Sanding machine

Abstract

This invention discloses a sander, comprising: a housing; a motor, at least partially disposed within the housing, for providing a power source, the motor shaft including a motor shaft rotating about a motor axis; a fan assembly including a fan connected to the motor; an eccentric element driven by the motor, the eccentric element having a central axis offset from the motor axis; a base plate assembly including a base plate, a grinding element fixed to the lower surface of the base plate, and a support member for supporting the eccentric element, the support member including a first end face and a second end face disposed opposite to each other, the second end face being disposed on the side closer to the lower surface relative to the first end face; the sander further includes a balance block connected to the eccentric element and driven by the motor to rotate about the central axis; the ratio of the distance from the center of mass of the balance block to the lower surface of the base plate to the distance from the first end face of the support member to the lower surface of the base plate is between 20% and 40%. This sander is lightweight and has a good operating feel.

Description

Technical Field

[0001] This invention relates to a power tool, specifically a sander. Background Technology

[0002] Sanders are becoming increasingly popular as a type of grinding and polishing tool. Functionally, they are mainly used for cleaning, deburring, and smoothing large flat surfaces such as those used in machinery, construction decoration, and furniture painting. Structurally, they typically include: a housing, a motor, a fan assembly, an eccentric element, and a base plate assembly. The housing houses the motor, fan assembly, and eccentric element. The base plate assembly, at least partially located outside the housing, is used to attach the sandpaper. The eccentric element drives the base plate assembly to move along the motor's axis, thereby achieving the grinding and polishing of the workpiece by the sandpaper. The fan assembly generates dust-collecting and heat-dissipating airflow when the motor is running.

[0003] To reduce vibration during operation, existing sanders on the market often incorporate a balancing structure to balance the base plate assembly. To facilitate installation and simplify the structure, this balancing structure is often directly fixed to or integrally formed with the eccentric element and / or fan assembly. However, this often results in a higher center of gravity for the balancing structure, increasing the distance between its center of gravity and the base plate assembly's center of gravity. This increases the torque between the centers of gravity, requiring additional counterweights to balance the torque and ensure stable machine operation. This increases the weight of the sander, affecting its handling. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a lightweight sander.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a sander, comprising: a housing; a motor, at least partially disposed within the housing, for providing a power source, the motor shaft including a motor shaft rotating about a motor axis; a fan assembly including a fan connected to the motor; an eccentric element driven by the motor, the eccentric element having a central axis offset from the motor axis; a base plate assembly including a base plate, a grinding element fixed to the lower surface of the base plate, and a support member for supporting the eccentric element, the support member including a first end face and a second end face disposed opposite to each other, the second end face being disposed on the side closer to the lower surface relative to the first end face; the sander further includes a balance block connected to the eccentric element and driven by the motor to rotate about the central axis; the ratio of the distance from the center of mass of the balance block to the lower surface of the base plate to the distance from the first end face of the support member to the lower surface of the base plate is between 20% and 40%.

[0006] Furthermore, the balance block includes a center of mass adjustment part for adjusting the center of mass of the balance block. The center of mass adjustment part is fixedly connected to the balance block or integrally formed.

[0007] Furthermore, the base plate assembly also includes a support seat for mounting the support member, the support seat being fixedly connected to the base plate, and the support seat including a clearance groove that allows the counterweight to rotate.

[0008] Furthermore, the base plate includes a groove that allows the balance block to move, and the balance block at least partially overlaps the base plate in its axial direction.

[0009] Furthermore, the groove is a circular groove coaxial with the central axis, and the ratio of the inner diameter of the groove to the outer diameter of the base plate is between 25% and 40%.

[0010] Furthermore, the balance weight includes a weight-adding part and a weight-reducing part. The weight-reducing part is located on the side of the balance weight facing the base plate, and the weight-adding part is located on the side of the balance weight facing the fan; or the weight-reducing part is located on the side of the balance weight facing the fan, and the weight-adding part is located on the side of the balance weight facing the base plate.

[0011] Furthermore, the product of the fan's weight and the square of the fan's outer diameter is greater than or equal to 40 kg / cm² and less than or equal to 200 kg / cm².

[0012] Furthermore, the ratio of fan weight to motor mass is greater than or equal to 3% and less than or equal to 25%.

[0013] A sander includes: a housing; a motor, at least partially disposed within the housing, for providing a power source, the motor shaft including a motor shaft rotating about a motor axis; a fan assembly including a fan connected to the motor; an eccentric element driven by the motor, the eccentric element having a central axis offset from the motor axis; a base plate assembly including a base plate, a grinding element fixed to a lower surface of the base plate, and a support member for supporting the eccentric element, the support member including a first end face and a second end face disposed opposite to each other, the second end face being disposed on a side closer to the lower surface relative to the first end face; the sander further includes a counterweight connected to the eccentric element and driven by the motor to rotate about a central axis; the ratio of the distance from the center of mass of the counterweight to the lower surface of the base plate to the distance from the first end face of the support member to the lower surface of the base plate is between 20% and 40%; the product of the weight of the fan and the square of the fan's outer diameter is greater than or equal to 40 kg / cm² and less than or equal to 200 kg / cm².

[0014] Furthermore, the fan is positioned above the counterweight in the direction along the motor axis, wherein the density of the fan is less than 6.5 g / cm3.

[0015] Furthermore, the base plate includes a groove that allows the balance block to move, and the balance block at least partially overlaps the base plate in its axial direction.

[0016] Furthermore, the groove is a circular groove coaxial with the central axis, and the ratio of the inner diameter of the groove to the outer diameter of the base plate is between 25% and 40%.

[0017] Furthermore, the ratio of fan weight to motor mass is greater than or equal to 3% and less than or equal to 25%.

[0018] Furthermore, the balance weight includes a weight-adding part and a weight-reducing part. The weight-reducing part is located on the side of the balance weight facing the base plate, and the weight-adding part is located on the side of the balance weight facing the fan; or the weight-reducing part is located on the side of the balance weight facing the fan, and the weight-adding part is located on the side of the balance weight facing the base plate.

[0019] The advantage of this invention is that by setting the center of mass of the balance block near the bottom surface of the base plate, the torque between the center of mass of the balance block and the center of mass of the base plate assembly is reduced, thereby reducing the weight of the balance block and the weight of the sander. Attached Figure Description

[0020] Figure 1 This is a perspective view of the sander shown in this invention;

[0021] Figure 2 for Figure 1 The diagram shows the structural plan of the power unit, fan unit, and base plate unit of the sander.

[0022] Figure 3 for Figure 2 The structure shown is a cross-sectional view along the motor axis;

[0023] Figure 4 for Figure 2 Exploded view of the structure shown;

[0024] Figure 5 for Figure 2 An exploded view of the structure shown from another perspective;

[0025] Figure 6 for Figure 4 A 3D view of the fan in the structure shown;

[0026] Figure 7 for Figure 4 A three-dimensional view of the fan in the structure shown from another perspective;

[0027] Figure 8 for Figure 4 A 3D view of the balance block in the structure shown;

[0028] Figure 9 for Figure 4 A three-dimensional view of the balance block in the structure shown from another perspective. Detailed Implementation

[0029] Figure 1The image shows a sander 100, which can drive the movement of a functional element, which can be sandpaper. In this way, the sander 100 can perform sanding, polishing, and other functions on the surface of workpieces made of various materials through the functional element.

[0030] It is understandable that the sander 100 can specifically be used for round sanders, triangular sanders, square sanders, etc. For the sake of convenience in describing the technical solution, this application specifically uses round sanders as an example.

[0031] For ease of explanation, the definition is as follows: Figure 1 The directions shown are up, down, front, back, left, and right.

[0032] like Figures 1 to 5 As shown, the sander 100 includes: a housing 10, a switch 111, a base plate assembly 40, a power assembly 20, a fan assembly 30, an eccentric element 50, and an energy source (not shown in the figure).

[0033] The housing 10, which forms the outer shape of the sander 100, includes at least a handle 110, a receiving portion 120, and a support portion 130. The handle 110 is for the user to grip; one end of the handle 110 is connected to the receiving portion 120, and the other end can be used to connect an external power cable or form a connector for mounting a portable DC power supply such as a battery pack. The receiving portion 120 is located between the handle 110 and the support portion 130, and a receiving cavity is formed inside the receiving portion 120, within which the power assembly 20 is at least partially disposed. The support portion 130 covers the fan assembly 30 and at least a portion of the base plate assembly 40.

[0034] The switch 111 can be installed on the housing 10. Specifically, the switch 111 is installed on the handle 110. This design allows the user to easily trigger the switch 111 when holding the handle 110.

[0035] The power assembly 20 includes a motor 21, which serves as the prime mover of the sander 100 and is housed within the casing 10. The motor 21 includes a motor shaft 211 for transmitting power to the fan assembly 30, and the motor shaft 211 rotates about a motor axis 101. The motor axis 101 extends substantially in the vertical direction.

[0036] The fan assembly 30 includes a fan 31, which can be driven by a motor shaft 211 to rotate about a motor axis 101. When the fan 31 is driven by the motor shaft 211 to rotate, the fan 31 can generate airflow.

[0037] An eccentric element 50 surrounds the motor shaft 211 and is eccentrically positioned relative to the motor shaft 211. The eccentric element 50 is mounted on and fixedly connected to the motor shaft 211. It should be noted that the eccentric positioning of the eccentric element 50 relative to the motor shaft 211 means that the eccentric element 50 has a central axis 102, which is parallel to the motor shaft axis 101 of the motor shaft 211, and there is a distance D between them. The existence of distance D allows the eccentric element 50 to transmit the rotation of the motor shaft 211 into the rotation and revolution of other components connected to the eccentric element 50 when the motor shaft 211 rotates.

[0038] The motor shaft 211 drives the base plate assembly 40, enabling the base plate assembly 40 to swing relative to the housing 10. Specifically, the base plate assembly 40 is fixedly connected to the eccentric element 50, meaning that the motor shaft 211 transmits power to the base plate assembly 40 through the eccentric element 50. The base plate assembly 40 includes a base plate 41, which includes an upper surface 411 and a lower surface 412 disposed opposite to each other. The lower surface 412 is disposed on the side away from the eccentric element 50 relative to the upper surface 411, and is used to mount functional components such as sandpaper. Driven by the motor shaft 211 and the eccentric element 50, the base plate 41 can perform eccentric motion. When the base plate 41 performs eccentric motion, the sandpaper can continuously rub against the surface of the workpiece to be ground, thereby achieving functions such as grinding and polishing of the workpiece.

[0039] The energy source provides power to the sander 100. The energy source can be alternating current (AC) or direct current (DC), such as a portable power source like a battery pack. In this embodiment, alternating current (AC) is used as the energy source.

[0040] like Figures 4 to 5 As shown, the base plate assembly 40 also includes a support member 42 and a support seat 43. The support member 42 is used to reduce the coefficient of friction between the motor shaft 211 and the eccentric element 50 disposed on the motor shaft 211 during rotation, ensuring the rotational accuracy and parallelism of the motor shaft 211. The support member 42 is sleeved on the eccentric element 50 and fixedly connected to the eccentric element 50. Specifically, the support member 42 is a rolling bearing, which includes an outer ring, an inner ring, and balls. The inner ring is sleeved on the motor shaft 211 and fixedly connected to the motor shaft 211. The outer ring is fixedly connected to the support seat 43 and surrounds the inner ring. The balls are disposed between the outer ring and the inner ring to allow the outer ring to move relative to the inner ring.

[0041] The support base 43 is used to mount the support member 42. The support base 43 is fixedly connected to the outer ring of the support member 42, that is, the outer ring of the support member 42 and the support base 43 are synchronously connected. The support base 43 is fixedly connected to the base plate 41, that is, the base plate 41 can move synchronously with the support base 43 and the outer ring of the support member 42.

[0042] like Figure 4 , Figure 5 , Figure 8 and Figure 9 As shown, the sander 100 also includes a balancing assembly 60 for balancing the base plate assembly 40. The balancing assembly 60 includes a balancing block 61, which is located between the fan 31 and the base plate 41 along the motor axis 101. The balancing block 61 and the eccentric element 50 are detachably fixedly connected, meaning that the eccentric element 50 and the balancing block 61 move synchronously, and the balancing block 61 can rotate around the central axis 102 with the eccentric element 50. It should be noted that the detachable fixed connection between the balancing block 61 and the eccentric element 50 means that the balancing block 61 and the eccentric element 50 are two separable parts, which can be fixed together by screws, threads, or snap-fit ​​connections to enable synchronous rotation. In this application, the balance block 61 and the eccentric element 50 are connected by screws. Specifically, the balance assembly 60 includes at least one fixing member, which is a positioning screw. The positioning screw passes through the connecting hole on the balance block 61, causing the balance block 61 to abut against the inner ring of the support member 42, and finally locking the balance block 61 onto the eccentric element 50, thereby achieving synchronous rotation of the balance block 61 and the eccentric element 50. Alternatively, the fixing member can be understood as the fixing member entering the connecting hole of the balance block 61 from the side of the balance block 61 near the base plate 41, thus fixing it to the eccentric element 50, thus constituting synchronous rotation. By using the balance block 61 to support the inner ring of the support member 42, it is possible to prevent the inner ring of the support member 42 from detaching from the outer ring of the support member 42 during operation of the sander 100, simplifying the structure and making the overall machine structure more compact.

[0043] In this embodiment, the support member 42 also includes a first end face 421 and a second end face 422 disposed opposite to each other, with the second end face 422 disposed on the side near the lower surface 412 of the base plate 41 relative to the first end face 421. That is, in the direction along the motor axis 101, the first end face 421 is disposed above the second end face 422. The distance from the center of mass A of the balance block 61 to the lower surface 412 of the base plate 41 is between 20% and 40% of the distance from the first end face 421 of the support member 42 to the lower surface 412 of the base plate 41. The center of mass A of the balance block 61 is disposed adjacent to the base plate 41. By setting the position of the center of mass A of the balance block 61 within the above-mentioned range, the center of mass A of the balance block 61 is positioned close to the center of mass B of the base plate assembly 40. This reduces the distance between the center of mass A of the balance block 61 and the center of mass B of the base plate assembly 40, thereby significantly reducing the weight of the balance block 61 and consequently reducing the overall weight of the sander 100.

[0044] Furthermore, such as Figure 3As shown, the center of mass A of the balance block 61 is located between the base plate 41 and the support member 42. The distance D1 from the center of mass A of the balance block 61 to the center of mass B of the base plate assembly 40 along the motor axis 101 is greater than or equal to 0 mm and less than or equal to 2 mm. The balance block 61 is used to achieve both mass and torque balance of the base plate assembly 40. By arranging the balance block 61 so that its center of mass A is close to the center of mass B of the base plate assembly 40, the distance between the center of mass A of the balance block 61 and the center of mass B of the base plate assembly 40 is reduced, thus reducing the torque between them. In other words, the weight used to balance the torque is reduced. This can also be understood as eliminating the need for other weight blocks to balance the torque, thus avoiding the need to add weight to the balance block 61 to balance other weight blocks. Alternatively, simply adding other very light weight blocks can offset the torque. This requires only adding an extra weight block of the same weight as the others to the balance block 61. Therefore, by setting it up as described above, the weight of the balance block 61 can be significantly reduced, thereby reducing the weight of the sander 100, making it easier for the user to operate, reducing the overall weight of the machine, and decreasing user fatigue. Furthermore, the distance D1 from the center of mass A of the balance block 61 to the center of mass B of the base plate assembly 40 is greater than or equal to 0 mm and less than or equal to 1 mm; within this range, the effect is even better.

[0045] The balance block 61 also includes a center of gravity adjustment part 62, which is fixedly connected to or integrally formed with the balance block 61. In this embodiment, the center of gravity adjustment part 62 is integrally formed with the balance block 61. Specifically, the center of gravity adjustment part 62 includes a weight-increasing part and a weight-reducing part. The weight-increasing part is used to increase the weight of the balance block 61, and the weight-reducing part is used to reduce the weight of the balance block 61. The weight-reducing part is located on the side of the balance block 61 facing the base plate 41, and the weight-increasing part is located on the side of the balance block 61 facing the fan 31. Of course, as another embodiment, the weight-reducing part is located on the side of the balance block 61 facing the fan 31, and the weight-increasing part is located on the side of the balance block 61 facing the base plate 41. The above configuration, that is, setting a center of gravity adjustment part 62 on the balance block 61, allows for adjustments to the weight-increasing part and the weight-reducing part according to the weight, eccentricity, etc. of the base plate assembly 40, thereby adjusting the position of the center of gravity and achieving a balance between the weight and torque of the base plate assembly 40. For example, a center of gravity adjustment part 62 that extends upward to increase the weight of the balance block 61 can be provided, or a center of gravity adjustment part 62 that extends downward to reduce the weight of the balance block 61 can be provided.

[0046] like Figures 3 to 5As shown, the balance block 61 is located between the support base 43 and the base plate 41, and the balance block 61 is at least partially disposed within the base plate 41. The balance block 61 includes a first surface 611 and a second surface 612 disposed opposite to each other. The first surface 611 is disposed away from the base plate 41 relative to the second surface 612, and the second surface 612 is located below the fixing member in the direction along the motor axis 101. That is, the first surface 611 at least partially abuts against the inner ring of the support member 42, and the second surface 612 is disposed adjacent to the upper surface 411 of the base plate 41. The upper surface 411 of the base plate 41 is recessed downward to form a groove 413 for the balance block 61 to move. The second surface 612 of the balance block 61 extends toward the recess of the groove 413. In other words, the balance block 61 and the base plate 41 partially overlap in their axial direction. In this embodiment, the groove 413 is a circular groove coaxial with the central axis 102, and the ratio of the inner diameter of the groove 413 to the outer diameter of the base plate 41 is between 25% and 40%. Furthermore, the radius C of the groove 413 is greater than or equal to 16 mm and less than or equal to 50 mm. On the one hand, by setting the radius C of the groove 413 within the above-mentioned reasonable range, it is possible to ensure that the balance block 61 has sufficient room for movement, while avoiding the situation where the radius of the groove 413 is too large, which would increase the radial dimension of the transmission component. On the other hand, by setting the downwardly recessed groove 413 on the base plate 41, the balance block 61 is positioned as close as possible to the base plate 41, thereby bringing the center of mass A of the balance block 61 closer to the base plate 41. This reduces the torque and also shortens the overall vertical dimension of the machine, thus making the overall structure more compact and reducing the weight of the machine.

[0047] The balance block 61 is at least partially disposed within the support base 43, which has a clearance groove 431 and a receiving groove 432. In the radial direction perpendicular to the motor axis 101, the clearance groove 431 is located outside the receiving groove 432. Both the clearance groove 431 and the receiving groove 432 are formed by an upward recess from the end face of the support base 43 near the upper surface 411 of the base plate 41. The receiving groove 432 is used to receive the support member 42, wherein the wall surface of the receiving groove 432 is at least partially in contact with the outer ring of the support member 42. The clearance groove 431 and the support member 42 partially overlap axially. The clearance groove 431 allows the balance block 61 to move, and the radius E of the clearance groove 431 is greater than or equal to 20 mm. This arrangement ensures sufficient movement space for the balance block 61 while making the overall structure more compact in the vertical direction, thus providing the user with a small and lightweight sander 100.

[0048] The second surface 612 and the first surface 611 are used to fix the eccentric element 50 to the fan 31 or form it integrally. In this embodiment, the eccentric element 50 is integrally formed with the fan 31, that is, the eccentric element 50 is formed on the fan 31. The fan 31 is mounted on the motor shaft 211 and can be driven by the motor shaft 211 to rotate. Of course, it can also be said that the fan 31 is the eccentric element 50.

[0049] Furthermore, the ratio of the weight of the fan 31 to the weight of the motor 21 is greater than or equal to 3% and less than or equal to 25%. With a fixed weight of the motor 21, the smaller the proportion of the fan 31 to the motor 21's weight, the lighter the fan 31 is, meaning a smaller moment of inertia is generated when the fan 31 rotates, which greatly improves the user's handling experience. On the other hand, a lighter fan 31 reduces the overall weight of the sander 100, making it easier for the user to hold.

[0050] In this embodiment, the fan 31 is made of a material with a density of less than 6.5 g / cm³. Since weight is directly proportional to density, the lower the density, the lighter the fan 31, effectively reducing its weight and thus the weight of the sander 100. Preferably, when the fan 31 is made of a material with a density greater than or equal to 1 g / cm³ and less than or equal to 3 g / cm³, the structural strength requirement is met while also reducing the weight of the fan 31. Furthermore, the fan 31 can be made of aluminum, which reduces its weight and saves costs. When the sander 100... Figure 1 When the motor 21 drives the fan 31 to rotate, the fan 31 generates rotational inertia. This means that the rotation of the fan 31 creates a constraint force that keeps it rotating around the motor axis 101 (vertically). This constraint force will restrain the sander 100 from continuing to rotate in the vertical direction if it tends to move in a direction intersecting the vertical direction. In other words, when the user applies a force to the sander 100 to move it in a direction intersecting the vertical direction, the constraint force will cause the sander 100 to tend to move in the opposite direction. This requires the user to apply more force to overcome the constraint force, resulting in inconvenience and fatigue over time, affecting work efficiency. The rotational inertia is proportional to the weight; the greater the weight of the fan 31, the greater the rotational inertia and the greater the impact on the user. Therefore, the above settings can reduce the rotational inertia, thereby improving the user experience.

[0051] Furthermore, the ratio of the product of the fan 31's weight and the square of its outer diameter is greater than or equal to 40 kg / cm² and less than or equal to 200 kg / cm². Here, the outer diameter refers to the radius of the outer edge of the fan 31. By setting the ratio of the fan 31's weight to the square of its outer diameter within the above range, the rotational inertia generated by the fan 31 during rotation can be effectively reduced, minimizing the influence of constraint forces during user operation and thus improving work efficiency.

[0052] Furthermore, the total weight of the fan 31 and the motor 21 is less than or equal to 400g. Within the internal structure of the sander 100, the motor 21 and fan 31 are relatively heavy compared to other components; that is, the weight of the sander 100 is mainly concentrated in the motor 21 and fan 31. By adjusting the structure and position of the balancing assembly 60 and the fan assembly 30, the weight of the fan 31 is significantly reduced, resulting in a sander 100 with a smaller moment of inertia and lighter weight. In this embodiment, the weight of the fan 31 is less than or equal to 80g.

[0053] like Figure 1 As shown, the housing 10 has an air inlet, an air outlet, and a dust outlet. The fan 31 is fixedly connected to the motor shaft 211; that is, when the motor 21 rotates, the fan 31 operates accordingly. When the fan 31 rotates, airflow enters through the air inlet, flows through the motor 21 and other components, and finally flows out through the air outlet, thereby achieving the effect of cooling the motor 21 and other components inside the housing 10. On the other hand, the airflow can also effectively blow dust and debris on the base plate 41 to the dust outlet, ultimately entering the dust collection box (not shown in the figure), thus achieving the effect of dust collection.

[0054] like Figures 6 to 7As shown, the fan 31 also includes a bracket 311, an air guide section 312, and a dust collection section 313. The bracket 311 is generally ring-shaped and includes an upper surface 321, a lower surface 331, and a through hole 341 arranged opposite each other. The upper surface 321 is located on the side away from the base plate 41 relative to the lower surface 331. The bracket 311 is fixedly connected to the motor shaft 211, that is, the through hole 341 of the bracket 311 is fitted onto the outer ring of the motor shaft 211. Of course, an intermediate part can also be provided between the through hole 341 of the bracket 311 and the outer ring of the motor shaft 211. The specific connection method between the through hole 341 of the bracket 311 and the outer ring of the motor shaft 211 is not limited here, as long as synchronous rotation can be achieved. The fan 31 includes at least two air guide sections 312, which are distributed on the upper surface 321 of the bracket 311. The air guide sections 312 are integrally formed with the bracket 311, but they can also be formed separately. The bracket 311 is annular, meaning it is arranged symmetrically along the motor axis 101. Air guides 312 are evenly distributed on the upper surface 321 of the bracket 311 along the circumference of the motor axis 101, extending upwards along the motor axis 101. In this embodiment, the air guide 312 is specifically an arc-shaped heat-dissipating blade. The number of heat-dissipating blades on the fan 31 is greater than or equal to 20, increasing the airflow generated when the fan 31 rotates, thus improving its heat-dissipating effect. Furthermore, the arc length of the heat-dissipating blades is greater than 13mm, further increasing the airflow when the fan 31 rotates, thereby improving its heat-dissipating effect. The fan 31 includes at least two dust-collecting parts 313, distributed on the lower surface 331 of the bracket 311, meaning the dust-collecting parts 313 and the air guides 312 are arranged opposite each other on both sides of the bracket 311, with the dust-collecting parts 313 adjacent to the base plate 41. The suction unit 313 is integrally formed with the bracket 311, but they can also be formed separately. The suction units 313 are evenly distributed on the lower surface 331 of the bracket 311 along the circumferential direction of the motor axis 101, and extend downward along the direction of the motor axis 101. In this embodiment, the suction unit 313 is specifically an arc-shaped suction blade.

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A sander comprising: a housing; a motor disposed at least partially within the housing for providing a source of power, the motor shaft comprising a motor shaft rotating about a motor axis; a fan assembly comprising a fan connected to the motor; an eccentric element driven by the motor, the eccentric element having a central axis disposed offset from the motor axis; a base plate assembly comprising a base plate, an abrasive element fixed to a lower surface of the base plate, and a support element for supporting the eccentric element, the support element comprising first and second oppositely disposed end faces, the second end face disposed closer to the lower surface than the first end face; characterized in that: the sander further comprises a counterweight connected to the eccentric element and driven by the motor to rotate about the central axis; a ratio of a distance of a center of mass of the counterweight from the lower surface of the base plate to a distance of the first end face of the support element from the lower surface of the base plate is between 20% and 40%.

2. The sander of claim 1, characterized in that: the counterweight comprises a center of mass adjustment portion for adjusting the center of mass of the counterweight, the center of mass adjustment portion fixedly connected to or integrally formed with the counterweight.

3. The sander of claim 2, characterized in that: the base plate assembly further comprises a support seat for mounting the support element, the support seat fixedly connected to the base plate, the support seat comprising a relief slot for allowing rotation of the counterweight.

4. The sander of claim 2, characterized in that: the base plate comprises a recess for allowing movement of the counterweight, the counterweight at least partially overlapping the base plate in an axial direction thereof.

5. The sander of claim 4, characterized in that: the recess is a circular recess coaxial with the central axis, an inner diameter of the recess to an outer diameter of the base plate is between 25% and 40%.

6. The sander of claim 1, characterized in that: the counterweight comprises a weight increasing portion and a weight decreasing portion, the weight decreasing portion disposed on a side of the counterweight facing the base plate, the weight increasing portion disposed on a side of the counterweight facing the fan; or the weight decreasing portion disposed on a side of the counterweight facing the fan, the weight increasing portion disposed on a side of the counterweight facing the base plate.

7. The sander of claim 4, characterized in that: a product of a weight of the fan and a square of an outer diameter of the fan is greater than or equal to 40 kg / cm2 and less than or equal to 200 kg / cm2.

8. The sander of claim 1, characterized in that: a ratio of the weight of the fan to a mass of the motor is greater than or equal to 3% and less than or equal to 25%.

9. The sander of claim 1, characterized in that: a product of a weight of the fan and a square of an outer diameter of the fan is greater than or equal to 40 kg / cm2 and less than or equal to 200 kg / cm2.

10. The sander of claim 9, characterized in that: the fan is located on an upper side of the counterweight in a direction along the motor axis, wherein a density of the fan is less than 6.5 g / cm3.

11. The sander of claim 9, wherein: the bottom plate includes a recess allowing the movement of the counterweight, the counterweight at least partially overlapping the bottom plate in its axial direction, the recess being a circular recess coaxial with the central axis, the ratio of the inner diameter of the recess to the outer diameter of the bottom plate being between 25% and 40%.

12. The sander of claim 9, wherein: the ratio of the weight of the fan to the mass of the motor is greater than or equal to 3% and less than or equal to 25%.

13. The sander of claim 9, wherein: the counterweight includes a weight-increasing portion and a weight-reducing portion, the weight-reducing portion being disposed on the side of the counterweight facing the bottom plate, the weight-increasing portion being disposed on the side of the counterweight facing the fan; or the weight-reducing portion being disposed on the side of the counterweight facing the fan, the weight-increasing portion being disposed on the side of the counterweight facing the bottom plate. ​

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