Grinding tool

Abstract

A grinding tool includes: a motor having a rotating shaft; a motor housing that accommodates the motor; a main shaft driven by the motor and extending in a direction intersecting the rotation shaft; a gear transmission mechanism that transmits rotation of a rotating shaft of the motor to the main shaft; the end tool is mounted on the main shaft; and a gearbox mounted in front of the motor housing and for receiving the gear transmission mechanism, the gear housing being formed from a metal insert overmolded with a plastic material. The gear housing of the grinding tool has reduced weight and good heat dissipation.

Description

Technical Field

[0001] This invention relates to a grinding tool, and more particularly to a grinding tool for grinding workpiece materials, which grinds the workpiece by rotating an end tool. Background Technology

[0002] For large handheld grinding tools such as heavy-duty angle grinders, weight is a key consideration for providing a good ergonomic experience for the user. Currently, the gear housings of such grinding tools are typically made of die-cast metal (such as aluminum alloy) to ensure sufficient strength. However, as the size of the grinding tool or the moving grinding wheel increases, the weight increases, leading to increased load on the user's hands and arms, and thus fatigue. Additionally, gear housings made of metal have high thermal conductivity and therefore transfer heat very easily, which can cause discomfort to the user's hands. Furthermore, the manufacturing cost of grinding tools remains high due to the continuous rise in the price of metal raw materials. Summary of the Invention

[0003] The purpose of this invention is to provide a grinding tool whose gear housing has reduced weight and good heat dissipation.

[0004] This invention provides a grinding tool comprising a motor having a rotating shaft and a motor housing housing the motor. A spindle is driven by the motor and extends in a direction intersecting the rotating shaft. A gear transmission mechanism transmits the rotation of the motor's rotating shaft to the spindle. An end tool is mounted on the spindle, and a gearbox is mounted in front of the motor housing and serves to receive the gear transmission mechanism. The gearbox is formed from a metal insert molded and covered with plastic material. According to this invention, the gearbox, conventionally made of metal, is now formed from a metal insert molded and covered with plastic, thus reducing the weight of the grinding tool and the load on the user's hands and arms, thereby reducing fatigue when operating the grinding tool. Furthermore, when the user's hand touches the gearbox cover, the contact area is made of a plastic or composite material with low thermal conductivity, so the temperature change of the gearbox cover is very small, and it will not cause accidental burns to the user when operating the grinding tool.

[0005] According to an embodiment of the present invention, the gear transmission mechanism includes a driving gear connected to a rotating shaft and at least one driven gear meshing with the driving gear. The driving gear is supported in a gear housing by a first bearing. A main shaft passes through the center of the driven gear and is supported in the gear housing by at least one second bearing. The metal insert includes a first bearing housing for supporting the first bearing and a second bearing housing for supporting the second bearing. The metal insert forms the main functional parts of the gear housing, such as the bearing housing supporting the bearing. These functional parts typically require high machining accuracy and good thermal conductivity. The metal insert forming the bearing housing supporting the bearing ensures high dimensional accuracy and good thermal conductivity of the interface components; for other non-interface parts, the molded metal insert is covered with plastic or composite material, thus eliminating the need for subsequent processes of assembling the plastic parts to the metal insert. Therefore, cumbersome process steps are reduced, and sufficient strength is achieved.

[0006] The metal insert further includes an annular portion circumferentially surrounding the driven gear. In grinding tools, the motor shaft acts as the driving element, driving the drive gear to rotate at high speed; the drive gear meshes with the driven gear, causing the driven gear to rotate about the spindle center. Therefore, a certain clearance must exist between the circumferential surface of the driven gear and the gear housing, and simultaneously, the driven gear must be protected from accidental damage. Furthermore, heat is generated during the meshing and rotation of the drive and driven gears, as well as the bearings. Therefore, the annular portion of the metal insert effectively ensures dimensional accuracy between the housing and the driven gear, and provides the gear housing with sufficient rigidity and good heat dissipation.

[0007] The first bearing housing is arranged in the axial direction of the rotating shaft, and the front end of the first bearing housing is connected to the outer peripheral surface of the annular portion. In this way, the metal insert essentially covers the parts of the driving and driven gears in the gear transmission mechanism that require the most machining accuracy and heat dissipation, while the other parts are molded and overlaid with plastic or composite materials, thereby ensuring the functionality of the gear housing while reducing the weight of the housing.

[0008] The upper edge of the annular portion is provided with ribs extending toward the second bearing housing.

[0009] The gear transmission mechanism further includes a flange cover disposed below the driven gear and connected to the bottom of the gear housing. The flange cover is substantially cylindrical and has a hollow cavity. The driven gear is pre-assembled onto the top of the flange cover. The main bearing is mounted in the cavity, and the upper portion of the flange cover at least partially contacts the annular portion. In this invention, the spindle of the grinding tool is actually supported by a second bearing disposed at the upper end of the spindle and a main bearing disposed below the driven gear. The second bearing is securely mounted in the gear housing, the main bearing is securely mounted in the flange cover, and the flange cover is connected to the bottom of the gear housing, thereby ensuring the coaxiality of the second bearing and the main bearing to ensure that the spindle does not deviate from its central axis during operation. Furthermore, the flange cover at least partially contacts the lower edge of the annular portion, so that heat generated during operation of the gear transmission mechanism can be transferred from the interior of the gear housing to the exterior.

[0010] The outer peripheral surface of the flange cover is provided with cooling fins at least partially. The cooling fins can be arranged on the side closer to the motor housing. The side closer to the motor housing is located near the outlet of the cooling airflow for the grinding tool, so the cooling fins can be partially or completely exposed to the cooling airflow to maximize the cooling function.

[0011] The metal insert is formed integrally. In this way, the metal insert can be directly placed into the injection mold for overmolding; this simplifies and simplifies the gear housing formation process. The injection-molded part is usable immediately after leaving the mold and can be further processed to form the final product. Furthermore, compared to lightweight alloy gear housings, the combination of the metal insert and the overmolded plastic reduces manufacturing costs.

[0012] According to another embodiment of the invention, the gear housing further includes at least one threaded seat; the threaded seat is also made of metal and is molded together with a plastic overlay and metal insert. In addition to serving as an interface with the gear transmission mechanism, the gear housing also includes an interface for connecting external components (e.g., side handles, auxiliary handles, etc.). This interface is typically a threaded seat, and the external components can be easily and reliably connected to the gear housing via a threaded connection. These threaded seats should also be pre-formed from metal, placed in an injection mold together with the metal insert, and then molded with a plastic overlay.

[0013] Threaded seats are located on the top and / or left and right sides of the gear housing and are used to connect the side handle. Therefore, the side handle can be installed in the desired position according to the user's preference and application scenario. Attached Figure Description

[0014] The above embodiments can be better understood through the following detailed description with reference to the accompanying drawings. It should be emphasized that the components are not necessarily drawn to scale. In fact, dimensions can be increased or decreased arbitrarily for clarity. In the drawings, the same reference numerals denote the same elements.

[0015] Figure 1 This is a partial cross-sectional view of the grinding tool of the present invention;

[0016] Figure 2 This is a schematic diagram of the gear housing of the grinding tool of the present invention;

[0017] Figure 3 This is a schematic diagram of the metal insert and threaded seat of the gear housing of the grinding tool of the present invention;

[0018] Figure 4 This is a schematic diagram of the gear transmission mechanism and spindle of the grinding tool of the present invention;

[0019] Figure 5 yes Figure 4 The gear transmission mechanism and spindle shown are viewed from below when they are installed in the gear housing. Detailed Implementation

[0020] The following is for reference. Figures 1 to 5 This invention describes a grinding tool. The following description is merely exemplary and does not limit the disclosure of this application or the application or use of the invention. The terms "front," "rear," "above," "below," "left," and "right" throughout this specification are used to define the grinding tool when it is arranged in the orientation in which it is intended to be used (e.g., ...). Figure 1 The components (as shown in the orientation) are arranged in a specific way.

[0021] Figure 1 A partial cross-sectional view of the front end of the grinding tool 1 is shown. The grinding tool 1 includes: a motor 3 having a rotating shaft 2; a motor housing 4 for housing the motor 3; a spindle 5 driven by the motor 3 and extending in a direction intersecting the rotating shaft 2; a gear transmission mechanism 6 that transmits the rotation of the rotating shaft 2 of the motor 3 to the spindle 5; an end tool (not shown) mounted on the spindle 5; and a gear housing 7 mounted in front of the motor housing 4 and for receiving the gear transmission mechanism 6 and the spindle 5. The rotating shaft 2 of the motor 3 extends substantially in the front-rear direction of the grinding tool 1, and when the motor 3 is activated, the rotating shaft 2 is driven to rotate at high speed about its axial extension direction.

[0022] The gear transmission mechanism 6 includes: a driving gear 60, which is directly or indirectly connected to the rotating shaft 2; at least one driven gear 64, which meshes with the driving gear; and a flange cover 65, which is disposed below the driven gear 64 and connected to the bottom of the gear housing.

[0023] According to an embodiment of the present invention, the driving gear 60 is a beveled pinion extending in the axial direction of the rotating shaft 2, and the driving gear 60 is press-fitted around the front end of the rotating shaft 2 with an interference fit. The driven gear 64 is arranged perpendicular to the axial direction of the rotating shaft 2, that is, the central axis of the driven gear extends in the vertical direction. The top surface of the driven gear 64 has a helical tooth portion that meshes with the bevel teeth of the driving gear 60. The driven gear may be a bevel gear. The main shaft 5 passes through the center of the driven gear, and there is an interference fit between the main shaft 5 and the driven gear 64. Furthermore, the upper end of the main shaft 5 is supported in the gear housing 7 by a second bearing 62.

[0024] The flange cover 65 is generally cylindrical and has a hollow cavity 67. The driven gear 64 is pre-assembled onto the top of the flange cover 65, and the main bearing 63 is mounted in the hollow cavity 67. The main shaft 5 is supported by a second bearing 62 located at the upper end of the main shaft and a main bearing 63 coaxial with the second bearing and located below the driven gear. The second bearing 62 is securely mounted in the gear housing, the main bearing 63 is securely mounted in the flange cover, and the flange cover 65 is securely connected to the gear housing 7, such that one end of the main shaft 5 is supported by the second bearing 62 and the other end of the main shaft 5 is supported by the main bearing 63, ensuring that the main shaft 5 does not deviate from its center of rotation during operation. Thus, the gear transmission mechanism 6 converts the high-speed rotational drive of the motor shaft 2 in the longitudinal direction into a low-speed rotational output of the main shaft 5 in the vertical direction. In alternative embodiments, other angular transmission devices 33, such as worm gear drives or spur gear drives, are also considered.

[0025] Figure 2A gear housing 7 according to one embodiment of the present invention is shown. The gear housing 7 of the present invention has substantially the same shape as a conventional metal housing, except that the gear housing 7 of the present invention is formed by a metal insert 70 and a plastic portion 75 molded over the metal insert 70. The grinding tool of the present invention achieves significant weight reduction by using as much plastic or any composite material as possible instead of metal. Especially for large grinding tools, the potential for weight reduction of the gear housing is in the range of about 50%, or between 150 g and 250 g, which is very significant for tools with a total weight of 5 kg to 7 kg. Furthermore, when the user touches the upper part of the gear housing with their palm, the part in contact with the palm is made of plastic with low thermal conductivity, so the external temperature of the gear housing changes very little during operation, and the user will not be burned or feel uncomfortable due to accidentally touching an excessively hot gear housing; therefore, the grinding tool is safer to operate. In addition, the resin material of the gear cover allows for reduced production costs compared to lightweight alloy gear covers.

[0026] See Figure 2 and Figure 3 The metal insert 70 is a one-piece finished part. Preferably, the metal insert is made of a light alloy material such as aluminum alloy or magnesium alloy to ensure sufficient strength and relatively light weight. The one-piece metal insert 70 can be directly placed into an injection mold, and then plastic or composite material is injected for overmolding; this makes the gear housing forming process simple and convenient. The injection-molded part is usable immediately after leaving the mold and can also be further processed to form the final product. By using the molding process of overmolding the insert by injection, the present invention omits the process step of assembling the metal and plastic parts together, thereby greatly increasing the convenience of gear housing manufacturing. In addition, the plastic used for overmolding the metal insert can be selected to have different colors and properties to give the product more characteristics regarding color and eliminate downstream processes such as coloring or coating.

[0027] According to an embodiment of the present invention, the metal insert 70 includes a first bearing seat 71 for supporting a first bearing 61, a second bearing seat 72 for supporting a second bearing 62, and an annular portion 74 circumferentially surrounding the driven gear 64. The first bearing seat 71 extends in the axial direction of the rotating shaft, and its front end is connected to the outer peripheral surface of the annular portion 74. Preferably, the upper edge of the annular portion 74 is provided with a rib 73 extending toward the second bearing seat 72. The outer peripheral surface of the annular portion may also be provided with screw fixing holes 76 for fastener engagement with the flange cover 65.

[0028] The metal insert 70 forms the main functional parts of the gear housing 7, such as the bearing housing supporting the bearing, because these functional parts typically require high machining accuracy and good thermal conductivity. The metal insert 70 forms the main functional parts of the gear housing 7 to ensure sufficient rigidity, high dimensional accuracy, and good thermal conductivity for the components that act as interfaces with the gear transmission mechanism 6. For other non-interface parts, the molded metal insert is overlaid with plastic or composite materials to reduce the weight of the gear housing 7.

[0029] In the grinding tool 1, the gear transmission mechanism 6 converts the high-speed rotational drive of the motor into the rotational output of the spindle 5, thereby driving the end tool to rotate to perform the grinding operation. A certain clearance must exist between the circumferential surface of the driven gear 64 and the internal cavity of the gear housing, and at the same time, the driven gear must be protected from accidental damage; therefore, as the component of the gear housing 7 that serves as the interface with the circumferential surface of the driven gear, the annular portion 74 of the metal insert of the present invention ensures the dimensional accuracy between the gear housing and the driven gear 64, and provides the gear housing 7 with sufficient rigidity.

[0030] like Figure 1 As shown, the front end of the driving gear 60 is a beveled tooth portion, and the rear end of the driving gear 60 is assembled around the front end of the rotating shaft 2 with an interference fit or a form fit. The first bearing 61 is assembled around the shaft behind the beveled tooth portion of the driving gear 60. The first bearing 61 is installed in the first bearing housing 71 with an interference fit to ensure that the driving gear 60 will not deviate from its rotation center when driven to rotate by the rotating shaft, and can apply sufficient driving torque to the driven gear to achieve gear transmission.

[0031] The first bearing housing 71 extends in the axial direction of the rotating shaft 2, and its front end engages with the outer peripheral surface of the annular portion 74. In this way, the metal insert 70 substantially covers the parts of the driving and driven gears in the gear transmission mechanism that require the most machining accuracy and heat dissipation, while other parts are molded and overmolded with plastic or composite materials, thereby ensuring the functionality of the gear housing while reducing the weight of the housing.

[0032] As described above, there is an interference fit between the main shaft 5 and the driven gear 64, and the main shaft 5 is supported by a second bearing 62 and a main bearing 63 arranged coaxially. The second bearing 62, located at the upper end of the main shaft 5, is securely mounted in the second bearing seat 72 of the gear housing 7. The main bearing 63 is located below the driven gear 64; see reference. Figure 1 and Figure 4 When the flange cap 65 is connected to the gear housing 7 through the screw fixing hole 76 in the metal insert 70, the main bearing 63 and the second bearing 62 are coaxial. The second bearing housing 72 is made of metal and has sufficiently high dimensional accuracy to ensure the coaxiality of the second bearing 62 and the main bearing 63.

[0033] The upper edge of the annular portion 74 is provided with ribs 73 extending toward the second bearing housing 72; preferably, the ribs 73 are connected to the outer peripheral surface of the second bearing housing 72 to further increase the rigidity of the gear housing. The ribs 73 are evenly arranged at the upper edge of the annular portion 74 in the circumferential direction, but must avoid the position of the drive gear.

[0034] See Figures 1 to 5 The annular portion 74 has screw fixing holes 76 around its periphery, and the flange cover 65 also has a radially outwardly extending mounting portion 68 around its periphery. The mounting portion 68 has mounting holes 69, and fasteners are inserted into the mounting holes 69 and threaded holes 67 of the metal insert to connect the flange cover 65 to the bottom of the gear housing 7. At this time, the upper portion of the flange cover 65 is at least partially in contact with the annular portion 64, so that heat can be conducted from the inside and the plastic-covered metal insert to the outside. Preferably, the upper portion of the flange cover extends into the inner circumferential side of the annular portion, thereby fitting against the lower circumferential edge of the annular portion in the circumferential direction for better heat dissipation.

[0035] The outer peripheral surface of the flange cover 65 is at least partially provided with cooling fins 66. Preferably, the cooling fins 66 are provided on the side closer to the motor housing 4. The side closer to the motor housing 4 is located near the outlet of the cooling airflow for the grinding tool, so the cooling fins 66 can be partially or completely exposed to the cooling airflow to maximize the cooling function.

[0036] According to another embodiment of the invention, the gear housing 7 further includes at least one threaded seat 8; the threaded seat 8 is also made of metal and is molded together with the metal insert 70 using plastic. In addition to serving as an interface with the gear transmission mechanism, the gear housing 7 also includes interfaces for connecting external components (e.g., side handles, auxiliary handles, etc.). Such interfaces are typically threaded seats, and external components can be easily and reliably connected to the gear housing via threaded connections. These threaded seats should also be pre-formed from metal, placed in an injection mold together with the metal insert, and then molded with plastic overlay. It is understood that these metal inserts can also be part of the main metal insert.

[0037] According to a preferred embodiment of the invention, there are three threaded seats 8, respectively arranged on the left, right, and top of the gear housing. Therefore, external components can be installed in different positions according to user needs and application scenarios, resulting in more user-friendly operability. For example, the right-side threaded seat 8 is used to receive a side handle, which is more suitable for users who typically grip the main handle with their left hand.

[0038] According to the above embodiments, the gear housing is formed by overmolding a lightweight metal insert with plastic or composite material, which reduces the weight of the grinding tool and the load on the user's hands and arms. Since the outer surface of the gear housing is made of a plastic or composite material with low thermal conductivity, the temperature change is minimal even when the user presses the upper part of the gear housing with their palm, reducing hand load and significantly improving comfort. Furthermore, using pre- or post-processed metal inserts ensures the functionality and geometric accuracy of all interfaces with adjacent parts (such as bearings), thereby reducing weight while maintaining relevant geometric accuracy. Additionally, the metal insert also aids in heat dissipation.

[0039] As described above, although exemplary embodiments of the invention have been explained herein with reference to the accompanying drawings, the invention is not limited to the specific embodiments described above and may have many other embodiments. The scope of the invention should be defined by the claims and their equivalents.

Claims

1. A grinding tool (1), the grinding tool comprising: A motor (3) having a rotating shaft (2); a motor housing (4) housing the motor (3); a spindle (5) driven by the motor (3) and extending in a direction intersecting the rotating shaft; a gear transmission mechanism (6) transmitting rotation of the rotating shaft (2) to the spindle (2); an end tool mounted on the spindle (5); and a gear housing (7) mounted in front of the motor housing (4) and used to receive the gear transmission mechanism (6). Its features are, The gear housing (7) is formed from a metal insert (70) molded and covered with plastic or composite material.

2. The grinding tool (1) according to claim 1, characterized in that, The gear transmission mechanism (6) includes a drive gear (60) connected to the rotating shaft (2) and at least one driven gear (64) meshing with the drive gear (60). The drive gear (60) is supported in the gear housing (7) by means of a first bearing (61). The main shaft (5) passes through the center of the driven gear (64) and is supported in the gear housing (7) by means of at least one second bearing (62). The metal insert (70) includes a first bearing seat (71) for supporting the first bearing (61) and a second bearing seat (72) for supporting the second bearing (62).

3. The grinding tool (1) according to claim 2, characterized in that, The metal insert (70) further includes an annular portion (74) circumferentially surrounding the driven gear (64).

4. The grinding tool (1) according to claim 3, characterized in that, The first bearing housing (71) is arranged in the axial direction of the rotating shaft (2) and is connected to the outer peripheral surface of the annular portion (74).

5. The grinding tool (1) according to claim 4, characterized in that, The upper edge of the annular portion (74) is provided with a rib (73) extending toward the second bearing seat (72).

6. The grinding tool (1) according to claim 5, characterized in that, The gear transmission mechanism (6) further includes a flange cover (65) disposed below the driven gear (64) and connected to the bottom of the gear housing (7). The flange cover (65) is substantially cylindrical and has a hollow cavity (67). The driven gear (64) is pre-assembled to the top of the flange cover (65), a main bearing (63) is mounted in the cavity (67), and the upper portion of the flange cover (65) is at least partially in contact with the annular portion (64).

7. The grinding tool (1) according to claim 6, characterized in that, The outer peripheral surface of the flange cover (65) is provided with cooling fins (66) at least partially, and these cooling fins (66) are preferably arranged on the side close to the motor housing (4).

8. The grinding tool (1) according to any one of claims 1 to 7, characterized in that, The metal insert (70) is integrally formed.

9. The grinding tool (1) according to claim 8, characterized in that, The gear housing further includes at least one threaded seat (8); the threaded seat (8) is also made of metal and is molded together with the metal insert (70) in plastic or composite material.

10. The grinding tool (1) according to claim 9, characterized in that, The threaded seat is arranged on the top and / or left and right sides of the gear housing (7) and is used to connect the side handle.

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