CN115889889A - Circular saw - Google Patents

Abstract

A circular saw including a housing, a driving unit accommodated in the housing, a saw blade driven to rotate to cut a work piece, a speed reduction mechanism installed between the driving unit and the saw blade for changing a rotation speed of the saw blade, and a blade guard; the housing includes a gear box at least partially housing the reduction mechanism, the gear box being provided with at least one vent. According to the circular saw of the present invention, it is possible to effectively suppress the expansion of air in the gear case and to prevent the seizure of the blade guard due to the leakage of the lubricant enclosed in the gear case, thereby improving the safety, quality and durability of the circular saw.

Description

Circular saw

Technical Field

The present invention relates to power tools, and more particularly to circular saws.

Background

Circular saws are a widely used power tool for cutting workpieces such as wood, metal and many other materials.

Circular saws generally include a drive unit disposed within a housing, a gear shaft connected to the drive unit, and a saw blade mounted on the gear shaft. The drive unit, such as a motor, includes a drive shaft that engages a gear shaft within a gear case of the circular saw. The gear engagement mechanism is a speed reduction mechanism for changing the rotational speed of the saw blade. When the motor starts to operate, the driving shaft drives the gear shaft to rotate, and the saw blade is driven to rotate along with the gear shaft, so that the workpiece is cut. Circular saws also typically include a handle disposed on the housing and a support plate that contacts the workpiece during a cutting operation, as well as an upper protective cover and a rotatable blade guard. The rotatable blade guard is rotatable about the rotational axis of the blade between its closed and operative positions, preventing accidental contact of the rear side of the blade rotating at high speed with a user during cutting of a workpiece by the blade, while also protecting the user from flying debris separated from the workpiece during the cutting process.

Typically, a certain amount of lubricant needs to be added to the gearbox to lubricate the gears during their meshing. The lubricant used is generally a soft, thick, greasy, semi-solid grease, and therefore, the gearbox needs to have good sealing properties to prevent grease from leaking out of the gearbox. In order to achieve high sealing performance, various sealing members such as 0-ring, oil seal, contact seal bearing, etc. may be provided.

However, during operation of the circular saw, the reduction mechanism in the gear case generates heat due to high-speed rotation, which increases the temperature inside the sealed gear case, and expands the air in the gear case. In this case, it is necessary to provide a vent hole so that high-temperature air in the gear case can be exhausted. Meanwhile, the grease in the gear case, which is substantially uniformly distributed in the gear case in the operating state of the circular saw, may leak from the air vent. Further, the semi-solid grease may be partially liquefied by the high-temperature and high-pressure gas, and may leak from the vent hole. Grease leaking from the gear case is cooled and then accumulates in the gap between the bearing cap of the gear shaft and the mounting ring of the blade guard. Because a small amount of dust or flying debris can also fall into the gap in the process of cutting the workpiece by the saw blade, after solid grease is mixed into the dust or flying debris, the normal rebound or bias of the saw blade shield to the closed position can be influenced, and potential safety hazards are caused.

Disclosure of Invention

The present invention is directed to provide a circular saw capable of effectively suppressing air expansion in a gear case and preventing seizure of a blade guard due to leakage of a lubricant sealed in the gear case, thereby improving safety, quality and durability of the circular saw.

A circular saw including a housing, a driving unit accommodated in the housing, a saw blade driven to rotate to cut a work piece, a speed reduction mechanism installed between the driving unit and the saw blade for changing a rotation speed of the saw blade, and a blade guard; the housing includes a gear box at least partially housing the reduction mechanism, the gear box being provided with at least one vent. The gear box is provided with a vent hole which can discharge high-temperature and high-pressure gas caused by the running of the speed reducing mechanism in the working process of the circular saw.

According to one embodiment of the invention, the drive unit comprises a motor having a drive shaft, the reduction mechanism comprises a gear shaft defining the axis of rotation of the saw blade, the gear shaft is configured with an input end connected to the drive shaft of the motor in a gear-engaging manner at one end and an output end supporting the saw blade at the other end, the gear housing has a bearing seat for receiving the drive shaft at a side facing the drive unit and a recess for receiving the input end of the gear shaft at a side facing the saw blade, the bearing seat and the recess being in at least partial communication, the blade guard is mounted to the output end of the gear shaft and is rotatable about the axis of rotation of the saw blade between its operative and closed positions.

According to a preferred embodiment of the invention, the pocket comprises a side circumferential surface substantially parallel to the rotational axis of the saw blade and a bottom surface substantially perpendicular to the rotational axis of the saw blade, the ventilation hole being located on the bottom surface of the pocket. Thus, when a small amount of grease is leaked from the vent hole, the grease is discharged from the inner side (the side facing the gear shaft, the saw blade and the saw blade shield) of the gear box to the outer side (the side facing away from the gear shaft, the saw blade and the saw blade shield) of the gear box through the vent hole, so that clamping stagnation caused by the accumulation of a mixture of grease, dust, flying debris and the like between gaps of the saw blade shield and the bearing cover does not exist, and the saw blade shield can normally rotate between the working position and the closed position.

Preferably, the pocket floor is substantially circular, with the center of the floor coinciding with the axis of rotation of the saw blade. The vent hole is located at a position above a horizontal plane extending along the rotational axis of the saw blade on the bottom surface. When the circular saw is in a non-working state, the lubricating grease in the gear box tends to concentrate on the lower half part of the gear box, and therefore the vent hole is arranged at a height exceeding the center of the bottom surface, and leakage of the lubricating grease from the gear box is avoided.

According to still another preferred embodiment of the present invention, the input end of the gear shaft has a transmission gear and a journal, the side circumferential surface of the recess substantially surrounds the transmission gear, the bottom surface of the recess is provided at the center thereof with a bearing hole supporting the journal, and the distance from the vent hole to the center of the bottom surface is smaller than the radius of the root circle of the transmission gear. The vent hole is arranged below the transmission gear, and is also beneficial to preventing excessive leakage of the lubricating grease.

According to another preferred embodiment of the invention, the radius extending through the ventilation aperture in the bottom surface has a smaller angle to the vertical than the radius extending through the centre line of the drive shaft. That is to say, the position of air vent is set up in the first half of bottom surface is close to the sector area of the vertical direction that passes the bottom surface center, and like this both can effectual discharge high pressure high temperature air, also can prevent simultaneously that grease from this air vent a large amount of even whole leaking outside the gear box, guarantee to remain the grease of sufficient volume in the gear box, carry out abundant lubrication to reduction gears all the time in the life range of annular saw.

The end of the driving shaft is provided with a driving gear, a bearing is sleeved on the driving shaft, the bearing seat comprises a hole part for supporting the bearing and a cavity part which is at least partially overlapped with the concave seat along the axial direction and is used for accommodating the driving gear, a plurality of reinforcing ribs are arranged on the periphery of the hole part, and the positions of the vent holes are kept away from the reinforcing ribs. Therefore, the processing technology of the vent holes is simple and convenient, and the ventilation and exhaust effects are better.

More preferably, the vent hole is obliquely arranged on the bottom surface, and one end of the vent hole facing the gear shaft is closer to the center of the bottom surface than the other end of the vent hole away from the gear shaft. The obliquely arranged vent holes have longer exhaust paths. The vent holes are inclined outwards along the radial direction from one side close to the bearing hole to one side close to the transmission teeth, so that semi-solid or partially liquefied lubricating grease is less prone to leaking from the interior of the gear box to the exterior of the gear box.

According to a further preferred embodiment of the present invention, the vent hole is a through hole having a diameter of not more than 2 mm. The vent holes should be as small as possible, but circular holes having a diameter of no more than 2mm are preferred in view of ease of machining and cost.

Drawings

The embodiments are better understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that the various features are not necessarily drawn to scale. In fact, the dimensions may be arbitrarily increased or decreased for clarity of discussion. In the drawings, like numbering represents like elements.

FIG. 1 illustrates a partial schematic view of a circular saw according to one embodiment of the present invention;

FIG. 2 is a partial perspective view of the circular saw of FIG. 1 in accordance with one embodiment of the present invention;

FIG. 3 is a cross-sectional view of an exemplary drive unit and reduction mechanism arrangement within a gear case of the circular saw of the present invention;

FIG. 4 is a schematic view of an exemplary gear case of the circular saw of the present invention shown to the side facing the saw blade;

FIG. 5 is an enlarged partial schematic view of the gearbox shown in FIG. 3 at C;

FIG. 6 is a schematic view of a side of the gearbox shown in FIG. 3 facing the drive unit;

FIG. 7 is an enlarged partial schematic view at B of the gearbox shown in FIG. 5.

Detailed Description

Hereinafter, a circular saw according to an embodiment of the present invention will be described with reference to fig. 1 to 7. The present invention relates to circular saws for forming openings in work pieces, widely used for cutting work pieces such as wood, vinyl siding and many other materials, including for cutting metal pieces. The "circular saw" according to the present invention may be a circular saw for woodworking, metalworking, ceramic processing, and/or plastic processing, in which a workpiece is cut by a rotating saw blade, and a portable circular saw, a table circular saw, or the like is also included in the "circular saw" described herein. In addition, the "circular saw" includes a cutting saw, a band saw, a cutting wheel, a diamond wheel, and the like. The "power source" of the power tool in the present invention is typically an electric motor, and includes an air motor, an engine, and the like.

According to an exemplary embodiment of the present invention, as shown in fig. 1 to 3, a circular saw 1 includes a housing 10, a driving unit 11 accommodated in the housing 10 and supported by the housing, a saw blade 12 driven to rotate to cut a work piece, a speed reducing mechanism 13 installed between the driving unit and the saw blade for changing a rotation speed of the saw blade, an upper cover 14, and a blade guard 15, the housing 10 further including a gear case 16 at least partially accommodating the speed reducing mechanism 13.

The housing 10 may be formed of metal or plastic such that the housing 10 is very strong and lightweight. In one embodiment of the invention, the upper guard 14 is supported by the housing 10 and is fixed in position relative to the housing 10, with the upper guard 14 substantially covering the upper half of the circumference of the saw blade 12.

Referring to fig. 2 and 3, the driving unit 11 may be powered by a battery (not shown) according to an embodiment of the present invention, but may be powered by a wired power connection as is well known in the art. The driving unit 11 includes a driving motor 18, a driving shaft 19, and a driving bearing 20, wherein the driving bearing 20 is sleeved on the driving shaft 19, and the driving gear 21 is provided at the end of the driving shaft 19.

According to one embodiment of the present invention, the speed reduction mechanism 13 is configured to reduce the output rotational speed of the motor 18 to a speed suitable for rotating the saw blade 12. According to an exemplary embodiment of the present invention, the speed reducing mechanism includes a gear shaft 22, one end of the gear shaft 22 is an input end 23 connected to the driving shaft 19 of the motor by means of gear engagement, the input end 23 has a transmission gear 24 and an axially outwardly extending journal 32, and the other end is an output end 25 supporting the saw blade 12. The gear shaft defines a rotational axis 17 of the saw blade, i.e. the rotational center of the gear shaft output coincides with the rotational axis 17 of the saw blade. When the motor 18 is energized, the drive shaft 19 rotates the transmission gear 24 of the gear shaft 22 via the drive gear 21, and the saw blade 12 rotates with the gear shaft 22 about the axis of rotation 17. In an alternative embodiment, the reduction mechanism may comprise multiple sets of geared transmission mechanisms. In other exemplary embodiments, the reduction mechanism may also include a worm drive (not shown) for driving the gear shaft.

Referring to fig. 2 to 7, the housing 10 further includes a gear case 16, the gear case 16 being located substantially at the rear side (right side surface in fig. 2 and 3) of the upper cover 14, and preferably, the gear case 16 and the upper cover 14 are integrally formed. According to an exemplary embodiment of the present invention, the gear housing 16 is a cavity extending from the bottom center of the back of the upper cover, and a plurality of ribs may be disposed in the cavity. The gear box 16 has a bearing seat 26 for receiving the drive shaft on the side facing the drive unit 11 and a recess 27 for receiving the input 23 of the gear shaft on the side facing the saw blade, the bearing seat 26 and the recess 27 being in at least partial communication. Preferably, the bearing housing 26 includes a bore portion 33 for supporting the bearing and a cavity portion 34 at least partially coincident with the recess for receiving the drive gear of the drive shaft. In this way, the drive gear 21 of the drive shaft 19 is connected in a geared manner to the transmission gear 24 of the input end 23 of the gear shaft 22 in the region where the cavity 34 and the recess 27 coincide.

The blade guard 15 is pivotally mounted by a mounting ring to the bearing cap of the output end 25 of the gear shaft 22. The saw blade 12 is fixedly mounted to the output end 25 of the gear shaft by mounting and clamping flanges and clamping screws. The blade guard 15 generally covers the lower half of the circumference of the saw blade 12, and the blade guard 15 is configured to be rotatable about a rotational axis 17 of the saw blade 12 between a closed position and an operative position. The circular saw 1 further includes a biasing member (not shown), such as a torsionally resilient element, configured to bias the blade guard 15 toward the closed position. That is, the saw blade 12 and the blade guard 15 are both mounted to the inside of the gear case, i.e., the left side in fig. 2 and 3, while the driving unit 11 is located to the outside of the gear case, i.e., the right side in fig. 2 and 3.

According to a preferred embodiment of the invention, with reference to fig. 2 to 5, said recess 27 comprises a lateral peripheral surface 28 substantially parallel to the rotation axis 17 of said saw blade and a bottom surface 29 perpendicular to the rotation axis 17 of said saw blade, at least one ventilation hole 30 being provided on said bottom surface 29. Thus, grease previously packed in the gear housing for lubrication can be partially discharged from the inside of the gear housing (left side in fig. 3) to the outside of the gear housing (right side in fig. 3), i.e., the side facing away from the gear shaft, the saw blade, and the blade guard, through the vent holes 30 located in the bottom surface of the recess. Therefore, the clamping stagnation caused by the mixture of grease, dust, flying debris and the like accumulated between the saw blade shield 15 and the gap of the bearing cover of the gear shaft does not exist, and the saw blade shield 15 can normally rotate between the working position and the closed position.

Preferably, the bottom surface 29 of the recess is substantially circular, the centre of the bottom surface coinciding with the axis of rotation of the saw blade, the side peripheral surface 28 and the bottom surface 29 forming a cylindrical recess. The side peripheral surface 28 of the recess substantially surrounds the transmission gear 24, and the bottom surface 29 of the recess is provided at its center with a bearing hole 31 that supports a journal 32 of a gear shaft. The journal 32 of the gear shaft 22 is supported in the bearing bore 31 by a bearing, and the position of the ventilation hole 30 on the bottom surface is at least higher than the horizontal plane passing through the rotational axis 17 of the saw blade, where the rotational axis 17 of the saw blade coincides with the center line of the bearing bore 31. That is, the position of the vent 30 on the bottom surface 29 should be at least higher than the level of the center of the bottom surface, at the upper half of the bottom surface. More preferably, the included angle between the vertical direction and the extension line passing through the vent hole 30 and the center of the bottom surface is smaller than the included angle between the vertical direction and the extension line passing through the center of the bearing housing hole 26 and the center of the bottom surface. That is, the positions of the ventilation holes 30 are set in the upper half of the bottom surface in a sector area near the vertical direction passing through the center of the bottom surface. The grease is required to be added into the gear box in advance to lubricate the transmission of the driving shaft and the gear shaft. The grease filling needs to be applied in a sufficient amount according to the service life of the circular saw, so as to ensure good lubrication of the circular saw throughout its life cycle. However, as described above, the semisolid grease is liquefied in a small amount in the high-temperature and high-pressure air, the liquidity of the liquefied lubricant is obviously increased, and the liquefied lubricant may be discharged out of the gear box through the vent hole, so that the vent hole is arranged above the bearing hole, the high-pressure and high-temperature air can be effectively discharged, the grease can be prevented from leaking out of the gear box through a large amount of or even all of the vent hole, a sufficient amount of grease can be kept in the gear box, and the speed reduction mechanism can be lubricated fully all the time in the service life range of the circular saw.

Referring to fig. 6 and 7, according to still another preferred embodiment of the present invention, the outer circumference of the hole part 33 is provided with a plurality of reinforcing ribs 35, and the positions of the vent holes 30 are offset from the positions of the radial reinforcing ribs 35. Therefore, the processing technology of the vent holes is simple and convenient, and the ventilation and exhaust effects are better. The ribs may be used to connect an air deflector 36. Since the vent holes are located in the area surrounded by the reinforcing ribs, a small amount of grease leaking from the vent holes will be received by the air guide device and will not accumulate on the gear shaft or the drive unit.

Preferably, the vent hole 30 is a circular hole with a diameter of not more than 2 mm. The vent holes should be as small as possible, but circular holes having a diameter of not more than 2mm are easy to machine, while ensuring good venting and not causing excessive grease leakage from the gear box, in view of ease of machining and cost. In fact, leakage of grease from the vent hole generally occurs only at the initial stage of starting the circular saw into use, and the amount of grease initially packed in the gear box is high. After a period of use, the gear engagement of the speed reducing mechanism is completely worn, and the storage amount of the lubricating grease in the gear box gradually reaches a balance value, so that the full lubrication of the speed reducing mechanism can be ensured, and more lubricating grease cannot continuously leak from the vent hole.

More preferably, the vent 30 is an oblique vent that is not perpendicular to the bottom surface 29 of the gear box. The obliquely arranged vent holes have longer exhaust paths. Preferably, the vent hole is inclined outwards along the radial direction from one side close to the bearing hole 31 to one side close to the transmission gear 24, so that the grease in a liquefied state is less prone to leaking from the inside of the gearbox to the outside of the gearbox, the grease packaged in the gearbox is ensured, sufficient lubrication for the driving unit and the speed reducing mechanism can be maintained all the time, and the service life of the tool is prolonged.

As described above, although the exemplary embodiments of the present invention have been described in the specification with reference to the drawings, the present invention is not limited to the above-described specific embodiments, but may be in many other embodiments, and the scope of the present invention should be defined by the claims and their equivalents.

Claims (10)

1. A circular saw including a housing, a driving unit accommodated in the housing, a saw blade driven to rotate to cut a work piece, a speed reduction mechanism installed between the driving unit and the saw blade for changing a rotation speed of the saw blade, and a blade guard; the housing includes a gear box at least partially housing the reduction mechanism, wherein the gear box is provided with at least one vent.

2. The circular saw of claim 1, wherein the drive unit includes a motor having a drive shaft, the speed reduction mechanism includes a gear shaft defining an axis of rotation of the saw blade, the gear shaft is configured with an input end coupled to the drive shaft of the motor in gear engagement at one end and an output end supporting the saw blade at the other end, the gear housing has a bearing seat receiving the drive shaft on a side facing the drive unit and a recess receiving the input end of the gear shaft on a side facing the saw blade, the bearing seat and recess being in at least partial communication, the blade guard being mounted to the output end of the gear shaft and rotatable about the axis of rotation of the saw blade between its operative and closed positions.

3. The circular saw of claim 2, wherein the pocket includes a side peripheral surface substantially parallel to the rotational axis of the saw blade and a bottom surface substantially perpendicular to the rotational axis of the saw blade, the vent hole being located on the bottom surface of the pocket.

4. The circular saw of claim 3, wherein the pocket has a generally circular bottom surface, a center of the bottom surface coinciding with the rotational axis of the saw blade.

5. The circular saw of claim 4, wherein the vent hole is located higher on the bottom surface than a horizontal plane extending along a center of the bottom surface.

6. The circular saw of claim 5, wherein the input end of the gear shaft has a transmission gear, and the distance from the vent hole to the center of the bottom surface is smaller than the radius of a root circle of the transmission gear.

7. The circular saw of claim 6, wherein a radius extending through the vent hole on the bottom surface is at a smaller angle to vertical than a radius extending through a centerline of the drive shaft.

8. The circular saw of any one of claims 2 to 7, wherein the drive shaft has a drive gear at a distal end thereof, a bearing is fitted on the drive shaft, the bearing holder includes a hole portion for supporting the bearing and a cavity portion axially coinciding at least in part with the recess for receiving the drive gear, the hole portion has a plurality of reinforcing ribs at an outer periphery thereof, and the vent hole is located so as to avoid the reinforcing ribs.

9. The circular saw of any one of claims 3 to 7, wherein the air vent is obliquely provided on the bottom surface, and one end of the air vent facing the gear shaft is closer to the center of the bottom surface than the other end thereof facing away from the gear shaft.

10. The circular saw of any one of claims 1 to 9, wherein the vent hole is a circular hole having a diameter of no more than 2 mm.

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