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Title:
CIRCULAR SAW
Document Type and Number:
WIPO Patent Application WO/2020/200859
Kind Code:
A1
Abstract:
A handheld circular saw (1), comprising a housing (10), a drive unit (20), a saw blade shaft (16, 23) connected to the drive unit (20) and a bearing cover (24) surrounding the saw blade shaft (16, 23), and a saw blade guard (18), the saw blade shaft (16, 23) being constructed so as to be capable of supporting a saw blade (16) for the circular saw (1) and defining a rotation axis (25), the saw blade guard (18) comprising a mounting ring (185), the mounting ring (185) defining a circular opening (186) and surrounding the bearing cover (24), and the saw blade guard (18) being capable of rotating around the rotation axis (25) between a closed position and an open position; an inner side of the circular opening (186) of the mounting ring (185) of the saw blade guard (18) is provided with at least one slot (188) or protrusions. The present invention helps to reduce wear during rotation of the saw blade guard (18); at the same time, since a gap of the slot (188) or protrusions can form an accumulation reservoir, in order to temporarily accommodate dust and chips produced in the course of cutting and expel same in a timely manner, the stability of normal operation of the circular saw (1) is ensured and the safety of the circular saw (1) in use is improved.

Inventors:
JACK SEE (CN)
KOH ALEX (CN)
ZHU HEAVEN (CN)
LIN ZHI (CN)
Application Number:
PCT/EP2020/057910
Publication Date:
October 08, 2020
Filing Date:
March 23, 2020
Export Citation:
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Assignee:
HILTI AG (LI)
International Classes:
B27G19/04; B23D45/16; B27B9/00
Foreign References:
EP2409820A12012-01-25
Attorney, Agent or Firm:
HILTI AKTIENGESELLSCHAFT (LI)
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Claims:
CLAIMS

1. A handheld circular saw, comprising a housing, a drive unit, a saw blade shaft connected to the drive unit and a bearing cover surrounding the saw blade shaft, and a saw blade guard, the saw blade shaft being constructed so as to be capable of supporting a saw blade for the circular saw and defining a rotation axis, the saw blade guard comprising a mounting ring, the mounting ring defining a circular opening and surrounding the bearing cover, and the saw blade guard being capable of rotating around the rotation axis between a closed position and an open position, characterized in that the circular opening of the mounting ring of the saw blade guard is provided with at least one slot.

2. The handheld circular saw according to Claim 1 , characterized in that multiple said slots are provided, arranged at uniform intervals on an inner peripheral face of the circular opening.

3. The handheld circular saw according to Claim 1 or 2, characterized in that the slot is substantially a radial cutout extending in the circumferential direction of the circular opening on an inner peripheral face of the circular opening.

4. The handheld circular saw according to Claim 3, characterized in that a cross section of the cutout is substantially a rectangle or parallelogram. 5. The handheld circular saw according to Claim 1 or 2, characterized in that the slot is a narrow slot arranged obliquely on an inner peripheral face of the circular opening.

6. The handheld circular saw according to Claim 5, characterized in that the narrow slot is in the form of a straight line, or a curved line, or a bent line.

7. A handheld circular saw, comprising a housing, a drive unit, a saw blade shaft connected to the drive unit and a bearing cover surrounding the saw blade shaft, and a saw blade guard, the saw blade shaft being constructed so as to be capable of supporting a saw blade for the circular saw and defining a rotation axis, the saw blade guard comprising a mounting ring, the mounting ring defining a circular opening and surrounding the bearing cover, the saw blade guard being capable of rotating around the rotation axis between a closed position and an open position, characterized in that an inner peripheral surface of the circular opening of the mounting ring of the saw blade guard is provided with a number of protrusions.

8. The handheld circular saw according to Claim 7, characterized in that the protrusions are of equal height and uniformly arranged on the inner peripheral surface of the circular opening. 9. The handheld circular saw according to Claim 8, characterized in that the protrusions are in the form of bosses, or ribs, or protruding points.

Description:
Circular saw

TECHNICAL FIELD

The present invention relates to an electric tool, in particular to a handheld circular saw.

BACKGROUND ART

Circular saws are widely used for cutting workpieces, such as wood, metal and many other materials. A circular saw generally comprises a rotating saw blade assembly and a drive unit which are disposed in a housing, a handle disposed on the housing, and a base or support plate which comes into contact with a workpiece during a cutting operation, as well as an upper protective cover and a moveable saw blade guard. The upper protective cover and the moveable saw blade guard generally cover the entire periphery of a saw blade, except for a front end which initially contacts the workpiece to be cut.

The saw blade of the circular saw is mounted on a saw blade shaft in a fixed manner by means of a mounting flange, a clamping flange and clamping screws. When an electric motor is started up, the drive unit drives the saw blade shaft to rotate, and the saw blade rotates with the saw blade shaft, thereby cutting the workpiece. The saw blade guard is generally used to protect a user from being hurt by the saw blade. In a non-operational state of the circular saw, the saw blade guard is in a closed position, and almost surrounds a lower half periphery of the saw blade, thereby avoiding accidental harm due to a sharp edge of the saw blade coming into contact with the user. In an operational state of the circular saw, the saw blade guard is biased towards the closed position around a lower part of the saw blade by means of a tensile elastic element or torsional elastic element. When the user pushes the circular saw forwards to perform cutting, the workpiece comes into contact with a front edge of the saw blade guard, thereby generating a torque that is opposite to and greater than the torque of the tensile elastic element or torsional elastic element, which causes the saw blade guard to rotate towards an open position; thus, in the process of the workpiece being cut by the saw blade, the saw blade guard can prevent a rear side of the saw blade rotating at high speed from accidentally coming into contact with the user, and at the same time protects the user from being hurt by chips scattered from the workpiece due to the cutting of the saw blade. Generally, the saw blade guard is pivotably mounted to a bearing cover of the saw blade shaft of the circular saw by means of a mounting ring, and when the saw blade guard moves from the closed position to the open position, the mounting ring pivots around the bearing cover; there is an appropriate gap, not a tight fit, between an inner diameter of the mounting ring and an outer diameter of the bearing cover. The saw blade produces large amounts of flying chips and dust in a cutting toolprocess; thus, although many circular saws are equipped with dust accumulation means, a small amount of dust or flying chips will still fall into the gap between the mounting ring of the saw blade guard and an outer peripheral face of the bearing cover, and this will result in a safety hazard, as dust, once accumulated to a certain degree, will affect the normal rebound of the saw blade guard or the biasing thereof to the closed position.

SUMMARY OF THE INVENTION

The present invention has been created in view of the above situation, with the objective of providing a handheld circular saw, comprising a housing, a drive unit, a saw blade shaft connected to the drive unit and a bearing cover surrounding the saw blade shaft, and a saw blade guard, the saw blade shaft being constructed so as to be capable of supporting a saw blade for the circular saw and defining a rotation axis, the saw blade guard comprising a mounting ring, the mounting ring defining a circular opening and surrounding the bearing cover, and the saw blade guard being capable of rotating around the rotation axis between a closed position and an open position; an inner side of the circular opening of the mounting ring of the saw blade guard is provided with at least one slot.

According to a preferred embodiment of the present invention, multiple said slots are provided, arranged at uniform intervals on an inner peripheral face of the circular opening. The slot is substantially a radial cutout extending in the circumferential direction of the circular opening on the inner peripheral face of the circular opening. A cross section of the cutout is substantially a rectangle or parallelogram. The rectangular or parallelogram shaped slots arranged uniformly on the peripheral face of the circular opening can be machined and formed simply and conveniently, facilitating manufacture.

According to a preferred embodiment of the present invention, the slot is a narrow slot arranged obliquely on the inner peripheral face of the circular opening. The oblique narrow slot is more helpful in expelling chips. The narrow slot may be in the form of a straight line, or a curved line, or a bent line.

According to another embodiment of the present invention, a handheld circular saw comprises a housing, a drive unit, a saw blade shaft connected to the drive unit and a bearing cover surrounding the saw blade shaft, and a saw blade guard, the saw blade shaft being constructed so as to be capable of supporting a saw blade for the circular saw and defining a rotation axis, the saw blade guard comprising a mounting ring, the mounting ring defining a circular opening and surrounding the bearing cover, the saw blade guard being capable of rotating around the rotation axis between a closed position and an open position, and a number of protrusions being provided in the circular opening of the mounting ring of the saw blade guard.

According to a preferred embodiment of the present invention, the protrusions are of equal height and uniformly arranged on an inner surface of the circular opening. The protrusions may be in the form of bosses, or ribs, or protruding points.

Due to the slot or protrusions on the circular opening of the saw blade guard mounting ring, when the circular opening of the saw blade guard mounting ring is mounted on the bearing cover, a surface of contact between an inner surface of the circular opening and an outer diameter surface of the bearing cover is reduced, helping to reduce wear during rotation of the saw blade guard, and at the same time, since a gap of the slot or protrusions can form an accumulation reservoir, in order to temporarily accommodate dust and chips produced in the course of circular saw cutting, and the dust and chips can be expelled as the saw blade guard rotates or vibrates, the possibility of the saw blade guard being unable to normally rotate and rebound to the closed position is considerably reduced, ensuring the stability of normal operation of the circular saw and improving the safety of the circular saw in use.

DESCRIPTION OF THE DRAWINGS

The embodiments mentioned can be better understood through the following detailed description while perusing the accompanying drawings. It is emphasized that the various components are not necessarily drawn to scale. In fact, dimensions can be enlarged or reduced at will for the purposes of clear discussion. In the drawings, identical reference labels denote identical elements.

Fig. 1 shows a perspective view of a handheld circular saw according to the present invention.

Fig. 2 is an exploded perspective view of the handheld circular saw according to the present invention shown in fig. 1.

Fig. 3 is a partial schematic diagram showing the connection and mounting of a saw blade, saw blade guard, drive unit and saw blade shaft of a circular saw of the present invention.

Fig. 4 shows a perspective view of a demonstrative saw blade guard of a circular saw of the present invention.

Fig. 5 shows a perspective view of another demonstrative saw blade guard of a circular saw of the present invention.

Fig. 6 shows a perspective view of a saw blade guard of another demonstrative circular saw of the present invention.

Fig. 7 shows an alternative schematic embodiment of a slot of a lower guard saw blade of the present invention.

DESCRIPTION OF EMBODIMENTS A handheld circular saw according to an embodiment of the present invention is described below with reference to figs. 1 - 7. The present invention relates to a circular saw used for forming an opening in an object being machined; the circular saw is widely used for cutting workpieces such as wood, vinyl siding and many other materials, including pieces of metal.

An electric handheld circular saw 1 is shown in figs. 1 and 2; the handheld circular saw 1 comprises a housing 10, handles 11 and 12 for a user to grip, a housing-supported drive unit 20 in the housing 10, a support plate 15 and a saw blade 16, an upper protective cover 17, and a saw blade guard 18.

The housing 10 may be formed of metal or plastic, such that the housing 10 is very sturdy and lightweight. In this embodiment, the circular saw 1 comprises a front handle 11 and a rear handle 12, which are individually supported on the housing 10 and constructed so as to be grippable by a user of the circular saw 1 during a cutting operation. The rear handle 12 comprises a trigger switch (not shown) which is operably connected to an electric motor. In other embodiments, the circular saw 1 may not comprise the front handle 11.

The upper protective cover 17 is supported by the housing 10 and is fixed in a suitable position relative to the housing 10. The support plate 15 is pivotably connected to the housing 10, and constructed so as to be capable of supporting the housing 10 and the drive unit 20 above a workpiece W during a cutting operation. A lower surface of the support plate 15 forms a workpiece support face; the saw blade 16 extends through a gap in the support plate 15 and is partially surrounded by the upper protective cover 17 in an arc shape. By means of the workpiece support face, the handheld circular saw 1 can be placed onto a workpiece to be machined, and guided along a surface of the workpiece. If necessary, the saw blade 16 may also be tilted relative to the support plate 11 , in order to allow oblique cutting to be carried out. The arrow 19 indicates the direction of rotation of the saw blade 16.

Referring to figs. 2 and 3, the circular saw of the present invention comprises a drive unit 20, which may be powered by a battery (not shown) shown in this embodiment, but of course could also be powered through a corded power source as is well known in the art. The drive unit 20 comprises a drive electric motor 201 , a drive shaft 202, a drive bearing 203 and a bearing block 204; the drive bearing 203 surrounds the drive shaft 202, and is mounted in the bearing block 204. The circular saw further comprises a saw blade shaft 23, with a bearing cover 24 surrounding the saw blade shaft 23; the bearing cover 24 may be connected to the bearing block 204 in a fixed manner by means of screws, and the saw blade shaft 23 is constructed so as to be capable of supporting the saw blade 16 for the circular saw and defines a rotation axis 25. Moreover, the saw blade shaft 23 is connected to the drive shaft by means of a gearbox (not shown). When the electric motor is triggered, the drive shaft 202 drives the saw blade shaft 23 to rotate by means of gears, and the saw blade 16 rotates around the rotation axis 25 with the saw blade shaft 23. In the embodiment shown, the gearbox comprises multiple gears (not shown) which are operably connected to the electric motor 20 and the saw blade shaft 23. The gearbox is constructed so as to be capable of reducing a rotation speed of an output (not shown) of the electric motor to a speed suitable for turning the saw blade 16. In other demonstrative embodiments, the gearbox may also comprise a worm transmission apparatus (not shown) for driving the saw blade shaft 16; in fact, the drive unit of the circular saw 1 may comprise a transmission apparatus of any type.

Referring to figs. 2 - 4, the saw blade guard 18 is rotatably mounted to the housing 10 of the circular saw 1. The saw blade guard 18 is constructed so as to be capable of rotating from a closed position to an open position around a rotation axis 25. The circular saw 1 further comprises a biasing member (not shown) such as a torsional elastic element; the biasing member is constructed so as to be capable of biasing the saw blade guard 18 towards the closed position. The saw blade guard 18 comprises a lower wall 180 and, an inside wall 181 and an outside wall 182 individually extending from the lower wall 180. The lower wall 180 has a substantially circular contour and is adapted to a periphery of the saw blade 16, thereby protecting the saw blade 16 from damage and also protecting the user from accidental contact with the saw blade 16. The lower wall 180 extends from a front edge part 183 to a rear edge part 184. The front edge 183 should be slightly lower than the workpiece support face when in a mounted position. An inner arc-shaped side edge and an outer arc-shaped side edge of the lower wall 180 extend upwards substantially perpendicularly to form the inside wall 181 and the outside wall 182. The inside wall 181 is substantially fan-shaped, and a mounting ring 185 is included at the centre of the fan shape thereof, the mounting ring 185 defining a circular opening 186; the saw blade shaft 23 and the bearing cover 24 extend through the circular opening 186. A centre point 187 of the opening 186 is coincident and aligned with the rotation axis 25. The saw blade guard 18 pivots around the centre point 187 from the closed position to the open position.

The saw blade guard 18 may be made of cast aluminium or moulded plastic, and the surface thereof is mostly flat; preferably, the surface may be covered with a wear- resistant material plate (e.g. stainless steel).

At least one slot 188 is provided in the circular opening 186 of the mounting ring 185 of the saw blade guard 18. Due to the slot 188, when the circular opening 186 of the saw blade guard mounting ring is mounted on the bearing cover 24, a surface of contact between an inner surface of the circular opening 186 and an outer ring surface of the bearing cover 24 is reduced, helping to reduce wear during rotation of the saw blade guard, and at the same time, since a gap formed by the slot can form an accumulation reservoir or a dust accumulation zone, in order to temporarily accommodate dust and chips produced in the course of circular saw cutting, and the dust and chips can be expelled as the saw blade guard rotates or vibrates, the possibility of the saw blade guard being unable to normally rotate and rebound to the closed position is considerably reduced, ensuring the stability of normal operation of the circular saw and improving the safety of the circular saw in use.

According to a preferred embodiment of the present invention, multiple said slots 188 are provided, arranged at uniform intervals on an inner peripheral face of the circular opening 186, in order to achieve a better result in terms of clear dust accumulation.

The slot 188 is substantially a radial cutout extending along the circular opening on the inner peripheral face of the circular opening 186 of the mounting ring, i.e. the slot 188 is a gap formed on the inner peripheral face of the circular opening; the gap is radial in order to temporarily accommodate dust and chips produced in the course of cutting. Moreover, the slot extends circumferentially in the circular opening, such that the function of removal by sweeping can be realized to a certain degree during rotation of the saw blade guard, and dust and chips can be expelled from the guard as the saw blade guard rotates.

According to a preferred embodiment of the present invention, as shown in fig. 6, the slot is a narrow slot 189 arranged obliquely on the inner peripheral face of the circular opening. The oblique narrow slot is more helpful in expelling chips. As shown in fig. 7, the narrow slot may be in the form of a straight line, or a curved line, or a bent line. The shape of the narrow slot is non-limiting; a suitable shape is selected mainly on the basis of overall consideration of convenience of machining and manufacture and a better dust removal result.

With regard to the width of the slot, the term“slot” should not be interpreted with any restrictive meaning, i.e. the width may be quite wide, e.g. in an embodiment of the present invention, the width of the slot is substantially equal to the length of the slot, and the width of the slot may even be greater than the length of the slot, e.g. a cross section of the cutout may be substantially formed as a rectangle or parallelogram. The distance between two adjacent slots may also be defined according to particular application conditions, e.g. when used in a circular saw which mainly cuts workpieces that do not produce a particularly large amount of dust, the width of the slots may be smaller, or the distance between slots may be larger, for convenience of machining. However, when used in a circular saw for workpieces that produce a very large amount of chips and dust, the width of the slot may be designed to be larger, or the distance between adjacent slots may be smaller, in order to better realize the functions of dust accumulation and removal. Thus, in this respect, the term“slot” or“narrow slot” should ultimately be appropriate. Similarly, the slot or narrow slot may have a desired depth, e.g. 3 - 5 mm.

According to another embodiment of the present invention, a handheld circular saw comprises a housing, a drive unit, a saw blade shaft connected to the drive unit and a bearing cover surrounding the saw blade shaft, and a saw blade guard, the saw blade shaft being constructed so as to be capable of supporting a saw blade for the circular saw and defining a rotation axis, the saw blade guard comprising a mounting ring, the mounting ring defining a circular opening and surrounding the bearing cover, the saw blade guard being capable of rotating around the rotation axis between a closed position and an open position, and a number of protrusions being provided in the circular opening of the mounting ring of the saw blade guard.

In fact, the protrusions have the same function as the slots; a slot is in fact formed between two adjacent protrusions, and so the solution whereby protrusions are disposed in the circular opening can similarly help to reduce wear during rotation of the saw blade guard. At the same time, a gap formed between the protrusions can form an accumulation reservoir or a dust accumulation zone, in order to temporarily accommodate dust and chips produced in the course of circular saw cutting, and the dust and chips can be expelled as the saw blade guard rotates or vibrates, thereby considerably reducing the possibility of the saw blade guard being unable to normally rotate and rebound to the closed position, ensuring the stability of normal operation of the circular saw and improving the safety of the circular saw in use.

According to a preferred embodiment of the present invention, the protrusions are of equal height and uniformly arranged on an inner surface of the circular opening. The protrusions may be in the form of protruding faces, or ribs, or protruding points. Similarly, with regard to the shape, arrangement and parameters such as height of the protrusions, these should not be interpreted with any restrictive meaning, but are defined according to particular application conditions, preferably such that machining is convenient while the functions of good dust accumulation and removal are achieved.

As stated above, although demonstrative embodiments of the present invention have already been explained herein with reference to the accompanying drawings, the present invention is not limited to the particular embodiments described above; many other embodiments are possible, and the scope of the present invention should be defined by the claims and their equivalent meaning.