CN211388635U - Rotary power tool - Google Patents

Abstract

A rotary power tool includes a spindle supported in a housing for rotation about an axis, the spindle having a thread extending about its axis. A threaded fastener is engageable with the threads for clamping the rotary tool to the spindle. The threaded fastener cannot be over tightened. The lock may be actuated to prevent rotation of the first clutch member relative to the housing. The first torque transmitting feature is fixed for rotation with one of the main shaft and the first clutch member, the first torque transmitting feature is engaged with the second torque transmitting feature under spring force to transmit torque from the main shaft to the first clutch member, and the first torque transmitting feature is moved to a slip position by mating surfaces of the first and second torque transmitting features out of engagement with the second torque transmitting feature when a predetermined torque is exceeded.

Description

Rotary power tool

Technical Field

The present invention relates to a power tool (e.g., circular saw and angle grinder) having a rotary tool spindle that can be locked against rotation by a spindle lock.

Background

Rotary tools such as blades for cutting, grinding, polishing, etc. are typically clamped to the output spindle of a power tool of the type described above by means of a threaded fastener such as a screw or nut. To assist in this process, a spindle lock is engaged by the user to prevent rotation of the threaded fastener from turning the spindle. However, a disadvantage of this arrangement is that the user may over-tighten the threaded fastener, or in use the threaded fastener may become over-tightened, which may damage the tool or even cause the connection to fail, or in use the threaded fastener is not tightened, which may present a safety hazard. It is an object of the present invention to overcome or substantially ameliorate the above disadvantages or, more generally, to provide an improved rotary power tool.

SUMMERY OF THE UTILITY MODEL

According to one aspect of the present invention, there is provided a rotary power tool comprising a housing; a spindle supported in the housing for rotation about an axis; a thread extending about an axis; a threaded fastener engageable with the threads for clamping the rotary tool to the spindle; a first clutch member; the clutch assembly includes a housing, a first clutch member having a first engagement surface, a second engagement surface, a first torque transfer feature fixed for rotation with one of the spindle and the first clutch member, a lock actuatable to prevent rotation of the first clutch member relative to the housing, and a first torque transfer feature fixed for rotation with one of the spindle and the first clutch member, the first torque transfer feature being engaged with the second torque transfer feature under spring force to transfer torque from the spindle to the first clutch member, and the first torque transfer feature being disengaged from the second torque transfer feature by movement of mating surfaces of the first and second torque transfer features to a slip position when a predetermined torque is exceeded.

Preferably, the first clutch member is annular and comprises: a central bore through which the spindle extends; and a circumferential periphery in which a groove is formed for receiving a lock to prevent rotation of the first clutch member relative to the housing. Preferably, the grooves are equally angularly spaced.

Preferably, the mating surfaces are configured such that the magnitude of the predetermined torque varies according to its direction and has a relatively low torque when applied by the threaded fastener in a direction tending to clamp the rotary tool; and a relatively high torque when applied by the threaded fastener in a direction tending to release the rotary tool.

Optionally, the rotary power tool comprises: a compression spring, and a pair of drive and driven gears intermeshed with each other, the drive gear being rotated by the motor, the driven gear being fixed to or integral with the spindle, and wherein the first clutch member is disposed adjacent the driven gear such that respective lateral sides of the driven and first clutch members are opposed, and the first torque transfer feature comprises an inclined face on a lateral side of the driven gear, the second torque transfer feature comprises an inclined face on the first clutch member, the compression spring (e.g. helical) extending around the spindle and having opposed ends which abut shoulders on the first clutch member and the spindle to urge the lateral sides together and provide a spring force.

Preferably, one of the inclined surface and the ramp surface is formed on an arcuate projection of one of the lateral sides and the other of the inclined surface and the ramp surface is formed on a complementary recess of the other of the lateral sides.

Preferably, the inclined surface and the inclined surface are located on respective spirals.

Optionally, the rotary power tool comprises: a second clutch member fixed for rotation with the spindle, wherein the second clutch member is made of a resilient material in a generally annular form including integral circumferentially spaced fingers, and wherein the first torque transfer feature includes ramped surfaces of the fingers, the second torque transfer feature includes ramped surfaces on the first clutch member, and the bending resilience of the fingers provides the resilient force.

Preferably, the fingers have a similar form extending longitudinally in cantilever fashion from the proximal end to the opposite free distal end, and the second clutch member has rotational symmetry about the axis.

Preferably, the fingers have substantially the same cross-section throughout their length, and the width of the fingers is greater than their thickness.

Preferably, the fingers are ridged, each finger has a generally radially aligned ridge, and the ramps are circumferentially spaced apart, and the ramps axially project from a lateral side of the second clutch member opposite the lateral side of the first clutch member.

Preferably, the second clutch member includes a flat disc portion, and each finger projects axially to one side of the disc portion.

Preferably, the rotary power tool comprises a pair of drive gears and a driven gear in mesh with each other, the drive gears being rotated by the motor, the driven gear being fixed to or integral with the spindle, and wherein the first clutch member and the driven gear are spaced apart from each other and the second clutch member is between the first clutch member and the driven gear.

Preferably, the fingers are ridged, each finger has a generally radially aligned ridge, and the ramps are circumferentially spaced apart, and the ramps axially project from a circumference of the second clutch member opposite the inner or outer circumferential surface of the first clutch member.

Preferably, the second clutch member includes an annular collar portion through which the main shaft extends and from which each finger projects radially, and the annular collar portion is disposed in an axially extending opening through the first clutch member.

Optionally, the first torque transmitting feature comprises a pawl and the second torque transmitting feature comprises a cavity that receives the pawl.

Preferably, the pawl is fixed in one of the main shaft and the first clutch member and the cavity is provided in the other of the main shaft and the first clutch member.

Preferably, the main shaft includes a circumferential surface and the first clutch member has a complementary surface extending around the circumferential surface, an interface being defined between the circumferential surface and the complementary surface; each pawl includes a recess that retains a pawl member and a compression spring that provides a spring force and urges the pawl member beyond the interface.

Optionally, the rotary power tool further comprises: a sleeve secured about the spindle; and the pawl is fixed in one of the sleeve and the first clutch member and the cavity is provided in the other of the sleeve and the first clutch member.

Other features and aspects of the present invention will become apparent by consideration of the following detailed description and accompanying drawings.

Drawings

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

fig. 1 is a schematic cross-sectional view of a rotary power tool according to a first embodiment of the present invention.

Fig. 2 is a perspective view of the driven gear of the tool of fig. 1.

Fig. 3 and 4 are perspective views of the inside and outside, respectively, of the first clutch member of the tool of fig. 1.

Fig. 5 is a schematic cross-sectional view of a rotary power tool according to a second embodiment of the present invention.

Fig. 6 is a perspective view of the driven gear of the tool of fig. 5.

Fig. 7 is a perspective view of a second clutch member of the tool of fig. 5.

Fig. 8 is a schematic cross-sectional view of a rotary power tool according to a third embodiment of the present invention.

FIG. 9 is a cross-sectional view of XX of FIG. 8.

Fig. 10 is a perspective view of a first clutch member of the tool of fig. 8.

Fig. 11 is a perspective view of a second clutch member of the tool of fig. 8.

Fig. 12 is a schematic cross-sectional view of a rotary power tool according to a fourth embodiment of the present invention.

Fig. 13 is a cross section of YY of fig. 12.

Fig. 14 is an exploded perspective view of first and second clutch members of a tool according to a fifth embodiment of the present invention.

Detailed Description

Referring to fig. 1, one example of a rotary power tool according to the present invention is a circular saw 10 having a housing 11 (shown schematically in phantom lines), the housing 11 holding a drive including an electric motor (not shown). Torque is applied from the driver to the rotary tool 13 (which in the embodiment shown is a saw blade). The output of the motor comprises a shaft 12, the shaft 12 carrying a drive gear 18 and being supported in bearings 17, the drive gear 18 engaging a driven gear 19 having a larger diameter, the driven gear 19 being fixed for rotation with the main shaft 14. The blade 13 is carried on a spindle 14, the spindle 14 being supported (e.g., by bearings 39, 51) for rotation about an axis 15. As used herein, the term "axial" refers to a direction generally parallel to axis 15. The term "radial" refers to a direction generally orthogonal to axis 15. The term "circumferential" refers to the direction of a circular arc having a radius generally perpendicular to the axis 15.

The blade support disk 20, which is rotationally fixed with the spindle 14, may have a transverse face on which the blade 13 is applied. A thread 21 coaxial with the axis 15 may be provided internally on the spindle 14. Received in the threads 21 is a threaded fastener 22. The fastener 22 abuts the washer 23 and serves to hold the blade 13 against the blade support disk 20, thereby clamping the blade 13 to the spindle 14.

If the user wants to remove or install the rotary tool 13, the fastener 22 must be rotated, and for this purpose, a manual tool 24 separate from the rotary power tool 10 may be used. For example, when the threaded fastener 22 includes a head having a hexagonal socket (as shown), the hand tool 24 may be an allen wrench.

The circular saws of the type to which the above description applies are prior art and therefore each feature is not described in detail.

The torque limiting clutch shown in fig. 1 comprises an annular first clutch member 25 and a cooperating second clutch member, which is effectively integral with the driven gear 19. A central opening 26 extends axially through the first clutch member 25 and receives the main shaft 14 to provide a running fit for rotation relative to the main shaft 14 and axial displacement along the main shaft 14. Similar and equiangularly spaced recesses 27 may be formed in the circumferential periphery of the first clutch member 25. The recess 27 may be shaped to complement the inner end of the lock 28. The lock 28 may be mounted in the housing 11 such that it may be operated by a user to move the lock 28 between a locked position and a released position (not shown). In the locking position, the lock 28 is received in one of the recesses 27. In the release position, the lock 28 is not received in one of the recesses 27. The lock 28 may be disposed in an opening of the housing 11 to reciprocate between the released and locked positions, and in this manner, the lock 28 may be actuated by a user to prevent rotation of the first clutch member 25 relative to the housing 11. The arrangement of the lock 28 and the way in which it cooperates with the recess in the first clutch member 25 may be the same for all embodiments of the invention.

A helical compression spring 29 may extend around the main shaft 14 and have opposite ends that abut the shoulder 16 on the main shaft and the first clutch member 25, wherein the spring 29 may be received in an annular channel 30. The driven gear 19 and the first clutch member 25 have opposite transverse faces 31, 32, respectively, which are urged together by a spring 29.

The rib-like projections 33 from the transverse faces 32 may be of generally identical arcuate form and extend circumferentially with longitudinal curvature according to their radial spacing from the axis 15 and each have inclined faces 34, 35 at opposite ends. Surface 34 may be inclined to follow a helical path, and surface 35 may generally lie in an axial-radial plane. The projections 33 may be equally angularly spaced and aligned so that the first clutch member 25 has rotational symmetry with respect to the axis 15.

To accommodate the projection 33, a complementary recess 36 may be formed in the lateral sides 31 and arranged in a corresponding manner, wherein the longitudinally opposite ends of the recess 36 have a bevel 37 and an abutment surface 38, such that between each projection/recess pair the bevel 34 and the bevel 37 are parallel and likewise the bevel 35 and the abutment surface 38 are parallel and may contact each other.

When the hand tool 24 is used to tighten the fastener 22, the first clutch member 25 rotates with the spindle 14 until the lock 28 is received in one of the recesses 27. The torque applied to the screw 22 is then transferred to the main shaft 14, then to the fixed driven gear 19, and then to the first clutch member 25 itself, via the inclined face 34 of the driven gear 19 and the abutting inclined face 37 on the first clutch member 25, where the lock 28 provides a reverse torque. The torque limit of the clutch (set by the angle of inclination of the inclined surface 34 and the adjacent inclined surface 37 and the stiffness of the spring 29) is reached when the torque transmitting surfaces 34, 37 are disengaged and slide past each other in the slip position, displacing the first clutch member 25 against the spring bias. The use of the clutch in this manner limits the torque applied via the threaded fastener 22, avoids damage that may result from over tightening of the fastener, and also allows the determination of whether the threaded fastener 22 is tightened by the first clutch disengaging from the driven gear to avoid potential safety hazards that may result from the fastener not being tightened.

When loosening the threaded fastener 22, torque is applied in the opposite direction, so that the clutch is arranged to provide a higher torque capacity in the direction tending to release the rotary tool, and this can be achieved by relatively increasing the angle of inclination of the inclined face 35 and the abutment surface 38.

In a second embodiment of the saw 110 of the present invention shown in fig. 5-7, a separate second clutch member 40 may be provided to cooperate with the first clutch member 125 to provide a torque limiting clutch. In the second embodiment, the first clutch member 125 has the same form as the first embodiment, but without the annular channel 30. By abutting the shoulder 50 on the main shaft 114, axial displacement of the first clutch member 125 away from the second clutch member 40 may be limited. The driven gear 119 may include a circular array of nubs 41 projecting from the transverse surface 131, the nubs 41 being received in complementary apertures 42 in the second clutch member 40 such that the second clutch member 40 is fixed for rotation with the driven gear 119.

Referring to fig. 7, the second clutch member 40 is made of a generally annular resilient material (e.g., spring steel) that includes integral circumferentially spaced fingers 43, each finger 43 engaging a respective projection 33 of the first clutch member 25. The second clutch member 40 may include a flat disc portion 44 with the hole 42 disposed in the disc portion 44. Fingers 43 have a similar form, projecting in cantilever fashion from a proximal end 45 to an opposite free distal end 46, and extending circumferentially. The fingers 43 may be equally circumferentially spaced and oriented such that the second clutch member 40 has rotational symmetry with respect to the axis 15. The fingers 43 may be ridged, each finger 43 projecting axially away from the driven gear 119 to one side of the disk portion 44. The ridge 47 of each finger 43 may be generally radially aligned to separate two ramps 136, 137, which may be helically ramped at different angles. Fingers 43 may be formed of a thin material (e.g., a material similar to disk portion 44) and may have substantially the same cross-section throughout their length. The gap 49 adjacent the distal end 46 of each finger 43 accommodates the circumferential elongation of the fingers 43 during bending. The fingers 43 may be rectangular in cross-section, with a width substantially greater than their thickness, thereby advantageously providing the second clutch member 40 with a small axial dimension.

As in the first embodiment, the main shaft 114 is fixed to the driven gear 119 by press-fitting, and passes through the center of the first clutch member 125 in sliding fit. The second clutch member 40 is axially disposed between the driven gear 119 and the first clutch member 125, with the shoulder 50 preventing axial movement of the first clutch member 125 away from the second clutch member 40. Until the torque limit of the clutch, the ramp surface 136 engages the ramped surface 34, preventing the main shaft 114 from rotating (by the torque applied to the main shaft by tightening the fastener 22), with the lock 28 engaged to prevent rotation of the first clutch member 125. At the torque limit, the fingers 43 are biased to flex and pass over the projections 33 and there is relative slippage between the clutch members 125, 40, limiting the maximum torque that can be applied to the threaded fastener 22.

A third embodiment of the saw 210 of the present invention is shown in fig. 8-11 and illustrates an alternative wherein the fingers 243 project radially (rather than axially) and the second clutch member 240 is fixed directly to the main shaft 214 (rather than being connected through a driven gear), such as by press fitting.

The second clutch member 240 is also made of a generally annular form of resilient material including integral circumferentially spaced fingers 243, the fingers 243 having a similar form, projecting in a cantilevered manner from a proximal end 245 to an opposite free distal end 246 and extending circumferentially. The fingers 243 may be equally circumferentially spaced and oriented such that the second clutch member 240 has rotational symmetry with respect to the axis 15. The fingers 243 may be ridged, each protruding radially outward from the cylindrical portion 244. The ridge 247 of each finger 243 may be generally axially aligned to separate the two inclined surfaces 236, 237, which inclined surfaces 236, 237 may be inclined at different angles relative to an axial tangent plane. The fingers 243 may be formed of a thin material and may have substantially the same cross-section throughout their length. Gaps 249 adjacent the distal ends 246 of each finger 43 accommodate circumferential elongation of the fingers 243 during flexing. The fingers 243 may be rectangular in cross-section, with a width substantially greater than a thickness thereof, thereby advantageously providing a smaller radial dimension for the second clutch member 40.

The main shaft 214 passes through the center of the second clutch member 240 and may be press fit fixed. A second clutch member 240 is disposed radially between the main shaft 214 and the first clutch member 225, and in the profiled opening 52, a cavity 53 recessed from the cylindrical surface 48 receives each finger 240. Inclined surfaces 234, 235 are provided in each cavity 53 in the first clutch member 225.

Until the torque limit of the clutch, with the lock 28 engaged to prevent rotation of the first clutch member 225, the ramp 236 engages the ramp surface 234, thereby preventing rotation of the spindle 214 (by the torque applied to the spindle 214 by tightening the fastener 22). At the torque limit, the fingers 243 are biased to flex and slide out of the cavity 53 and there is relative slippage between the clutch members 225, 240, thereby limiting the maximum torque that can be applied to the threaded fastener 22.

As shown in fig. 12 and 13 for the fourth embodiment of the saw 310, the clutch may include a pawl 60 secured in the spindle 314 and a pawl receiving cavity 61 disposed in the first clutch member 325 to limit the torque that may be applied to the fastener 22 during tightening. The main shaft 314 includes a circumferential surface 63 and the first clutch member 325 has a complementary opening with a surface 64 extending around the circumferential surface 63, the surface 64 defining an interface between the circumferential surfaces that provides a running fit. Each pawl 60 may include a recess 66 that retains a pawl member 67 and a compression spring 68 that provides a spring force and urges the pawl member 67 across the interface. The recess 66 may extend radially and the detent member 67 may have a hemispherical tip 69 received in the cavity 61 in the surface 64. The asymmetrical shape of the cavity 61 ensures a relatively low slip torque when tightening the threaded fastener 22 and a relatively high torque when turning in the opposite direction to loosen the threaded fastener 22.

Instead of arranging the pawls in the main shaft or the first clutch member, the pawls may also be arranged in a separate sleeve 70, as shown in the embodiment of fig. 14. The sleeve 70 may receive the main shaft 414 in an interference fit, thereby being fixed for rotation with the main shaft 414, and may be received in a slip fit in a complementary opening 464 in the first clutch member 425. Each pawl 460 may include a recess 466 having a rectangular cross-section, the recess 466 holding a pawl member 467 in the form of a generally rectangular prism, and a compression spring 468 providing a spring force and urging the pawl member 467 past the interface. The notch 466 may extend radially and the pawl member 467 may have a cylindrical tip 469 that is received in a cavity 461 in a surface of the opening 464.

Aspects of the invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the invention.

Claims (19)

1. A rotary power tool, characterized by comprising:

a housing;

a spindle supported in the housing for rotation about an axis;

a thread extending about the axis;

a threaded fastener engageable with the threads for clamping a rotary tool to the spindle;

a first clutch member;

a lock actuatable to prevent rotation of the first clutch member relative to the housing, an

A first torque transfer feature fixed for rotation with one of the main shaft and the first clutch member, the first torque transfer feature being engaged with a second torque transfer feature under spring force to transfer torque from the main shaft to the first clutch member, and the first torque transfer feature being disengaged from the second torque transfer feature by the mating surfaces of the first and second torque transfer features moving to a slip position when a predetermined torque is exceeded.

2. The rotary power tool of claim 1, wherein the first clutch member is annular and includes:

a central bore through which the spindle extends; and

a circumferential periphery with a groove formed therein for receiving the lock to prevent rotation of the first clutch member relative to the housing.

3. The rotary power tool of claim 2, wherein the grooves are equally angularly spaced.

4. The rotary power tool of claim 1, wherein the mating surfaces are configured such that the magnitude of the predetermined torque varies according to its direction, and

a relatively low torque when applied by the threaded fastener in a direction tending to clamp the rotary tool; and

there is a relatively high torque when applied by the threaded fastener in a direction tending to release the rotary tool.

5. The rotary power tool of any one of claims 1 to 4, wherein the rotary power tool comprises:

a compression spring, and

a pair of drive gears and a driven gear that mesh with each other, the drive gears being rotated by a motor, the driven gear being fixed to or formed integrally with the main shaft, and wherein the first clutch member is disposed adjacent to the driven gear such that respective lateral sides of the driven gear and the first clutch member are opposed, and

the first torque transfer feature includes an inclined surface on the lateral side of the driven gear,

the second torque transfer feature includes a ramp on the first clutch member, an

The compression spring extends around the main shaft and has opposite ends that abut the first clutch member and a shoulder on the main shaft to urge the lateral sides together and provide the spring force.

6. The rotary power tool of claim 5, wherein one of the inclined surface and the ramped surface is formed on an arcuate projection of one of the lateral sides and the other of the inclined surface and the ramped surface is formed on a complementary recess of the other of the lateral sides.

7. The rotary power tool of claim 6, wherein the inclined surface and the ramped surface are on respective spirals.

8. The rotary power tool of any one of claims 1 to 4, wherein the rotary power tool comprises:

a second clutch member fixed for rotation with the spindle, wherein the second clutch member is made of a resilient material in a generally annular form including integral circumferentially spaced fingers, and,

the first torque transfer feature comprises an angled face of the finger,

the second torque transfer feature includes a ramp on the first clutch member, an

The bending elasticity of the fingers provides the spring force.

9. The rotary power tool of claim 8, wherein the fingers have a similar form extending longitudinally in cantilever fashion from a proximal end to an opposite free distal end, and the second clutch member has rotational symmetry about the axis.

10. The rotary power tool of claim 9, wherein the fingers have substantially the same cross-section throughout their length and the width of the fingers is greater than their thickness.

11. The rotary power tool of claim 9, wherein the fingers are ridged, each of the fingers has a generally radially aligned ridge, and the ramps are circumferentially spaced, and the ramps axially project from a lateral side of the second clutch member opposite the lateral side of the first clutch member.

12. The rotary power tool of claim 8, wherein the second clutch member includes a flat disk portion, and each of the fingers projects axially to one side of the disk portion.

13. The rotary power tool of claim 9, including a pair of intermeshing drive gears rotated by a motor and a driven gear fixed on or integral with the spindle, and wherein the first clutch member and the driven gear are spaced apart from one another and the second clutch member is between the first clutch member and the driven gear.

14. The rotary power tool of claim 8, wherein the fingers are ridged, each of the fingers has a ridge that is generally radially aligned, and the ramps are circumferentially spaced, and the ramps axially project from a circumference of the second clutch member opposite an inner or outer circumferential surface of the first clutch member.

15. The rotary power tool of claim 14, wherein the second clutch member includes an annular collar portion through which the spindle extends and from which each of the fingers projects radially, and the annular collar portion is disposed in an axially extending opening through the first clutch member.

16. The rotary power tool of any one of claims 1 to 4, wherein the first torque transmission feature comprises a pawl and the second torque transmission feature comprises a cavity that receives the pawl.

17. The rotary power tool of claim 16, wherein the pawl is fixed in one of the spindle and the first clutch member and the cavity is provided in the other of the spindle and the first clutch member.

18. The rotary power tool of claim 16, wherein the spindle includes a circumferential surface and the first clutch member has a complementary surface extending around the circumferential surface, an interface being defined between the circumferential surface and the complementary surface; each of the pawls includes a recess that retains a pawl member and a compression spring that provides the spring force and urges the pawl member beyond the interface.

19. The rotary power tool of claim 16, further comprising:

a sleeve secured about the spindle; and is

The pawl is fixed in one of the sleeve and the first clutch member, and the cavity is disposed in the other of the sleeve and the first clutch member.

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