Handheld power tool with kickback detection and method for detecting a kickback condition in a handheld power tool

Abstract

Disclosed herein is a hand-held power tool with kickback detection and a method for detecting a kickback condition on the hand-held power tool. The method includes moving an implement of the hand-held power tool in an implement plane of motion and detecting the motion of the hand-held power tool. The method also includes determining the presence of a kickback condition based at least in part on the motion of the hand-held power tool. In some embodiments, the hand-held power tool is a circular saw including a user-actuated assembly. The user-actuated assembly includes a motion sensor, a controller, and a motor. The circular saw also includes a workpiece support and a pivot. The motion sensor is configured to detect acceleration along an acceleration detection axis extending at a threshold pivot axis-acceleration axis distance of up to 4 cm from a pivot axis of the pivot.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to hand-held power tools with kickback detection and / or methods for detecting a kickback condition on a hand-held power tool. [Background technology]

[0002] Under certain operating conditions, power tools such as circular saws may behave unpredictably, such as accelerating suddenly and / or undesirably. Such behavior may be referred to herein as a "kickback condition" of the power tool. As an example, when a circular saw is used to cut a workpiece, the workpiece may extend on both sides of the circular saw blade. If the workpiece is allowed to engage and / or pinch the sides of the circular saw blade, friction between the sides of the circular saw blade and the workpiece may provide the driving force for the kickback of the circular saw. As another example, if the circular saw blade cuts unexpectedly deep into the workpiece or penetrates an abnormally hard or soft workpiece area, a change in the force acting on the circular saw may manifest a kickback condition.

[0003] Mechanisms have been developed to detect and respond to kickback conditions, although these mechanisms may be limited to a particular type or class of power tool. As an example, detecting a kickback condition in a stationary power tool, which is generally not moved by the user during operation, may be simpler than detecting a corresponding kickback condition in a handheld power tool, which may experience a variety of different movements during its operation. Thus, there is a need for improved handheld power tools with kickback detection and / or methods of detecting a kickback condition in a handheld power tool. Summary of the Invention

[0004] Disclosed herein are hand-held power tools with kickback detection and methods for detecting a kickback condition on the hand-held power tool. In some embodiments, the methods include moving a tool of the hand-held power tool in a tool motion plane, detecting the motion of the hand-held power tool, and applying a refutation parameter. The methods also include determining the presence of a kickback condition based at least in part on the motion of the hand-held power tool as a verification parameter and the refutation parameter. This aims to identify a kickback condition on the hand-held power tool by the verification parameter that determines a possible kickback condition and the refutation parameter that determines whether the possible kickback condition is a (real) kickback condition. In this way, the verification parameter can be a necessary condition for detecting a kickback condition and the refutation parameter can be a sufficient condition for detecting a kickback condition. The refutation parameter can be or be based on a specific subset of parameter values ​​of the verification parameter.

[0005] Thus, multiple particular handheld power tools, i.e., circular saws, may utilize the same or different refutation parameters, analyses, and / or constraints. The refutation parameters may be applied to determine if a kickback determined by the verification parameters is not a genuine kickback. Providing the refutation parameters allows for increased sensitivity of the verification parameters in determining if a kickback is genuine. In this way, kickback detection is more sensitive to genuine kickbacks, while being less susceptible to false or misidentified kickbacks.

[0006] In some embodiments, the method includes rotating a circular saw blade of a circular saw in a plane of rotation of the blade and detecting movement of the circular saw. The motion detection may include detection in an acceleration detection plane parallel to and / or the same as the plane of rotation of the blade. The motion detection may additionally or alternatively include detecting a direction of acceleration of the circular saw in the acceleration detection plane. The motion detection may additionally or alternatively include detecting an angular velocity of the circular saw about at least one rotation detection axis extending in the acceleration detection plane. The method further includes determining that a kickback condition exists based at least in part on the motion of the circular saw. Determining that a kickback condition exists may include determining when a magnitude of acceleration of the circular saw is greater than a threshold acceleration, when a direction of acceleration of the circular saw is within a threshold direction range, and / or when an angular velocity of the circular saw is greater than a threshold angular velocity.

[0007] The handheld power tool includes a circular saw with a user-actuated assembly. The user-actuated assembly includes a motion sensor, a controller, and a motor. The motion sensor is configured to detect motion of the user-actuated assembly and generate a motion signal indicative of the motion of the user-actuated assembly. The controller is programmed to control operation of the circular saw based at least in part on the motion signal. The motor includes a motor shaft configured to rotate about a shaft rotation axis. The circular saw also includes a workpiece support configured to relatively position the workpiece and the circular saw when the workpiece is cut with the circular saw. The circular saw further includes a pivot. The user-actuated assembly is pivotally coupled to the workpiece support via the pivot, and the user-actuated assembly and the workpiece support are configured to operatively rotate relative to one another about a pivot axis of the pivot. The motion sensor is configured to detect acceleration along an acceleration detection axis extending at a threshold pivot axis-acceleration axis distance of up to 4 cm from the pivot axis. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an embodiment of a circular saw according to the present disclosure; [Diagram 2]2 is another schematic diagram of an embodiment of a circular saw according to the present disclosure. [Diagram 3] FIG. 2 is a schematic diagram of an example handheld circular saw in an untucked orientation according to the present disclosure. [Figure 4] 4 is a schematic diagram of the example handheld circular saw of FIG. 3 in a pushed-in orientation. [Diagram 5] 5 is a plot showing acceleration measured by a motion sensor relatively close to the pivot of the circular saw of FIGS. 3-4. [Figure 6] 5 is a plot showing acceleration measured by a motion sensor relatively distal from the pivot of the circular saw of FIGS. 3-4. [Figure 7] 1 is a schematic diagram of a kickback of a circular saw according to the present disclosure; [Figure 8] 8 is a plot showing acceleration measured during kickback by a motion sensor relatively close to the trailing edge of the circular saw of FIG. 7; [Figure 9] 8 is a plot showing acceleration measured during kickback by a motion sensor relatively distal from the trailing edge of the circular saw of FIG. 7; [Figure 10] 1 is a schematic diagram of an example of a circular saw including a motion sensor having an acceleration detection axis extending through a pivot axis in accordance with the present disclosure. [Figure 11] 1 is a schematic diagram of an example of a circular saw including a circuit board according to the present disclosure. [Figure 12] 1 is a schematic diagram of an example circular saw in an unretracted orientation including a pivot proximate a front edge of the circular saw according to the present disclosure. [Figure 13] FIG. 13 is a schematic diagram of the circular saw of FIG. 12 in a pushed-in orientation. [Figure 14] 4 is a flow chart illustrating an example method for detecting a kickback condition in a circular saw according to the present disclosure. [Figure 15] 1A-1C show examples of magnitudes of acceleration of a circular saw that can be detected using circular saws and / or methods according to the present disclosure. [Figure 16] 1A-1C show examples of the direction of acceleration of a circular saw that can be detected using circular saws and / or methods according to the present disclosure. [Figure 17]1A-1C show examples of angular velocities of a circular saw that can be detected using circular saws and / or methods according to the present disclosure. [Figure 18] 1A-1C show examples of angular velocities of a circular saw blade that can be detected using circular saws and / or methods according to the present disclosure. [Figure 19] 1A-1C show examples of power consumption of a circular saw motor that can be detected using circular saws and / or methods according to the present disclosure. [Figure 20] 1A-1C show examples of linear acceleration components that may be detected and / or utilized as refutation evidence using circular saws and / or methods according to the present disclosure. [Figure 21] 1A-1C show examples of angular velocity components that can be detected and / or used as refutation evidence using circular saws and / or methods according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 1-21 provide examples of handheld power tools 8, such as a circular saw 10, components and / or features of the circular saw 10, parameters measured during operation of the circular saw 10, and / or methods 300 according to the present disclosure. In each of FIGS. 1-21, elements that serve similar or at least substantially similar purposes are numbered the same, and these elements may not be described in detail herein with respect to each of FIGS. 1-21. Similarly, not all elements may be labeled in each of FIGS. 1-21, but reference numbers thereto may be used consistently herein. Elements, components and / or features discussed herein with respect to one or more of FIGS. 1-21 may be included and / or utilized in any of FIGS. 1-21 without departing from the scope of the present disclosure. In general, elements that may be included in a particular embodiment are indicated with solid lines, and optional elements are indicated with dashed lines. However, elements indicated with solid lines are not required for all embodiments, and may be omitted in some embodiments without departing from the scope of the present disclosure.

[0010] 1-4, 7, and 10-13 are schematic diagrams of examples of hand-held power tools 8 according to the present disclosure. For simplicity, the hand-held power tools 8 are shown as circular saws 10 in FIGS. 1-4, 7, and 10-13. However, it is within the scope of the present disclosure that the components, features, and / or methods disclosed herein may be included in and / or utilized with other types of hand-held power tools 8, as described in more detail herein. Examples of such hand-held power tools 8 include rotary hand-held power tools that rotate an implement relative to a workpiece. Examples of such rotary hand-held power tools include rotary cutters, sanders, grinders, and / or drills. Examples of implements of such rotary hand-held power tools include cutting bits, mills, sanding pads, grinding wheels, and / or drill bits.

[0011] As shown collectively in Figures 1-4, 7 and 10-13, and with particular reference to Figures 1-2, the circular saw 10 includes a workpiece support 40 and a pivot 50. The circular saw 10 also includes a user-actuated assembly 100, which may be configured to rotate about the pivot 50 relative to the workpiece support 40 and / or cut the workpiece when the circular saw is in use. The workpiece support 40 may be configured to position the workpiece 90 and the circular saw relative to one another, support the remainder of the circular saw relative to the workpiece, support the workpiece relative to the circular saw, and / or position the workpiece relative to the user-actuated assembly 100 when the workpiece is cut by the circular saw. The workpiece support 40 may include and / or define an assembly-facing side 42 that faces the user-actuated assembly 100 and / or an assembly-facing side 44 that faces away from the user-actuated assembly. The assembly-facing side 42 may also be referred to herein as the user-actuated assembly-facing side 42.

[0012] In some examples of the circular saw 10, such as when the circular saw 10 includes a miter saw, a radial arm saw, a chop saw, and / or a bevel saw, when the circular saw is used to cut a workpiece 90, the workpiece may be placed on and / or supported by the assembly facing surface 42. In some examples of the circular saw 10, such as when the circular saw 10 includes a plunge saw and / or a track saw, when the circular saw is used to cut a workpiece 90, the workpiece may be placed on and / or supported by the assembly facing surface 44 via a workpiece support.

[0013] A user-actuated assembly 100 may be pivotally coupled to the workpiece support 40 via a pivot 50. Additionally, the user-actuated assembly 100 and the workpiece support 40 may be configured to operatively rotate, pivot and / or pivot relative to one another about a pivot axis 52 of the pivot 50. This rotation is illustrated by the transition between Figures 1 and 2.

[0014] In some examples, this rotation can be used to selectively engage the circular saw blade 170 of the user-actuated assembly 100 with the workpiece 90, such as to cut the workpiece with the rotating circular saw blade. By way of example, as shown by the transition between Figures 1 and 2, this rotation can be used to selectively vary the area of ​​the circular saw blade that extends on the opposite assembly surface 44 of the workpiece support 40, the extent to which the circular saw blade extends on the opposite assembly surface of the workpiece, and / or the cutting depth of the circular saw blade.

[0015] In some examples, such as when the circular saw 10 includes a handheld circular saw configured to be held by a user when utilized to cut a workpiece, the circular saw may have and / or define a leading region 22 and a trailing region 26. The leading region 22 may be configured to lead, be in front of, and / or initiate contact with the workpiece when the circular saw is utilized to cut a workpiece, such as when the circular saw is driven by a user to cut the workpiece. The trailing region 26 may be configured to follow and / or be behind the leading region when the circular saw is utilized to cut the workpiece.

[0016] The pivot 50 can be located within and / or adjacent to the leading region 22, as shown by solid lines in Figures 1-2 and 12-13. Alternatively, the pivot 50 can be located within and / or adjacent to the rear end region 26, as shown by dashed lines in Figures 1-2 and 3-4, 7, and 10-11. In other words, the pivot 50 can be within an end of the circular saw 10, such as the leading region 22 or the rear end region 26. In yet other words, the leading region 22 can define the leading edge 24, the rear end region 26 can define the rear edge 28, and the pivot axis 52 can be within a threshold edge distance of the leading edge or the rear edge. Examples of threshold edge distances include distances of at least 1 millimeter (mm), at least 5 mm, at least 1 centimeter (cm), at least 2 cm, at least 4 cm, at most 10 cm, at most 8 cm, at most 6 cm and / or at most 4 cm.

[0017] The user-actuated assembly 100 includes a motion sensor 110 and may include a controller 120. The motion sensor 110 is configurable to detect movement of the user-actuated assembly and / or generate a motion signal 112 that may be indicative of movement of the user-actuated assembly. In other words, as described in more detail herein, the motion sensor 110 is configurable to detect movement of the user-actuated assembly 100 that may be indicative of a kickback condition and / or the onset of a kickback condition in the circular saw. Similar to the pivot 50, the motion sensor 110 may be located in the leading end region 22 and / or the trailing end region 26 of the circular saw.

[0018] As used herein, the phrase "kickback condition" may refer to a condition in which the circular saw or at least a region of the circular saw moves or is forced to move in an unexpected and / or unexpected manner during use of the circular saw to cut a workpiece. Such movement may include unexpected linear, rotational, linear and / or rotational acceleration of the circular saw, which may startle a user of the circular saw and / or damage a workpiece. The circular saws and methods disclosed herein may be configured to detect one or more parameters that may indicate the onset of a kickback condition, or the early stages of a kickback condition, and respond to the detection in a manner that mitigates or reduces the magnitude of the movement of the circular saw. Thus, the circular saws and methods disclosed herein may reduce the likelihood of startling a user of the circular saw and / or damaging a workpiece as a result of a kickback condition.

[0019] The controller 120 is adapted, configured and / or programmable to control operation of the circular saw 10 based at least in part on the movement signal 112. By way of example, and as described in more detail herein, the controller 120 can be programmed to determine when a kickback condition exists or has begun, and to respond to a kickback condition, such as to cushion the impact of the kickback condition, reduce the likelihood of damage to a workpiece as a result of the kickback condition, and / or reduce the likelihood of injury to a user as a result of the kickback condition.

[0020] As shown in dashed lines in Figures 1-2, the user-actuated assembly 100 of the circular saw 10 may include a gripping area 130. If present, the gripping area 130 may be configured to be grasped and / or held by a user of the circular saw during operation of the circular saw to cut a workpiece. In some examples, the gripping area 130 may be within and / or adjacent to the leading end region 22 of the circular saw 10. In some examples, the gripping area 130 may be within and / or adjacent to the trailing end region 26 of the circular saw 10.

[0021] As also shown in dashed lines in FIGS. 1-2, the user actuation assembly 100 of the circular saw 10 may include at least one switch 140. If present, the switch 140 may be configured to be selectively actuated by a user to selectively enable operation of the circular saw, such as to selectively initiate operation of the circular saw, and / or to selectively apply current to at least one other component of the circular saw, such as the controller 120. If present, the switch 140 may be configured to be selectively actuated by a user to selectively initiate operation of the circular saw, selectively enable operation of the circular saw, and / or to selectively apply current to at least one other component of the circular saw, such as the controller 120. As shown, the switch 140 may be in proximity to the gripping area 130 to enable and / or facilitate selective actuation of the switch by a user while the user is gripping the gripping area. Examples of the switch 140 include a trigger switch, a normally open switch, and / or a short throw switch.

[0022] As shown in dashed lines in Figures 1-2, the user-actuated assembly 100 of the circular saw 10 may include a motor 150. If present, the motor 150 may include a motor shaft 152 and / or be configurable to rotate a motor shaft about a shaft axis of rotation 154. Examples of the motor 150 include an electric motor, an AC electric motor, a DC electric motor, a brushless DC electric motor, a variable speed motor, and / or a single speed motor.

[0023] Also, as shown in dashed lines in FIGS. 1-2, the user-actuated assembly 100 of the circular saw 10 can include an arbor 160. The arbor 160, if present, can be operably attached to the motor shaft 152 and / or configured to receive and / or attach the circular saw blade to the motor shaft and / or the user-actuated assembly. Additionally or alternatively, the arbor 160 can be configured to drive, i.e., rotate, the circular saw blade 170 in a blade rotation plane of the circular saw blade. The blade rotation plane can be parallel or at least substantially parallel to the XZ plane of FIGS. 1-2. Examples of the arbor 160 include any suitable clamp, compression mechanism, washer, bushing, spacer, and / or threaded hole that can be operably attached to, defined by, and / or in mechanical communication with the motor shaft 152.

[0024] As shown in dashed lines in FIGS. 1-2, the user-actuated assembly 100 of the circular saw 10 may include and / or be configured to operably receive the circular saw blade 170. If present, the circular saw blade 170 may be operably attached to the circular saw via the arbor 160 and / or may be configured to selectively rotate in a blade rotation plane to cut a workpiece. The circular saw blade 170 generally includes a disk, which may be a metal disk defining a central opening sized to receive the arbor 160, and a cutting edge defined on an outer periphery of the disk. The cutting edge may include a plurality of cutting teeth and / or an abrasive material, by way of example. Examples of the circular saw blade 170 include metal circular saw blades, abrasive circular saw blades, carbide toothed circular saw blades, diamond circular saw blades, rip cut circular saw blades, cross cut circular saw blades, combination circular saw blades, specialty circular saw blades, metal cutting circular saw blades, tile cutting circular saw blades, and / or composite cutting circular saw blades.

[0025] 1-2 show a user-actuated assembly 100 that includes a motion sensor 110 and a controller 120. Figures 1-2 further show the user-actuated assembly 100 optionally including several additional components, such as a gripping area 130, a switch 140, a motor 150, an arbor 160, and / or a circular saw blade 170. To detect movement of the user-actuated assembly, the motion sensor 110 is typically associated with and / or at least indirectly attached to the user-actuated assembly.

[0026] However, it is within the scope of this disclosure that any suitable component or components of the circular saw 10 as disclosed herein may be incorporated into the circular saw in any suitable manner. By way of example, one or more components of the circular saw 10, such as the controller 120, the gripping area 130, the switch 140, the motor 150, the arbor 160, and / or the circular saw blade 170, may be associated with and / or attached to the workpiece support 40 and / or the pivot 50. Additionally or alternatively, one or more components of the circular saw 10 may be indirectly attached to the user-actuated assembly 100, such as via the workpiece support 40 and / or the pivot 50.

[0027] The motion sensor 110 may include any suitable structure that may be adapted, configured, designed, and / or constructed to detect motion of a user-actuated assembly and / or generate a motion signal. By way of example, the motion sensor may include and / or be a Micro-Electro-Mechanical System (MEMS) motion sensor.

[0028] As described, the motion sensor 110 may form part of the user-actuated assembly 100. In other words, the motion sensor 110 may be configured to rotate with the user-actuated assembly 100 about the pivot axis 52 and / or relative to the workpiece support 40. Such an arrangement may enable and / or facilitate measurement, i.e., direct measurement, of the motion of the circular saw 10 that may act on, be experienced by, and / or be accessible to a user of the circular saw. Additionally or alternatively, such an arrangement may also enable and / or facilitate measurement, i.e., direct measurement, of the motion, i.e., translational motion, of the circular saw blade 170.

[0029] However, such a configuration may also present additional challenges, making it more difficult to detect a kickback condition and / or distinguish it from other conditions that may occur during normal or non-kickback operation of the circular saw. As an example, a plunging motion of a circular saw 10 in the form of a plunge saw 20 according to the present disclosure is illustrated by a transition from the configuration shown in FIG. 3 to the configuration shown in FIG. 4. During such a plunging motion or movement, the user-actuated assembly 100 is rotated relative to the workpiece support 40 via the pivot 50 as the plunge saw transitions from an unpushed orientation 30 as shown in FIG. 3 to a pushed orientation 32 as shown in FIG. 4. As illustrated by the plots of FIGS. 5-6, the motion sensor 110 of the user-actuated assembly 100 may experience an acceleration at the beginning of this plunging motion, as shown at 210, and also at the end of the plunging motion, as shown at 212. It may not be desirable for the controller 120 to characterize such predicted acceleration as a kickback condition. Thus, as described in more detail herein, the controller 120 may require that the detected acceleration have a particular magnitude, may require that the detected acceleration have a particular direction, and / or may utilize additional parameters to determine or establish that the detected acceleration of the user-actuated assembly 100 is the result of or corresponds to a kickback condition in the circular saw.

[0030] 1-2, the motion sensor 110 can be configured to detect any suitable motion of the user-actuated assembly 100. By way of example, the motion sensor can be configured to detect acceleration of the user-actuated assembly along a single detection axis 206, which may also be referred to herein as an acceleration detection axis 206, and / or along multiple detection axes 206, such as two perpendicular detection axes 206 or three orthogonal detection axes 206. By way of another example, the motion sensor can be configured to detect rotation of the user-actuated assembly about a single detection axis 206, which may also be referred to herein as a rotation detection axis 206, and / or about multiple detection axes 206, such as two perpendicular detection axes 206 or three orthogonal detection axes 206.

[0031] In some examples, the motion sensor 110 can be configured to detect acceleration of the user-actuated assembly 100 in an acceleration detection plane, or only in the acceleration detection plane. The acceleration detection plane can be perpendicular or at least substantially perpendicular to the shaft rotation axis 154, perpendicular or at least substantially perpendicular to the pivot axis 52, and / or parallel or at least substantially parallel to the blade rotation plane in which the circular saw blade rotates during operation of the circular saw. As a specific example, the acceleration detection plane can be parallel or at least substantially parallel to the XZ plane of FIGS. 1-2.

[0032] In some examples, the motion sensor 110 can be configured to detect rotation of the user-actuated assembly 100 about a detection axis 206 that extends in the acceleration detection plane, or only about the detection axis 206. In other words, the motion sensor 110 can be configured to detect rotation of the user-actuated assembly 100 about the same detection axis 206 of the motion sensor 110 that is utilized to detect acceleration of the user-actuated assembly 100 in the acceleration detection plane.

[0033] The location of the motion sensor 110 on the user-actuated assembly 100 can affect the sensitivity of the motion sensor to various movements of the user-actuated assembly. By way of example, as shown in FIGS. 3-4, if the motion sensor 110 is located relatively closer to the pivot 50 (as shown by the solid line), the sensitivity of the motion sensor to the plunge action of the plunge saw 20 can be relatively less than if the motion sensor is located relatively farther from the pivot 50 (as shown by the dashed line). This is shown by the increased magnitude of acceleration at 210 and 212 in the plot of FIG. 6 compared to the plot of FIG. 5. FIG. 6 illustrates the acceleration measured by the motion sensor 110 shown by the dashed line in FIGS. 3-4 and defining a relatively larger threshold pivot axis-sensor distance 56. In contrast, FIG. 5 illustrates the acceleration measured by the motion sensor 110 shown by the solid line and defining a relatively smaller threshold pivot axis-sensor distance 56.

[0034] As another example, as shown in Figure 7, if the motion sensor 110 is located relatively closer to the trailing edge 28 (i.e., the threshold trailing edge-sensor distance 57 is relatively smaller), the motion sensor may be relatively more sensitive to kickback motion of the circular saw as compared to when the motion sensor is located relatively farther from the trailing edge 28 (i.e., the distance 57 is relatively larger). This kickback motion, shown at 34 in Figure 7, causes the circular saw to move from the dashed orientation to the solid orientation. As shown, the motion sensor 110 that is relatively closer to the trailing edge 28 moves a greater distance 58 as compared to the distance 59 moved by the motion sensor 110 that is relatively farther from the trailing edge.

[0035] Figure 8 illustrates the acceleration measured by a motion sensor 110 relatively closer to the trailing edge 28 (i.e., defining a relatively smaller threshold trailing edge-sensor distance 57) during the kickback motion shown at 34, and Figure 9 illustrates the acceleration measured by a motion sensor 110 relatively farther from the trailing edge 28 (i.e., defining a relatively larger threshold trailing edge-sensor distance 57) during the kickback motion shown at 34. As can be seen, the magnitude of the acceleration signal is significantly greater in Figure 8 compared to Figure 9.

[0036] With this in mind, it may be desirable to position the motion sensor 110 closer to the pivot 50 and / or closer to the trailing edge 28. Such a configuration may reduce the sensitivity of the motion sensor to normal movement of the circular saw and may increase the sensitivity of the motion sensor to kickback conditions. Thus, in some examples, the motion sensor 110 may be positioned a distance 56 away from the pivot axis 52 as shown in Figures 1-4. Examples of distances 56 include distances of at least 1 cm, at least 2 cm, at least 3 cm, at least 4 cm, at least 5 cm, at least 6 cm, at least 7 cm, at least 8 cm, up to 20 cm, up to 18 cm, up to 16 cm, up to 14 cm, up to 12 cm, up to 10 cm, up to 9 cm, up to 8 cm, up to 7 cm, up to 6 cm, up to 5 cm, up to 4 cm, up to 3 cm, up to 2 cm, and / or up to 1 cm.

[0037] In some examples, the motion sensor 110 can be configured to detect acceleration along the acceleration detection axis 206, along a single acceleration detection axis 206, and / or only along the single acceleration detection axis 206. A relatively short distance between the acceleration detection axis 206 and the pivot axis 52 can reduce the sensitivity of the motion sensor 110 to rotation about the pivot axis while still allowing the motion sensor to detect kickback motion of the circular saw. With this in mind, in some examples, the threshold pivot axis-acceleration axis separation distance can be the distance or the shortest distance between the acceleration detection axis 206 and the pivot axis 52. Examples of threshold pivot axis-acceleration axis separation distances include distances of at least 1 mm, at least 2 mm, at least 3 mm, at least 4 mm, at least 5 mm, at least 6 mm, at least 7 mm, at least 8 mm, at least 9 mm, at least 1 cm, at most 4 cm, at most 3 cm, at most 2 cm, at most 1 cm, at most 8 mm, at most 6 mm, at most 4 mm, at most 2 mm, and / or at most 1 mm.

[0038] When the pivot 50 is located relatively closer to the leading edge 24, it may be desirable to locate the motion sensor 110 relatively farther from the pivot 50 and / or relatively closer to the trailing edge 28, as shown in Figures 12-13. Such a configuration may reduce the sensitivity of the motion sensor to normal motion of the circular saw and may increase the sensitivity of the motion sensor to kickback conditions. Thus, in some examples, the motion sensor 110 may be located a distance 56 away from the pivot axis 52, as shown in Figures 1-2. In such examples, the distance 56 may include a distance of at least 5 cm, at least 6 cm, at least 7 cm, at least 8 cm, at most 20 cm, at most 18 cm, at most 16 cm, at most 14 cm, at most 12 cm, at most 10 cm, at most 9 cm, at most 8 cm, at most 7 cm, and / or at most 6 cm.

[0039] In a specific example, although not necessary for all circular saws 10, the motion sensor 110 may be positioned and / or oriented such that the acceleration detection axis 206 may intersect the pivot axis 52, may intersect the pivot 50, may extend through the pivot axis, and / or may extend perpendicular or at least substantially perpendicular to the pivot axis, as shown in Figures 10 and 12-13. In such a configuration, the motion sensor 110 may not detect, or only minimally detect, rotation about the pivot axis 52, thereby further reducing sensitivity to the plunge motion or cut depth setting of the circular saw while still allowing kickback motion detection of the circular saw.

[0040] In some examples, the acceleration sensing axis 206 can extend radially relative to the shaft rotation axis 154 of the motor 150. Such a configuration can increase the sensitivity of the motion sensor 110 to acceleration, i.e., translational acceleration, of the motor shaft 152 and / or the circular saw blade 170.

[0041] 1-2 and 11, the user-actuated assembly 100 may include a circuit board 180 that includes both the controller 120 and the motion sensor 110. Such a configuration reduces costs associated with constructing the circular saw 10 and allows for more economical manufacture of the circular saw. If both the controller 120 and the motion sensor 110 are on the same circuit board 180, space constraints may dictate that the motion sensor be located a finite distance from the pivot axis 52 and / or that the detection axis 206 not intersect the pivot axis 52.

[0042] The controller 120 may include any suitable structure adapted, configured, designed, constructed and / or programmed to control operation of the circular saw based at least in part on the motion signal 112. In some examples, the controller 120 may be programmed to determine that the motion signal 112 is indicative of a kickback condition of the circular saw, as described. In some examples, the controller 120 may be programmed to determine that the motion signal 112 is indicative of a kickback condition when an acceleration axis of the acceleration detected by the motion sensor 110 extends through the pivot axis 52. In some examples, the controller 120 may be programmed to perform any suitable step of the method 300 disclosed herein.

[0043] In some examples, the controller 120 can be further programmed to stop rotation of the circular saw blade in response to determining that a kickback condition exists. By way of example, as shown in FIGS. 1-2, the circular saw 10 can include a brake assembly 80 that can be selectively activated to stop rotation of the circular saw blade. In some such examples, the controller 120 can be programmed to activate the brake assembly 80 in response to a kickback condition and / or in response to determining that a kickback condition exists. As another example, the controller 120 can additionally or alternatively be programmed to stop current supply to the motor 150 or to short or ground a stator coil of the motor 150 in response to a kickback condition and / or in response to determining that a kickback condition exists.

[0044] Controller 120 may include and / or be any suitable structure and / or device that can be adapted, configured, designed, constructed, and / or programmed to perform the functions described herein. By way of example, controller 120 may include one or more of an electronic controller, a dedicated controller, a special purpose controller, a display device, a logic device, a storage device, and / or a storage device having a computer-readable storage medium.

[0045] When present, the computer readable storage medium may also be referred to herein as a non-transitory computer readable storage medium. This non-transitory computer readable storage medium may include, define, contain, and / or store computer executable instructions, programs, and / or codes that may instruct the circular saw 10 and / or its controller 120 to perform any suitable portion or subset of the method 300. Examples of such non-transitory computer readable storage media include CD-ROMs, disks, hard drives, flash memory, and the like. As used herein, storage, i.e., memory, devices, and / or media having computer executable instructions, as well as computer-implemented methods and other methods according to the present disclosure, are believed to be within the scope of subject matter deemed patentable pursuant to 35 U.S.C. 101 (35 U.S.C. 101).

[0046] 1-2, the circular saw 10 may include a biasing mechanism 60. If present, the biasing mechanism 60 may be adapted, configured, designed and / or constructed to bias the user-actuated assembly 100 away from the workpiece support 40 and / or to bias the user-actuated assembly to rotate about the pivot axis 52 in a direction away from the workpiece support. Examples of the biasing mechanism 60 include a resilient member, a spring, a coil spring and / or a torsion spring.

[0047] 1-2 in dashed lines, the circular saw 10 may include a plunge lock 70. If present, the plunge lock 70 may be configured to allow a circular saw user to selectively stop and selectively pivot the user-actuated assembly 100 about the pivot axis 52 and / or toward the workpiece support 40. Examples of the plunge lock 70 include any suitable catch and / or latch.

[0048] The circular saw 10 may include and / or be any suitable circular saw. As an example, the circular saw 10 may include and / or be a handheld circular saw 10 that can be configured to be lifted and / or held by a user when utilizing the circular saw to cut a workpiece. Additionally or alternatively, the handheld circular saw 10 may be referred to as a portable circular saw 10 and / or a non-stationary circular saw 10. As another example, the circular saw 10 may include and / or be a semi-stationary circular saw 10. As used herein, the phrase "semi-stationary circular saw" refers to a circular saw that includes a large, heavy, and / or stationary workpiece support 40 that is configured to remain stationary on a support surface when the circular saw is used to cut a workpiece. However, because the user-actuated assembly 100 is pivotally coupled to the workpiece support 40 via the pivot 50, the user-actuated assembly may still experience kickback conditions that may result in unexpected and / or undesirable rotation of the user-actuated assembly.

[0049] As more specific examples, the circular saw 10 may include a plunge saw, a miter saw, a track saw, a radial arm saw, a chop saw, a sliding miter saw, a bevel saw, and / or a panel saw. If the circular saw 10 includes a track saw, the track saw may further include a track 82 that may be configured to guide the track saw relative to the workpiece 90. If the circular saw 10 includes a radial arm saw, the radial arm saw may further include a support arm 84 that may be configured to guide the radial arm saw relative to the workpiece. If the circular saw 10 includes a panel saw, the panel saw may further include a frame 86 that may be configured to guide and / or orient the panel saw relative to the workpiece. Some circular saws may include a combination of these elements. As an example, a sliding miter saw may include both a pivot 50 and a frame 86, with the user-actuated assembly 100 configured to rotate about a pivot axis 52 of the pivot 50 relative to the workpiece support 40 and translate along the frame 86 relative to the workpiece support 40.

[0050] 14 is a flow chart illustrating an example method 300 for detecting a kickback condition in a hand held power tool, such as a circular saw, in accordance with the present disclosure. Examples of hand held power tools and / or circular saws are disclosed herein with reference to the hand held power tool 8 and / or circular saw 10 of FIGS. 1-4, 7 and 10-13.

[0051] The method 300 may include rotating a circular saw blade at 310 and may include cutting a workpiece at 320. The method 300 may also include detecting movement of the circular saw at 330 and may include detecting a workpiece contact parameter at 340. The method 300 may further include determining the presence of a kickback condition at 350 and may include responding to the determination of the presence of the kickback condition at 360. The method 300 may include determining the presence of a kickback condition at 350 based at least in part on the verification parameters including movement of the hand held power tool and optionally further including the workpiece contact parameter.

[0052] Rotating the circular saw blade at 310 may include rotating the circular saw blade in a blade rotation plane. Examples of blade rotation planes are disclosed herein. This may include rotating the circular saw blade to enable and / or facilitate cutting at 320. Rotating at 310 may be accomplished in any suitable manner. As an example, as described, the circular saw may include a motor including a motor shaft configured to rotate about a shaft rotation axis. As also described, the circular saw may also include an arbor that attaches the circular saw blade to the motor shaft. In some such examples, rotating at 310 may include passing or supplying current to the motor to provide a motive force for rotation about a shaft rotation axis of the motor shaft to rotate the circular saw blade via the arbor. Examples of motors, motor shafts, and shaft rotation axes are disclosed herein with reference to motor 150, motor shaft 152, and shaft rotation axis 154, respectively. Examples of arbors are disclosed herein with reference to arbor 160. Examples of circular saw blades are disclosed herein with reference to circular saw blade 170.

[0053] The rotation at 310 can be performed at any suitable time and / or order during the method 300. By way of example, the rotation at 310 can be performed before, during and / or simultaneously with the disconnection at 320, the detection at 330, the detection at 340, the determination at 350 and / or the response at 360.

[0054] Cutting the workpiece at 320 may include cutting the workpiece with a circular saw blade. Cutting at 320 may be accomplished in any suitable manner. By way of example, cutting at 320 may include operatively engaging a circular saw blade, i.e., a plurality of teeth of the circular saw blade, with the workpiece to form and / or define a cut, slit, and / or kerf in the workpiece. Cutting at 320 may additionally or alternatively include translating and / or rotating the circular saw relative to the workpiece to widen the cut, slit, and / or kerf.

[0055] In some examples, the cutting at 320 may further include establishing a kickback condition. In other words, a kickback condition may occur during the cutting at 320. As one example, the circular saw blade may catch on and / or be pinched by the workpiece, causing a kickback motion of the circular saw during a kickback condition. As another example, the circular saw blade may cut into an abnormally hard or soft area of ​​the workpiece and / or catch on an area of ​​the workpiece, causing a kickback motion of the circular saw during a kickback condition.

[0056] The disconnection at 320 can occur at any suitable time and / or order during method 300. As one example, the disconnection at 320 can occur following the initiation of rotation at 310 and / or simultaneously with the rotation at 310. As a further example, the disconnection at 320 can occur before, during, and / or simultaneously with the detection at 330, the detection at 340, the determination at 350, and / or the response at 360.

[0057] The detection of the movement of the circular saw at 330 may include detection of any suitable movement of the circular saw that may be indicative of a kickback condition and / or may be utilized to predict a kickback condition. The detection at 330 may be performed using any suitable timing and / or order during the method 300. As an example, the detection at 330 may be performed after, after initiation of, during, and / or simultaneously with the turning at 310 and / or cutting at 320. As another example, the detection at 330 may be performed simultaneously with the detection at 340. As a further example, the detection at 330 may be performed prior to the determination at 350 and / or prior to the response at 360. Additionally or alternatively, the determination at 350 and / or the response at 360 may be based on and / or at least partially responsive to the detection at 330.

[0058] In some examples, the detecting at 330 may include detecting a magnitude of acceleration as shown at 332. The detecting at 332 may include detecting a magnitude of acceleration of the circular saw and / or at least one component of the circular saw, such as the user-actuated assembly 100 described in more detail herein. In some examples, the detecting at 332 may include detecting in an acceleration detection plane. The acceleration detection plane may be parallel or at least substantially parallel to the plane of rotation of the blade and / or may be coplanar with the plane of rotation of the blade. Examples of acceleration detection planes are described herein.

[0059] The detecting at 332 may include detecting the magnitude of the acceleration in any suitable manner. As an example, as described, the circular saw may include a motion sensor, such as the motion sensor 110 disclosed herein. In such a configuration, the detecting at 332 may include detecting by, through, and / or utilizing the motion sensor.

[0060] In some examples, the sensing at 332 can include sensing a first acceleration component in a first direction that is in the acceleration sensing plane, and also sensing an acceleration component in a second direction that is in the acceleration sensing plane and that can be a direction different from the first direction or even perpendicular to the first direction. In some such examples, the magnitude of the acceleration is the magnitude of a vector sum of the first acceleration component and the second acceleration component.

[0061] An example of the magnitude of the acceleration of a circular saw, both as a time plot and a schematic diagram, is shown in Figure 15. As shown in the time plot of Figure 15, the magnitude of the acceleration of the circular saw may increase significantly as a result of and / or during a kickback condition, as indicated at 220. Thus, the magnitude of the acceleration of the circular saw may be indicative of a kickback condition and / or may be used to at least partially establish that a kickback condition exists.

[0062] As shown in the schematic circular saw 10 of FIG. 15, detection at 332 is x and detecting a first acceleration component such as the acceleration component a z and detecting a second acceleration component such as: In such an arrangement, the magnitude of the acceleration m can be determined by a vector sum of the first acceleration component and the second acceleration component.

[0063] In some examples, the detecting at 330 can include detecting a direction of acceleration, as shown at 334. The detecting at 334 can include detecting a direction of acceleration of the circular saw 10 and / or the user-actuated assembly 100. In some examples, the detecting at 334 can include detecting in an acceleration detection plane.

[0064] The detecting at 334 may include detecting the direction of acceleration in any suitable manner. As an example, as described, the circular saw may include a motion sensor, such as the motion sensor 110 disclosed herein. In such a configuration, the detecting at 334 may include detecting by, through and / or using the motion sensor.

[0065] In some examples, the detecting at 334 can include detecting a first acceleration component in a first direction that is in the acceleration detection plane and detecting a second acceleration component in a second direction that is also in the acceleration detection plane and can be a different direction than the first direction or even a direction perpendicular to the first direction. In some such examples, the direction of the acceleration can be the orientation and / or direction of a vector sum of the first acceleration component and the second acceleration component.

[0066] An example of the magnitude of the circular saw direction, angle or vector orientation is shown in both a time plot and a schematic diagram in Figure 16. As shown in the plot of Figure 16, the direction of the circular saw acceleration can change significantly as a result of and / or during a kickback condition, as indicated at 220. Thus, the direction of the circular saw acceleration can be indicative of a kickback condition and / or can be used to at least partially establish that a kickback condition exists.

[0067] As shown in the schematic circular saw 10 of FIG. 16, detection at 334 is x and detecting a first acceleration component such as the acceleration component a z and detecting a second acceleration component such as: In such an arrangement, the direction of acceleration, such as may be established by angle 222, may be determined via and / or from the first and second acceleration components, as shown in FIG.

[0068] The detection of angular velocity at 336 can include detection of an angular velocity of the circular saw 10 and / or the user-actuated assembly 100. In some examples, the detection at 336 can include detection of angular velocity about and / or about one or more detection axes extending in an acceleration detection plane.

[0069] The detection at 336 may include detecting angular velocity in any suitable manner. As an example, as described, the circular saw may include a motion sensor, such as the motion sensor 110 disclosed herein. In such a configuration, the detection at 336 may include detecting by, through, and / or utilizing the motion sensor.

[0070] In some examples, the sensing at 336 can include sensing a first angular velocity component in a first direction that is in the acceleration sensing plane and sensing a second angular velocity component in a second direction that is also in the acceleration sensing plane and that can be a direction different from the first direction or even perpendicular to the first direction. In some such examples, the angular velocity can be a vector sum of the first and second angular velocity components.

[0071] An example of the angular velocity of the circular saw, both as a time plot and as a schematic diagram, is shown in Figure 17. As shown in the plot of Figure 17, the angular velocity of the circular saw can change significantly as a result of and / or during a kickback condition, as indicated at 220. Thus, the angular velocity of the circular saw can be indicative of a kickback condition and / or can be used to at least partially establish that a kickback condition exists.

[0072] As shown in the leftmost schematic circular saw 10 of FIG. 17, detection at 336 determines the angular velocity component w x Detection of the first angular velocity component such as z In such a configuration, the angular velocity may be determined via a vector sum of the first and second angular velocity components, as shown at 224 in the right-most schematic circular saw 10 of FIG.

[0073] As explained, and where handheld power tools include circular saws, hand held circular saws, and / or semi-stationary circular saws, etc., the acceleration and / or rotation of the circular saw that may occur during normal operation of the circular saw and / or when a user moves, repositions, and / or repositions the circular saw may, in certain circumstances, be similar to that experienced during a kickback condition. Thus, for some circular saws, it may also be beneficial to detect one or more additional parameters that can be used to verify that the circular saw is actually being used to cut a workpiece and / or that a kickback condition actually exists.

[0074] With this in mind, the method 300 may further include detecting a workpiece contact parameter at 340. In such an example, the determination at 350 may further be based at least in part on the detection at 340. In other words, a kickback condition may exist only if the circular saw blade is in contact with the workpiece and / or if the workpiece contact parameter indicates that the circular saw blade is in contact with the workpiece. In this manner, contact between the circular saw blade and the workpiece may be utilized within the method 300 as a necessary condition for a kickback condition to exist.

[0075] The detection of the workpiece contact parameter at 340 may include detection of any suitable workpiece contact parameter that may be indicative of contact between the circular saw blade and the workpiece. In other words, if the circular saw blade is in contact with the workpiece, the workpiece contact parameter may be within a contact value range. In contrast, if the circular saw blade is spaced from, or not in contact with, the workpiece contact parameter may be within a non-contact value range that is different from the contact value range. In such a configuration, the determination at 350 may include determining that a kickback condition exists if, or only if, the workpiece contact parameter is within the contact value range. In other words, if the method 300 includes the detection at 340, a workpiece contact parameter having a value within the contact value range may be a prerequisite that must be met prior to or for determining that a kickback condition exists, such as at the time of the determination at 350.

[0076] In some examples, the workpiece contact parameters can include and / or be the angular velocity of the circular saw blade, the revolutions per minute of the circular saw blade, the angular velocity of the motor shaft, and / or the revolutions per minute of the motor shaft during rotation at 310. In such an arrangement, the circular saw blade can define a mean free angular velocity when it is spaced from the workpiece, and the contact value range can include angular velocities below the mean free angular velocity by a threshold angular velocity decrement. Examples of threshold angular velocity reductions include a reduction of at least 20 revolutions per minute (RPM), at least 25 RPM, at least 30 RPM, at least 35 RPM, at least 40 RPM, at least 50 RPM, at least 60 RPM, at least 70 RPM, at least 80 RPM, at least 90 RPM, at least 100 RPM, at least 150 RPM, at least 200 RPM, at least 300 RPM, at least 400 RPM, at least 500 RPM, at least 600 RPM, at least 700 RPM, or at least 800 RPM.

[0077] In other words, contact between the circular saw blade and the workpiece creates a resistance to the rotation of the circular saw blade, which may reduce the angular velocity of the circular saw blade to a value less than the mean free angular velocity of the circular saw blade. Also, as explained, a kickback condition may result from the jamming and / or pinching of the circular saw blade by the workpiece. This jamming and / or pinching may further reduce the angular velocity of the circular saw blade compared to the mean free angular velocity, and this reduction in the angular velocity of the circular saw blade may be used to indicate that the circular saw blade is actually in contact with the workpiece.

[0078] An example of the angular velocity of the circular saw blade as a function of time is shown in Figure 18. As shown, the angular velocity of the circular saw blade may decrease significantly as a result of and / or during a kickback condition, as indicated at 220. Thus, the angular velocity of the circular saw blade may be used to at least partially establish that the circular saw blade is in contact with a workpiece and / or that a kickback condition exists.

[0079] Detecting the angular velocity of the circular saw blade can be accomplished in any suitable manner. As an example, detecting the angular velocity of the circular saw blade can include measuring the angular velocity of the circular saw blade, such as by utilizing a revolution counter of the circular saw. As another example, detecting the angular velocity of the circular saw blade can include calculating the angular velocity of the circular saw blade, for example, based at least in part on a motor model of the circular saw motor. In some such examples, calculating the angular velocity of the circular saw blade can include calculating at least in part on a magnitude of a current supplied to the motor and / or a magnitude of a voltage of the current.

[0080] In some examples, the workpiece contact parameter can include and / or be the power consumption of the circular saw blade when rotating at 310. In such a configuration, the motor can define a maximum rated power consumption and the contact value range can include power consumption greater than a threshold percentage of the maximum rated power consumption. Examples of threshold percentages of the maximum rated power consumption include percentages of 50%, 60%, 70%, 80% or 90%.

[0081] In other words, contact between the circular saw blade and the workpiece creates resistance to rotation of the circular saw blade and can increase the power consumption of the motor. Also, as explained, a kickback condition can occur as a result of the circular saw blade getting stuck and / or pinched by the workpiece. This sticking and / or pinching can further increase the power consumption of the motor, and this increase in power consumption can be used to indicate that the circular saw blade is actually in contact with the workpiece.

[0082] An example of motor power consumption as a function of time is shown in Figure 19. As shown, motor power consumption may increase significantly as a result of and / or during a kickback condition, as indicated at 220. Thus, motor power consumption may be used to at least partially verify that the circular saw blade is in contact with the workpiece and / or that a kickback condition exists.

[0083] Detecting the power consumption of the motor may be accomplished in any suitable manner, and as one example may include calculating the power consumption of the motor based at least in part on the magnitude of the current supplied to the motor and the magnitude of the voltage of the current.

[0084] In some examples, the circular saw can include a contact detector configurable to detect contact between the circular saw blade and the workpiece. In some such examples, the contact detector can be configured to produce and / or generate a workpiece contact parameter. Examples of contact detectors include an electrical contact detector, a capacitive contact detector, an electromagnetic contact detector, and / or a mechanical contact detector.

[0085] The determination at 350 that a kickback condition exists may include determining, establishing, determining, and / or concluding that a kickback condition exists in any suitable manner and / or based on any suitable information, data, and / or parameters. In some examples, the circular saw may include a controller, such as the controller 120 of FIGS. 1-2 and 11. In some such examples, the controller is programmable to perform the determination at 350. This may include determining the presence of a kickback condition based at least in part on movement of the circular saw as detected during detection at 330.

[0086] In some examples, the determination at 350 may include determining that a kickback condition exists if, or only if, the magnitude of the acceleration of the circular saw, as may be determined upon detection at 332, is greater than a threshold acceleration value. An example of a threshold acceleration value is at least 1 meter per second per second (m / s 2 ), at least 2m / s 2 , at least 3m / s 2 , at least 4m / s 2 , at least 6m / s 2 , at least 8m / s 2 , at least 10 m / s 2, at least 12 m / s 2 , at least 14 m / s 2 , at least 16m / s 2 , at least 18 m / s2, or at least 20 m / s 2 Examples of accelerations that are greater than the threshold acceleration value and indicate a kickback condition are indicated by the cross-hatched areas of the plot in FIG.

[0087] In some examples, the determination at 350 may include determining that a kickback condition exists if, or only if, the direction of acceleration of the circular saw is within a threshold direction range, examples of which include a direction rearward relative to the cutting direction of the circular saw, a direction toward the trailing edge 28 of the circular saw, and / or a direction away from a workpiece being cut with the circular saw, as shown in FIG.

[0088] As a more specific example, the workpiece support may define a workpiece-facing surface, a workpiece-reverse surface, a leading edge, and a trailing edge. In some such examples, the threshold directional range may be at least partially perpendicular to the workpiece-facing surface of the workpiece support and / or at least partially toward the trailing edge of the workpiece support. In some such examples, the threshold directional range may be defined within a quadrant extending between a first vector toward the trailing edge of the workpiece support and along the workpiece-facing surface of the workpiece support, and a second vector intersecting the first vector and perpendicular to the workpiece-facing surface of the workpiece support. An example of such a quadrant is shown in FIG. 16 at 226.

[0089] As another more specific example, the threshold direction range may be within a threshold angle range of the cutting direction of a circular saw. Such a threshold angle range may be oriented in a direction away from the user-actuated assembly facing surface of the workpiece and may be shown at 222 in FIG. 16. Examples of threshold angle ranges include angles of at least 80 degrees, at least 90 degrees, at least 100 degrees, at least 110 degrees, at least 120 degrees, at least 130 degrees, at least 140 degrees, at least 150 degrees, at least 160 degrees, up to 200 degrees, up to 180 degrees, up to 170 degrees, up to 160 degrees, up to 150 degrees, up to 140 degrees, up to 130 degrees, up to 120 degrees, up to 110 degrees, and / or up to 100 degrees. The cross-hatched areas in the plot of FIG. 16 indicate examples of threshold direction ranges that are within the threshold angle range.

[0090] In some examples, the determining at 350 may include determining that a kickback condition exists if, or only if, the angular velocity of the circular saw is greater than a threshold angular velocity value. Examples of threshold angular velocity values ​​include at least 1 degree per second (° / s), at least 2° / s, at least 3° / s, at least 4° / s, at least 6° / s, at least 8° / s, or at least 10° / s. Examples of angular velocities greater than the threshold angular velocity value are shown by the cross-hatched areas in the plot of FIG. 17. In some examples, the threshold angular velocity value may include an angular velocity that urges a blade-proximate side of the workpiece support of the circular saw away from the workpiece, as shown in FIG. 17.

[0091] In some examples, the determination at 350 may include applying a refutation parameter, analysis, and / or constraint, or even multiple refutation parameters, analyses, and / or constraints, to the detection at 330 and / or the detection at 340. In such examples, the determination at 350 may be based at least in part on the refutation parameter, analysis, and / or constraints.

[0092] The refutation parameters, analysis, and / or constraints may be selected or based on the configuration, structure, and / or usage of the hand-held power tool or circular saw. As an example, according to the present disclosure, a particular hand-held power tool and / or circular saw may have a different overall configuration, structure, and / or layout and / or may be used differently compared to another hand-held power tool or circular saw. As such, a hand-held power tool and / or circular saw may experience different accelerations and / or rotations compared to other hand-held power tools or circular saws, and different accelerations and / or rotations may be indicative of or a prerequisite for a kickback condition. Thus, a particular hand-held power tool or circular saw may utilize the same or different refutation parameters, analysis, and / or constraints. The refutation parameters may be applied to determine when a kickback determined by the verification parameters is not an actual kickback. The application of the refutation parameters may increase the sensitivity of the verification parameters in determining. Thus, the detection of the kickback may be more sensitive to actual kickbacks while being less susceptible to false reactions to false kickbacks.

[0093] One example of a refutation parameter is a linear acceleration component of the acceleration of the circular saw, as may be determined upon detection at 330. The linear acceleration component may be directed in a particular, defined and / or predetermined linear acceleration direction. In other words, the linear acceleration component may be a particular subset of the overall acceleration of the circular saw, with the particular subset directed in a linear acceleration direction. An example of a linear acceleration component is shown in FIG. 20 and described in more detail herein.

[0094] The linear acceleration direction can include or be equivalent to any suitable specific, defined and / or predetermined linear acceleration direction. As an example, the linear acceleration direction can be parallel, or at least substantially parallel, to a blade rotation plane of the circular saw blade and / or parallel, or at least substantially parallel, to an assembly facing surface of a workpiece support of the circular saw. As another example, the linear acceleration direction can be parallel, or at least substantially parallel, to a longitudinal axis of a kerf defined in a workpiece by the circular saw blade, such as when cutting at 320.

[0095] As a further example, the linear acceleration direction may be within a threshold angular difference of being parallel to the blade rotation plane, parallel to the assembly facing surface of the workpiece support, and / or parallel to the kerf. Examples of the threshold angular difference include an angular difference of up to 1 degree, up to 2 degrees, up to 4 degrees, up to 6 degrees, up to 8 degrees, up to 10 degrees, up to 12 degrees, up to 14 degrees, up to 16 degrees, and / or up to 18 degrees.

[0096] If the determination at 350 involves applying a refutation parameter in the form of a linear acceleration component, the determination at 350 may include determining that a kickback condition exists if or only if the linear acceleration component is outside a threshold linear acceleration component range. In other words, the linear acceleration component may be within the threshold linear acceleration component range during normal operation of the circular saw to cut a workpiece. However, the linear acceleration component may differ from the threshold linear acceleration component range during or before a kickback condition. In further words, the linear acceleration component may be within the threshold linear acceleration component range when a false kickback is detected during normal operation of the circular saw to cut a workpiece. The method 300 is configured not to initiate a response at 360 during such a false kickback condition. In this way, the linear acceleration component being outside the threshold linear acceleration range may be a necessary condition for determining that a kickback condition exists. In other words, the linear acceleration component being within the threshold linear acceleration component range is a necessary condition for determining that a false kickback condition exists and / or that a kickback condition does not exist.

[0097] If the linear acceleration component is outside the threshold linear acceleration component range, the direction of the linear acceleration component may be toward a trailing edge of the circular saw, or if the linear acceleration component is within the threshold linear acceleration component range, the direction of the linear acceleration component may be toward a leading edge of the circular saw.

[0098] The threshold linear acceleration component range may include and / or be any suitable linear acceleration component value. In a coordinate system as shown in FIG. 16 , where positive acceleration values ​​point generally toward the trailing edge 28 and negative acceleration values ​​point generally toward the leading edge 24, linear acceleration component values ​​whose linear acceleration components fall within the threshold linear acceleration component range may have a negative sign (i.e., may point toward the leading edge 24). In such a coordinate system, the upper limit 237 (as shown in FIG. 20 ) of linear acceleration component values ​​falling within the threshold linear acceleration component value range may be up to −1.5 meters / sec 2 . 2 (m / s 2 ), maximum -2m / s2 , up to -2.5m / s 2 , up to -3m / s 2 , up to -3.5m / s 2 , up to -4m / s 2 , up to -4.5m / s 2 , up to -5m / s 2 , up to -5.5m / s 2 , up to -6m / s 2 , at least -10m / s 2 , at least -9.5m / s 2 , at least -9m / s 2 , at least -8.5m / s 2 , at least -8m / s 2 , at least -7.5m / s 2 , at least -7m / s 2 , at least -6.5m / s 2 , at least -6m / s 2 , at least -5.5m / s 2 , at least -5m / s 2 , at least -4.5m / s 2 and / or at least -4m / s 2 Includes linear acceleration values.

[0099] Another example of a refutation parameter is a linear acceleration direction component of the acceleration of the circular saw, as may be determined upon detection at 330. The linear acceleration direction component may point in a specific, defined and / or predetermined linear acceleration direction. In other words, the linear acceleration direction component may be a specific subset of the overall acceleration direction of the circular saw, with the specific subset pointing in a linear acceleration direction.

[0100] The linear acceleration direction may include or be equivalent to any suitable specific, defined and / or predetermined linear acceleration direction. As an example, the linear acceleration direction component may be toward a leading edge of the circular saw or away from a user of the saw. In other words, such a linear acceleration direction component may be toward a user-actuated assembly-facing surface of the workpiece support, as shown at 222 in FIG. 16. In such a coordinate system, linear acceleration direction component values ​​within the threshold linear acceleration direction component range include linear acceleration direction values ​​of at most 80 degrees (°), at most 60°, at most 45°, at least −80°, at least −60°, at least −45°, at least −30°, and / or at least 0°.

[0101] Other examples of refutation parameters include angular velocity components of the angular velocity of the circular saw as measured about an angular velocity axis. The angular velocity axis may include and / or be an axis along which a linear acceleration direction extends, and may also be referred to herein as a linear acceleration axis. In other words, the angular velocity axis may coincide with a linear acceleration direction. In further words, the angular velocity components may include and / or be a particular subset of the total angular velocity of the circular saw as measured about the angular velocity axis. Examples of angular velocity components are shown in FIG. 21 and described in more detail herein.

[0102] If the determination at 350 includes applying a refutation parameter in the form of an angular velocity component, the determination at 350 may determine the presence of a kickback condition if, or only if, the angular velocity is outside the threshold angular velocity component range. In other words, the angular velocity component may be within the threshold angular velocity component range during normal operation of the circular saw to cut a workpiece. However, the angular velocity component may differ from the threshold angular velocity component range during or before a kickback condition. Additionally or alternatively, the angular velocity component may be within the threshold angular velocity component range when a kickback condition does not exist and / or when a false kickback is detected during normal operation of the circular saw to cut a workpiece. In this way, the angular velocity component being outside the threshold angular velocity component range may be a necessary condition for determining that a kickback condition exists. In other words, the angular velocity component being within the threshold angular velocity component range is a necessary condition for determining that a false kickback condition exists.

[0103] If the angular velocity component is within the threshold angular velocity component range, then rotating about the angular velocity axis and / or about the cutting direction includes rotating the arbor of the circular saw and / or the blade of the circular saw towards the workpiece, or if the linear acceleration component is outside the threshold angular velocity component range, then rotating about the angular velocity axis and / or about the cutting direction includes rotating the arbor of the circular saw and / or the blade of the circular saw away from the workpiece.

[0104] The threshold angular velocity component range may include any suitable angular velocity component values. In a coordinate system as shown in FIG. 16 , where positive acceleration values ​​point generally toward the trailing edge 28 and negative acceleration values ​​point generally toward the leading edge 24, angular velocity component values ​​whose angular velocity components fall within the threshold angular velocity component range may have a negative sign for rotation according to the right-hand rule. In such a coordinate system, the upper limits 239 (as shown in FIG. 21 ) of angular velocity component values ​​that fall within the range of threshold angular velocity component values ​​may be at most −1.5 degrees per second (° / s), at most −2° / s, at most −2.5° / s, at most −3° / s, at most −3.5° / s, at most −4° / s, at most −4.5° / s, at most −5° / s, at most −5.5° / s, at most −6° / s, at most −6.5° / s, at most −7° / s, at most −7.5° / s, at most −8° / s, at least −12° / s, at least −14° / s, at least −16° / s, at least −18 ... including angular velocities of -11.5° / s, at least -11° / s, at least -10.5° / s, at least -10° / s, at least -9.5° / s, at least -9° / s, at least -8.5° / s, at least -8° / s, at least -7.5° / s, at least -7° / s, at least -6.5° / s, at least -6° / s, at least -5.5° / s, at least -5° / s, at least -4.5° / s and / or at least -4° / s.

[0105] In some examples, the refutation parameters, such as linear acceleration components and / or angular velocity components, can be determined and / or detected within a detection time window. If a detection time window is used, the detection time window can extend a threshold detection time before a kickback time of the hand-held power tool. The kickback time can include and / or be a time during which the magnitude of the acceleration of the hand-held power tool is greater than a threshold acceleration value, the direction of the acceleration of the hand-held power tool is within a threshold direction range, and / or the angular velocity of the hand-held power tool is greater than a threshold angular velocity value. The detection time window can have a duration that can be determined by the threshold detection time before the kickback time. Example durations include durations of at least 20 milliseconds (ms), at least 30 ms, at least 40 ms, at least 50 ms, at least 60 ms, at least 70 ms, at least 80 ms, at least 90 ms, at least 100 ms, at least 110 ms, at least 120 ms, at least 130 ms, at least 140 ms, up to 220 ms, up to 210 ms, up to 200 ms, up to 190 ms, up to 180 ms, up to 170 ms, up to 160 ms, up to 150 ms, up to 140 ms, up to 130 ms, up to 120 ms, up to 110 ms, and / or up to 100 ms.

[0106] As explained, the refutation parameters may be used or adapted based on the configuration of the hand held power tool or circular saw. Examples of refutation parameters determined from a hand held circular saw are shown in Figures 20-21. Figure 20 shows the refutation parameters in the form of linear acceleration components of the hand held circular saw, and Figure 21 shows the refutation parameters in the form of angular velocity components of the hand held circular saw.

[0107] 20-21 show examples of refutation parameters (i.e., linear acceleration components in FIG. 20 and angular velocity components in FIG. 21) that can be used to distinguish between actual and false kickback indications at kickback time 220, as described herein. In FIGS. 20-21, kickback time (i.e., the onset of a kickback condition as indicated by the magnitude of the acceleration of the circular saw being greater than a threshold acceleration value, the direction of the acceleration of the circular saw being within a threshold direction range, and the angular velocity of the circular saw being greater than a threshold angular velocity value) is shown at 220. However, as described in more detail herein, a hand held circular saw does not necessarily experience a kickback at kickback time 220. In FIGS. 20-21, an example of normal operation of a hand held circular saw during a chop cut (i.e., no kickback) is shown by line 230, while two examples of actual kickback of the hand held circular saw are shown by line 232. A detection time window is also shown in FIGS. 20-21 at 234.

[0108] In Fig. 20, negative linear acceleration component values ​​point away from the user of the handheld circular saw and / or in the direction of the cut (e.g., toward the leading edge of the saw), while positive linear acceleration component values ​​point toward the user of the handheld circular saw and / or against the direction of the cut (e.g., toward the trailing edge of the handheld circular saw). As shown in Fig. 20, during normal operation of the handheld circular saw (as shown at 230), the linear acceleration component is within a threshold linear acceleration component range 236 during at least a subset of a detection time window 234. However, as also shown in Fig. 20, when a kickback of the handheld circular saw (as shown at 232) occurs, the linear acceleration component is outside of the threshold linear acceleration component range 236 for the entire detection time window. Thus, the linear acceleration component can be indicative of or can be used to detect actual and / or false kickback of the handheld circular saw.

[0109] In Fig. 21, negative angular velocity values ​​rotate the arbor of the handheld circular saw towards the workpiece (i.e., the circular saw or the user-actuated assembly of the circular saw is rotated clockwise as viewed in the direction of the cut) and positive angular velocity values ​​rotate the arbor of the handheld circular saw away from the workpiece (i.e., the circular saw or the user-actuated assembly of the circular saw is rotated counterclockwise as viewed in the direction of the cut). As shown in Fig. 21, during normal operation of the handheld circular saw making a chop cut (as shown at 230), the angular velocity component is within the threshold angular velocity component range 238 during at least a subset of the detection time window 234. However, as also shown in Fig. 21, during a kickback of the circular saw (as shown at 232), the angular velocity component is outside the threshold angular velocity component range 238 for the entire detection time window. Thus, the angular velocity component can be indicative of or can be used to detect actual and / or false kickback of the handheld circular saw.

[0110] The response at 360 to the determination that a kickback condition exists may include responding in any suitable manner. As an example, the response at 360 may include ceasing rotation at 310. In some such examples, ceasing rotation may include ceasing current supply to a motor of the circular saw. In some such examples, the circular saw may include a brake assembly, such as brake assembly 80 of FIGS. 1-2, which is configurable to be selectively actuated to stop rotation of the circular saw blade. Ceasing rotation may additionally or alternatively include actuating the brake assembly to stop rotation of the circular saw blade.

[0111] In some examples, method 300 can include initiating a response at 360 in response to, or only in response to, multiple instances of the determination at 350. In other words, a given kickback event may occur during a time interval during which the determination at 350 is performed multiple discrete times, and the response at 360 can include responding if, or only if, the determination at 350 indicates that a kickback condition exists for two or more discrete times out of the multiple discrete times.

[0112] As described, aspects of the hand-held power tool 8 according to the present disclosure are more particularly described in relation to a circular saw 10. Similarly, aspects of the method 300 according to the present disclosure are more particularly described in relation to a circular saw. This description is for illustrative purposes only, and it is within the scope of the present disclosure that the method 300 may also be utilized with other types of hand-held power tools, as described herein. With this in mind, a circular saw as disclosed herein with respect to the method 300 may also be referred to and / or may be a hand-held power tool herein. Similarly, a blade as disclosed herein with respect to the method 300 may also be referred to and / or may be a tool herein. Additionally, an arbor as disclosed herein with respect to the method 300 may also be referred to and / or may be a tool holder herein. Additionally, a blade rotation surface as disclosed herein with respect to the method 300 may also be referred to herein as a tool working surface and / or a tool working axis.

[0113] In this disclosure, some exemplary, non-exclusive embodiments have been discussed and / or presented in the context of flow diagrams or flowcharts that depict and describe a methodology as a series of blocks or steps. Unless specifically specified in the accompanying description, it is within the scope of this disclosure that the order of the blocks may differ from the order depicted in the flow diagrams, including two or more blocks (or steps) occurring in a different order and / or simultaneously. It is also within the scope of this disclosure that the blocks or steps may be implemented as logic, and may be expressed as being implemented as logic. In some applications, the blocks or steps may represent expressions and / or operations to be performed by functionally equivalent circuitry or other logical devices. The illustrated blocks may, but are not required to, represent executable instructions that cause a computer, processor, and / or other logical device to respond, perform an operation, change state, generate an output or display, and / or make a decision.

[0114] As used herein, "and / or" placed between a first item and a second item means one of: (1) the first item, (2) the second item, and (3) the first item and the second item. Multiple items listed with "and / or" should be considered in the same way, i.e., "one or more" of the items so combined. Other items may optionally be present in addition to the items specifically identified with "and / or," whether related or unrelated to the specifically identified items. Thus, as a non-limiting example, a reference to "A and / or B," when used with open-ended language such as "comprising," may refer in one embodiment to only A (optionally including items other than B), in another embodiment to only B (optionally including items other than A), and in yet another embodiment to both A and B (optionally including other items). These items may be elements, acts, structures, steps, operations, values, and the like.

[0115] As used herein, the phrase "at least one" in reference to a list of one or more items should be understood to mean at least one item selected from any one or more of the listed items, and should not necessarily be understood as including at least one of each and every item specifically listed in the list of items, nor excluding any combination of items in the list of items. This definition allows for the optional presence of items other than the specifically identified items in the list of items to which the phrase "at least one" refers, whether or not they relate to those specifically identified items. Thus, as a non-limiting example, the phrase "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently, "at least one of A and / or B") may, in one embodiment, refer to at least one, optionally more than one, A, and no B (and optionally including items other than B); in another embodiment, at least one, optionally more than one, B, and no A (and optionally including items other than A); and in yet another embodiment, at least one, optionally more than one, A, and at least one, optionally more than one, B (and optionally other items). In other words, "at least one," "one or more," and "and / or" are open-ended phrases and act both conjunctively and disjunctively. For example, "at least one of A, B, and C," "at least one of A, B, or C," "one or more of A, B, and C," "one or more of A, B, or C," "A, B, and / or C" can mean A only, B only, C only, both A and B, both A and C, both B and C, both A, B, and C, and any of the above, optionally in combination with at least one other item.

[0116] If any patent, patent application, or other reference is incorporated by reference herein and (1) defines a term in a manner that conflicts with and / or (2) otherwise conflicts with any other portion of this disclosure and / or any other incorporated reference, the unincorporated portion of this disclosure shall control, and the incorporated term or disclosure shall control only with respect to the reference in which the term was defined and / or in which the incorporated disclosure originally resided.

[0117] As used herein, the terms "adapted" and "configured" mean that an element, component, or other subject matter is designed and / or intended to perform a given function. Thus, the terms "adapted" and "configured" should be understood to mean that a given element, component, and / or other subject matter is specifically selected, generated, implemented, utilized, programmed, and / or designed for performing a given function, rather than that the given element, component, and / or other subject matter is merely "capable of performing" a given function. It is also within the scope of the present invention that elements, components, and / or other described subject matter described as being adapted to perform a particular function may, in addition or alternatively, be described as being configured to perform the function, and vice versa.

[0118] As used herein, the terms "for example," "as an example," and / or simply "example," when used with respect to one or more components, features, details, structures, embodiments, and / or methods according to the present disclosure, are intended to convey that the described components, features, details, structures, embodiments, and / or methods are exemplary, non-exclusive examples of the components, features, details, structures, embodiments, and / or methods according to the present disclosure. Thus, the described components, features, details, structures, embodiments, and / or methods are not intended to be limiting, essential, or exclusive / exhaustive, and other components, features, details, structures, embodiments, and / or methods are also within the scope of the present disclosure, including structurally and / or functionally similar and / or equivalent components, features, details, structures, embodiments, and / or methods.

[0119] As used herein, "at least substantially" when modifying a degree or relationship can include not only the "substantial" degree or relationship referred to, but also the full extent of the degree or relationship referred to. A substantial amount of the degree or relationship referred to can include at least 75% of the degree or relationship referred to. For example, an object at least substantially formed of a material includes an object at least 75% of the object formed of the material, and also includes an object completely formed of the object. As another example, a first length at least substantially equal to a second length includes a first length having a length within 75% of the second length, and also includes a first length that is the same length as the second length. [Industrial Applicability]

[0120] The hand held power tools, circular saws and methods disclosed herein are applicable to the power tool industry.

[0121] The above disclosure is believed to encompass multiple separate inventions having independent utility. Each of these inventions is disclosed in its preferred form, but the specific embodiments thereof disclosed and illustrated herein should not be considered in a limiting sense, as numerous variations are possible. The subject matter of the invention includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions, and / or properties disclosed herein. Similarly, when a claim recites "a" or "first" element or the equivalent, such claim should be understood to include the incorporation of one or more such elements, and does not require or exclude two or more such elements.

[0122] The following claims are believed to be directed to one of the disclosed inventions and to particularly point out certain combinations and subcombinations that are novel and non-obvious. Inventions embodied in other combinations and subcombinations of features, functions, elements, and / or properties may be claimed through amendment of the present claims or presentation of new claims in this or a related application. Such amended or new claims, whether directed to a different invention or to the same invention, and whether different, broader, narrower or equal in scope to the original claims, are deemed to be included within the inventive subject matter of this disclosure.

Claims

1. 1. A method for detecting a kickback condition in a handheld power tool, comprising: moving an implement of the handheld power tool within a plane of implement motion; Detecting movement of the handheld power tool and workpiece contact parameters; applying a falsification parameter; determining that the kickback condition exists based on verification parameters including the movement of the handheld power tool and the workpiece contact parameters and based on the refutation parameters; Including, A method for detecting a kickback condition, wherein the workpiece contact parameter is within a contact value range when the tool is in contact with the workpiece, and the workpiece contact parameter is within a non-contact value range when the tool is spaced from the workpiece.

2. The detection of the movement includes: (ai) detecting a magnitude of acceleration of the handheld power tool; (a-ii) detecting the direction of the acceleration of the handheld power tool; (a-iii) detecting an angular velocity of the handheld power tool; The method of claim 1 , comprising at least one of:

3. The determination is (bi) detecting a magnitude of acceleration of the hand-held power tool (ai); and if the magnitude of the acceleration of the hand-held power tool is greater than a threshold acceleration, (b-ii) detecting a direction of acceleration of the hand-held power tool (a-ii), and if the direction of acceleration of the hand-held power tool is within a threshold direction range, and / or (b-iii) detecting an angular velocity of the handheld power tool (ai), and if the angular velocity of the handheld power tool is within a threshold angular velocity; 3. The method of claim 2, comprising determining that the kickback condition exists in:

4. The refutation parameters are: (a) a linear acceleration component of the acceleration of the handheld power tool; and (b) angular velocity components of the angular velocity of the handheld power tool; and (c) a linear acceleration direction component of the acceleration of the handheld power tool; and The method according to any one of claims 2 to 3, comprising at least one of:

5. The determination is (i) determining that the kickback condition exists when the linear acceleration component is outside a threshold linear acceleration component range; and (ii) determining that the kickback condition does not exist when the linear acceleration component is within a threshold linear acceleration component range; The method of claim 4 , comprising one of:

6. The method of claim 4 , wherein when the linear acceleration component is within a threshold linear acceleration component range, the direction of the linear acceleration component is toward a leading edge of the hand-held power tool.

7. The determination is (i) determining that the kickback condition exists when the angular velocity component is outside a threshold angular velocity component range; and (ii) determining that the kickback condition does not exist when the angular velocity component is within a threshold angular velocity component range; The method of claim 4, comprising:

8. 8. The method of claim 7, wherein the angular velocity component is within the threshold angular velocity component range if and only if rotation about a linear acceleration axis includes rotation of an implement holder of the hand-held power tool toward a workpiece support of the hand-held power tool.

9. The method of claim 4 , wherein the linear acceleration direction coincides with an angular velocity axis of the angular velocity.

10. The linear acceleration direction component is (i) pointing toward the front edge of the handheld power tool; (ii) facing away from the user of the handheld power tool; (iii) facing away from the user-actuated assembly-facing surface of the workpiece support of the handheld power tool; The method of claim 4, wherein the at least one of

11. The linear acceleration directional component is within a threshold angular range of a cutting direction of the hand held power tool, optionally the threshold angular range comprising: (i) at least 0°, at least −30°, at least −45°, at least −60°, or at least −80°; (ii) at most 80°, at most 60°, or at most 45°; The method of claim 4 , wherein the boundary is at least one of:

12. The handheld power tool comprises: a workpiece support defining a workpiece facing surface, a workpiece opposite surface, a leading edge, and a trailing edge; (i) the threshold direction range is at least partially perpendicular to the workpiece-opposing surface of the workpiece support; (ii) the threshold direction range is at least partially toward the trailing edge of the workpiece support; and (iii) the threshold direction range is defined within a quadrant extending between a first vector toward the trailing edge of the workpiece support and along the workpiece-opposing surface of the workpiece support, and a second vector intersecting the first vector and perpendicular to the workpiece-opposing surface of the workpiece support; The method according to any one of claims 1 to 3, wherein the method is at least one of the following:

13. The method according to any one of claims 1 to 3, wherein the refutation parameter is determined within a detection time window.

14. The detection time window is: (i) the acceleration of the handheld power tool is greater than a threshold acceleration; (ii) the direction of the acceleration of the handheld power tool is within a threshold direction range; and (iii) the angular velocity of the handheld power tool is greater than a threshold angular velocity; 14. The method of claim 13, further comprising extending the threshold detection time before the kickback time, wherein the threshold detection time is at least one of:

15. 4. The method of claim 1, wherein the method includes determining that the kickback condition exists if or only if the workpiece contact parameter is within the contact value range.

16. The method of any one of claims 1 to 3, further comprising cutting a workpiece with the tool after initiating the movement and simultaneously with the detection.

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