Patent Application
20210323189
The present invention relates to a portable circular saw having a sole plate, a housing, and a drive unit which at least in portions is disposed in the housing and which is assigned a tool receptacle for an interchangeable saw blade, wherein the drive unit is configured for rotatingly driving the interchangeable saw blade about an assigned rotation axis, and wherein the portable circular saw by means of the sole plate is guidable along a workpiece.
A circular saw, configured as a portable circular saw, which has a housing and a drive unit which in portions is disposed in the housing is known from the prior art. The drive unit herein is assigned a tool receptacle for an interchangeable saw blade, and the drive unit is configured for rotatingly driving the interchangeable saw blade about an assigned rotation axis.
DE 35 46 896 C2 furthermore discloses a method for detecting an imminent kickback state for increasing the operational safety in a motorized tool. The method is based on detecting a percentage change in the rotating speed of the motor. This results in an adequate sensitivity of the method in the case of high rotating speeds of the motorized tool, and excessive sensitivities are avoided in the case of low rotating speeds.
DE 10 2007 062 256 A1 furthermore discloses a circular saw having a saw blade that is rotatingly driven about a rotation axis, and at least a first riving knife. One embodiment of the circular saw herein is configured in such a manner that for increasing the operational safety at least the first riving knife by means of a servomotor is automatically movable relative to the rotation axis of the saw blade.
The present invention provides a portable circular saw having a sole plate, a housing, and a drive unit which at least in portions is disposed in the housing and which is assigned a tool receptacle for an interchangeable saw blade, wherein the drive unit is configured for rotatingly driving the interchangeable saw blade about an assigned rotation axis, and wherein the portable circular saw by means of the sole plate is guidable along a workpiece. A safeguard device having at least one sensor element is provided, wherein the safeguard device is configured for detecting crashing of the portable circular saw into the workpiece, at least as arises in a sawing procedure, and upon detecting any crashing into the workpiece is configured for decelerating and/or switching off the drive unit.
The invention thus enables a reliable detection of a crashing of the portable circular saw into the workpiece, and preferably associated herewith an immediate deceleration and/or switching-off of the drive unit. Consequently, the operational safety can be significantly increased. Moreover, the end of a saw cut and a kickback, that is to say jamming of the saw blade in the workpiece, can be reliably detected by way of the safeguard device.
The term of so-called “crashing into” in the context of the present description is understood to be an at least partial braking or rupturing of the workpiece outside of the saw cut generated in the workpiece by means of the circular saw. The safeguard device can moreover be designed as a retrofit kit for usual standard portable circular saws or other sawing devices.
The sensor element preferably has at least one acceleration sensor. On account thereof, the safeguard device makes do without damage-prone components that are mechanically moved.
The sensor element preferably has at least one rotating speed sensor. A particularly simple construction of the required sensor mechanism is thus provided. The crashing of the portable circular saw into a workpiece explained above can be detected by way of a rapid increase in the rotating speed, for example, and the drive unit can be switched off and/or at least partially decelerated.
In the case of a technically favorable refinement, the sensor element has at least one electromechanical and/or one electronic switching means. A particularly robust sensor mechanism which at the same time is of simple construction can be implemented on account thereof. A switching means of this type can at the same time be comparatively easily repaired in the event of a defect.
The at least one switching means in the region of a rectangular passage opening of the saw blade is preferably disposed on a workpiece-facing bearing face of the sole plate. A reliable detection of any potential crashing of the portable circular saw is possible on account thereof.
According to one embodiment, the at least one switching means at least in portions runs in the region of at least one narrow side and/or at least in portions runs in the region of at least one longitudinal side of the passage opening. The detection of any potential crashing of the portable circular saw thus takes place in the direct vicinity of the saw cut.
According to one further embodiment, the at least one switching means is configured so as to be L-shaped, U-shaped, or rectangular. Various variants of design in terms of construction are provided on account thereof.
According to a further embodiment, the at least one switching means comprises the passage opening in the manner of a frame. Consequently, detecting is possible on all sides.
The at least one switching means in the case of the sole plate bearing on the workpiece preferably terminates so as to be flush with the bearing face of said sole plate and when raising the sole plate from the workpiece springs out of said bearing face. A safe and reliable integration of the safeguard device in the portable circular saw is thus provided.
The at least one switching means preferably has a spring-loaded rocker or pressure plate which is in particular configured for activating an electrical contact and/or a strain gauge of the switching means. A digital or analog signal for evaluating by means of a control apparatus of the safeguard device can thus be selectively provided by the switching means.
According to a further embodiment, the at least one sensor element has an optical detector. Consequently, a crashing procedure of the portable circular saw is possible in a non-contacting manner.
The at least one optical detector in the region of a passage opening of the saw blade is preferably disposed so as to be flush in a workpiece-facing bearing face of the sole plate. On account thereof, the detection thus takes place in the direct vicinity of the saw cut.
In the case of a technically advantageous refinement, the bearing face for configuring an area-measuring zone has at least one depression, wherein the at least one optical detector is disposed in the at least one depression. On account thereof, a planar detection of a crashing procedure is provided.
The at least one optical detector is preferably formed having an optical reflex sensor. A particularly compact construction is thus provided.
The safeguard device preferably has a control apparatus. On account thereof, the digital or analog signals supplied by the at least one sensor element can be comprehensively evaluated for detecting the crashing of the portable circular saw and for switching off the drive unit. The control apparatus can be implemented, for example, by way of a microcomputer embodied as an integrated circuit, or the like.
The invention is explained in more detail in the description hereunder by means of exemplary embodiments illustrated in the drawings in which:
The drive unit 120 preferably serves for driving a tool receptacle 144 for an interchangeable saw blade 130. The drive unit 120 herein is in particular configured for rotatingly driving the interchangeable saw blade 130 about an assigned rotation axis 142. The saw blade 130 is preferably configured as a circular saw blade 132 having a serrated cutting edge 134.
The portable circular saw 100 for the mains-dependent supply of power is preferably connected mechanically and electrically to a mains connector 118, but additionally or alternatively could also be equipped with a rechargeable battery pack for the mains-independent supply of power. The portable power tool 102, deviating from the illustration in
The housing 110 of the portable circular saw 100 preferably has a first end 114 and a second end 116 that is directed away from the first end 114. The portable circular saw 100 herein is provided for sawing in an operating direction 150. A corresponding operating region 152 herein is preferably situated at the first end 114, or ahead of the saw blade 130 in the operating direction 150. Moreover, the portable circular saw 100 is preferably provided with an at least substantially planar, preferably rectangular, sole plate 122. The sole plate 122 has a bearing face 124 that is directed away from the drive unit 120 and with the aid of which the portable circular saw 100 is guidable, for example, along an at least substantially flat upper side 154 of a workpiece 160 which here is only indicated by a dotted line. In the case that no plunge cuts or insert cuts, respectively, are carried out with the portable circular saw 100, the saw blade 130 typically penetrates the workpiece 160 completely and therefore at least partially exits the workpiece 160 in the region of a lower side 156 of said workpiece 160.
A riving knife which for increasing the operational safety is usually provided in the case of conventional portable circular saws and which is guided through a saw cut 158 generated in the workpiece 160 by the portable circular saw 100 and by means of which jamming of the saw blade 130 is to be prevented, is not plotted here for the sake of improved clarity of the drawing. The portable circular saw 100 moreover usually has an optional pivoting protective hood. Corresponding pivoting protective hoods are well known from the relevant prior art, which is why a detailed description of the optional pivoting protective hood is prevented for the sake of simplicity and brevity of the description.
According to the invention, a safeguard device 170, preferably for further increasing the operational safety, is integrated in the portable circular saw 100, by means of which safeguard device 170 a crashing of the portable circular saw 100 into the workpiece 160 inter-alia is able to be detected and the drive unit 120 is able to be switched off and/or at least partially decelerated in a timely manner, or immediately, respectively. Furthermore, the end of a saw cut to be carried out as well as jamming of the saw blade 130 can optionally also be detected by means of the safeguard device 170, wherein the jamming of the saw blade 130 can lead to a dangerous so-called kickback. In both cases, the drive unit 120, preferably for increasing the operational safety of the user or operator, respectively, is switched off in a controlled, preferably immediate, manner by the safeguard device 170. In the case of the detection of the saw cut end, an at least partial deceleration of the drive unit 20 can also be provided.
In order for the crashing of the portable circular saw 100 into the workpiece 200 to be reliably detected, the first embodiment of the safeguard device 170 has a sensor element 214 which here in an exemplary manner is implemented having a preferably electronic acceleration sensor 216. With the aid of the acceleration sensor 216, at least the linear acceleration of the portable circular saw 100 in the direction of a z-axis of a rectangular coordinate system 220, or in the direction of the floor 208, can be detected so as to detect the crashing procedure of the portable circular saw 100 into the workpiece 200, schematically illustrated here, with high reliability. On account of the crashing of the portable circular saw 100 into the workpiece 200, a significant acceleration gz which is detectable by means of the acceleration sensor 216 and which for evaluation is transmitted to the safeguard device 170 is created primarily in the direction of the z-axis of the coordinate system 220, or in the direction of the hard ground 208, respectively.
By way of the safeguard device 170, the drive unit 120 of
Furthermore, the safeguard device 170 can have at least one gyro sensor, or an electronic angular acceleration sensor, respectively, (not illustrated for the sake of improved clarity in the drawing) as a further sensor element so as to additionally detect potential angular accelerations of the portable circular saw 100 about at least one of the three axes of the coordinate system 220 and thus tilting movements of the portable circular saw 100 and evaluate said angular accelerations by way of the safeguard device 170.
The diagram by means of a first curve profile 250, illustrated with a solid line, and of a second curve profile 252, plotted with a dashed line, illustrates the rotating speed of the current rotating speed of the saw blade, or of the drive unit of the portable circular saw, respectively, in each case as a function of the sawing progress, as determined by the rotating speed sensor and transmitted to the safeguard device for evaluation, wherein the rotating speed is plotted on the vertical axis and the sawing progress of the portable circular saw through the workpiece is plotted on the horizontal axis.
In a first region 254 of the two curve profiles 250, 252, the drive unit of the portable circular saw is idling, that is to say that the saw blade freely rotates at the usual idling rotating speed. In a second region 256 of the two curve profiles 250, 252, the saw blade increasingly enters a workpiece to be sawn until the latter is completely penetrated, and the rotating speed consequently steadily drops to an operating rotating speed that is usual in the normal sawing operation. In a third region 258 of the two curve profiles 252, 254 the portable circular saw is in the normal, or orderly, respectively, sawing operation, wherein the operating rotating speed remains almost constant. The two curves 250, 252 in the first three regions 254, 256, 258 of the diagram have practically identical profiles, or are almost mutually congruent, respectively.
In a fourth region 260 the first curve 250 however rises considerably slower in comparison to the sinking of the latter at the beginning of sawing in the second region 256, this indicating a delayed increase in the rotating speed of the saw blade when exiting the workpiece until the idling rotating speed is achieved again. By contrast, in the region of a transition between the third region 258 and the fourth region 260, in the region of a point 262 there is an abrupt, or comparatively steep, rise of the second curve 252, or of the rotating speed of the saw blade, respectively, which enables an unequivocal conclusion of crashing of the portable circular saw into the workpiece having taken place. The abrupt rotation speed increase 264 that can be measured directly after the crashing, is evaluated by the safeguard device and serves as an unequivocal signal for switching off and/or for at least partially decelerating the drive unit of the saw blade when a crashing procedure arises.
A saw cut end in the normal sawing operation is present and can be detected by means of the rotating speed sensor when the rotating speed increase of the drive unit corresponds to the profile of the second curve 250 in the fourth region 260 of the diagram such that the safeguard device can optionally initiate the switching off and/or the at least partial deceleration of the drive unit of the portable circular saw.
A practically abrupt drop in the second curve 252 to a rotating speed of approximately “0” (not illustrated) however indicates a total blockage of the saw blade within the workpiece to be sawn, which can arise, for example, on account of the saw blade tilting or the like. In order for the accident-prone kickback of the portable circular saw toward the user to be avoided in such a situation, the safeguard device can likewise initiate the immediate switching off and/or at least partial deceleration of the drive unit of the portable circular saw.
The switching means 304 can be implemented, for example, having a spring-loaded rocker 316, or having a spring-loaded pressure plate 318 which in the simplest case are coupled, for example, to an electrical contact 320 and/or a strain gauge 322, the signals thereof being in each case supplied to a control apparatus 330 within the safeguard device 300. The electrical contact 320 can be, for example, a simple electromechanical closing contact, an opening contact, or a two-way contact which is capable of being activated in a sensory or switching manner. In the case of the bearing face 124 of the sole plate 122 of the portable circular saw 100 not bearing on a workpiece to be sawn, or the switching means 304 not being mechanically stressed, respectively, said switching means 304 preferably does not terminate so as to be flush with the bearing face 124 of the sole plate 122, but springs out of the latter to a preferably minor extent and when non-stressed remains in this slightly proud position.
Should crashing of the portable circular saw 100 arise, the switching means 304 preferably springs out of the plane of the bearing face 124 of the sole plate 122 in the direction of the workpiece to be sawn such that the electrical contact 320 and/or the strain gauge 322 preferably emit an unequivocal electrical signal which can be evaluated by a control apparatus 330 of the safeguard device 300. When an electrical signal of this type that is generated by the switching means 304 arises, the safeguard device 300 preferably switches off the drive unit 120 of
Alternatively or additionally, the rocker 316 or the pressure plate 318 of the switching means 304 can also have a permanent magnet (not illustrated) which when deflecting in the event of the portable circular saw 100 crashing in a non-contacting manner activates or releases a magnetic sensor such as, for example, a Hall effect sensor, a reed relay, or the like. The signal generated by the magnetic sensor in this instance preferably serves in turn for switching off and/or at least partially decelerating the drive unit 120 of
Alternatively, a second electromechanical and/or electronic switching means (not illustrated here) which in terms of construction is configured to be identical to the first switching means 304 can be provided in the region of the first longitudinal side 312 of the passage opening 306. The switching off and/or the at least partial deceleration of the drive unit 120 of
By contrast to the embodiment of
Should crashing of the portable circular saw 100 arise, the switching means 354 is preferably released from the workpiece 200 and preferably springs out of the bearing face 124 of the sole plate 122, as is indicated by the double arrow 364, and generates a corresponding electrical signal within the safeguard device 350 such that the latter can switch off and/or at least partially decelerate the drive unit 120 of
Moreover, a further rectangular sensor element 408 which is implemented having a spring-loaded switching means 410 and the design embodiment thereof in terms of construction and the functional mode thereof corresponding to those of the switching means 404 can be placed on the second narrow side 310 of the passage opening 306 for the saw blade 130. Accordingly, the non-stressed switching means 410 springs at least partially out of the run-on face 124 of the sole plate 122 and when running over the workpiece 200 is pushed back into the sole plate 122 again such that the switching means 410 in this instance terminates as to be flush with said sole plate 122. The contraction and expansion of the spring-loaded switching means 410 herein is indicated by the double arrow 412. Should one of the switching means 404, 410 lose contact with the workpiece 200, this is an unequivocal indication that the portable circular saw 100 has crashed into the workpiece 200 to be sawn such that safeguard device 400 rapidly switches off and/or at least partially decelerates the drive unit of the portable circular saw 100.
By contrast to the preceding embodiments, the safeguard device 450 has a sensor element 452 which is preferably formed having a frame-type, spring-loaded electronic and/or electromechanical switching means 454 which preferably comprises the passage opening 306 on all sides so as to be slightly spaced apart therefrom, or in the manner of a frame, respectively. In the non-stressed state of the switching means 454, the latter preferably springs out of the bearing face 124 of the sole plate 122, while said switching means 454 bearing on the workpiece (not illustrated here) as is indicated by the double arrow 456, preferably springs back into the sole plate 122 of the portable circular saw 100 again so as to terminate flush with the bearing face 124. In the event of these portable circular saw 100 crashing, the switching means 454 preferably springs out of the sole plate 122, and the safeguard device 450 immediately switches off the drive unit 120 of
The functioning of the safeguard device 450 otherwise again corresponds substantially to that of the variants of embodiments of safeguard devices already described above such that, for reasons of brevity of the description, reference at this point is to be made to the relevant paragraphs of the description.
Should crashing of the portable circular saw 100 into the workpiece (not illustrated here) arise, the release of only one of the two switching means 504, 512 from the workpiece, or the fragments thereof, suffices, wherein at least one of the switching means 504, 512 rises out of the bearing face 124 of the sole plate 122 so as to trigger the immediate switching off of the drive unit and/or the at least partial deceleration of the drive unit 120 of
Each of the two again spring-loaded switching means 554, 562, as is indicated by the two double arrows 568, 570, without contact with the workpiece preferably springs out of the run-on face 124 of the sole plate 122 and when the sole plate 122 bears on the workpiece (not illustrated here) is again pushed back into the sole plate 122 so as to be preferably completely flush therewith.
In the event of the portable circular saw 100 crashing into the workpiece (not plotted), at least one of the spring-loaded switching means 554, 562 preferably springs abruptly out of the sole plate 122, and the safeguard device 550 in response to a corresponding, preferably electrical, signal again triggers the immediate switching off and/or the at least partial deceleration of the drive unit 120 of
Consequently, a particularly reliable detection of crashing of the portable circular saw 100 is possible, since the second switching means 562 extends approximately up to the center of a saw cut to be carried out with the portable circular saw 100.
The optical detector 604 here in only an exemplary manner is situated centrically in the region of the first narrow side 308 of the passage opening 306, while the optical detector 610 is positioned in the region of the second narrow side 310 of the passage opening 306. The optical detectors 606, 608 as well as 612, 614 in the region of the two longitudinal sides 312, 314 of the passage opening 306 are preferably disposed in each case in pairs in the sole plate 122 for the saw blade 130.
Should the sole plate 122 bear completely on the workpiece to be sawn, the optical detectors 604 to 614 are preferably shaded, and the portable circular saw 100 is in the normal sawing operation. However, should sudden crashing into the workpiece (not illustrated here) arise, each of the optical detectors 604 to 614 is typically at least briefly illuminated by the ambient light, and the safeguard device 600 by virtue of this temporal brightness transition which can be evaluated in a defined manner initiates the immediate switching off and/or the at least partial deceleration of the drive unit 120 of
The detectors 604 to 614 can be implemented, for example, having passive optical elements which per se do not emit any electromagnetic radiation but only respond to the external ambient radiation. In this context, photo resistors, photodiodes, photo transistors, or the like can be used, for example. Alternatively or additionally to the purely passively acting optical detectors, active optical elements such as, for example, so-called optical reflex sensors, etc., can also be used, which per se emit electromagnetic radiation which in a situational manner is reflected by the workpiece and is then evaluated by the reflex sensor. The radiation emitted by the optical elements can be modulated for further optimizing the interference resistance.
At least one optical detector (not illustrated here) is preferably installed in each of the (here only exemplary) four L-shaped depressions 656, 658, 660, 662. The optical detectors herein are preferably attached in the depressions 656, 658, 660, 662 such that said detectors do not protrude beyond the run-on face 124 of the sole plate 122 but if at all terminates as to be flush with the run-on face 124 of the sole plate 122, wherein a fully planar bearing of the sole plate 122 on the workpiece to be sawn is ideally guaranteed (cf. Reference sign 200,
The area measuring zone 654 is derived by virtue of the preferably four L-shaped depressions 656, 658, 660, 662 which circumferentially adjoin one another and are disposed in the manner of a quadrant, having the at least one optical detector disposed in each case therein. The area measuring zone 654 comprises the passage opening 306 of the sole plate 122 in the manner of a frame such that a particularly reliable as well as non-contacting detection of a crashing procedure of the portable power tools 100 into the workpiece (not plotted here) is possible by means of the safeguard device 650.
Shapings that deviate from the L-shaped geometry of the depressions 656, 658, 660, 662 that are set forth herein only in an exemplary manner as well as a higher and/or lower number of the depressions 656, 658, 660, 662 within the sole plate 122 of the portable circular saw 100 can likewise be provided.
The workpiece 200 here only partially covers the depression 656 in the sole plate 122 of the portable circular saw 100 such that the electromagnetic radiation emitted by the optical reflex sensor 672 is if need be partially reflected, and the optical reflex sensor 672 does not emit any relevant electrical signal, for example. In such a situation, a crashing procedure of the portable circular saw 100 in the workpiece 200 is present, such that the safeguard device 650 triggers the immediate switching off and/or the at least partial deceleration of the drive unit of the portable circular saw 100. However, should the workpiece 200 cover the depression 656 in a substantially complete manner, the electromagnetic radiation emitted by the optical reflex sensor 672 is almost completely redirected from the workpiece 200 to the optical reflex sensor 672 such that the latter emits a signal which indicates to the safeguard device 650 the normal sawing operation, for example.
Instead of the optical reflex sensor 672 that actively emits an electromagnetic radiation, the optical detector 670 can also be implemented having a purely passively acting optical element such as, for example, a photoresist, a photodiode, a phototransistor, or the like, which solely registers the incoming electromagnetic radiation from the environment and admits a corresponding electrical signal. The functional mode of the optical detector 670 in this instance corresponds to the functional mode of the passive optical detectors already described in the context of
After a rapid switching off and/or an and at least partial deceleration of the drive unit 120 of
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2017 211 270.0 | Jul 2017 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/064184 | 5/30/2018 | WO | 00 |
