WO1996022175A2

WO1996022175A2 - Safety device for electrically driven hand tools, in particular circular and compass saws

Info

Publication number: WO1996022175A2
Application number: PCT/EP1996/000196
Authority: WO
Inventors: Iradj Hessabi
Original assignee: Iradj Hessabi
Priority date: 1995-01-20
Filing date: 1996-01-18
Publication date: 1996-07-25
Also published as: DE19501579A1; WO1996022175A3; TW349898B; EP0873226A2; AU4619896A

Abstract

The invention concerns a safety device for electrically operated hand tools (1), in particular circular and compass saws in which the motor drive is transmitted via a clutch plate with a clutch (10) to a tool (5) fitted on a tool carrier (4). The safety device in question is provided with an electronic sensor circuit (SÜS) with lifting magnet control (HS) which, if the tool (5) comes into contact with any part of the operator's body, breaks the connection between the drive motor (8) and tool (10) by causing the clutch magnetically to disengage. To ensure easy re-engagement of the clutch (10) where there is no danger to the operator, it is proposed that the disengageable clutch should be provided with coupling elements (13, 16) capable of axial displacement or radial excursion, the said coupling elements being displaced/lifted by a lifting magnet (15) once energised out of the seats (11, 25) which create the force flux.

Description

Safety device for electrically powered hand tools. especially jigsaws and circular saws.

The invention relates to a safety device for electromotively powered hand tools, in particular jigsaws and circular saws, in which the flow of force from the motor to the tool is interrupted by a direct flow of force between the output shaft, the drive motor and the drive shaft of the tool Appropriate, disengageable clutch is guided with coupling elements, the coupling elements interacting with a lifting magnet which can be excited by means of an electronic sensor which can be activated when the tool is touched with a body part, disengages the coupling and thus interrupts the connection from the motor to the tool.

Safety devices on such tools are intended to protect the user of such machines when, for example, the fingers come into the working area of the tool. A saw - regardless of whether circular or jigsaw - can cause considerable injuries if Safety devices on such tools are intended to protect the user of such machines when, for example, the fingers come into the working area of the tool. A saw - irrespective of whether circular or jigsaw - can cause considerable injuries if a finger gets into the sawing area, especially since the tool cannot be stopped immediately due to the trailing motor, but especially because of the delay in reaction of the user. In DE-GM 91 09 573 it has already been proposed to provide the drive with a disengagement disk which, under electromagnetic control, then separates the drive from the tool when a galvanically connected sensor absorbs a body current which is transmitted from the tool via, for example, the Fingers (or another part of the body) flows back to the tool, this technique of utilizing a body current being known, for example, from high-resistance sensors. If a body current is now picked up, an electromagnet is excited, which pulls the release disk back, so that the motor drive and tool are separated, which then stops immediately because of its friction. In jigsaws, the coupling between the drive and tool for converting the rotating movement into a linear movement is effected by a driver pin, which is arranged so as to be radially movable on the disengaging disk and is guided in a machine-fixed slot connected to the tool. If the safety device according to DE-GM 9109573 is used here, the drive may be separated from the tool when the contact occurs, but reinsertion is only possible with considerable difficulty since the driver pin only hits the slot directly by chance and can be introduced. In the case of circular saws, the clutch disc is axially displaced by means of a ring-shaped lifting magnet according to this proposal so that the drive is decoupled from the circular saw blade and the flow of force is thus interrupted. Because of the considerable torque of such rotating circular saw blades, an additional brake is provided which is designed as a mechanically acting friction brake. Here too, direct reinsertion can only be achieved if the driver pin (s) accidentally "hit" the hole in the tool or its holder. In both cases this "meeting" because of the considerable differences in speed, great difficulty for re-engagement, especially since the holes for ensuring a perfect power transmission with respect to the diameter of the drive pins must be selected so that a good fit is achieved, and especially with many tools for reasons of Tool geometry no means for inserting the driver pins into the hole can be provided.

This is where the invention comes in, which is based on the object of further developing the device according to DE-GM 91 09 573 in such a way that it is easy to re-engage while maintaining the security level.

A solution to this problem is described in claim 1, another in claim 8; advantageous further developments and preferred embodiments describe the subclaims.

In one embodiment, the invention provides that the lifting magnet axially (directly or indirectly) moves the driving pins. For this purpose, the output shaft of the drive motor advantageously has a clutch disc arranged on the motor side of the tool, which is provided with a number of locking points arranged in a circle around its center, at least some of which cooperate with the coupling elements designed as driving pins or driving lugs , which constantly form the force transmission member in engagement with the tool via its holder or via its drive shaft, the lifting magnet causing the axial displacement of the clutch disc / driver pins / driver lugs, which engage at least in some of the latching parts, to disengage, and wherein the lifting magnet has means acting against its working direction, which are tensioned when the lifting magnet is excited and which, when de-energized, cancel the displacement of the clutch disc or driver pin caused by the latter. This reset of the clutch can be prevented by a lock, so that the lock must first be released manually to reset. This has the advantage that, before resetting, the cause for the safety device responding is must be looked for.

By decoupling the driver pins from the locking points by their axial displacement, the flow of force is interrupted, so that the tool comes to a standstill and dangers are excluded. The axial movement is brought about by a solenoid which can be activated by a body current via a control electronics, the lifting pins remaining in engagement with the tool or its holder, regardless of the excited state of the lifting magnet. The parts of the drive which are decoupled from the drive in the event of safety and come to rest, insofar as they are mounted on the output shaft, are decoupled with bearings opposite the output shaft, so that a direct force path is interrupted.

A first embodiment of this design is provided in that the tool or its holder, which is provided with at least one fixedly arranged driving pin, is arranged so as to be freely rotatable coaxially to the axially displaceable clutch disk and the driver pins are located in the latching points of the clutch disk in its latching position ¬ len intervene, the lifting magnet and clutch disc interacting in such a way that the clutch disc is attracted when the lifting magnet is excited and the driver pins located in the latching points become free. In this embodiment, a permanent connection of driver pin and tool or tool holder is created; the power transmission is interrupted when the driver pin (s) is / are pulled out of the locking points of the clutch disc; it is reinserted by the driver pin (s) being immersed in the rest area. Since the clutch disc as a permanent machine part can be provided with corresponding detent points arranged on a circle concentric to the axis of rotation, the driver pins find one of the detent points and are taken along, the fit in the tool or its holder being irrelevant. Since the axially movable clutch disc acts as a force transmission element in this embodiment, means are provided. see that ensure the flow of power from the output shaft to the clutch disc, for example axially parallel guide grooves. This embodiment is important when the moving tool has to remain free on one side, for example with a circular saw. The axial movement of the clutch disc is effected by means of the lifting magnet when it is de-energized or excited. The driver pins are connected to the tool or its holder, the connection to the tool holder being preferred because of the inevitable tool wear.

In a second embodiment of this embodiment, an axially movable release member is provided with at least one driver pin, freely rotatable, between the clutch disc and tool or its holder, which is fixedly connected to the output shaft of the drive motor, and axially movable is disc-shaped with a diameter preferably larger than that of the clutch disc, and the lifting magnet is arranged in the region of this overhanging circumference with rotation-symmetric field distribution, in which the driver pins directed towards the tool or its holder are in the bores of the tool or Holders are axially displaceable, and in which the driver pins are provided with projections directed towards the clutch disc, which cooperate with the locking points of the axially fixed clutch disc in such a way that the release member is attracted when the lifting magnet is excited and the one located in the locking points n Driver pins become free. The driver pin (s) is / are axially movable, while the clutch disc is fixed with respect to the output shaft. Advantageously, an axially movable, coaxial to the drive shaft and freely rotatable, ferro-magnetic release member is provided for receiving the driving pin (s), which is axially moved in cooperation with the lifting magnet when it is de-energized or excited. Da¬ this release member - as far as moved on the output shaft - is mounted with displaceable bearings, so that the output shaft and release member are uncoupled with respect to a power transmission. The movable disengaging member is particularly advantageous in the case of a plurality of coupling pins, since so that a time-synchronized movement of the driver pins is brought about, which are thus pulled out of the locking points or introduced into them again.

In one embodiment, the disengaging member is arranged between the clutch disk fixedly connected to the output shaft of the drive motor and the tool or its holder and is disk-shaped with a diameter larger than that of the clutch disk. In this area of the projection, the lifting magnet has paired pole shoes which generate a field with a rotationally symmetrical distribution in such a way that the disengaging member is displaced when excited or de-excited so that the driver pins either engage in the locking points of the clutch disc or out of them have moved. The driver pins directed towards the tool or its holder can be axially displaced in the bores of the tool or its holder; they are further provided with projections directed towards the clutch disc, which interact with the locking points of the clutch disc which is axially fixed on the output shaft of the drive motor.

In an alternative embodiment, the disengaging member is arranged on the side of the tool or its holder remote from the clutch disk fixedly connected to the output shaft of the drive motor and is disk-shaped, with a diameter at least equal to the diameter of the circle of the locking points. The lifting magnet is arranged concentrically in the region of this disk and interacts with the release member in such a way that it is axially displaced when the lifting magnet is excited. The driving pins directed towards the tool or its holder can be moved axially in the bores of the tool or holder, so that they interact with the locking points of the clutch disc through engagement through the tool or its holder.

In these arrangements, the driving pin (s) is / are guided through the tool or its holder in such a way that they can be moved axially and are constantly in engagement therewith; the power flow from the drive The motor for the tool is produced by the clutch disc in its interaction with the driver pins. If the release disk is in the "working position" when the solenoid is not energized, the driver pin (s) engages in one or more of the locking points on the tool side of the clutch disk and is / are taken along. If the sensor detects a leakage current from the tool via an external conductor path - here it is assumed that this is the body of the user - the solenoid is excited, it picks up, the disengaging plate goes into its "safety position" and that Driving pins are retracted to such an extent that they slide out of the locking points and thus separate the drive from the tool, but remain in the tool, so that re-engagement only requires immersion in the locking points.

For manual machine tools with rotating movements - for example in the case of a circular saw - the disengaging member advantageously has three coupling pins distributed in a rotationally metric manner, while the clutch disc has at least three locking points distributed in the same way, but is preferably provided with two or three locking points. Provide sets so that when rotating, the driver pins find a first means of engagement after an angular rotation of less than 60 °. For manual machine tools with linear movement - for example in the case of a jigsaw or a fox's tail - the disengaging member advantageously has a driver pin, while the clutch disc has at least one locking point; it is preferably provided with a plurality of sets of locking points. If the locking points are arranged, for example, at an angular distance of 60 °, an angular rotation of at most 60 ° is also sufficient here to provide a first possibility of engagement for the driver pin; If twice the number of locking points is provided, there remains an angular distance of 30 °, with three times the number of 20 °, sufficient to avert dangers from the tool. The locking points 11 assigned to these driving pins 13 form a locking point set, of which two or more can be provided. In order to reduce the rotational energy stored in rotating tools, a braking to provide facility.

Finally, in a third embodiment, an axially movable disengaging member is provided with at least one driver pin, which can be freely rotated and which is axially movable on the side of the tool or the holder thereof which is fixedly facing away from the clutch disk connected to the output shaft of the drive motor and which is axially movable, the disk-shaped is formed with a diameter at least equal to the diameter of the circle of the locking points, and the lifting magnet is arranged concentrically in the area of the disengaging member, in which the axially displaceable driving pins directed towards the tool or its holder in the bores of the tool or Holders are axially displaceable and cooperate through the tool or its holder with the locking points of the clutch disc in such a way that the disengaging member is attracted when the solenoid is excited and the coupling pins located in the locking points become free. The disengaging member is pressed into a "working position" by means of a compression spring, so that immersion can take place while the clutch disc is rotating, in which case inclines leading in the direction of rotation are advantageously provided which prevent hard insertion of the clutch pins into the locking points and thus increase the safety of immersion without bouncing and reduce wear.

By means of these arrangements (shown on the basis of the exemplary embodiments) it is possible to interrupt the flow of power from the drive motor to the tool when the driver pins leave their seats in the locking positions; however, since the driver pins remain in engagement with the tool or its holder, it is easy to reestablish this flow of force by reinserting the coupling pins into the locking positions, for which a reversal of the axial movement is sufficient. In order to achieve a secure engagement, the detent points are designed as tool-side recesses in the clutch disc, which preferably have lead-in slopes leading in the direction of the rotational movement of the clutch disc. The driver pins can be reinserted into these tool-side locking points. fen if the excitation of the solenoid has ceased without the drive motor having to be stopped; this "spinning" of the drive motor allows the driver pins to find a rest point, the force required for this being provided by the means acting against the working direction of the lifting magnet, which are tensioned when the lifting magnet is excited and which, when de-energized, causes the displacement caused by the latter from the clutch disc or drive pin.

Another embodiment is given in that at least one coupling element is articulated radially movably on the output shaft of the drive motor or the drive shaft of the tool, with each coupling element in the area of the other shaft end having a driving nose for positive and positive locking , However, releasably connecting both shaft ends, and that the drive shaft of the tool or the output shaft of the drive motor has a number of recesses distributed over the circumference, which cooperate with the / the coupling element (s) and with which these are deenergized to produce the power flow in the solenoid Are engaged and can be disengaged when the lifting magnet is excited to separate the flow of force. The locking points are advantageously provided at an angular distance of at most 120 °; In practice, angular distances of 90 ° and 60 ° have proven their worth. To implement the movement, the driving pins / driving lugs are lifted out of the occupied locking points by the radial movement, so that the flow of force is interrupted and the danger - such as injury to the hand or a finger - is averted. This radial movement is achieved in that the lifting magnet interacts with a release ring which surrounds the drive shaft of the tool in a ring shape and whose side facing the end of the output shaft of the motor is beveled in a wedge shape, and in that the ends of the coupling elements lie in the region of this wedge surface are correspondingly bevelled in such a way that when the solenoid is excited, the disengaging ring grips under these ends and lifts them out to release the non-positive or positive connection between the two shafts, the solenoid acting against its working direction Has means which are excited when the lifting magnet is excited and which, when de-energized, cancel the displacement of the driving lug / s caused by them. In this embodiment, the disengagement ring slides under the bevels of the coupling elements, so that they act like an inclined plane to "lift out" the ends of the coupling elements assigned to them, which, as one-armed levers, allow the driving lugs to slide out of the locking points. This transmission ensures that the latching lugs are forced out of the latching points mechanically, so that a reliable separation of the power flow is achieved and the tool comes to rest.

In the case of rotating tools in particular, which may have stored considerable rotational energy, it is advantageous if a braking device which can be triggered by the lifting magnet is provided. Such a braking device is advantageously formed by a brake cross connected to the tool or its holder and a plurality of brake stops connected to the lifting magnet or its armature, which can be pivoted into the rotating circle of the cross when the lifting magnet is excited. These arms pivoted into the turning area block the further turning movement and stop the tool. It goes without saying that these arms as well as those of the brake cross are designed so that they can withstand the maximum forces that occur when braking. For this purpose, the arms of the brake cross and / or the brake stops have a rectangular profile elongated in the direction of rotation; In order to flatten the jerk occurring when striking, they are advantageously provided with elastic buffers in the area of the attachment points.

In order to be able to move the driving pins / driving lugs, the clutch disc or the disengaging member back into their rest position after the safety device has responded, the means acting against the working direction of the lifting magnet is tensioned when the lifting magnet is excited and when it is de-energized this causes displacement of the clutch disc or driver pin, advantageously formed by at least one compression spring; this compression spring is tensioned when the solenoids are excited and releases the energy stored in it when the solenoid is de-energized, the driving pins / driving lugs, the clutch disc or the disengaging member being moved back to the rest position, as a result of which the continuous flow of force is restored . As a compression spring that is tensioned when the magnet is de-energized, such a spring can also support the disengagement movement; this is particularly important when a braking device must also be triggered with the disengaging movement.

The circuit arrangement for this safety device advantageously has a sensor which emits a sensor voltage, which is guided on the one hand to the handle of the hand tool and on the other hand to the moving tool, wherein a sensor detects a current flow between the two outputs has a recognizing element which, in cooperation with a switching element, switches through a circuit for the lifting magnet. In principle, this principle of the sensor is not new; it is used, for example, in elevators to generate signals. Applied to hand machine tools, it allows a conclusion to be drawn between the moving tool and the handle, which usually leads over the body of the user. This detection leads to the switching of the excitation circuit for the lifting magnet, it being basically the same whether the lifting magnet is energized or de-energized in the working position and vice versa in the safety position. Operation is advantageous in that the solenoid is de-energized in the working position and that the driver pins are held in engagement by means of the compression spring. If the sensor detects a body current, the solenoid is excited, it picks up and the power flow interruption occurs.

In order to be able to distinguish a random conclusion from an ongoing conclusion which means a possible danger, a time delay element is connected upstream of the switching element. If the conclusion lasts several pulses, the logic of the switching element assumes that there is a hazard and switches the circuit of the solenoid by. Depending on the mode of operation, this is converted from excitation to excitation or vice versa, and in the process moves either the clutch disc or the disengaging member axially so that the clutch pins slide out of the locking points found, so that the flow of force from the drive motor to the moving tool is interrupted is and this comes to rest quickly if necessary under the action of an additional brake.

In order to reliably prevent the user from being endangered by the sensor voltage, the sensor galvanically isolates the sensor voltage from the mains voltage. A DC voltage is generated, the voltage of which is below a hazard limit voltage; A DC voltage of less than 42 V, preferably around 24 V, is advantageously used. A pulsed voltage with a pulse frequency of at least 0.5 kHz is advantageously provided as the sensor voltage itself. This means a sensor pulse sequence in such a way that the pulse interval is less than 2 ms, whereby it should be noted that the hazard does not reflect the working speed of the tool but the feed rate of the machine reflects the risk of injury. In order to have sufficient detection reliability, the pulses are advantageously designed such that their peak voltage reaches at least 1 kV. This peak voltage is completely harmless for the user of the hand machine tool, since the energy converted in the event of accidental contact is kept small by low (line) capacities. In order to eliminate radio interference, the connecting lines carrying the sensor pulses are designed as shielded lines. The additional line capacities obtained in this way can be kept in such a way that the discharge energy determining a hazard is not raised above a limit, they are too small because of the short line length. This pulse voltage is also for a high-resistance external connection, which is given, for example, when wearing workshop gloves.

The invention is explained in more detail with reference to the embodiment shown in Figures 1 to 10; show:

Figure 01: Safety drive with axially movable clutch disk, schematic;

Figure 02: Safety drive with axially movable release member, release member between clutch disc and tool or its holder, schematically;

FIG. 03: safety drive with axially movable disengaging member, disengaging member outside the tool or its holder and clutch disc, schematically;

Figure 04: Jigsaw with safety drive, front view, cut;

Figure 05: Jigsaw with safety drive, drive engaged, side view, cut;

Figure 06: Jigsaw with safety drive, drive disengaged, side view, cut;

Figure 07: Circular saw with safety drive, drive disengaged, side view, cut ;;

FIG. 08: circular saw with safety drive, drive engaged, side view, cut;

Figure 09: Section through the end of the drive shaft of the tool at the level of the locking point;

Figure 10: Circuit diagram, schematic.

Figures 1 to 3 schematically show the designs with an axially movable clutch disc 10 (Fig. 1), with release member 12 between clutch disc 10 and tool 5 or its holder 4 (Fig. 2) and with release member 12 outside tool 5 or its Holder 4 and clutch disc 10 (Fig. 3). In all three cases, the drive motor 8 (FIGS. 4-8) acts on its output shaft 9, which in turn transmits the rotary movement to the clutch disc 10. This is provided with the locking points 11, in which the driver pins 13 engage. These driver pins 13 are arranged on the tool 5 or their holder 4 in an axially parallel manner so that they lie on the circle assigned to the locking points 11 of the clutch disc 10. In this embodiment, the clutch disc 10 is axially movably guided on the output shaft 9, for which purpose guide grooves 9.1 are provided, so that the lifting magnet 15 axially disengages the clutch disc 10 when excited. can store. The compression spring 14 is tensioned with such an excitation-related shift and ensures that the clutch disc 10 is returned to its original position when de-energized. The driver pin (s) provided on the tool (5) or its holder (4) engages in these locking points (11) or is withdrawn therefrom, so that the power flow is either established or interrupted. The solenoid 15 in FIG. 1 interacts with the clutch disc 10, the clutch disc 10 being axially movable on the output shaft 9, which is also provided with guide grooves 9.1 here. In the other two embodiments, the clutch disc 10 is fixed on the output shaft 9, and it is provided with the / the drive pin (s) 13 release member 12 coaxial with the output shaft 9 so that the drive pins 13 attached to it axially parallel with the Raststel¬ len 11 of the clutch disc 10 can cooperate. 2, the disengaging member 12 is arranged between the clutch disc 10 and the tool 5 or its holder 4 and is moved away from the clutch disc 10 by lifting magnets, so that the protrusions 13.1 of the driver pins 13 from the locking points 11 be lifted. During this movement, a compression spring 14 is tensioned as a restoring element, which, when the lifting magnet 15 is de-energized, brings the release element 12 into its original position and can thus start the flow of force again. 3, disengaging member 12 and solenoid 15 are arranged outside of tool 5 or its holder 4 and clutch disc 10. This arrangement allows driver pins 13 to pass through the tool 5 or its holder 4 onto the clutch disk 10, so that the ends of the driver pins 13 can engage in the locking points 11 of the clutch disk 10, the engagement being canceled by the lifting magnet 15 can be. The compression spring 14 is tensioned when the solenoid 15 is excited, so that the release member 12 is moved back to its original position when de-energized.

FIGS. 4 to 6 show sections through a jigsaw with a safety drive in a front view (FIG. 4) and in a side view, on the one hand the pin coupling is disengaged (FIG. 5) and on the other hand the pin coupling is engaged (FIG. 6). In the view of the machine 1, the housing 2 can be seen with the handle 3, as can the tool 5 shown here as a jigsaw blade. The tool 5 is held by the tool holder 4 and set in motion, with a Shoe 6 arranged under the machine 1 enables the machine 1 to be guided cleanly. The movement is triggered by the drive motor 8, the output shaft 9 of which cooperates with a pin coupling which transmits the movement of the saw blade holder 4. This pin clutch is formed by the clutch disc 10, which is provided with locking points 11, into which the free end of a driving pin 13 engages, which is fastened to an axially movable release member 12. The axial movement of the release member is effected by a lifting magnet 15 which is arranged on the side of the jigsaw facing away from the drive. The machine is guided on the handle 3, which has a sensor electrode 3.1 at a suitable point, which is in an electrically conductive connection with the safety circuit, and on which the skin surface which is free when the machine is operated is supported. The force coupling effecting the pin clutch is formed by the clutch disc 10, which cooperates with the guide pin 13 guided through the holder 4 of the tool 5 and engaging in one of the locking points 11, the driver pin 13 being held by a disengaging member 12 so that it is held by a When the solenoid 15 is de-energized, the pin opening in the holder 4 is axially movable and engages in one of the locking points 11 of the clutch disc 10. When the magnet is excited, the release member 12 is attracted and moves axially away from the clutch disc 10, so that the driver pin 13 is lifted out of the locking point 11 and the flow of force is interrupted.

FIGS. 7 and 8 show another embodiment of the safety device with radially displaceable coupling elements which are designed as (one-armed) coupling levers 16; FIG. 9 shows a section through the end of the drive shaft 7 of the tool at the level of the locking positions 25. These coupling levers are articulated with a joint 16.1 to the end of the output shaft 9 of the drive motor 8 so that they could be pivoted, the driver lugs 17 being radially displaced. The end of the clutch lever 16 opposite the joint 16.1 is provided with a sliding bevel 18, under which the disengaging ring 19 grips, which is guided in guide grooves 19.1 on the drive shaft 5.1 of the tool 5. This acts as an anchor with the solenoid 15, which pulls the release ring 19 when energized and presses it under the sliding slope 18, so that the free end of the clutch lever 16 is raised. The driver lugs 17 follow this lifting, as is customary in the case of a one-armed lever, and slide out of the latching points 25. The clutch is thus disengaged between the output shaft 9 and the tool drive shaft 7. In order to achieve a smooth running of the driver lugs 17 into the latching points 25, they are cut out on one side in the manner of a run-in slope so that this recess is leading in the direction of rotation. When the disengaging ring 19 is tightened, the spring 14, which is tensioned here when the magnet is de-energized, is relaxed, so that it supports the movement of the disengaging ring 19. With this movement of the release ring, the braking device 20 is triggered at the same time.

This braking device 20 - shown here in simplified form for the sake of clarity - is formed by a brake cross 21 fixedly mounted on the shaft 7 of the tool 5, which interacts with brake arms 22 fixedly attached to the lifting magnet. These brake arms 22 are pivotally mounted in a bearing 22.1, which is also fixed to the lifting magnet, and they are pivoted into the rotating circle of the brake cross 21 when the lifting magnet 15 is excited. The brake stops 21.1 provided on the rotating brake cross 21 then interact with the stationary brake arms 22 in such a way that they strike their elastic buffers 23 and are stopped there.

Finally, FIG. 10 shows a schematic circuit diagram of the electronic circuit that triggers the safety device. Via the line L1 provided with the mains switch N1, the mains voltage reaches the device, which is monitored and controlled by a sensor monitoring circuit SÜS. This sensor monitoring circuit gives the voltage via the line L3 to the motor control MS with the speed control DS for the drive motor 8, via the line L2 to the pulse generator II, which generates the voltage for the sensor, in particular the pulses of higher voltage, via the line L6 approaches tool 5. The counter voltage, generally the ground, is conducted via line L5 to the sensor electrode 3.1, on this sensor electrode. A current flow via tool 5 and sensor electrode 3.1 activates the monitoring circuit in the sensor monitoring circuit SÜS and excites the solenoid 15 via the line L4 via the solenoid control HS, which then attracts and the flow of force from the drive motor 8 to the tool 5 by disengaging the clutch interrupts. In order to rule out accidental events that simulate such a conclusion, a delay element is provided in the sensor monitoring circuit, which only releases the actuation of the lifting magnet when at least two pulses or a time corresponding to these two pulses after the first occurrence of the end has passed. In order to also be able to detect high-resistance inferences, the sensor is set to high-resistance external circles.

Claims

claims

01. Safety device for electromotive hand tools, in particular jigsaws and circular saws, in which the power flow from the motor to the tool is arranged via a clutch which is arranged between the two and disengages the direct power flow between the output shaft, the drive motor and the drive shaft of the tool is guided with coupling elements, the coupling elements interacting with a lifting magnet which, by means of an electronic sensor which can be activated when the tool is touched with a body part, disengages the coupling and thus interrupts the connection from the motor to the tool, characterized in that the coupling elements axially parallel and constantly connected to the tool or its holder or drive shaft in a non-positive or positive manner, and that the output shaft of the motor or a clutch disc connected therewith interacts with the tool-side coupling elements Has projections / projections with which they are engaged when the lifting magnet is de-energized to produce the power flow and can be disengaged when the lifting magnet is energized to separate the power flow.

02. Safety device according to claim 1, characterized in that the output shaft (9) of the drive motor (8) has a clutch disc arranged on the motor side of the tool (5), which has a number of locking points (11) arranged in a circle around its center. , at least some of which are designed as drive pins (13) Interacting coupling elements is provided, which constantly form the force transmission element in engagement with the tool (5) via its holder (4) or via its drive shaft, the lifting magnet (15) axially displacing the clutch disc ( 10) / driver pins (12) for disengaging and the driver pins (12) engage at least in some of the locking points (11), and wherein the lifting magnet has means acting against its working direction, which excites when the lifting magnet (15) is excited and which when it is de-energized, remove the displacement of the clutch disc (10) or driver pin (13) caused by them.

03. Safety device according to claim 2, characterized in that the tool (5) or its holder (4) provided with at least one fixedly arranged driver pin (13) or its holder (4) next to the axially displaceable clutch disc (10) is freely rotatable coaxially to the latter is arranged and the driving pins (13) engage in the locking points (A) of the clutch disc (10) in their locking points (11), the lifting magnet (15) and clutch disc (10) interacting such that the clutch disc ( 10) is attracted when the lifting magnet (15) is excited and the driver pins (13) located in the latching points (11) become free.

04. Safety device according to claim 2, characterized gekenn¬ characterized in that with at least one driver pin (13) provided, freely rotatable, between the fixed to the output shaft (9) of the drive motor (8) connected to the clutch disc (10) and Tool (5) or its holder (4), which is arranged coaxially with it and is axially movable release member (12) is provided, which is disc-shaped with a diameter preferably larger than that of the clutch disc (10), and the lifting magnet (15 ) in the area of this protruding circumference with rotational symmetry Field distribution is arranged, in which the driver pins (13) facing the tool (5) or its holder (4) can be axially displaced in the bores of the tool (5) or holder (4), and in which the driver pins (13) are provided with projections (13.1) directed towards the clutch disc (10), which cooperate with the locking points (11) of the axially fixed clutch disc (10) such that the release member (12) is attracted when the solenoid (15) is excited and the driver pins (13) located in the locking points (11) come out of engagement.

05. Safety device according to claim 2, characterized gekenn¬ characterized in that with at least one driver pin (13) provided, freely rotatable, on which the fixed to the output shaft (9) of the drive motor (8) connected clutch disc (10) The side of the tool (5) facing away or its holder (4) is provided with an axially movable disengaging member (12) which is arranged coaxially therewith and is disc-shaped with a diameter at least equal to the diameter of the circle of the locking points (11). , and the lifting magnet (15) is arranged concentrically in the region of the release member (12), in which the axially displaceable driver pins (13) directed towards the tool (5) or its holder (4) are located in the bores of Tool (5) or holder (4) are axially displaceable and interact through the tool (5) or its holder (4) with the locking points (11) of the clutch disc (10) in such a way that the disengaging member (12) Excitation of the solenoid ( 15) is tightened and the coupling pins (13) located in the locking points (11) become free.

06. Safety device according to one of claims 1 to 5, characterized in that the locking points (11) are formed as tool-side recesses in the clutch disc (10), which are preferably in the direction of the rotary motion. 75 PCI7EP96 / 00196

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tion of the clutch disc (10) have leading inlet slopes (11.1).

07. Safety device according to one of claims 1 to 6, for a tool executing a linear movement, characterized in that the disengaging member (12) has a driving pin (13) and the clutch disc (10) has at least one, preferably a number of preferably have evenly distributed locking points (11).

08. Safety device for electromotive hand tools, in particular jigsaws and circular saws, in which the power flow from the motor to the tool is arranged via a clutch which is arranged between the two and disengages the direct power flow between the output shaft, the drive motor and the drive shaft of the tool is guided with coupling elements, the coupling elements cooperating with a lifting magnet which, by means of an electronic sensor which can be activated when the tool is touched with a body part, disengages the coupling and thus interrupts the connection from the motor to the tool, characterized in that at least one coupling element ¬ element (16) is radially movable to the output shaft (9) of the drive motor (8) or the drive shaft (5.1) of the tool (5), each coupling element (16) in the area of the other shaft end a driving nose (17) for positive and positive, jedoc h Detachable connection of both shaft ends (5.1, 9), and that the drive shaft (5.1) of the tool (5) or the output shaft (9) of the drive motor (8) has a number of recesses distributed over the circumference as locking points (25 ) which cooperate with the coupling element (s) (17) in such a way that, when the lifting magnet (15) is de-energized, it engages with them to produce the flow of force and when the lifting magnet (15) is de-energized to disconnect the flow of force are feasible.

09. Safety device according to claim 8, characterized gekenn¬ characterized in that the locking points (25) are provided at an angular distance of at most 120 °.

10. Safety device according to claim 9, characterized gekenn¬ characterized in that the lifting magnet (15) with a drive shaft (5.1) of the tool (5) ring-shaped Ausrück¬ ring (19), the end of the output shaft (9) of the Motor (8) facing side has a wedge surface as a sliding slope (18), cooperates, and that the ends of the coupling elements (16) lying in the area of these sliding slopes (18) are beveled corresponding to it such that when the solenoid (15 ) the disengaging ring (19) grips under these ends and lifts them to release the non-positive or positive connection between the two shafts (5.1, 9), the lifting magnet (15) having means acting against its working direction which, when the stroke is de-energized ¬ magnets (15) are tensioned to support the displacement of clutch levers (16) caused by this.

11. Safety device according to claim 9 or 10, in particular for electric motor-driven hand tools with a rotating tool, characterized in that a brake device (20) which can be triggered by the lifting magnet (15) is provided.

12. Safety device according to claim 11, characterized gekenn¬ characterized in that the braking device (20) is formed by a with the tool (5) or its holder connected brake cross (21) and several with the lifting magnet (15) or its armature connected , with brake stops (21.1) provide brake arms (21) which can be pivoted into the rotating circle of the brake cross (21) when the lifting magnet (15) is excited.

13. Safety device according to claim 12, characterized gekenn¬ characterized in that the radial arms of the brake cross (21) and / or the Bremsaπschlag (22) have a ver¬ elongated in the direction of rotation rectangular profile, and preferably the radial arms of the brake cross (21) and / or the brake stops (22) are provided with elastic buffers (21.1; 23) in the area of the stop points.

14. Safety device according to one of claims 1 to 13, characterized in that the lifting magnet (15) cooperates with a spring (14) which is preferably designed as a compression spring acting against the working direction of the lifting magnet (15).

15. Circuit arrangement for a safety device according to one of claims 1 to 14, characterized in that the handle (3) of the hand tools (1) has a Sensorelektro¬ de (3.1), between which and the moving tool (5) one of a Sensor monitoring circuit (SÜS) generated sensor voltage is present, the opposite voltage, preferably the general ground, is applied to the other part, the electronic sensor monitoring circuit (SÜS) being the link that recognizes a conclusion between the two outputs, the cooperating with a lifting magnet control (HS), switches the circuit for the lifting magnet (15).

16. Circuit arrangement according to claim 15, characterized in that voltage pulses of at least 1 kV are used as the sensor voltage, the repetition frequency of the pulse sequence being in the range from 0.5 to 1.5 kHz.

17. Circuit arrangement according to claim 15 or 16, characterized in that the sensor monitoring circuit (SÜS) has a time delay element which connects a body closure recognized by the sensor with a time delay to the solenoid control (HS), this time delay preferably corresponding to the duration of about 2 periods of the pulse frequency.

18. Circuit arrangement according to one of claims 15 to 17, characterized by the fact that the sensor voltage is galvanically separated from the mains voltage, a sensor voltage generator being provided in the sensor monitoring circuit (SÜS), which primarily generates a rectified low voltage, from which a pulse shaper generates the pulse voltage, the connecting lines carrying the sensor pulses preferably being shielded lines.