EP1563962B1 - Safety activation device for an electric tool - Google Patents

Abstract

The tool has a control unit generating inoperative, working and intermediate modes of a motor. The motor is out of operation in the inoperative mode, driven for driving a tool (20) in the working mode, and activates a signal generator to create a signal in the intermediate mode. The signal indicates that activation of a switching unit is needed for transferring the motor into the working mode.

Description

The invention relates to a power tool with a motor for driving a tool, with at least one switching element for actuating the motor, which is coupled to a control device, wherein the control device is designed such that a switching on of the motor for driving the tool is only possible when the at least one switching element is repeatedly activated in a predetermined manner or at least two switching elements are activated simultaneously or in a predetermined manner in succession, wherein at least three operating states are provided, a resting state in which the engine is out of operation, a working state in which the Motor is driven to drive the tool, and an intermediate state in which is signaled that for the conversion to the working state further activation of a switching element is required.

Such a power tool is from the US 2003/0196824 A1 known.

In the known power tool is a controlled by a microprocessor power tool in which can be set with the help of various input options numerous different modes of operation. This includes, among other things, a safety mode in which the engine only starts if a security code has been entered previously.

From the DE 101 41 161 A1 It is also known to use optical switches for controlling power tools. In this case, a plurality of optical switches, which essentially function in the manner of a light barrier, may be provided in miniaturized form at a plurality of locations of the power tool, without having to take special measures for touch safety for this purpose. Since the control and evaluation of the switching signals takes place only via optical fibers, namely, the switching elements can be arranged at almost any point of the power tool without protective measures against the mains voltage must be taken. In this way, it is possible to produce ergonomically significantly improved power tools with a plurality of switching elements, which are preferably actuatable by means of resilient, elastic touch surfaces. In order to enable a switching on of the motor, it can be provided that for this purpose at least two switching elements must be actuated simultaneously.

However, in principle, there is the possibility that the power tool is operated accidentally, since the individual switching elements can be easily activated via elastic touch surfaces and as an activation of the individual switching elements is not readily apparent.

The invention is therefore based on the object to improve a power tool according to the type mentioned in such a way that even with the use of very easily activatable switching elements for engine control high reliability is guaranteed and in particular a protection against unintentional switching is made.

This object is achieved in a power tool according to the aforementioned type in that the control device is designed such that the motor in the intermediate state periodically voltage pulses of short duration are supplied to signal a user the intermediate state by movement pulses of the tool.

The invention is completely solved in this way.

According to the invention namely a deliberate switching on the power tool is effectively enforced by the one to start the engine in the working state, the previous operation of at least two switching elements in a predetermined manner or the operation of a switching element is repeatedly required in a prescribed manner. If this does not happen, then the power tool initially goes into an intermediate state, which is signaled to the user by short movement pulses of the tool, which indicates to the user that further activation of a switching element is necessary to put the power tool in the working state. Thus, if, for example, a switching element is only activated at random, for example if the machine still has connection to the mains voltage and is stored, the user is immediately informed that a further activation of a switching element can bring about a transfer to the working state. Similarly, if, for example, the machine is being handed over from one user to another user, or if a child touches the power tool and accidentally activates a switching element, then the danger that is present in the intermediate state is that further activation a switching element can cause the machine to start, made clear.

This significantly reduces the risk potential.

For signaling to a user that the power tool is in the intermediate state, all conceivable and suitable signal means can additionally be used. For this purpose, the power tool may have approximately acoustic, optical and / or haptic signaling means. For example, the power tool can be equipped with a buzzer or a beeper, which signals the intermediate state. Further, optical signaling means, such as LEDs or the like, may be used to indicate the intermediate state.

According to a further embodiment of the invention, the control device is designed such that for switching on at least one or more switching elements within a predetermined time frame must be activated several times.

This also improves the reliability. Namely, since a certain time window is given, within which the multiple activation of a single or multiple switching elements is necessary, the risk of unconscious switching on the engine is further reduced, since even after a short time, for example after a few seconds, also a further activation of a switching element does not lead to the transition to the working state. Rather, this must first be done for this purpose, a deactivation of all switching elements and then a renewed activation are made.

According to a further embodiment of the invention, the control is designed such that the intermediate state, a transition to the idle state takes place, if not carried out within a predetermined time frame, a transfer to the working state by activation of a switching element in the predetermined manner.

As a result, the reliability is further improved because automatically in the intermediate state after failure of activation to return to the working state, a return to the idle state.

According to an advantageous embodiment of the invention, the switching elements are designed as a button.

According to an additional development of the invention, the switching elements are designed as optical switches or as microswitches which can be activated via elastic touch surfaces.

In this way, the switching elements can be miniaturized and arranged at the ergonomically particularly favorable locations of the power tool.

In an additional embodiment of the invention, the switching elements can be activated by grasping a housing of the power tool or a handle of the power tool.

In this way, a particularly ergonomic design of the power tool is made possible.

In a preferred development of the invention, the control device is designed in such a way that, when the two switching elements are activated in real time, the motor immediately changes from the idle state into the working state. Preferably, a front and a rear touch surface must be operated for this purpose.

In this way, a quick start of the engine is made possible in a conscious switching.

It is understood that the features of the invention mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the invention.

Fig. 1

eine Aufsicht eines erfindungsgemäßen Elektrowerkzeuges, das als Winkelschleifer ausgeführt ist und

Fig. 2

eine vereinfachte Schaltung des Elektrowerkzeuges gemäß Fig. 1.

Further features and advantages of the invention will become apparent from the following description of a preferred embodiment with reference to the drawings. Show it:

Fig. 1

a plan view of a power tool according to the invention, which is designed as an angle grinder and

Fig. 2

a simplified circuit of the power tool according to Fig. 1 ,

In Fig. 1 an inventive power tool is shown in the form of an angle grinder and generally designated by the numeral 10.

The power tool 10 has an elongate, approximately rod-shaped housing 12, at one end of a gear head 14 is provided, on the underside of a protective hood 16 is received. At the outer end of the outwardly projecting from the gear head 14 drive shaft, a receptacle for receiving a tool 20 in the form of a grinding wheel or cutting disc is provided. Left or right on the gear head 14, a handle handle 18 may be screwed, as from Fig. 1 can be seen.

The region of the housing 12 symmetrical with respect to its longitudinal axis, which adjoins directly to the gear head 14, is tapered on both sides to form a grip region, on which the housing 12 is easily grasped with one hand and the thumb on one side and of the others Fingers on the other side can be easily held. In the tapering region of the housing 12, which adjoins the gear head 14, there are two elastic touch surfaces on the left and right side of the housing, namely a first elastic touch surface 22 on the left side of the housing and a second elastic touch surface 24 on the right side of the housing. At the end opposite the gear head 14 (approximately in the outer third of the housing 12), a further two-sided taper of the housing is provided. In the tapering area further tactile surfaces are provided on the left side of the housing and the right side of the housing, namely a third touch surface 26 on the left side and a fourth touch surface 28 on the right side.

About the touch surfaces 22, 24, 26, 28 respectively assigned switching elements can be actuated.

A simplified basic circuit of the power tool 10 is shown in FIG Fig. 2 shown.

An electric motor 40 in the form of a universal motor is connected via a power control element 44 in the form of a thyristor to a voltage source, which in the present case is the mains voltage of 230 V alternating current at 50 Hz. The power control element 44 or the thyristor becomes controlled by a control device 42, which is preferably a microprocessor control.

Via the touch surfaces 22, 24, 26, 28 suitable switching elements are controlled, which are connected to the control device 42 (in Fig. 2 only the touch surfaces 22 to 28, but not the switching elements controlled over it are shown).

The control device 42 is now designed so that there are three operating states for the motor 40, an idle state in which the power control element 44 is fully disabled, a working state in which the power control element 44 is periodically turned on at least so far that a continuous rotation gives the motor shaft, while a speed control is enabled, and an intermediate state, whose function will be explained in detail below.

To prevent inadvertent starting of the motor 40, it is necessary in the present case that at least one of the front touch surfaces 22, 24 and at least one of the rear touch surfaces 26, 28, and thus the associated switching elements, are activated simultaneously. If only one of the touch surfaces 22, 24, 26, 28 activated, which can be done by simply grasping by hand, the power tool 10 first enters the intermediate state.

In the intermediate state, the motor receives 40 periodic voltage pulses, each leading to a short start of the motor shaft. For example, the thyristor 44 could be driven in each case for a period of 3 ms, which is at a mains frequency of 50 Hz in a full-wave control corresponds to a phase angle α = 60 ° in a half-wave. Thereafter, for example, could be a complete block over 200 ms or over a longer period of eg 500 ms, before the motor 40 is driven again. As a result, this leads to a brief start of the motor shaft, followed by a standstill, followed by a restart, etc. This results in an intermediate state, which can also be referred to as "tacking" vivid. While no operation can take place in this intermediate state, is signaled by the brief periodic startup of the motor shaft and the driven tool 20, followed by the standstill, a user of the power tool both visually and acoustically, as well as tactile that the power tool in Intermediate state is located. If, in addition, one of the other touch surfaces is activated at the same time, that is to say, for example, when the two front touch surfaces 22, 24 are additionally activated with the second hand, one of the rear touch surfaces 26, 28, the power tool 10 changes from the intermediate state into the working state, in FIG the motor 40 is driven continuously. If, however, no further activation of other touch surfaces and the housing 12 is released again, the power tool 10 automatically goes into hibernation.

Once the power tool 10 is in the working state, it is sufficient to permanently activate one of the touch surfaces 22, 24, 26, 28 in order to maintain the working state.

Although in the working state, the power control element 44 a periodic blocking or partial blocking of the AC voltage caused, this is done in the working state only to control the speed of the electric motor 40. For this purpose, usually only a part of a full wave is cut off both in the positive and in the negative range. Overall, however, the electric motor 40 is continuously driven during successive voltage waves in order to ensure a continuous running of the motor 40. In contrast, the control of the electric motor 40 in the intermediate state takes place only over part of a half-wave, whereupon in turn followed by a complete blocking over a plurality of wavelengths

Regardless of whether first one of the front touch surfaces 22, 24 or one of the rear touch surfaces 26, 28 is activated, the intermediate state is initiated upon initial activation of a touch surface. For the transition to the working state then one of the other touch surfaces must be additionally activated. If, for example, one of the front touch surfaces 22, 24 is initially activated, the activation of at least one of the rear touch surfaces 26, 28 is necessary for the transition to the working state. If, conversely, at least one of the rear touch surfaces 26, 28 is activated, the subsequent activation or simultaneous activation of one of the front touch surfaces 22, 24 is necessary for the transition to the working state. If at the same time one of the front touch surfaces 22, 24 and one of the rear touch surfaces 26, 28 is activated, the power tool immediately goes into the working state, and the motor 40 starts. A "Tackern" does not take place.

In addition, the power tool 10 is still provided with an external speed control, via which the setpoint speed of the electric motor 40 can be adjusted in the working state. For this purpose, when the motor 40 is running (in the operating state), a touch surface 32 on the gear head must be actuated and at the same time one of the touch surfaces 22, 26 on the left side of the housing or one of the touch surfaces 24, 28 are actuated. An activation of one of the touch surfaces 22, 26 on the left side of the housing leads to a speed reduction, while an activation of a touch surface 24, 28 on the right side of the housing leads to an increase in speed. Upon release of the touchpad 32, the current speed value is stored. Even after standstill and subsequent restart of the electric motor 40 of the stored target speed value is maintained. This can be made visually recognizable via an indicator element 30, which is provided for example with three LEDs.

It is understood that, apart from the "tacking" described in the embodiment, any other indications can be used to indicate to the user the presence of the intermediate state. For example, a buzzer could be actuated, an optical indicator activated, or the like.

However, the described motor tacking in the intermediate state is particularly suitable for making a user clearly aware of the presence of the intermediate state both visually and acoustically, the intermediate state being additionally felt simultaneously by the motion impulses of the motor.

Claims (8)

1. An electric power tool comprising a motor (40) for driving a tool (20), comprising at least one switching element, coupled with a control system (42), for actuation of the motor (40), the control system (42) being designed so that the motor (40) can be switched on for driving the tool (20) only when the at least one switching element is activated several times in a predetermined way, or when at least two switching elements are activated simultaneously or in a predetermined way in succession, there being provided at least three operating modes, namely an inoperative mode, in which the motor (40) is out of operation, a working mode in which the motor (40) is driven for driving a tool (20), and an intermediate mode, in which the user is signaled that further activation of a switching element is needed for transferring the motor to its working mode, characterized in that the control system (42) is configured for supplying periodic voltage pulses of a short duration so as to signal to a user that the tool is in its intermediate mode by generating a series of short motion pulses of the tool.
2. The electric power tool of claim 1, further comprising an additional acoustic, optical and/or haptic signaling means for signaling to the user that the power tool (10) is in its intermediate mode.
3. The electric power tool of any of the preceding claims, wherein the design of the control system (42) is such that for transferring the tool to its working mode at least one or more switching elements must be actuated several times within a predetermined timeframe.
4. The electric power tool of any of the preceding claims, wherein the design of the control system (42) is such that when the motor is not transferred to its working mode by activation of a switching element in the predetermined way within a given timeframe, it is automatically transferred from its intermediate mode to its inoperative mode.
5. The electric power tool as defined in any of the preceding claims, wherein the switching elements take the form of pushbuttons.
6. The electric power tool of claim 5, wherein the switching elements are configured as optical switches or as micro switches that can be activated via elastic touch areas (22, 24, 26, 28).
7. The electric power tool of claim 5 or 6, wherein the switching elements can be activated by the act of grasping a housing (12) of the power tool or of a handle of the power tool.
8. The electric power tool of any of the preceding claims, wherein the design of the control system is such that activation of two switching elements in short succession will directly transfer the motor (40) from its inoperative mode to its working mode.

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