DE29707901U1 - Device for the controlled power supply of electrical devices - Google Patents

Description

OTTE & JAKELSKlV * ^: V .··' PATENT ATTORNEYS

PETER OTTE, DIPL.-ING, MASTER IN APPLIED SCIENCES

DR. JOACHIM JAKELSKI, dipl.-phys.

3075G/ot/wi
02 .05.1997

Mr Gerhard Kurz, Industriestrasse, 753 82 Althengstett

Device for the controlled power supply of Electrical appliances

State of the art

The invention is based on a device for the controlled power supply of electrical devices including a separate switch-on function, according to the preamble of claim 1.

For electrical devices, especially hand-held electrical devices such as drills, saws, screwdrivers, etc., which are offered in a wide variety, especially as home devices, it is usual to adapt the power consumed by the electrical device and ultimately delivered to its output shaft to the respective requirements. This is particularly important for screwdrivers, so that appropriate care can be taken when screwing in and also when unscrewing screws.

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To control the power, the so-called phase control circuit is normally used, in which a triac is connected in series with the load, usually the electric motor in handheld electric devices, which switches the mains supply voltage or another DC voltage, also based on a chopped DC voltage provided with the help of batteries, through to the consumer at an adjustable ignition point in the course of a half-wave, which enables effective control of its current consumption.

At the same time, this creates the need to implement a switch-on function for the respective electrical device so that, for example, the power plug does not have to be pulled out every time the operation of the electrical device is to be interrupted.

Devices for controlling the power of electrical consumers that are connected to an alternating voltage, usually the mains voltage, are known in many different forms and usually include the phase control circuit, by means of which the ignition angle of the alternating electrical quantity supplied to the consumer can be adjusted in the desired manner, whereby the power supplied can be regulated.

Such phase control systems are known, for example, from DE 33 03 126 C2, which describes a device for limiting the inrush current in a motor control system for the drive motor of a vacuum cleaner provided with a phase control circuit

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concerns, as well as for example from DE 43 27 070 Cl, in which a device for regulating the power consumption of a vacuum cleaner is described, in which the alternating voltage supplied to the electric motor driving the vacuum cleaner is regulated to a value via a phase control circuit so that it corresponds to the effective value of the motor voltage. The phase control circuits used in each case usually contain a triac, which is connected to the mains in series with the electrical consumer, in this case the electric motor, and supplies the electric motor with a discontinuous (sinusoidal) voltage, depending on the desired power.

If one assumes a circuit for the phase control made up of discrete components, whereby here any highly integrated implementation options up to pure microprocessor control are conceivable and possible, then the phase control in the control circuit for the triac includes a resistance that is usually adjustable as a potentiometer or trimmer and a charging capacitor for igniting the triac depending on the set resistance, so that by shifting the ignition angle accordingly practically any intermediate power up to the full angle can be called up on request.

Especially with handheld electric devices, it is desirable to have the electrical control for the entire functional sequence in the device, i.e. the switch-on function and the controlled power supply via the phase control circuit as space-saving and compact as possible inside the device and from the outside using appropriate operating handles,

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Switches, levers or triggers must be arranged in such a way that they are accessible that the operation of the respective power tool, for example when it is hand-held, can also be controlled with the same hand, which often holds a part of the device that is designed like a pistol grip, for example by using the index or middle finger to operate a trigger switch or trigger lever.

These pushbutton switches are therefore usually designed in such a way that they actuate a separate power switch within the device on a first partial path immediately after actuation, so that the electrical area of the device is supplied with voltage, whereby a so-called accelerator function can then be implemented on the further actuation path, which is used in a suitable way to move a potentiometer ϑ or similar in the control circuit for the triac, so that it is controlled more or less by moving its ignition point.

Such a power switch, which implements the switch-on function in conjunction with an external push button, trigger switch or other sliding lever, is designed to be powerful enough to switch and conduct high currents, as it has to disconnect the entire device from the mains, even at full speed if necessary, and is therefore expensive, and is arranged as a separate component with its own housing at any point in the device or in the area of the circuit board that supports the phase control.

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The invention has the task of significantly simplifying the switch-on function for such electrical devices that are supplied with power by a phase control circuit and, in particular, of significantly reducing the costs for the always-present switch for the power supply.

Advantages of the invention

The device according to the invention solves this problem with the features of claim 1 and has the advantage that the switch provided for the entire switch-on function of the device is removed from the mains area and moved to the control area for the triac of the always present phase control circuit, where the switch is only loaded with drastically reduced currents and therefore requires considerably less effort in terms of structure, materials used, its storage and basic functions. Such a switch is therefore inexpensive to manufacture and can advantageously be stored directly on the circuit board, which also carries the other electrical circuit elements, for example for the phase control circuit.

A further advantage is that the switch components (movable switch lever and counter contact) can be mounted directly on the circuit board, which forms a kind of support housing for the switch, whereby these switch parts are directly mechanically connected to the circuit board and furthermore

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take the opportunity to exploit the possibilities offered by the circuit board for their electrical contacting, namely the connection of these switch components directly to the conductor tracks on the circuit board.

It is thus possible to manufacture the switch in a preferred embodiment of the invention as a simple, appropriately bent metal tongue in the form of a simple stamped sheet metal part, whereby the switch can be easily operated by an external actuating element, which is accessible from the outside of the device housing, being guided over the area of the circuit board on which the switch is located, so that the metal tongue experiences a movement from the actuating element relative to the circuit board when it moves, which can be used to make contact. The metal tongue which mainly forms the switch is in this case mounted on one side of the circuit board and can be bent back by the actuating part when it is displaced to a contact point on the circuit board, whereby this contact point forms the only other component of the switch.

In this respect, the circuit board, since it takes over the storage of the switch components, simultaneously represents the switch housing and preferably also serves as the storage for the actuating element, which is designed in any way possible in such a way that the pressure movement exerted by the operator on the outer end area of the actuating element is converted into a movement of the metal tongue in the direction of the contact point.

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its contacting and thus switching on the gate current to the triac and starting the device.

The mounting for the actuating element on the circuit board can be done by bearings/sliding blocks arranged on both sides of the actuating element on the circuit board, along which the actuating element slides in rail or groove guides, for example, whereby the metal tongue can have a bent-up end area which, when it runs over, is pressed downwards by a cam from the actuating element, in any case in the direction of the circuit board and the contact point, so that contact is made between the metal tongue and the contact point. The small gate current then flows, which in a practical embodiment can be between 50 and 100 mA, compared to the current otherwise flowing in such switches that implement a switch-on function for an electrical device of up to 5 A or more, possibly even much more if chopped direct current has to be switched in a battery-powered low-voltage device.

A further advantage of an embodiment of the invention is that both the switch for the gate current and the setting potentiometer for the ignition angle setting of the phase control circuit are arranged on the same board, so that it is possible to ensure, by means of appropriate kinematic elements or a correspondingly co-directional arrangement of the actuating parts for the switch and potentiometer for the phase control, that the actuating element first actuates the switch and

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switches on the triac and then adjusts the potentiometer accordingly in the extension of its direction of movement, so that by shifting the trigger time for the triac accordingly, the motor power can be adjusted to the requirements, namely increased or reduced. Reducing the motor power beyond a lower threshold value then leads to switching off again, namely opening the switch for the gate current of the triac when the switching tongue is released by the actuating element and springs back into its contact-free starting position.

The measures and features listed in the subclaims enable further advantageous refinements and improvements of the invention.

drawing

Embodiments of the invention are shown in the drawing and are explained in more detail in the following description. They show:
Fig. 1 shows a simplified top view of a possible circuit board shape with circuit elements mounted on it, including a metal tongue for the realization of the switching function, together with other components;

Fig. 2 in a greatly enlarged detail in side view a possible embodiment of the mounting of the metal tongue on the circuit board in connection with a possible actuation, i.e. effecting a contact

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the metal tongue by moving an actuating element;

Fig. 3 in a view from behind the metal tongue as the main component of the switch with lower extensions for fastening to the circuit board and simultaneous contacting of circuit board conductor tracks and

Fig. 4 shows a possible circuit example for a phase control circuit of basically known construction, but with the switch arranged in the control circuit for the triac.

Description of the embodiments

In Fig. 1, a circuit board 10 is shown, which can be designed in any shape and dimensions and supports electrical circuit components, which do not need to be discussed in detail, since these can be components of known phase control circuits for electrical devices and the like. An electrically conductive, resilient metal piece is mounted directly on the circuit board, which is referred to below as metal tongue 11 and is a component of a switch Sl, the structure of which is completed by the presence of a contact point 12 that is also electrically conductive and therefore preferably metallic. Metal tongue 11 and contact point 12 are mounted directly on the circuit board 10, as can also be seen from the side view of Fig. 2, so that the circuit board is a housing component of the switch Sl, with the metal tongue, which for example

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, which can be made of a suitable elastically springy copper or brass alloy, has an elongated extension and is mounted with one end region on the circuit board 10, while the other end freely projects at a distance from the circuit board and thus also from the contact point 12, so that the switch S1 thus formed is open, as also shown in Fig. 2 in solid lines.

In detail, the metal tongue 11 can be designed in such a way that, starting from the contact point 12 and extending above it, a longer section is initially provided which is kept at a distance from this contact point and from the circuit board, which is then bent diagonally downwards towards the circuit board, extends again along the circuit board by a shorter section and then breaks through the circuit board with one or two bent legs 11a, 11b, so that the end areas of the legs 11a, 11b on the circuit board side of the circuit board - in Fig. 1 the component side can be seen in plan view - become visible after being pushed through, where they are connected to one or more conductor tracks, namely by an appropriate soldering process, for example dip soldering, which simultaneously results in a secure fixation of the entire metal tongue.

In the same way, the contact point 12, for example designed as a small rivet with a rounded head pointing upwards, is connected to other conductor tracks on the conductor track side, for example by dip soldering. A switch of simple form formed in this way cannot and does not need to carry high currents, since it,

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as already mentioned at the beginning, is only arranged in the control circuit of the triac and thus switches its gate current, which then leads to the control of the triac TC (see Fig. 4) and thus to the connection of the load, which is shown as a resistor RL (alternatively) or as a motor in Fig. 4, to the mains connection terminals Nl, M2.

In this context, it can be pointed out that the switch Sl in the control circuit for the triac TC is preferably in series with the RC element for the time delay of the trigger pulses for the triac, i.e. in series with the potentiometer Pl and the capacitor C, from whose connection point the trigger pulses are fed to the gate of the triac TC via a diac Dl and another series resistor Rl. However, it is also possible to place the switch as Sl' directly in the control line to the gate, which branches off from the connection point of the capacitor C with the potentiometer Pl.

A preferred embodiment of the invention is that the actuating element for the switch movement, which is designated 14 in Fig. 2, is also expediently mounted on the circuit board 10, or at least is held so that it can slide, so that a corresponding alignment with the metal tongue 11 and thus with the actuation of the switch Sl, Sl' can be achieved. The actuating element can have a cam sliding section 14a adapted to the shape of the switch, which, when the actuating element moves linearly transversely in the direction of arrow A (Fig. 2), i.e. along the surface of the circuit board 10, is oriented towards the

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middle bevel lic of the metal tongue 11 and presses its front part downwards along the direction of arrow B (Fig. 2) so that, as the dashed line shows, contact is made between the metal tongue and the contact point 12, which at the same time means a contact connection between the conductor tracks of the circuit board soldered to these two connection points, so that the switch Sl, Sl' in the circuit diagram in Fig. 4 is closed.

To guide the actuating element 14 along the circuit board 10, guide blocks 15a, 15b can be provided on both sides of the switch tongue, which are only indicated schematically in the drawing and hold the actuating element, for example, by means of grooved sliding guides. The switching movement of the actuating element is then carried out by a suitable push button switch, push button or trigger lever from outside the device, so that a rear part of the operating element 14a extends outwards through a corresponding device housing opening, which a user's finger grips. At the same time, it is possible to arrange potentiometers or the like on the circuit board. to be laid out in such a way that the actuating element 14 also takes over the adjustment of the potentiometer - since any design form is possible here, depending on the application, shape of the circuit board and potentiometer used (linear potentiometer or rotary potentiometer), which in this respect lie within the scope of expert knowledge, such designs do not need to be discussed further.

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It makes sense for a return spring to act on the actuating element 14, which returns it to its original position when released by the user's finger, i.e. at least after the actuating pressure is removed, so that the metal tongue can also return to its original starting position above the contact point 12, the switch is separated again and the device is switched off by blocking the triac. No further current then flows through the load.

Claims (1)

3075G/ot/wi 14 02.05.1997 Mr Gerhard Kurz, Industriestrasse, 75382 Althenqstett Protection claims 1. Device for the controlled power supply of electrical devices including a switch-on function, in particular of electrical handheld devices with an associated phase control circuit, in which an electrical circuit element (triac) that switches in both directions of the alternating supply voltage is arranged in series with the consumer, characterized in that a) a resilient metal tongue (11) that implements the switch-on function is attached to the circuit board (10), that b) the other end of the metal tongue (11) protruding from the circuit board is arranged in the contact path area of a contact point (12) also attached to the circuit board (10), that c) both mechanical bearing connections of metal tongue (11) and contact point (12) on the board simultaneously form electrical contacts with conventional conductor tracks on the back of the board, whereby 4. ·♦· 3075G/ot/wi 15 02.05.1997 d) these contacts lead to connection points in the control circuit of the triac (TC) of the phase control circuit that controls the current flow through the load (M, RL) in such a way that the contact caused by a movement of the metal tongue supplies the load with correspondingly high currents via the now switched-through triac, depending on the setting, while at the same time a very low current flow via the switch (Sl) in the triac control circuit consisting of the metal tongue (11) and contact point (12). 2. Device according to claim 1, characterized in that the switching tongue (with projections) is arranged in the displacement path of an actuating element (14) in such a way that a displacement movement of the actuating element (14) causes contact between the metal tongue end and the contact point (12), whereby the actuating element (14) is also mounted on the circuit board (10), but at least its movement sequence for actuating the metal tongue is guided on the circuit board. 3. Device according to claim 1 or 2, characterized in that the resilient metal tongue (11) of the switch (S1) on the circuit board is bent upwards from its one mounted end at a distance from the circuit board and that the actuating element (14) also mounted on the circuit board has a cam-like track corresponding to the bend in such a way that in the case of a relative displacement of the actuating element · 3075G/ot/wi 16 02.05.1997 element (14) to metal tongue (11) when the user applies a switch-on pressure the bent part (lic) of the metal tongue (11) is overrun by the actuating element (14) and thereup the other outer end region of the metal tongue contacts the contact point (12). 4. Device according to one of claims 1 to 3, characterized in that a potentiometer determining the trigger time of the triac via an RC element in the control circuit on the board (10) is mounted in such a way that it undergoes a simultaneous (further) adjustment via the movable actuating element (14) after the latter has initially caused the switch (S1) to make contact. 5. Device according to one of claims 1 to 4, characterized in that the metal tongue (11) and contact point (12) consisting of switches on the circuit board in series with the RC element (Pl, C) in the control circuit of the triac (TC) or in the line from the connection point of the RC element to the gate of the triac (TC).