EP0091009A2 - Electromechanical overload indicator for electrical appliances using alternating current, especially multiple-outlet boxes - Google Patents

Abstract

In electrical appliances, especially multiple-outlet boxes, there is a risk that users will connect too many loads, and/or loads that are too powerful. Apart from the risk of overheating, this has the consequence that the overcurrent-protection devices protecting the relevant part of the network will trip, as a result of which other important loads in this part of the network, e.g. refrigerators or such like, are also then affected by the disconnection. As a remedy, the invention provides for a low-volume, simple electromechanical acoustic warning device, which can be retrofitted in existing installations, to be inserted in the alternating current flow of, for example, multiple-outlet boxes in such a manner that an electromechanical vibrator (10), which is at least audible and is influenced directly by the current flow if the permissible current is exceeded, is connected to a housing part, e.g. the cover (2). The vibrator (10), which is of particularly flat construction, consists of a soft iron core (16) with a main limb (11) and at least one auxiliary limb (12, 13), furthermore a magnetically connected armature, supported via one or more springs (15'; 15), and of a current coil (22) through which flows the equipment alternating current which is to be monitored. If a particular current level is exceeded, e.g. 16 A, an unmistakable, suddenly-starting tone is produced at double the mains frequency, and is not suddenly silenced again until the current falls significantly below the predetermined limit. <IMAGE>

Description

The invention relates to an electromechanical overload indicator for AC electrical devices, in particular multiple sockets, according to the preamble of claim 1.

A number of electrical devices that are operated with technical AC power are not protected against overload due to excessive current flow. Multiple sockets in particular seduce users by overloading by attaching too many and too powerful consumers. If such a multiple socket is provided with a conventional overcurrent protection switch, it would trip immediately in the event of a surge. In the case of a slight permanent overload, however, such switches are too inert, so that they are only triggered after a certain time delay. This can lead to inconvenience if in such a case important consumers such as Freezers and the like are also affected by the shutdown. A multiple socket can also be destroyed by permanent overload.

It is known to use buzzer as a warning device; for example, an acoustic display of egg boilers should be mentioned. But the known buzzers work voltage-dependent and are therefore less suitable for monitoring a maximum current. They also do not have the desired hysteresis behavior, which means that the warning tone does not jump as desired, but gradually, e.g. starts with slowly increasing current.

The object of the invention is to provide a simple electromechanical warning device against overloading of AC devices, for example multiple sockets, which in the event of an overload performs its warning function without inertia; The actual warning device should be flat and robust against mechanical (e.g. when the device falls) and electrical (voltage peaks) stresses, as well as being resistant to aging. Hysteresis behavior is also desirable. The solution is defined in claim 1.

Essential for the solution according to claim 1 is a particularly flat and relatively space-saving electromechanical vibrator which generates a sudden warning sound as soon as the AC current value permissible for the device to be secured is exceeded. The vibrator used shows good hysteresis behavior, so that the user is not already confused by an early warning tone if the current is close, but still below the limit value. Even with continuous use, there is no danger that the vibrator will be destroyed for mechanical or thermal reasons.

The vibrator can also be retrofitted into a wide variety of AC devices.

In the event of a surge current, the warning device reacts as quickly as an overcurrent protection switch, but in the event of continuous overload, it does so much faster, namely immediately after the overloading consumer is switched on. In this case, an unmistakable acoustic warning signal sounds, which can also be coupled with an optical signal.

In the case of a multiple socket in particular, a warning signal is advantageous in the event of an overload, namely when an additional plug is plugged in, the load of which exceeds the nominal current limit. Due to the warning signal starting immediately, the user notices when the plug is inserted that there is an error; the plug will then be removed again instinctively.

The structure of the vibrator specified in claims 2 to 4 results in the desired flat, robust and age-resistant device with hysteresis properties.

A particularly pleasant use of sound is achieved by the measure according to claim 5.

According to claim 6, it is possible to distinguish between two different current values based on the tone frequency: When the current increases moderately, the vibrator first sounds with its own resonance in order to carry out forced vibrations with a larger current at twice the mains frequency.

The claim 7 shows that the vibrator can also be used, at least as a side effect, as an air-moving and thus cooling fan.

In contrast, claims 8-9 describe, for example, the additional design of an optical (remote) display.

By the measure of claim 15, the device is absolutely foolproof.

Other advantageous embodiments can be found in further claims.

• Fig. 1 die Draufsicht auf die Unterseite des Deckels einer zweiteiligen Steckdosenleiste mit eingepreßtem elektromechanischem Vibrator, in perspektivischer Darstellung,
• Fig. 2 den Einbau des Vibrators zwischen ohnehin vorhandene Verrippungen u.dgl. im Deckel der Steckdosenleiste gemäß Fig. 1,
• Fig. 3 die wesentlichen Bestandteile des elektromechanischen Viorators in perspektivischer Darstellung,
• Fig. 4 den Weicheisenkern mit federnd gelagertem Anker zum Vibrator gemäß Fig. 3,
• Fig. 5 die Strom-Spule zum Vibrator gemäß Fig. 3,
• Fig. 6 einen Weicheisenkern ähnlich Fig. 4, bestehend aus Hauptschenkel, zwei Nebenschenkeln sowie dem zugehörigen Anker, ferner die angedeutete Strom-Spule,
• Fig. 7 die Vibratorteile gemäß Fig. 6 von der Seite gesehen, jedoch ohne Strom-Spule,
• Fig. 8 die besonders flache Ausbildung des Vibrators mit Rechteck-Weicheisenkern und mittig angeordnetem, von der Strom-Spule umgebenem Anker,
• Fig. 9 ein Verdrahtungsschema zur Steckdosenleiste gemäß Fig. 1 und
• Fig. 10 die Hysteresis-Eigenschaften der Überwachungseinrichtung im Kräftediagramm.

The invention is described below using an exemplary embodiment with a vibrator installed in a multiple socket; in the associated schematic drawings:

• 1 is a top view of the underside of the cover of a two-part power strip with a pressed-in electromechanical vibrator, in a perspective view,
• Fig. 2 shows the installation of the vibrator between existing ribs and the like. in the cover of the power strip according to FIG. 1,
• 3 shows the essential components of the electromechanical viorator in a perspective view,
• 4 shows the soft iron core with a spring-loaded armature for the vibrator according to FIG. 3,
• 5 shows the current coil for the vibrator according to FIG. 3,
• 6 shows a soft iron core similar to FIG. 4, consisting of a main leg, two secondary legs and the associated armature, as well as the indicated current coil,
• 7 seen the vibrator parts of FIG. 6 from the side, but without a current coil,
• 8 shows the particularly flat design of the vibrator with a rectangular soft iron core and a centrally arranged armature surrounded by the current coil,
• Fig. 9 is a wiring diagram for the power strip shown in FIG. 1 and
• 10 shows the hysteresis properties of the monitoring device in the force diagram.

Fig. 1 shows the electromechanical overload indicator, for example installed in a multiple socket. In detail, the underside of the cover 2 is shown as a two-part socket strip in a position rotated by 180, that is to say with the inner parts of the strip 1 pointing upwards. In addition to the housing 3 of the cover as a whole, bottoms 4 of the pots 5 for inserting Schuco plugs with bores 6 for passing the plug pins and openings 7 for the protective springs can be seen. The pots 5 are braced against the walls 8 of the lid 2 by ribs 9. The electromechanical, acoustic overload indicator, a vibrator or buzzer, is generally designated 10 here.

As shown in FIG. 2 in particular, it is possible thanks to the extremely flat design of the overload indicator 10 to easily insert it later into an existing housing 3 of a strip 1. In the case shown, the overload indicator 10 is inserted with a press fit between the ribs 9 and the walls of the pots 5. The fixed connection between the overload indicator 10 and the wall areas of the housing 3 is expedient because it thereby acts as a kind of soundboard and thus has a sound-reinforcing effect. For the same reason, it is advantageous to choose the installation site so that housing areas that are as oscillatable as possible are impacted by structure-borne noise.

The lower part of the power strip 1, which among other things receives the "female" plug elements, is - as is generally known - not shown in the drawings. However, it is emphasized that the overload indicator 10, if the installation conditions are more favorable here than in cover 2, it can just as well be installed in the lower part. Thanks to its robustness and freedom from maintenance, the overload indicator 10 is also particularly suitable for power strips that are welded at the factory after assembly or wiring.

From Fig. 3 it can also be seen that the current coil 22 can be pushed as the last step on the middle leg of the otherwise completely prefabricated vibrator, which considerably simplifies the manufacture of the vibrator.

FIGS. 3 to 5 show a perspective illustration of an example of a particularly expedient and production-oriented solution for the actual electromechanical, acoustic overload indicator 10, which will henceforth be referred to briefly as "vibrator". An M-shaped soft iron core 16, consisting of the main leg 11 and at least one secondary leg 12 or 13, is opposed here by a magnetically conductive armature 14 which is resiliently supported by two leaf springs 15. At least one of the legs 11, 12 or 13 is acted upon by a coil 22 which carries the device alternating current to be monitored. Depending on the size of the alternating current flowing through the coil 22, a magnetic alternating flux with a frequency of 50 or 60 Hz (corresponding to the respective mains frequency) arises in the legs and in the armature. Above a certain current, the alternating flow is so great that the armature 14 begins to oscillate at twice the mains frequency.

With increasing current, the amplitude of the armature oscillation increases. When the predetermined nominal current, for example 16 A, is reached, the armature 14 strikes for the first time against a resistance, here the legs 11-13, and suddenly starts a bright humming sound of 100 Hz with corresponding harmonics.

In the present case, seven turns are sufficient for the current coil 22. The response current can be adjusted by increasing or decreasing the number of turns. The number of turns can be reduced in a simple manner by short-circuiting adjacent turns. 5, one or more known intermediate taps 23 can also be provided between the mains-side coil end 20 and the load-side coil end 21. The core can also have an iron shunt for adjustment. In general, however, one will get by in the normal design of devices provided with such overload indicators without this alternative adjustment possibility.

According to the example shown in more detail in FIGS. 6 and 7, the armature 14 can initially oscillate freely and thus inaudibly at twice the mains frequency (100 or 120 Hz). When the current increases further, the armature strikes at least one of the legs 11, 12, 13 for the first time. From this it is reflected mechanically and elastically, and then, once stimulated to vibrate more violently, hit the legs 11-13 again with almost equally vehement shocks, emitting a loud buzzing or humming noise. If the current flowing through the coil 22 increases further, this behavior practically does not change, since the amplitude of the armature oscillation is limited and thus stabilized by striking the legs 11-13. When the current flow is reduced to below the value at which the first anchor stop occurred, the reflective effect of the legs and thus the warning tone effect initially remain obtained, which gives sufficient hysteresis. The sound only stops abruptly when the current falls below a predetermined minimum value.

7 explains in particular the production-technically favorable design of the soft iron core 16 together with springs 15 and anchors 14. As can be seen, main legs 11 together with secondary legs 12, 13 are simply punched out or folded out of soft iron sheet. Armature 14 and springs 15, the latter made of a resilient metal, or the like are by spot welding, riveting. with each other with the _W or calibration iron core fixedly connected. Other fixed connections of these parts are possible.

In this example, the vibrator is only about 30 mm high and about 20 mm wide. The depth 17, without the coil 22, is only about 4 mm. The outer winding diameter of the coil 22 is about 9 mm here. These maximum dimensions, which can be reduced if necessary, clearly show that the vibrator 10 can also be easily retrofitted into existing socket constructions.

Of course, the coil can also be made with a rectangular cross-section and thus flatter.

It is also conceivable that the coil consists directly of a few turns of a phase of the device supply line, which is wound a few times around the middle leg before connection in the device.

In a further simplification, the soft iron core 16 can be designed as a rectangular core 18 punched out of sheet metal, as can be seen from FIG. 8. Here is one of the legs, for example the middle leg kel, spring-mounted by means of spring 15 'and takes over the function of anchor 14'. The armature 14 'passes through the coil 22.

9 shows a wiring example of a power strip equipped with the vibrator. For reasons of simplification, this did not take into account the fact that, in the case of the socket strip explained with reference to FIG. 1, the connection terminals are in the lower part of the socket, but the vibrator is accommodated in the cover according to the example shown there. According to FIG. 9, the end 20 of the current coil to the vibrator 10 is connected to a terminal 30 'in the socket strip. The end 21 lies on the clamp 30 "" which is usual with such strips, so that the total load flows through the current coil 22 in any case.

• wobei F_m die durch den Strom erregte magnetische Kraft und
• F_R die durch den Anschlag vorhandene Reflexionskraft (Impuls) sowie
• F_F die Federkraft bezeichnen.

The mode of operation of the vibrator and in particular its hysteresis behavior is then explained in more detail with reference to FIG. 10: The following applies to the force F acting on the armature during a period of oscillation:

• where F _{m is} the magnetic force excited by the current and
• F _{R is} the reflective force (impulse) due to the stop and
• F _F denote the spring force.

Although all the forces are complex quantities, the hysteresis behavior of the arrangement can easily be explained by the diagram according to FIG. 10. With increasing current, F _{R is} initially zero; F _M + F _F grow until the amplitude of the armature for the the first stop is sufficient (point A in the diagram). From point A, F _{R is} added and the amplitude suddenly swells up to the limit of the stop. If the current drops, FM also drops. Only when FM has dropped by the amount F _R when F _F is assumed to be constant does the audible oscillation cease abruptly, since the amplitude of the armature suddenly drops due to the absence of the reflection forces (point B).

For the vibrator to function properly, it is advantageous, but not necessary, that the resonance frequency of the spring-mass system consisting of spring 15 and armature 14 roughly corresponds to twice the mains frequency.

Under certain circumstances, however, it may also be desirable to distinguish between two current threshold values. If, for example, the natural frequency of springs 15 and armature 14 is set to 50 Hz, the system will initially sound at 50 Hz after the first striking, but with a further increase in current because of the increasing F, it will finally sound at a predetermined current value of 100 Hz. In this case, too, the property of the abrupt use and drop of sound is retained.

As an expedient embodiment, it can be provided that the vibrating part (s) of the system have a cooling effect, e.g. exercises (or exercises) on the power coil or on other parts of a particular device that require cooling. In order to achieve the effect of a "cooling fan", the vibrating parts are expediently designed to be as large as possible. This configuration of the vibrator is primarily suitable for other fields of application than the socket described here.

The same applies to a further advantageous embodiment of the vibrator, which consists in the fact that the current coil also acts as a suppression choke. In such cases, a combination of cooling and interference suppression is particularly advantageous. This configuration can be used primarily with switched or clocked electrical devices.

The particularly flat, space-saving design of the vibrator is always advantageous for all conceivable applications. As a result, the vibrator advantageously differs from all known buzzer types.

Reference symbol list

• 1 power strip
• 2 lids
• 3 housing
• 4 floor
• 5 pot
• 6 hole
• 7 breakthrough
• 8 wall
• 9 rib
• 10 Vibrator electromechanical overload indicator
• 11 main legs
• 12 thighs
• 13 thighs
• 14 anchors
• 14 'anchor
• 15 spring
• 15 'spring
• 16 soft iron core
• 17 depth
• 18 rectangular core
• 20 coil end, mains side
• 21 coil end, load side
• 22 current coil
• 23 intermediate tap
• 24 connecting lines
• 30 line
• 30 'clamp
• 30 "clamp
• 31 line
• 31 'clamp
• 31 '' clamp
• 33 protective earth

Claims (15)

1. Electromechanical overload indicator for AC electrical devices, in particular multiple sockets, with a housing and with devices for supplying and discharging electrical energy
characterized,
that the electromechanical overload indicator connected to a housing part (for example cover 2), which is directly influenced by the current flow, is a vibrator (10) which, when a predetermined current is exceeded, emits at least one sudden warning signal which abruptly stops after the current has clearly fallen below the predetermined value. 2. overload indicator according to claim 1,
characterized,
that the overload indicator (10) consists of a main leg (11) and at least one secondary leg (12, 13), furthermore a spring-loaded (springs 15; 15 ') and reflective and magnetically conductive armature (14; 14') with respect to a soft iron core (16) ) and consists of a current coil (22) through which the device alternating current to be monitored flows. 3. overload indicator according to claim 2,
characterized,
that the soft iron core (16) is M-shaped. 4. overload indicator according to claim 3,
characterized,
that at least one of the legs (eg 11) of the soft iron core (16) is acted upon by the current coil (22). 5. overload indicator according to at least one of claims 1 to 4,
characterized,
that the armature (14; 14 ') together with the spring (15) is designed in terms of vibration for double the mains frequency (100 or 120 Hz). 6. overload indicator according to at least one of claims 1 to 5,
characterized,
that the natural frequency of the spring (15; 15 ') with armature (14; 14') is designed for mains frequency (50 or 60 Hz). 7. overload indicator according to at least one of claims 1 to 6,
characterized,
that vibrating parts (eg 14, 15; 14 ', 15') of the overload indicator are formed over a large area in the manner of a fan. 8. overload indicator according to at least one of claims 1 to 7,
characterized,
that vibrating and stationary parts are electrically isolated from each other and form a pair of contacts. 9. overload indicator according to claim 8,
characterized,
that the contact pair switches a further control device on or off, for example a warning lamp. 10. overload indicator according to at least one of claims 1 to 9,
characterized,
that the coil (22) together with the armature (14; 14 ') are designed as a suppression choke. 11. Overload indicator according to at least one of claims 1 to 10,
characterized,
that the coil (22) is electromagnetically adjustable. 12. Overload indicator according to at least one of claims 1 to 11
characterized,
that the calibration _W iron core (16) for adjusting the on the armature (14; 14 ') acting magnetic force has a magnetically permeable yoke. 13. overload indicator according to at least one of claims 1 to 12,
characterized,
that the vibrator (10) is clamped at an acoustically particularly conductive point of the housing (3). 14. overload indicator according to claim 13,
characterized,
that the vibrator (10) is clamped between ribs (eg 9) of the housing (3). 15. overload indicator according to at least one of claims 1 to 14,
characterized,
that the vibrator (10) is connected in series with a protective element, for example a fuse.

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