WO1989001718A1

WO1989001718A1 - Protective switching device for electrical appliances

Info

Publication number: WO1989001718A1
Application number: PCT/CH1988/000135
Authority: WO
Inventors: Herbert Wirth
Original assignee: Weber Ag, Fabrik Elektrotechnischer Artikel Und Ap
Priority date: 1987-08-14
Filing date: 1988-08-10
Publication date: 1989-02-23
Also published as: AU2134288A

Abstract

A protective switching device for electrical appliances, in particular household appliances, has at least two current-carrying leads (L1', L2') and a spring-loaded switch (6) which can be switched off by a remote-controlled trip element (9). A single electrode (7) lodged in the housing (2) of the electrical appliance is normally electrically insulated from the current-carrying parts inside the appliance (1). In the event of a fault, the current in said parts flows through the electrode (7). An electric lead (S) connects the electrode (7) directly to one of the current-carrying leads (L1', L2') via the trip element (9).

Description

Protective switching device for electrical devices

Technical field

The invention relates to a protective switching device for electrical devices, in particular household appliances, according to the preamble of patent claim 1.

State of the art

Such a protective device is known, for example, from EP-B-0088390. The protective device described there is intended to protect the operator in electrical household appliances, for example a hair dryer, against dangerous body currents which would arise when wetted with water, in particular dropping into a filled bathtub . The protective device consists of an electronic circuit, an electrical, self-opening switch and a contact protection grille which has electrically conductive strips which form a type of double conductor. The electronic circuit is a diode bridge circuit, on the diagonal of which there is a thyristor with a resistor connected in series. The ignition circuit of the thyristor is formed by the contact protection grille, which is arranged inside the housing of a household appliance, for example a hair dryer. The resistor forms a releasable locking of the electrical switch. It consists of a protective wire that holds the switch in the switched-on state via a yoke. When water causes the thyristor to ignite on the contact protection grid, it flows through the fuse wire Tripping current so that the fuse wire burns out and the switch is turned off. Switch-off times of approximately 1.3 msec are mentioned. In another variant of the protective device, a conventional resistance element is provided which holds the yoke in place by means of an adhesive. Switch-off times of approximately 1 msec are allegedly achieved here. In this variant, the triggering time is strongly dependent on the adhesive used and on an even application of the adhesive. The above-mentioned protective device is quite complex because of the electronic circuit with a thyristor. Precise production is also required in order to achieve reliable and equivalent release times, especially in the second variant with an adhesive. The protective device described has many electronic components and electrical connections and can therefore no longer be installed in a small, handy connector. If components fail undesirably, protection is no longer guaranteed. This means that the protective device only switches off in special cases. In addition, it cannot be determined from the outside whether the protective device is still functional.

Presentation of the invention

The object of the invention is now to obtain a protective switching device of the aforementioned type which is inexpensive, reliable and compact and can be accommodated in a small connector plug of the household appliance without any problems.

This object is achieved in a protective switching device of the above type by the features of patent claim 1.

Preferred embodiments of the invention are characterized in the dependent claims. The invention has the great advantage that the protective switching device does not require any electronic components, can be installed in the connector plug and enables a very compact design. Since only very few mechanical components are required and no electronic components are used, the price of the new protective switching device is considerably lower. If an electrically insulating slide is pushed between the contacts of the self-closing switch, the design can become even more compact. But the solutions with self-opening contacts are also very compact, since the switch contacts are arranged parallel to each other, ie very space-saving. The connector pins also form the fixed contacts of the switch. The other switch parts are also aligned as far as possible in the longitudinal direction of the connector housing.

Brief description of the drawings

Further advantages result from the description below. There, the invention is explained in more detail with reference to several examples shown in the drawing. It shows:

1 shows the basic circuit diagram of a protective switching device,

FIG. 2 shows a variant of the circuit diagram of FIG. 1

3 shows the basic circuit diagram of a reclosable protective switching device with test button,

4 shows a first protective switching device installed in a connector, 4a shows a section along the line AA in Fig. 4,

4b shows a section along the line B-B in Fig. 4,

5 shows a second protective switching device installed in a connecting plug,

5a shows a section along the line A-A in Fig. 5,

5b shows a section along the line B-B in Fig. 5,

6 shows a third protective switching device installed in a connecting plug,

6a shows a section along the line A-A in Fig. 6,

7 shows a fourth protective switching device installed in a connecting plug,

7a shows a section along the line A-A in Fig. 7,

8 shows a fifth protective switching device with reset button and test button installed in a connector,

8a shows a section along the line A-A in Fig. 8,

9 shows a sixth protective switching device with a magnet system which triggers in the event of a malfunction as a trip element, installed in a connecting plug, and

10 shows a seventh protective switching device with a magnetic system dropping out in the event of a fault as a trip element, installed in a connecting plug. In the figures, the same reference numbers are used for the same elements.

Ways of Carrying Out the Invention

1 shows the basic circuit diagram of a protective switching device for an electrical household appliance, for example a hair dryer. Its live parts 1 are housed in an electrically insulating housing 2 (protection class II) and connected to the electricity network 5 by means of a three-wire cable 3 via a connector 4. The connections L, and L ₂ are connected via a switch 6 to the current-carrying leads L, 'and L ₂ ' of the cable 3. A third lead S leads to an electrode 7, which is normally arranged electrically separated from the current-carrying parts of the hair dryer. The electrode 7 is attached, for example, in the form of a protective grid on the inside at exposed points of the hairdryer. The switch 6 is provided with a trigger mechanism 8 and a trigger 9. The third lead S is now electrically connected to one of the two leads L 'or L ₂ ' via the trigger 9. However, this connection can also be made to one of the connections L or L ₂ (dashed line). In the event of a shunt between one of the current-carrying parts of the household appliance 1 and the electrode 7, it can be assumed that the electrode 7 absorbs half the voltage potential between the two leads L, 'and L ₂ '. Accordingly, it is irrelevant whether the third lead S is connected to the lead L, 'or L ₂ '.

The trigger 9 will therefore respond in any case and switch the switch 6 off via the trigger mechanism 8. The tripping times depend on the response characteristic of the trigger 9. 2 shows an alternative to the above type of connection. This is the case when the electrode 7 is only partially wetted with water and the voltage potential between the electrode 7 and the supply line L ₂ 'is not sufficient to trigger the switch 6 (FIG. 1). The third lead S is connected here via the trigger 9 to the cathodes of two diodes D, and D ₂ . The anode of the diode D- is connected to the supply line L. 'and the anode of the diode D- is connected to the supply line D ₂ . If the electrode 7 is now insufficiently wetted to achieve the required voltage potential with the lead L ₂ ^f , a sufficiently high potential is formed for the lead L-, '. The trigger 9 will therefore respond in any case.

3 shows an expansion of the circuit in FIG. 1 with a reset button 10 and a test button 11. The reset button 10 can be provided in cases where the trigger 9 is ready for operation again after a malfunction. The test button 11 belongs to a single-pole switch 12 (button) which connects the supply line L-, 'via a series resistor R to the third supply line S. It goes without saying that this extension can also be seen in the variant according to FIG. 2.

4 shows a first embodiment of the protective switching device. It shows an opened connector housing 13 in a top view and partially in a sectional view. The ends of the leads L, ', L ₂ ' and S are each provided with a clamping socket 14, which is in each case attached to a flat plug pin 15. The plug pin 15 of the supply line L 'is formed on the left in the plug housing 13 on an elongated connecting piece 16. At the right end of the connecting piece 16, an outwardly bent leaf spring 17 is welded, which presses against the inside of the power plug L-. The plug pin 15 of the Lead L ₂ 'is formed on a similar connector 18, at the right end of which an outwardly bent leaf spring 19 is welded. This leaf spring 19 also presses against the inside of the power plug L ₂ . The plug pin 15 of the third lead is welded to a small connector 20. The connecting pieces 16, 18, 20 are arranged in a stationary manner by means of guides in the plug housing 13. To the left of the connecting piece 20 is a slide 21, which consists of a base plate with four upstanding ribs. The two outer ribs are pointed to the left and attached on the outside with a T-shaped part. A compression spring 22, which is supported against a cam 23 in the plug housing 13, is pushed over the middle leg of the T-shaped part, which points to the right side of the housing. On the left side of the slide 21, a pin 24 is fastened in the middle and parallel to the ribs. A fuse wire 25 is pinched at its ends by the ends of the connectors 16 and 20 and passed around the pin 24. The fusible wire 25 thus prevents the slide from moving to the left. The compression springs 22 and the thickness of the fusible wire 25 are dimensioned in such a way that mechanical stresses such as impact or impact do not lead to the wire being destroyed. The slide 21 is made of an insulating material such as polyamide and, in the event of a fault, is pushed to the left between the leaf springs 17, 19 and the mains plug L,, L-. A contact distance of 1 to 2 mm is therefore sufficient for perfect electrical isolation. The connector housing 13 is very compact due to the space-saving and longitudinally aligned parts of the protective switching device.

Further details of the protective switching device can be seen from FIGS. 4a and 4b. The power plug L, and L ₂ are flat, but can also be round ^" . 5 shows a second embodiment of the protective switching device. An open connector housing 13 is also shown in a top view and partially in a sectional view. In contrast to the above shape, the leaf springs 17 and 19 are flat and fastened on the connecting pieces 16 and 18 in such a way that the spring force acts outwards. The ends of the leaf springs 17 and 19 are slightly curved outwards. Instead of a slide, a slide clamp 26 is provided, which press the bellow springs 17 and 19 against the outer sides of the connector L, and L ₂ . For this purpose, the sliding clamp 26 encompasses the leaf springs 17 and 19. A large compression spring 27 is enclosed in a blind hole in the sliding clamp 26 and is supported against two cams 28 in the plug housing 13 (shown in part by broken lines). The functionality of this variant is the same as before. 5a shows further details.

A third embodiment is shown in FIG. 6. In this variant, the third feed line S is connected to the connection ₂ (see dashed line in FIG. 1). The mains plugs L. and L _y are arranged transversely to the longitudinal direction of the plug housing 13 (in the illustration in FIG. 6 they protrude into the plane of the drawing). In this case, the leaf springs 17 and 19 are welded to the mains plugs L and L ₂ . The contacts are then on the right side of the connector housing 13. The connecting pieces 16 and 18 are provided with contact surfaces at the appropriate place. An elongated, diamond-shaped rotating part 29 is rotatably mounted on the right side by means of a rotating cam 30. Two switching pins 31 are arranged transversely to the longitudinal direction of the rotating part 29 at the opposite corners. The switching pins 31 press up against the leaf springs 17 and 19 and when the rotating part 29 is turned clockwise, the contacts are closed. At the left corner of the rotating part 29 is the Pin 24 is provided around which the fuse wire 25 is guided. One end of the fuse wire 25 is attached directly to the power connector L ₂ , the other end is clamped to the small connecting piece 20. The rotating part 29, the leaf springs 17 and 19 and the fuse wire 25 are dimensioned such that impacts or impacts on the plug housing 13 are unable to trigger the protective switching device. The rotating part 29 extends over approximately 2/3 of the housing length, so that the strength of the fuse wire 25, ie the cross section, is as small as possible. A cable bracket 32 screwed on on both sides serves as strain relief for the cable 3. The operation of this variant is the same as before. 6a shows further details. In particular, it can be seen from this that the leaf springs 17 and 19 are tapered to the right, so that a high contact force is obtained with a small contact area.

7 shows a fourth embodiment of the protective switching device. The parts which are covered by the supply lines L, ', L ₂ ' and S have been drawn with dashed lines. The mains plugs L, and L ₂ are mounted transversely to the longitudinal direction of the plug housing 13, as in FIG. 6. The ends of the flat power plugs L- and L ₂ have been slightly twisted in the housing and thus fastened on a feed-through shaft 33. The leaf springs 17 and 19 are welded here again with their right ends to the connecting piece 16 or 18. The connecting piece 16 is a U-shaped sheet metal part, the middle part of which is fastened to the housing base. The trigger 9 of FIG. 1 is a rod 34 made of conductive plastic with a double-conical weak point 35. The ends of the rod 34 are widened in a plate shape, which rest on the edges of slot-shaped recesses. 1, a torsion bar 36 is mounted on a pin 37 located centrally between the leaf springs 17 and 19. The torsion bar 36 has a wide shape Rohres, and is provided in the area of the Balttfedern 17 and 19 with a cross bar. At the end of this longitudinal member 38, a slot-shaped, upwardly open recess for the rod 34 is provided. One leg of the connecting piece 16 is also provided with such a recess. The longitudinal beam 38 is provided with a bent connecting piece 20 for the third feed line S. As can be seen from FIG. 7 a, the torsion bar 36 rotates above and independently of the leaf spring 17. In the state shown, the cross bar of the torsion bar 36 brings about the required contact pressure on the leaf springs 17 and 19. When the rod 34 melts in the region of the double-conical weak point 35, the torsion bar 36 is rotated to the left by the leaf springs 17 and 19, and the protective switching device is switched off. The rod 34 - and above all the double-conical weak point 35 - is dimensioned in such a way that rapid triggering is ensured and normal impacts and impacts on the plug housing 13 (for example dropping) cannot cause the rod 34 to break.

FIG. 8 shows a fifth variant of the protective switching device with a wire made of a shape memory alloy 39, which has the property of being shortened when heated. In this form, the leads L, 'and L ₂ ' are slightly slanted at the top in the connector housing 13 and parallel to each other on the flat connector 15. The leaf springs 17 and 19 are fastened in parallel via the connecting pieces 16 and 18, and are pressed by an elongated, T-shaped contact lever 40 with cams 41 against the power plugs L, and L ₂ . The actual switch is again self-opening. The contact lever 40 has a fulcrum 42 approximately in the middle on the left side of the plug housing 13 and is bent downwards on the right side. On this bent part of the contact lever 40 there is a latching lug 43 which projects into the paper intended. The wire 39 is fastened to an elongated, short angled flat plug pin 15 on the left side of the housing and extends longitudinally over almost the entire plug housing 13. The other end of the wire 39 is fastened to a tie rod 44 which has its end in the Connector 18 is rotatably supported limited. The tensioning rod 44 has an angular end piece 45, which is locked with the latching nose 43. The latch is designed in such a way that it can be released both by rotating the tensioning rod 44 clockwise and in the counterclockwise direction. A compression spring 46 is inserted in a U-shaped housing rib 47 and presses against the tension rod 44. In order to correctly cut the wire 39 to length during assembly, a stop 48 for the tension rod 44 is attached in the connector housing 13. As can be seen from FIG. 8a, the contact lever 40 is not disturbed by this stop 48. A reset button 49 is arranged lengthwise in the plug housing 13 at the top left. This button 49 is essentially a round rod with a notch with V-shaped sections that encompass the foot of the T-shaped contact lever 40. If the protective switching device is now triggered, ie if a sufficiently strong current flows through the wire 39, the wire is shortened

39 and moves the tension lever 44 clockwise, thereby locking between the angular end piece 45 of the tension rod 44 and the latching lug 43 of the contact lever

40 is solved. The contact lever 40 is then rotated to the left (counterclockwise) due to the spring force of the Balttfedern 17 and 19, the leaf springs 17 and 19 from the power plugs L, and L _? take off. The reset button 49 is pushed to the left and in this way indicates that the protective switching device has responded. When the wire 39 has cooled, it returns to its old length under the pressure of the spring 46, so that the latching nose 43 can be locked again by the angular end piece 45. At the bottom left is a in the longitudinal direction of the connector housing 13 Test button 50 is arranged, which consists of a short cylinder with a flanged plate. The test button 50 bears against a short leaf spring 51 which is welded to the angled end piece of the clamping bush 14 for the third feed line S. A contact angle 52 is enclosed in the housing at a short distance from it. The series resistor R (cf. also FIG. 3) connects the contact angle 52 to the connecting piece 16. If the test button 50 is now pressed, a current flows through the series resistor R to the supply line L ''. At the same time, a current then flows via the wire 39 to the feed line ₂ '(cf. also FIG. 3), as a result of which the protective switching device will trip.

The same arrangement of the fifth variant can be used for a metal wire made of a thermally expanding metal. The tie rod 44 with the angled end piece 45 then lies against the U-shaped housing rib 47, and the stop 48 is omitted. The latching lug 43 is designed so that in the event of a fault - i.e. in the expanded state of the metal wire - to the left of the angled end piece 45 is released.

A sixth embodiment is shown in FIG. 9. This embodiment largely corresponds to that shown in FIGS. 8 and 8a, but with the difference that a magnet system is provided as the trigger element instead of the memory alloy wire 39. This has a coil 53 with a yoke and a core 54 and an armature 55 which is under the action of a spring 56. The armature 55 is articulated on the yoke 54 and, in the same way as the tensioning rod 44 from FIG. 8, is provided with an angular end piece 57 which can be locked with the latching lug 43 of the contact lever 40. The contact lever 40 is not shown completely here for better visualization of the magnet system. The coil 53 is on the one hand with the supply line S and on the other hand connected to the supply line L ₂ '. in the

In the event of a fault, a current flows through the coil 53. The yoke 54 is magnetized by the fault current through the coil 53 and the armature 55 is drawn against the spring 56 against the coil 53, whereby the locking of the contact lever 40 is released. The magnet system shown is based on the "attract when excited" principle.

A magnet system based on the reverse principle of "falling off on excitation" as a trigger element is provided in the seventh embodiment according to FIG. 10. In this case, with the same configuration as in FIG. 9, a permanent magnet 58 is additionally arranged on the yoke 54 of the coil 53, by means of which the magnet system is premagnetized and the armature 55 is held against the action of the spring 56 against the coil 53. When the coil 53 is excited in the event of a fault, the magnetization is compensated for in every second half-wave of the fault current flowing through the coil, as a result of which the armature 55 falls off the coil 53 under the action of the spring 56 and releases the contact lever 40. Here, too, the contact lever 40 is not shown completely in order to make the magnet system more visible.

For the sake of simplicity, all of these variants are shown without a free triggering. It goes without saying that free tripping is also possible within the scope of the disclosed protective circuit.

Claims

1. Protective switching device for electrical devices, in particular household appliances, with

- At least two live feed lines (L, ', L ₂ ').

- A spring-loaded switch (6) which can be switched off by a trigger element (9) actuated, characterized in that

- Essentially, a single electrode (7) is provided in the housing (2) of the electrical device, which is normally electrically separated from the current-carrying parts within the device (1) and which is current-carrying in the event of a fault, and

- An electrical lead (S) connects the electrode (7) via the trigger element (9) essentially directly to one of the current-carrying leads (L, ', ^ ₂ ').

2. Protective switching device according to claim 1, characterized gekenn¬ characterized in that the electrical lead (S) of the electrode (7) via a diode (D,, D ₂ ) is connected to the current-carrying leads (L-, ', ₂ ') .

3. Protective switching device according to claim 1 or 2, characterized in that the trigger element (9) is ready for multiple use, and a reset button (49) is arranged for restarting after a fault.

4. Protective switching device according to claim 3, characterized gekenn¬ characterized in that a test button (50) is provided with a single-pole switch, the series resistor (R) switches between one of the current-carrying leads (L, ', L ₂ ') and the lead (S) of the electrode (7) such that a tripping current flows through the tripping element (9).

5. Protective switching device according to one of claims 1 or 2, characterized in that the trigger element (9) is a fuse wire or a rod (34) made of a conductive plastic.

6. Protective switching device according to one of claims 1 to 5, characterized in that the trigger element (9) is a metal wire made of a shape memory alloy or of a thermally expanding metal.

7. Protection switching device according to one of the preceding claims, characterized in that the switch (6; L,, L ₂ , 17, 19) is self-closing and a spring-loaded, electrically insulated slide (21) is provided which, in the event of a fault, the contacts of the switch (6; L,, L ₂ , 17, 19) pushes from each other.

8. Protective switching device according to one of claims 1 to 6, characterized in that the switch (6; L., L ₂ , 17, 19) is self-opening and a sliding clamp (26) is provided which contacts the contacts of the switch (6; L - ,, L ₂ , 17, 19) normally closes and releases in the event of a fault.

9. Protective switching device according to one of claims 1 to 6, characterized in that the switch is self-opening, is under spring force in the switched-on state and can be clipped in this state, that the release element acts on the latch and by releasing the latch the switch turns off.

10. Protective switching device according to one of claims 1 to 4 or 9, characterized in that the trigger element (9) is a magnet system.

11. Protective switching device according to claim 10, characterized gekenn¬ characterized in that the magnet system has a coil (53) and a spring-loaded armature (55), which in the event of a fault when the coil is energized against the action of the spring force by this and thereby switches off under spring force.

12. Protective switching device according to claim 10, characterized in that the magnet system is permanently magnetized by a permanent magnet (58) and has a coil (53) and a spring-loaded armature (55), which under the action the permanent pre-magnetization against the spring force is held against a stop of the magnet system and which, in the event of a fault, excites the coil due to the action of the spring force and thereby switches off the switch under spring force.

13. Protective switching device according to claim 11 or 12, characterized in that the armature (55) can be latched with a contact lever (40) of the switch (6) under spring force in its switched-on state.

14. Protective switching device according to one of the preceding claims, characterized in that its individual parts are housed in a connector housing (13) with the power plugs (L ,, L ₂ ) and are aligned more or less in the longitudinal direction of the housing.