GB2442555A

GB2442555A - A safe electric switch

Info

Publication number: GB2442555A
Application number: GB0718125A
Authority: GB
Inventors: Jacques Fauriot; Etienne Rejou
Original assignee: Legrand SNC; Legrand France SA
Current assignee: Legrand SNC; Legrand France SA
Priority date: 2006-10-05
Filing date: 2007-09-18
Publication date: 2008-04-09
Anticipated expiration: 2027-09-18
Also published as: GB2442555B; CN101159194B; FR2906928B1; CN101159194A; GB0718125D0; FR2906928A1

Abstract

An electric switch comprising an actuator mounted to rock between an ON position and an OFF position, the positions being situated on either side of an equilibrium axis, and a moving contact element along which one end of the actuator travels to cause it to rock between a closed position and an open position that correspond to the ON and OFF positions of the actuator, the switch being characterised in that the actuator and the moving contact element include complementary abutment means comprising two rounded projections, one of the projections being on the moving contact element and the other projection being on the actuator, the curved abutment surfaces of the projections presenting parallel tangents spaced apart by a distance lying in the range 0.5 mm to 1 mm when the actuator is placed in the ON position, and in that in the ON position, the contact zone of the end of the actuator on the moving contact element is situated at a distance from the equilibrium axis that is determined in such a manner than when the moving contact element is held in the closed position and the actuator is rocked from its ON position towards its OFF position, the end of the actuator travels on the moving contact element until the abutment means come into abutment against each other before the contact zone reaches the equilibrium axis.

Description

A SAFE ELECTRIC SWITCH

TECHNICAL FIELD TO WHICH THE INVENTION RELATES

The present invention relates to an electric switch that comprises an actuator mounted to rock between an ON position and an OFF position, which positions are situated on either side of an equilibrium axis, and a moving contact element on which one end of the actuator travels in order to cause the contact element to rock between a closed position and an open position corresponding to the ON and OFF positions of said actuator.

The invention finds a particularly advantageous application in making ON/OFF switches or changeover switches. A most advantageous application lies in particular in making two-pole electric switches in which the switch case has two switch chambers, containing respective independent moving contact elements actuated to rock by a single actuator having two control shanks.

TECHNOLOGICAL BACKGROUND

ASTA certification requires that electric switches comply with sequence 9 of British Standard BS1363 part 2 and part 4.

That sequence defines safety conditions that must be satisfied in the event of the actuator of an electric switch being operated when the moving contact element is held abnormally in its closed position, in particular because it has become stuck to the fixed contact element of the switch due to melting.

More particularly, in order to comply with those safety conditions, when the moving contact element is held abnormally in the closed position in contact with the fixed contact element, the rocking mount of the actuator must prevent a user from rocking the actuator into the OFF position.

Presently-known electric switches do not comply with that standard.

They are designed in such a manner that when the moving contact element remains stuck to the fixed contact element, and while the actuator is in the ON position, a user pressing on the control key of the actuator is capable of causing the actuator to rock until its end that travels on the moving contact element goes past the equilibrium axis situated halfway between the ON and OFF positions.

Once the end of the actuator has gone past this equilibrium axis, the pressure exerted by the actuator on the moving contact element increases until the actuator reaches an intermediate position situated between its ON and OFF extreme positions, but quite close to the OFF position, and in which it becomes blocked against the moving contact element. The pressure exerted by the actuator and the friction are so great that the actuator remains blocked in this intermediate position close to the OFF position.

OBJECT OF THE INVENTION

Compared with the above-mentioned state of the art, the present invention seeks to provide a novel electric switch complying with the requirements of British Standard BS1363.

More particularly, the invention provides an electric switch as defined in the introduction, in which the actuator and the moving contact element include complementary abutment means comprising two rounded projections, one on the moving contact element, the other on the actuator, the projections having curved abutment surfaces presenting parallel tangents that are spaced apart by a distance lying in the range 0.5 mm to 1 mm when said actuator is placed in the ON position and in which, in the ON position, the contact zone of said end of the actuator on said moving contact element is situated at a distance from the equilibrium axis that is determined in such a manner that when said moving contact element is held in the closed position and said actuator is rocked from its ON position towards its OFF position, said abutment means come into abutment against each other before said contact zone reaches said equilibrium axis.

Advantageously, in the electric switch in accordance with the invention, the actuator includes a shank that, in the ON position or in the OFF position, does not bear against any portion of the switch, and when the moving contact element is held abnormally in the closed position in contact with the fixed contact element, the actuator retains the possibility of being rocked so as to travel or slide on the moving contact element. Thus, when the moving contact element is held abnormally in the closed position in contact with the fixed contact element and the user attempts to cause the actuator to rock towards said OFF position, the rocking mount of the actuator prevents said actuator from moving to the OFF position and causes it to return automatically to the ON position.

In a first advantageous embodiment of the switch in accordance with the invention, the equilibrium axis is offset relative to the axis of symmetry of the tilt angle of the actuator in such a manner that the stroke followed by the actuator to go from the ON position to the OFF position is longer than the stroke followed by the actuator to go from the OFF position to the ON position.

In this embodiment, and preferably, the offset between the equilibrium axis and said axis of symmetry is of the order of 2 .

In a second advantageous embodiment of the switch in accordance with the invention, said end of the actuator presents a shape that is asymmetrical.

In this embodiment, and preferably, said end presents a cam profile with two sloping flats of different lengths and inclinations, converging towards a rounded tip.

Said contact zone of said end is then situated at the junction between the longer sloping flat and said rounded tip.

In a third advantageous embodiment of the switch in accordance with the invention, the actuator comprises a control key made available to the user and a shank with a free end that travels on said moving contact element, the shank presenting an axis of symmetry that is inclined relative to the axis of symmetry of said control key.

In this embodiment, and preferably, the angle of inclination of said axis.of symmetry of the shank is of the order of 2 .

Other advantageous and non-limiting characteristics of the electric switch of the invention are as follows: the curved abutment surfaces present parallel tangents that are spaced apart by a distance lying in the range 0.7 mm to 0.8 mm when said actuator is placed in the ON position; the actuator comprises a control key secured to a shank that includes a cylindrical cavity housing a helical spring bearing against a piston having a nose constituting said end of the actuator; said moving contact element comprises a metal blade carrying a silver contact pellet at one end, said metal blade being mounted to rock on a metal strip; and the electric switch is a two-pole switch for interrupting both the live and the neutral wires, having two independent moving contact elements actuated by a single actuator having two bearing ends and only one control key.

DETAILED DESCRIPTION OF N EMBODINT

The following description with reference to the

accompanying drawings, given as non-limiting examples, shows clearly what the invention consists in and how it can be performed.

In the accompanying drawings: Figures 1A, 1B, and 10 are diagrammatic perspective views of an inside portion of the case of an electric switch of the invention; * Figure 2 is a fragmentary diagrammatic side view of a first embodiment of an electric switch of the invention with its actuator in the ON position; * Figure 3 is an enlargement of detail III of Figure 2; * Figure 4 is an enlargement of detail IV of Figure 2; * Figure 5 is a fragmentary diagrammatic side view of the Figure 2 electric switch with its actuator placed in an unstable position intermediate between its ON and OFF extreme positions; * Figure 6 is a diagrammatic detail view of the piston of the actuator of the Figure 7 electric switch; * Figure 7 is a fragmentary diagrammatic side view of a second embodiment of the electric switch of the invention with its actuator placed in the ON position; * Figure 8 is a fragmentary diagrammatic side view of the Figure 7 electric switch with its actuator placed in an unstable position intermediate between its ON and OFF extreme positions; Figure 9 is a diagrammatic detail view of the actuator of the Figure 10 electric switch; Figure 10 is a fragmentary diagrammatic side view of a third embodiment of the electric switch of the invention with its actuator placed in the ON position; and Figure 11 is a fragmentary diagrammatic side view of the Figure 10 electric switch with its actuator placed in an unstable position intermediate between its extreme ON and OFF positions.

As a preliminary, it should be observed that from one figure to another, elements that are identical or similar in the various embodiments shown are, whenever possible, given the same reference signs and are not described again on each occasion.

Figures 1A, 1B, 1C, 2, 7, and 10 show three embodiments of an electric switch 1, e.g. an ON/OFF switch or a changeover switch, and it comprises a case 100 of insulating material housing electrical contact elements 20, of metal together with an actuator 10 for making and breaking electric contact between the electrical contact elements 20, 30.

More particularly, as shown in Figures 2, 7, and 10, the electric switch 1 houses in its case 100 at least one fixed contact element 30 and at least one moving contact element 20 adapted to take up two extreme positions, namely a closed position in contact with the fixed contact 30, and an open position out of contact with the fixed contact 30.

Each contact element 20, 30 shown is in the form of a metal blade carrying a silver contact pellet 21, 31 at one end.

The metal blade of the moving contact element 20 is mounted to rock on a pressed metal strip 40 placed on the bottom of a housing 110 in the case 100 (see Figures 1A, 1B, 1C) The metal strip 40 is connected to a terminal (not shown) for connection to an electrical feed wire coming from mains for feeding the electric switch 1 with electricity.

The metal strip 40 is in the form of a blade, having a curved end 41 that presents a straight edge 42 against which the central portion 23 of the metal blade of the moving contact element 20 comes to bear. The straight edge 42 forms the pivot axis about which the moving contact element 20 pivots to go from one extreme position to the other.

On either side of this central portion 23, the moving contact element 20 presents, on both longitudinal sides, respective tabs 22 that bear against internal ribs 120 of the case 100 (see Figures 1A, 1B, 1C) . These tabs 22 bearing against the internal ribs 120 serve to stabilize the moving contact element 20 in the housing 110 of the case 100, while bearing against the straight edge 42 of the metal strip 40, so that the contact area between the metal strip 40 and the moving contact element 20 is sufficient to pass electric current properly between these two metal blades without leading to heating.

As shown in Figures 2, 7, and 10, the electric switch 1 includes an actuator 10 mounted to rock between an ON position and an OFF position situated on either side of an equilibrium axis Xl.

The actuator 10 presents an end 17A; 17'A that travels or that slides on said moving contact element 20 to cause it to rock between its closed position and its open position which correspond to the ON position and the OFF position of said actuator 10.

The actuator 10 is an insulating material part having an control key 11 made available to the user, and a shank 13; 13' that includes a cylindrical cavity 15 housing a helical spring 16 with one end bearing against the end wall of the cylindrical cavity 15 and its other end bearing against a piston 17; 17' whose nose 17A; 17'A bears against the moving contact element 20. The nose 17A; 17'A of the piston 17 constituting said end of the actuator 10 presents a cam profile with two sloping flats that converge towards a rounded tip.

The control key 11 may be fitted onto the shank 13; 13' of the actuator, or it may be formed integrally therewith to constitute a one-piece part (by molding a plastics material) The control key 11 is surrounded by a margin 12 that forms an abutment suitable for cooperating with a complementary abutment (not shown) of the case 10 so as to hold the actuator 10 in each of its two extreme ON and OFF positions.

In contrast, in both of the extreme ON and OFF positions, the shank 13; 13' of the actuator 10 does not bear against any portion of the electric switch. Thus, when the moving contact element 20 is held abnormally in the closed position in contact with the fixed contact element 3D, the actuator 10 retains the possibility of being rocked to travel or slide on the moving contact element 20.

On either side of the control key 11, the actuator 10 has two stub axles hA that embody the pivot axis of the actuator. These stub axles hA are designed to snap into bearings (not shown) of the case 100 of the electric switch 1 so as to mount the actuator 10 pivotally in the case 100.

The pivot axes of the actuator 10 and of the moving contact element 20 are parallel to each other.

The equilibrium axis Xl on either side of which there are situated firstly the ON and OFF positions of the actuator, and secondly the closed and open positions of the moving contact element 20, itself extends perpendicularly to said pivot axes of the actuator 10 and of the moving contact element 20.

This equilibrium axis Xl intersects the pivot axis of the moving contact element 20 embodied by the straight edge 42 at the curved end 41 of the metal strip 40, at a point of intersection referred to as the equilibrium point I (see Figure 4).

As shown more particularly in Figures 3, 5, 8, and 11, according to essential characteristics of the electric switch 1, the actuator 10 and the moving contact 20 have complementary abutment means 14, 24, and in the ON position, the contact zone 17B; 17'B of said end l7A; 17'A of the actuator 10 on said moving contact element 20 is situated at a distance from the equilibrium axis Xl that is determined in such a manner that when said moving contact element 20 is held in the closed position (e.g. because its contact pellet 21 is stuck to the contact pellet 31 of the fixed contact element 30 due to melting) and said actuator is rocked from its ON position towards its OFF position, said abutment means 14, 24 come into abutment each other before said contact zone 17B; 17'B reaches said equilibrium axis Xl (and more particularly reaches said equilibrium point I).

In the first embodiment of the electric switch 1 shown in Figures 2 to 5, the equilibrium axis Xl is offset from the axis of symmetry X2 by the angle of tilt of the actuator 10 such that the stroke followed by the actuator 10 to pass from the ON position to the OFF position is longer than the stroke followed by the actuator 10 to pass from the OFF position to the ON position.

Preferably, the offset between the equilibrium axis Xl and said axis of symmetry X2 is of the order of 2 .

Said determined distance between the equilibrium axis Xl (or the equilibrium point I) and said contact zone 17B of the end 17A of the actuator 10 placed in the ON position, corresponds to an angle Al of the order of 11.2 formed between the equilibrium axis Xl and the axis of symmetry X3 of the actuator 10 and passing through the rounded tip of the nose 17A of the piston 17.

In this ON position, the angle Al formed between the axis of symmetry X3 of the actuator 10 and the axis of symmetry X2 of the angle of tilt of the actuator 10 is of the order of 9.1 .

In the second embodiment of the electric switch 1 shown in Figures 6 to 8, said end 17'A of the actuator 10 presents a shape that is asymmetrical.

More particularly, the piston 17' here presents a cylindrical body of axis of symmetry X3 and a nose 17'A having its rounded tip shifted a little way from said axis of symmetry X3. The nose 17'A presents a cam profile with two sloping flats having different lengths and inclinations that converge towards the rounded tip.

As shown more particularly in Figure 8, in this second embodiment, the equilibrium axis Xl coincides with the axis of symmetry X2 of the tilt angle of the actuator 10. Said contact zone 17'B of the nose 17'A of the piston 17 of the actuator 10 on the moving contact element 20 is situated at the junction between the longer sloping flat of the nose 17'A and said rounded tip. It is shifted a little relative to the axis of symmetry X3 of the cylindrical body of the piston 17' and of the control key 11 of the actuator 10.

In the third embodiment of the electric switch 1, shown in Figures 9 to 11, the equilibrium axis Xl coincides with the axis of symmetry X2 of the tilt angle of the actuator 10, and the shank 13' of the actuator 10 presents an axis of symmetry X4 that is inclined relative to the axis of symmetry X3 of said control key 11. The angle of inclination A3 of said axis of symmetry X4 of the shank 13' is preferably of the order of 2 .

Furthermore, as can be seen more particularly in Figures 2 and 3, said complementary abutment means of the moving contact element 20 and of the actuator 10 include rounded projections 24, 14, one of the projections 24 being on the moving contact element 20 and the projection 14 on the actuator 10, having convex curved abutment surfaces 24A, 14A that present parallel tangents T, T' spaced apart by a distance d lying in the range 0.5 millimeters (mm) to 1 mm when said actuator 10 is placed in the ON position.

Said curved abutment surfaces 24A, 14A preferably present parallel tangents T, T' that are spaced apart by a distance d lying in the range 0.7 mm to 0.8 mm when said actuator 10 is placed in the ON position.

The operation of each of the above-described embodiments is as follows.

To open the electrical contact between the fixed contact element 30 and the moving contact element 20, the user exerts pressure on the control key 11 of the actuator to cause it to rock from its ON position to its OFF position.

In normal operation, when the moving contact element is not stuck to the fixed contact element 30, then starting from the ON position, the contact zone 17B; 17'B of the nose 17A; 17'A of the piston 17; 17' of the actuator 10 bearing, under thrust from the helical spring, against the metal blade of the moving contact element 20, then travels along said blade until it reaches the equilibrium point I (or the equilibrium axis Xl).

When said contact zone 17B; 17'B reaches the equilibrium point I, the actuator 10 rocks to the other side of the equilibrium axis Xl towards its OFF position, taking with it said moving contact element 20 which rocks towards its open position.

In abnormal operation, when the contact pellet 2]. of the moving contact element 20 is stuck to the contact pellet 21 of the fixed contact element 30 by melting (e.g. due to an electric arc), then starting from the ON position, the contact zone 17B; 17B' of the nose 17A; l7'A of the piston 17; 17' of the actuator 10 bearing under thrust from the helical spring, against the metal blade of the moving contact element 20, then travels along said blade until the curved abutment surfaces 14A, 24A of the rounded projections 14, 24 of the actuator 10 and of the moving contact element 20 come into abutment against each other, thereby preventing the actuator 10 from going any further along its stroke.

Advantageously, in this abutment position, said contact zone 17B; 17'B of the nose 17A; 17'A of the piston 1); 17' of the actuator 10 against the metal blade of the moving contact element 20 has not yet reached the equilibrium point I, and since the actuator 10 has not reached the equilibrium axis Xl, when the user releases the pressure exerted on the control key 11, the actuator returns automatically to its original ON position.

Thus, in safe manner, the control key 11 of the actuator 10 informs users that the electric switch 1 cannot be switched to its OFF position because of a malfunction.

The present invention is not limited in any way to the embodiments described and shown, and the person skilled in the art will know how to apply any variant thereto in accordance with its spirit.

In particular, in a variant, provision can be made for the electric switch to be a two-pole switch acting both on the live (phase) wire and on the neutral wire. Such a switch has a case with two switch chambers (similar to the housing 110 of Figure 1A), each housing a respective fixed contact element 30 and moving contact element 20 pivotally mounted on a strip 40.

The actuator of such a switch has a single control key and two ends positioned at the same level that bear against the two moving contact elements that are parallel and independent so as to cause them to rock from one extreme position to the other.

Specifically, the actuator has a control key 11 secured to two parallel shanks 13, each shank having a cylindrical cavity 15 housing a helical spring 16 that bears against a piston 17; 17' with a nose 17A; 17'A that constitutes said end of the actuator.

The actuator is mounted to rock in the housing of the switch between an ON position and an OFF position situated on either side of a single equilibrium axis. Its rocking movement actuates both moving contact elements simultaneously to pivot between their open and closed extreme positions.

The advantageous arrangement of the present invention then applies to each pair comprising a moving contact element and an actuator.

By means of this advantageous arrangement, in such a two-pole switch, when one of the two moving contact elements remains stuck to the corresponding fixed contact element, while the other moving contact element remains free to pivot, the pivoting movement of the free moving contact element does not run any risk of entrairiing the actuator into the OFF position, since the actuator is automatically returned to the ON position because said complementary abutment means of the stuck moving contact element and of the actuator come into abutment against each other before said ends of the actuator reach said equilibrium axis (or said equilibrium points I).

Claims

CLA I MS

1. An electric switch (1) comprising an actuator (10) mounted to rock between an ON position and an OFF position, said positions being situated on either side of an equilibrium axis (Xl), and a moving contact element (20) along which one end (17A; 17'A) of the actuator (10) travels to cause it to rock between a closed position and an open position that correspond to the ON and OFF positions of said actuator (10), the switch being characterized in that the actuator (10) and the moving contact element (20) include complementary abutment means (14, 24) comprising two rounded projections (24, 14), one of the projections (24) being on the moving contact element (20) and the other projection (14) being on the actuator (10), the curved abutment surfaces (24A, 14A) of the projections presenting parallel tangents (T, T') spaced apart by a distance (d) lying in the range 0.5 mm to 1 mm when said actuator is placed in the ON position, and in that in the ON position, the contact zone (17B; 17'B) of said end (l7A; 17'A) of the actuator (10) on said moving contact element (20) is situated at a distance from the equilibrium axis (Xl) that is determined in such a manner that when said moving contact element (20) is held in the closed position and said actuator (10) is rocked from its ON position towards its OFF position, said end (17A; 17'A) of the actuator (10) travels on said moving contact element (20) until said abutment means (14, 24) come into abutment against each other before said contact zone (17B; 17'B) reaches said equilibrium axis (Xl)

2. An electric switch according to claim 1, characterized in that the equilibrium axis (Xl) is offset relative to the axis of symmetry (X2) of the tilt angle of the actuator (10) in such a manner that the stroke followed by the actuator (10) to go from the ON position to the OFF position is longer than the stroke followed by the actuator (10) to go from the OFF position to the ON position.

3. An electric switch according to claim 2, characterized in that the offset between the equilibrium axis (Xl) and said axis of symmetry (X2) is of the order of 2 .

4. An electric switch according to claim 1, characterized in that said end (17'A) of the actuator presents a shape that is asymmetrical.

5. An electric switch according to the preceding claim, characterized in that said end (17'A) presents a cam profile with two sloping flats of different lengths and inclinations, converging towards a rounded tip.

6. An electric switch according to the preceding claim, characterized in that said contact zone (17'B) of said end (17'A) is situated at the junction between the longer sloping flat and said rounded tip.

7. An electric switch according to claim 1, characterized in that the actuator (10) comprises a control key (11) made available to the user and a shank (13') with a free end that travels on said moving contact element, the shank (13') presenting an axis of symmetry (X4) that is inclined relative to the axis of symmetry (X3) of said control key (11)

8. An electric switch according to claim 5, characterized in that the angle of inclination of said axis of symmetry (X4) of the shank (13') is of the order of 2 .

9. An electric switch according to any preceding claim, characterized in that the curved abutment surfaces (24A, 14A) present parallel tangents (T, T') that are spaced apart by a distance (d) lying in the range 0.7 mm to 0.8 mm when said actuator is placed in the ON position.

10. An electric switch according to any preceding claim, characterized in that the actuator (10) comprises a control key (11) secured to a shank (13; 13') that includes a cylindrical cavity (15) housing a helical spring (16) bearing against a piston (17; 17') having a nose (17A; 17'A) constituting said end of the actuator.

11. An electric switch according to any preceding claim, characterized in that said moving contact element (20) comprises a metal blade carrying a silver contact pellet (21) at one end, said metal blade being mounted to rock on a metal strip (40)

12. An electric switch according to any preceding claim, characterized in that it is a two-pole switch for interrupting both the live and the neutral wires, having two independent moving contact elements (20) actuated by a single actuator having two bearing ends and only one control key.