Apparatus for supplying high voltage pulses

Description

[0001] Apparatus which can supply high voltage pulses to create sparks may be used for ignition purposes, such as in the ignition system of an internal combustion engine, although other uses are contemplated.

[0002] A conventional internal combustion engine has an ignition system incorporating a transformer whose high tension secondary coil will cause a spark to be formed across the spark gap of a spark plug when the power supply to the primary coil is interrupted, so that the magnetic field created by the primary coil collapses. Thus there is a contact breaker which alternately makes and breaks the circuit to the primary coil once during a complete revolution of a cam for each spark plug in the system. Unless the engine is properly tuned sparking may occur at the wrong moment to ensure correct burning of the fuel in the cylinder of the engine and even with a properly tuned system an appreciable proportion of the fuel is not burned and is passed to the exhaust, thus wasting fuel and causing pollution. Improved firing characteristics can be achieved by providing more than one spark plug for each cylinder but this adds to the cost and makes tuning more difficult. Apparatus for creating a sequence of high voltage pulses has also been proposed in FR-A-2036291 and US-A-3543740. However these require complicated modifications to the existing ignition system circuitry and incorporate substantial numbers of circuit components which add appreciably to the cost and likelihood of breakdown of the ignition system.

[0003] It is an object of this invention to provide apparatus for an ignition system, such as for an internal combustion engine, which can produce high voltage pulses which will create improved ignition sparking and which may readily be incorporated in an existing ignition system.

[0004] Accordingly this invention provides apparatus for supplying a continuous stream of high voltage pulses at the secondary coil output of a transformer of an ignition system, such as for an internal combustion engine, the ignition system having a primary coil circuit including a contact breaker, means for connection to a voltage source, and a switch, a part of which is connected to or formed by a magnetically attractive body, wherein the switch part is positioned adjacent the actual transformer core of the ignition system so that the switch part will move to bring the switch to the open condition against a closing bias when a magnetic field passes through the transformer core.

[0005] With such an apparatus instead of a single spark occurring across the spark gap of the spark plug of an internal combustion engine, for example, a substantially continuous spark will be produced (in the form of a very rapid sequence of pulses) over a predetermined period of time. This will ensure that better combustion characteristics of the fuel in an internal combustion engine will be achieved. It will be appreciated, however, that this apparatus could be used for other purposes where an effectively continuous spark could be useful, for example an ignition device for a gas or oil burner.

[0006] If the contact breaker is connected in series with the switch, the contact breaker will be designed to have its contacts closed during the period when a spark is required and the length of time during which sparking will continue will of course depend upon the period of time during which the contact breaker is in the closed state. The contact breaker could be of the conventional form wherein a rotating cam opens and closes a pair of contacts such that movement of the cam follower will cause the contacts to close rather than to open as is usual. Alternatively the contact breaker may comprise a photocell operated by light passing through an opening in a rotating disc, the length of the opening determining the time during which a current will be supplied by an electronic circuit incorporating the photocell to the primary coil of the transformer, and thus determining the time during which sparking will occur under control of the apparatus of this invention. As a further example, a transistorised ignition system may be employed to replace the conventional contact breaker and allow the operating current to be supplied to the primary coil of the transformer for the required length of time for producing the continuous stream of high voltage pulses to each spark plug of the internal combustion engine.

[0007] The contact breaker may be connected in parallel with the switch. This enables the contact breaker to operate in a conventional manner with the result that whilst the contact breaker is normally closed the switch will be held open by the magnetic field induced in the transformer but when the contact breaker opens the current from the power supply will flow in series through the switch and the transformer primary coil resulting in intermittent operation of the switch to produce the desired rapid sequence of pulses. This arrangement has the advantage that the timing of the initial spark produced is determined by the opening of the contact breaker. Thus the timing may be adjusted accurately and the automatic adjustment which occurs for example with a vacuum assisted advance mechanism will operate in the correct manner. The parallel circuit incorporating the switch may incorporate an isolating switch so that, when the isolating switch is opened the ignition system will operate in the conventional manner. If desired the parallel circuit may then be utilised only during starting and it may of course be isolated should a malfunction occur. An overload fuse could also be incorporated in the parallel circuit.

[0008] The switch, which is to be operated by a magnetic field passing through the transformer core, may take many forms and could comprise a reed switch, mercury switch or trembler switch,.for example. Also the switch could be an electronic circuit incorporating a photocell, the switch part, to which the magnetically attractive body is attached, being movable between conditions wherein a light path to the photocell is respectively blocked or unimpeded. The switch would need to be sufficiently robust for the particular situation in which it is used such as in apparatus for supplying high voltage pulses to a sparking plug. Where the switch employs opening and closing contacts ideally a condenser will be connected in parallel with the switch to minimise arcing at the switch contacts.

[0009] Preferably, however, the switch will comprise a pair of contacts, one of which is carried on a movable switch arm and is biased into the closed position against the other contact, such as by a light spring and is connected to a magnetically attractive disc positioned adjacent the end of the transformer core. When current is supplied to the primary winding of the transformer a magnetic field will be induced in the transformer core which is effective to attract the body connected to the one contact of the switch, thus opening the switch and interrupting the supply of current to the primary coil. The resulting collapse of the magnetic field will cause a high voltage to be generated in the secondary winding, resulting in a spark across the spark gap of a spark plug and at the same time the body connected to the one contact of the switch will be released to allow the switch to close and complete the circuit through the primary coil. The sequence will be repeated continuously until the switch is rendered inoperative by disconnecting the voltage supply to the primary coil and to the switch for the series arrangement, or by-passing the switch in the parallel arrangement. Thus, a rapid sequence uf high voltage pulses will be supplied to the spark plug resulting in a substantially continuous spark being produced.

[0010] The invention also extends to a unit for converting an existing transformer of an ignition system, such as for an internal combustion engine, to create apparatus of this invention as hereinbefore defined, the ignition system having a primary coil circuit including a contact breaker and means for connection to a voltage source, wherein the unit comprises a switch, connecting leads from the two contacts of the switch for connecting the switch into the primary coil circuit of the transformer and a mounting device for attaching the switch to the body of the transformer so that a magnetically attractive body, forming or connected to part of the switch, will lie in the axial magnetic field of the transformer core.

[0011] The invention may be performed in various ways and preferred embodiments thereof will now be described with reference to the accompanying drawings, in which:

Figure 1 illustrates an ignition system for an internal combustion engine utilising apparatus according to this invention;

Figure 2 illustrates an alternative ignition system of the invention; and

Figure 3 is an illustration of the circuit of Figure 2 as laid out in an ignition system of a vehicle.

[0012] The device of Figure 1 incorporates a transformer having a core 1, primary winding 2 and secondary winding 3. The primary winding 2 is connected to a power supply 4 through a contact breaker device 5 and a switch 6. The secondary winding 3 is connected through a conventional distributor 7 to spark plugs 8 in the cylinders of an internal combustion engine.

[0013] When the switch of contact breaker 5 is in the closed condition a magnetic field is induced in the core 1 which attracts a plate 9 of magnetically attractive material which is attached to an arm 10 carrying one of the contacts 11 of the switch 6 and pivoted at 12. The arm 10 is normally biased by a spring (not shown) so as to close the contacts 11 and 13 of the switch 6. When the contacts open the supply of current to the primary winding 2 is interrupted and the high voltage generated in the secondary winding by collapse of the magnetic field in the core 1 is passed to one of the spark plugs 8 through the distributor 7. Collapse of the magnetic field allows the contacts 11 and 13 to close again and the sequence is repeated at a very rapid rate during the time that the contact breaker 5 is closed, so that a sequence of high voltage pulses is supplied to the one spark plug 8. A condensor 14 is connected in parallel across the switch 6 to suppress arcing across the contacts 11 and 13.

[0014] The contact breaker device 5 can comprise a conventional arrangement of a rotating cam which operates on a cam follower attached to a contact arm biased by a spring so that the contacts will normally be open. As each lobe of the cam operates on the cam follower the contacts will close so as to complete the circuit through the supply source 4 and the primary windings 2 to the switch 6 shown in Figure 1. The length of time during which the supply source is thus connected into the circuit (and therefore the time during which the rapid sequence of sparks are applied to one of the spark plugs 8) will depend upon the length of the cam follower surface of the cam follower.

[0015] As an alternative the contact breaker device 5 could be replaced by the device of a photocell and a rotating disc incorporating slots which allow light to pass through to the photocell so as to complete the circuit through the switch and the primary winding 2. The period during which the spark plug is operative can then of course be modified by varying the length of the slot.

[0016] In the alternative arrangement illustrated in Figure 2, the switch 6 is connected in parallel with the contact breaker 5 and the condensor 14 is connected directly across the contact breaker and can therefore be the existing condensor present in a conventional circuit. An isolating switch 15 enables the switch 6 to be brought into use as and when required or to be isolated if a malfunction should occur, thus enabling the system to operate in a conventional manner under control solely of the contact breaker 5. A trip fuse 1 6 will allow for any overload occurring and this could be associated with a warning light on the dashboard of the vehicle. With this circuit, when the circuit breaker switch is in the closed position the switch 6, which will be held in the open position by the magnetic field induced by the current flowing through the primary coil 2, will be by-passed. However when the circuit breaker switch opens the current through the coil 2 will be interrupted resulting in the collapse of the magnetic field, the occurrence of a spark in one of the spark plugs 8, and closure of the switch 6. The switch 6 will then open and close intermittently, thus causing a sequence of sparks in the spark plug 8 until such time as the circuit breaker switch reverts to the closed condition. It will be appreciated that the isolating switch 15 could be linked with the choke of a vehicle so that the switch 6 is only effective during starting whilst the choke is in operation.

[0017] It will be appreciated that the switch 6 could be replaced by a photocell which would be operated by means of a member moving in and out of the light path to the photocell as the plate 9 is intermittently attracted to the transformer core 1. This would remove the possibility of sparking occurring in the control circuit.

[0018] Figure 3 illustrates how the circuit of Figure 2 might appear in the actual layout of the ignition system of a vehicle. For clarity, the rotor arm of the distributor 7 has been omitted to show clearly the contact breaker device 5 operated by a cam 19. This Figure also illustrates how an auxiliary capacitor 20 might be incorporated into the circuit if the existing capacitor 14 in the conventional ignition system is of too small a value for the modified circuit.

[0019] A conventional vehicle ignition system may readily be adapted to the form illustrated in Figure 2 of the drawings in particular by incorporating the parallel circuit of the switch 6, isolating switch 15 and fuse 16 across the contact breaker 5 and attaching the switch 6 assembly adjacent the end of the transformer casing 17. Thus the switch 6 with its associated magnetically attractive plate 9 could be housed within a casing extension 18 (shown in dashed outlined) which is adapted to clip onto the existing casing 17. The fuse 16 and isolating switch 15 could be positioned where required. With the arrangement shown in Figure 1 the switch 6 and associated parts together with the condenser 14 could be housed in the casing extension 18 clipped onto the casing 17. Again a circuit could readily be incorporated into that of an existing ignition system. Where a complete ignition system is being installed then a custom-made unit comprising the transformer with the switch 6 positioned therebelow within a single casing could be supplied.

[0020] The positioning of the magnetically attractive plate 9 may be modified, as illustrated in Figure 3, so as to be within the main casing 17 and adjacent the ceramic core 21 of the core 1, a pin 22 attached to the plate 9 passing into a hole in the core 21 to act as a bearing member as the plate 9 moves. Biasing of the plate 9 away from the core 1 (to cause closure of the switch 6) is achieved by a resilient pad 23, such as of sorbo rubber. Because the plate 9 is much closer to the core 1 in this arrangement, a strong closing bias, by the pad 23, can be provided to ensure positive closure of the switch 6 and a reduction in possible arcing.

[0021] This apparatus can have many uses, some of which are mentioned above. Additionally it could be used to provide a continuous flame (the spark) for the purpose of igniting various materials or fuels or, for example, for the localised destruction of weeds.

Claims

1. Apparatus for supplying a continuous stream of high voltage pulses at the secondary coil (3) output of a transformer of an ignition system, such as for an internal combustion engine, the ignition system having a primary coil (2) circuit including a contact breaker (5), means for connection to a voltage source (4), and a switch (6) a part (9) of which is connected to or formed by a magnetically attractive body, characterised in that the switch part (9) is positioned adjacent the actual transformer core (1) of the ignition system so that the switch part (9) will move to bring the switch to the open condition against a closing bias when a magnetic field passes through the transformer core (1).

2. Apparatus according to claim 1, characterised in that the contact breaker (5) is connected in series with the switch (6), the contact breaker (5) being designed to have its contacts closed during the period when a spark is required.

3. Apparatus according to claim 2, characterised in that the contact breaker (5) is constructed so that a rotating cam opens and closes a pair of contacts such that movement of the cam follower will cause the contacts to close.

4. Apparatus according to claim 2, characterised in that the contact breaker comprises a photocell operated by light passing through an opening in a rotating disc, the length of the opening determining the time during which a current will be supplied by an electronic circuit incorporating the photocell to the primary coil (2) of the transformer, and thus determining the period during which sparking will occur.

5. Apparatus according to claim 1, characterised by the incorporation of a transistorised ignition system which will operate to allow the operating current to be supplied to the primary coil (2) of the transformer for the required length of time for producing the continuous stream of high voltage pulses to each spark plug (8) of the internal combustion engine.

6. Apparatus according to claim 1, characterised in that the contact breaker (5) is connected in parallel with the switch (6).

7. Apparatus according to claim 6, characterised in that the parallel circuit incorporating the switch (6) also incorporates an isolating switch (15) so that, when the isolating switch (15) is opened the ignition system will operate in the conventional manner.

8. Apparatus according to claim 6 or claim 7, characterised in that an overload fuse (16) is incorporated in the parallel circuit incorporating the switch.

9. Apparatus according to any one of claims 1 to 8, characterised in that the switch (6) which is to be operated by a magnetic field passing through the transformer core (1) comprises a reed switch, mercury switch or trembler switch.

10. Apparatus according to claim 9, characterised in that a condenser (14) is connected in parallel with the switch (6) to minimise arcing at the contacts of the switch (6).

11. Apparatus according to any one of claims 1 to 8, characterised in that the switch (6) is an electronic circuit incorporating a photocell, the switch part (9), to which the magnetically attractive body is attached, being movable between conditions wherein a light path to the photocell is respectively blocked or unimpeded.

12. Apparatus according to any one of claims 1 to 8, characterised in that the switch (6) comprises a pair of contacts (11, 13), one of which is carried on a movable switch arm (10) and is biased into the closed position against the other contact, such as by a light spring, and is connected to a magnetically attractive disc (9) positioned adjacent the end of the transformer core (1).

13. A unit for converting an existing transformer of an ignition system such as for an internal combustion engine to provide apparatus according to claim 1, the ignition system having a primary coil (2) circuit including a contact breaker (5), and means for connection to a voltage source (4), characterised in that the unit comprises a switch (6), connecting leads from the two contacts (11, 13) of the switch (6) for connecting the switch (6) into the primary coil (2) circuit of the transformer and a mounting device for attaching the switch (6) to the body of the transformer so that a magnetically attractive body (9), forming or connected to part of the switch (6), will lie in the axial magnetic field of the transformer core (1).

Revendications

1. Dispositif pour engendrer un train continu d'impulsions de haute tension à la sortie de l'enroulement secondaire (3) d'un transformateur d'un système d'allumage, tel que celui d'un moteur à combustion interne, le système d'allumage comprenant un circuit pour l'enroulement primaire (2) renfermant un rupteur (5), des moyens pour réaliser une connexion à une source de tension (4), et un commutateur (6) dont un composant (9) est relié à ou formé par un organe d'attraction magnétique, caractérisé en ce que le composant (9) du commutateur est positionné à proximité du noyau (1) du transformateur réel du système d'allumage de façon que le composant (9) du commutateur se déplacera pour amener le commutateur en position ouverte à l'encontre d'une force le sollicitant vers la fermeture quand un champ magnétique travers le noyau (1) du transformateur.

2. Dispositif selon la revendication 1, caractérisé en ce que le rupteur (5) est relié en série au commutateur (6), le rupteur (5) étant conçu pour avoir ses contacts fermés pendant la période au cours de laquelle une étincelle doit être engendrée.

3. Dispositif selon la revendication 2, caractérisé en ce que le rupteur (5) est construit de façon qu'une came rotative ouvre et ferme deux contacts de telle manière que le mouvement du toucheau de came provoquera la fermeture des contacts.

4. Dispositif selon la revendication 2, caractérisé en ce que le rupteur comprend une cellule photo-électrique activée par un faisceau lumineux passant à travers une ouvertures ménagée dans un disque rotatif, la longueur de l'ouverture déterminant la période de temps au cours de laquelle un courant sera fourni par un circuit électronique incluant la cellule photo-électrique, à l'enroulement primaire (2) du transformateur et déterminant ainsi la période de temps durant laquelle la génération des étincelles a lieu.

5. Dispositif selon la revendication 1, caractérisé par l'incorporation d'un système d'allumage transistorisé que agit pour permettre au courant d'activation d'être fourni à l'enroulement primaire (2) du transformateur pendant le laps de temps requis pour engendrer le train continu d'impulsions de haute tension appliqué à chaque bougie (8) du moteur à combustion interne.

6. Dispositif selon la revendication 1, caractérisé en ce que le rupteur (5) est monté en parallèle sur le commutateur (6).

7. Dispositif selon la revendication 6, caractérisé en ce que le circuit parallèle incluant le commutateur (6) comprend aussi un commutateur isolateur (15) de sorte que, lorsque le commutateur isolateur (15) est ouvert, le système d'allumage fonctionne de la manière classique.

8. Dispositif selon la revendication 6 ou 7, caractérisé en ce qu'un fusible de protection contre les surintensités (16) est incorporé dans le circuit parallèle incluant le commutateur.

9. Dispositif selon l'une quelconque des revendications 1 à 8, caractérisé en ce que le commutateur (6) qui est destiné à être actionné par un champ magnétique traversant le noyau (1) du transformateur est constitué par un commutateur à lame vibrante, un commutateur à mercure ou un commutateur à trembleur.

10. Dispositif selon la revendication 9, caractérisé en ce qu'un condensateur (14) est monté en parallèle sur le commutateur (6) pour réduire à un minimum la formation d'arcs au niveau des contacts du commutateur (6).

11. Dispositif selon l'une quelconque des revendications 1 à 8, caractérisé en ce que le commutateur (6) est un circuit électronique comprenant une cellule photo-électrique, le composant (9) du commutateur, auquel l'organe d'attraction magnétique est rattaché, étant déplaçable entre des positions dans lesquelles un trajet pour le faisceau lumineux dirigé vers la cellule photo-électrique est respectivement obstrué ou désobstrué.

12. Dispositif selon l'une quelconque des revendications 1 à 8, caractérisé en ce que le commutateur (6) comprend deux contacts (11, 13) dont l'un est porté par une branche de commutation mobile (10) et est sollicité dans la position de fermeture contre l'autre contact, par exemple sous l'action d'un ressort de faible raideur, et est relié à un disque d'attraction magnétique (9) positionné à proximité de l'extrémité du noyau (1) du transformateur.

13. Appareillage pour convertir un transformateur existant d'un système d'allumage, tel que celui d'un moteur à combustion interne, en un dispositif selon la revendication 1, le système d'allumage comportant un circuit pour l'enroulement primaire (2) renfermant un rupteur (5), et des moyens pour réaliser une connexion à une source de tension (4), caractérisé en ce que l'appareillage comprend un commutateur (6), des fils conducteurs de connexion partant des deux contacts (11, 13) du commutateur (6) pour connecter le commutateur (6) à l'intérieur du circuit de l'enroulement primaire (2) du transformateur et un organe de montage pour fixer le commutateur (6) sur le corps du transformateur de telle manière qu'un organe d'attraction magnétique (9) qui forme le composant du commutateur (6) ou qui est relié à celui-ci, se trouve dans le champ magnétique axial du noyau (1) du transformateur.

Ansprüche

1. Vorrichtung zum Liefern eines kontinuierlichen Stromes von Hochspannungsimpulsen am Ausgang der Sekundärwicklung (3) eines Transformators eines Zündsystems, beispielsweise für Brennkraftmaschinen, wobei das Zündsystem einen eine Primärwicklung (2) enthaltenden Stromkreis aufweist, der einen Unterbrecher (5), Anschlußmittel für eine Spannungsquelle (4) und einen Schalter (6), enthält, von dem ein Teil (9) mit einem magnetisch anziehenden Körper verbunden oder von einem solchen gebildet ist, dadurch gekennzeichnet, daß der Schalterteil (9) dem tatsächlichen Transformatorkern (1) des Zündsystems benachbart angeordnet ist, so daß der Schalterteil (9) bewegt wird, um den Schalter entgegen einer Schließkraft in die Offenstellung zu bringen, wenn ein Magnetfeld durch den Transformatorkern (1) fließt.

2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß der Unterbrecher (5) mit dem Schalter (6) in Reihe geschaltet und so ausgebildet ist, daß seine Kontakte während des Zeitraumes, wenn ein Funken benötigt wird, geschlossen sind.

3. Vorrichtung nach Anspruch 2, dadurch gekennzeichnet, daß der Unterbrecher (5) so ausgebildet ist, daß ein umlaufender Nocken ein Kontaktpaar öffnet und schließt, derart, daß die Bewegung des Unterbrecherhebels ein Schließen der Kontakte bewirkt.

4. Vorrichtung nach Anspruch 2, dadurch gekennzeichnet, daß der Unterbrecher eine Photozelle aufweist, die durch Licht erregt wird, das eine Öffnung in einer umlaufenden Scheibe passiert, wobei die Länge der Öffnung die Zeit bestimmt, während der ein Strom von einem die Photozelle enthaltenden elektronischen Schaltkreis der Primärwicklung (2) des Transformators zugeführt wird, und somit die Funkendauer bestimmt.

5. Vorrichtung nach Anspruch 1, gekennzeichnet durch den Einschluß eines transistorisierten Zündsystems, das so aufgebaut ist, daß eine Zuführung des Arbeitsstromes zu der Primärwicklung (2) des Transformators über den Zeitraum erfolgt, der erforderlich ist, um den kontinuierlichen Strom von Hochspannungsimpulsen zu jeder Zündkerze (8) der Brennkraftmaschine zu erzeugen.

6. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß der Unterbrecherkontakt (5) zu dem Schalter (6) parallel geschaltet ist.

7. Vorrichtung nach Anspruch 6, dadurch gekennzeichnet, daß der den Schalter (6) enthaltende Parallelkreis außerdem einen TrennSchalter (15) enthält, und bei offenem TrennSchalter (15) das Zündsystem in konventioneller Weise Arbeitet.

8. Vorrichtung nach Anspruch 6 oder 7, dadurch gekennzeichnet, daß in dem den Schalter enthaltenden Parallelkreis eine Überlastsicherung (16) angeordnet ist.

9. Vorrichtung nach irgendeinem der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß der durch das Magnetfeld des Transformatorkernes (1) betätigbare Schalter (6) ein Reedschalter, ein Quecksilberschalter oder ein Wagnerscher Hammer ist.

10. Vorrichtung nach Anspruch 9, dadurch gekennzeichnet, daß dem Schalter (6) ein Kondensator (14) parallelgeschaltet ist, um die Lichtbogenbildung an den Kontakten des Schalters (6) zu verringern.

11. Vorrichtung nach irgendeinem der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß der Schalter (6) ein elektronischer Schaltkreis mit einer Photozelle ist, wobei der Schalterteil (9), an dem der magnetisch anziehende Körper angebracht ist, zwischen Stellungen bewegbar ist, in denen ein Lichtstrahl zu der Photozelle unterbrochen bzw. nicht behindert ist.

12. Vorrichtung nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß der Schalter (6) zwei Kontakte (11, 13) aufweist, von denen einer auf einem beweglichen Schaltarm (10) angeordnet und beispielsweise durch eine schwache Feder im Schließsinn gegen den anderen beaufschlagt ist und an einer magnetisch anziehenden Scheibe (9) angebracht ist, die dem Ende des Transformatorkerns (1) benachbart ist.

13. Einheit zur Umwandlung eines bestehenden Transformators eines Zündsystems, bespielsweise für eine Brennkraftmaschine, zur Schaffung der Vorrichtung nach Anspruch 1, wobei das Zündsystem einen die Primärwicklung (2) enthaltenden Stromkreis mit einem Unterbrecher (5) und Mitteln zum Anschluß an eine Spannungsquelle (4) aufweist, dadurch gekennzeichnet, daß die Einheit einen Schalter (6) enthält, dessen beide Kontakte (11, 13) durch Verbindungsleitungen in den Stromkreis der Primärwicklung (2) des Transformators einschaltbar sind, sowie eine Befestigungsvorrichtung zur Anbringung des Schalters (6) am Körper des Transformators derart, daß ein magnetisch anziehender Körper (9), der ein Teil des Schalters (6) bildet oder an einem solchen Teil angebracht ist, in dem axialen Magnetfeld des Transformatorkerns (1) liegt.

Drawing