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EP 1 146 227 B1 |
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EUROPEAN PATENT SPECIFICATION |
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Mention of the grant of the patent: |
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13.10.2004 Bulletin 2004/42 |
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Date of filing: 24.02.2001 |
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Method of assembly of ignition pencil coils
Verfahren zur Herstellung von Zündspulen
Methode d'assemblage de bobines d'allumage
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Designated Contracting States: |
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DE FR IT |
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Priority: |
13.04.2000 LU 90563
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Date of publication of application: |
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17.10.2001 Bulletin 2001/42 |
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Proprietor: Delphi Technologies, Inc. |
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Troy, MI 48007 (US) |
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Inventor: |
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- Igot, Alain
6740 Etalle (BE)
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Representative: Beissel, Jean et al |
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Office Ernest T. Freylinger S.A.,
234, route d'Arlon,
B.P. 48 8001 Strassen 8001 Strassen (LU) |
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References cited: :
GB-A- 2 339 596 US-A- 5 218 936
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US-A- 5 109 828 US-A- 5 241 942
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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Field of the invention
[0001] The present invention generally relates to a method of assembly of ignition pencil
coils.
Background of the invention
[0002] Recent developments in ignition systems have led to the introduction of ignition
pencil coils. The actual practice is to assemble each pencil coil individually on
a cylinder head. However, it would be profitable to find a simple method for assembling
those ignition pencil coils into a unit of ignition pencil coils, to simplify their
mounting on cylinder heads.
[0003] In today's prototypes, a unit of ignition pencil coils comprises one steel bracket
acting as rigid support, on which the four pencil coils (one per cylinder) are fastened
by means of screws, with one large seal between the coils and the bracket. A printed
circuit board connects the four pencil coils to a primary connector mounted at one
end of the printed circuit board. For protection, this assembly is generally placed
into a plastic housing, which is mounted on the bracket by means of two screws. Such
a unit of pencil coils requires a complicated assembly process, thus resulting in
high manufacturing costs and risks of manufacturing faults. Hence, there is a strong
need for a simpler method of assembly of ignition pencil coils.
Object of the invention
[0004] The object of the present invention is to provide a simple and efficient method of
assembly of ignition pencil coils. This object is achieved by a method as claimed
in claim 1.
Summary of the invention
[0005] A method of assembly of ignition pencil coils in accordance with the invention comprises
the following steps:
(a) providing a leadframe comprising tracks for the electrical connection of said
ignition pencil coils;
(b) overmolding said leadframe with a polymer so as to form a casing for said tracks
while leaving accessible track terminals for connecting coil terminals of said ignition
pencil coils ; and
(c) fastening said ignition pencil coils to said casing and connecting electrically
said coil terminals to said accessible track terminals.
[0006] The great advantage of the method of the invention is its simplicity. Within a few
steps, the ignition pencil coils are assembled into a unit of ignition pencil coils.
In conventional units of pencil coils, the support for the coils is supplied by a
bracket and the electrical connection by a printed circuit board. In the present method,
the use of an overmolded leadframe provides the electrical circuit for connecting
the ignition pencil coils as well as a support for the latter. Moreover, the casing
protects and insulates the tracks. The pencil coils may be fastened to the casing
by thermal or ultrasonic welding. A plastic portion of the body of the pencil coils
can e.g. be soldered to the casing. The electrical connection between the coil terminals
and the accessible track terminals may be carried out by welding or soldering. However,
this electrical connection does not necessarily require soldering as the coils are
fixed to the casing. Indeed, the coil terminals may be formed as female terminals
for receiving the male-shaped accessible track terminals.
[0007] The casing may comprise first fastening means and each ignition pencil coil may comprises
second fastening means, which are capable of cooperating with the first fastening
means for fastening said ignition pencil coils to said casing. The first and second
means may be e.g. at least partially soldered or welded together. It is also possible
to deform one of the fastening means. However, the first and second means may be advantageously
designed so as to provide a snap-fit connection, thereby enabling a very simple and
rapid fastening of the coils to the casing.
[0008] In a preferred embodiment, the first fastening means comprises at least one slot
per pencil coil and the second fastening means of each pencil coil comprises at least
one tab, which can be received in a respective slot of the first fastening means.
As explained before, the coils may be fastened to the casing by welding the tabs to
the casing, once inserted through the slots. Another possibility is to heat the tabs,
once inserted through the slot, to deform them. However, the tabs and slots may alternatively
be designed so as to provide a snap-fit connection. This can be achieved by providing
a nose at the end of each tab. It shall further be noticed that the location of the
slots in the casing can be used to define an orientation, or positioning, of the pencil
coils. Thus connection errors can be avoided, as there is only one way of assembling
the ignition coils to the casing.
[0009] Advantageously, openings are provided in the casing, each opening being capable of
receiving an end of an ignition coil. Such openings may serve for guiding and positioning
the ignition coils during assembly of the ignition coils. The coil end bearing the
coil terminals shall be in particular received in such an opening. These openings
are preferably arranged during step (b) and formed as sockets. Such sockets may ensure
a rigid holding of the ignition coils after assembly.
[0010] Preferably, the leadframe is stamped out of a metal sheet. Therefore, after stamping
out, the tracks of the leadframe are generally held together by spacers. Those spacers
are preferably cut before, during or after step (b) in order to individualize said
tracks.
[0011] Track ends and spacers may be at least partially bent to form accessible track terminals.
This will preferably take place after the cutting, at least for the spacers. The accessible
track terminals are advantageously perpendicular to the tracks, so as to offer a large
surface of contact with the coil terminals.
[0012] One end of the leadframe is preferably formed as a primary connector. In other words,
the tracks at this end of the leadframe are shaped and spaced as the terminals of
a conventional connector. Then, during step (b) a housing may be formed around said
primary connector to ensure an easy and watertight connection of the ignition coil
unit to a connector of the ignition system.
[0013] Advantageously, mounting bushings are fixed to the leadframe, preferably to the ground-tracks
thereof, before step (b), and are subsequently overmolded with said leadframe. It
follows that the ignition coil unit can be directly mounted on a cylinder head. Moreover,
the mounting bushings ensure the grounding of the electric circuit of the ignition
coil unit.
[0014] A RFI capacitor may be mounted to the leadframe before step (b) and overmolded with
the leadframe.
[0015] Preferably, said coil terminals and said track terminals, as well as said connector
tabs are embedded in a curable resin. Hence, the electrical connections are protected
and the ignition coils are locked in their sockets.
[0016] The method of the invention is particularly suited for assembling ignition pencil
coils. Within a few simple steps, there is obtained an engine mountable unit of ignition
pencil coils, consistent with the actual requirements of ignition systems: use of
ignition pencils coils, integrated RFI capacitor, good sealing of electrical connections.
Moreover, the method of assembly is very simple, namely because of a reduced number
of elements. This results in a reduction in cost and weight, and in improved performance
of unit ignition pencil coils.
Brief description of the drawings
[0017] The present invention will now be described, by way of example, with reference to
the accompanying drawings, in which:
Fig.1: is a view of an unit of ignition pencil coils obtained according to a preferred
embodiment of the method of the invention;
Fig.2: is a top view of the unit shown in Fig.1;
Fig.3: is a partial view of the unit shown in Fig.1, without the casing;
Fig.4: shows the casing before introduction of the pencil coils.
Detailed description of a preferred embodiment
[0018] In order to rapidly and easily assemble ignition coils into a unit of ignition pencil
coils, the present invention proposes the use of an overmolded leadframe, i.e. a structure
featuring the electrical circuit for connecting the pencil coils and capable of supporting
the pencil coils. A unit 10 of ignition pencil coils, shown in Fig.1, comprises four
ignition pencil coils 12. This unit 10 has been obtained in accordance with a preferred
embodiment of the method of the invention, which will now be described in detail.
[0019] In a first method step (a), a leadframe 14 (partially shown in Fig.3) is stamped
out of a metal sheet. At the issue of the stamping machine, the leadframe 14 consists
of tracks 16 held together by spacers 17. The tracks 16 provide the electrical circuit
necessary to connect the ignition pencil coils 12 to the ignition system (not shown).
The spacers 17 are metal strips left from the metal sheet to hold the tracks 16. At
one of its ends, the leadframe 14 is formed as a primary connector, for connection
with the ignition system (this end of the leadframe 14 is not shown). This means that
at this end of the leadframe 14, the tracks 16 are shaped and spaced as the terminals
of a conventional connector.
[0020] Advantageously, two mounting bushings 18 are subsequently fixed to the leadframe
14. They will later permit the insertion of screws through the ignition coil unit
10 for its mounting on the cylinder head of an engine. It shall be noted that an optional
RFI capacitor (not shown) may be connected to the leadframe 14 at this point of the
method.
[0021] In the next step (b), the leadframe 14 is overmolded with a polymer so as to form
a casing 20 for the tracks 16. The part as obtained at the issue of the injection
molding machine is shown in Fig.4. It consists of a plastic casing (casing 20) with
inner electric circuit (tracks 16).
[0022] In fact, step (b) preferably comprises several sub-steps. Firstly, the leadframe
14 is placed into a mold. Then, the spacers 17 are cut in order to individualize the
tracks 16, thereby forming the electric circuit. As a matter of fact, the mold is
designed so that the tracks 16 may be kept in position after they have been individualized,
i.e. after cutting of the spacers 17, and until the polymer is injected. It shall
also be noticed that the positions of the spacers 17 in the leadframe 14 may be advantageously
defined in such a way that some of them may serve as track terminals 22 after cutting.
Once the spacers have been cut, all the parts of the circuit that shall serve as track
terminals 22 are bent to an angle of 90° with regard to the rest of the tracks 16.
This may be seen in Fig.3 where the ignition coil unit 10 of Fig.1 is illustrated
without its casing 20. The parts of the circuit used as track terminals are preferably
track ends 24 or spacers 17. It will be noticed that the cutting and bending could
also take place after overmolding. In Fig.3, the pencil coils 12 are connected to
the track terminals 22, which is not yet the case at this step of the method. However,
this figure shows the advantage of bent track terminals 22: a greater area of contact
between coil terminals 26 and track terminals 22. It is also shown how the mounting
bushings 18 are assembled to the leadframe 14, and will permit to ground the circuit
once mounted onto the engine. Finally, a polymer is injected into the mold, and the
tracks 16, together with the RFI capacitor and the bushings 18 are overmolded with
the polymer. It is clear that in order to connect the track terminals 22 to the coil
terminals 26, the track terminals 22 have to be accessible. Therefore, the mold is
preferably designed in such a way that the casing comprises openings 28, in which
the track terminals 22 protrude, and are thereby accessible. Such an opening 28 is
represented in Fig.2, which shows a top view of the ignition coil unit 10 of Fig.1
(only one opening 28 per casing 20 is shown in the Figures). As a matter of fact,
the mold is preferably designed so that the casing 20 is provided with socket-shaped
openings 28, which shall serve for positioning, guiding and connecting the pencil
coils 12. The sockets are indicated by reference sign 30 and can be easily identified
in Fig.4.
[0023] As mentioned earlier, one end of the leadframe 14 is formed as a primary connector.
Therefore, during the overmolding at step (b) a housing 31 (see Fig.4) is formed around
this primary connector to permit an easy and watertight connection of the ignition
coil unit 10 to a primary connector of the ignition system.
[0024] Once the casing 20 is obtained, a pencil coil 12 is introduced into each socket 30
so as to bring the coil terminals 26 in contact with the track terminals 22. It shall
be noticed that the pencil coils 12 are advantageously provided with two orientation
tabs 32 (see Fig.4 and Fig.1) that fit into two slots 34 of the casing 20. Those tabs
32 and slots 34 may differ in size, shape or position, so that there is only one way
of inserting the pencil coils 12 in the sockets 30, thereby avoiding connection errors
of the coils 12.
[0025] In the next step (c), the pencil coils 12 are firstly fastened to the casing 20,
e.g. by welding the tabs 32 to the casing 20. Both thermal and ultrasonic welding
is appropriate. Then, the coil terminals 26 are firmly attached to the track terminals
22 to ensure a good electrical connection. This connection is shown in Fig.3 and can
be carried out by soldering or welding, and preferably by spot-welding.
[0026] After that, a curable resin is poured in each opening 28 in order to seal them and
to embed the track terminals 22 and coil terminals 26 in the resin to insulate them.
As a result, the connections are protected from the environment and the pencil coils
12 are securely locked in their sockets 30.
[0027] It shall be appreciated that the ignition coil unit 10 obtained with the present
method, as shown in Fig.1, is ready for use. It can easily be mounted on a cylinder
head by inserting two screws through the bushings 18 and screwing in the cylinder
head. The ignition coil unit 10 is sealed, features an integrated RFI capacitor, mounting
bushings, ignition pencil coils, and a primary connector.
1. A method of assembly of ignition pencil coils comprising the steps of:
(a) providing a leadframe (14) comprising tracks (16) for the electrical connection
of said ignition pencil coils (12);
(b) overmolding said leadframe (14) with a polymer so as to form a casing (20) for
said tracks (16), while leaving accessible track terminals (22) for connecting coil
terminals (26) of said ignition pencil coils (12); and
(c) fastening said ignition pencil coils (12) to said casing (20) and connecting electrically
said coil terminals (26) to said accessible track terminals (22).
2. The method according to claim 1, characterized in that said coil terminals (26) and said accessible track terminals (22) are connected by
welding or soldering.
3. The method according to claim 1 or 2, characterized in that said ignition pencil coils (12) are fastened to said casing (20) by thermal or ultrasonic
welding.
4. The method according to anyone of the preceding claims, characterized by the step of providing openings (28) in said casing (20), each opening (28) being
capable of receiving an end of an ignition pencil coil (12).
5. The method according to claim 4, characterized in that said openings (28) are arranged during step (b) and are formed as sockets (30).
6. The method according to anyone of the preceding claims, characterized in that said casing (20) comprises first fastening means and each ignition pencil coil (12)
comprises second fastening means, which are capable of cooperating with said first
fastening means for fastening said ignition pencil coils (12) to said casing (20).
7. The method according to claim 6, characterized in that said first fastening means comprises at least one slot (34) per pencil coil (12)
and in that said second fastening means of each pencil coil (12) comprises at least one tab (32),
which can be received in said at least one slot (34).
8. The method according to claim 6 or 7, characterized in that said first and second fastening means are designed so as to provide a snap-fit connection.
9. The method according to anyone of the preceding claims, characterized in that said leadframe (14) is stamped out of a metal sheet.
10. The method according to claim 9, wherein after stamping out, said tracks (16) are
held together by spacers (17), characterized in that said spacers (17) are cut in order to individualize said tracks (16) before, during
or after step (b).
11. The method according to claim 10, characterized in that at least one of said tracks (16) is partially bent so as to form an accessible track
terminal (26).
12. The method according to claim 10 or 11, characterized in that after cutting, at least one of said spacers (17) is partially bent to form an accessible
track terminal (22).
13. The method according to anyone of the preceding claims, characterized in that one end of said leadframe (14) is formed as a primary connector; and in that during step (b) a housing (31) is formed around said primary connector.
14. The method according to anyone of the preceding claims, characterized in that mounting bushings (18) are fixed to the leadframe (14) before step (b); and in that said mounting bushings (18) are overmolded with said leadframe (14).
15. The method according to anyone of the preceding claims, characterized in that a RFI capacitor is mounted on said leadframe (14) before step (b); and in that said RFI capacitor is overmolded with said leadframe (14).
16. The method according to anyone of the preceding claims, characterized by the step of embedding said coil terminals (26) and said track terminals (22) in a
curable resin.
1. Verfahren zur Herstellung von Stabzündspulen, umfassend die Schritte zum:
(a) Bereitstellen eines Leiterrahmens (14), der Leiterbahnen (16) für die elektrische
Verbindung der Stabzündspulen (12) umfasst;
(b) Umspritzen des Leiterrahmens (14) mit einem Polymer, um so ein Gehäuse (20) für
die Leiterbahnen (16) auszubilden, wobei zugängliche Leiterbahnanschlüsse (22) zum
Anschließen der Spulenanschlüsse (26) der Stabzündspulen (12) erhalten bleiben; und
(c) Befestigen der Stabzündspulen (12) am Gehäuse (20) und elektrischen Verbinden
der Spulenanschlüsse (26) mit den zugänglichen Leiterbahnanschlüssen (22).
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die Spulenanschlüsse (26) und die zugänglichen Leiterbahnanschlüsse (22) durch Schweißen
oder Löten verbunden werden.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Stabzündspulen (12) durch thermisches Schweißen oder Ultraschallschweißen am
Gehäuse (20) befestigt werden.
4. Verfahren nach irgendeinem der vorangehenden Ansprüche, gekennzeichnet durch den Schritt des Bereitstellens von Öffnungen (28) im Gehäuse (20), wobei jede Öffnung
(28) ein Ende einer Stabzündspule (12) aufnehmen kann.
5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, dass die Öffnungen (28) bei Schritt (b) angeordnet und als Buchsen (30) ausgebildet werden.
6. Verfahren nach irgendeinem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass das Gehäuse (20) erste Befestigungsmittel urnfasst und dass jede Stabzündspule (12)
zweite Befestigungsmittel umfasst, die mit den ersten Befestigungsmitteln zusammenwirken
können, um die Stabzündspulen (12) am Gehäuse (20) zu befestigen.
7. Verfahren nach Anspruch 6, dadurch gekennzeichnet, dass das erste Befestigungsmittel mindestens einen Schlitz (34) pro Stabzündspule (12)
umfasst und dass das zweite Befestigungsmittel jeder Stabzündspule (12) mindestens
einen Zapfen (32) umfasst, der in dem mindestens einen Schlitz (34) aufgenommen werden
kann.
8. Verfahren nach Anspruch 6 oder 7, dadurch gekennzeichnet, dass die ersten und zweiten Befestigungsmittel so ausgelegt werden, dass sie eine Schnappverschluss-Verbindung
ergeben.
9. Verfahren nach irgendeinem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass der Leiterrahmen (14) aus einem Metallblech ausgestanzt wird.
10. Verfahren nach Anspruch 9, wobei nach dem Ausstanzen die Leiterbahnen (16) durch Zwischenstücke
(17) zusammengehalten werden, dadurch gekennzeichnet, dass die Zwischenstücke (17) zerschnitten werden, um die Leiterbahnen (16) vor, bei oder
nach Schritt (b) zu individualisieren.
11. Verfahren nach Anspruch 10, dadurch gekennzeichnet, dass mindestens eine der Leiterbahnen (16) teilweise gebogen wird, um so einen zugänglichen
Leiterbahnanschluss (26) auszubilden.
12. Verfahren nach Anspruch 10 oder 11, dadurch gekennzeichnet, dass nach dem Zerschneiden mindestens eines der Zwischenstücke (17) teilweise gebogen
wird, um einen zugänglichen Leiterbahnanschluss (22) auszubilden.
13. Verfahren nach irgendeinem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass ein Ende des Leiterrahmens (14) als ein Primärverbinder ausgebildet wird; und dass
bei Schritt (b) ein Steckergehäuse (31) rings um den Primärverbinder ausgebildet wird.
14. Verfahren nach irgendeinem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass vor Schritt (b) Montagebuchsen (18) am Leiterrahmen (14) befestigt werden; und dass
die Montagebuchsen (18) mit dem Leiterrahmen (14) umspritzt werden.
15. Verfahren nach irgendeinem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass vor Schritt (b) ein RFI-Kondensator am Leiterrahmen (14) befestigt wird; und dass
der RFI-Kondensator mit dem Leiterrahmen (14) umspritzt wird.
16. Verfahren nach irgendeinem der vorangehenden Ansprüche, gekennzeichnet durch den Schritt des Einbettens der Spulenanschlüsse (26) und der Leiterbahnanschlüsse
(22) in einem aushärtbaren Harz.
1. Procédé d'assemblage de bobines-crayon d'allumage, comprenant les étapes qui consistent
à :
(a) fournir une grille de connexion (14) comprenant des pistes (16) pour la connexion
électrique desdites bobines-crayon d'allumage (12);
(b) mouler un polymère par-dessus ladite grille de connexion (14) de manière à former
un boîtier (20) pour lesdites pistes (16) tout en laissant des bornes de piste accessibles
(22) en vue de la connexion avec les bornes de bobine (26) desdites bobines-crayon
d'allumage (12) ; et
(c) fixer lesdites bobines-crayon d'allumage (12) sur ledit boîtier (20) et connecter
électriquement lesdites bornes de bobine (26) auxdites bornes de piste accessibles
(22).
2. Procédé selon la revendication 1, caractérisé en ce que lesdites bornes de bobine (26) et lesdites bornes de piste accessibles (22) sont
connectées par soudage ou brasage.
3. Procédé selon la revendication 1 ou 2, caractérisé en ce que lesdites bobines-crayon d'allumage (12) sont fixées sur ledit boîtier (20) par soudage
thermique ou ultrasonique.
4. Procédé selon l'une quelconque des revendications précédentes, caractérisé par l'étape consistant à prévoir des ouvertures (28) dans ledit boîtier (20), chaque
ouverture (28) étant capable de recevoir une extrémité d'une bobine-crayon d'allumage
(12).
5. Procédé selon la revendication 4, caractérisé en ce que lesdites ouvertures (28) sont réalisées pendant l'étape (b) et sont formées en tant
que douilles (30).
6. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que ledit boîtier (20) comprend un premier moyen de fixation et chaque bobine-crayon
d'allumage (12) comprend un second moyen de fixation capable de coopérer avec ledit
premier moyen de fixation afin de fixer lesdites bobines-crayon d'allumage (12) sur
ledit boîtier (20).
7. Procédé selon la revendication 6, caractérisé en ce que ledit premier moyen de fixation comprend au moins une fente (34) par bobine-crayon
(12) et en ce que ledit second moyen de fixation de chaque bobine-crayon (12) comprend au moins une
patte (32) qui peut être reçue dans ladite au moins une fente (34).
8. Procédé selon la revendication 6 ou 7, caractérisé en ce que lesdits premier et second moyens de fixation sont conçus de manière à fournir une
liaison par encliquetage.
9. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que ladite grille de connexion (14) est estampée à partir d'une feuille de tôle.
10. Procédé selon la revendication 9, dans lequel, après l'estampage, lesdites pistes
(16) sont maintenues ensemble par des éléments d'écartement (17), caractérisé en ce que lesdits éléments d'écartement (17) sont coupés afin d'individualiser lesdites pistes
(16) avant, pendant ou après l'étape (b).
11. Procédé selon la revendication 10, caractérisé en ce qu'au moins une desdites pistes (16) est partiellement pliée afin de former une borne
de piste accessible (26).
12. Procédé selon la revendication 10 ou 11, caractérisé en ce que, après la coupe, au moins un desdits éléments d'écartement (17) est partiellement
plié afin de former une borne de piste accessible (22).
13. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce qu'une extrémité de ladite grille de connexion (14) est formée en tant que connecteur
primaire et en ce que, pendant l'étape (b), un boîtier (31) est formé autour dudit connecteur primaire.
14. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que des douilles de montage (18) sont fixées sur la grille de connexion (14) avant l'étape
(b) et en ce qu'on procède à un moulage par-dessus lesdites douilles de montage (18) et par-dessus
ladite grille de connexion (14).
15. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce qu'un condensateur RFI est monté sur ladite grille de connexion (14) avant l'étape (b)
et en ce qu'on procède au moulage par-dessus ledit condensateur RFI et par-dessus ladite grille
de connexion (14).
16. Procédé selon l'une quelconque des revendications précédentes, caractérisé par l'étape consistant à enrober lesdites bornes de bobine (26) et lesdites bornes de
piste (22) dans une résiné durcissable.