EP0406509A1

EP0406509A1 - Method for making insulated conductor elements for connecting units to signal generators

Info

Publication number: EP0406509A1
Application number: EP89830396A
Authority: EP
Inventors: Dante Baldini
Original assignee: UBALIT SpA
Current assignee: UBALIT SpA
Priority date: 1989-06-09
Filing date: 1989-09-18
Publication date: 1991-01-09
Also published as: BR9002714A; KR910002058A; JPH0395887A; IT1233310B; KR920002768B1; CA2018468A1; IT8903512A0

Abstract

This method has been proposed for making an insulated conductor element 100 consisting of a flexible and electric conductor component 1, preferably in conducting silicon rubber, consisting of a cylindrical shaped portion 2, whose ends are attached to terminals 3,4, and an insulating flexible sheath 5, which is solid with and closely adheres to said cylindrical shaped portion 2, and which, by means of corresponding caps 6,7 also closely surrounds said terminals 3, 4 whereby, the latter are designed for connection to corresponding metal tips used for electric units or generators of electric signals.

Description

It is known that in the current ignition systems being used in combustion engines, electricity flows from the generator of electric signals (such as coils, distributors, or electronic ignition units) to the spark plug through an electric lead with a conducting core consisting of a thin copper or metal alloy wire, that is wound into a coil (constituting an inductance to limit what is known as radio interference) on a cylindrical shaped insulated support.
The conducting core is covered with a sheath and/or one or more layers of insulating material. The ends of the core are fixed to metal terminals which, by means of suitable metal tabs, are shaped in such a way as to make it possible for them to be fixed (connected) at the one end to the outer metal tang (metal tip) of the spark plug, and to be fixed at the other end to the corresponding metal tip to be found in the aforementioned generator of electric signals.
It is also known that metal terminals are normally electrically insulated by means of the sheath and caps, which are both made in natural or synthetic rubbers, or in plastic materials.
Therefore, each conductor element for transmitting electricity from the generator to the spark plug contains a metal core endpiece wound around its corresponding cylindrical shaped insulated support, which, in turn, is electrically insulated (the lead), two metal terminals (one for each end of the core) and two insulated caps (one for each terminal of the conductor element). The final version of this invention consists of a plural number of separately produced components (lead, terminals, tabs, caps) that have been duly tested prior to assembly; the conductor element produced in this way is then also subjected to testing.
In order to guarantee that the terminals are electrically insulated, the caps also have to be hermetically sealed against atmospheric humidity, the lead to be insulated, and the spark plug has to have ceramic insulation at the one end, and the lead to the signal generator to be insulated at the other end; it is for this purpose that the metal terminals and the leads, in particular, are forced into the axial holes connecting the cap cavities to the outside; since the diameter of said holes is smaller than that of the terminals and leads, the caps are frequently cut and/or damaged and consequently the conductor element has to be discarded.
The above point, along with the not inconsiderable amount of individual components rejected during testing, has considerable bearing upon the costs of the insulated conductor element.
The object of this invention is to propose a method that can be used for making insulated conductor elements performing the same functions as the aforementioned conductor elements, with improved manufacturing costs of the element and improved assembly times for mounting said elements onto internal combustion engines, by comparison with what is currently available on the market.
A further object of this invention is to propose insulated conductor elements that can be used to connect generators of electric signals to corresponding electric units without any radio interference, in such a way that only the slightest amount of rejects will be involved in their manufacture and assembly onto internal combustion engines, in such a way as to offer their corresponding terminals efficient protection against atmospheric humidity and lastly in such a way as to guarantee top performance in terms of the transmission of electricity from generator to spark plugs.
The component is preferably to be made in conducting silicon rubber.
The element proposed consists solely of a flexible electro-conductor component and an insulating sheath; the structural simplicity of the proposed element is obvious, it allows considerable savings to be made on the manufacturing costs, and is extremely practical in terms of electric performance, durability, protection against corrosive atmospheric agents and lack of radio interference.
Top electric performance is achieved because the component making the electric connections is manufactured as a single piece and its flexibility enables push connection of the terminals in question to the metal tips of either the electric charges or the generator, thus achieving reduced contact resistance for these connections, and consequently limiting current density, due to the large contact area between the terminals and metal tips.
The lack of assembled parts and of undue mechanical stress arising from the connections has a positive effect upon durability.
Protection against corrosive atmospheric agents is guaranteed by the sheath, which is solid with and closely adhering to the cylindrical shaped portion of the component, and by the caps, closely adhering to the portions of said metal tips that are immediately outside in relation to the terminals of the component that the metal tips are connected to.
The use of conducting silicon rubber enables a reduction in, or near elimination of, radio interference.
Any features of this invention that are not apparent from the above will be more easily understood from the following detailed description and reference to the attached drawings in which:

- Fig. 1 is a diagram showing a cross-section of the insulated conductor element proposed in this invention together with a spark plug.
- Figures 2 and 3 are diagrams showing enlarged cross-sections of the two versions of the terminals of the above element.

With detailed reference to these figures, 1 represents a flexible electro-conductor component, preferably made of conducting silicon rubber and having the same powers of conductivity as well-known electric conductors.
This component consists of a cylindrical-shaped portion, 2, whose ends, with the latter, form a single piece, said terminals (obviously electro-conductors) being referred to as the first and second terminal respectively, and given reference numbers 3 and 4.
No. 5 refers to a flexible insulating sheath (made of a synthetic resin, such as silicon or synthetic rubber) which is solid to and adhering to said cylindrical shaped portion, 2, and which also adheres to said terminals, 3 and 4, by means of the corresponding caps, 6 and 7, referred to respectively as the first and second cap.
Preferably terminals 3 and 4 are to be smaller in cross section than caps 6 and 7 are.
In the first version, the first cap, 6, closely adheres to the corresponding first terminal, 3, and the latter is centrally located on the seat, 8 (see Fig. 1).
This version can also be seen in Fig. 3, which shows the second cap, 7, corresponding to the second terminal, 4.
In the second version (shown in Fig. 2) the cross-section of the second terminal, 4, is smaller in diameter than the inside diameter of the second cap, 7; thus constituting a circular seat, 9.
The method for making element, 100, in the way described, i.e. of making it from component, 1, and sheath, 5, involves the following operations being carried out in the following order : the moulding of the afore-mentioned flexible insulating sheath, 5, the surrounding of a corresponding first core (not shown in the diagram) with sheath complete with caps, 6 and 7; the extraction of the core from the sheath, 5; the location in the first and second caps, 6 and 7, of the sheath of a second and third core respectively (neither of which are shown in the diagram); the injection, into the through hole of sheath, 5, of a mixture of liquid at such a temperature as will not alter the physical and chemical properties of the sheath.
The subsequent solidifying of the mixture, thus constitutes the combining of the sheath with the second and third cores to produce the flexible electro-conductor component, 1, consisting of the cylindrical-shaped portion, 2, forming the terminals, 3 and 4.
Finally the extraction of the second and third cores from the corresponding caps, 6 and 7 is accomplished.
The shape of either the one or the other of the two manufacturing cores allows the obtaining of either the one or the other of the two versions described above for the terminals 3 and 4 and their corresponding caps 6 and 7.
The surfaces of the sheath, 5, and component, 1, meet according to design and are joined together in one piece, so that in the terms of this invention, the component and the sheath constitute a single piece; this means that the formation of pockets of air between said surfaces can be avoided quite regardless of the values of mechanical stress and temperature, provided that these do not exceed the pre-determined limits the element will be subjected to during use.
Seat, 8, designed to locate the first terminal, 3, will be connected to the metal tip, 10, of a pre-determined electric charge, 11 (such as a spark plug, see Fig. 1).
The flexibility of the material used for the manufacture of terminal, 3, enables said interference-fit push connection to take place between terminal, 3, and metal tip, 10; it will therefore follow that said terminal will surround the metal tip, 10, at the side, by exerting a pre-determined pressure on the latter; this considerably limits contact resistance, which, together with the large contact area between the terminal and the metal tip, will constitute advantages that are obvious to an expert in this field.
Either seat, 8, designed for the second terminal, 4, in terms of the first version (Fig. 3), or the circular seat, 4, designed in terms of the second version (Fig. 2) are for interference-fit push connection, suited to the metal tips (which are not shown in the diagram) used in known generators of electric signals (such as coils, distributors and electronic ignition units); the previously mentioned advantages will also apply in this case.
The element 100 enables terminals 3 and 4 to be electrically connected to the corresponding metal tips of either an electric charge, on the one hand, or of a generator of electric signals, on the other hand; protection against humidity (more specifically against corrosive atmospheric agents) is offered by the caps 6 and 7 as each of the latter closely surrounds the portion of the electric tip (which is insulated if necessary like the spark plugs) immediately outside in relation to terminal 3 or 4, that said metal tip is connected to.
To sum up, the element 100 has the same function as the conductor elements mentioned in the introduction, but unlike the latter, no assembly operations are required; furthermore the operations for mounting element 100 onto the engines of automobiles do not require any particular adjustments to be made and are facilitated by the push connection of terminals 3 and 4 to the metal tips.
The method proposed makes an insulated conductor element that can be perfectly matched to the corresponding metal tip, and which optimizes electric performance, insulation and protection against atmospheric humidity.

Claims

1) Method for making insulated conductor elements electrically connecting electric charges to generators of electric signals, characterised in that the following operations are carried out in the following order: the moulding of a flexible insulating sheath (5), surrounding a corresponding first core, with said sheath complete with related caps (6 and 7) fitted to its ends; the extraction of said core from said sheath; the location in the first and second caps (6 and 7), of a second and third core respectively; the injection into the through hole of said sheath (5), of a mixture of liquid at such a temperature as will not alter the physical and chemical properties of said sheath (5), the subsequent solidifying of said mixture, thus combining with said sheath (5) and said second and third cores to produce a flexible electro-conductor component (1), consisting of a cylindrical shaped portion (2), which is solid with and adhering to the corresponding portion of the sheath whose ends, in the same place as said caps (6 7), form said terminals (3, 4); and the extraction of said second and third cores from their corresponding caps.

2) Method according to claim 1, characterised in that said terminals (3, 4) are extended axially for the length that does not excede the length of the corresponding caps (6, 7).

3) Method according to claim 1, characterised in that the rim of at least one of said terminals (3, 4) is solid with and closely adhering to the corresponding cap (6, 7), said seat (8) being centrally located on said terminal and designed for connection to either the metal tip (10) of the corresponding electric charge (11), or to the metal tip of said generator.

4) Method according to claim 1, characterised in that at least one of said terminals (3, 4), is smaller in cross section than the inside diameter of the corresponding cap (6, 7), thus constituting a circular seat (9) designed for connection to either the metal tip of a corresponding electric charge, or to the metal tip of said generator.

5) Method according to any of the previous claims whatsoever, characterized in that said flexible electro-conductor component (1), is made of conducting silicon rubber.

6) Insulated conductor element electrically connecting electric units to a generator of electric signals, characterised in that it consists of the following parts: a flexible electro-conductor component (1), consisting of a cylindrical shaped portion (2) whose ends are designed to form terminals (3, 4) as a single piece of said portion, said terminals being designed to be connected to metal tips (10), either of said electric units or of said generator; a flexible insulating sheath (5) solid to and closely adhering to said cylindrical shaped portion, and surrounding said terminals (3, 4) by means of corresponding caps.

7) Element according to claim 6, characterized in that said terminals (3, 4) are extended axially for a length not exceeding the length of the corresponding caps.

8) Element according to claim 6, characterized in that the rim of at least one of said terminals (3, 4) is solid with and adheres to the corresponding cap (6, 7), said seat (8) being centrally located on said terminal and designed for connection to either the metal tip (10) of the corresponding electric charge (11), or to the metal tip of said generator.

9) Element according to claim 6, characterized in that at least one of said terminals (3, 4) is smaller in cross section than the inside diameter of the corresponding cap (6, 7), constituting a circular seat (9) designed for connection to either the metal tip of a corresponding electric unit, or the metal tip of said generator.

10) Element according to any whatsoever of the above claims from 6 to 9, characterized in that said flexible electro-conductor component (1) is made of conducting silicon rubber.