EP1429424A1

EP1429424A1 - Electric terminal

Info

Publication number: EP1429424A1
Application number: EP02425758A
Authority: EP
Inventors: Antonio Falchetti
Original assignee: Meccanotecnica Codognese SpA
Current assignee: Meccanotecnica Codognese SpA
Priority date: 2002-12-10
Filing date: 2002-12-10
Publication date: 2004-06-16

Abstract

An electric terminal (1) to be connected to a complementary electric terminal (2) along a preestablished direction of connection (A-A) comprises a first (4) and a second (10) portion of conductive material between which an electric continuity is achieved. Advantageously, said second portion (10) protrudes from the first portion (4) in the direction of connection (A-A) so as to contact said complementary electric terminal during the connection operation before the complementary electric terminal (2) comes into contact with the first portion (4). Moreover, the conductive material of the second portion (10) has a lower electric conductivity than the electric conductivity of the conductive material of the first portion (4).

Description

The present invention relates to an electric terminal according to the pre-characterizing portion of claim 1.
It is known for electric installations on motor vehicles, lorries, three-wheelers and self-propelled operating machines, about the use of fuses having a suitable amperage for protecting the electric functions that are present therein.
Fuses are generally placed in a fuse box so as to be connected in a removable way to electric terminals that are the starting point of electric cables going towards the operating devices installed on the vehicle.
In case maintenance operations are to be carried out on the electric devices of the vehicle, such as for instance head lights, direction indicators, fans, battery, windscreen wipers and electric motors, it should be provided for the possibility to temporarily eliminate and subsequently recover the electric contact with the fuses, since high voltages, of around 80 V, and high currents, of around 30 A, within the electric installation can be dangerous for the operator carrying out maintenance operations on the installation.
In this case, after first switching off the operating device, the fuses are disconnected from their respective terminals.
Then, after completing and carrying out in full safety conditions the necessary maintenance operations, the electric connections with the fuses are recovered.
During the re-connection of the fuses with their respective terminals it might happen that, due to residual charges in the electric installation, the fuse is fitted in under charge.
Due to the nature of the materials used for terminals, mainly tinned copper with a high electric conductivity, peak currents can reach quite high values, which can certainly result - while fitting the fuse into its respective terminal - in an arc discharge in the contact area.
The electric discharge thus generated damages the contacts and, in extreme cases, due to the high temperature reached in the contact area, results in a welding between the copper contacts of the terminal and of the fuse.
The electric arc, therefore, is due to the high intensity of the current flowing from a terminal to the other because of the low resistivity of the material the terminals are made of, mainly tinned copper.
Under these circumstances there is a strong need for an electric connection terminal having such structural and functional characteristics as to prevent the damaging, deterioration or breaking of the ends of said terminals during connection and disconnection of the latter.
In particular, the most important step is the one in which the connection between the connectors of the electric terminals is established, i.e. the step in which electric arcs are very likely to form for the reasons disclosed above.
It is therefore desired to have a protection system preventing the formation of electric arcs.
The scope of the present invention is to provide an electric terminal having such structural and functional characteristics as to meet the aforesaid needs and at the same time to obviate the drawbacks mentioned referring to the state of the art.
Such problem is solved by means of an electric terminal according to claim 1.
Further characteristics and the advantages of the electric terminal according to the present invention will be evident from the following description having a mere indicative and non-limiting purpose, with reference to the enclosed figures, in which:

Figure 1 shows a perspective view of a terminal according to the present invention in an operating configuration at a time previous the connection with a complementary terminal,
Figure 2 shows an exploded view of the terminal in Figure 1 during an assembling step,
Figure 3 shows a perspective view of the terminal in Figure 2,
Figure 4 shows a plan view of the terminal in Figure 2,
Figure 5 shows a view from below of the terminal in Figure 2,
Figure 6 shows a side view of the terminal in Figure 2,
Figure 7 shows a front view of the terminal in Figure 2,
Figure 8 shows a sectioned view of the terminal in Figure 2 along section line VIII-VIII of Figure 2.

The following description relates to an electric terminal 1, in particular to a male terminal able to house, i.e. be connected to a complementary electric terminal 2, in particular a male terminal consisting of a blade 2 of a fuse 3.
The connection between the terminal 1 and the blade 2 occurs in a direction of connection indicated by axis A-A in Figure 1.
The terminal 1 comprises a first portion 4 and a second portion 10, both made of a conductive material, between which an electric continuity is achieved.
As shown in Figure 1, the aforesaid electric continuity between the first 4 and second 10 portion is achieved by direct physical contact, although said electric continuity can also be ensured in functionally equivalent ways.
The complementary terminal 2, i.e. the blade 2 of the fuse 3, is made of a conductive material commonly used for fuses, for instance tinned copper, and is known per se and shall not be described in further detail in the following.
The first portion 4 of the terminal 1 is obtained by cutting and folding from a sheet of conductive material, preferably a tinned copper alloy.
The first portion 4 extends in a main longitudinal direction corresponding to the direction of connection A-A.
The first portion 4 has a back portion 5 to be connected by means of a conductive element 6 to an electric installation not shown in the figures.
To this purpose the back portion 5 comprises a plurality of wings 5a, which are folded so as to engage a tab of a distribution plate or bar of a fuse box, or alternatively so as to seam the cable terminale of an electric cable.
In the example of Figure 8 the conductive element 6 to which the wings 5a are seamed is an electric cable made of tinned copper, which can ensure an excellent electric conductivity and, therefore, a low potential drop within the electric installation where it is fitted.
The first portion 4 has a front portion 7 interfacing in a removable way with the complementary terminal 2 or with another complementary terminal, so as to create an electric continuity between the fuse 3 and the electric cable 6, whose function is to connect directly the terminal 1 to an operating device of a vehicle not shown in the figures.
The front portion 7 is folded so as to form an open tubular element 8 extending in the longitudinal direction A-A, so as to enable the introduction of the blade 2 of the fuse 3 therein.
The second portion 10 of the terminal 1 shall contact the blade 2 of the fuse 3 before said blade 2 comes into contact with the first portion 4 of the terminal 1.
To said purpose the second portion 10 protrudes from the first portion 4 of the electric terminal 1, substantially in the direction of connection A-A.
Advantageously, the conductive material the second portion 10 is made of has a lower electric conductivity than the conductive material the first portion 4 is made of, so that the electric resistance of the portion 4 is lower than the electric resistance of the portion 10.
According to a preferred embodiment, the second portion 10 is made of steel, whose electric conductivity is at least one magnitude lower than tinned copper.
Preferably, the second portion 10 is provided with contact means 11 extending substantially in the direction of connection A-A.
More to the point, the contact means 11 are placed on the front edge 12 of the second portion 10.
Since, as above stated, the second portion' 10 protrudes from the first portion 4 in the direction of connection A-A, said portion 10 is placed opposite the complementary terminal 1 during the connection operation.
The contact means 11, therefore, cause an anticipated contact of the second portion 10 of the electric terminal 1 with the blade 2 with respect to the contact with the first portion 4 of the terminal 1.
According to a preferred embodiment and as shown in the enclosed figures, the contact means 11 consist of a pair of protuberances starting from the front edge 12 of the second portion 10 of the terminal 1.
In the example the aforesaid pair of protuberances consists of two opposed contact reeds 11 extending from the front edge 12.
A particularly efficient embodiment of the contact reeds 11 is shown in Figures 1-5, showing the undulating shape of the reeds 11.
Such shape allows to perform the main function of said reeds 11, i.e. to contact the blade 2 before the latter can come into contact with the portion 4 and at the same time to enable an introduction with a slight force fitting of the blade 2 into the terminal 1, so as to ensure a firm and stable contact between the blade 2 and the terminal 1.
The shape and the material of the contact reeds 11 allow said reeds 11 to be elastic enough to enable a small transversal deformation of said reeds with respect to the direction,of connection A-A during the connection of the blade 2 to the terminal 1.
The second portion 10 consists in a plate fastened by seaming to the first portion 4 on its front portion 7 forming the open tubular element 8.
In particular, said plate is associated outside to the open side of the tubular element 8.
The seaming is carried out through hooking means comprising a plurality of wings 22 engaging the tubular element 8 so as to hold and put into electric contact the portion 10 with the first portion 4 of the terminal 1.
In particular, the wings 22 engage each a corresponding seat 24 obtained in the inner wall 27 of the front portion 7 of the first portion 4.
Advantageously, the upper wall 20 of the plate 10 is provided with a wing 21 protruding outside and inclined towards the back portion 5 of the terminal 1.
The plate 10 is equipped on its side walls 30 with a pair of wings 23, one on each side, protruding outside and oriented parallel to said walls 30.
The wing 21 and the pair of wings 23 are stop means engaging with the surfaces of respective seats (not shown) of a supporting structure (not shown), for instance a terminal-holding housing made of plastic material.
The wing 21 is oriented so as to converge in the direction in which the terminal 1 fits into one of the seats of the aforesaid terminal-holding housing, and consequently to diverge in the opposite direction so as to prevent the extraction of the terminal 1 from the terminal-holding housing if the fuse 3, or the blade 2, has to be taken out of the electric terminal 1.
The portion 4 is provided on the inner wall 28 of the back portion 5 with friction means interfering with the cable 6 so as to increase its friction against the wings 5a and to improve the efficiency of the seaming of said wings 5a onto the cable 6.
In a preferred embodiment said friction means consist of a plurality of reliefs 32 obtained transversally with respect to the direction of connection A-A.
Advantageously, the plate 10 is provided with two elastic contact reeds 25 extending within the open tubular element 8, starting from the front edge 12 of the plate 10 to contact the inner wall 27 of the first portion 4.
Said reeds 25 perform the task of keeping the blade 2 engaged against the wall 27 when the blade 2 is fitted into the terminal 1, thus ensuring a good electric contact between the blade 2 and the portion 4 of the terminal 1.
While using the electric terminal 1 the advantages of the invention can be fully appreciated in case the electric terminal 1 is electrically charged when introducing the complementary terminal 2 of the fuse 3.
Thus, during the connection operation the second portion 10 of the terminal 1 contacts the blade 2 of the fuse 3 before said blade 2 comes into contact with the first portion 4 of the terminal 1.
In other words, the first portion of the electric terminal 1 coming into contact with the complementary terminal 2 is the second portion 10 protruding with respect to the first portion 4, and not the first portion 4, which is connected directly to the electric installation through the cable 6.
As previously described, the invention is particularly advantageous if the plate 10 consists of a conductive element having a lower electric conductivity than the one of the portion 4 of the terminal 1 and of the complementary terminal 2.
In the preferred embodiment steel is used, whose electric conductivity is,at least one magnitude lower than tinned copper, i.e. whose resistivity is at least one magnitude higher than tinned copper.
In particular, in the described example the plate 10 is made of steel, whereas the portion 4 and the blade 2 are made of tinned copper.
During the introduction of the blade 2 into the terminal 1, the particular choice of the conductive materials results in a decrease of the peak current flowing from one terminal to the other.
If the installation to which the terminal 1 is connected through the cable 6 has residual electric charges, the latter - as above stated - can lead to the formation of electric arcs near the contact area of the terminal 1 with the blade 2 of the fuse 3. This occurs in particular during the introduction of the blade 2 into the terminal 1.
During such operation, when the terminals 1 and 2 are at a very small distance one with respect to the other, though not yet in physical connection, the high electric field that is present, if higher than the maximum value tolerated by air before the latter ionizes, can lead to the formation of unwanted electric arcs between the terminals.
Using the terminal according to the present invention the likelihood of formation of electric arcs is almost set to zero, or even equal to zero, thanks to the presence of the contact reeds 11 discharging the electric charges through the steel the plate 10 is made of.
In particular, the interposition in the electric continuity between the blade 2 and the portion 4, both for instance made of copper, of a plate 10, preferably made of steel having a lower conductivity, leads to a decrease of the peak current.
The decrease of the peak current immediately results in a decrease of the electric field between the conductive elements of the terminals 1 and 2, thus preventing the formation of electric discharges.
As can be inferred from the description, the terminal according to the invention allows to meet the needs mentioned in the introduction to the present description and to overcome in the meanwhile the drawbacks mentioned referring to the state of the art.
As a matter of fact, with the terminal according to the invention it is possible to prevent the formation of electric arcs, thus eliminating the danger of breaking or damaging the electric contacts.
Obviously, in order to meet specific and urgent needs a technician in the field can make several changes and variants to the electric terminal as described above, all of them being nevertheless included in the scope of protection of the invention as defined by the following claims.

Claims

Electric terminal (1) to be connected to a complementary electric terminal (2) along a preestablished direction of connection (A-A), said electric terminal (1) comprising a first (4) and a second (10) portion of conductive material between which an electric continuity is achieved, characterized in that

said second portion (10) protrudes from said first portion (4) substantially in said preestablished direction of connection (A-A) so as to contact said complementary electric terminal (2) during the connection operation before said complementary electric terminal (2) comes into contact with said first portion (4), and

the conductive material of the second portion (10) has a lower electric conductivity than the electric conductivity of the conductive material of the first portion (4).
Terminal according to claim 1, wherein said second portion (10) protrudes from said first portion (4) through contact means (11) substantially extending in said direction of connection (A-A).
Terminal according to claim 2, wherein said contact means (11) are arranged on the front edge (12) of said second portion (10), which is placed opposite said complementary electric terminal (2) during the connection operation.
Terminal according to claim 2, wherein said contact means (11) comprise a pair of protuberances.
Terminal according to claim 4, wherein said pair of protuberances consists of contact reeds shaped so as to enable a coupling with interference of said complementary electric terminal (2) with said electric terminal (1).
Terminal according to claim 1, wherein said second portion (10) of said electric terminal (1) is associated integrally to said first portion (4).
Terminal according to claim 1, wherein said electric terminal (1) is a female terminal and said complementary electric terminal (2) is a male terminal.
Terminal according to claim 1, wherein said electric terminal (1) is a male terminal and said complementary electric terminal (2) is a female terminal.
Terminal according to claim 1, wherein said second portion (10) is associated outside to said first portion (4).
Terminal according to claim 9, wherein said second portion (10) is fastened by seaming to the first portion (4).
Terminal according to claim 1, wherein said second portion (10) comprises holding means (21, 23) able to engage surfaces of a seat of a supporting structure.
Terminal according to claim 1, wherein the conductive material of said first portion (4) and of said complementary electric terminal (2) is tinned copper.
Terminal according to claim 1, wherein the conductive material of said second portion (10) is steel.
Terminal according to claim 7, wherein said first portion (4) is an open tubular element (8) obtained by cutting and folding.
Terminal according to any of the preceding claims, wherein said:second portion (10) is a plate.
Terminal according to claims 14 and 15, wherein said plate is associated outside to the open side of said tubular element.