EP0623971B1

EP0623971B1 - Improved method for the connection of heater elements

Info

Publication number: EP0623971B1
Application number: EP94107233A
Authority: EP
Inventors: Giansante Antoniazzi; Claudio Fattorel
Original assignee: IRCA SpA Industria Resistenze Corazzate e Affini
Current assignee: IRCA SpA Industria Resistenze Corazzate e Affini
Priority date: 1993-05-07
Filing date: 1994-05-09
Publication date: 1996-09-04
Anticipated expiration: 2014-05-09
Also published as: DE69400461T2; EP0623971A2; ES2094587T3; ITPN930032A0; IT1268522B1; EP0623971A3; DE69400461D1; ITPN930032A1

Description

The present invention relates to a method for making connections between electric circuits disposed on an insulating support, including the steps of applying a plurality of terminals to said insulating support, said step of applying said plurality of terminals is carried out by mounting at least one conductive member on said insulating support by inserting projections extending therefrom into apertures formed in said insulating support, and mechanically and electrically connecting terminal ends of said electric circuits to said plurality of terminals.
The technology for making connections of this type is generally known, and is employed in practically identical manner by different manufacturers, apart from certain marginal variations mainly due to different physical configurations of the resistor elements and the associated supports.
This technology is substantially based on a manufacturing cycle which shall be briefly outlined in the following in order to facilitate comparison to the method of the present invention to be described subsequently.
In the known manufacturing cycle, the first step consists in forming the insulating support with a number of apertures at locations corresponding to the terminal ends of the resistance circuits; the second step consists in connecting the terminal ends of the resistance circuits to conductor elements adjacent the locations of respective apertures; the third step consists in rivetting the conductor elements to the insulating support by means of rivets passing through respective apertures, to thereby establish reliable mechanical and electrical connections of the conductor elements to the associated rivets; and the fourth step consists in connecting the rivets to respective power supply terminals in a per se known manner, for instance by soldering.
While this known process is sufficiently simple and safe, it suffers from the inconvenience of being a manual process throughout; in view of the severe competition in the field of large-scale industrial production, this extensive use of manual labour results in an inacceptable cost increase, apart from the unavoidable occurrence of quality variations.
In order to reduce the number of assembly steps, reference document DE-A-30 42 417 discloses a method for the connection of heater elements with terminals. The terminals are part of a conductive member which comprises a rivet type projection. In a first step, the rivet type projection is inserted in apertures of the insulating support. One end of the rivet type projection is formed like a flange and abuts against the insulating support. The other end projects through the insulating support. The diameter of the rivet type projection is about equal to the diameter of the apertures in the insulating support. In a consecutive step, the projecting end of the rivet type projection is bent over in order to clamp the insulating support between the flange and the bent over end of the rivet type projection. Even though the number of assembly steps is reduced, this method is still not satisfactory.
It would therefore be desirable, and is in fact the object of the present invention, to provide a method permitting resistance circuits and the like to be connected to respective power supply terminals in a fully automatic manner by the employ of actually available technologies.
This object is achieved by said conductive member being a sheet member being formed with a plurality of outwards projecting tongues, and that said sheet member being positioned so that said tongues coincide with respective terminal ends of said electric circuits, said tongues being bent 180° upon themselves to form two legs for said terminal ends to be received therebetween, and that said sheet member is divided into several separate sheet elements by the execution of multiple cuts at selected locations and the removal of sheet sections extending between adjacent cuts, and that said projections inserted into said apertures and projecting from said insulating support are bent over the edges of said apertures in a locking fit.
A method according to the present invention is preferably carried out by employing an electric circuit disposed on an insulating support and connected to a flat power supply terminal according to claim 5.
The invention will be more fully understood from the following description, given by way of example with reference to the accompanying drawings, wherein:

fig. 1: shows a component to be mounted on a support as a first step of the method according to the invention,
figs. 2 and 3: show and end view and a top plan view, respectively, of a heater circuit in a state attained in a second step of the method,
fig. 4: shows a longitudinally sectioned view of the assembly of fig. 3,
figs. 5 and 6: show the assembly of figs. 3 and 4 at the end of a subsequent step of the method, and
fig. 7: shows the assembly of fig. 5 in the state attained in a final step of the method.

The method according to the invention is substantially based on the provision that the connections between power supply conductors and the terminal ends of electric circuits are made by using one-piece conductive sheet members adapted to be automatically mounted in apertures suitably formed in an insulating suport and to be similarly connected to the terminal ends of electric circuits; for a better understanding of the invention, it shall be supposed that these electric circuits are resistor circuits, it being understood, however, that the invention is similarly applicable to any kind of electric circuits, and particularly to resistor circuits for air heating purposes.
With reference to the drawings, there is shown an insulating support 1, typically a mica plate, supporting one or several elongate resistor circuits 2 mounted in respective rows of apertures suitably formed therein. At the ends of support 1, each resistor circuit terminates in respective terminal ends 2a projecting from support 1 at the same side thereof.
In a first step of the method to be described, a single preferably metallic conductive sheet member 5 of elongate shape is attached to one or each end portion 3 of support 1 provided with suitable apertures 4. Each sheet member 5 is pre-shaped to present a plurality of tongues 6 projecting from its plane at right angles thereto to coincide with terminal ends 2a for connection there to, and a number of orthogonally extending projections to be received in apertures 4.
For reasons to be explained later, tongues 6 are formed on conductive sheet member 5 at sufficiently wide spacings. In addition, tongues 6 are pre-bent at 180° upon themselves to thus form a pair of legs adapted to embrace respective terminal ends 2a.
In the course of this first step, the projections extending from conductive sheet member 5 are inserted into apertures 4 of insulating support 1 and bent over the edges thereof so as to securely fix the sheet member on the support.
Sheet member 5 is additionally provided with flat terminal elements 7 likewise projecting therefrom at right angles and adapted to be used as male contacts in flat plug connectors.
As the second step of the method, terminal ends 2a are introduced between the pairs of legs formed by the tongues 6 of sheet member 5 (fig. 4).
In the third step of the method, the two legs formed by each tongue 6 are clamped together so that terminal ends 2a are firmly retained therebetween, thus providing at the same time a reliable electric connection (figs. 5 and 6).
In the fourth step, sheet member 5 is divided into several separate sheet elements 6a, 6b, 6c by performing, preferably simultaneously, multiple cuts at selected locations, and removing the sheet sections between adjacent cuts (fig.7).
The locations of the cuts are selected so that

a) there is obtained at least one pair of sheet elements 6a and 6b each connected to at least one of the above defined resistor circuits by the described clamped connection between respective tongues 6 and terminal ends 2a, and
b) each of the sheet elements 6a, 6b has at least one of the flat terminal elements 7 thereon so as to permit each resistor circuit to be independently energized.

In another solution shown at the bottom end of fig. 7, sheet member 5 may be cut to provide a centrally located sheet element 6c permitting to selectively connect two separate resistor circuits in series, or to connect the two circuits to the electric power supply by using the flat terminal element 7 provided on sheet element 6c.
If so required, sheet element 6c may be simplified for solely connecting two resistor circuits in series, without the provision of any external connections.
It is thus obvious that the described method may be employed by one skilled in the art for obtaining the greatest variety of of connections between any number of initially separate electric circuits in series, in parallel, and with electric power supply terminals at any desired location.
The described method may thus be accomplished by the operations of a) connecting and/or interconnecting electric circuits at selected locations thereof by means of a single conductive sheet member secured to the insulating support, and b), dividing the conductive sheet member into several separate sheet elements adapted to be selectively connected to one or more of the electric circuits, with the possibility of performing these operations in a fully automatized process without any manual intervention.
As a matter of fact, all of the operations described in connection with the four steps of the process as well as the ancillary operations (preparation of the conductive sheet member, drilling the apertures in the insulating support and so on) can be carried out by fully automatized programmable machinery. The construction of such machinery and of the asssociated tools and actuators as well as the composition of the required operating programmes are familiar to one skilled in the art and need therefore not be explained.
Those skilled in the art will in particular be capable of optimizing the sequence of the various steps with a view to the timing of their execution, or with a view to regrouping the operations into a reduced number of steps each including several elementary operations.

Claims

A method for making connections between electric circuits disposed on an insulating support (3) including the steps of applying a plurality of terminals (7) to said insulating support (3), said step of applying said plurality of terminals (7) is carried out by mounting at least one conductive member (5) on said insulating support (1) by inserting projections extending therefrom into apertures (4) formed in said insulating support (3), and mechanically and electrically connecting terminal ends of said electric circuits (2) to said plurality of terminals (7),
characterised in that
said conductive member being a sheet member being formed with a plurality of outwards projecting tongues (6),

and that said sheet member is positioned so that said tongues (6) coincide with respective terminal ends (2a) of said electric circuits (2), said tongues (6) being bent 180° upon themselves to form two legs for said terminal ends (2a) to be received therebetween,

and that said sheet member (5) is divided into several separate sheet elements (6a, 6b, 6c) by the execution of multiple cuts at selected locations and the removal of sheet sections extending between adjacent cuts, and

that said projections inserted into said apertures (4) and projecting from said insulating support are bent over the edges of said apertures in a locking fit.
A method according to claim 1, characterised in that at least one pair of separate sheet elements (6a, 6b) is devised to connect the terminal ends (2a) of at least one of said electric circuits (2), each of said sheet elements being provided with at least one flat terminal element (7).
A method according to any of the preceding claims, characterised in that at least one separate sheet element (6c) is connected to at least one pair of terminal ends (2a) of respective different electric circuit elements (2), and may be provided with one or several flat terminal elements (7).
A method according to any of the preceding claims, characterised in that it is executed by a fully automised plant.
An electric circuit (2) disposed on an insulating support (3) and connected to flat power supply terminals (7), said terminals (7) extending from a conductive member (5) which is mounted on said insulating support (3) by inserting projections extending therefrom into apertures (4) formed in said insulating support (3),
characterised by
said conductive member (5) being a sheet member being formed with a plurality of outwardly projecting tongues (6), and by said sheet member being positioned so that tongues (6) coincide with respective terminal ends (2a) of said electric circuits (2), said tongues (6) being bent 180° upon themselves to form two legs for said terminal ends (2a) to be received therebetween, and that said sheet member (5) being divided into several separate sheet elements (6a, 6b, 6c) after being mounted on said insulating support (3) by the execution of multiple cuts at selected locations and that the sheet sections extending between adjacent cuts are removed and that said projections inserted into said apertures (4) and projecting from said insulating support are bent over the edges of said apertures in a locking fit.