Electrical assembly having multiple slidable elements
FIELD OF THE INVENTION 
     This invention relates to a multi-slider electrical assembly wherein a plurality of slidable electrical elements such as variable resistor devices and slidable switching devices are mounted on a single substrate structure. 
     BACKGROUND OF THE INVENTION 
     Multi-slider electrical assemblies including slidable variable resistor or other electrical devices are known and used in graphic equalizers. Such a multi-slider variable electrical assembly generally comprises a substrate having conductive patterns as resistor, collector or other elements printed thereon, a cover mounted on the substrate to define the outer margin of the assembly, a guide block means interposed between the substrate and cover to define a plurality of parallel slits, a plurality of carriers reciprocally received in the slits of the guide block means, and a plurality of sliders each secured to the bottom surface of the carrier to slide on the conductive patterns when the carrier is moved. Each carrier has a lever extending upward through one of elongated grooves in the cover to provide an external knob. When the lever is moved along the elongated groove, the associated slider moves on the conductive patterns to change its position and hence vary the electrical output which is taken from a lead terminal soldered to a circuit pattern on the bottom surface of the substrate. 
     In the prior art multi-slider assembly, since the substrate is a printed board made of a heat-resistant material to accept a temperature of more than 200° C. upon printing conductive patterns such as resistor and collector elements on its upper surface, a significantly expensive material must be used as the substrate structure. Additionally, since the conductive patterns on the upper surface are led to conductive patterns on the lower surface of the substrate and are soldered there to lead terminals, the troublesome soldering also causes a further increase of the manufacturing cost of the assembly. 
     OBJECT OF THE INVENTION 
     It is therefore an object of the invention to provide a multi-slider electrical assembly using an inexpensive substrate material and facilitating electrical connection between the conductive patterns and lead terminals to reduce the manufacturing cost of the assembly. 
     SUMMARY OF THE INVENTION 
     In the most preferred form of the invention, the substrate structure is made of a first insulative film having printed resistor, collector and other elements in the form of printed conductive patterns, and a second insulative film having lead circuit patterns so as to connect connection lands of the conductive patterns on the first insulative film to connection lands of lead circuit patterns on the second insulative film by a heat-sealing means. 
     The use of inexpensive two insulative films in place of a prior art expensive printed board enables to provide the conductive patterns for resistor, collector or other elements on the first insulative film and provide the lead circuit patterns on the second insulative film so that they are electrically connected via connection lands associated to the conductive patterns and lead circuit patterns respectively. Therefore, the second insulative film keeps off the heat of 200° C. or more applied to the first insulative film for printing the conductive patterns, and may be made from any inexpensive insulative material to decrease the manufacturing cost of the substrate structure. 
     The heat-sealing connection between the first and second insulative film provides a reliable electrical connection and facilitates the connection process by omitting the soldering. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     FIGS. 1 through 3 illustrate a multi-slider electrical assembly (variable resistor assembly) embodying the invention in which: 
     FIG. 1 is a fragmentary cross-sectional view; 
     FIG. 2 is an exploded perspective view; and 
     FIG. 3 is a cross-sectional view to show electrical connection between first and second insulative films. 
     FIG. 4 is a cross-sectional view showing a further electrical connection between the first and second insulative films. 
    
    
     DETAILED DESCRIPTION 
     The invention is hereinbelow described in detail, referring to preferred embodiments illustrated in the drawings. 
     In FIGS. 1 and 2, reference numeral 1 designates a support plate made of iron, aluminum or other metal and having a number of bores 1a. Reference numeral 2a is a first insulative film made from polyimide or other heatresistant insulative material and provided with printed conductive patterns 20 such as resistor and collector elements on its upper surface and circuit patterns (not shown) on its lower surface which are continuous from the upper conductive patterns 20 via through holes (not shown). Reference numeral 21 in FIG. 2 designates connection lands at end portions of the circuit patterns on the lower surface of the first insulative film 2a and not overlapping the uper conductive patterns 20. Still referring to FIG. 2, reference numeral 22 denotes engage holes passing through the first insulative film 2a. Reference numeral 2b designates a second insulative film made from PET or other material and having on its upper surface lead circuit patterns 23 which respectively terminate at connection lands 24 at positions corresponding to connection lands 21 of the first insulative film 2a. The entire upper surface of the second insulative film 2b except the connection lands 24 is overcoated by thermoplastic resin 25 shown in FIG. 3. In FIG. 2, reference numeral 26 denotes engage holes. 
     As shown in FIG. 3, both insulative films 2a and 2b are mounted together, confronting their respective connection lands 21 and 24. Heat-sealing members 27 made from a thermoplastic resin including a mixture of conductive particles are interposed between respective opposed pairs of connection lands 21-24, and heat is applied to the films to thermally adhere the connection lands 21-24 by the heat-sealing members 27 and the other opposed surfaces of the films by the thermoplastic resin 25. 
     The assembly further includes a guide block means 3, some carriers 4, sliders 5, plate springs 6, spacers 7, and a cover 8. As best shown in FIG. 2, the guide block means made from a plastic resin includes two first blocks 4&#39; each having a step at one side thereof and some second blocks 3&#34; each having steps at both sides thereof. The first and second blocks 3&#39; and 3&#34; each have some pins 3a and 3b projecting from the upper and lower surfaces thereof. The first blocks 3&#39; are located at opposite ends on the first insulative film 2a so that their steps are opposed to each other. The second blocks 3&#34; are aligned in parallel between the first blocks 3&#39; at a predetermined interval to define slits therebetween. The downward projecting pins 3b of the first and second blocks 3&#39; and 3&#34; passing through the aligned holes 22 and 26 of the united first and second insulative films 2a and 2b are inserted and hot-welded in the bores 1a of the support plate 1 to unite the films 2a-2b and blocks 3&#39;-3&#34;. 
     Each carrier 4 includes a metal lever 4a and a slider carrier which are united together by inserting the slider carrier 4b in the lever 4a. The slider 5 is secured to the bottom surface of the slider carrier 4b as shown in FIG. 1 by hot-welding or other fixing method. Each carrier 4 is accepted in the slit between adjacent first and second blocks 3&#39;-3&#34;, with both ends of the slider carrier 4b being slidably accepted on opposed steps of the blocks. 
     The cover 8 is an iron, aluminum, stainless steel or other metal plate. The cover 8 has a plurality of transversal parallel elongated grooves 8a at a given interval corresponding to the number of the slits defined by the blocks 3&#39;-3&#34;, and a number of through holes 8b at both sides of and between the elongated grooves 8a. 
     After the plate springs 6 and spacers 7 are mounted around the lever 4a of the carrier 4, the case 8 is mounted on the guide block means 3 so that the lever 4a passes through the elongated groove 8a, and the upward pins 3a of the blocks 3&#39;-3&#34; engage the through holes 8b. The pins 3a are subsequently hot-welded in the through holes 8b to conjoin the blocks 3&#39;-3&#34; with the cover 8. 
     With this arrangement, when the lever 4a of the carrier 4 is moved in and along the elongated groove 8a, the slider 5 moves on the resistor and collector elements in the form of conductive patterns on the first insulative film 2a to provide an amount of resistance determined by the position of the slider 5 and taken from the lead circuit pattern 23 of the second insulative film 2b. 
     As described, the invention replaces the prior art expensive printed board by inexpensive first and second insulative films 2a and 2b, the first film 2a having the resistor, collector or other printed conductive patterns and the second film 2b having the lead circuit patterns 23, so that the second insulative film 2b does not receive heat of 200° C. or more upon printing the conductive patterns 20 on the first insulative film 2a. Therefore, any inexpensive insulative material may be used as the second insulative film 2b to significantly decrease the manufacturing cost of the substrate structure. 
     Beside this, electrical connection between the connection lands 21-24 of the first and second insulative films 2a-2b is readily and reliably established by heat-sealing them via the heat-sealing members 27. Therefore, soldering of the patterns is omitted to facilitate the manufacturing process of the assembly. 
     The thermoplastic resin 25 provided on the second insulative film 2b conjoins the remaining opposed surfaces of the insulative films 2a-2b other than their lands 21-24 to provide a more strong fixture of the insulative films. 
     The connection lands 21 of the first insulative film 2a are located at positions on the lower surface not overlapping the conductive patterns 20 to protect the patterns 20 against crushing or other damages upon heat-sealing the connection lands 21-24 by the heat-sealing members 27. 
     FIG. 4 is a cross-sectional view of a further embodiment of the invention where identical members to those of FIG. 3 are designated by the same reference numerals. In this arrangement, an elastic member such as a foamed sheet is mounted immediately under the blocks 3&#39;-3&#34;, with the pins 3a-3b passing therethrough, to establish a resilient, compressive and direct contact between the connection lands 21-24 of the first and second insulative films 2a-2b. 
     As described, the use of two separate insulative films in place of a prior art expensive printed board not only contributes to a reduction in the manufacturing cost of the substrate structure but also facilitates the manufacturing process by omitting the soldering between the conductive patterns and external circuit elements. 
     The use of the elastic member 28 interposed between the guide block means 3 and first insulative film 2a provides a reliable electrical contact between the connection lands 21-24 by a simple compressive arrangement. 
     When the thermoplastic resin 25 is overcoated on the second insulative film 2b except the connection lands 24 to thermally adhere the opposed surfaces of the first and second insulative films, a more reliable contact is established between the connection lands 21-24.