Improvements in a straight-line potentiometer

Abstract: An improved straight-line potentiometer with a casing (1) having a longitudinal opening (2) along which slides a carrier (3) having a slider (4) providing electrical contact between an electroconductive slideway (5) and an electroresistive slideway (6), said slideways (5, 6,) being longitudinally arranged on opposite sides of said opening (2). The carrier (3) is further comprised of an operating stem (7) and two resilient lugs (10), arranged so as to form a fork, extending through said opening (2) and the lugs (10) ending in toes (11) which engage the inner edges of said opening (2). Resilient grips (13, 13a) are situated at opposite ends of a longitudinal line of said carrier (3, 3a), perpendicular to the transverse axis formed by said toes (11) and engaging lateral sectors of said slider (4, 4a) in a riding arrangement, and a centrally disposed offset portion (14) of said slider (4, 4a) is introduced between the lugs (10).

Description: Field of the Invention The object of this invention concerns some improvements in a straight-line potentiometer, in particular of the miniature type and of those employed in electronic units, said improvements providing more reliability, an easy assembly and a lower manufacturing cost. Prior Art Those straight-line potentiometers are in fact conventional which do basically comprise a casing with a longitudinal opening at each of whose sides there are one or more electric slideways which are parallel to each other and electroconductive and/or electroresistive, there being generally an electroconductive one for each electroresistive one, as well as a carrier with an operating stem or appendage which is operable to be shifted in a straight-line along said opening, said carrier carrying one or more electroconductive members or sliders forming electrical jumpers between several points of said slideways. We can mention, Patents GB-a-1305955, DE-a-1952319 and DE-A-2521789. FR-A-2 282 150 discloses an improved straight-line potentiometer in which the flexible central plate has at one of its extremes two retaining hooks engaged within the slider. Furthermore, in a known solution of the prior art the engagement of said slider carrier with the potentiometer casing is carried out by means of two U-shaped or fork-shaped resilient lugs of said carrier, each of said lugs ending in a toe, said toes approaching when being inserted through said longitudinal opening and again spacing themselves apart once having passed the inner surface of the latter, said toes being thus retained at respective inner edges of said longitudinal opening. The electroconductive member forming the slider is attached to said fork-shaped lugs by means of riveting on flat fastening areas at both sides of the lugs, this operation having to be carried out by means of precision robotics due to the reduced dimensions involved. This increases in short the cost of the product if a correct manufacture of the potentiometer has to be guaranteed. Nevertheless, in said straight-line potentiometer of the prior art it happens that if due to any intervention in the pertinent circuit or during said riveting of the slider said lugs approach or are deformed by heating their toes can get at least in part into the longitudinal opening thus being trapped inside it and hence preventing the operation of the potentiometer itself. And if an attempt is made to unblock said carrier by acting on it in order to correct such an anomaly, said slider can be then damaged due to its frail build on account of its reduced dimensions. The gripping provided by said lugs, to a portion of which the slider is fastened by riveting, is not in any case effective or secure, and imposes in general onerous process costs if a proper completion of the potentiometer is called for. Brief Description of the Invention The object of the invention consists in obviating the above-mentioned drawbacks by means of a straight-line potentiometer defined by the features of claim 1. Its improvements essentially are based in providing the slider with a portion, for example by way of an offset portion, which in the assembly process is inserted between the fork-shaped lugs of the carrier thereby totally preventing said lugs from joining and passing again through the opening or getting trapped in it. Said slider is as well provided with tabs which are oriented in opposite directions and are inserted between respective pairs of resilient grips of the carrier, the action of said grips being perpendicular to that of the toes or fork-shaped lugs whereas at the same time said grips exert their gripping action on corresponding edges of said slider thereby firmly retaining it with no need to carry out any riveting whatsoever, with the consequent cost saving and simplicity of the operation; all this as will be explained hereinafter and as claimed in the appended claims. In order to facilitate the following explanation this description is accompanied by a sheet of drawings showing by way of a merely illustrative and nonlimiting example an embodiment of the object of the invention. Short description of the drawings In said drawings: Figure 1 is a plan-view of the inside of the straight-line potentiometer of the invention showing its casing in a cutaway view; Figure 1a is a view similar to the previous one illustrating an alternative embodiment of the carrier and slider; Figure 2 is a longitudinal elevation sectioned along section line II-II in the previous Fig. 1 showing the gripping of the slider by its carrier; and Figure 3 corresponds to a 90° rabatment of Fig. 2 showing the potentiometer casing in a sectional and partly cutaway view, as well as the attachment to it of the slider carrier by way of a slide. Detailed Description of a Preferred Embodiment According to these Figures, the straight-line potentiometer being the object of the improvements as per the invention is essentially composed of a casing (1) with a longitudinal opening (2) along which can slide by way of a slide carrier (3) carrying the metallic slider (4) which establishes electric contact between both slideways, of which normally one (5) is electroconductive and the other one (6) is electroressitive, both slideways being parallel to one another and being each longitudinally arranged at its respective side of said opening. Carrier (3) is on its side composed of a piece having an operating outer stem (7) and an enlargement (8) which is apt to slide on longitudinal guides (9) provided by way of a step flanking said opening (2), two resilient and sensibly wide lugs (10) extending from said enlargement (8) by way of a fork, in such a way that said lugs are inserted in said opening (2) and end each in its corresponding toe (11) which projects from its central part and from its outer surface, said toes being thus retained on the inner edges of said longitudinal opening (2) in such a way that carrier (3) can slide along said longitudinal opening. On the other hand, electrical jumper element or slider (4) is when mounted applied against the inner surface of carrier (3) and has two arcuate portions or arms (12) which are resilient and at their middle end part have respective pairs of inflexions (12a) which are tangent to the corresponding slideways (5) and (6). In the present invention the fact is to be pointed out that at each of both end edges or corners of each lug (10) a resilient grip (13) is formed in such a way that both said grips of each lug are flanking the respective central toe and are facing each other. As for slider (4) the fact is equally to be pointed out that it has at the centre a U-shaped offset portion (14) whereas at each of the opposite end parts of its longitudinal axis and transversally to its arms (12) there is a tab (15) of a preferentially rectangular shape. With this arrangement, when mounting the slider said offset portion (14) is inserted between lugs (10) of the fork-shaped portion of carrier (3) thereby locking them and preventing them from closing and being thus in a position to pass again through said longitudinal opening (2). Said U-shaped offset portion (14) provides besides a resilience in the longitudinal direction thus facilitating the insertion of the slider underneath the fastening grips (13), and its ulterior recovery eliminates all clearances. As for tabs (15) of slider (4), they are inserted between respective pairs of grips (13), the latter being at the same time applied in a riding arrangement on areas adjacent to said tabs (15) of said slider (4) and thus working in a direction perpendicular to that of toes (11) thus firmly attaching slider (4) to lugs (10) of carrier (3). This arrangement allows as well that the arms or origins of the arcuate portions (12) of slider (4) are in a position to pass between grips (13) and toes (11), which are conveniently spaced apart. Figure 1a shows an alternative embodiment of carrier (3a) wherein said lugs include resilient grips (13a) which are facing each other and situated at opposite ends of a longitudinal line of said carrier (3a) which is perpendicular to the transversal axis containing toes (11) of said lugs (10), said grips (13a) being provided to grip slider (4a) (which is in this case devoid of tabs (15)) by gripping in a riding arrangement lateral sectors of the latter.

Claims: A straight-line potentiometer of the type in which a casing (1) having a longitudinal opening (2) along which slides a carrier (3) having an electroconductive slider (4) which provides electrical contact between at least an electroconductive slideway (5) and an electroresistive slideway (6), said slideways (5, 6,) are longitudinally arranged on opposite sides of said longitudinal opening (2) and run parallel to said longitudinal opening (2), said carrier (3) is further comprised of an operating stem (7) and two resilient lugs (10), arranged so as to form a fork, extending through said longitudinal opening (2), the ends of said lugs (10) are further provided with toes (11) which engage the inner edges of said longitudinal opening (2), and allows said carrier and slider (3) to slide along said longitudinal opening (2), characterized in that it comprises: a plurality of resilient grips (13, 13a) situated at opposite ends of a longitudinal line of said carrier (3, 3a), perpendicular to the transverse axis formed by said toes (11) and engaging lateral sectors of said slider (4, 4a) in a riding arrangement; and an improved slider (4, 4a) provided with a centrally disposed offset portion (14) which is inserted between said lugs (10) of said carrier (3, 3a). A potentiometer as per claim 1, characterized in that the offset portion (14) of said improved slider is recessed. A potentiometer as per claim 1, characterized in that said plurality of resilient grips (13) is comprised of a first pair of said resilient grips and a second pair of said resilient grips and the grips of said first pair of grips are facing the grips of said second pair of grips and said grips (13) being coplanar with said toes (11) and said grips are disposed at opposite ends of a longitudinal line of said carrier (3) which is perpendicular to the transverse axis formed by said lugs (10). A potentiometer as per claim 3, characterized in that said slider (4) has a tab (15) projecting from each of two longitudinally opposite points and said slider (4) has a plurality of resilient arms (12) extending from said slider (4) and resting on said slideways (5, 6) along an axis perpendicular to the transverse axis formed by said tabs, where said tabs (15) are inserted between and engage each pair of said grips (13) so as to fasten said slider (4) to said carrier (3). A potentiometer as per claim 3, characterized in that : said lugs (10) are markedly wide, said toes (11) starting from a central part thereof and projecting towards the exterior; and said resilient grips (13) are located next to the end corners of said lugs (10) and are thus situated on both sides of said toes (11) and said grips (13) face each other. A potentiometer as per claim 5, characterized in that the distance between said grips (13) and said toes (11) is such that it allows said resilient arms (12) to slide freely therebetween. A potentiometer as per claim 1, characterized in that said stem (7) has an enlargement (8) from which extends said resilient lugs (10) and which slides along a pair longitudinal guides (9) provided by steps formed along the edges of said longitudinal opening (2).

Inventors: CASTELLANO ALDAVE JESUS CARLOS, CASTELLANO ALDAVE, JESUS CARLOS
Applicants: NAVARRA COMPONENTES ELECTRO, NAVARRA DE COMPONENTES ELECTRONICOS, S.A.
Application year: 1996
Main classification: H01C10
IPC codes: H01C10