Miniaturized power relay for printed circuits

Abstract: The miniaturized power relay for printed circuits comprises an electromagnetic circuit (2) complete with coil (39), a contact-holder block (3) provided with an actuator (25) and a protection and sealing covering (4); the magnetic circuit has exclusively a fixed supporting element (5) and a movable keeper element (6) the respective polar expansions whereof (7, 8) are conveniently shaped so as to reduce dimensions and are accommodated inside the coil to use all of the magnetic flux which is generated by the coil itself.

Description: The present invention relates to a miniaturized power relay for printed circuits. As is known, the extremely widespread use of relays in many fields of electrical technology, telecommunications, electronics and in particular of automation is due to the versatility of the numerous types provided; in particular, the trend of manufacturers of electronic devices which currently use said miniaturized relays is to reduce their dimensions and make them as compact as possible. In particular, the trend of manufacturers of electronic devices is most of all to achieve, by reducing the size of the relays, a reduction in the gauge of the electronic boards on which the relays are mounted. In view of the above, relay manufacturers are therefore induced to manufacture relays which have smaller dimensions, especially in terms of height, and are increasingly sensitive, i.e. have a lower power consumption so as to also reduce the dimensions of the power supply transformers. A magnetic circuit of current miniaturized relays currently has an electromagnet which is excited by an electric current which flows through its coil so as to attract a movable keeper against the polar face or polar expansion. The movement of the keeper is conveniently used to provide the required movements on the contacts. The return of the movable keeper to the idle position, after the excitation current has ceased, is provided by means of a spring and generally by means of the elastic contact-holder laminas themselves of the relays. The number, the arrangement of the contacts and the sequence of the movements naturally vary according to the purposes to which said relay is assigned. Current power relays, depending on the execution of their structure, have their polar expansions arranged externally to the coil and/or shaped so as to generate magnetic losses in the circuit with a partial use of the flux produced by the coils and consequently with a low magnetic efficiency. Another disadvantage to which current miniaturized relays are often subject is related to the difficulty in assembling the contact-holder block and the electromagnetic circuit-holder block and to their adjustment. Not least, the need to insulate the contacts from the magnetic circuits by means of surface distances in excess of 8 mm and a dielectric strength in excess of 4 KV, as required by the currently applicable norms, necessarily entails the use of insulating plates which sometimes cause an increase in the external dimensions of the relay with all the consequences which derive from this. EP-A-310 091 discloses a miniaturized power relay as defined in the pre-characterizing part of claim 1. Said miniaturized power relay does not have a keeper element provided with a recess coinciding with the oscillation axis of said keeper element. An important object of the present invention is to provide a miniaturized power relay for printed circuits which has extremely modest coil absorption and dimensions. A further object of the present invention is to provide a miniaturized relay which despite having reduced dimensions has a dielectric strength in excess of 4 KV between the magnetic circuit, complete with coils, and the contact block, with a surface distance of at least 8 mm between the metallic parts thereof. Not least object of the invention is to provide a miniaturized relay which allows an extremely simple and automated assembly of the magnetic circuit block with the contact block, together with the fact of having an extremely simple adjustment process with a smaller number of operations than the adjustment of conventional relays. This aim and these objects are achieved by a miniaturized power relay for printed circuits as defined in the characterizing clause of claim 1. The details of the invention will become apparent from the description of a preferred embodiment of the miniaturized power relay for printed circuits according to the invention, illustrated in the accompanying drawings, wherein: figure 1 is a transverse sectional lateral elevation view of the relay; figure 2 is a view taken along the sectional line II-II of figure 1; figure 3 is a view taken along the sectional line III-III of figure 1; figure 4 is a view taken along the sectional line IV-IV of figure 1; and figure 5 is a schematic view of the steps of the assembly of the magnetic circuit-holder block with the contact-holder block and with a protection and sealing covering; figures 6 and 7 illustrate a variated constructive embodiment of the relay according to the invention. respectively an alternating-current relay and a bistable permanent-magnet relay. With reference to the above described figures, the miniaturized relay according to the invention, generally indicated by the reference numeral 1, comprises an electromagnetic circuit complete with coil 39, a contact-holder block 3 provided with an actuator 25, and a protection and sealing covering 4. The magnetic circuit with low magnetic loss is made of just two pieces of pure iron: one piece is fixed and defined by a fixed supporting element 5, and the other one is movable and is defined by a movable keeper element 6. The fixed supporting element 5 and the movable keeper element 6 have their respective polar expansions 7 and 8 accommodated inside a coil 39 so as to use all of the flux produced by said coil. Each of the polar expansions 7 and 8 furthermore has an inclined surface 9 and 10; said surfaces are dimensioned and mutually matched so as to maximally contain their bulk and facilitate the best magnetic efficiency of the circuit. Furthermore, as mentioned, in order to allow the use of all of the flux generated by the coil, the attraction gap 11 between said polar expansions is internal to the coil 39. More in particular, as can be seen in figure 1, the keeper element 6 and the supporting element 5 substantially have a U-shaped configuration which is defined by a first wing and by a second wing, respectively indicated by 12 and 13, which are connected by a crosspiece 14. Advantageously, as mentioned, the supporting element and the keeper element are furthermore entirely made of pure iron, so that the magnetic circuit is composed of only two parts instead of three as normally occurs. The first wing 12 of the supporting element 5 is larger than its second wing 13 and is external to the coil 39, whereas the first wing 12 of the keeper element 6 is smaller than the second wing 13 thereof and is external to the coil 39. In particular, the second wings 13 of the supporting element and of the keeper element are inserted from opposite sides of a through hole 15 in the coil 39. The through hole 15 conveniently has a rectangular cross-sectional configuration. The supporting element 5 is rigidly associated with the coil by virtue of the exact coupling of its internal and external wings 13 and 12 with the plastic spool 40 of the coil. The keeper element is furthermore associated, so as to be able to oscillate, with the supporting element by means of an elastic element 17 which has one of its ends rigidly associated with the supporting element and its opposite end engaged in a recess 18 defined on the end of the keeper element. The recess 18 furthermore coincides with the oscillation axis or fulcrum of the keeper element. The position of the fulcrum of the keeper element, exemplified in figure 1 on the back of the supporting element, can also be arranged, for example, according to the requirements, on the end of the supporting element or on the back or inside it; in this case the length of the wing 12 of the keeper element is practically zero. In the case being considered, the particular position of the fulcrum of the keeper element is approximately at one third of the length of the first wing of the supporting element so as to obtain a perfect balancing of the keeper element with respect to the oscillation axis. Advantageously, the particular configuration of the polar expansions furthermore causes the sum of the area of the co-planar sections of the polar expansions of the supporting element and of the keeper element to be equal along the entire length of said polar expansions so as to provide minimal dimensions with constant induction in the iron. In order to comply with the currently applicable laws, the relay has an insulation plate 19 made of thermoplastic material and suitable for providing a dielectric strength of 4 KV between the contacts and the magnetic circuit with a surface distance thereof in excess of 8 mm. The insulation plate 19 is associated with a base 20 which is made of insulating material, more precisely also made of thermoplastic material, on which the fixed contact-holders 21 and a movable contact-holder 22 are mounted; an elastic lamina 23 is rigidly coupled to said movable contact-holder 22 with a first end by means of welding or riveting and supports, in a substantially terminal position, a contact 24 which is movable between the fixed contacts 21. Obviously the contact-holder block 3 described above relates for example to a relay with a single switching contact, but as is obvious to the technician in the field the same type of construction is also valid for two switching contacts mounted side by side on the contact-holder bases and actuated by the same actuator 25. The relay furthermore comprises actuation means for converting the rotary motion of the second wing 13 of the keeper element 6 into a translatory motion of the actuator 25 of the elastic lamina 23 for the movement of the movable contact 24 between the fixed contacts. More precisely, the actuation means comprise a guiding channel 26 which has, in cross section, a frustum-like configuration and is associated with the base 20. The actuator element 25 is slidable inside the guiding channel 26 and is connected in an articulated manner to the second wing 13 of the keeper element which is guided, on the narrowest side of the channel 26, adjacent to the end of the laminas 23. The coupling between the end of the second wing of the keeper element and the actuator element occurs by virtue of automatic coupling means and more precisely by means of a slide-like element 27 which is present on the upper part of the actuator element and defines therewith a rotatable retention seat 28. Two mutually opposite coaxial expansions 29 insert snap-together inside the seal 28 and extend laterally from the ends of the second wing of the keeper element. This technical solution advantageously allows the actuator element to perform a rectilinear translatory motion inside the guiding channel with virtually no friction. The above furthermore allows, in an extremely simple manner, to associate the circuit-holder block with the contact holder block, as shown in figure 5, with a simple longitudinal translatory motion so as to couple the two blocks by interpenetration, using appropriate snap-together elements which are shown in figure 3 and are constituted by the wings 16 defined on the supporting element and by the corresponding grooves defined on the insulation plate so as to ensure the stable relative position of the two blocks in the course of time. Finally, as again shown in figure 5, the two blocks are covered by a protection covering 4 and then sealed by means of a considerable amount of sealing resin. Finally, it should be noted that the structure of the relay according to the invention allows a further very important advantage, i.e. it allows a simplified adjustment of the stroke limit of the elastic lamina 23. Essentially, the adjustment is performed simply by carrying out a possible deformation of the end of the second wing 13 of the keeper element 6 so as to obtain the pre-required force of the movable contact on the fixed one. The operation of the miniaturized power relay according to the invention is evident from what is described and illustrated; in particular, when the magnetic circuit-holder block is connected to the contact-holder block, the end of the second wing 13 of the keeper element 6 engages snap-together and in an articulated manner with the actuation element 25, which by moving without friction, as mentioned, within the guiding channel 26, acts on the ends of the elastic lamina 23. When current flows through the coil 39, the keeper element 6 is attracted by the supporting element 5, and by rotating about the fulcrum axis 18 it performs, at the end of the second wing 13, an active stroke, transferring the movement, by means of the actuator element 25, to the end of the elastic lamina 23, switching the contacts. In practice it has been observed that the miniaturized power relay according to the invention is particularly advantageous in that it has extremely reduced dimensions especially in terms of height and it is extremely sensitive and therefore has a low consumption so as to allow to reduce the dimensions of the power supply transformers. Since it has appropriately shaped polar expansions arranged inside the coil, the magnetic circuit made of only two parts (a fixed supporting element and a movable keeper element), facilitates the best magnetic efficiency of the circuit since said circuit has less magnetic losses and all of the flux produced by the coil is furthermore used. Finally, the relay complies with the currently applicable laws on the subject, since the insulation which is generated between the magnetic circuit and the contact block has a dielectric strength in excess of 4 KV with a surface distance of 8 mm between the metallic parts thereof, though extremely reduced external dimensions are maintained. Figures 6 and 7 furthermore illustrate two relays according to the invention, the first one for alternating current and the second one of the bistable type with a permanent magnet, wherein the numeral 40 (figure 6) indicates a short-circuit turn and, in figure 7, 50 indicates a permanent magnet and 51 indicates the gap. In practice, the materials employed, as well as the dimensions, may be any according to the requirements and to the state of the art. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: Miniaturized power relay for printed circuits, comprising: an electromagnetic circuit (2) complete with coil (39), a contact-holder block (3) provided with an actuator (25), a protection and sealing covering (4), said magnetic circuit comprising a fixed supporting element (5) and a moving keeper element (6) the respective polar expansions thereof (7, 8) are accommodated internally to said coil to use the entire magnetic flux generated by said coil, said keeper element and said supporting element substantially having a U-shaped configuration defined by a first wing (12) and by a second wing (13) which are connected by a crosspiece (14), characterized in that said first wing (12) of the keeper element is provided with a recess (18) coinciding with the oscillation axis of said keeper element. Miniaturized power relay for printed circuits according to claim 1, characterized in that said first wing of said supporting element is larger than said second wing is external to said coil, and in that said first wing of said keeper element is smaller than said second wing and is external to said coil. Miniaturized power relay for printed circuits according to claim 1, characterized in that said second wings respectively of said supporting element and of said keeper element are inserted from opposite sides of a through hole (15) of said coil. Miniaturized power relay for printed circuits according to claim 1, characterized in that the sum of the area of the co-planar sections of said polar expansion of said supporting element and of said keeper element is equal along the entire length thereof so as to provide constant induction. Miniaturized power relay for printed circuits according to claim 1, characterized in that said first wing (12) of the said supporting element is provided with an elastic element (17), said second wing (13) of the keeper element being provided with a fulcrum lying on the pivot axis upon oscillating of said keeper element and connected with said elastic element, said fulcrum lying a location approximately one-third of the lenght of said second pole wing of said keeper element to provide substantially perfect balance thereof. Miniaturized power relay for printed circuits according to claim 1, characterized in that said contact-holder block comprises a base (20) made of insulating material which has fixed contact-holders (21) and a movable contact-holder (22) with which an elastic lamina (23) is rigidly connected with a first end, said elastic lamina supporting a contact (24) which is movable between said fixed contacts, said base having an insulation plate (19) to insulate said fixed and movable contacts from said magnetic circuit. Miniaturized power relay for printed circuits according to one or more of the preceding claims, characterized in that it comprises actuation means (26) for converting the rotary motion of said second wing of said keeper element into a translatory motion of said actuator of said elastic lamina. Miniaturized power relay for printed circuits according to claim 7, characterized in that said actuation means comprise a guiding channel (26) which is associated with said base and inside which said actuator element of said elastic lamina is slidable, said actuator element being connected to said second wing of said keeper element. Miniaturized power relay for printed circuits according to one or more of the preceding claims, characterized in that said second wing (13) of the keeper element (6) is operatively connected to said lamina to enable adjusting of a force of said movable contact against one of said fixed contacts by deformation of said second wing (13). Miniaturized power relay for printed circuits according to one or more of the preceding claims, characterized in that it comprises a first supporting block for said magnetic circuit, said first block being longitudinally associable with a second supporting block which comprises said base, said actuator element, said insulation plade and said guiding channel, means (27) being furthermore provided for the automatic coupling between said second wing of said keeper element and said actuator element. Miniaturized power relay for printed circuits according to one or more of the preceding claims, characterized in that said coupling means comprise a slide-like element (27) which is rigidly associated with said actuator element and defines therewith a seat (28) for the rotatable retention of two coaxial and opposite expansions (29) which extend laterally from the end of said second wing of said keeper element.

Inventors: ALBERTONI MARTINO, ALBERTONI, MARTINO
Applicants: GAVAZZI CARLO ELECTROMATIC, CARLO GAVAZZI AG
Application year: 1990
Main classification: H01H50
IPC codes: H01H50, H01H51