Electrical contact having a self-cleaning contact piston

Abstract

An electrical contact device comprising: at least one metal contact part; a movable metal contact head comprising an end protrusion arranged to define an electrical contact point during the cooperation with an opposing electrically conductive element; guide means arranged to guide a movement of the movable metal contact head relative to the contact part along a longitudinal axis of the electrical contact device; and a compression spring pressing against the contact head on the side opposite the electrical contact point.

Description

[0001] Description

[0002] Self-cleaning piston electrical contact.

[0003] Declaration of priority

[0004] This application claims priority from application FR2402340 having a filing date of March 8, 2024, this application being incorporated by reference in its entirety.

[0005] Technical Field

[0006] The present description relates to electrical piston contacts having, on the one hand, the intrinsic capacity to carry out a self-cleaning movement of its point of contact with the opposite contact element during the entire compression stroke of its movable head induced by the movement of approaching the opposite contact surface and, on the other hand, having an improved characteristic of conduction of the electric current.

[0007] Previous Art

[0008] CN116093651 A describes a spring-loaded connector with position identification. JPH11307161 A describes a spring-loaded pin connector used in various electronic devices and for testing them. WO2023181906A1 describes a spring-loaded connector used in a part of various electronic devices that provides a detachable electrical connection.

[0009] Summary

[0010] Electrical piston contacts are traditionally used in railway couplings, more precisely in automatic coupling systems for railway rolling stock to establish the electrical connection between the circuits of the power car and those of the following wagon or between the electrical circuits of two consecutive wagons. In these couplings, several dozen of these electrical piston contacts are generally mounted side by side in a support, providing a multitude of contact points. These assemblies must withstand a large number of coupling and uncoupling maneuvers, as well as all the small variations in axial and lateral position linked to the respective movements of each coupled rolling element and to the internal mechanical clearances of the coupling device.

[0011] Electrical piston contacts are also used as contact keys to create "beds of nails" for test benches for assembled electronic cards or PCB A (Printed Circuit Board Assembly) in order to simultaneously establish a multitude of test point connections during product development or to measure their performance. They are also traditionally found under the name PO-GO for the production of connectors with spring-loaded point contacts.

[0012] The electrical piston contacts known to date have the main disadvantage that the electric current passes through the only point of contact established mechanically with the element facing it, making this passage of current susceptible to oxidation and fouling, without any transverse relative self-cleaning movement being achieved due to the fact that the axis of the piston contact is in the same direction as the axis of movement and that the trajectory of the point of contact is aligned with the axis of the piston, that is to say that at the moment of establishing the connection between the piston contact and the contact element facing it, no friction movement capable of eliminating by mechanical friction the impurities or oxides present on the contact surfaces appears in the plane perpendicular to the axis of movement of the contact.

[0013] Another sensitive aspect of the piston contacts known to date is the difficulty in maintaining the quality of the electrical connection between the moving head of the piston contact and the static part of the piston contact, the latter being connected to a pole of the electrical circuit. Several solutions can be adopted depending on the desired current capacity objective, here are the best known.

[0014] For piston contacts carrying only very low currents, no special provisions are adopted, the low current having the possibility of passing through the compression spring made of electrically conductive material which pushes back the movable contact head by resting on the fixed base of the piston contact. Part of the current also has the possibility of passing through one or two random mechanical contact points which appear in the guide between the metal body secured to the fixed base and the movable contact head, the metal body serving as a guide part for the contact head. Electrical continuity is ensured in all cases but the value of the electrical resistance is random, the number of contact points and the contact forces at these points not being controlled.An improvement in this aspect exists, however, since, as described by patent EP3627630, a particular construction arrangement promotes the tilting of the contact head within the limit of its guide volume and guarantees the presence of two contact points between the movable head and the guide body by producing a spring support face whose plane is inclined relative to the axis of movement of the head, which has the effect of forcing a lateral and tilting movement of the movable head. However, in this construction, the spring does not work in its best conditions since it is subjected to buckling, which causes friction and wear on its side. For piston contacts that must carry higher currents, from a few amperes to a few hundred amperes, two construction arrangements are known:

[0015] • the first arrangement consists of electrically connecting the moving head to the base via a flexible electrical shunt consisting of a braid of fine copper wires whose ends are connected to each of the two parts, this braid passing through the central space of the compression spring. An example of a known embodiment is given by document US2003 / 0049974. The shaping of this shunt can be more or less sophisticated, straight or twisted or helical, dictated by the objectives of resistance to wear and fatigue of the braid during the back-and-forth movements of the moving head. The production of this connection is often expensive due to the high price of the copper braid, the cost of its shaping and the delicacy of making the connections of its ends.This braid is often the element limiting the current capacity of the piston contact because the increase in its section results at the same time in a reduction in its flexibility and consequently, in its lifespan.

[0016] • the second known construction arrangement for having a high current capacity consists of making the contact head with an elastic part or of adding an elastic part or a contact clip which can be secured either to the movable contact head or to the contact body, the elastic zones establishing internal contact points to the piston contact, said contact points rubbing on surfaces belonging to the body of the piston contact or belonging to its fixed base when the elastic element is secured to the contact head, or these contact points rubbing on surfaces belonging to the contact head when the elastic element is secured to the contact body. An example of a known embodiment is given by document ES2356562. The number of internal contact points and the contact forces are in this case well controlled, guaranteeing a certain stability of the overall electrical resistance.However, this arrangement has the technical disadvantage of requiring a stronger, but also more bulky and more expensive, compression spring in order to compensate for the frictional forces at the internal contact points, so as to maintain the adequate contact force at the end of the contact head. Another technical limitation is the wear due to friction which appears at the internal contact points after a certain number of maneuvers, metallic wear particles being able to disturb and increase the electrical resistance of the contact points, which, in the long term, results in an increase in heating of the contact subjected to the passage of current.This arrangement also increases the cost of industrialization and manufacturing of the piston contact since, on the one hand, the manufacture of the attached elastic element generally requires having a press tool of the type of follow-up cutting-bending tool, which is particularly expensive, and on the other hand, the attached elastic element itself is an additional component which must generally be manufactured in an equally expensive elastic copper metal alloy. When it is the contact head with elastic parts of the same material which must be manufactured, the cost is also high due to the need to use elastic copper alloys with high conductivity.

[0017] One aim is to overcome these drawbacks by proposing a piston contact whose original design of the two main components, namely the contact head and the guide body or contact body, makes it possible, on the one hand, to generate a self-cleaning movement at the end contact point of the contact head, and on the other hand, to provide low electrical resistance and high wear resistance without requiring the implementation of costly arrangements such as using elastic materials to produce the contact head, elastic interface elements or electrical connection shunts.

[0018] One aspect of the present description relates to an electrical contact device comprising: at least one metallic contact body, a movable metallic contact head comprising an end protrusion arranged to define an electrical contact point when cooperating with an opposing electrically conductive element, guide means arranged to guide a movement of the movable metallic contact head relative to the contact body along a longitudinal axis of the electrical contact device, and a compression spring pressing against the contact head on the side opposite the electrical contact point, wherein the end protrusion and the guide means are arranged to impose a helical trajectory on the contact point during a relative movement of the contact head relative to the contact body.

[0019] Thus, the extremal protrusion may describe a movement, such as an arc of a circle, on the contact surface of the opposing electrically conductive element during a movement of the opposing electrically conductive element and the contact head relative to the contact body, thereby cleaning this contact surface as well as the contact point. This self-cleaning effect makes it possible to improve the reliability of an electrical power or electrical signal transmission. The helical movement may be considered as the combination of a translational movement with a rotational movement, as known to the person skilled in the art. The longitudinal axis of the electrical contact device may be defined as the axis in the largest dimension of the electrical contact device, which generally has an elongated shape.For example, the longitudinal axis may be an axis of symmetry of the contact body and / or the contact head, or be placed on a plane of symmetry of the electrical contact device.

[0020] Advantageously or alternatively, a second longitudinal axis, passing through the electrical contact point and parallel to the longitudinal axis, has a lateral, or radial, offset relative to the longitudinal axis. This makes it possible to simply ensure the self-cleaning arcuate movement on the contact surface and to control the amplitude of this movement.

[0021] Advantageously, one of the contact head and the contact body is of preferably straight cylindrical shape and / or circular cross-section and the other of the contact head and the contact body defines an axial guide volume of preferably straight cylindrical shape and / or circular cross-section. This allows easy manufacturing and optimal helical movement. For example, one of the contact head and the contact body is at least partially accommodated in the axial guide volume of the other of the contact head and the contact body. The axial guide volume may be aligned with the longitudinal axis.

[0022] Advantageously, the guide means comprise geometric shapes whose cross-sections projected in the plane perpendicular to the longitudinal axis fit into one another without interference and are twisted in a helical movement with the same winding direction and the same helix pitch along the longitudinal axis. Such guide means make it possible to ensure a high level of electrical and mechanical contact, making it possible to improve the electrical characteristics of the device and reduce wear. In addition, these geometric shapes exclude any through groove, in particular in the contact body, thus avoiding fouling of the electrical contact device.

[0023] Advantageously, the guidance means include:

[0024] • on one of the contact head and the contact body, at least one hollow guide surface of twisted shape around the longitudinal axis,

[0025] • on the other of the contact head and the contact body, at least one projection transverse to the longitudinal axis and adapted to be received in the hollow guide surface. Such guide means allow simple production and reliable and durable guidance of the contact head in or on the contact body. A hollow guide surface is preferably blind, i.e. non-opening. The transverse projection and the hollow guide surface each preferably comprise a contact surface or zone having the same curvature, so as to increase the contact surface.

[0026] Advantageously, the hollow guide surface results from the extension, along the axial guide volume and in a helical movement along the longitudinal axis, of a non-circular cross section perpendicular to the longitudinal axis including at least one hollow shape tangent to the projection of the circular section. Preferably, this guide surface defines grooves and in particular helical grooves, which can cover the entire guide surface, so as to increase the mechanical and electrical contact.

[0027] Advantageously, the at least one hollow guide surface is constituted by at least one helical groove extending along a guide face of the contact body or the contact head.

[0028] Preferably, the projection or projecting volume may have a cross section perpendicular to the longitudinal axis falling within the cross section perpendicular to the longitudinal axis, for example defined by the axial guide volume with its hollow volume(s) and having a profile capable of passing through the guide volume while being blocked in rotation by placing at least one side of the profile of the projecting element in opposition to a hollow side of the profile of the hollow guide surface.

[0029] Advantageously, the projecting volume is constituted by at least one helical rib of the same winding direction and the same helical pitch as the helical groove, the flank of the helical groove cooperating with the flank of the helical rib by establishing at least one contact generatrix passing through a contact point established at the contact between a cross-section of the contact body and a cross-section of the contact head. For example, the contact generatrix extends along a flank of the helical groove and helical rib and / or may extend over the entire length of the contact surface of the contact head or over a shorter length, for example at least 50%, at least 30%, or at least 10%.

[0030] Such a contact generator makes it possible to increase the internal contact between the contact head and the contact body and therefore to improve the transmission of electrical power. In addition, the contact generator makes it possible to limit the wear of the electrical contact device by distributing the mechanical forces over a larger surface area. Preferably, the guide means comprise two or a plurality of helical ribs and a plurality of helical grooves.

[0031] Preferably, the contact generator defines a continuous or segmented helical contact surface, further enhancing the above advantageous effects.

[0032] Advantageously, a point of application of the force of the compression spring on the contact head passes through an axis parallel to the longitudinal axis and laterally offset relative to the second longitudinal axis passing through the contact point located at the end of the contact head. This has the effect of producing a radial reaction contact force opposing the tilting of the contact head. This radial force increases the contact force at its location, locally promoting the flow of current.

[0033] Another aspect of the present description relates to an electrical contact device comprising: at least one metal contact body, a movable metal contact head comprising an end arranged to define an electrical contact point when cooperating with an opposing electrically conductive element, guide means arranged to guide a movement of the movable metal contact head relative to the contact body along a longitudinal axis of the electrical contact device, and a compression spring pressing against the contact head on the side opposite the electrical contact point, wherein the guide means comprise geometric shapes whose cross-sections projected in the plane perpendicular to the longitudinal axis fit into each other without interference and are twisted in a helical movement of the same winding direction and the same helix pitch along the longitudinal axis,allowing greater electrical and mechanical contact.,

[0034] Such an electrical contact device thus makes it possible to provide low electrical resistance and high wear resistance without requiring the implementation of costly arrangements such as using elastic materials to produce the contact head, elastic interface elements or electrical connection shunts, these geometric shapes are provided on the respective guide surfaces of the contact head and the contact body.

[0035] Advantageously, the guidance means include:

[0036] • at least one helical groove extending along a guide face of one of the contact body and the contact head • at least one helical twisted rib with the same winding direction and the same helix pitch as the helical grooves, extending along a guide face of the other of the contact body and the contact head, the flank of the helical groove cooperating with the flank of the helical rib by establishing at least one contact generator passing through a point of contact established at the contact between a cross-section of the contact body and a cross-section of the contact head.

[0037] Advantageously, the contact generator extends over at least part of the length of the helical groove or the helical rib extending along the guide face of the contact head or the contact body, for example at least 10%, at least 30%, at least 50%, or preferably over the entire length.

[0038] Advantageously, the cooperation between the flank of the helical groove and the flank of the helical rib establishes a contact surface between the contact body and the contact head, making it possible to further improve the above advantageous effects. This contact surface may extend, continuously or discontinuously, over part or preferably the entire length of the groove and / or the rib.

[0039] Advantageously, the cross-section of the helical groove and / or the helical rib has a triangular, trapezoidal or curvilinear shape. The triangular shape allows, for the same space requirement, to have a longer contact generatrix and / or contact surfaces. The curvilinear shape can allow for easier manufacturing by material upsetting and therefore less costly while reducing internal stresses. The trapezoidal shape can allow for greater manufacturing tolerances and / or better resistance to temperature changes.

[0040] Another aspect of the present description relates to an electrical contact device comprising: at least one metallic contact body, a movable metallic contact head comprising an end arranged to define an electrical contact point when cooperating with an opposing electrically conductive element, guide means arranged to guide a movement of the movable metallic contact head relative to the contact body along a longitudinal axis of the electrical contact device, as well as a compression spring pressing against the contact head on the side opposite the electrical contact point, wherein the guide means comprise:

[0041] • at least one helical groove extending along a guide face of one of the contact body and the contact head

[0042] • at least one helical twisted rib with the same winding direction and the same helix pitch as the helical grooves, extending along one guide face of the other of the contact body and the contact head, the flank of a helical groove cooperating with the flank of a helical rib by establishing at least one contact generator passing through a point of contact established at the contact between a cross-section of the contact body and a cross-section of the contact head.

[0043] Another aspect of the description makes it possible to combine aspects described above and relates to an electrical contact device with a piston capable of cooperating with an opposing electrically conductive element located opposite the movable head of the piston and comprising at least one metal contact body, a movable metal contact head guided by the contact body along a longitudinal axis of translation as well as a compression spring pressing against the contact head on the side opposite the opposing external element, the cylindrical contact head having, on the side opposite the bearing face of the spring, an end in the form of a spherical or pointed cap provided to establish a point electrical contact with the opposing element opposite, characterized in that:

[0044] • on the one hand, the contact body defines a cylindrical axial volume for guiding the contact head comprising a straight cylindrical surface of circular section perpendicular to the longitudinal axis of the axial guide volume and having at least one hollow guide surface of twisted geometric shape resulting from the extension, along the axial guide volume and in a helical movement along the longitudinal translation axis, of a non-circular straight section perpendicular to the longitudinal translation axis including at least one hollow shape tangent to the projection of the circular section, this hollow helical guide surface of the contact body cooperating with at least one volume projecting from the axial guide volume of the contact head,projecting volume whose cross section perpendicular to the longitudinal axis of translation is included in the cross section perpendicular to the axis of translation defined by the axial volume of the contact body with its hollow volume(s) and having a profile capable of passing through said cross section of the contact body while being blocked in rotation thanks to the opposition of at least one side of the depth of the projecting element of the contact head against a hollow side of the profile of the contact body,

[0045] • on the other hand, a second longitudinal axis passing through the electrical contact point located at the end of the contact head, parallel to the longitudinal axis of translation of the contact head in the contact body, has a lateral offset relative to the longitudinal axis of translation.

[0046] Advantageously, the hollow helical surfaces of the contact body are constituted by one or more twisted grooves extending along the inner guide face of the contact body.

[0047] Advantageously, the volume(s) projecting from the guide surface of the contact head cooperating with the groove(s) of the contact body are of straight cylindrical shape with a circular section or of conical shape whose axes extend radially in a plane perpendicular to the longitudinal axis of translation.

[0048] Advantageously, the volume(s) projecting from the guide surface of the contact head cooperating with the groove(s) of the contact body are constituted by helical twisted ribs of the same winding direction and the same helix pitch as the twisted grooves of the contact body extending over the entire guide length of the contact head, the flank of a groove of the contact body cooperating with the flank of a rib of the contact head by establishing at least one contact generator passing through a point of contact established at the contact between the cross section of the contact body and the cross section of the contact head and extending over the entire length of the ribs.

[0049] Advantageously, the volume(s) projecting from the guide surface of the contact head cooperating with the groove(s) of the contact body are constituted by helical twisted ribs of the same winding direction and the same helix pitch as the twisted grooves of the contact body extending over a length shorter than the guide length of the contact head.

[0050] Advantageously, the hollow helical guide surfaces of the contact body and the projecting helical volumes of the contact head are formed by twisted grooves in the contact body on the contact head, with parallel sides or curvilinear sides, with the same winding direction and the same helix pitch, the cross sections of which fit into each other without interference. Advantageously, the placement of the hollow helical guide surfaces (and that of the projecting guide shapes) is reversed so that the hollow guide shapes are located on the guided volume of the contact head and the projecting guide shapes are located in the bore of the contact body.

[0051] Advantageously, the movable contact head has a straight cylindrical guide surface of circular section located inside and is guided longitudinally by a straight cylindrical surface of circular section located on the outside of the contact body, at least one of the cylindrical guide surfaces of these two components, either that belonging to the contact body or that belonging to the contact head, having at least one hollow or projecting helical longitudinal guide surface cooperating with at least one volume belonging to the other component whose cross section is of a shape complementary to the cross section, perpendicular to the longitudinal translation axis, of the helical surface in order to allow the helical translation movement of the contact head on the contact body.

[0052] Advantageously, the point of application of the force of the compression spring on the contact head passes through an axis parallel to the guide axis of the contact body and laterally offset from the axis passing through the contact point located at the end of the contact head.

[0053] The aspects described above concern different realizations and improvements of the same object and can therefore be freely combined.

[0054] Finally, an electrical apparatus is described comprising at least one electrically conductive element, at least one other electrically conductive element and an electrical contact device according to the above aspects. The electrical contact device thus enables reliable transmission of power or an electrical signal between the electrically conductive elements which can move and / or vibrate relative to each other.

[0055] Presentation of figures

[0056] The present description will be better understood thanks to the following description which relates to preferred embodiments, given as non-limiting examples, and explained with reference to the appended schematic drawings in which:

[0057] [Fig. 1] is a schematic illustration in perspective view of a first example of a self-cleaning contact piston contact according to the present description in an embodiment with a contact body with internal guide surfaces comprising 6 helical grooves cooperating with a contact head guided inside the contact body and having 6 projecting pins, the contact body being shown partially cut longitudinally in order to facilitate understanding. [Fig. 2] is a schematic illustration in exploded perspective view of the first example of a self-cleaning contact piston contact according to the present description and corresponding to the illustration [Fig. 1], the contact body being seen in its entirety with its hidden edges.

[0058] [Fig. 3] is a schematic illustration in exploded perspective view of the first example of a self-cleaning contact piston contact according to the present description and corresponding to the illustration [Fig. 2], the contact body being shown partially cut away to facilitate understanding of its interior part, one of the nipples of the contact head being shown in enlarged detail view.

[0059] [Fig. 4] is a schematic illustration in front view with its corresponding longitudinal sectional view of the first example of a self-cleaning contact piston contact according to the present description and corresponding to the illustration [Fig. 1] highlighting the radial offset of the end of the contact head relative to the guide axis of the contact body and the axis of the spring.

[0060] [Fig. 5] is a schematic illustration in perspective view of a second example of a self-cleaning contact piston contact according to the present description in an embodiment with a contact body comprising 6 helical grooves cooperating with a contact head having 6 helical projecting ribs extending along the entire length of the contact head, the contact body being shown partially cut away to facilitate understanding.

[0061] [Fig. 6] is a schematic illustration in exploded perspective view of the second example of a self-cleaning piston contact according to the present description and corresponding to the illustration [Fig. 5], the contact body being seen in its entirety with its edges hidden.

[0062] [Fig. 7] is a schematic illustration in exploded perspective view of the second example of a self-cleaning contact piston contact according to the present description and corresponding to the illustration [Fig. 5], the contact body being shown partially cut away to facilitate understanding of its interior part.

[0063] [Fig. 8] is a schematic illustration in perspective view of a third example of a self-cleaning contact piston contact according to the present description in an embodiment with a contact body comprising 6 helical grooves cooperating with a contact head having 6 short helical projecting ribs of short length relative to the contact head, the contact body being shown partially cut away.

[0064] [Fig. 9] is a schematic illustration in exploded perspective view of the third example of a self-cleaning contact piston contact according to the present description and corresponding to the illustration [Fig. 8], the contact body being shown partially cut away to facilitate the understanding of its interior part, one of the short ribs of the contact head being shown in enlarged detail view.

[0065] [Fig. 10] is a schematic illustration in perspective view of a fourth example of a self-cleaning contact piston contact according to the present description in an embodiment with a contact body comprising recessed helical grooves cooperating with a contact head provided with projecting helical grooves, the contact body being shown partially cut away.

[0066] [Fig. 11] is a schematic illustration in exploded perspective view of the fourth example of a self-cleaning piston contact according to the present description and corresponding to the illustration [Fig. 10], the contact body being shown partially cut longitudinally in order to facilitate the understanding of its interior part.

[0067] [Fig. 12] is a schematic illustration in perspective view of a fifth example of a self-cleaning contact piston contact according to the present description in an embodiment with a contact body of hexagonal cross-section extending helically and cooperating with a contact head also of helical hexagonal section, the contact body being shown partially cut away.

[0068] [Fig. 13] is a schematic illustration in front view with its corresponding longitudinal sectional view of the fifth example of a self-cleaning contact piston contact according to the present description and corresponding to the illustration [Fig. 12] highlighting the radial offset of the end of the contact head relative to the guide axis of the contact body and relative to the axis of the spring and proposing an alternative connection of the contact body with an end piece.

[0069] [Fig. 14] shows three schematic representations of contact generatrices appearing between a hollow guide form of a contact body defining an axial inner housing associated with a projecting guide form of a contact head guided inside the contact body.

[0070] [Fig. 15] is a schematic illustration in perspective view of a sixth example of a self-cleaning contact piston contact according to the present description in an embodiment with a contact body whose guide surface is an outer surface provided with helical grooves cooperating with a contact head located outside the contact body and provided with an inner guide surface having helical grooves corresponding to those of the contact head.

[0071] [Fig. 16] is a schematic illustration in front view with its corresponding longitudinal sectional view of the sixth example of a self-cleaning contact piston contact according to the present description and corresponding to the illustration [Fig. 15] highlighting the radial offset of the end of the contact head relative to the guide axis of the contact body and relative to the axis of the spring

[0072] Detailed description

[0073] There is generally described an electrical contact device comprising a contact head movable relative to a contact body, the contact body and the contact head may each be in electrical contact with a different electrically conductive element, so as to ensure electrical contact and therefore the transmission of electrical power and / or signal between these different conductive elements. Guide means or guide surfaces may be provided so that one of the contact head and the contact body performs a relative helical movement when it is subjected to an external force.

[0074] For example, an electrical contact device with a piston 50 capable of cooperating with an opposing electrically conductive element located opposite the movable head of the piston and comprising at least one metal contact body 1, a movable metal contact head 2 guided by the contact body 1 along a longitudinal translation axis 16 as well as a compression spring 4 pressing against the contact head 2 on the side opposite the opposing external element, the contact head 2 of cylindrical shape having, on the side opposite the bearing face of the spring 4, an end 25 in the form of a spherical or pointed cap provided to establish a point electrical contact C1 with the opposing element opposite, characterized in that:

[0075] • on the one hand, the contact body 1 defines a cylindrical axial volume for guiding the contact head 2 comprising a straight cylindrical surface of circular section 11 perpendicular to the longitudinal axis 16 of the axial guide volume and having at least one hollow guide surface of twisted geometric shape 12 or 12' or 19 resulting from the extension, along the axial guide volume and in a helical movement along the longitudinal translation axis 16, of a non-circular straight section perpendicular to the longitudinal translation axis 16 including at least one hollow shape tangent to the projection of the circular section, this hollow helical guide surface 12 or 12' or 19 of the contact body 1 cooperating with at least one projecting volume 22 or 27 or 28 or 29 on the axial guide volume 21 of the contact head 2,projecting volume whose cross section perpendicular to the longitudinal axis of translation 16 is inscribed in the cross section perpendicular to the axis of translation 16 defined by the axial volume of the contact body 1 with its hollow volume(s) 12 or 12' or 19 and having a profile capable of passing through said cross section of the contact body 1 while being blocked in rotation thanks to the opposition of at least one side of the depth of the projecting element 22 or 27 or 28 or 29 of the contact head 2 against a hollow side of the profile of the contact body 1,

[0076] • on the other hand, a second longitudinal axis 26 passing through the electrical contact point C1 located at the end of the contact head 2, parallel to the longitudinal translation axis 23 of the contact head 2 in the contact body 1, has a lateral offset A relative to the longitudinal translation axis 23.

[0077] These various characteristics give the device, on the one hand, the ability to generate a self-cleaning trajectory in an arc of a circle of amplitude “T” at the contact point Cl at the end of the contact head 2, a trajectory that is all the longer and more effective as the lateral offset A is significant, and on the other hand, the ability to create at the same time one or more internal contact points or generatrices or surfaces between the hollow helical guide volumes cooperating with the projecting helical guide volumes, thus promoting wear resistance, mechanical endurance as well as good continuity of passage of the electric current and current capacity.

[0078] The amplitude “T” of the self-cleaning trajectory is calculated with the following equation:

[0079] T= (2.7iAc) / P

[0080] • A being the lateral offset of the contact point Cl relative to the axis of the guide 16,

[0081] • c representing the value of the contact head’s depression stroke,

[0082] • P representing the value of the helix pitch of the helical twist.

[0083] Examples of achievements

[0084] According to a particular embodiment which is not limiting within the scope of the present description and illustrated by figures [Fig. 1] to [Fig. 13], the contact head 2 is guided in the interior volume of the contact body 1 by guide means. According to this configuration, the contact body 1 has two openings located at each end of its interior cylindrical volume:

[0085] • a fully open opening 18 capable of allowing the contact head 2 to pass through in its entirety and which accommodates, by means of a rigid connection, a terminal part 3 for closing the interior volume and connecting to the electrical circuit. • a partially open opening 15 located opposite the opening 18 allowing the end 25 intended for the electrical contact of the contact head 2 to protrude. According to a non-limiting example of embodiment as represented by the illustrations [Fig.

[0086] 1] to [Fig. 11], the contact body 1 has, at the opening 18, a thread 13 capable of receiving the corresponding thread 33 located at the end of the terminal part 3. The terminal part 3 is thus screwed into the contact body 1 until its shoulder 34 comes into abutment against the contact body 1.

[0087] According to a second non-limiting exemplary embodiment as represented by the illustrations [Fig. 12] and [Fig. 13], the thickness of the contact body 1 at the end 18 is sufficiently thin to be deformed by crimping and stamping on the corresponding end of the terminal part 3 provided with a groove 34 hollowed locally and radially with one or more shallow holes 35 so that the radial deformation 36 of the end of the contact body 1 obtained after stamping completely secures the contact body 1 with the terminal part 3.

[0088] According to a non-limiting exemplary embodiment as represented by the illustrations [Fig. 1] to [Fig. 9], the end opening 15 of the contact body 1 is obtained by pushing back in the direction of the translation axis 16 a cylindrical wall extending the internal guide volume of the contact body 1 until a wall 14 is raised which is capable of opposing the complete crossing of the contact head 2 by obstructing the shoulder 24 of the contact head 2 defined by the transition between the guide volume 21 increased by the volume of the projecting elements 22 or 27 or 28, intended for guidance in the contact body 1 and the end 25 of smaller section intended to carry the external contact point Cl.

[0089] According to a non-limiting exemplary embodiment as represented by the illustrations [Fig. 10] and [Fig. 11], the end opening 15 is produced by embedding a ring 17 in the contact body 1, the passage dimension of which in its center is less than the largest radial dimension of the guide volume of the contact head 2. This ring 17 is made integral with the contact body 1 by any means such as shrinking or welding or crimping or other.The flank of this ring 17 which is oriented towards the inside of the contact body 1 prevents the contact head 2 from passing completely through by obstructing the shoulder defined by the transition between the volume 21 increased by the volume of the projecting elements 29 intended for guidance in the contact body 1 and the volume 25 of smaller section intended to carry the external contact point CL. It should also be noted that, in order to allow the correct passage of the end 25 intended for the electrical contact of the contact head 2, the dimension of the opening 15 must be increased relative to the transverse dimension of the end 25 to take into account the variation in the angular position of the lateral offset A (Delta) during the helical longitudinal movement of displacement carried out by the contact head 2 relative to the contact body 1.Thus, in the case of a non-limiting embodiment of a contact head 2 whose end 25 is of straight cylindrical shape with a circular section and an opening 15 constituted by a cylindrical hole with a circular section with an axis centered on the guide axis 16 of the contact body 1, the diameter of the orifice 15 must at least have the value of the diameter of the end 25 increased by 2 times A (Delta), the value of the lateral offset between the longitudinal guide axis 16 and the parallel axis passing through the external contact point Cl.

[0090] According to the above, the contact head 2 evolves in a cylindrical volume defined by three surfaces:

[0091] • the cylindrical and helical guide surfaces, parts or defining guide means and defining the translation axis 16 here merged with the longitudinal axis of the cylindrical volume and of the electrical contact device,

[0092] • on the side opposite the contact point Cl, a closing surface constituted by the presence of the terminal part 13,

[0093] • at the end of the contact body 1 on the side of the contact point Cl, by the surface resulting from the presence of the reduced opening 15.

[0094] A compression spring 4 is interposed between the end piece 3 and the contact head 2. In the absence of an opposing external element, the contact head 2, whose projecting volume(s) 22 or 27 or 28 or 29 slide in the hollow volumes 12 or 12' or 19 of the contact body, is thus pushed back to the stop on the side of the opening 15 of the contact body 1, leaving the volume 25 or extreme protrusion protruding outside the contact body 1 at the end of which the point of contact C1 will be established with the opposite external element.

[0095] Example of operation

[0096] When an opposing element presents itself opposite by establishing contact with the contact head 2 at its contact point C1 while approaching the contact body 1, the contact head 2 is pushed back inside the contact body 1 in the direction of the end piece 3 while compressing the spring 4. The flank or flanks of the projecting helical volume(s) 22 or 27 or 28 or 29 of the contact head 2 comes into contact with the flank or flanks of the hollow helical volume(s) 12 or 12' or 19 of the contact body 1 at at least one internal contact point C1 by developing a reaction force normal to the contact surface of the flanks of the volumes, thus defining guiding means.As the outer element approaches the contact body 1 and the contact head 2 sinks deeper, the internal contact point Ci slides on the flank of the corresponding hollow volume 12 or 12' or 19 following the same helical trajectory as this or these volumes 12 or 12' or 19 while causing a tangential force on the contact head 2. This helical displacement movement and the tangential contact force associated with the internal contact point Ci causes a rotational movement of the contact head, the amplitude of which is a function of the sinking stroke and the helix pitch of the helical volume(s). Driven by the projecting volumes 22 or 27 or 28 which are guided by the hollow volumes 12 or 12' or 19 of the contact body 1, the contact head 2 moves inside the guide volume of the contact body 1 following a helical translational movement.Under the effect of the thrust of the spring 4 on the contact head 2, the reverse movement of helical translation of the contact head 2 occurs when the opposing external element moves away from the contact body 1 until the contact head 2 returns to the stop at the bottom of the guide volume of the contact body 1 on the side of the opening 15.

[0097] It should be noted that the fact of producing in the contact body 1 at least two hollow and diametrically opposed helical guide volumes 12 or 12' or 19 cooperating with at least two projecting guide volumes 22 or 27 or 28 or 29 integral with the contact head 2 creates the appearance of at least 2 internal contact points Ci, namely at least 1 internal contact point Ci at each pair of hollow and projecting volume, which improves the rotational torque effect on the contact head while reducing the reaction force at each internal contact point Ci. This arrangement can be extended to a larger number of hollow guide volumes distributed in the contact body 1 and cooperating with an equally larger number of projecting guide volumes on the contact head 2 distributed in correspondence with the hollow volumes of the contact body 1.This arrangement makes it possible to reduce the reaction contact forces proportionally to the number of pairs of cooperating recessed and projecting volumes and, consequently, to reduce wear and improve endurance. Another favorable consequence of the multiplication of internal contact points Ci is the multiplication of the points of passage of the electric current between the contact head 2 and the contact body 1, which contributes to reducing the electrical resistance and increasing the current capacity of the electric piston contact 50.

[0098] Other examples of achievement

[0099] According to an example relating to a particular construction variant of the device, the hollow helical surfaces 12 of the contact body 1 are constituted by one or more twisted grooves 12 extending along the inner face 11 of the contact body 1. This particular arrangement of grooves allows the use of proven mechanical means such as for example machining by chip removal or material pushing by means of rolling tooling related to thread rolling for the production in large series of contact bodies 1 with high qualities of precision and surface finish while optimizing manufacturing costs. As non-limiting examples of embodiment, figures [Fig. 1] to [Fig. 9] show guide means with 6 grooves distributed at regular intervals on the periphery of the guide cylinder 21.

[0100] According to an example relating to a particular construction variant of the device, the projecting elements on the guide surface of the contact head 2 cooperating with the groove(s) 12 of the contact body 1 are of straight cylindrical shape with a circular section or of conical shape 22 whose axes extend radially in a plane perpendicular to the longitudinal translation axis 23. This particular arrangement makes it possible to produce projecting volumes in a simple manner, for example by embedding projecting inserts in the contact head 2 in a radial arrangement.In the case where the section of the grooves 12 of the contact body has parallel sides, it will be necessary to embed inserts whose projecting part on the contact head 2 will have the shape of a right circular cylinder with a diameter slightly smaller than the distance between the sides of the grooves of the contact body so that the side of each right cylinder cooperates with the side of each groove by means of a rectilinear contact generator instead of a simple contact point Ci. In the case where the section of the grooves 12 of the contact body has oblique sides, it will be necessary to embed inserts whose projecting part on the contact head 2 will have a conical shape with the same angle at the top as that formed by the sides of the grooves so that the side of each cone cooperates with the side of each groove by means of a contact generator C2 instead of a simple contact point Ci as illustrated by view A located on the left of the figure [Fig.14], This construction has the advantage of extending the internal contact areas and, therefore, reducing wear, improving endurance and reducing internal electrical contact resistance.

[0101] According to another example relating to a particular construction variant of the device, the helical elements projecting from the guide surface of the contact head 2 cooperating with the groove(s) 12 of the contact body 1 are constituted by twisted ribs 27 of the same winding direction and the same helical pitch as the twisted grooves 12 of the contact body 1 and extend over the entire guide length 21 of the contact head 2, the flank of a groove 12 of the contact body 1 cooperating with the flank of a rib 27 of the contact head 2 by establishing at least one contact generatrix passing through an internal contact point Ci established at the contact between the cross section of the contact body 1 and the cross section of the contact head 2 and extending over the entire length of the ribs 27. This particular arrangement, illustrated by [Fig. 5], [Fig. 6] and [Fig.7], allows the appearance of internal contact generators between each groove 12 of the contact body 1 cooperating with a rib 27 of the contact head 2, the length of each generator being equal to the developed length of each rib 27 of the contact head. This construction has the advantage of providing very long contact lines, both mechanical and electrical, which, on the mechanical level, contributes to very significantly reducing the contact pressure at the supports along these generators and thereby reducing wear and increasing endurance, and on the electrical level, contributes to reducing the current density at the crossing points along these generators and thereby increasing the current capacity of the electrical contact with piston 50.

[0102] It should be noted that, since the geometry of the surfaces of the helical grooves 12 and ribs 27 allows the appearance of generators C2 as defined in a section plane as illustrated by view A located to the left of the figure [Fig. 14], it is no longer only contact generators which appear at the interfaces between grooves 12 and ribs 27, but indeed contact surfaces, further increasing the endurance capacity and the current capacity of the electrical contact device with piston 50 according to the present description.

[0103] According to another example relating to a particular construction variant of the device, the helical elements projecting from the guide surface of the contact head 2 cooperating with the groove(s) 12 of the contact body 1 are constituted by twisted ribs 28, with the same winding direction and the same helical pitch as the twisted grooves 12 of the contact body 1 and extending over a length L shorter than the guide length 21 of the contact head 2. This arrangement illustrated by [Fig. 8] and [Fig. 9] reproduces, with lower performance, the same characteristics as those of the previous example illustrated by [Fig.5] describing ribs 27 extending along the entire guide volume of the contact head 2, but allowing for simplification of manufacturing, which consequently reduces the manufacturing cost because it requires less precision in the production of the helical grooves 12 and the helical ribs 28 since the latter are of reduced length. Although the contact surfaces are less extensive than in the case of longer ribs, this arrangement nevertheless provides a significant improvement in terms of endurance capacity and current capacity compared to the construction using projecting guide volumes of circular cylindrical or conical shape as described above and illustrated by [Fig. 1] to [Fig.3] since it brings at least contact generatrices of length close to the length L of the ribs 28, and in the case of careful production of higher precision, it brings contact surfaces of extent close to the product “LxC2” with as many contact surfaces of this dimension as there are pairs of grooves 12 cooperating with short ribs 28.

[0104] According to another example relating to a particular construction variant of the device, the hollow helical guide elements of the contact body 1 and those projecting from the contact head 2 are constituted by twisted grooves 19 in the contact body 1 and 29 on the contact head 2, with parallel sides or curvilinear sides, with the same winding direction and the same helical pitch, the cross sections of which, perpendicular to the translation axis 16, fit into each other without interference. According to this construction variant illustrated by [Fig. 10] and [Fig. 11], the geometry softened by the radii at the bottom and at the top of the grooves with curvilinear sides 19 and 29 makes it possible to reduce the internal stresses of the material of the body 1 and of the head 2 and to envisage more easily obtaining the parts by material upsetting.Since, in the cross-section perpendicular to the translation axis 16, the bottom and top radii of the grooves 19 and 29 are connected by a straight line, an internal contact generator C3 also appears as illustrated by view B located in the center of the figure [Fig. 14]. This particular construction variant therefore also offers a high endurance capacity and a high electric current capacity, these capacities being all the greater as the number of grooves 19 and 29 distributed over the guide surfaces 11 for the contact body and 21 for the contact head is large. The production of a large number of grooves 19 and 29 will be all the easier as the grooves are of shallow depth and small dimensions.An alternative form of shallow grooves can be obtained by using a generally triangular groove profile which allows, with the same space requirement as the grooves with a curvilinear profile, to have contact generatrices C4 longer than C3 as illustrated by view C located on the right of the figure [Fig. 14].

[0105] According to another example relating to a particular construction variant of the device, the hollow helical guide surfaces of the contact body 1 and the projecting helical volumes of the contact head 2 are derived from geometric shapes whose cross sections projected in the plane perpendicular to the longitudinal axis of translation 16 fit into each other without interference and are twisted in a helical movement of the same winding direction and the same helix pitch along the longitudinal axis of translation (16). It should be noted that the type of geometric shapes is not limited to only a few types of shapes. This arrangement is achievable as soon as two geometric shapes, not necessarily of the same type, can fit into each other without interference and without the possibility of turning one into the other by establishing at least two point contacts.Thus, without departing from the scope of the present description, it is possible to produce contact bodies 1 and contact heads 2 having guide volumes one inside the other defined in the cross section perpendicular to the guide axes 16 or 23 by two squares, two hexagons as illustrated by [Fig. 12] and [Fig. 13] generating guide volumes in hollow 12' and in projection 27', or two octagons, or two ovals, etc.

[0106] It should also be noted that this arrangement opens up other possibilities for producing the contact body 1 and the contact head 2, in particular for example by the use of twisted tubular profiles, without these embodiments being limiting for the production of piston contacts 50 according to the present description.

[0107] According to another example relating to a particular construction variant of the device, the placement of the hollow helical guide shapes 12 or 19 and that of the projecting guide shapes 22 or 27 or 28 or 29 is reversed so that the hollow guide shapes are located on the guided volume 21 of the contact head 2 and the projecting guide shapes are located in the bore 11 of the contact body 1. This construction variant with reversed guide shapes allows other ways of producing the contact body 1 and the contact head 2 without calling the principle of the device into question and without modifying the relative behavior of the contact head 2 with respect to the contact body 1 or the endurance and current capacity properties of the piston contact.

[0108] According to another example relating to a particular construction variant of the device, the movable contact head 2 has a straight cylindrical guide surface of circular section located inside and is guided longitudinally by a straight cylindrical surface of circular section located on the outside of the contact body 1, at least one of the cylindrical guide surfaces of these two components, either that belonging to the contact body 1, or that belonging to the contact head 2, having at least one hollow or projecting helical longitudinal guide surface 19' or 29' cooperating with at least one volume belonging to the other component whose cross section is of a shape complementary to the cross section, perpendicular to the longitudinal translation axis 16, of the helical surface in order to allow the helical translation movement of the contact head 2 on the contact body 1.This construction variant also opens up new possibilities for producing the contact body 1, which becomes an inner part of the assembly, and the contact head 2, which becomes an outer part of the assembly, without departing from the scope of the present description. As a non-limiting example, [Fig. 15] and [Fig. 16] show an electrical contact with a piston with a self-cleaning contact 50, the contact head 2 of which is guided on the outer cylindrical face of the contact body 1, the inner guide surface of the contact head 2 carrying helical grooves with a curvilinear flank 19' cooperating with helical grooves with a curvilinear flank 29' of the same direction and the same helix pitch belonging to the contact body 1. The contact body 1 also acts as an end piece for connection to the electrical circuit.The longitudinal axis 26 passing through the external contact point Cl located at the end of the end 25 or extreme protrusion of the contact head 2 is offset laterally by a value A relative to the longitudinal guide axis 16 of the contact body 1.

[0109] It should be noted that this provision can be combined with all the preceding characteristics without departing from the scope of this description.

[0110] According to another example relating to a particular construction variant of the device, the point of application of the force of the compression spring 4 on the contact head 2 passes through an axis parallel to the guide axis of the contact body 16 and laterally offset relative to the axis 26 passing through the contact point C1 located at the end 25 of the contact head 2. This construction variant, in which the thrust force of the spring 4 is not aligned with the contact point C1, causes a torque of tilting force of the contact head 2 around its external contact point C1. The contact head 2 being guided by the contact body 1, this results in the appearance of a radial reaction contact force opposing the tilting of the contact head 2. This radial force increases the contact force at its location, locally promoting the passage of the current.

[0111] An electrical contact device according to the present description can be produced by any known method and preferably by machining methods such as turning, tapping, boring, broaching, milling, bar turning, threading, molding methods and / or by additive manufacturing.

[0112] Of course, the description is not limited to the embodiments described and represented in the attached drawings which can be combined. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection as defined by the attached claims.

Claims

Claims 1. An electrical contact device comprising: at least one metal contact body, a movable metal contact head comprising an end protrusion arranged to define an electrical contact point when cooperating with an opposing electrically conductive element, guide means arranged to guide a movement of the movable metal contact head relative to the contact body along a longitudinal axis of the electrical contact device, and a compression spring pressing against the contact head on the side opposite the electrical contact point, wherein the end protrusion and the guide means are arranged to impose a helical trajectory on the contact point during a relative movement of the contact head relative to the contact body.

2. An electrical contact device according to claim 1, wherein a second longitudinal axis, passing through the electrical contact point and parallel to the longitudinal axis, has a lateral offset relative to the longitudinal axis.

3. Electrical contact device according to claim 1 or 2, wherein one of the contact head and the contact body is cylindrical in shape and circular in cross-section and the other of the contact head and the contact body defines an axial guide volume of right cylindrical shape and circular in cross-section.

4. Electrical contact device according to one of claims 1 to 3, in which the guide means comprise geometric shapes whose cross sections projected in the plane perpendicular to the longitudinal axis fit into one another without interference and are twisted in a helical movement with the same winding direction and the same helix pitch along the longitudinal axis.

5. Electrical contact device according to one of claims 1 to 4, in which the guide means comprise: • on one of the contact head and the contact body, at least one hollow guide surface of twisted shape around the longitudinal axis, • on the other of the contact head and the contact body, at least one projection transverse to the longitudinal axis and adapted to be received in the hollow guide surface.

6. Electrical contact device according to claim 5, in which the hollow guide surface results from the extension, along the axial guide volume and in a helical movement along the longitudinal translation axis, of a non-circular straight section perpendicular to the longitudinal axis including at least one hollow shape tangent to the projection of the circular section or opening into the circular section.

7. Electrical contact device according to claim 5 or 6, wherein the at least one recessed guide surface is constituted by at least one helical groove extending along a guide face of the contact body or the contact head.

8. Electrical contact device according to claim 7, in which the projecting volume is constituted by at least one helical rib of the same winding direction and the same helical pitch as the helical groove, the flank of the helical groove cooperating with the flank of the helical rib by establishing at least one contact generator passing through a contact point established at the contact between a cross-section of the contact body and a cross-section of the contact head.

9. Electrical contact device according to one of claims 2 to 8, a point of application of the force of the compression spring on the contact head passes through an axis parallel to the longitudinal axis and laterally offset relative to the second longitudinal axis passing through the contact point located at the end of the contact head.

10. An electrical contact device comprising: at least one metal contact body, a movable metal contact head comprising an end arranged to define an electrical contact point when cooperating with an opposing electrically conductive element, guide means arranged to guide a movement of the movable metal contact head relative to the contact body along a longitudinal axis of the electrical contact device, and a compression spring pressing against the contact head on the side opposite the electrical contact point, wherein the guide means comprise geometric shapes whose cross-sections projected in the plane perpendicular to the longitudinal axis fit into each other without interference and are twisted in a helical movement of the same winding direction and the same helix pitch along the longitudinal axis.

11. Electrical contact device according to claim 10, wherein the guide means comprise at least one helical groove extending along a guide face of one of the contact body and the contact head, and at least one helical twisted rib of the same winding direction and the same helix pitch as the helical grooves, extending along a guide face of the other of the contact body and the contact head, the flank of a helical groove cooperating with the flank of a helical rib by establishing at least one contact generator passing through a point of contact established at the contact between a cross-section of the contact body and a cross-section of the contact head.

12. An electrical contact device according to claim 11, wherein the contact generatrix extends over at least a portion of the length of the helical groove or helical rib extending along the guide face of the contact head or contact body.

13. Electrical contact device according to one of claims 8, 11 and 12, in which the cooperation between the flank of the helical groove and the flank of the helical rib establishes a contact surface between the contact body and the contact head.

14. Electrical contact device according to one of claims 8 and 11-13, wherein the cross-section of the helical groove and / or the helical rib has a triangular, trapezoidal or curvilinear shape.

15. Electrical apparatus comprising at least one electrically conductive element, at least one other conductive element and an electrical contact device according to one of claims 1 to 14.

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