Patent Publication Number: US-11657991-B2

Title: Electrical switch

Description:
RELATED APPLICATIONS AND CLAIM OF PRIORITY 
     This patent document claims priority to French Patent Application No. 2103490 filed Apr. 6, 2021, the entirety of which is incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a long-life, high-reliability electrical switch that provides excellent tactile feel when operated axially. 
     The invention relates more particularly to an electrical switch in which the tactile sensation results from the cooperation of an elastically deformable ring, and for example the free end turn of a compression coil spring, with a ramp of the upper actuating rod which is passed by the elastic ring which deforms radially during the actuating travel of the switch. 
     Description of the Related Art 
     U.S. Pat. No. 4,451,719, which issued May 29, 1984 to Lauterburg and Geiger, and which claims priority to French patent FR2420834, proposes the design of an electrical switch, also called an electric switch, with a tactile effect and axial actuation, comprising, with reference to the Figures of that patent: a lower base or casing 6. 
     The switch of U.S. Pat. No. 4,451,719 also comprises an upper actuating rod, or push-button, 1 comprising a section 18 whose cylindrical side wall is guided axially in sliding manner in a guide bore formed in the lower base; an elastic member for returning the upper actuating rod to a high rest position, switch in which, under the action of an actuating force applied to the upper actuating rod and against the force exerted by the elastic return member, the upper actuating rod 1 moves axially with respect to the lower base, along an actuating travel, to an active lower position for changing the state of at least one electrical switching way. 
     The switch of U.S. Pat. No. 4,451,719 also comprises comprising an elastic ring 17 which: (a) is arranged in a peripheral housing formed in the side wall; (b) is traversed axially by the said section of the upper actuating rod; (c) during the actuating travel of the upper actuating rod 1, bears axially downwards against a fixed stop face 18 belonging to the lower base 6; and (d) during the actuation travel of the upper actuation rod 1, cooperates with a cam profile 20 formed in said side wall which radially deforms the said elastic ring to produce an elastic resistance to the actuation of the upper actuation rod. 
     The detailed description and figures of U.S. Pat. No. 4,451,719 are fully incorporated into this document by reference. 
     The purpose of such a design is to solve the problem of the user&#39;s uncertainty as to the reality of the implementation of the function he has controlled by means of the switch by acting on the upper actuating rod. 
     This is achieved by the tactile sensation he perceives when he acts on the upper actuating rod. 
     This principle has been implemented by C&amp;K Components S.A. in the design of its “K12S” pushbutton switch. 
     The last free end turn of the return spring interacts with the actuator ramp which creates several forces, including a radial force which causes the opening of the last turn and determines the mechanical characteristics of the switch, and an axial force which pushes the last turn of the return spring axially downwards in the direction of the actuating travel, this last turn being in principle axially stopped by the fixed annular stop face belonging to the lower base. 
     The combination of these two forces causes the last turn to be pushed radially outwards. 
     There is a risk that the last turn of the spring will be trapped between the ramp of the upper actuating rod and the lower base plate, which can then lead to a significant increase in actuating force and/or to an uncontrolled variation in actuating force and an increase in the range of values of this actuating force in the technical specification of the product. 
     The present application describes a novel electrical switch that provides improvements over the prior art listed above. 
     SUMMARY 
     This document describes a new electrical switch of the aforementioned type which provides a tactile sensation by an elastically deformable ring. In various embodiments of the switch, the guide bore comprises a series of axial ribs, each of which projects radially towards the interior of the guide bore and is slidably received in a complementary axial groove formed in the side wall. The fixed stop surface is constituted by the upper radial end facets of each axial rib. 
     In some embodiments, the housing may be delimited axially downwards by a lower radial shoulder and upwards by the cam profile. 
     In any of the embodiments described above, the cam profile may be a cone section whose apex is oriented axially downwards, forming a ramp with which the elastic ring cooperates. 
     In any of the embodiments described above, each axial groove formed in the side wall may extend axially upwards beyond the cam profile. 
     In any of the embodiments described above, the elastic return member may include a helical compression spring through which the section of the upper actuating rod passes axially. The lower turn of the helical compression spring may constitute the elastic ring. 
     Optionally, the helical compression spring may be mounted to be axially compressed between the upper radial end facets of each axial rib and an upper radial shoulder which axially delimits the section upwards. 
     In some embodiments, an electrical switch with axial actuation includes a lower base comprising a fixed stop surface, an upper actuating rod comprising a section having a cylindrical side wall that is configured to axially slide in a guide bore formed in the lower base, and an elastic member for returning the upper actuating rod to a high rest position. When subjected to an actuating force applied to the upper actuating rod and against the force exerted by the elastic return member, the upper actuating rod is configured to engage in an actuating travel in which the upper actuating rod is displaced axially with respect to the lower base towards an active lower position for changing the state of at least one electrical switching way of the electrical switch. The electrical switch further comprises an elastic ring. The elastic ring is arranged in a peripheral housing formed in the side wall and which is axially traversed by the section of the upper actuating rod which is configured to be, during the actuation travel of the upper actuation rod, in axially downward abutment against the fixed stop surface belonging to the lower base. The elastic ring is also configured to cooperate, during the actuation travel of the upper actuation rod, with a cam profile formed in the side wall, which deforms the elastic ring radially in order to produce an elastic resistance to the actuation travel of the upper actuation rod. The guide bore comprises a series of axial ribs, each of which projects radially inwardly of the guide bore and is slidably received in a complementary axial groove formed in the side wall. The fixed abutment surface is constituted by the radial upper end facets of each axial rib. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention will become apparent from the following detailed description, for the understanding of which reference is made to the attached drawings in which: 
         FIG.  1    is an exploded side view of an example embodiment of an electrical switch according to the invention; 
         FIG.  2    is a cross-sectional view, through a longitudinal and vertical median plane, of the switch in  FIG.  1   ; 
         FIG.  3    is a cross-sectional view, through a vertical and transverse median plane, of the switch in  FIG.  1   ; 
         FIG.  4    is an exploded perspective view of the lower baseplate, return spring and upper actuating rod of the switch of  FIG.  1   ; 
         FIG.  5    is a perspective view of the upper actuating rod of the switch in  FIG.  1   ; 
         FIG.  6    is a perspective view of the upper actuating rod and return spring of the switch in  FIG.  1   ; 
         FIG.  7    is an axial end view of the upper actuating rod of the switch in  FIG.  1   ; 
         FIG.  8 A  is a cross-sectional view through a median longitudinal and transverse plane of the lower base, return spring and upper actuating rod of the switch of  FIG.  1    with the upper actuating rod shown in the upper rest position; 
         FIG.  8 B  is a similar view to  FIG.  8 A  in which the upper actuating rod is shown in the active down position, without the return spring; 
         FIG.  9    is a partial cross-sectional view through a longitudinal and transverse plane along line  9 - 9  of  FIG.  8 A ; 
         FIG.  10    is a similar view to  FIG.  9    which shows a second example of the return spring design with a circular lower end turn. 
     
    
    
     DETAILED DESCRIPTION 
     For the description of the invention and the understanding of the claims, the vertical, longitudinal, and transverse orientations, according to the reference V, L, T shown in the figures, whose longitudinal L and transverse T axes extend in a horizontal plane, will be adopted by way of non-limitation and without restrictive reference to terrestrial gravity. By convention, the vertical axis V is oriented from bottom to top. 
     In the following description, identical, similar or analogous elements will be referred to by the same reference numbers. 
     As used in this document, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. As used in this document, the term “comprising” (or “comprises”) means “including (or includes), but not limited to.” 
     First Example of an Embodiment 
     In the following example, the electrical switch  20  is generally symmetrical in design with respect to the median vertical and longitudinal plane, and with respect to the median vertical and transverse plane. 
     Vertically from bottom to top, the electrical switch  20 —which is illustrated in particular in  FIGS.  1  to  3   —comprises a lower base  22  and an upper actuating rod  24  which is mounted so as to be slidable, along the main vertical axis A, relative to the lower base  22 . 
     The lower base  22 , which forms a housing, is closed at the top by an upper actuating cover  26 , which is mounted so as to be axially displaceable relative to the lower base  22 . 
     The electrical switch  20  further comprises a compression coil spring  28  which is axially interposed between the upper actuating rod  24  and the lower base  22 , and a flexible lateral sealing membrane  30  which cooperates with the upper actuating cover  26  and the lower base  22 . 
     The electrical switch  20  also comprises two elastically deformable electrical contact blades  32  and  34 , each of which is connected to a connection terminal  36 . Thus, by way of example, the electrical switch  20  is here of the normally closed type in which, in the absence of actuation, the two electrical contact blades  32  and  34  elastically abut each other and establish the electrical switching way or path between two associated connection terminals  36 . 
     As a non-limiting example, the electrical switch  20  is of the luminous type and for this purpose comprises a light source  38  which, for example, is a light-emitting diode and which is connected to connection terminals  40  for its supply. 
     The lower base  22  is moulded from plastic around the electrical connection elements of the electrical contact blades  32  and  34  and the light source  38 . 
     The lower base is  22  in the form of a cylindrical housing of axis A, the lower face  42  of which has a pin  44  for fixing to a support element (not shown) such as a printed circuit board. 
     The main body  46  of the lower base  22  defines a lower cavity  48  which is open vertically upwards and an upper cavity  50  of generally circular cylindrical shape which is also open upwards and is defined by the upper edge  52  of the lower base  22 . 
     The two cavities  48  and  50  are delimited from each other by a horizontal radial face  49  which is oriented vertically upwards. 
     The electrical contact blades  32  and  34  extend vertically upwards within the lower base  22  from the bottom  47  of the lower cavity  48 . The light source  38  is also arranged in the bottom  47  of the lower cavity  48 . 
     The side wall  54  of the lower base  22  has a lower radial groove  56  into which a complementary annular rib  58  of the sealing membrane  30  is elastically fitted, and two diametrically opposed vertical axial grooves  60 , closed at their upper ends. 
     The upper actuating cover  26  comprises a horizontal top plate  62  and a cylindrical tubular side wall  64  which comprises two diametrically opposed hooks  66  which extend generally inwardly and each of which is received in an associated groove  60  in the side wall  54  of the lower base  22 . 
     The top plate  62  is centrally perforated and is here closed by a translucent or transparent plate  68  which may, for example, be colored and/or have a pattern and which may allow the lighting of the light source  38  to be viewed. 
     The inner bottom face  70  of the top plate  62  defines a housing  72  which is open axially downwards and has a radial angular indexing finger  74 . 
     The side wall  63  of the top plate  62  has an internal radial groove  76  into which a complementary annular bead  78  of the sealing membrane  30  is elastically fitted. 
     The lower cavity  48  of the lower base has  22  an axial guiding bore  80  in the form of a series of concave sections, of which there are six in this case. 
     The axial guide bore  80  thus formed extends vertically upwards from the bottom  47  and opens axially into the face  49 . 
     In accordance with the invention, the lower cavity  48  of the lower base  22  also has a series of vertical axial ribs  82  each of which extends radially inwardly from the concave cylindrical surface of the guiding bore  80 . 
     By way of illustration, and as can be seen in particular in  FIG.  9   , the ribs  82  are eight in number and comprise two pairs of upper and lower ribs and two transversely opposed lateral ribs. 
     Each rib  82  is bounded axially upwards by an upper radial end facet  84  which is coplanar with face  49 . 
     Thus, in the sense of the invention, the eight facets  84  are stop facets each constituting a portion of a horizontal stop face which is oriented vertically upwards for axial downward support of the return spring. 
     The lower cavity  48  of the lower base  22  further has four recesses  86  arranged at a ninety-degree angle. 
     The upper actuating rod  24  includes a plastic moulding having a hollow tubular body  90  which is bounded by an inner concave cylindrical wall  92  and a convex cylindrical side wall  94 . 
     At its upper end, the body  90  extends into an upper cylindrical radial plate  96  which is received in the housing  72  and which has an angular indexing notch  97  in which the indexing finger  74  of the actuating cover  26  is received. 
     Inside the tubular body  90 , the upper actuating rod  24  has two diametral plates  98  and  100  which are suitable for acting on electrical contact elements. 
     In the example shown in the figures, it is the diameter plate  98  which is adapted to cooperate with the two electrical contact blades  32  and  34  to move them longitudinally away from each other in order to interrupt the electrical switching way with which they are associated. 
     Thus, considering the rest position illustrated in  FIG.  2   , an axial downward displacement of the plate  98  causes an opening of the electrical contact constituted by the two electrical contact elements  32  and  34  on which it acts by elastically deforming them to move them away from each other. 
     Such actuation is obtained by acting on the upper actuating cover  26  which pushes axially on the upper radial plate  96  of the upper actuation rod  24  to move the latter axially downwards relative to the lower base  22  and thus relative to the electrical contact elements  32  and  34 . 
     The side wall  94  of the upper actuating rod  24  extends axially from the lower annular radial face  102  of the radial plate  96  to the lower axial annular end radial face  104 . 
     The side wall  94  of the upper actuating rod  24  has an internal radial groove  106  which is bounded by a convex cylindrical bottom wall  108 . 
     The groove  106  is delimited axially upwards by a frustoconical upper radial shoulder  110 , the apex of which is oriented downwards and which constitutes a connecting ramp between the bottom wall  108  of the radial groove  106  and the convex side wall  94  of the upper actuating rod  24 . 
     The groove  106  is bounded axially upwards by a lower radial shoulder  112  which is bounded axially by an axially upward facing radial face  114 . 
     In accordance with the teachings of the invention, the side wall  94  of the upper actuating rod  24  has a series of vertical axial grooves  116  each of which extends radially inwardly from the surface of the convex cylindrical side wall  94 . 
     The profile of the bottom wall  118  of each axial groove  116  is here common to the convex cylindrical profile of the bottom wall  108  of the radial groove  106 . 
     Each axial groove  116  opens axially downwards into the annular radial lower axial end face  104 . 
     The number, dimensions, and angular distribution of the axial grooves  116  are identical and complementary to those of the axial ribs  82  of the lower base  22 . 
     Thus, as can be seen in particular in  FIG.  9   , in the assembled position in which the side wall  94  of the upper actuating rod  24  is received and axially slidably guided in the guiding bore  80 , each axial rib  82  is axially slidably received in a complementary axial groove  116  of the upper actuating rod  24 . 
     The return spring  28  is a helical compression spring, also known as a coil spring, whose circular cylindrical body is penetrated by the upper actuating rod  24 . 
     The upper end spiral  120  is here of generally circular shape and is axially supported against the lower annular radial face  102  of the radial plate  96 . 
     The lower end turn  122 , also known as the last turn or coil of the return spring  28 , is here generally triangular in shape and is axially abutting the axially upwardly facing radial face  114  of the lower radial shoulder  112 . 
     Thus, as can be seen for example in  FIG.  6   , when assembling the spring to the actuating rod, the return spring is mounted slightly axially compressed without play between the opposing radial faces  102  and  114 . 
     In this initial state of the return spring  28 , and as can also be seen in  FIGS.  2  and  3   , the last turn  122  is arranged in the recess in the side wall  94  of the upper actuating rod  24  constituted by which the radial groove  106 . 
     The average internal diameter of the last turn is reduced relative to the internal diameter of the other turns so as to be adjacent to the convex cylindrical side wall of the radial groove  106 . In this way, the turn  122  is axially supported on the facets  84  and the tactile sensation during actuation is optimized. 
     In the upper rest position of the upper actuating rod  24 , the last turn  122  is in downward axial abutment against the radial face  49  of the lower base  22  and the spring  28  exerts a elastic upward return force on the upper actuating rod  24 , this upper rest position being determined by the upward axial abutment of the hooks  66  against the upper bottom  61  of the axial grooves  60 . 
     As can be seen in detail in  FIG.  9   , different sections of the last turn  122  of the return spring  28  are in axial abutment against a facet  84  of an axial rib  82  or extend opposite a facet  84  of an axial rib  82 . In each case, the facet  84  thus may be considered to be a stop surface or abutment surface of the housing 
     Thus, when the switch is actuated and the upper actuating rod  24  is pushed axially downwards against the elastic return force applied to it by the spring  28 , the last turn  122  is supported axially on the facets  84  without any risk of this turn  122  becoming jammed between the upper actuating rod  24  and the lower base  22 , even when the last turn  122  cooperates with the cam profile constituted by the frustoconical ramp  110 . 
     Second Example Embodiment 
     The second embodiment shown in  FIG.  10    is similar to that shown in  FIG.  9   , except that the last turn  122  of the return spring  28  is generally circular in shape. Otherwise, as with the first embodiment shown in  FIG.  9   , the abutment facet  84  of axial rib  82 , as well as the guiding bore  80 . vertical axial grooves  116 , lower base  22  and other elements of the switch, are arranged as they are in the first embodiment of  FIGS.  1 - 9   . 
     Thus, when the switch is actuated and the upper actuating rod  24  is pushed axially downwards against the elastic return force applied to it by the spring  28 , the last turn  122  is supported axially on the facets  84  without any risk of this turn  122  becoming jammed between the upper actuating rod  24  and the lower base  22 , even when the last turn  122  cooperates with the cam profile constituted by the frustoconical ramp  110 . 
     The features and functions described above, as well as alternatives, may be combined into many other different systems or applications. Various alternatives, modifications, variations or improvements may be made by those skilled in the art, each of which is also intended to be encompassed by the disclosed embodiments.