Abstract:
A push button switch includes: a support structure of a generally box-like shape, defining an internal space, the support structure having at least an opening communicating with the internal space and an opening axis, the opening being defined by an internal opening edge; an actuation mechanism having a push button and a mechanical coupling arrangement for connecting the push button to the support structure, the mechanical coupling arrangement having a guiding arrangement for the push button to traverse with respect to the support structure in a direction generally parallel to the opening axis; a key which is fixable to the push button for manually actuating the push button; and an anti-jamming protection device having a protective plug interposable between the key and push button and being appliable onto the support structure for interacting with the internal edge, to protect the guiding arrangement from undesired intrusion by dust particles and such.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention refers to electric switches, and more particularly to a push button switch. 
       BACKGROUND INFORMATION 
       [0002]    A push button switch  1  of this type, as illustrated in  FIG. 1  and discussed for example in published international patent application WO 2006/1065554, includes a support structure  2 , or casing, of insulating material, having a generally box-like shape and defining an internal space for housing and supporting the electro-mechanical components of the switch. The support structure  2  has an opening  3 , through which the internal space is connected to the outside of the support structure  2 . 
         [0003]    The push button switch  1  moreover includes an actuation mechanism  4 , having a push button  5 , which may be coupled with the support structure  2  for closing its opening  3 . The actuation mechanism  4  also includes a coupling arrangement  6  for coupling the push button  5  to the support structure  2  in order to allow a relative guided sliding movement of push button  5  with respect to support structure  2 . The sliding is required for controlling, by push button  5 , an electrical switching of switch  21 , which is performed, in practice, by rotating an oscillating switching member  10 , for establishing/interrupting electrical connections by interacting with fixed electrical contact elements housed in the box-like structure  2 , not shown in  FIG. 1 . In particular, the actuation mechanism  4  includes a pressure transmission arrangement  7 , a rotating block  8  and a spring loaded pin  9  adapted to cooperate with the oscillating switching member  10 . 
         [0004]    The push button  5  includes a front portion provided by a key  11 , and the switch  1  includes a key cover  12  which may be associated with the key  11 . 
         [0005]    In order to avoid possible jamming of push button  5  in the box-like structure  2 , which is likely in particular when the push button  5  is for example subject to a manually exerted pressing force in a position which is distinct from a generally central portion of push button  5 , in the above international patent application WO 2006/106554, a solution has been proposed, in which the coupling arrangement  6  is provided, which are disposed between the push button  5  and the box-like structure  2 , comprising a retaining and guiding frame  6  for push button  5 , which may be fixed to the support structure  2 , by two small hooks  13 , and which may be interposed between the push button  5  and the support structure  2 . 
         [0006]    The applicant, based on field tests, has observed that in particular when tolerances between the push button  5  and retaining and guiding frame  6  are relatively small, for example, but not exclusively, as described in the international patent application WO 2006/106554, wherein the push button  5  and frame  6  form a directly assembled cinematic system, a undesirable intrusion of dust or sand particles and construction materials and similar may occur in the sliding areas defined between the push button  5  and retaining and guiding frame  6 . 
         [0007]    Such undesirable intrusion may in some case inhibit the sliding of push button  5  with respect to the retaining and guiding frame  6 , therefore causing the actuation mechanism  4  to jam. 
         [0008]    An object of the exemplary embodiments and/or exemplary methods of the present invention is to provide a switch with a push button actuation system, which is such as to solve the above problem with reference to the switches of the known art. 
         [0009]    This object is achieved by a push button switch, as generally defined herein. Exemplary and advantageous embodiments of the present invention are also further defined herein. 
         [0010]    The exemplary embodiments and/or exemplary methods of the present invention may be better understood from the following detailed description of a particular illustrative and therefore non-limiting embodiment, with reference to the appended drawings. In the drawings, same or like elements are indicated by the same reference numerals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a perspective exploded view of a push button switch according to the prior art. 
           [0012]      FIG. 2  shows a perspective exploded view of a push button switch according to the present invention. 
           [0013]      FIG. 3  shows in greater detail some of the parts of switch of  FIG. 2 . 
           [0014]      FIG. 4  shows a lateral sectional view of the push button switch of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Referring to  FIGS. 2 ,  3  and  4 , a particular exemplary embodiment of a push button switch according to the present invention is shown, which is generally indicated by  21 . This switch may be of the modular type, i.e. it is to be installed in a support frame for wall mounting, beside other switches of the same type, or generally beside other electrical modular apparatus, such as electrical sockets. 
         [0016]    In the exemplary embodiments and/or exemplary methods of the present invention, by switch a single contact opening and closing device as well as an opening contact device with simultaneous closing of another contact and vice versa (diverter) are intended. 
         [0017]    The switch  21 , shown in  FIG. 2  with partially separated parts, comprises a support structure  22  of insulating material, for instance plastic, having, in an exemplary and non-limiting way, approximately a parallelepiped shape with four lateral walls and a bottom wall. 
         [0018]    The support structure  22 , defines within lateral walls and a bottom wall an internal space communicating through a front opening  23  with the outside of the support structure  22 . As shown in  FIG. 4 , the front opening  23  is provided with an opening axis Z-Z and is bounded by an inner edge  23   a  of the support structure  22 . 
         [0019]    In the internal space of the box-like structure  22  three electrical connection terminals  41 ,  42  and  43  are housed. Two of such terminals  41 ,  42  have a respective fixed contact  44  whereas the third terminal  43  carries a pivot  45 , which in the example shown is formed by a conductive bar having an L shaped section. 
         [0020]    In the described example, the push button switch  21  also includes a diaphragm  28  and an oscillating switching member  10  for establishing electrical connections, which in the particular example are provided by a rotatable metal bridge  10 . In the example described, the rotatable bridge  10  is a rocker with a central rounded profile, which is positioned in the internal space of support structure  22 . The rotatable bridge  10  comprises an abutting central portion  10 . 3 , which through an opening  29  formed in the diaphragm  28  contacts the pivot  45 , and also comprises two arms having mobile electrical contacts  10 . 1 ,  10 . 2  at the respective ends. The bridge  10  is such as to be rotated about its central abutting portion, in order to establish/interrupt electrical connections. 
         [0021]    The push button switch  21  further comprises an actuation mechanism  24  which may be coupled to the support structure  22 . 
         [0022]    The actuation mechanism  24  comprises a push button  25  and a mechanical coupling arrangement  26  for coupling the push button  25  to the support structure  22  in order to fix the push button  25  to the support structure  22 . The mechanical coupling arrangement includes a guiding arrangement  26  for allowing the push button  25  to move with respect to the support structure  22  in a direction which is substantially parallel to the opening axis Z-Z. In a particularly advantageous embodiment, the guiding arrangement advantageously includes a retaining and guiding frame  26  for push button  25 . The retaining and guiding frame  26  may be fixed, in an exemplary and non-limiting way, by clamping to the support structure  22 . The retaining and guiding frame  26  may be inserted into the front opening  3  for being at least partially received inside the internal space of support structure  22 . In a particularly advantageous embodiment, the retaining and guiding frame  26  is totally received in the internal space of support structure  22 . The retaining and guiding frame  26  may be made according to already cited international patent application WO 2006/106554. 
         [0023]    The push button  25  may include an upper portion having a plate  25 . 1  and may also include a lower portion formed by lateral push button walls  25   a ,  25   b ,  25   c ,  25   d , which perpendicularly protrude from plate  25 . 1 . 
         [0024]    Advantageously, the retaining and guiding frame  26  comprises lateral walls  26   a ,  26   b ,  26   c ,  26   d  which annularly surround the push button  25 , in order to envelope the lower portion  25   a ,  25   b ,  25   c ,  25   d  of push button  25 . In a particularly advantageous embodiment, the lateral walls of frame  26   a ,  26   b ,  26   c ,  26   d  on the side directed towards the push button  25  have surfaces, provided with protrusions and recesses, which are substantially counter-shaped with respect to corresponding surfaces of lateral walls  25   a ,  25   b ,  25   c ,  25   d  of the push button, which face the retaining and guiding frame  26 . In practice, protrusions of lateral frame walls  26   a ,  26   b ,  26   c ,  26   d  are received in corresponding recesses of push button walls  25   a ,  25   b ,  25   c ,  25   d  and vice versa, in order to define a plurality of guides provided in the thickness of lateral walls of frame  26  and push button  25 . 
         [0025]    Advantageously, the push button  25 , due to the interaction of lateral push button walls  25   a ,  25   b ,  25   c ,  25   d  with lateral frame walls  26   a ,  26   b ,  26   c ,  26   d , is slidingly constrained by the retaining and guiding frame  26  in order to traverse in a guided way with respect to the same, in a direction which is substantially parallel to opening axis Z-Z. In particular, the push button  25  may traverse, sliding in the retaining and guiding frame  26 , along a path between a first end position, in which, as shown in  FIG. 3 , the push button  25  is in a distal position with respect to frame  26  and a second end position (not shown), in which the push button  25  is in a proximal position with respect to frame  26 . 
         [0026]    In a particularly convenient embodiment, the push button  25  and guiding frame  26  form a directly assembled cinematic system which comprises two almost irreversibly coupled elements  25 ,  26 , i.e. which cannot be easily separated from each other without structurally damaging these elements. For example, push button  25  and retaining and guiding frame  26  are composed of two distinct chemically non adhesive materials, by a co-molding technique comprising two sequential successive accretions. Such a co-molding technique is described, for example, in the European patent application number EP 1386716. 
         [0027]    In a particularly advantageous embodiment, at least two lateral mutually opposed push button walls  25   a ,  25   b ,  25   c ,  25   d  comprise protruding end-stop elements  25 . 3 , which project from push button lateral walls towards corresponding lateral frame walls. In the thickness of the lateral frame walls pockets (i.e. blind cavities) or windows (i.e. through openings)  26 . 3  are provided, which receive the protruding end-stop elements  25 . 3 . In  FIG. 3 , two openings  26 . 3  are partially visible, which are formed in the lateral wall  26   a  of frame  26 . Corresponding openings are provided in the wall  26   c  of frame  26 . 
         [0028]    The push button switch  21  further includes an elastic pushing arrangement  14  for retaining the push button  25  in its distal position with respect to guiding frame  26 , i.e. in a distal position with respect to support structure  22 . This distal position represents the rest position of push button  25 . In the example described, the elastic pushing arrangement includes, without any limitation, two helical pressure springs  14 , with respective second ends abutting against a surface of plate  25 . 1  which is directed towards the internal space of supporting structure  22 . 
         [0029]    As shown in  FIG. 2 , the actuation mechanism  24  may include a control element  8 ,  9  having a block  8  of insulating material and a spring-loaded pin  9 , and may also have a pressure transmission arrangement  7 . Without any limitation, the above mentioned components  7 ,  8  and  9  may be structurally realized and functionally operative according to European patent EP 1 584 096 and/or international patent application WO 2006/106554. 
         [0030]    The push button  21  also includes a key  31 , or counter-button, which may be fixed to push button  25  for manually actuating the same. The switch  21  may also include a key cover  12 , which may be coupled to key  31  for aesthetic reasons. 
         [0031]    The push button switch  21  further includes an anti-jamming protection device  33 , having a protective plug, which may be interposed between the push button  25  and key  31  and which can be coupled to support structure  22  for protecting the guiding arrangement  26  from undesirable intrusion of dust particles and similar. 
         [0032]    The protective plug  33  may be applied on the support structure  22  at the front opening  3  of same, and is advantageously fixable to support structure  22  for cooperating with the internal edge  23   a  of support structure  22  surrounding the front opening  3 . In other words, an external peripheral edge  33   a  of protective plug  33  is such as to cooperate with the internal edge  23   a  of front opening  3 . In this way, the protective plug  33  passes through the opening  23  and is at least partially received in the internal space of support structure  22 . This advantageously allows a limitation of size, i.e. avoids a substantial increase in size with respect to a switch without the anti-jamming protection device  33 . 
         [0033]    This solution also advantageously does not interfere with a modular installation of switch, since it does not substantially increase the modular size (height, width) of switch. 
         [0034]    In a particularly advantageous embodiment, the protective plug  33  includes a relatively rigid portion  34 , having an arrangement  36  for fixing the plug  33  to the box-like structure  22 , and a relatively flexible portion  35 , which may be an elastic membrane, which is integral with the relatively rigid portion  34  and is internal with respect to the latter, the two portions being made of different materials with different flexibility characteristics. Without any limitation, the relatively rigid portion may be made of polypropylene reinforced by glass fibers whereas the relatively flexible portion  35  is made of a thermoplastic elastomer SEBS (Styrene-Ethylene-Butadiene-Styrene). 
         [0035]    It is to be noted that according to the particularly advantageous embodiment, which is shown in the figures, the relatively rigid portion is provided by a frame which completely surrounds the relatively elastic portion  35 . As in the example shown, in a plan view, the latter may be “C”-shaped or “U”-shaped. 
         [0036]    In the example shown, the relatively rigid portion  34  comprises two opposed protruding teeth  36  for clamping the protective plug  33  to the box-like structure  42  by respective metal flaps  13 . Such metal flaps  13  may also hook the switch  21  to a mounting frame (not shown). 
         [0037]    In a particularly advantageous embodiment, the protective plug  33  is a one-piece solid device, wherein the relatively rigid portion  34  and the relatively flexible portion  35  are fabricated by a co-molding technique using two chemically adhering materials. 
         [0038]    The protective plug  33  may be provided with at least a through opening  35 . 2  through which fixing arrangements  31 . 1 ,  25 . 2  may pass, which are provided for fixing the key  31  to push button  25 . In the described example, in particular, two openings  35 . 2  are provided, which are formed in the relatively flexible wall  35  and the fixing arrangement for fixing key  31  to push button  25  comprise a pair of pins  25 . 2  provided on push button  25  and a pair of bushings  31 . 1  provided on key  31  for receiving a respective pin  25 . 2  of push button  25 . As may be seen in  FIG. 4 , a respective pin  25 . 2  passes through each of the two openings  35 . 2 . 
         [0039]    In a particularly advantageous embodiment, the relatively flexible portion  35  of protective plug  33  comprises a sealing edge  35 . 1  surrounding the plug opening  35 . 2 , and which deforms in order to follow the push button movements. In particular, in the described example two sealing edges  35 . 1  are provided, each with a substantially wavy profile associated to a respective opening  35 . 2 . In a particularly advantageous embodiment it is also possible to provide, as shown in  FIG. 4 , sealing edges  35 . 1  which are internally clamped between the key  31  and push button  25 . 
         [0040]    From the above description it is possible to understand that the switch according to the invention fully accomplishes the required task. It is in fact to be noted that the provision of a protective plug of the above type advantageously allows avoiding undesirable intrusions of dust and similar material inside the sliding areas and therefore avoiding the jamming problem of above push button switch of the known art. 
         [0041]    The skilled in the art, in order to satisfy contingent and specific needs, may introduce numerous modifications and variants to the above push button switch, all contained in the protection scope of the present invention.