Protection device against water splashes for electric switches and the like

Abstract: The described switch comprises a casing (3) housing fixed contacts (5, 6) and a movable contact element (8) to be operated through at least one control pushbutton (9) projecting externally of a front side (10) of the casing (3) for breaking and restoring an electric continuity between the fixed contacts (5, 6). Sealingly engaged on said front side (10) is a closure wall (13) exhibiting one or more guide collars (14) over each of which the respective control pushbutton (9) is slidably and sealingly fitted. Coaxially engaged with each control pushbutton (9) is one transmission rod (15) operatively connecting the pushbutton with the movable contact element (8) for controlling the displacement thereof.

Description: The present invention relates to an electric switch including a protection device against water splashes according to the preamble of claim 1 (US-A-2040919). In the embodiment described the inventive solution is adopted on a switch of the type to be used mainly on household electrical appliances. It is however understood that the innovatory concepts proposed in the present invention can be also adopted in switches intended for uses other than the above one. It is known that electric switches and similar switching members of the above type essentially comprise an insulating casing housing at least one pair of fixed contacts each terminating at a respective pole of an electric circuit to which the switch is connected. Housed in the casing is at least one movable contact element that, through a control pushbutton manually operable from the outside, can be moved for selectively opening and closing the electric connection between said fixed contacts. The foregoing being stated, it is noted that said switches are often associated with apparatus that may accidentally operate or are conceived for use in the presence of water or in highly damp environments, as well as in the presence of other external agents particularly damaging for the correct operation of the switch. It is apparent that in the absence of appropriate expedients or protection devices, this situation involves many problems in terms of correct operation and safety. In fact, if even a small amount of water should enter the casing, making the contacts wet, inevitably electric discharges and/or shortcircuits would occur which not only can damage the electric circuit to which the switch is connected but also involve high risks for the safety of the appliance's user. In order to obviate the above drawbacks, in case of switches destined to appliances intended for use in the presence of liquids or in very damp environments, it has been hitherto provided that sealing means be associated with said switches, which means generally consists of a flexible covering element disposed such as to close the front side of the casing from which the control pushbutton projects. In greater detail, this flexibile covering element mainly made in silicone or other appropriate material, has a perimetric sealing edge engaged on said front side by an appropriate fastening frame so as to fully insulate the casing and, as a result, all components housed therein, from the surrounding atmosphere. However this solution is particularly heavy from an economic point of view above all in consideration of the reduced overall costs of the switches of the type in reference. The covering element made of silicone material actually has a high production cost to which costs for manufacturing the fastening frame must be added, as well as costs resulting from the additional time and operations required during the assembling step for the engagement of the covering element and fastening frame on the casing. It is also known from US-A-2040919 a circuit closer having a cap formed with an opening defined by a centrally upstanding flange which may terminate in an outstanding bead. A rod slidably extends through the cap opening and mounts at its upper end a head having a downwardly extending flange which snugly embraces the flange. At its lower end the rod in enlarged for engagement with the switch proper. Further it is known in the art, namely from DE-U-1790858 an electric switch with a closing top of electrically insulating material. A rod is slidable in a collar of the top in order to drive the electric contacts of the switch between an opening and a closing position. To ensure the closing of the apparatus, a sealing agent is interposed between the rod and the collar. Under this situation, the main object of the invention is substantially to solve the problems of the known art by providing a protection device against water splashes for electric switches and the like that, while ensuring a high operating reliability, can be manufactured at very reduced production costs and installed very easily. The above and still further objects that will become more apparent in the course of the present description, are substantially achieved by an electric switch including a protection device against water splashes according to claim 1. Further features and advantages will best be understood from a detailed description of a preferred embodiment of a protection device against water splashes for electric switches and the like in accordance with the present invention. This description will be given hereinafter by way of non-limiting example with reference to the accompanying drawing, in which the only figure is a part interrupted cross-sectional view of a switch embodying a device in accordance with the invention. Referring to the figure, an electric switch including a protection device against water splashes has been generally identified by reference numeral 1. The device is associated with an electric switch 2 for the purpose of inhibiting the penetration of any external agents thereinto. The switch 2 conventionally comprises a casing 3 made of electrically insulating material and intended for engagement with a shaped opening 22a provided in a support wall 22 of any electrical appliance (not shown) with which the switch is to be associated. Suitable resilient tabs 3a cooperate with a perimetric projection 3b of the casing 3 for fastening the switch 2 to the edge of the shaped opening 22a. Preferably the perimetric projection 3b is embedded in a perimetric recess 23 defined around the edges of the shaped opening 22a. An annular sealing element 24 engaged around the perimetric projection 3b acts between the projection and a locating housing 23a defined in the perimetric recess 23, so as to prevent water or other undesired substances from penetrating into the switch through the shaped opening 22a. An interconnecting device 4 operates within the casing 3 for selectively causing the opening and closure of one or more electric circuits with which the switch is associated. In greater detail, the interconnecting device 4 which is the object of an Italian Patent application filed on same date in the name of the same Applicant, comprises first and second fixed contacts, 5 and 6, rigidly carried by a base wall 7 of the casing 3 and connected to respective electric conductors, not shown as known per se and conventional. The first and second fixed contacts 5 cooperate with at least one movable contact element 8 that, upon the action of at least one control pushbutton 9 projecting externally of a front side 10 of the casing 9, can be selectively moved from an open condition to a closed condition, for breaking and restoring an electric continuity between the fixed contacts 5 and 6, respectively. More particularly, the movable contact element 8 has a linking portion 11 oscillatably engaged on the first fixed contact 5 and an interconnecting portion 12 which is moved close to and away from the second fixed contact 6 when said opening and closure conditions are respectively set. In the device in question, a sealing means is provided to be associated with the switch 2 and it operates on the front side 10 of the casing 3 for ensuring a heat insulation of said casing from the surrounding atmosphere. In accordance with the present invention, this sealing means is such structured that it defines a labyrinth path capable of preventing water droplets projected against the switch 2 from penetrating thereinto. More particularly, the sealing means comprises a closure wall 13 hermetically associated with the front side 10 of the casing 3. The closure wall 13, preferably of one piece construction with the casing 3, has at least one guide collar 14 projecting from the wall itself and slidably passed through by a transmission rod 15 operatively connecting the control pushbutton 9 to the movable contact element 8, as better specified in the following. In particular, still in accordance with the invention, the control pushbutton 9 has a bottom wall 16 engaged to one end 15a of the transmission rod 15 and a perimetric wall 17 sealingly fitted around the guide collar 14 possibly through interposition of at least one seal 18. In the embodiment shown the switch 2 with which the device 1 is associated is of the bat-handle type. In this case two control pushbuttons 9 are provided each engaged on a corresponding guide collar 14 and carrying respective transmission rods 15. The rods 15 are linked, on mutually opposite sides, to a rocking element 19 oscillatably engaged with the casing 3 by at least one central pivot pin 20. The rocking element 19 is operatively connected to the movable contact element 8 via a bistable helical spring 21 acting at the linking portion 11 of the movable contact element. The bistable spring 21, in known manner, bends with alternate motion on opposite sides with respect to an ideal median line, thereby selectively controlling the movement of the movable contact element 8 from the open condition to the closed condition and vice-versa. The bistable spring 21 acting upon the movable contact element 8 also ensures that the linking portion 11 thereof is constantly held in contact with the end of the first fixed contact 5. The present invention attains the intended purposes. The device in reference in fact enables the switch to be satisfactorily protected against water splashes without the use of sealing elements made of silicone or similar materials being required. Actually, in the known art said materials besides encountering problems as regards reliability, also involve important increases in costs due to the particular workings for manufacturing and assembling the different additional parts. Unlike the solutions of the known art, the present invention can be adopted on all kinds of switches, changover switches or the like, without practically involving any increase in the production costs. In the connection it is to note that the closure wall 13 can be easily formed during the moulding step for making the casing 3. The transmission rods 15 may also be made, if desired, unitary with the respective control pushbuttons 9 and linked to the rocking element 19 by a mere fitting action to be executed on the automated assembly lines conventionally used for making said switches. Obviously, many changes and modifications may be made to the invention as conceived without departing from the scope of the appended claims.

Claims: An electric switch including a protection device against water splashes, each switch comprising: a casing (3) made of electrically insulating material and housing fixed contacts (5, 6) and at least one movable contact element (8) selectively movable between an opening condition and a closure condition, in order to respectively break and restore an electric continuity between the fixed contacts (5, 6); at least one control pushbutton (9) projecting externally of a front side (10) of the casing (3) and manually operable for controlling the displacement of the movable contact element (8) between the closure and opening conditions; sealing means acting on the front side (10) of the casing (3) for preventing external agents from penetrating into the casing, said sealing means comprising: a closure wall sealingly associated with the front side of the casing; at least one guide collar (14) projecting externally of the closure wall (13); at least one transmission rod (15) slidably passing through the guide collar (14) for connecting the control pushbutton (9) to the movable contact element (8), said control pushbutton (9) having a bottom wall (16) engaged to one end of the transmission rod (15) and a perimetric wall (17) which is sealingly fitted around the guide collar (14), characterized int that said casing (3) in engagement with a shaped opening (22a) defined in a support wall (22), has a perimetric projection (3b) engaged in a perimetric recess (23) defined around said shaped opening (22a), at least one annular sealing element (24) being interposed between the perimetric projection (3b) and a locating housing (23a) formed in the perimetric recess (23) so that liquids cannot penetrate into the switch through the shaped opening (22a). A switch according to claim 1, characterized in that close to the closure wall (13), said sealing means defines a labyrinth path for preventing liquid from penetrating into the casing (3). A switch according to claim 1, characterized in that it further comprises at least one seal (18) operatively engaged between the perimetric wall (17) of the control pushbutton (9) and said collar (14). A switch according to claim 1, characterized in that it comprises two control pushbuttons (9) each engaged on a corresponding guide collar (14) and carrying respective transmission rods (15) that are in engagement, on mutually opposite sides, with a rocking element (19) operatively connected to the movable contact element (8) for controlling the displacement of said movable contact element between the closure and opening positions.

Inventors: CESARE GALLONE, CESARE, GALLONE
Applicants: SIGNAL LUX INTERNATIONAL S A, SIGNAL LUX INTERNATIONAL S.A.
Application year: 1993
Main classification: H01H13
IPC codes: H01H13