Patent Publication Number: US-6222140-B1

Title: Miniature momentary contact sliding switch

Description:
This is a continuation application of U.S. application Ser. No. 09/158,796 filed on Sep. 23, 1998 and now U.S. Pat. No. 6,091,037 which is a divisional application of application Ser. No. 08/898,958 filed on Jul. 23, 1997, and now allowed as U.S. Pat. No. 5,871,086. U.S. application Ser. No. 09/158,796 is also a continuing application of U.S. patent application Ser. No. 09/122,721 filed Jul. 27, 1998 which is a continuation application of U.S. patent application Ser. No. 08/685,609 filed on Jul. 24, 1996, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to switches for electronic and electrical apparatus and, more particularly, to miniature switches which are suitable for retrofitting electrical and electronic apparatus to other devices and controlling the electrical or electronic apparatus in conjunction therewith. 
     2. Description of the Prior Art 
     Control must be exercised over virtually all electronic or electrical apparatus in order to derive desired functions therefrom. To exercise such control, some device must provide an interface between the apparatus and some external agency such as a condition sensor or, much more often, a human operator. It is sometimes the case that control of a device will be desired in conjunction with operation or control of some other apparatus or system with which the device otherwise cooperates only minimally, if at all. In such a case, either operation or the control of the other apparatus or system must be sensed and converted to an electrical signal suitable for exercising the desired control of the device. 
     For example, it is known to sense current in one circuit and to control application of power to the another circuit. Thus, as applied in a commercially available power strip to an installation of a personal computer or audio system, the usually accessible power connection to, say, the monitor or the printer of a personal computer or the pre-amplifier, tuner or other component of an audio system, may be used to remotely control application of power to other components of the system where the individual switches therefor are not necessarily accessible or where the convenience of a single power switch for all system components is desired. 
     In other arrangements which involve separated but similar power sources such as in multi-pole circuit breakers or switches, a simple mechanical interlock between similar switch structures may be sufficient to commonly control separate circuits. In contrast, complex proximity sensing circuits (e.g. capacitive or radiant energy sensors) or signals representing changes in any of a number of different control functions of a device may be used in conjunction with knobs or keypads to provide an additional control function for the same or another device. For example, in some consumer electronics devices such as a car radio, adjustment of any control (e.g. volume) will cause temporary display of alternative data (e.g. tuner frequency rather than time) on a display. However, unless some structural or functional similarity or cooperation can be exploited, auxiliary switching or sensor arrangements are generally bulky, complicated, expensive and/or difficult to retrofit to existing apparatus or systems. 
     It has recently been proposed to provide a voice recording device in an electrical wall switch plate, such as is disclosed and claimed in co-pending U.S. patent application Ser. No. 08/685,609, filed Jul. 24, 1996 (now abandoned), of which the present inventor is a joint inventor and which application is hereby fully incorporated by reference as if the text thereof were fully set forth herein. In this combination, it is contemplated that the actuation of the wall switch should cause the playback of an audio message of one or more messages (possibly of a sequence of messages) that may be recorded at will, preferably by recording samples of the message in random access memory or other solid state memories. 
     Such recordation has been facilitated by recent reductions in cost of relatively large capacity semiconductor memories and integrated circuits capable of conversion of analog signals to digital signals and vice-versa. Thus, it is possible to provide the necessary electronics, including a speaker, microphone and battery power supply within a wall switch plate cover with only a relatively modest increase in the thickness thereof (e.g. about a {fraction (7/16)} inch overall thickness, increasing thickness over a conventional switch plate generally by less than ¼ inch). 
     Incidentally, at the current state of design of this device, it is preferred to activate the playback function by a brief signal pulse with automatic reset of the playback circuit when the message playback is complete. Thus the preferred function of sensing actuation of the wall switch differs widely from the function of the wall switch itself or the circuit to which it is connected. Further, it is considered desirable to be able to distinguish between directions of actuation to provide different messages for each wall switch state or to control a sequence of messages. Sensing of circuit conditions may also be complicated by so-called three-way or four-way switch connections which may allow a circuit to be controlled from multiple locations potentially remote from the playback device. 
     However, providing sensing of operation of a wall switch as desired for this application within a switch plate cover is not trivial. The existing wall switch provides the mounting arrangement for the switch plate and conventional switch plates are designed to be drawn tightly against the body of the wall switch with virtually the entirety of the actuating lever of the wall switch protruding therethrough. Of course, external mechanisms would be unsightly and potentially dangerous. 
     Current sensing in the controlled circuit is less than fully reliable due to possible variation or disconnection of the load controlled by the switch and, in any event, it is desirable for purposes of simplicity and safety of installation of the device to retrofit it to an existing wiring system without disturbance of existing wiring in any way. Prevailing electrical codes may prohibit and restrict any incursion of any portion of the device or its circuitry into an existing electrical wiring box. 
     The need for linking of a switch or other structure to an existing electrical switch within a small volume is not limited to the device disclosed in the above-incorporated application. While many arrangements for operationally linking switches and electrical circuits are known, none are suitable for providing sensing of actuation and/or direction of actuation within a small thickness and within a wall switch cover plate with only a marginal increase in thickness thereof. Further, the required thinness of a switch may limit its ability to withstand thousands of actuations of the switch to which is to be connected. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a very thin but mechanically robust switch and linkage suitable for simple connection to the actuating lever of an existing electrical switch such as a wall switch and without requirement for modification of the existing electrical switch or contact with existing wiring. 
     It is another object of the invention to provide a momentary contact switch for sensing an intermediate location of an actuating lever of another switch. 
     It is a further object of the invention to provide a mechanically robust switch and linkage capable of sensing a direction of movement of an actuating lever of another switch at an intermediate location thereof between normal switch actuation positions. 
     In order to accomplish these and other objects of the invention, a momentary contact switch is provided comprising a support structure, a sliding plate having an aperture to engage an actuating lever of an electrical switch and slidable along a locus relative to the support structure, and an arrangement moveable with the sliding plate to control movement of a first electrical contact against a second electrical contact at a position intermediate between two extreme positions of said sliding plate. 
     In accordance with another aspect of the invention, a method of retrofitting apparatus such as a voice recording and playback apparatus to an electrical switch is provided comprising the steps of placing an aperture in a plate slidable relative to a support structure over an actuating lever of the electrical switch, attaching the support structure to the electrical switch, controlling movement of electrical contacts with the plate in accordance with the relative position of the plate and the support structure, and controlling the apparatus with said electrical contacts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which: 
     FIG. 1 is a plan view of the front of a wall switch plate including a preferred recording and playback device and a switch in accordance with the invention, 
     FIG. 2A is a plan view of the back of a wall switch plate including a preferred recording and playback device and a switch in accordance with the invention, 
     FIGS. 2B and 2C are plan and side views of a preferred form of the switch in accordance with the invention, 
     FIG. 3 is a perspective view of a preferred form of the switch and wall plate in accordance with the invention with recording and playback circuits removed, 
     FIG. 4 is a perspective view of a variant form of the switch of FIG. 2A including provision for sensing direction of motion of an actuating lever of a switch to which it is connected, 
     FIG. 5 is a plan view of the variant form of the invention shown in FIG. 4, 
     FIG. 6 is a plan view of a form of the invention functionally corresponding to FIG.  3  and employing a cam, 
     FIG. 7 is a plan view of a modified form of the switch of FIG. 6, and 
     FIG. 8 is a plan view of a form of the invention functionally corresponding to FIG.  3  and employing a cam. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     Referring now to the drawings, and more particularly to FIG. 1, there is shown, in plan view, the front of a wall switch cover plate  10  including a voice recorder in accordance with a preferred application of the invention. The switch plate includes an aperture  11 , preferably tapered or bevelled about the periphery thereof through which an actuating lever of an existing conventional wall switch (not shown) may protrude, passing through a portion of a sliding plate  12  supported by cover plate  10  with an aperture  12 ′ therein which thus engages the actuating lever of the existing wall switch, schematically illustrated and indicated by the same reference numeral. Apertures  14  are provided for mounting the wall switch cover plate  10  to the existing wall switch in the conventional fashion. To conceal the slightly increased thickness of the cover plate and provide an aesthetically pleasing appearance as well as efficiently housing conventionally shaped batteries therein, the edges thereof are preferably bevelled or rounded as shown at  15  in a manner not at all critical to the practice of the present invention. 
     An opening  16  is preferably provided to facilitate acoustic coupling to a miniature microphone placed behind it. The opening can be formed in a manner to resemble the head of a mounting screw, as illustrated, if desired. Further apertures  18  are provided as a grille for a miniature speaker which can be mounted behind it and a button  20 , which can also be made to resemble a head of a mounting screw, is also provided to control the recording function. 
     Referring now to FIG. 2A, the back side of the wall switch cover plate  10  is shown in plan view. Mounting arrangements for the electronics board ( 22 ), microphone ( 23 ), speaker ( 24 ) and batteries ( 25 ) are preferably provided as molded bosses but are not critical to the practice of the invention. In the same manner, stand-off bosses  26  are provided to accommodate the thickness of sliding plate  12  and to provide bearing surfaces therefor. Accordingly, when the actuating lever of an existing wall switch engages aperture  12 ′ in sliding plate  12 , cut-outs  27  bear against bosses  26  to constrain movement of sliding plate  12  along a preferably linear locus. Additionally, the sliding plate  12  is assembled to the cover plate  10  with a screw, washer and insulating bearing washer (all generally indicated at  28 ) through slot  28 ′. The insulating washer serves to retain contact plate  29  in position against the cover plate and positioned by preferably molded bosses  29 ′. It should be understood that that contact plate could also be a fixed contact mounted as part of a switch including moveable contact  31 . Electrical connection to contact plate or fixed contact  29  may be made in any desired manner, conveniently in the same direction and under contact  31  as illustrated in FIG.  2 A. Alternatively, adhesive or other expedients may be used to attach the contact plate  29  in place. 
     Sliding plate  12  also carries a switch mask portion  30 , also shown in FIG.  2 B. It should be appreciated that the position of sliding plate  12  depicted in FIG. 2A relative to cover plate  10  (and in FIG. 2B relative to bosses  26 ) corresponds to an intermediate position of the existing wall switch with which it is intended to cooperate. Therefore, the actuated or operative positions of the existing wall switch bring sliding plate  12  to one of the extreme positions indicated by dashed lines  12 A or  12 B. 
     The switch in accordance with the invention is formed by contact plate  29 , shown in FIGS. 2A and 2C and a conductive contact  31  shown in all of FIGS. 2A-2C, preferably of a cantilevered form illustrated but not critical to the invention. It should be further appreciated that a further aperture  32  in sliding plate  12  allows contact between contact  31  and contact plate  12  when sliding plate  12  is in the intermediate position between operative positions of the actuating lever of the existing switch. In either of these operative positions of the existing switch, aperture  32  is moved to either position  32 A or  32 B (corresponding to the extreme positions  12 A and  12 B, respectively, of the sliding plate  12 ) and the mask portion  30  of sliding plate  12  thus serves to insulate contact  31  from contact plate  29 . Accordingly, as perhaps more clearly shown in FIG. 3, the switch formed by sliding plate  12  and contacts  29  and  31  provides a momentary contact as the actuating lever of the existing switch is moved between operative positions. 
     It should further be appreciated that sliding plate  12  has robust bearing surfaces  26 ′ which bear against bosses  26  and the separation between them is long in comparison with the separation of mask portion  30  from the axis between them. Therefore, the sliding plate mechanism  12  is not susceptible to binding. Likewise, mask portion  30  can bear directly against contact plate  29  and be supported thereby as it is driven between contact  31  and the contact plate  29 . The edges of aperture  32  can be bevelled, if desired, to assist in the ease with which contact  31  can be separated from contact plate  29  and preferably works against only the small force exerted by the relatively long cantilever of contact  31  (which is, of course sufficiently long that only elastic deformation of the cantilever will occur over the small thickness of sliding plate  12 ). Therefore, the switch of FIGS. 1-3 is extremely reliable and robust and need be no thicker than the contact plate  29  (which could, in theory be formed by a foil or a plated layer), the small thickness of sliding plate  12 , and enough curvature or other shaping in cantilever  31  to accommodate that small thickness. In essence, the total required thickness of the switch is only twice the thickness of the sliding plate  12  plus the thickness of contact  31 . It should be noted in this regard that the relatively wide areas of the mask portion  30  of sliding plate  12  provide a substantial degree of stiffness to resist deformation around the aperture  32  even if sliding plate  12  is very thin and of a relatively flexible material. 
     From the foregoing, it is seen that the preferred form of the invention provides a mechanically reliable and robust basic momentary contact switch design of minimal thickness which can be refined in many ways by those skilled in the art in view of this description thereof. Bearing surfaces can be provided by readily available insulative and abrasion-resistant materials which will provide a long serviceable lifetime under the extremely light loads inherent in the design are readily available. Additionally, lubrication can be provided and renewed from time to time at bosses  26  and contact plate  29 . It should also be noted that the only moving part of the switch other than the slight elastic deformation of the contact  31  is slidable plate  12  which is inexpensive and could be easily renewed since it is held in position over bosses  26  only by a single screw  28 . 
     A preferred variant form of the invention which can provide discrimination of direction of motion of the existing switch actuating lever can best be understood from a comparison of FIG. 4 with the similar view shown in FIG. 3 discussed above. In this variant form of the invention, contact plate  29 , contact  31  and aperture  32  in sliding plate  12  are functionally identical to the embodiment of FIG. 3 although the size, form and placement thereof may be varied to accommodate additional contacts  41  and  42 . 
     It will be recalled from the foregoing that the recording and playback device  22  of the preferred application of the invention is arranged to begin operation in response to a momentary pulse and resets itself for another operation when an operation is complete. Therefore, the recording and playback device  22  will not respond to a further pulse during an operation. While the preferred configuration of the variant form of the invention illustrated in FIG. 4 exploits this function of recording and playback device  22  so that only the first of two momentary contacts is recognized, other mechanical configurations or electrical logic circuitry provided to achieve a the same or other desired function. 
     For example, while the embodiment illustrated in FIG. 4 has contacts  41  and  42  placed such that all of contacts  31 ,  41  and  42  are separated from contact plate  29  in either extreme position of sliding plate  12 , contacts  41  and  42  could be more widely separated to be in contact with contact plate  29  at an extreme position of sliding plate  12  and, for example, a capacitor charging circuit connected to each of contacts  41  and  42  such that a respective capacitor will be discharged through contact  31  as sliding plate  12  moves through the intermediate position and while both contacts  41  and  42  are separated from contact plate  12 . Alternatively, only contacts  41  and  42  need be provided in combination with an electrical connection to contact plate  29  to provide an input to a logic circuit which can similarly discriminate which of contacts  41  and  42  contacts contact plate  29  earlier or later than the other. 
     In this way, only one pulse will be produced for each movement of sliding plate  12  but different directions of movement will produce that pulse at a different node of the circuit and can thus be discriminated. It will be appreciated from the foregoing that other functions could also be achieved by providing additional or differently shaped apertures  32  in mask portion  30  of sliding plate  12  as well as additional switch poles and may be found desirable or convenient. 
     Referring now to the plan view of the variant form of the invention of FIG. 4 shown in FIG. 5, the direction discriminating function thereof will now be explained. In either extreme position  12 A or  12 B of sliding plate  12  aperture  32  will be at locations  32 A or  32 B respectively, at which all contacts  31 ,  41  and  42  will be separated from the contact plate  29  by the interposition of the mask portion  30  of sliding plate  12 . In a central intermediate position, depicted in solid lines, only contact  31  will be in contact with contact plate  29  and contacts  41  and  42  will be separated from the contact plate  29  by the edge of aperture  32 . 
     Between each extreme position  12 A,  12 B, and the central intermediate position there will be a position indicated by bracket  51  of sliding plate  12  at which two contacts will be allowed to simultaneously be in contact with contact plate  29  while one of contacts  41  and  42  will be separated therefrom by the mask portion  30  of the sliding plate  12 . While another such position, indicated by bracket  52 , will occur before the opposite extreme position is reached, simultaneous connection of two contacts with or through contact plate  29  will always occur before the other as the existing switch lever is moved between operative positions. Thus, the direction of movement on the existing switch lever can be readily discriminated by detection of the earlier (or later) connection of contact  41  or  42  with contact  32 . 
     As alluded to above, the embodiments of the invention illustrated in FIGS. 3 and 4 rely on elastic deformation of contacts  31 ,  41 ,  42 , (e.g. by being cantilevered) as they are separated from contact plate  29  by the mask portion  30  of sliding plate  12  such that they will return to their original shape to contact the contact plate  29  when allowed to do so by the aperture  32 . While preferred for thinness and economy of manufacture and/or repair, robustness of the switch may be enhanced by providing for positive contact movement and engagement as will now be discussed for different forms of the invention illustrated in FIGS. 6-8. It should be understood, however, that positive contact and increased robustness is achieved at a cost of the positive separation of contacts in the above-described embodiments and may require, in practical implementations, increased stiffness of contacts and consequent increase in actuation force and susceptibility to wear. However, in applications not subject to accelerations such as with a wall switch, maintaining separation may not be a problem and relatively thin resilient contacts may be employed. 
     Referring first to FIG. 6, an embodiment of the invention having a momentary contact function corresponding to that of the embodiment of FIG. 3 is shown. Essentially, the embodiment of FIG. 6 (and FIGS. 7 and 8, as well) use a cam  62  for providing positive contact instead of an aperture  32  which provides positive separation. Thus, as sliding plate  12  moves from one extreme position  12 A, shown in solid lines, to the other extreme position  12 B, shown in dashed lines, cam  62  will be brought into contact with contact  61  and urge it against contact  63  which functions in the same manner as contact plate  29  of the embodiment of FIGS. 3 and 4. 
     Similarly in FIG. 7, cam  62  momentarily bears against contact  61  to urge it against contact  63  while separating it from contact  71  as the sliding plate  12  moves between extreme positions  12 A and  12 B. It should be appreciated that the switch function of simultaneously opening one pair of contacts while closing another is readily achieved with a cam structure. The same function can also be achieved using an aperture  32  as in the embodiments of FIGS. 3 and 4 but may require additional apertures or shaping of the edges of aperture  32  to obtain the desired function, as will be evident to those skilled in the art in view of this description. 
     The embodiment of the invention shown in FIG. 8 corresponds to the switch function of the variant form of the invention shown in FIG.  4 . Specifically, in FIG. 8, sliding plate  12  is shown between an extreme position  12 A,  12 B, and a central intermediate position at which both contacts  81  (corresponding to contact  31  of FIG. 4) and  82  (corresponding to  41  of FIG. 4) are brought into contact with contact  84  (corresponding to contact plate  29  of FIG.  4 ). Similarly, in the central intermediate position, only contact  81  will be in contact with contact  84  and in an extreme position, none of contacts  81 ,  82  or  83  will contact the contact  84 . Thus, as in the embodiments of FIGS. 6 and 7, the embodiment of FIG. 8 also provides momentary contact but additionally provides for discrimination of direction of movement in the manner described above in regard to FIG.  4 . 
     It should be understood in regard to the embodiment of the invention illustrated in FIG. 8 that separate contacts  84  can be provided for any desired ones of contacts  81 - 83  as may be desired and additional contacts corresponding to contact  71  of FIG. 7 may be provided as desired. Additionally, separate cams  62  could be provided for any or all contacts  81 - 83  in the same manner that the edges of aperture  32  may be adjusted to alter switch functions or plural apertures  32  provided. 
     It should also be appreciated in regard to the embodiments of FIGS. 6-8 that the location of the cam  62  is not critical to the invention. For example, cam  62  could be provided on the front or back side of sliding plate  12 . However, such a location would result in greater switch thickness and may require other structural adjustments such as provision of bearing surfaces, additional stiffness of the sliding plate  12  and the like, as will be apparent to those skilled in the art. 
     It should also be appreciated that all of the above disclosed embodiments of the invention can accommodate differing amounts of movement of an existing switch actuating lever or other moveable structure by virtue of the momentary contact function at an intermediate location between extreme positions and thus is applicable to a wide variety of switches made by different manufacturers. Any length of movement can be accommodated by design of the length of slots  27  and  28 ′. 
     In view of the foregoing, it is seen that the invention provides a plurality of momentary contact switch functions including discrimination of direction of movement at an intermediate position in a robust switch structure which can be very thin and economically manufactured and/or repaired. The switch can be retrofitted to an actuating lever of an existing switch or other moveable structure without modification of the switch or other structure or disturbance of existing wiring to detect operation of, for example, an electrical light controlling circuit and to coordinate operation of another device such as a sound recording and playback device therewith. 
     While the invention has been described in terms of a single preferred embodiment and variations thereon, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims.