Abstract:
This concerns a method and kit for converting a flat panel switch to a raised panel switch by mounting a rotary switch thereto. The flat panel switch has a carrier layer. A set of electrodes forming an electrical circuit is disposed on the carrier. The kit includes a rotor having a head mounted in a front cover. A stem attached to the head extends through the front cover for actuation by a user. An electrical contact member is connected to the head for movement therewith. The contact member is associated with the electrodes to alter the condition of the electrical circuit upon actuation of the rotor. The front cover has latches that extend through perforations in the carrier for engagement with a back cover. The latches lock the front and back cover in place on the carrier.

Description:
BACKGROUND OF THE INVENTION 
     Membrane switches are well known for providing electrical switching functions in a reliable, compact package. Membrane switches typically have a flexible plastic membrane layer normally separated from a substrate by a nonconductive spacer. Openings in the spacer permit a user to push the membrane through the spacer, bringing facing electrical contacts on the internal surfaces of the membrane and substrate into contact with one another, thereby closing a switch. The natural resilience of the membrane returns the membrane to its spaced position upon removal of the actuating force. 
     While this basic membrane switch construction has many advantages, it does not provide some features desirable in certain applications. For example, in some instances switch users are so accustomed to manipulating a particular type of mechanical actuator that they become confused by a membrane switch. The membrane switch is often a flat panel with graphical elements indicating where to press but having no protruding actuating member. Although membrane switches provide perfectly adequate electrical switching, manufacturers have found that users expecting to find a rotary switch or a slide switch or a push button switch for a certain function are resistant to having the familiar mechanical actuator replaced with a flat panel membrane switch. This is especially true with consumer products. Also, in automotive applications it can be important to provide a rotary or slide switch that a driver can find and manipulate with one hand while not diverting his or her attention from the road. Another difficulty with membrane switches is they are not readily adapted for use as a potentiometer such as might be desirable for, say, a volume control on a radio or CD player. 
     Rotary and slide switches suitable for use with flat panel switches such as membrane switches are known. Examples are shown in U.S. Pat. Nos. 5,523,730, 5,666,096, and 5,867,082. One of the problems in the past has been the inability to conveniently apply such switches directly to film-based switch panels. The present invention addresses this issue. 
     SUMMARY OF THE INVENTION 
     This invention is a method and kit for converting a flat panel switch to a switch panel having discrete components thereon. Such a panel will be referred to herein as a raised panel switch. The method involves preparing a rotary switch mounting kit and applying it to a film-based flat panel switch. The flat panel switch has a carrier sheet with a set of conductors thereon forming an electrical circuit, e.g., spaced contact pads or a potentiometer, both with associated leads. The kit includes a front and a back cover which have cooperating latch members for holding the covers together on opposite sides of the carrier sheet of a flat panel switch. The latch members extend through perforations in the carrier. The front cover latches have hooks that engage notches in the back cover to clamp the pieces together on the carrier. The front cover rotatably mounts a rotor. The rotor has a head inside the front cover and a stem fixed to the head. The stem extends to the outside of the front cover where it mounts a knob which is manipulable by a user. The rotor head carries an electrically conductive contact member. The contact member is engageable with the electrical conductors to alter the state of the electrical circuit when the rotor is actuated. The contact member can be either a conductive wiper attached directly to the rotor head or a magnetically-retained armature that follows magnets mounted in the rotor. If desired a detent mechanism can be incorporated in the front cover and rotor. The carrier may be a single layer or it be one of several layers such as a flexible membrane, substrate and spacer having conventional membrane switches therein in addition to the rotary switch supplied by the kit of the present invention. Alternately, magnetically-actuated push button switches of the type described in the above patents may be incorporated in the carrier. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded, diagrammatic section of a rotary switch kit used to convert a flat panel switch to a raised panel switch according to the present invention. 
     FIG. 2 is a section of the kit of FIG. 1 after assembly. 
     FIG. 3 is a view similar to FIG. 1 showing an alternate form of the electrical contact member. 
     FIG. 4 a  is an exploded perspective view of a further alternate embodiment, showing the kit applied to a flat panel switch with magnetically-actuated push button switches. 
     FIG. 4 b  is an enlarged perspective view of the bottom of the rotor. 
     FIG. 4 c  is a further enlarged perspective view of the coupler magnets used in the switch of FIG. 1 a.    
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2 illustrate the rotary switch kit of the present invention. The kit permits conversion of a flat panel switch to a raised panel switch by means of application of a rotary switch anywhere on a flat panel switch. The flat panel switch comprises a carrier sheet  10  having first and second surfaces and a set of electrical conductors formed on one of those surfaces. The carrier sheet may be made of any material suitable for forming sheets, such as polyester, printed circuit board material or plastic-coated sheet metal. The carrier may be either rigid or flexible as the application requires. In this embodiment the electrical conductors, although not shown, would be formed on the bottom or lower surface of the carrier. The set of conductors would include suitable leads extending to an edge of the carrier or a tail extending therefrom for connection to external electronics. The carrier sheet  10  has perforations  12  through its entire thickness for accepting latch members as will be described. There is also an opening  14  for a locating pin. While the carrier sheet is shown in FIG. 1 in its most basic form, it will be understood that the carrier sheet could incorporate additional features such as conventional membrane switches, magnetically-actuated switches, slide switches and the like. Indeed, one of the benefits of the present invention is its ability to add rotary switches anywhere desired on a flat panel having these other types of devices. 
     The kit itself comprises three main components, a front cover  16 , a back cover  18  and a rotor  20 . The front and back covers are held in place on opposite sides of the carrier sheet by a latching connection between them. The rotor is mounted for rotation in the front cover. Details of each main component will now be described. 
     The front cover  16  has a rectangular or round enclosure  17  which is open on one side toward the carrier sheet. The enclosure  17  includes depending latch members  19  which terminate at hooks  22 . The underside of the enclosure defines a rotor cavity  24 . There is an opening (not shown) through the center of the enclosure. The exterior of the enclosure may have a threaded bushing  26  attached to it for the purpose of mounting the entire switch, carrier and all, in an instrument panel, circuit board or other apparatus with which the switch is used. The bushing would fit through a hole in the instrument panel and a nut would secure the front cover in place. 
     The back cover  18  has a housing  28  which may be but is not necessarily similar in shape to the enclosure  17 . The housing  28  has notches  30  sized and located to receive the hooks  22  in a snap fit therein. In this embodiment the notches are in the exterior surface of the back cover and face outwardly to receive the hooks which are arranged to fit around the external perimeter of the housing  28 . It will be understood that slots in the interior portions of the housing could be used to receive the latch members and hooks. What is important is that the latches engage the back cover so the two covers are locked together on opposite sides of the carrier to hold the covers in place. 
     Similar to the enclosure  17 , the housing  28  has a shape that defines an internal space or chamber adjacent to the carrier. In the center of this chamber there is a locating pin  32 . When the back cover is installed on the carrier the pin  32  fits through the opening  14  in the carrier. A ball retainer  34  is mounted within the chamber for rotation about the locating pin  32 . The ball retainer has a pocket  36  for receiving a ball armature set as described below. Further details of a ball retainer are described in U.S. patent application Ser. No. 09/480,606, filed on Jan. 10, 2000 and assigned to the present assignee. The disclosure of this application is incorporated herein by reference. 
     The rotor  20  has a head  38  and a stem  40 . The head is disposed in the cavity  24  of the front cover&#39;s enclosure  17 . The stem extends through the opening in the enclosure and through the bushing  26 . The head and stem are sized so as to be rotatable in the front cover. The upper surface of the head may have a slightly upraised boss engageable with a depression or seat in the underside of the enclosure  17  to center the rotor and fix its position in the front cover. A knob (not shown) may be attached to the stem to facilitate manipulation of the stem by a user. A socket  42  in the head  38  receives the locating pin  32  to further fix the relationship among the front cover, back cover and rotor. 
     A detent mechanism may optionally be included in the rotor and front cover. In this embodiment the detent mechanism includes a detent ring  43  fastened to the enclosure  17 . The internal diameter of the detent ring has a series of grooves or indentations (not shown) that receive a detent ball to define a fixed position of the rotor. A detent ball  44  and spring  46  are located in a radial bore in the head  38 . The spring urges the ball into contact with the detent ring&#39;s grooves. 
     An electrical contact member is associated with the rotor. In this embodiment the contact member comprises a coupler  48  and an armature  50 . The armature shown comprises three conductive balls held in the ball retainer pocket  36 . The coupler is a set of magnets pressed into a receptacle in the rotor head  38 . The magnetic attraction of the balls to the magnets causes them to follow the rotor head as it rotates. The balls thus move relative to the electrical contacts on the underside of the carrier. This movement alters the status of the electrical circuit, either by shorting or opening a set of spaced contact pads or by changing the setting on a potentiometer. 
     FIG. 3 illustrates a second embodiment that is similar in many respects to the first embodiment. The primary difference is the electrical contact member in this embodiment is a wiper  52  instead of a coupler and armature. The wiper  52  is preferably a metallic element fastened directly to the underside of the rotor head. It will be understood that with this form of contact member the electrical conductors would be formed on the top of the carrier instead of on the bottom. Otherwise the wiper performs the similar function of moving with the rotor to alter the condition of a potentiometer or to short or open spaced contact pads. The back cover  54  in this embodiment also differs somewhat in that it does not require a chamber for the armature so it may have more or less a simple block configuration with appropriate slots for receiving the front cover latches. 
     Turning now to FIGS. 4 a ,  4   b  and  4   c , application of the kit of the present invention to a more complex carrier is shown. The kit in this case includes a front cover  56  having a central opening  58  and a peripheral flange  60 . A detent ring  62  fits into the cavity of the front cover. A rotor  64  with a head  66  and stem  68  fit into the front cover. The stem  68  extends through opening  58 . A knob  70  fastens to the outer end of the stem. A detent ball  72  and spring  74  fit in a bore in the head  66 . Two sets of coupler magnets  76  also reside in the head. Armature balls  78  follow the magnets around on the opposite side of a sheet of plastic as described below. 
     These components are mounted on a three-part carrier comprising, from top to bottom, an overlay  80 , an upper spacer  82  and an upper circuit sheet  84 . These three layers are adhesively bonded together. The overlay has an aperture  86  directly above an opening  88  in the upper spacer. The aperture  86  is sized to permit all but the flange  60  of the front cover to fit therethrough. The flange  60  resides in the spacer opening  88 . The underside of the upper circuit sheet  84  has a set of electrical conductors  90  printed thereon. As FIG. 4 a  shows these conductors extend onto a tail portion  91  for external connection. The armature balls  78  roll on the underside of the upper circuit sheet  84 , in association with the conductors  90 . 
     The switch panel of FIG. 4 a  further comprises a magnet layer  92  bonded by adhesive  94  to the three-part carrier. The magnet layer has ports  96  therein and overlies a lower spacer  98 . Apertures  100  in the lower spacer accommodate push button armatures  102  which are made of magnetic material. As used herein “magnetic material” means material that is affected by a magnet. These armatures have buttons  104  which extend into the ports  96  of the magnet layer. Beneath the lower spacer is a lower circuit sheet  106  having electrical conductors  108  formed on its upper surface. These conductors include contact pads  110  which can be shorted by the armatures  102 . The armatures are normally held in spaced relation to the pads  110  by the magnetic attraction to the magnet layer  92 . When a user depresses the overlay  80  above an armature  102  the force is transferred to the button  104  and causes the armature to snap free of the magnet layer and short the pads. Release of the actuating pressure allows the magnet layer to retract the armature back into spaced relation with the pads. A substrate or backing plate  112  may be adhesively attached to the lower circuit sheet  106 . 
     It can be seen that the rotary switch kit of the present invention permits application of a rotary switch wherever it may be desirable on a flat panel switch. All that is needed is to print or otherwise form the appropriate electrical conductors and punch the perforations in the carrier to allow mounting of the front and back covers. Thus, existing flat panels can have rotary switches added thereto without interfering with the existing construction. 
     While a preferred form of the invention has been shown and described, it will be realized that alterations and modifications may be made thereto without departing from the scope of the following claims. For example, instead of having latches extend through the carrier to engage a back cover, the rotary switch with the wiper contact could have the front cover adhesively secured to the carrier. In that embodiment no back cover would be necessary.