Island switch

Abstract

A magnetically actuated pushbutton switch has individual switch modules pre-assembled as standalone subassemblies. Each subassembly has a platform with a cavity on its underside. A portion of the platform is magnetized. A metallic armature is held in the cavity by the magnetic attraction of the platform. The switch subassemblies are mounted on a substrate that has electrodes thereon. The armature is movable into and out of shorting relation with the electrodes. Plugs on the platform may align with holes on the substrate to locate the subassemblies.

Description

BACKGROUND OF THE INVENTION

Magnetically actuated pushbutton switches have a metal armature normally held spaced from switch contacts by a magnet. Pushing on the armature causes it to snap free of the magnet and close the switch contacts by shorting them. Release of the actuating pressure allows the magnetic force to withdraw the armature from the contacts to reopen the switch. The switches typically are made in panels having a non-conductive substrate with electrical contacts formed thereon. A non-conductive spacer layer lies on the substrate with openings therein exposing the contacts. A sheet magnet overlies the spacer with the armatures underneath the magnet layer in the spacer openings. The armatures preferably have actuating buttons that protrude through apertures in the magnet layer. Most often the magnet layer itself is covered by a membrane or the like, the upper surface of which carries suitable graphics. The benefits of magnetically-actuated pushbutton switches have been demonstrated in U.S. Pat. Nos. 5,523,730, 5,666,096, 5,867,082 and U.S. patent application Ser. No. 09/160,645, filed Sep. 25, 1998, the disclosures of which are incorporated herein by reference.

Although the pushbutton switch as shown and described in the foregoing patents is very robust and easy to manufacture, relative to its counterparts, certain improvements in the manufacturing process are addressed by the present invention. The most difficult and expensive process in the manufacture of the described pushbutton switches is assembling all of the individual layers consistently. This can be a problem around the individual switch areas where the alignment with the armature is critical. Using pins to align the individual layers relative to each other is adequate to assemble a magnetically actuated pushbutton switch, although it is most advantageously done with special assembly apparatus. Tolerances are always a problem, however. As the overall size of the switch panel increases, the tolerances become difficult to control. The present invention teaches an alternative method of construction to eliminate the problems with assembly and to significantly reduce the overall product cost.

SUMMARY OF THE INVENTION

The present invention concerns a magnetically actuated pushbutton switch wherein each switch includes a pre-assembled, free-standing actuator subassembly. Because each subassembly is separate from the others on a switch panel, they are sometimes referred to herein as island modules. The subassembly is made up of a platform which defines a cavity on its underside. The platform can be either stratified or monolithic. At least a portion of the platform is magnetized. A metallic armature fits into the cavity and is held therein by the magnetic attraction of the magnetized portion of the platform. The stratified platform may comprise a local spacer having a local opening therein, and a coupler which is a magnet. The coupler may have an aperture that allows an actuating button formed on the armature to protrude and receive the actuating force. An upper spacer may surround the protruding button to provide a top surface for supporting a membrane or overlay. The alternate, monolithic platform is formed as a single, integral component. Magnetization of the monolithic platform can take place immediately prior to installation of the subassembly.

The actuator subassemblies are mounted on a substrate. The substrate carries electrodes which include at least one set of switch contacts. In some applications it may be desirable to place a major spacer over the substrate with openings in the major spacer aligned with the switch contacts. The actuator subassemblies are then placed into these openings to complete the switch. The armature may be provided with a lens to disperse backlighting. Tactile domes may be added to the actuator subassemblies. The subassemblies may have multiple armatures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a full switch panel according to the present invention.

FIG. 2 is an exploded perspective view of an actuator subassembly.

FIG. 3 is a section through the completed subassembly of FIG. 2 .

FIG. 4 is a top plan view of the subassembly.

FIG. 5 is a section through an alternate embodiment of a switch panel having a monolithic island module.

FIG. 6 is an exploded perspective view of the bottom of the monolithic island module.

FIG. 7 is an exploded perspective view of the top of the monolithic island module.

FIG. 8 is a perspective view of a further alternate embodiment of a switch panel having a substrate, major spacer and top film with an integrated rotary switch.

FIG. 9 is a perspective view of the switch panel of FIG. 8 with the top film removed to reveal the major spacer and the multiple armature island module.

FIG. 10 is a perspective view of the switch panel of FIG. 8 with both the top film and major spacer removed to reveal the substrate.

FIG. 11 is a top plan view of a tactile dome.

FIG. 12 is a section taken along line 12 — 12 of FIG. 11 .

FIG. 13 is a section through a further alternate embodiment of a switch panel having a lens in the armature for transmitting light through the actuator subassembly.

FIG. 14 is a view similar to FIG. 13 showing a further variation.

FIG. 15 is an exploded perspective view of a further alternate embodiment.

FIG. 16 is a section through the embodiment of FIG. 15 in an unactuated condition.

FIG. 17 is similar to FIG. 16 showing the armature in an actuated condition.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a switch panel 10 according to the present invention. The panel includes a substrate 12 which is formed of either rigid or flexible non-conductive material. For example, the substrate can be made of printed circuit board material or plastic film such as polyester. At least one surface of the substrate has electrodes formed thereon by a suitable process such as etching or screen printing. Electrodes can be arranged in any suitable manner and will typically include leads 14 which extend to an appropriate connector portion at an edge of the substrate. The electrodes will also include sets of spaced switch contacts such as the pads shown at 16 A, 16 B and 18 A, 18 B. As can be seen, the switch contacts 16 , 18 are suitably connected to various ones of the leads 14 and the contacts themselves are spaced apart. It will be understood that the electrodes and contacts can be arranged in any configuration needed. For example, instead of the simple pads shown at 16 and 18 , a more complex arrangement of spaced, interleaved fingers could be used.

A major spacer 20 is mounted on the substrate 12 . The spacer is made of a thick film or rigid material, preferably with adhesive located on the top and bottom surfaces. A typical material used in this application would be closed cell adhesive foam such as one manufactured by 3M Corporation and sold under their trademark VHB Series. This material is supplied with a high bond adhesive on both the top and bottom surfaces. Release liners cover the adhesive layers prior to assembly. One advantage of using closed cell foam as a spacer is that the flexibility of the material allows the adhesive to bond readily with the substrate, even if it has a rough surface. Typical imperfections on the surface would be conductive traces such as the screened silver or etched copper leads 14 . The closed cell foam material protects the switch from liquids and gases and allows the assembly to be sealed. While the use of adhesive is the preferred method of joining the major spacer and substrate, mechanical means could be used, either alone or in combination with adhesive.

The major spacer 20 has openings 22 formed therein and located so as to expose the sets of contacts on the substrate. Thus, opening 22 A is aligned with the switch contacts 16 while opening 22 B is aligned with and exposes contacts 18 . Individual island modules or actuator subassemblies 24 fit into the openings 22 . Details of the subassemblies 24 will be described below. Miscellaneous components can also be pre-assembled on to the substrate 12 . When such components are included, holes similar to openings 22 are cut into the major spacer to accommodate these components. This is shown in more detail in FIGS. 9 and 10 .

After insertion of the switch subassemblies 24 into openings 22 , release liners, if present, are removed from the top surfaces of the major spacer 20 and the subassemblies 24 . A top film layer or membrane 26 is placed over the major spacer and actuator subassemblies 24 . The film layer 26 is made of flexible plastic or elastomeric material. It can have suitable graphics printed thereon to instruct a user as to the location of a switch subassembly. The film layer adheres to the major spacer 20 and, optionally, to the top of the subassemblies 24 . As mentioned above, mechanical methods may also be used to secure the film layer 26 .

Looking now at FIGS. 2-4 , details of the actuator subassembly or island module 24 will be described. Each subassembly has two major components, a platform and an armature. The platform defines a cavity for receiving the armature. The embodiment of FIGS. 2-4 shows a stratified platform which includes a local spacer 28 , a coupler 30 and an upper spacer 32 . The local spacer 28 is made of non-conductive material such as polyester. It has a local opening 34 , an upper surface 36 and a lower surface 37 . The local opening 34 extends all the way through the thickness of the local spacer. The coupler 30 also has an aperture 38 all the way through its thickness. The coupler is a sheet magnet. Together the coupler 30 and the local spacer 28 define a cavity in the area of the local opening 34 . The upper spacer 32 has three legs 40 forming three sides of a rectangle and defining an open area which surrounds the coupler aperture 38 . The parts of the stratified platform may be held together by adhesive (not shown). Thus, adhesive may be deposited on the top and bottom sides of the upper spacer 32 and on the top surface 36 and the lower surface 37 of the local spacer 28 . Release liners may cover any of these adhesive layers until such time as joining with adjacent members is desired. For example, the lower surface 37 of the local spacer would have a release liner that would remain in place until it is time for the subassembly 24 to be mounted on the substrate 12 . If adhesive is used on the top of the upper spacer, a release liner thereon would be removed just prior to installation of the film layer 26 .

The second major component of the actuator subassembly 24 is an armature 42 . It is made of electrically conductive, magnetic material, i.e., material that is affected by a magnet. Typically the armature is soft steel. The armature shown has a disc-like configuration with an upstanding or protruding actuating button 44 formed on one side of the disc. The actuating button protrudes through the aperture 38 in the coupler 30 . The actuating button extends above the top surface of the coupler to the same extent as the thickness of the upper spacer 32 . Thus, the top of the button 44 and top of the upper spacer 32 terminate in the same plane. This provides a smooth, level surface for the top film layer 26 . Alternately, the button 44 could extend above the upper spacer 32 and cause a slight bulge in the film layer to provide a visual and tactile indication of the button's location. liner from the bottom surface 37 of the local spacer 28 and pressing the subassembly into the appropriate opening 22 in the major spacer 20 . Once that is done the armature 42 will reside above the switch contacts 16 or 18 . It will be noted in FIG. 4 that one corner of the subassembly may be beveled as at 45 . The major spacer opening 22 is similarly shaped. This affords a non-symmetrical configuration that prevents putting the subassembly in backwards.

When a user presses on the actuating button 44 it causes the left side (as viewed in FIG. 3 ) of the armature to break away from the coupler 30 until the left side of the armature bottoms on the switch contact pad, e.g. 16 A. Continued actuating pressure then causes the right side of the armature to break away and engage the other contact pad 16 B. This shorts the contact pads and closes the switch. Removal of the actuating pressure allows the magnetic force of the coupler 30 to pull the armature 42 back up off of the contacts and into the position shown in FIG. 3 wherein the armature is spaced from the contact pads.

An alternate embodiment of the actuator subassembly is shown in FIGS. 5-7 . In this embodiment, which may be referred to as a monolithic island module, the platform 46 is made as a single, integral part. It includes a coupler layer 48 having an aperture 50 therethrough. The underside of the coupler 48 has a rim 52 around its perimeter. The rim defines a depression or cavity 54 in which the armature 42 sits. The top side of the coupler 48 has an upper spacer 56 around three side edges. The armature 42 resides in the cavity 54 with its actuating button 44 extending through the aperture 50 . It can be seen that the monolithic platform has just one part compared to the three part stratified platform.

This construction offers a number of advantages in addition to ease of manufacture. For example, the sheet magnet material used in other switches is magnetized in a series of parallel poles of opposite polarity. This makes it difficult to specifically magnetize a particular area to a certain polarity or to increase its magnetic force. The unitary design of the monolithic island module platform allows for the magnetic poles to be placed at very specific points, thus allowing for high magnetic forces to be placed in the position where they will allow for increased and optimum switch actuation force and travel characteristics. Additionally, state of the art sheet magnet materials are limited to relatively low force ferrite magnet materials. The molded construction of this teaching allows the magnets to be fabricated from high magnetic force rare earth materials such as neodymium iron boron and samarium cobalt. In addition, thicker magnets can be fabricated that have greater magnetic induction strengths. Much smaller switches thus can be fabricated since the monolithic platform does not suffer the limitations of prior art products which, at least to some extent, are limited by the overall area of the switch armature and the thickness of the magnet material. Another advantage of the monolithic platform is it can be molded but not magnetized until it is ready for assembly. The platform is magnetized at the time of installation of the substrate, i.e., either just prior to or immediately after installation on a substrate. This timing makes it much easier to keep the platform clean after its fabrication but prior to installation. Also, the unassembled, unmagnetized platforms are easier to handle in containers such as bags or boxes because they don't stick together as much as magnetized components do. Greater control of the magnetic field strength is also possible. The platform could be magnetized with multiple parallel poles or with just two poles.

FIGS. 8-10 illustrate a further variation on the island switch. This switch panel 58 comprises a substrate 60 , a major spacer 62 and a top film layer 64 . These may be made of materials similar to those of the FIG. 1 embodiment. The top film layer may have a tail 66 that extends to a connector 68 for attachment to an associated electronics unit (not shown). The top film has conductors on its underside as needed to create a rotary switch. The switch rotor is shown at 70 . Further details of the rotary switch are shown in U.S. Pat. No. 5,867,082. FIG. 9 illustrates the major spacer 62 and a large opening 72 therein which accommodates a multiple-armature island switch module. This module has a platform 74 that has three cavities underneath it for receiving three separate armatures 76 A, 76 B and 76 C. The platform 74 fits within opening 72 . The major spacer 62 also has a plurality of smaller openings 78 . These accommodate surface mounted components such as those illustrated diagrammatically at 80 in FIG. 10 . These components are mounted on the printed circuit board that forms the substrate 60 . FIG. 10 also shows how the platform 74 rests on the top surface of the substrate 60 . It will be understood that the top of the substrate would also have electrodes (not shown) formed thereon to connect to switch contact pads underneath the armatures 76 .

The island switch modules of FIGS. 2 and 5 are also applicable to a dome switch. For years, the membrane switch industry, and indeed most tactile pushbutton switch manufacturers, have utilized metal or plastic domes to provide tactile feel for their switches. The major problem associated with the tactile dome membrane switches has been repeatability from one switch to another within a switch panel. These inconsistencies are due primarily to inconsistencies in alignment and assembly of the layers. In the present invention, assembly of the dome switches can be automated and the domes can be placed as individual islands, thus eliminating the prior art inconsistencies for all intents and purposes. One example of how such an island would look is shown in FIGS. 11 and 12 . A tactile dome 82 is held in place on top of the actuator subassembly by a dome retainer 84 . The retainer may be adhesively fixed to the magnet layer 30 . The dome may fit within the legs 40 of the upper spacer 32 .

Looking now at FIGS. 13 and 14 , another aspect of the present invention is shown and described. In many switch applications, backlighting of the individual switch positions or modules is required. There are a number of alternative techniques available at the present time for providing lighting. Among these are edge lighting, light pipes and electroluminesence. Each of these various techniques has different degrees of difficulty, cost and limitations. This disclosure offers a unique method of lighting magnetically actuated pushbutton switches. The basic construction is similar to that of the switch panel 10 in FIG. 1 and the actuator subassembly 24 in FIGS. 2 and 3 . Common elements are given common reference numbers and their description will not be repeated. The island module shown generally at 86 includes a back light source 88 shown schematically in this example as an LED. It will be understood that the LED is electrically connected to a suitable power source and physically mounted in a suitable housing underneath the substrate 12 . The armature 90 has a lens or crystal 92 insert molded as part of the armature. Alternately, the lens 92 can be snapped in place in an opening in the armature. As shown in FIG. 13 , the light is piped up from underneath the armature and through either an opening or transparent portion of the substrate 12 . Light is scattered at the top surface of the lens 92 through the overlay film 26 . This allows the center of the individual switch module to be lighted.

The shape of the lens is important in that the light has to be scattered to provide uniformity across the face of the switch. A faceted design is shown in the figure on the top and bottom surfaces. It is important to note that since the actual switch contacts are not in the center of the lens 92 , the switch contact integrity is not compromised, as is often the case with domed or standard membrane switches.

The light scattering can be enhanced by providing a diffraction grating as shown in FIG. 14 at 94 . This grating is placed between the overlay film 26 and the upper spacer 32 . Alternatively, the diffraction grating could be placed just on top of the lens 92 . A diffraction grating is a series of diffracting lines either etched or molded into the surface and extending as concentric rings around the center of the light source. Providing a fluorescing layer on the bottom surface of the top film can enhance the light scattering. This layer is loaded with fluorescing dye and can either be screened on the bottom surface of the overlay or inserted as a separate film.

A further alternate embodiment of the actuator subassembly is shown in FIGS. 15-17 . This version is a directionally sensitive island switch which combines the actuator subassembly of the present invention with the directionally sensitive switch of U.S. Pat. No. 6,069,552, the disclosure of which is incorporated herein by reference. The actuator subassembly 96 is mounted on a substrate 98 . The substrate has a set of electrodes or conductors formed on the first surface thereof. The electrical conductors are made of conductive materials that may be painted, printed, etched or otherwise formed on the first surface of the substrate. In this case the electrical conductors are laid out in the form of a potentiometer. The potentiometer has high and low voltage leads 100 and 102 on either end of a circular carbon resistor element 104 . Inside the resistor element is a common contact pad 106 connected to a common lead 108 that extends out between the high and low voltage leads. It will be understood that the leads extend to a suitable connector, typically at an edge of the substrate, for connection to external electronics. The external electronics supply any required electrical signals on the leads 100 , 102 , and detect the output on lead 108 .

In the embodiment of FIGS. 15-17 , which may be referred to as a monolithic directionally sensitive island switch, the platform 110 is made as a single part. The platform is typically manufactured by an injection molding process. If any of the injection molding ejector pins are shortened during the manufacturing process, the injection molded platform will have a plug protruding from the platform at the location of every shortened ejector pin. The shortened ejector pins preferably form beveled edges at the ends of the plugs. From a manufacturer's perspective, incorporation of these plugs onto an existing mold adds virtually nothing to the cost of the platform.

In FIG. 15 , there are plugs 111 on the underside of the platform 110 in each corner, where the plugs will not interfere with the proper functioning of the switch. The plugs are used to align the platform with the substrate. The substrate 98 has appropriate depressions or holes 113 and 115 for receiving the plugs 111 when the assembly is brought together. The beveled edges on each plug make alignment of the subassembly 96 and substrate 98 easier. FIG. 15 shows the plugs arranged in a non-symmetrical configuration so that platform can only be installed in the proper orientation on the substrate. This will help maintain consistent tolerances when the switches are assembled in mass quantity. The mold for the platform 110 forms the upper right corner in FIG. 15 so that the corner is angled or beveled at a 45 degree angle. The upper right corner has its plug, as well as the plug's corresponding hole 115 , moved down slightly. Alternatively, the plugs may be symmetrically located on the platform so that the substrate may receive a platform in any orientation. An example of a symmetrical platform is one that is square with a plug identically located in each of the four corners.

The platform 110 includes a magnetized coupler layer 112 having an aperture 114 therethrough. The top side of the coupler layer 112 has an upper spacer 116 . The underside of the platform 110 has a platform rim 118 ( FIGS. 16 , 17 ) around its perimeter. The platform rim defines a depression or cavity 120 which receives an armature as will be explained below. It can be seen that the monolithic platform has just one part.

The platform 110 mounts an armature 122 which is made of electrically conductive, magnetic material. The armature has an upraised central crown 124 and an armature rim 126 . The crown has a central depression 128 on the upper side that also defines a central depending post 130 on the underside of the armature. The armature rim 126 is engageable with the coupler layer 112 . The armature rim 126 includes an annular ridge 132 . When the armature is in the unactuated position, as seen in FIG. 16 , the coupler layer 112 holds the armature, including the central post and annular ridge, spaced from the substrate and from the electrodes. To actuate the switch a force is applied to a particular portion of the crown 124 , say at the location of arrow A in FIG. 17 . This causes the armature rim 126 to break away from the magnetized coupler layer 112 and carry the ridge 132 into contact with the resistor element 104 , as seen at the right hand side of FIG. 17 . Shortly thereafter the post 130 engages the contact pad 106 and completes a circuit from the high voltage lead 100 to the common lead 108 . The voltage on the common lead will depend on the location of the contact between the armature and the resistor element. Thus, the voltage signal provides an indication of where the armature was depressed by the user.

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, while at least a portion of the platform is described as being magnetized and the armature is made of magnetic material, this could be reversed so the armature is a magnet and the platform is magnetic material. Also, while the island switch modules have been described as joined to the substrate by adhesive which is covered by a release liner prior to installation, the modules could be retained by other means not requiring adhesive or release liners.

Claims

1. A method of making an electrical switch panel, comprising the steps of:forming at least one set of spaced electrodes on a substrate; fabricating a platform and an electrically conductive armature, one of the platform and armature being a magnet, the other of the platform and armature being made of magnetic material; forming an actuator subassembly by joining the platform and armature; and installing the actuator subassembly on the substrate with the armature aligned with the electrodes such that the armature is normally held spaced from the electrodes in engagement with the platform by the magnetic attraction between the platform and armature, the armature being releasable from the platform upon application of a switch closing force to engage and close the electrodes.

2. The method of claim 1 wherein the step of forming the armature is characterized by forming an upraised crown in the armature and a depending post in the center of the crown.

3. The method of claim 1 further comprising the step of forming holes in the substrate and wherein the step of fabricating a platform is further characterized by forming plugs on the underside of the platform, and wherein the step of installing the actuator subassembly is further characterized by placing the plugs into the holes formed on the substrate.

4. The method of claim 3 further characterized by forming beveled edges on the plugs.

5. The method of claim 3 further characterized in that the plugs are formed at locations that make the platform non-symmetrical.

6. An electrical switch, comprising:a substrate having electrodes disposed on the substrate and defining at least one set of spaced switch contacts; a plurality of holes formed in the substrate; an actuator subassembly mounted on the substrate for selectively opening or closing the switch contacts, the actuator subassembly comprising a platform having plugs extending into the holes of the substrate, the platform defining a cavity adjacent the switch contacts and an electrically conductive armature disposed in the cavity, one of the platform and armature including a permanent magnet and the other being made of magnetic material such that the armature is normally held spaced from the switch contacts in engagement with the platform by the magnetic attraction between the platform and armature, the armature being releasable from the platform upon application of a switch closing force to engage and close the switch contacts.