Abstract:
A panel mounted low profile rotary switch ( 100 ) contains a detent mechanism ( 120 ) mounted in a bushing ( 110 ). In a preferred class of embodiments, the detent sub-assembly comprises a single spring ( 220 ) positioned in parallel within the vertical extending shaft ( 130 ). The force exerted by the spring is manually adjusted by a set screw ( 210 ) to provide the desired downward applied vertical force on a plunger ( 230 ). The plunger, preferably a pointed cylinder, applies pressure to detent balls ( 240 ) causing the detent balls to move radially outward and engage rotorcams located on the inner surface of the detent mechanism.

Description:
[0001]     This application claims priority to PCT patent application number PCT/US02135610 filed on 05 Nov. 2002. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of the invention is electromechanical rotary switches.  
       BACKGROUND OF THE INVENTION  
       [0003]     A rotary electromechanical switch is generally defined as a device that has a rotating shaft connected to one terminal capable of making or breaking a connection to one or more other terminals. A rotary electromechanical encoder includes the overall characteristics of a rotary switch, but has additional mechanical movements. In any case, a user typically manipulates the switch to manually select a circuit.  
         [0004]     Rotary switches and encoders are often mounted upon panels and other supporting structures in order that a user may control an electrical device. It is common for a portion of the switch to be on one side of the panel (the user side) and another portion of the switch to be on the other side of the panel (the inside). In many instances, the only portion of a switch that is on the user&#39;s side of the panel is a section of the shaft and a knob or other actuating means. Generally, the bulk of the switch is on the inside of the panel. For many years this type of configuration was sufficient, but over time the size of electrical devices has become increasingly smaller and there has become a need to reduce the size of the switch -.especially that portion on the inside of the panel.  
         [0005]     In order to meet the needs of smaller devices having less room under the panel, the size of the components of the switches have also become smaller. Yet, because these switches are comprised in part of mechanical components, there remained a practical limit as to how small they could become while still remaining useful. There became a need for different designs rather than just a reduction in the size of the components. One such design is taught in U.S. Pat. No. 4,454,391 to Olsson (June 1984). Olsson describes a low profile dip switch used on an integrated circuit board in which the actuating member of the dip switch is set within the body of the switch By reducing the vertical profile of the switch, a lower overall footprint may be achieved for a board. The switch design taught by Olsson, however, does not address design problems related to panel mounted switches. Another patent which addresses problems in the design of switches is described in U.S. Pat. No. 6,312,288 to Genz et al. (November 2001). Genz teaches a low profile combination switch and connector assembly. While the switch described by Genz may have resulted in a lower overall profile of the combined components, this switch still does not address problems of panel mounted switches, specifically those problems due to limited space under the panel.  
         [0006]     U.S. Pat. No. 6,043,855 to Grave (March 2000) is directed toward switches that mount on a bezel surrounding an LCD which is located on an avionics panel in an aircraft. The &#39;855 patent teaches a design in which the detent is at least partially positioned in the Icnob of the switch. Still, the design of the &#39;855 patent has its shortcomings: the detent is housed by the knob such that if the knob were to be displaced, the switch would not function or would function improperly; the detent is not entirely within the Icnob; the design requires two springs; and the springs are mounted vertically adding to the overall vertical profile of the knob.  
         [0007]     As electronic devices become even smaller, there is a need for more compact and efficient designs.  
       SUMMARY OF THE INVENTION  
       [0008]     The inventive subject matter is a panel mounted low profile switch having a detent sub-assembly housed in a bushing. The portion of the bushing housing the spring is in substantial planar relation with the panel within which the switch is mounted.  
         [0009]     In some embodiments the detent sub-assembly comprises a single spring positioned vertically in the vertical extending shaft.  
         [0010]     Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view of an exploded rotary switch.  
         [0012]      FIG. 2  is a perspective view of an exploded rotary switch  
         [0013]      FIG. 3  is a perspective view of an exploded rotary switch. 
     
    
     DETAILED DESCRIPTION  
       [0014]      FIG. 1  depicts a rotary switch  100  generally comprised of a bushing  110 , a detent mechanism  120 , a shaft  130 , an electrical contact  140 , and a printed circuit board (PCB)  150 .  
         [0015]     Bushing  110  is comprised of a threaded upper portion  112  and a lower portion  114 . As defined herein, a bushing is a component of a switch that is used to hold the switch to a panel (e.g. a control borad) through which the switch is mounted. A preferred bushing has an upper portion that extends through a hole in the panel and a lower portion that contacts the underside (i.e. non-user side) of the panel. In  FIG. 1 , bushing  110  has a threaded upper portion  112  that extends through hole  164  in the panel  160 . In order to facilitate holding of the switch to the panel, the lower portion  114  is of a diameter and/or shape that will not fit through the hole  164  in the panel  160 . A lock washer  172  is placed over the upper portion of the bushing  112  and the capture nut  170  is threaded to the upper portion  112  in order to hold the switch to the panel. It is not required that a bushing be threaded and that a nut be-used to hold the switch to the panel as non-threaded bushings may also be used. A non-threaded bushing can be held to the panel in other ways, for example by using rivets or compression fittings.  
         [0016]     It is generally contemplated that a bushing should not rotate, and herein there are provided means for substantially prohibiting such rotational movement One such means is a pin/aperture configuration in which the pin  116  fits snugly within an aperture  162  in the panel. In another class of embodiments, it may be advantageous to have a “D” shaped hole (opening) in the panel, such “D” shaped hole cooperating with a flat sided bushing to prevent rotation. It should be understood that any combination of suitable shapes and sizes will suffice so long as the combination substantially prohibits rotational movement For example, the hole in the panel and the associated upper portion of the bushing may have two or more flat sides.  
         [0017]     A detent sub-assembly is comprised of the detent mechanism  120  having rotors  121 , a spring  122 , and a ball  124 . Further analysis of the switch depicted in  FIG. 1  reveals a single spring detent sub-assembly in which the spring  122  is horizontally disposed (i.e perpendicular to the shaft). The spring is in contact (direct or indirect) with at least one ball  124 . Note that in some horizontal single sping embodiments two balls may be utilized, one on each end of the spring. In any case, the ball  124  is biased toward the inner surface of the detent mechanism  120 . Along the inner surface of the detent mechanism are rotor cams (ie. cylindrical lobes)  121 . As the shaft  130  of the switch is rotated, the-ball(s) rotates about the rotor cams as the electrical contact  140  rotates about the PCB  150 . The detent sub-assembly is housed within the bushing  110 , preferably within the upper portion of the bushing  112 . However, it is envisaged that a portion of the detent sub-assembly may extend into the lower portion of the bushing.  
         [0018]     It is preferred that the detent mechanism be prevented from rotation within the bushing. Along these lines, the detent mechanism  120  can have an extrusion  126  that engages a notch (not shown) on the inner surface of the bushing thereby preventing such rotation. Of course, the shaft is intended to rotate, however, it can be advantageous to limit the rotation of the shaft. Limiting rotation of the shaft can be accomplished by using a pin  132  to limit the degree of rotation as a function of the size of a notch  128  in the detent mechanism. By limiting the rotation of the shaft, the available switch settings can be limited. An electrical contact  140  (e.g. switch wipers or brushes) is mounted on a non-conductive disc  135  (ie. dielectric) and the contact  140  cooperates with the circuit configuration on the PCB  150 . The PCB  150  is anchored to the bushing  110  by metal rivets  190  or other connectors, however it should be noted that anchoring of the PCB to the bushing is not a requirement. Although not depicted, a PCB can contain additional electronic components (e.g. chips, pins, leads, and so forth) that may interface with components other than the switch. Setting of a switch position, therefore, is generally a function of the interaction among the detent sub-assembly, the shaft, the electrical contact and the PCB.  
         [0019]     Turning now to  FIG. 2 , an alternative embodiment includes a vertical spring  220  (i.e. parallel to the shaft), a set screw  210 , and a plunger  230 . The single vertical spring  220  is housed within the shaft and is elongated in the same direction as the shaft. The set screw  210  is threaded into the upper portion  212  of the shaft  130  thereby causing the plunger to exert outward pressure on the balls  240 . The outward pressure biases the balls in the direction of the rotor cams on the inner surface of the detent mechanism  120 . It should be noted that outward tension against the balls can be adjusted by threading or unthreading the set screw. As the set screw is threaded in, the plunger is forced downward (toward the PCB) and the balls are pushed outward. Of course, unthreading the set screw will have the opposite effect. A plunger is preferably cylindrical in shape and pointed. The preferred plunger not only provides uniform pressure to the balls, but it also allows for more than two balls to be used with a single spring.  
         [0020]     A switch can be configured to set a plurality of electrical settings.  FIG. 3  depicts a multiple deck switch having a vertical spring configuration. The embodiment of  FIG. 3  has two sets of contacts and two PCBs. The first set of contacts  140  is attached to a non-conductive (dielectric) disc  310  which is further coupled to the shaft  130 . A second non-conductive disc  320  is also coupled to the shaft  130  and is further coupled to a second set of contacts  330 . A spacer  340  provides insulation between the PCBs.  
         [0021]     Functionally, the shaft of a switch is generally rotated by manual movement in order to set a switch position. Switch positions are defined by the rotor cams (lobes) in the detent mechanism. Upon rotation of the shaft, a ball protruding from the shaft will get in the area between two rotor cams thereby defining a switch position. A user of the switch will be able to feel the ball set between the rotor cams. As a ball rotates about the inner surface of the detent mechanism, the contacts form electrical connections based on the relationship between the contact and the PCB. While the switches enumerated here are shown with a stop pin to limit the rotation of the shaft, this is not a requirement as some switches will allow  360  degree rotation in both directions.  
         [0022]     Methods of use include mounting a rotary switch such that the detent sub-assembly is in planar relation to a panel. Since most of the upper portion of the bushing is on the user&#39;s side of the panel, however, the detent sub-assembly may be substantially on the user&#39;s side of the panel rather than in a plane with the panel. Additionally, there may even be a portion of the detent sub-assembly which extends underside of the panel. Thus, a single detent sub-assembly may be positioned such that a portion of the detent sub-assembly is above the panel, a portion is parallel with the panel, and a portion is below the panel.  
         [0023]     Thus, specific embodiments and applications of a low profile switch with a detent in the bushing have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.