Abstract:
A dual magnet Hall effect switch for contactless switching is provided. The Hall effect switch includes a magnet carriage and a Hall effect sensor positioned inside a switch housing. The magnet carriage includes two magnets positioned with opposite polarities facing the Hall effect sensor and in contact. When the switch is actuated, the magnet carriage is displaced within the switch housing and relative to the Hall effect sensor. The two magnets positioned inside the magnet carriage are also displaced. The positional displacement of the magnets relative to the Hall effect sensor alters the magnetic field detected by the Hall effect sensor. When the magnetic field detected by the Hall effect sensor reaches a predetermined level, the switch is actuated. The Hall effect switch also includes a boot seal sealing the switch and an internal clicker ball to provide an audible or tactile indication of the switch&#39;s actuation.

Description:
BACKGROUND OF THE INVENTION 
   The present invention generally relates to a dual magnet Hall effect switch. More particularly, the present invention relates to a push button, dual magnet Hall effect switch wherein the two magnets are aligned in parallel, in contact, and have opposite polarities. 
   The Hall effect occurs when charge carriers moving through a material experience a deflection because of an applied magnetic field. The deflection of the charge carriers results in a measurable electrical potential difference across the material. The potential difference is transverse to the magnetic field and the current direction. A Hall effect transducer measures the applied magnetic field and converts that measurement into a voltage. Hall effect transducers may be packaged to form commercially available Hall effect probes. 
   Many common applications may rely on the Hall effect and Hall effect probes. For instance, some computer keyboards employ a small magnet and a Hall effect probe to detect when a key is pressed. Some antilock brakes use Hall effect transducers to detect changes in a car wheel&#39;s rotational velocity, which can be used to calculate the appropriate braking pressure on each wheels. Additionally, Hall effect probes may be used to measure very small and slow fluctuations in a magnetic field, possibly down to one-hundredth of a gauss. 
   Hall effect probes may be used in a variety of applications and are particularly well-suited for use in contactless switches. A contactless switch typically includes a Hall effect probe, a magnetic field generator such as a magnet, and a mechanical activation means. In operation, a user activates the mechanical activation means, such as by flipping a switch. The mechanical activation means causes the magnet to move relative to the Hall effect probe. The movement of the magnet relative to the Hall effect probe induces a change in the magnetic field detected by the Hall effect probe. When the magnetic field reaches a predetermined level, the switch is treated as activated. Although the magnet is displaced relative to the Hall effect sensor, the magnet does not contact the sensor, nor does any electrical contact occur. Contactless switches offer improved reliability over conventional switches in which mechanical electrical contacts occur because contactless switches degrade less over time and are thus more reliable. For example, the mechanical contacts in a conventional switch may become corroded with use or alternatively the contacts may no longer form an acceptable electrical connection with use, Hall effect switches may be durable up to millions of actuations. 
   One useful example of a contactless Hall effect switch is U.S. Pat. No. 4,489,303 issued to Martin (hereinafter the Martin patent). The Martin patent discloses a contactless switch and joystick controller using Hall elements. FIGS. 4 and 5 of the Martin patent show contactless switches employing the Hall effect. Referring to FIG. 4, the contactless switch 60 includes a rod 74 having a magnet 86 mounted on one end, and a push button 80 mounted on the other end. A Hall effect switch 92 is positioned 20 below and in alignment with the rod 74. When the push button 80 on the rod 74 is depressed, the end of rod 74 upon which the magnet 86 is mounted is displaced towards the Hall effect switch 92. The displacement of the magnet 86 towards the Hall effect switch 92 generates a magnetic field at the Hall effect switch 92 which increases as the magnet 86 approaches. When the magnetic field detected at the Hall effect switch 92 reaches a predetermined level, the Hall effect switch 92 is actuated. 
   FIG. 5 of the Martin patent illustrates an alternate embodiment of a contactless switch 100 employing the Hall effect. The contactless switch includes a rod 74′ having a push button 80′ mounted on one end, a Hall effect switch 110 and two magnets 106, 108. The two magnets 106, 108 are mounted in the midportion of the rod 74′. Instead of the end-positioned Hall effect switch 60 of FIG. 4. the contactless switch 100 employs a Hall effect switch 110 mounted parallel to the axis of the rod 74′ near to the two magnets 106, 108. When the push button 80′ is engaged. the rod 74′ is displaced downward thus moving the two magnets 106, 108 with respect to the Hall effect switch 110. The movement of the two magnets 106, 108 relative to the Hall effect switch 110 produces a change in the magnetic field detected by the Hall effect switch 110. When the magnetic field detected at the Hall effect switch 110 reaches a predetermined level, the Hall effect switch 110 is actuated. 
   The two magnets 106, 108 of FIG. 5 are separated by a section of the rod 74′. The separation of the magnets may help to increase the region of linearity of the magnet&#39;s magnetic field. A large region of linearity is preferable in many applications because it allows the magnetic field to adjust more slowly with actuation, thus allows a detecting Hall Effect probe to track with greater accuracy. 
   The invention of the Martin patent is directed toward a video game. In switching applications outside of the video game arena, greater precision switches may be desired. That is, a more precise trigger point for the switch actuation is desired. Also, thermal effects may be encountered in some applications and may alter a switch&#39;s magnetic field or the sensitivity of the switch&#39;s Hall effect probe. 
   Thus, a need has long existed for a Hall effect switch having a greater switching precision and increased resistance to thermal effects. 
   SUMMARY OF THE INVENTION 
   The present invention provides a dual magnet Hall effect switch for contactless switching. The Hall effect switch includes a an internal housing positioned inside an external housing. Inside the internal housing is a magnet carriage having two magnets, a return spring, a Hall effect sensor and a clicker ball. The two magnets are positioned in contact with each other and with opposite polarities facing the Hall effect sensor. When the switch is actuated, the magnet carriage is displaced relative to the Hall effect sensor. The resulting displacement of the two magnets within the magnet carriages alters the magnetic field detected by the Hall effect sensor. When the magnetic field detected by the Hall effect sensor reaches a certain predetermined level the switch is actuated. 
   Because the two magnets inside the magnet carriage are positioned in contact and with opposite polarities facing the Hall effect sensor, the change in magnetic field with displacement is relatively large. The switch thus provides a more precise trigger point than conventional switches. 
   These and other features of the present invention are discussed or apparent in the following detailed description of the preferred embodiments of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates the individual components of a push button dual magnet Hall effect switch according to a preferred embodiment of the present invention. 
       FIG. 2  illustrates the assembled push button dual magnet Hall effect switch of  FIG. 1  in its non-actuated position according to a preferred embodiment of the present invention. 
       FIG. 3  illustrates the assembled push button dual magnet Hall effect switch of  FIGS. 1 and 2  in its actuated position according to a preferred embodiment of the present invention. 
       FIG. 4  illustrates a flow chart of a preferred embodiment of the present invention. 
       FIG. 5  illustrates a three-magnet Hall effect switch according to a preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the following detailed description, spatially orienting terms are used such as “left”, “right”, “vertical”, “horizontal”, and the like. It is to be understood that these terms are used for convenience of description of the preferred embodiments by reference to the drawings. These terms do not necessarily describe the absolute location in space, such as left, right, upward, downward, etc., that any part must assume. 
     FIG. 1  illustrates the individual components of a push button dual magnet Hall effect switch  100  according to a preferred embodiment of the present invention. The switch  100  includes an end cap  105 , exterior housing  110  having an axis  111 , an interior housing  120 , a magnet carriage  130 , a boot seal  140 , a seal washer  150 , a return spring  160 , a Hall effect sensor  170 , an first magnet  180 , a second magnet  185 , a clicker ball  190 , a clicker ball aperture  195 , and a clicker ball spring  197 . 
     FIG. 2  illustrates the assembled push button dual magnet Hall effect switch  100  of  FIG. 1  in its non-actuated position according to a preferred embodiment of the present invention. As seen in  FIGS. 1 and 2 , the interior housing  120  is positioned axially within the exterior housing  110 . The magnet carriage  130  is positioned axially within the interior housing  120 . The boot seal  140  is positioned axially between the magnet carriage  130  and the exterior housing  110  and longitudinally between the seal washer  150  and the exterior housing  110 . The seal washer  150  is positioned longitudinally between the boot seal  140  and the interior housing  120  and axially between the magnet carriage  130  and the exterior housing  110 . The return spring  160  is positioned axially between the magnet carriage  130  and the interior housing  120  and longitudinally between the seal washer  150  and the interior housing  120 . The first magnet  180  and the second magnet  185  are positioned along the longitudinal axis of the exterior housing  110  and adjacent to each other and are embedded in the magnet carriage  130 . The first magnet  180  and second magnet  185  are in contact with each other. The contact point describes a magnet contact region  182 . The Hall effect sensor  170  is positioned radially between the first magnet  180  and second magnet  185  and the interior housing  120 . The Hall effect sensor  170  is positioned longitudinally between the magnet carriage  130  and the interior housing  120  so that the midpoint of the Hall effect sensor  170  is generally located at the magnet contact region  182  when the switch  100  is in its actuated position (see FIG.  3 ). The end cap  105  is positioned on top of the exterior housing  110  and in contact with the magnet carriage  130 . 
   The clicker ball  190  and clicker ball spring  197  are positioned within the clicker ball aperture  195  and are positioned generally radially outwardly from the magnet contact region  182 . The clicker ball spring  197  is in contact with the exterior housing  110  and biases the clicker ball  190  into contact with the magnet carriage  130 . The magnet carriage  130  includes a clicker nub  198 . The clicker ball  190  is biased against the clicker nub  198  on the exterior of the magnet carriage  130 . 
   The exterior housing  110  is preferably constructed of a metallic substance such as aluminum. The end cap  105 , interior housing  120 , magnet carriage  130 , and boot seal  140  are preferably constructed of plastic. The seal washer  150  is preferably constructed of rubber or another elastomeric product. The return spring  160 , clicker ball  190 , and clicker ball spring  197  are preferably constructed of a metallic substance such as steel. 
   In  FIG. 2 , the hall effect switch  100  is shown in its non-actuated position. In operation, a user activates the switch  100  by pressing on the end cap  105  which is in mechanical contact with the magnet carriage  130 . The magnet carriage  130  is downwardly displaced within the exterior housing  110  and interior housing  120 . The downward displacement of the magnet carriage  130  is against the action of the return spring  160  and causes the return spring  160  to be compressed. The downward displacement of the magnet carriage  130  also causes the magnet contact region  182  to be downwardly displaced relative to the Hall effect sensor  170 . The displacement of the magnet contact region  182  relative to the Hall effect sensor  170  causes the magnetic field detected by the Hall effect sensor  170  to change. The change in magnetic field detected bv the Hall effect sensor  170  causes the switch  200  to be actuated. 
     FIG. 3  illustrates the assembled push button dual magnet Hall effect switch  100  of  FIGS. 1 and 2  in its actuated position according to a preferred embodiment of the present invention. As shown in  FIG. 3 , the downward displacement of the end cap  105  by the user also causes the clicker ball  190  to be moved from its non-actuated position in contact with the clicker nub  198  on the exterior of the magnet carriage  130 . As the magnet carriage  130  is downwardly displaced, the clicker ball  190  is forced past the clicker nub  198  to its actuated position as shown in FIG.  3 . The movement of the clicker ball  190  produces an audible clicking sound and a tactile sensation to the user to provide an audible or tactile indication that the switch  300  has been actuated. 
   Once the switch  300  has been actuated, the user releases the end cap  105 , thus removing the force that provides the downward displacement of the magnet carriage  130  against the action of the return spring  160 . The return spring  170  then expands upwardly and returns the magnet carriage  130  to its non-actuated position as shown in FIG.  2 . The upward displacement of the magnet carriage  130  returns the magnet contact region  182  to its non-actuated position. 
   Preferably, the switch  300  is sealed so that it is air-tight and water-tight. In this respect, the boot seal  140  and seal washer  150  maintain an air and water tight seal for the interior of the switch  100  during activation of the switch  100 . 
   The actuation of the switch  100  is summarized in the flowchart  400  of FIG.  4 . First, at step  405 , the user activates the switch  100 . When the user activates the switch  100 , steps  410 ,  415 , and  420  occur simultaneously. The magnets contact region  182  is displaced relative to the Hall effect sensor  170  at step  415 , the return spring  160  is compressed at step  410 , and the clicker ball  190  is displaced from is non-actuated position in contact with the clicker nub  198  as shown in  FIG. 2  to its actuated position as shown in  FIG. 3 , at step  420 . Next, the change in magnetic field due to the displacement of the magnets is detected by the Hall effect sensor  170  at step  430 . The switch  100  is then actuated at step  440 . At step  450 , the user releases the switch  100 . When the user releases the switch  100 , steps  460 ,  470  and  480  occur simultaneously. At step  460 , the return spring  160  expands. The magnet carriage  130  is returned to its non-actuated position at step  470 . Finally, at step  480 , the clicker ball  190  is returned to its non-actuated position as shown in FIG.  2 . 
   The first magnet  180  and second magnet  185 , in addition to being in contact, are preferably cylindrical magnets. The ends of the cylindrical magnets are opposite polarities, commonly called north and south. The first magnet  180  and second magnet  185  are positioned so that the end of the first magnet  180  having a south polarity is positioned adjacent next to the end of the second magnet  185  having a north polarity and vice versa. Because the first magnet  180  and second magnet  185  are positioned with opposite polarities facing the Hall effect sensor  170 , the change in magnetic field detected by the Hall effect sensor  170  as the magnets are displaced is large or very well defined. Additionally, because the magnets are in contact, the change in magnetic field as the magnets are displaced is more sharply defined than the change would be if the magnets were separated by some distance. Thus, the positioning and orientation of the magnets according to the present invention yields a precise transition point for switching. 
   Because the change in polarity of the magnetic field generated by the magnets takes place over a small displacement, only a small displacement is needed to actuate the switch  100 . Thus, the switch  100  does not require the extended region of linearity that may be present in the prior art and instead uses a very precise switching point. The switching point is precise because the magnets are in contact and are aligned with opposite polarities so that a small displacement of the magnets produces a large change in magnetic field as detected by the Hall effect sensor  170 . As discussed above, the change in magnetic field is detected by the Hall effect sensor  170  and causes the switch  100  to be actuated. The sensitivity of the present invention is such that the switch  100  may be actuated by a displacement of mere thousandths of an inch. 
   Alternatively, the above invention may be implemented using more than two magnets, as shown in FIG. 5. FIG. 5 illustrates a three-magnet Hall effect switch  500  according to a preferred embodiment of the present invention. In FIG. 5, three magnets are inserted in the magnet carriage  130  in place of the first magnet 180 and second magnet 185. The polarities of the magnets may be aligned as north-south-north as shown or alternatively may be north-south-north. This magnet alignment may also yield a fairly large change in magnetic field with displacement. Other variations of magnet number and positioning are also possible. 
   The Hall effect sensor may be an off-the-self device such as the “3123 Hall effect Switch for High Temperature Operations” commercially available from Allegro Micro System, Inc. While the present invention is described in connection with a push button switch, it will be appreciated by those skilled in the art that the invention is equally applicable to other types of switches such as rocker switches, toggle switches, etc. Other changes, such as providing a detent mechanism, may be made to the switch  100  without departing from the scope of the claimed invention. Additionally, although the preferred embodiment of present invention is described in connection with cylindrical magnets because of ease of manufacturability, the invention is equally applicable to magnets of other shapes. 
   While particular elements, embodiments and applications of the present invention have been shown and described, it is understood that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teaching. It is therefore contemplated by the appended claims to cover such modifications and incorporate those features which come within the spirit and scope of the invention.