Patent Publication Number: US-10312908-B2

Title: Nested magnetic controls for industrial enclosures

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 62/233,485, filed Sep. 28, 2015, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure generally relates to industrial enclosures and, more specifically, to the incorporation of magnetic controls in industrial enclosures. 
     BACKGROUND OF THE DISCLOSURE 
     Industrial control systems are an important and necessary element in automating machinery and processes in industrial applications worldwide. Industrial control systems implement mechanical, hydraulic, pneumatic, and electrical controls as well as provide a user with a means to interface with these controls. The types of user interfaces can vary from a simple pushbutton to complex, computerized touch screens. Regardless of the type of user interface, each user interface must be presented to the user in an enclosure that is suitable to the environment in which the interface operates. As such, significant engineering work goes into designing enclosures that are not only appropriate to house a user interface but are also cost-effective to manufacture and maintain. Another important consideration of enclosure design is how to fit as many controls as possible into the smallest footprint while providing desired operability. 
     The many and varied types of industrial environments present different types of hazards and concerns. A major safety concern in dust laden industrial plants is the occurrence of fires and explosions. A source of energy is all that is needed to ignite an explosion when flammable gases or combustible dusts are mixed in the proper proportions with air. That source of energy can come from any number of sources within a plant environment however one area of particular concern is the plant&#39;s electrical installation which might include electrical components such as switches, circuit breakers, motor starter, pushbutton stations, or plugs and receptacles. 
     As such, the National Electric Code (NEC) has worked to establish a classification system to classify hazardous locations and to define standards for the types of electrical equipment that may be allowed into the hazardous location. The classes define the type of explosive or ignitable substances which are present in the atmosphere. Class I locations, those locations of particularly relevance to the present disclosure, are those in which flammable vapors and gases may be present. Class I is further subdivided into two divisions. Division 1 is a location in which ignitable concentrations of hazards exists under normal operation conditions and/or where hazard is caused by frequent maintenance or repair work or frequent equipment failure. Division 2 is a location in which ignitable concentrations of hazards are handled, processed or used, but which are normally in closed containers or closed systems from which they can only escape through accidental rupture or breakdown of such containers or systems. 
     With regard to the types of electrical equipment that may be allowed in a Class I, Division 1 or Division 2 location, the NEC noted that any type of conventional relay, contact, or switch that has an arcing contact must be enclosed in an explosion proof housing. The NEC has defined an Explosionproof Apparatus as an apparatus enclosed in a case that is capable of withstanding an explosion of a specified gas or a vapor that may occur within it and of preventing the ignition of a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within, and that operates at such an external temperature that a surrounding flammable atmosphere will not be ignited thereby. 
     Thus, an explosion proof enclosure must prevent the ignition of an explosive gas or vapor that may surround it. In other words, an explosion inside the enclosure must be prevented from starting a larger explosion outside the enclosure. An explosion proof enclosure must further be of adequate strength and be “flame-tight.” The term “flame-tight” does not imply that the enclosure is hermetically sealed but rather that the joints or flanges are held within narrow tolerances. These carefully machined joints cool the hot gases resulting from an internal explosion so that by the time they reach the outside hazardous atmosphere they are not hot enough to cause ignition. 
     Alternatively, intrinsically safe equipment may be used in a Class I, Division 1 or Division 2 location, wherein intrinsically safe equipment and wiring are incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture intis most easily ignited concentration. 
     The constraints around the types of enclosures that may be placed within a Class I, Division 1 or Division 2 location, must be addressed by the engineers designing and building the enclosure. Intrinsically safe barriers and complex flame paths require significant design and construction efforts at significant cost. Consequently, electrical control designs have focused on simplified push-buttons and simplified selector switches within explosion proof enclosures. 
     SUMMARY 
     A first aspect of the disclosure is directed to a system comprising an industrial enclosure, a first magnetic control and a second magnetic control. The industrial enclosure has a cover with an outer surface. The second magnetic control is nested within the first magnetic control, and the nested magnetic controls are secured to the outer surface of the cover of the enclosure. 
     Another aspect of the disclosure is directed to a system comprising an industrial enclosure a first rotatable magnetic control, a second rotatable magnetic control, and a plurality of sensors. The industrial enclosure has a cover with an outer surface. The first rotatable magnetic control is configured to emit a first magnetic flux density and the second rotatable magnetic control is configured to emit a second magnetic flux density. The second rotatable magnetic control is nested within the first rotatable magnetic control and the nested controls are secured to the outer surface of the cover of the enclosure. The plurality of sensors are contained within the industrial enclosure and are configured to sense the first and second magnetic flux densities. The sensed magnetic flux densities are representative of a position of the first rotatable magnetic control, the second rotatable magnetic control, or of both the first and second rotatable magnetic controls. 
     Still another aspect of the present disclosure is directed to a system comprising an industrial enclosure, a single-magnet control nested within a dual-magnet control, a sensor, and a programmable controller. The industrial enclosure has a cover with an outer surface. The nested magnetic controls are secured to this outer surface and are configured to emit magnetic flux density. The sensor is configured to sense the magnetic flux density. Further, the sensor is contained within the industrial enclosure and is configured to produce an output representative of the sensed magnetic flux density. The programmable controller is configured to operate on the output of the sensor to determine the position of at least one of the single-magnet control or the dual-magnet control and is configured to initiate a control operation based on the determined position. 
     The above summary is not intended to describe each embodiment or every implementation. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims in conjunction with the accompanying drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an industrial enclosure equipped with nested, magnetic controls according to various embodiments of the disclosure. 
         FIG. 2  is a side view of the body of the industrial enclosure of  FIG. 1 . 
         FIG. 3  is a side view of the cover of the industrial enclosure of  FIG. 1 . 
         FIG. 4  is a cross section of the nested, magnetic controls of  FIG. 1 . 
         FIG. 5  illustrates an example of a circuit board configured to interface with the nested, magnetic controls of  FIG. 1 . 
         FIG. 6  is a flow chart illustrating an example calibration method for the nested, magnetic controls of  FIG. 1   
     
    
    
     The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number. 
     DETAILED DESCRIPTION 
     The present disclosure is directed to nested, magnetic controls that may be implemented in an industrial enclosure. The nested, magnetic controls provide multi-functional operation in a small foot print. When used with an explosion proof enclosure, within a Class I, Division 1 or Division 2 location, the nested, magnetic controls are able to provide significantly more functionality than the simplified, mechanical push-buttons and selector switches currently available for these locations. The multi-functional ability of the nested, magnetic controls increases the usability of the control interface yet requires little modification to the design of the enclosure in which they are implemented. It should be noted that, while the description below refers to example configurations comprising explosion proof enclosures, the nested, magnetic controls of the present disclosure may be implemented within any type of suitable industrial enclosure. 
     Referring to  FIG. 1  an industrial enclosure  100  is equipped with nested, magnetic controls  102  is illustrated. A side view of the body  104  of the industrial enclosure  100  is illustrated in  FIG. 2 . In one example embodiment, the body  104  of the industrial enclosure  100  may comprise a commercially available body such as those provided with the explosion proof EDS/EFS Series Control Stations available from Crouse-Hinds which are typically made of a FERALOY® iron alloy or a copper-free aluminum. The body  104  of the industrial enclosure  100  may vary in size as appropriate to the application. However, by way of example with reference to the EDS/EFS bodies, the dimensions of the body  104  of the enclosure  100  are approximately six inches in height by three and a-half inches in width and two to three inches in depth. 
     The cover  106  of the industrial enclosure  100  comprises a face plate  108  and a flange  109 , where the cover  106  has a depth A, a height B, and width C (see,  FIG. 1 ) that is configured to interface with the body  104  of the enclosure; a side view of the cover  106  is illustrated in  FIG. 3 . A mounting plate  110 , to which the nested, magnetic controls  102  are secured, is attached to the cover  106 . The nested, magnetic controls  102  may be secured to the mounting plate  110  with a series of bolts (not shown) threaded into the cover, or through another appropriate mechanical means. 
     Notably, the mounting plate  110  and the nested, magnetic controls  102  are secured to the industrial enclosure  100  without penetrating the interior walls of the enclosure. In an example where the industrial enclosure  100  is an explosion proof enclosure, the absence of penetration means that no additional design considerations must be given to flame paths. In the conventional design of explosion proof enclosures, all penetrations through the enclosure are considered flame paths. This includes the threads within the cover for the device, and the orifices in the devices for the actuations of shaft assemblies, etc., and even the hubs for connection of electrical conduit. The present design eliminates the flame paths between the enclosure and cover, and within the enclosure, improving safety, ingress protection, and reliability in hazardous environments. 
     In one example embodiment, the face plate  108  and mounting plate  110  are fabricated from a copper-free aluminum while the screws  112  connecting the cover  106  to the body  104 , and connecting the mounting plate  110  to the cover  106 , are stainless steel. In another example embodiment, that of an explosion proof enclosure, the body  104  and the cover  106  each include accurately ground wide flanges for a flame-tight joint. 
     A cross section of the nested, magnetic controls  102 , relative to the cover  106 , is provided in  FIG. 4 . As shown, the nested, magnetic controls  102  generally comprise a magnetized inner dial  114  nested within a magnetized outer dial  116  and a plurality of sensors  118 . The magnetized inner dial  114  comprises a rotatable housing  120  including a diametric cylindrical magnet  122  polarized with a positive (+) and negative (−) side as shown. The magnetized inner dial  114  is configured with a continuous 360 deg. rotational ability and essentially functions as a magnetized potentiometer. In alternative embodiments, the rotatable inner dial  114  may be replaced with a key switch, a push button (a “plunging” control), joystick, or combination there, e.g., a rotatable control that may be pushed down whereby any appropriate inner control (magnetic or non-magnetic) is surrounded by an outer rotatable magnetic control, e.g., magnetized outer dial  116 . 
     The magnetized outer dial  116  comprises a rotatable housing  124  having an outer concentric configuration relative to the magnetized inner dial  114 . The rotatable housing  124  includes two axially magnetized magnets  126   a  and  126   b  having opposite positive (+) and negative (−) polarization as shown. The magnets  126   a  and  126   b  are placed opposite one another within the housing  124 . In one example embodiment, the magnetized outer dial  116  is configured as a selector switch having eight detent enabled positions. Other configurations of the outer magnetized dial  116 , such as continuous 360 degree rotation, greater or lesser number of detents, etc., are also deemed part of the present disclosure. Further, in an alternative embodiment, the sensors  118  configured within the dials  114 ,  166  while the magnets  122 ,  126   a ,  126   b  are in a fixed position below the sensors  118 . The magnets  122 ,  126   a , and  126   b , may comprise, but are not limited to rare earth magnets of Neodymium, Iron and Boron. The magnets  122 ,  126   a ,  126   b , may further include coatings to protect them from the environment. Such coatings may include nickel, copper, tin, zinc, epoxy, silver, gold, or rubber. 
     The sensors  118  are each configured to detect magnetic flux density along three axes, e.g., x-axis, y-axis, and z-axis. In an example embodiment, each of the sensors  118  comprises a TRIAXIS® Magnetometer IC (integrated circuit), e.g., MLX90363, available from Melexis. Suitable to the eight detent switch configuration described above, at least five sensors  118 ( a )- 118 ( e ) are provided and are arranged in a substantially radial configuration as shown in  FIG. 5 . In one example embodiment, the sensors  118 ( a )- 118 ( e ) are mounted to a circuit board  128  that is positioned within the flange  109  depth of the cover  106  such that sensor  118 ( a ) is behind the cover  106  and beneath the magnetized inner dial  114 . Similarly, positioning the circuit board  128  within the flange  109  of the cover  106  places sensors  118 ( b )- 118 ( e ) behind the cover  106  such that they may lie beneath magnets  126 ( a ) and  126 ( b ) of the magnetized outer dial  116 . The circuit board  128  is additionally provided with a programmable controller  130 , e.g., processor, microprocessor, FPGA (field programmable gate array) that is configured to operate on the output signals provided by each of the sensors  118 ( a )- 118 ( e ). The circuit board  128  is powered by a low system voltage (not shown). 
     Notably, only four radially positioned sensors  118 ( b )- 118 ( e ) are necessary for an eight detent position switch as, no matter the switch position, at least one of the magnets  126 ( a ) or  126 ( b ) will be positioned over one of the sensors  118 ( b )- 118 ( e ). Note that the opposite polarity of magnets  126 ( a ) and  126 ( b ) enables one to determine which hemisphere of the magnetic outer dial  116  is over each of the sensors  118 ( b )- 118 ( e ). Of course, a greater number of radially positioned sensors  118  could be used, if desired, at increased cost. When configuring other types of rotatable switches, a lesser or greater number of sensors  118  may be used as appropriate. Further, the switches may include additional positions, which may require additional magnets. Of note is that the number of sensors is substantially less than the number of positions by arrangement of the magnets. 
     To use the nested, magnetic controls  102  within the industrial enclosure  100  as described above, the controls  102  must first be calibrated with the knowledge that the close positioning of the magnets  122 ,  126 ( a ) and  126 ( b ) may create magnetic flux density interference. In an example embodiment, the magnetic interference issue may be dealt with by a data point calibration method  600  illustrated in  FIG. 6 . 
     The calibration  600  begins by setting the magnetic outer dial  116  to detent position  1   602  and the magnetic inner dial  114  to 0 deg.  604 . A query  606  determines if the magnetic inner dial is at a position greater than 360 deg. If not, the position of the magnetic inner dial  114 , the detent position of the magnetic outer dial  116 , as well as the x-axis, y-axis, and z-axis outputs from each of the sensors  118 ( d ) and  118 ( e ) is recorded  606  in a data table within programmable controller  130 . Subsequently, the degree setting of the magnetic inner dial  114  is increased by +5 deg.,  610 , and control is returned to query  606 . 
     If query  606  determines that the degree reading of the magnetic inner dial  114  has surpassed 360 deg., then the position/value of the magnetic inner dial is reset to 0 deg.  612 . Subsequently, query  614  determines if the magnetic outer dial detent setting has surpassed a value of 8. If not, the magnetic outer dial detent setting is increased by one  616  and data related to the inner dial degree setting, the outer dial detent setting, as well as the x-axis, y-axis, and z-axis outputs from each of the sensors  118 ( d ) and  118 ( e ) is recorded  608 . If the query  614  has determined that magnetic outer dial detent setting has surpassed 8, all desired calibration data has been recorded and the calibration process is ended  618 . 
     In one example embodiment, 576 data points are collected that account for measurements at every five degrees for all eight positions of the outer dial  116 , e.g., 72*8=576. Each “data point” actually consists of x, y, and z measurement for the four sensors  118 ( b )- 118 ( e ), providing a total of 6912 pieces of data that may be used in the calibration. 
     In use the magnetic inner dial  114  may be used to change a setting value while the magnetic outer dial  116 , having eight detent positions, may use one or all eight detent positions to select the setting to change. During run-time of the nested, magnetic controls  102 , the programmable controller  130  is configured to perform a look-up in the data from the four sensors. A mean squared error calculation is performed by the programmable controller  130  from the sensor reading for all eight detent positions. The position with the lowest means squared error is considered to be the detent position of the magnetic outer dial  116 . 
     More specifically, the inner dial  114  value is used as an input to a lookup table. The output of the lookup table is a data set consisting of x, y, and z values for all four sensors  118 ( b )- 118 ( e ), for all eight possible sensor positions (96 total values). Note that because the angle of the internal dial  114  affects the values read at the sensors  118 ( b )- 1118 ( e ), the values for the eight possible sensor positions in each of the 5 degree increments of the inner dial  114  are stored. The current values that are being measured are the x, y, and z for the four sensors  118 ( b )- 118 ( e ). The current x of each sensor is compared to the x of the corresponding sensor from the data set (for the current inner dial position), which gives 32 different error values (4 sensors times 8 positions). The same operation is performed on y and z, for a total of 96 error values. The 12 error values per outer dial position (x, y, and z, for sensors  118 ( b )- 118 ( e )) are each squared, and an average is taken, resulting in a single positive value per outer dial position. The position that has the lowest error value is selected as the current position. 
     An example equation for calculating the mean squared error for an x-axis reading is provided below in Equation (1). Similar equations are used for y and z readings. 
     
       
         
           
             
               
                 
                   
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     Once the detent position of the magnetic outer dial  116  is determined the operation assigned to the detent position may be activated/initiated by an output from the controller  130 . 
     Of course different calibration methods and different run-time switch position determination methods that are known to those in the art, e.g., neural nets, baeysian classifiers, etc., may be used in place of the above-described data point calibration method and mean squared error switch position determination method, and are deemed part of the present disclosure. 
     The above-described nested, magnetic controls for an industrial enclosure provide the user with multi-functional controls in a small footprint. With regard to explosion proof industrial enclosures, the nested, magnetic controls provide significantly more and complex interface options than has previously been available in Class I, Division 1 and Division 2 locations. Numbers of explosion proof enclosures utilizing simplified, one-action (e.g., push button, rocker switch) controls may now be replaced with a single explosion proof enclosure incorporating nested, magnetic controls. 
     Systems, devices or methods disclosed herein may include one or more of the features, structures, methods, or combination thereof described herein. For example, a device or method may be implemented to include one or more of the features and/or processes above. It is intended that such device or method need not include all of the features and/or processes described herein, but may be implemented to include selected features and/or processes that provide useful structures and/or functionality. 
     Various modifications and additions can be made to the disclosed embodiments discussed above. Accordingly, the scope of the present disclosure should not be limited by the particular embodiments described above, but should be defined only by the claims set forth below and equivalents thereof.