Abstract:
A mounting assembly for fastening a device housing onto a panel includes a housing and a clamp. The panel defines a front surface, a rear surface, and an opening extending therethrough for receiving the housing. The housing includes at least one wall sized to extend through the opening. The wall defines a bearing surface. The clamp includes a beam member and a head member. The beam member extends from the wall at a first end. The beam member is biased to deflect outwardly with respect to the wall at an oblique angle. The head member extends from a second end of the beam member and includes a first cam surface for engaging the rear surface of the panel and a second cam surface for engaging the bearing surface of the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable 
   BACKGROUND OF THE INVENTION 
   The present invention relates generally to industrial control systems, and, in particular, to a method and apparatus for mounting a device onto a panel. 
   An automated manufacturing assembly typically includes a set of mechanical and electrical components and one or more panel mount devices that allow a factory worker or operator to monitor or control the automated assembly. The mechanical and electrical components are integrated together to perform an automated manufacturing process. The controller is linked to a sub-set of the components (e.g., sensors) for receiving information regarding progression of the process and to another sub-set of the components (e.g., motors, actuators, etc.) for controlling progression of the process. A human-machine interface (HMI) is typically linked to the controller to facilitate either altering the process parameters or monitoring the process. In particular, the interface generally includes an output terminal, such as a display, that provides data to the user that is relevant to the controlled process. Likewise, one or more input devices, such as a touch screen or keypad, are typically provided so that a user can transmit information over the network to, for instance, the controller or controlled device. 
   While many different types of communication systems have been developed for linking the controller to the assembly components and to the interface, one particularly useful type of linkage is a network communication system, the Ethernet being an example. In the case of the Ethernet, for instance, an interface generates messages earmarked for the controller and transmits those messages onto the network. The controller listens on the network for messages earmarked for the controller and uses those messages to perform specific functions. Similarly, the controller earmarks specific messages for the interface and transmits those messages to the interface via the network. 
   Panel mount devices with operator interfaces are typically mounted onto a panel having a front surface that faces the operator, and a rear surface that is generally inaccessible during normal operation. An opening is provided in the panel that receives the interface from the front. The interface is thus fastened to the panel at the rear panel surface. When mounting the interface, the rear of the panel is difficult to access and not visible by the installer or panel builder when stationed in front of the panel. In some instances, the rear panel surface can be accessed by the installer. However, accessing the rear panel surface in order to mount an interface can be tedious and time-consuming, especially when mounting a plurality of interfaces onto a panel. 
   Accordingly, conventional mounting assemblies enable an installer stationed in front of the panel to mount the interface on a blind rear panel surface. For instance, one typical mounting assembly includes a screw or other rotatable fastener that extends inwardly from the rear of the interface towards the rear surface of the panel that can be rotated until the fastener abuts the rear panel surface. Such fasteners must first be positioned in a threaded aperture, and are further ergonomically unfriendly to the installer. Furthermore, when the fastener is rotated by the installer, the fasteners will likely be blind to the installer who is stationed at the front of the panel. As a result, under-rotation can compromise the mounting stability, while over-rotation can place excessive stresses on the fastening parts which can wear and fail over time. Other mounting assemblies require multiple installers, positioned at the front and rear of the panel. 
   Additionally, many panel mount industrial controls are typically made using polymeric materials which may deform over time, especially at the elevated temperatures typical of an industrial environment. As a result, the mounting mechanism for the panel mount device must be robust to long term temperature variation and may also be required to protect the interior of the panel from ingress of various fluids common to industrial environments. 
   What is therefore needed is a method and apparatus that facilitates mounting an industrial control device onto a panel in a less tedious and more reliable manner than conventionally achieved. The apparatus should provide the mechanical stability necessary to withstand the industrial environment and should facilitate an environmental seal that can be certified to various standards commonly accepted in the industry. 
   This section of this document is intended to introduce various aspects of art that may be related to various aspects of the present invention described and/or claimed below. This section provides background information to facilitate a better understanding of the various aspects of the present invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art. 
   BRIEF SUMMARY OF THE INVENTION 
   One aspect of the present invention is seen in a mounting assembly for fastening a device housing onto a panel including a housing and a clamp. The panel defines a front surface, a rear surface, and an opening extending therethrough for receiving the housing. The housing includes at least one wall sized to extend through the opening. The wall defines a bearing surface. The clamp includes a beam member and a head member. The beam member extends from the wall at a first end. The beam member is biased to deflect outwardly with respect to the wall at an oblique angle. The head member extends from a second end of the beam member and includes a first cam surface for engaging the rear surface of the panel and a second cam surface for engaging the bearing surface of the housing. 
   Another aspect of the present invention is seen in a method for fastening an industrial control device housing onto a panel. The panel defines a front surface, a rear surface, and an opening extending therethrough for receiving the housing. The method comprises providing a housing including at least one wall sized to extend through the opening and defining a bearing surface, and a clamp including a beam member extending from the wall at a first end. The beam member is biased to deflect outwardly with respect to the wall at an oblique angle. A head member extends from a second end of the beam member. The head member includes a first cam surface for engaging the rear surface of the panel and a second cam surface for engaging the bearing member. The housing is inserted through the opening thereby deflecting the beam member inwardly toward the side wall until a first position at which the first cam surface abuts the rear surface of the panel. The housing is further inserted through the opening to allow outward deflection of the beam member to engage the first cam surface with the rear surface of the panel and the second cam surface with the bearing member. 
   These and other objects, advantages and aspects of the invention will become apparent from the following description. The particular objects and advantages described herein may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made, therefore, to the claims herein for interpreting the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
       FIG. 1  is a simplified block diagram of an industrial control system; 
       FIGS. 2 ,  3 , and  4  are front isometric, rear isometric, and top views of a panel mount industrial control device with a human machine interface employed in the system of  FIG. 1 , respectively; 
       FIGS. 5 through 7  are partial cross-section views of a panel clamp on the HMI of  FIG. 2  in various stages of engagement with the panel; 
       FIG. 8  is a rear isometric view of the industrial control device disengaged from the panel; and 
       FIG. 9  is a partial cross-section view of alternative embodiment of the panel clamp including a latch for disengaging the panel clamp to allow removal of the HMI from the panel. 
   

   While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
   DETAILED DESCRIPTION OF THE INVENTION 
   One or more specific embodiments of the present invention will be described below. It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. Nothing in this application is considered critical or essential to the present invention unless explicitly indicated as being “critical” or “essential.” 
   Referring now to the drawings wherein like reference numbers correspond to similar components throughout the several views and, specifically, referring to  FIG. 1 , the present invention shall be described in the context of an industrial control system  10  used for industrial automation. It should be appreciated that the industrial control system  10  is provided only as an example of one of a multitude of systems that can incorporate a human-machine interface (HMI), and that the present invention is not limited to the example described herein. Moreover, the panel mounting structures described herein are not limited to HMI applications. For example, other panel mounted equipment, such as sensors, displays, controls, etc. may also incorporate the panel mounting features described herein. 
   Generally, the industrial control system  10  includes a programmable logic controller (PLC)  15 , a programming terminal  20 , a human-machine interface (HMI)  25 , an I/O module  30 , sensors  35 , actuators  40 , and a communication medium  45 . The programming terminal  20  allows the configuring, modifying, debugging and maintaining of the industrial control system  10 . The HMI  25  provides an operator interface for operating the industrial control system  10  to perform an automated industrial process. The I/O module  30  provides an interface to the sensors  35  and actuators  40 . The sensors  35  can sense items such as temperature, pressure, flow rate of a fluid, torque, electrical current, etc. The actuators  40  control items such as motors, switches, and valves associated with robotic systems, fans, beaters, pumps, and the like. 
   The communication medium  45  may take the form of a cable, and may also include repeaters, routers, bridges, and gateways. A suitable communication medium  45  is the ControlNet™ network offered by Rockwell Automation, Inc., of Milwaukee, Wis. ControlNet™ is a high-speed, deterministic, scheduled network for the transmission of time-critical application information. 
   Referring now to  FIGS. 2–4 , an exemplary HMI  25  mounted to a panel  50  having front and rear surfaces  52 ,  54 , respectively, is illustrated. The exemplary HMI  25  includes a housing  55  supporting the internal components of the HMI  25  (e.g., memory, processor, network interface, etc.) and a front bezel  60 . The front bezel  60  supports a display  65 , a navigation keypad  70 , and a function keypad  75 . Of course other arrangements and interface devices may be used. For example, alternative input interfaces (e.g., alphanumeric keypad, touch sensitive screen, trackball, stylus, etc.) or alternative output devices (e.g., speaker, indicator lights, meters, etc.) may be supported by the bezel  60 . In the illustrated embodiment, the housing  55  and bezel  60  are formed of a plastic material, however, other materials, such as metal, may also be used. 
   The HMI  25  is installed by a panel builder or installer from the front of the panel  50  by inserting the housing  55  through an opening defined therein. The installer need not have access to the rear surface  54  of the panel  50  during installation, and only one individual is required to complete the installation. 
   The housing  55  includes side walls  80 , end walls  85 , a rear cover  90 , and panel clamps  95  that engage the panel  50  to secure the HMI  25  thereto. One or more apertures  100  extend through the housing  55  to provide a plurality of vents that enable cooling air to travel across the HMI  25 . Other apertures  102  of various shapes and sizes may be provided to allow power or data connections to be made with the HMI  25 . The bezel  60  defines a rim  104  that extends beyond an outer periphery defined by the side walls  80  and end walls  85  of the housing  55 . The number and arrangement of panel clamps  95  may vary depending on the particular application (e.g., based on the size of the HMI  25 ). In the illustrated embodiment, one panel clamp  95  is defined along each end wall  85 . In other embodiments, multiple panel clamps  95  may be defined for each end wall  85  and/or additional panel clamps  95  may be defined along the side walls  80 . 
   In the illustrated embodiment, the end walls  85  are defined by a first portion  96  extending from the rear cover  90  and a second portion  98  extending from the bezel  60 . The application of the present invention is not limited to this two-part construction. For example, a unitary construction may be used where the housing is formed as a single part. Also, if a two-part construction is used, the positioning of the interface between the bezel  60  and the end cover  90  may vary. For instance, the entire end wall  85  may be defined by either the end cover  90  or the bezel  60 . Hence, the end wall  85  is defined in the housing  55 , regardless of whether the housing  55  is formed of one, two, or more interfacing parts. 
   Referring to  FIG. 5 , a cutaway cross-section view of the HMI  25  engaged with the panel  50  is shown. A compressible gasket  105  is disposed on a rear surface  110  of the bezel  60  along the rim  104  to provide an environmental seal between the HMI  25  and the front surface  52  of the panel  50 . When mounted, the gasket  105  provides a seal against the panel  50  that prevents the ingress of fluids or dust at the interface between the panel  50  and the housing  55 , complying with the NEMA 4X standard for an environmental seal. 
     FIGS. 6 and 7  illustrate the panel clamp  95  in various stages of engagement with the panel  50 , and  FIG. 5  illustrates the panel clamp  95  in a fully engaged position.  FIG. 8  illustrates the housing disengaged from the panel  50 . The panel clamps  95  are spring loaded and self-actuating. In the illustrated embodiment, the spring nature of the panel clamps  95  results from them being formed from a cantilevered beam  115  extending from the housing  55  at one end  117 . The cantilevered beam  115  extends outwardly with respect to the end walls  85  when in a non-deflected disengaged position, as illustrated in  FIG. 6 . The panel clamp  95  further includes a head  118  having a first arcuate cam surface  120  extending from a second end of the cantilevered beam  115  and having a plurality of teeth  125  defined along the cam surface  120 . A second arcuate cam surface  126  is present on the head member  119  opposite the cam surface  120  that engages with a bearing surface  127  defined in the end wall  85  (i.e., either by bezel  60  or the end cover  90 ). 
   Of course, alternative arrangements may be provided for biasing the panel clamps  95  in an outwardly deflecting position. For example, a hinge formed at the intersection of the beam  115  and the housing  55  may allow rotation of the beam  115  and an associated leaf spring may be provided to outwardly bias the beam  115 . A lip  128  may be provided on the head  118  for limiting the outward deflection of the beam  115 . The lip  128  defined on the head  118  serves as a stop surface that engages the end wall  85  to prevent further outward rotation of the panel clamp  95  that may damage the beam  115  by deforming it such that is loses its spring nature. 
   The cam surface  126  and bearing surface  127  engage such that the interference between the cam surface  126  and the bearing surface  127  increases as the panel clamp  95  is deflected inwardly. This interference provides an additional deflection resisting force that further urges the head  118  of the panel clamp  95  to its undeflected position. 
   Referring to  FIG. 6 , as the housing  55  is inserted through an opening in the panel  50 , the edge  130  of the panel  50  deflects the cantilevered beam  115  inwardly. This inward deflection increases until the cantilevered beam  115  is nearly parallel with the end wall  85  (i.e., assuming the size of the opening in the panel  50  corresponds to the size of the housing  55 ), as shown in  FIG. 7 . 
   Returning to  FIG. 5 , as the housing  55  is inserted further than the length of the cantilevered beam  115 , the cam surface  120  engages the rear surface  54  of the panel  50  as the beam  115  and head  118  return toward their undeflected positions. The spring nature of the cantilevered beam  115  and the interference between the cam surface  126  and the bearing surface  127  aid in this return. As the housing  55  is inserted further into the opening, subsequent teeth  125  engage the panel  50 , and the beam  115  continues to spring outwardly. The particular tooth  125  that engages the rear surface  54  when the housing  55  is fully inserted depends on the height of the teeth  125 , the thickness of the panel  50 , and the compressibility of the gasket  105 . Although the teeth  125  are shown as having uniform height displacements between adjacent teeth  125 , it is contemplated that the height displacements may vary along the length of the cam surface  120 . For example, the height displacement may decrease for the teeth  125  disposed furthest from the beam  115  to allow finer step adjustments in the region of the cam surface  120  likely to be in contact with the panel  50  when the gasket  105  is in a compressed state. 
   When the gasket  105  engages the front surface  52  of the panel  50 , and the installer continues to exert an insertion force, the gasket  105  will compress, thereby allowing further outward rotation of the head  118  of the panel clamp  95  and the engagement of another tooth  125  along the cam surface  120 . Assuming the compressibility of the gasket  105  is greater than or equal to the height of one tooth  125 , at least one additional tooth  125  will be engaged when the installer inserts the housing  55  and compresses the gasket  105  until the rear surface  110  of the bezel  60  touches or nearly touches the front surface  52  of the panel  50 . Hence, when the insertion force is removed, the gasket  105  will remain in compression, thereby providing an environmental seal. As seen by comparing  FIGS. 5 and 6 , the gasket  105  is in compression when the housing  55  is fully inserted. 
   The force generated by the compressed gasket  105  further urges the cam surface  126  on the head  118  to engage the bearing surface  127 , thereby creating a load path  129  that extends through the end wall  85  which defines the bearing surface  127 , head  118 , panel  50 , gasket  105 , and bezel  60 . The load between the head  118  and the panel  50 , which keeps the integrity of the environmental seal created by the gasket  105 , is transferred along the load path  129 , thereby removing the load from the beam member  115 . Without the interaction between the cam surface  126  and the bearing surface  127  to create the load path  129 , the load would be borne entirely by the beam member  115 . This loading, over time and temperature variation, could cause a weakening or deformation of the beam member  115 , thereby compromising the integrity of the environmental seal. 
   Hence, the HMI  25  may be easily installed by a single individual present at the front of the panel  50  without requiring access to the rear surface  54 . The installer simply inserts the housing  55  and continue to provide an insertion force until the bezel  60  touches the front surface  52  of the panel  50  or the gasket  105  is fully compressed. The heads  118  of the spring clamps  95  will rotate outwardly as the teeth  125  of the cam surface  120  engage the panel  50 . When the insertion force is removed, the HMI  25  is secured to the panel  50  with the sealing gasket  105  in compression. The installation of the HMI  25  may be performed in seconds, as compared to the previous mounting techniques which took considerably longer and sometimes required multiple individuals. 
   Turning now to  FIG. 9 , an alternative embodiment of the panel clamp  95  that includes a depanelization latch  135  is provided. The latch  135  facilitates removal of the HMI  25  from the panel  50 . As described above and shown in  FIG. 7 , the maximum inward deflection of the beam  115  of the panel clamp  95  during insertion of the housing  55  is such that the beam  115  is parallel to the end wall  85 . The beam  115  would be parallel if the opening in the panel  50  exactly matched the dimensions of the housing  55 . If the panel opening were to be larger than the dimensions of the housing  55 , the deflection would be less than parallel. 
   As seen in  FIG. 9 , a first tab  140  is defined on the head  118  of the panel clamp  95  and a second tab  145  is defined on the housing  55  (e.g., extending from the bezel  60  or defined in the end wall  85 ). Removal of the HMI  25  requires access to the rear surface  54  of the panel  50  to allow the disengaging of the panel clamps  95 . An installer deflects the panel clamp  95  inwardly past the parallel position such that the tab  140  on the panel clamp  95  engages the tab  145  on the housing  55  and retains the panel clamp  95  in a disengaged position. When all of the panel clamps  95  have been disengaged, the HMI  25  may be extracted from the front of the panel. Hence, only one individual is required for removing the HMI  25  from the panel  50 . 
   The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.