Patent Publication Number: US-8115099-B2

Title: Industrial automation input output module with elastomeric sealing

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. application Ser. No. 11/824,987 filed Jul. 3, 2007 now U.S. Pat. No. 7,503,790, and said prior application Ser. No. 11/824,987 is hereby expressly incorporated by reference into the present specification. 
    
    
     FIELD 
     The present development relates to an industrial automation input output module for a distributed input output system that is highly resistant to ingress of water, oil, debris, dirt and other contaminants encountered in manufacturing and other environments without use of a potting compound. An industrial automation input output module formed in accordance with the present development meets ingress protection standards such as IP69/IP67. 
     BACKGROUND 
       FIG. 1  illustrates a known industrial automation input output module  100  comprising a housing  102  constructed from inner and outer housing members  102   a , 102   b  that are inter-fitted with each other to define an enclosed interior space  104  in which one or more electronic circuit boards  106  is/are located. The inner and outer housing members  102   a , 102   b  are each preferably defined as one-piece molded polymeric constructions utilizing any of a wide variety of polymeric materials in an injection molding process. One suitable material is glass-filled polyester, although it is not intended that the development be limited to such material or any other material. One or more connectors  108  are operably connected to the circuit board  106  and project through a top face  110  of the outer housing member  102   b  so as to be adapted for mating with corresponding cable connectors from external input output devices or the like. The circuit boards  106  and connectors  108  are adapted for any desired electrical application such as input and output to/from an industrial process. A module  100  typically comprises a plurality of visual indicators such as light emitting diodes operably connected to a circuit board  106  and that provide visual output signals concerning the state of the circuitry  106  in the module  100  and/or flow of data or power or other signals. A light pipe includes lenses  114  that are aligned with and/or project through respective openings  116  in the top face  110  of the outer housing member  102   b  or other location of the housing  102  to communicate light from the LED&#39;s outside of the module  100 . 
     The connectors  108 , light pipe lenses  114  and any other openings in the outer housing member  102   b  are sealed against ingress of water, dirt or other contaminants to the interior space  104  using a potting compound PT that is applied into the outer housing member  102   b  after the various components such as the connectors and light pipe are installed. Often, multiple layers of potting compound PT are used and installed/cured in stages as components are correspondingly added in stages. 
     Potting compound PT is also used to seal the connection between the inner and outer housing members  102   a , 102   b . In the illustrated example of  FIG. 1 , it can be seen that the inner housing member  102   a  is adapted for nesting within the outer housing member  102   b  and comprises a plurality of tabs  102 T that are received in corresponding recesses  102 R such as notches, or apertures defined by the outer housing member  102   b  so that the housing members  102   a , 102   b  are mechanically interlocked with a close snap-fit. Furthermore, the inner housing member  102   a  comprises a continuous peripheral wall  102 W projecting outwardly therefrom that is received within a corresponding continuously extending peripheral groove  102 G defined by the outer housing member  102   b . The joint at the junction of the wall  102 W and groove  102 G is sealed with the potting compound PT. 
     Despite widespread commercial success, the module  100  of  FIG. 1  has various drawbacks relating to the use of potting compound PT to provide the requisite ingress protection. Potted products cannot be disassembled and repaired. A batch of defective modules  100  must be discarded even if only a single component of each module is defective. Assembled modules  100  that are potted cannot be disassembled and reconfigured. The potting compound PT must be cured by passage of time and/or application of heat, neither of which is desirable in a manufacturing system. The potting compound PT is dense and adds significant weight to the product. The presence of potting compound PT also prevents recycling of the module  100 . 
     With these and other concerns in mind, an industrial automation input output module with elastomeric sealing, and a method of constructing same, have been developed and are disclosed herein according to the present invention. 
     SUMMARY 
     In accordance with one aspect of the present development, an industrial automation input output module includes an outer housing member with a top housing wall and an outer peripheral housing wall. The top housing wall and the outer peripheral housing wall define an open recess. The outer housing member further includes an inner peripheral housing wall spaced from the outer peripheral housing wall. A groove is defined between the inner peripheral housing wall and the outer peripheral housing wall. An inner housing member is received in the open recess of the outer housing member so that the inner and outer housing members together define an interior space for containing at least one circuit board. The inner housing member includes a projecting seal engagement wall that is received in the groove. A one-piece elastomeric main seal is installed adjacent the groove. The main seal includes: (i) a lateral seal portion that provides a fluid-tight seal between an inner face of said seal engagement wall and the inner peripheral housing wall; and, (ii) a face seal portion located in the groove that provides a fluid-tight seal between a tip of the seal engagement wall and the outer housing member. 
     In accordance with another aspect of the present development, the industrial automation input output module further includes a visual indicator adjacent a visual indicator opening in the top housing wall. The one-piece elastomeric main seal further includes a light-pipe portion including a translucent light pipe adapted to communicate light from a light source located in the interior space of the module to the visual indicator opening. 
     In accordance with another aspect of the present development, an elastomeric seal comprises a one-piece body including a seal portion and a light pipe portion, said seal portion including a plurality of linear segments and a plurality of corners located respectively between the linear segments, wherein the linear segments and the corners define the main seal to have an open central portion. The light pipe portion includes a translucent light pipe having an inner end and an outer end, and the light pipe is adapted to communicate light from the inner end to the outer end thereof. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an isometric, partially sectioned view of a known industrial automation input output module; 
         FIG. 2  is similar to  FIG. 1  and provides an isometric view of an industrial automation input output module with elastomeric sealing formed in accordance with the present invention; 
         FIG. 3  is an isometric view of the bottom or open side of the outer housing member of the industrial automation input output module of  FIG. 2 , with internal components removed to review the elastomeric seal and sealed connectors; 
         FIGS. 4A and 4B  are lower and upper side isometric views of an elastomeric seal formed in accordance with the present invention and used in the module of  FIG. 2 ; 
         FIG. 5  is a sectional view of the elastomeric seal as taken at location  5 - 5  of  FIG. 4A ; 
         FIG. 6  is a sectional view of the outer housing member and installed elastomeric seal as taken at location  6 - 6  of  FIG. 3 ; 
         FIG. 7  is a section view of the outer housing member and installed elastomeric seal as taken at location  7 - 7  of  FIG. 3 , and also shows the inner housing member and an installed circuit board including LED&#39;s; 
         FIG. 8  illustrates a connector installed into the outer housing member using an o-ring seal and a torsion resistant connection in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 2  shows an industrial automation input output module  10  that corresponds in terms of structure to the module  100  of  FIG. 1 , except that the potting compound PT of the module  100  of  FIG. 1  is eliminated and replaced with a one-piece elastomeric seal  30  in accordance with the present invention. In some cases, the one or more connectors  18  of the module  10  are sealed to the housing with O-rings or other elastomeric seals, depending on the type of connector. 
     Similar to the module  100 , the module  10  comprises a housing  12  constructed from inner and outer housing members  12   a , 12   b  that are inter-fitted with each other to define an enclosed interior space  14  in which one or more electronic circuit boards  16  is/are located. The inner and outer housing members  12   a , 12   b  are each preferably defined as one-piece molded polymeric constructions utilizing any of a wide variety of polymeric materials in an injection molding process. One suitable material is glass-filled polyester, although it is not intended that the development be limited to such material or any other material. The connectors  18  are operably connected to a circuit board  16  and project through a top wall  11  of the outer housing member  12   b  so as to be adapted for mating with corresponding cable connectors from external input output devices or the like. The circuit boards  16  and connectors  18  are adapted for any desired electrical application such as input and output to/from an industrial process. The module  10  comprises a plurality of visual indicators  24  that project through corresponding openings  26  in the outer housing member  12   b  that provide visual output signals concerning the state of the circuitry  16  in the module  10  and/or flow of data or power or other signals. 
     The housing member  12  is sealed against ingress of water, dirt or other contaminants using a main elastomeric seal  30  located between the inner and outer housing members  12   a , 12   b , and an elastomeric seal for each connector  18 . As described herein, the visual indicators  24  are also sealed relative to the openings  26  in the outer housing member  12   b , but remain visible outside of the housing member  12 . As can be seen in  FIG. 2 , the inner housing member  12   a  is adapted for nesting within the outer housing member  12   b  and comprises a plurality of tabs  12 T that are received in corresponding recesses  12 R such as notches, or apertures defined by the outer housing member  12   b  so that the housing members  12   a , 12   b  are mechanically interlocked with a close snap-fit without requiring use of screws or other fasteners. The inner housing member  12   a  comprises a continuous peripheral wall  12 W projecting outwardly therefrom that is received within a corresponding continuously extending peripheral groove  12 G defined by the outer housing member  12   b . According to the present invention, and unlike the known module  100  that uses potting compound, the joint at the junction of the wall  12 W and groove  12 G of the module  10  is sealed with the main elastomeric seal  30  to prevent ingress of water, dirt, and other contaminants at the interface between the wall  12 W and groove  12 G. As such, the wall  12 W is sometimes referred to herein as a “seal engagement wall.” 
       FIG. 3  shows the outer housing member  12   b  by itself in an inverted state and with the circuit board(s)  16  and other components removed so that it can be seen that the outer housing member includes an open recess  20  defined by the top wall  11  and a plurality of side walls  22   a , 22   b , 22   c , 22   d  that project outwardly from the top wall  11  and that are connected to each other by corners  23   a , 23   b , 23   c , 23   d  so as to define a continuous outer peripheral wall structure  22 . As described in full detail below, the connectors  18  project through respective openings  19  in the top wall  11  and are sealed using respective connector seals  70  (see  FIG. 8 ). The groove  12 G is defined between an inner face of the peripheral wall  22  and a correspondingly shaped but shorter second or inner wall  24  that is spaced inward from the peripheral wall  22  (see also  FIG. 6 ). As shown in  FIG. 6 , this inner wall  24  comprises an outer edge  24   a  and first and second opposite faces  24   b , 24   c  and thus defines a mounting location for the main elastomeric seal  30 . 
     The main elastomeric seal  30 , itself, is shown in  FIGS. 4A ,  4 B, and  5  and comprises a one-piece molded elastomeric body defined from a suitable elastomer such as DuPont™ Vamac® (ethylene acrylic elastomer (AEM) or a commercial grade silicone or any other compressible, resilient elastomeric composition suitable for seals (that is preferably also clear or at least translucent for light piping capability as disclosed below). The seal  30  is dimensioned and conformed so as to be adapted to seal the groove  12 G of the outer housing member  12   b , i.e., to seal the space between the seal engaging wall  12 W of the inner housing member  12   a  and the groove  12 G of the outer housing member  12   b . Typically, as shown herein, the seal  30  defines an overall rectangular shape comprising four linear segments  32   a , 32   b , 32   c , 32   d  connected by corners  33   a , 33   b , 33   c , 33   d . The linear segments  32   a - 32   d  and corners  33   a - 33   d  preferably define an open central portion O of the seal  30  therebetween to reduce material usage and to minimize the likelihood that the seal  30  will interfere with other components of the module  10 , e.g., the connectors  18 . 
     As is shown in  FIG. 5 , the linear segments  32   a - 32   d  and corners  33   a , 33   d  are defined by spaced apart inner and outer walls  34   a , 34   b  that are interconnected by an end wall  34   c , wherein the inner and outer walls  34   a , 34   b  and end wall  34   c  define a U-shaped wall receiving structure adapted for close sliding receipt of the inner wall  24  of the outer housing member  12   b  as shown in  FIG. 6 , with the interface between the housing wall  24  and the seal walls  34   a , 34   b  being smooth and planar over at least a substantial portion of both opposite faces  24   a , 24   b  of the wall  24 . 
     The outer seal wall  34   b , located adjacent the groove  12 G, comprises an outer face  36  that provides a lateral seal portion SL. This outer face  36  preferably defines one or more sealing ribs  36   r  that extend parallel to the outer and inner walls  22 , 24  and parallel to the groove  12 G. The sealing ribs  36   r  preferably define a saw-tooth cross-section, with a ramp surface  36   a  that diverges from the seal wall  34   b  as it extends away from the end wall  34   c , which facilitates insertion of the seal engagement wall  12 W of the inner housing member into the groove  12 G when the module  10  is assembled and which also tends to improve sealing in response to any fluid pressure being exerted on the ribs  36   r  toward the interior space  14  of the module  10 . The sealing ribs  36   r  engage and are compressed by an inner surface  12 Wi of the wall  12 W when the wall  12 W is inserted in the groove  12 G as shown in  FIG. 7 . 
     With continuing reference to  FIGS. 5-7 , the seal  30  further comprises a face seal portion SF defined by a lip  38  that projects transversely outward from the seal outer wall  34   b  away from the inner wall  34   a  at a location spaced from the end wall  34   c  so as to be located in the groove  12 G, in abutment with an inner wall  12 Gi of the groove that extends between and interconnects the walls  22 , 24  of the outer housing member  12   b . The lip  38  of the face seal portion SF defines an outwardly facing recess  38   r  that opens upwardly away from the inner wall  12 Gi of the groove  12 G so as to be adapted for receipt of a tip  12 Wt of the wall  12 W of the inner housing portion  12   a  when the inner and outer housing portions  12   a , 12   b  are inter-fitted to define the module housing  12  as shown in  FIG. 7 . At least at each of the corners  33   a - 33   d  of the seal, the lip  38  further comprises an upwardly projecting tab  38   t  that projects upwardly away from the recess  38   r  at a location spaced from the seal outer wall  34   b . The seal engagement wall  12 W of the inner housing member  12   a  is received between the seal outer wall  34   b  and each tab  38   t , and the tabs  38   t  ensure a fluid-tight seal between the corners  23   a , 23   b , 23   c , 23   d  of the outer housing wall  22  and the corresponding adjacent corners of the seal engagement wall  12 W of the inner housing  12   a  when the inner housing  12   a  is installed in the outer housing  12   b . As such, the tabs  38   t  ensure a fluid-tight seal at the corners  23   a - 23   d  which can otherwise be prone to leaks. 
     The main elastomeric seal  30  preferably includes at least one integral light-pipe portion  50  as part of its one-piece construction. With particular reference to  FIGS. 4A ,  4 B and  7 , the light pipe portion  50  is defined as part of the one-piece seal construction from the same material and comprises at least one light pipe  52  which is transparent or at least translucent, depending upon the material from which the seal  30  is defined. As shown herein, a base wall  54  is connected to the seal inner wall  34   a  and extends transversely inward toward a center of the seal  30 , and each light pipe  52  is connected to the base wall  54 . As shown, the seal  30  comprises two light pipe portions  50   a , 50   b  of like construction located on opposite sides of the seal opening O, each comprising a plurality of light pipes  52 . 
     Each light pipe  52  is adapted to communicate light from a light source such as an LED or other light source located inside the space  14  of the module  10  to a location adjacent one of the visual indicator openings  26  of the outer housing member  12   b . More particularly, as shown in  FIG. 7 , each light pipe  52  comprises an inner end  52   a  and an outer end  52   b . The inner end  52   a  is adapted to be positioned in abutment with or otherwise adjacent an LED or other light source  56  connected to a circuit board  16  or other location in the module  10 . The outer end  52   b  is adapted to be located adjacent and tightly received in one of the visual indicator openings  26  of the outer housing member  12   b  and preferably project entirely through the opening  26  so that the outer end  52   b  defines the visual indicator  24 , while a fluid-tight seal is maintained between the light pipe  52  and the outer housing member  12   b . As shown, each visual indicator opening  26  is surrounded by a respective visual indicator boss  26   b  that is part of the outer housing member  12   b  and that includes a cylindrical inner surface. The outer end  52   b  of each light pipe comprises one or more radially projecting sealing ribs  57  that engage the corresponding visual indicator boss  26   b  with a fluid-tight fit as shown in  FIG. 7  (note that in  FIG. 7 , the ribs  57  are shown in broken lines to indicate that they are compressed between the light pipe  52  and the visual indicator boss  26   b . As also shown in  FIG. 7 , it is most preferred that each light pipe  52  comprise a hollow tube structure including a bore  53  closed at the outer end  52   b  but otherwise open from the closed end  52   b  to and through the inner end  52   a . The open, tubular bore  53  of the light pipe maximizes communication of light from the light source  54  to the closed outer end  52   b  of the light pipe, whereas a solid mass of the elastomeric seal material would lead to light losses, scattering and/or dissipation. The bore  53  also facilitates injection molding of the one-piece main seal  30 . The main seal  30 , including the light pipe portion  50  can alternatively be made integral to the outer housing member  12   b  using a transfer or insert molding process, in which the main seal  30  becomes permanently bonded to and/or defined as part of the outer housing member  12   b.    
     As noted, one or more connectors  18  project through respective openings  19  in the outer housing member  12   b  as shown in  FIGS. 2 and 3 . As such, each connector  18  must be sealingly engaged with the outer housing member  12   b  to prevent ingress of water and other contaminants to the interior space  14  between the connector  18  and outer housing member  12   b  as required by the IP65/IP67 or other comparable standard. As such, each connector  18  is sealed to the outer housing member  12   b  using an O-ring or like seal  70  as shown in  FIG. 8 . In particular, the top wall  11  of the outer housing member  12   b  includes one or more connector mounting locations  60  corresponding in number to the number of connectors  18  for the module  10 . Each connector mounting location  60  is defined by a connector opening  19  in the top wall  11 , an outer boss  62  that projects from an outer surface  11   a  of the top wall and that encircles the opening  19 , and an inner boss  64  that also encircles the opening  19  but projects from an opposite inner surface  11   b  of the top wall  11  into the open recess  20  of the outer housing member  12   b . The outer and inner bosses  62 , 64  each comprise a cylindrical inner surface. 
     The connector  18  is inserted into the connector mounting location  60 , from inside the open recess  20  of the outer housing member  12   b , so that the connector extends through the opening  19  with an outer portion  18   a  of the connector tightly fit into the outer boss  62  and an inner portion  18   b  of the connector tightly fit into the inner boss  64 . The inner portion  18   b  of the connector comprises an elastomeric O-ring seal  70  seated in a circumferential groove  72 , and the seal  70  engages the inner boss  64  with a fluid-tight fit. The connectors  18  are typically metallic and can be any of a wide variety of well known connectors. As shown, the connectors  18  adapted for threaded connection with a mating cable connector and, as such, each comprise an internally threaded portion  18   t . Because the connectors  18  are subjected to torsional stresses during threaded connection/disconnection of an associated cable, each connector  18  includes means for preventing rotation of the connector relative to the connector mounting location  60 . As shown, the outer portion  18   a  of each connector includes a plurality of vertical or otherwise configured ribs  18   r  so that a knurled outer surface is defined which frictionally engages the outer cylindrical boss  62  to inhibit rotation of the connector  18 . It is preferred that the knurled outer surface defined by the ribs  18   r  be bonded to the outer cylindrical boss, e.g., by ultrasonic welding or an adhesive or the like. 
     The invention has been described with reference to preferred embodiments. Modifications and alterations will occur to those of ordinary skill in the art, and it is intended that the claims be construed literally and/or according to the doctrine or equivalents to encompass all such modifications and alterations to the fullest possible extent.