Abstract:
The invention disclosed and claimed is an improved plug with an internal anchor. The plug has particular utility in masking openings in parts to be coated. Generally, the plug comprises a compressible, resilient plug body and a compression mechanism. The compression mechanism compresses the plug body between an internal plug anchor and an opposed plug compression surface. The compressive force causes the plug circumference to increase forming a tight seal between the plug and walls forming the opening. The internal anchor design and absence of any axial opening through the entire plug body prevent fluids and other coating materials from passing through the internal plug body and into the interior of the part to be coated thereby avoiding costly damage to the part.

Description:
FIELD OF THE INVENTION 
     This invention is related generally to improved plug apparatus and, more specifically, to plug apparatus providing improved resistance to liquid and material flow. 
     BACKGROUND OF THE INVENTION 
     Many types of manufactured parts, such as parts used in the manufacture of automobiles and machinery, must be coated with various materials and substances to adapt those parts for their intended end use. The coatings impart desired characteristics to the parts, such as resistance to corrosion or friction. Many different types of materials can be applied to the parts including nylons, polycarbonates, metals, etc. Among the well-known types of coating operations used to apply various substances to parts include coating by powder coating, anodizing and plating. 
     In all of these coating operations, the surface portions of the part are completely exposed to the coating substance. In powder coating operations the part to be coated is typically electrostatically charged and heated and then exposed to a fine particulate spray or fluidized bed of oppositely-charged coating particles. The particles are attracted to the surface to be coated and are melted, forming a coating over the part. In anodizing and plating operations, the part to be coated is charged and then dipped into a bath containing the coating material. The coating material is attracted to the part and is deposited onto the exposed surface portions of the part. 
     Many types of parts to be coated include internal surface portions which must not be coated. These types of parts are typically three-dimensional, include outer and inner surface portions and include various openings (also known as holes) in the part outer surface through which coating materials could enter the part and undesirably come into contact with the internal surface portions of the part. 
     It may be undesirable to apply a coating to the internal surface portions of these types of parts for many reasons. For example, it may be undesirable to apply a coating to the internal surface portions of a valve or pipe because that coating may be incompatible with fluids or gases to be conveyed through the valve or pipe. Also by way of example, it may be undesirable to apply a coating to threads cut in the internal surface portion of an annular opening in a tube or other part because that coating may interfere with operation of the threads. It may be undesirable for the liquid media used in plating or anodizing operations to come into contact with the internal surface portions of a part because the media can damage the internal surface portions of the part. 
     Various products have been developed to mask, or close, the openings in these parts thereby preventing coating materials from coming into contact with the internal surface portions of the parts. For example, a variety of caps and plugs are commercially available to mask openings in the part to be coated. These masking devices are configured for the particular application. For example, plugs are intended to be inserted into the opening. The plug has a tapered outer body at least a portion of which has an outside diameter which is larger than the inside diameter of the opening. The plug is held in place by the frictional fit between the plug outer body and the walls forming the opening in the part. 
     Conventional plugs are available in many sizes and shapes and include configurations ranging from gently tapered annular plug bodies to plug bodies having pronounced conical designs. Conventional plugs are available in many types of materials including, for example, cork, silicone and EPDM rubber. 
     Conventional plugs are quite suitable for use in masking most openings in parts and for use with most coating operations. However, these types of masking devices may provide a less-than-complete seal under certain circumstances. For example, certain types of parts may include a confined void volume formed by internal walls of the part and the plug inserted into the opening in the part. If the part is to be heated as part of the coating operation, gas inside the part void volume can expand, potentially forcing the plug partially or completely out of the opening. Failure of the plug may undesirably expose the internal surface portions of the part to the coating material. 
     By way of further example, conventional plugs may form a less-than-complete seal around a threaded opening in the part, particularly where the threads are cut deeply into the walls forming the opening. A less-than-complete seal in such a threaded opening may permit coating materials, such as the liquid media used in plating and anodizing operations, to enter into the interior surface portions of the part by flowing along the threads. 
     Other types of commercially-available plugs for masking openings in parts include apparatus to more completely engage the plug body with the opening walls. These conventional devices include a plug body made of a compressible material and a lever arm with a camming apparatus or other compressing apparatus. The compressing apparatus applies force to the plug body thereby compressing the plug body and expanding the plug circumferentially forming a tight fit between the plug and the opening walls. 
     Compressible plugs are advantageous because they are less likely to be dislodged from an opening by the expanding gas forces within a heated part. In addition, the tight seal formed between the compressible plug and the part can form a more complete seal between the plug body and a threaded opening, particularly where the plug body is made of a soft material which can conform to the threads. 
     However, conventional compressible plugs may not be suitable for use in all coating applications, particularly those applications in which the part is immersed in a liquid media. It has been found that liquid media (such as used in anodizing and plating operations) can flow through an axial opening provided in the plug body and into interior portions of the part. The axial opening is coextensive with the plug body and is provided so that a rod may be inserted through the plug body to join opposed external plates between which the plug body is compressed. 
     Passage of even a small amount of liquid media between the external plates, through the plug body and against the interior surface portions of the part can severely damage the part. The damage may be so extensive that the part must be discarded or the part may require repair and remediation at undue cost. As can be understood, damage of parts is a particular problem in large scale coating operations, such as those found in the automotive industry. Loss of, or damage to, even a small percentage of the parts to be coated can result in significant monetary loss to the manufacturer. 
     It would be significant improvement in the art to provide a plug for masking one or more openings in a part to be coated which would form a complete seal between the plug and opening walls of the part to be coated, which would prevent passage of liquids and other coating materials through the internal plug body, which would be simple and easy to use and which would be reusable. 
     OBJECTS OF THE INVENTION 
     It is an object of this invention to provide an improved plug apparatus which overcomes problems and shortcomings of the prior art. 
     Another object of this invention is to provide an improved plug apparatus which completely seals an opening in a part, particularly to prevent liquids and other materials from entering the opening. 
     A further object of this invention is to provide an improved plug apparatus which completely seals an opening in a part and which prevents passage of liquids and other materials into the part through the internal plug body. 
     Yet another object is to provide an improved plug apparatus which is simple and easy to use. 
     Still another object of this invention is to provide an improved plug apparatus which forms a tight seal across an opening in a part. 
     An additional object is to provide an improved plug apparatus which is reusable. 
     How these and other objects are accomplished will be apparent from the descriptions of this invention which follow. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of an exemplary prior art plug body taken approximately in the mid-section of the body. 
     FIG. 2 is a cross-sectional view of an exemplary prior art plug taken approximately in the mid-section of the plug. 
     FIG. 3 is a partial perspective drawing of an exemplary plug of the invention positioned in an opening in a part including a partial cut-out showing internal plug components. 
     FIG. 4 is a partial perspective view of an exemplary plug of the invention including a partial cut-out showing internal plug components. 
     FIG. 5 is an assembly view of an exemplary plug of the invention including a partial cut-out showing internal plug components. 
     FIG. 6 is a cross-sectional view of an exemplary plug body of the invention including an anchor. 
     FIG. 7 is a cross-sectional view of an exemplary plug of the invention. taken along section  7 — 7  of FIG.  8 . 
     FIG. 8 is a top perspective view of an exemplary plug of the invention. 
     FIG. 9 is a cross-sectional view of an exemplary plug body of the invention including an optional protective cap. 
     FIG. 10 is an assembly view of an exemplary plug of the invention including a partial cut-out showing internal plug components. 
    
    
     SUMMARY OF THE INVENTION 
     The present invention is an improved reusable plug apparatus. The plug has particular utility in coating operations and for masking openings in a part to be coated. The invention includes novel structure preventing liquids and other coating materials applied to the part from passing through the internal plug body and into contact with the interior of the part to be coated thereby avoiding costly damage to the part. 
     Preferred forms of the plug include a reusable plug body having first and second ends, an internal anchor disposed entirely within the plug body and a rod loosely positioned in the plug body. The rod is attached at a first end to the anchor and at a second end to a compression mechanism. The preferred compression mechanism moves the rod and internal anchor toward the plug second end thereby applying compressive force to the plug and expanding the plug circumferentially so that the plug may be secured across an opening in a part to be coated. 
     The preferred plug body is reusable and is made of a compressible, resilient material such as silicone, neoprene, EPDM rubber or any elastomeric material with appropriate properties (such as resistance to heat or corrosive effects of certain liquid media). The plug body may be of any suitable size and configuration needed to appropriately mask the part opening and may include unitary as well as multi-part designs. The preferred plug body has first and second ends and an axial internal opening. The internal opening extends partially through the plug body and has one end coextensive with the plug second end and another end extending to a terminus within the plug body. 
     It is most preferred that the plug body include a compression surface along the plug second end for engaging the compression mechanism. Preferably, a plate such as a nylon or metal washer, is positioned across at least a portion of the compression surface for engaging the compression mechanism thereby providing a wear surface for the plug compression surface and extending the service life of the plug. 
     The internal anchor is embedded in the plug body and is preferably spaced from the plug first end. The internal anchor is in communication with the opening terminus and may include a threaded internal anchor neck portion configured to mate with the rod first end. The anchor may comprise the opening terminus. The internal anchor may be of any suitable configuration capable of engaging the plug body material and may, for example, include a flange and/or other attachment structure such as a shoulder. 
     The preferred rod is positioned loosely through the plug body axial opening. The rod includes a first end attached to the internal anchor. Preferably the rod first end is threaded and is mated with the threaded neck portion of the internal anchor. The rod second end is coupled to the compression mechanism. The rod is provided as a link between the anchor and the compression mechanism and is not limited to any particular material or configuration. 
     The preferred compression mechanism is, as described above, attached to the rod second end. The compression mechanism has at least one position in which the compression mechanism moves the internal anchor toward the plug second end thereby applying compressive force to the plug and expanding the plug circumferentially so that the plug may be secured across the opening. The compression mechanism also has at least a second position in which the compressive force applied to the plug is released so that the plug may be easily removed from the part opening. 
     The most highly preferred form of compression mechanism comprises a lever pivotally mounted on the rod second end, a camming surface on the lever for engaging the plug second end directly along the plug compression surface or along a plate positioned over said surface. In a first position, the lever camming surface applies compressive force to the plug between the anchor and plate and in a second position the compressive force applied by the lever camring surface is released. 
     Other types of compression mechanisms may be used. For example, the compression mechanism may comprise a threaded portion along the rod second end and a threaded fastener, such as a nut, configured to engage the rod second end threaded portion. As the fastener is tightened, it engages the plug second end along the plug compression surface and preferred plate. In at least a first position, the fastener applies compressive force to the plug and in at least a second position the compressive force applied by the fastener is released. 
     The advantageous design of the inventive reusable plug provides a tight, secure seal between the outer surface of the plug and the opening of a part to be masked and at the same time prevents fluid migration through the plug body as is the case with prior art designs. Any fluid or other material which might enter the plug body of the inventive plug is blocked from further movement by the opening terminus and anchor. By preventing liquids and other materials from entering the internal portions of the parts being coated it is expected that the inventive plug will result in fewer damaged parts and will result in significant cost savings. 
     Further aspects and advantages of the invention will become apparent to those skilled in the art from a review of the following detailed description taken in conjunction with the drawings and the appended claims. It should be noted that the invention is susceptible to embodiments in various forms. Therefore, the specific embodiments described hereinafter are provided with the understanding that the present disclosure is intended as illustrative and is not intended to limit the invention to the specific embodiments described herein. 
     DETAILED DESCRIPTION 
     FIGS. 1-2 show a prior art plug  10 . Prior art plug  10  includes plug body  11  made of an elastomeric material. Plug  10  is intended to be inserted into an opening (not shown) in a part (not shown) in order to prevent liquids, coating materials and other substances from entering the opening and coming into contact with the inner surface portions of the part. As shown best in FIG. 1, plug body  11  includes first end  13 , second end  15  and outer surface  17 . Internal opening walls  19  form an axial opening  21  coextensive with plug body  11 . Opening  21  has a first opening  23  along plug first end  13  and a second opening  25  along plug body second end  15 . Axial opening  21  provided in prior art plug  10  extends along the entire length of plug body  11  disadvantageously providing a passageway through which fluids, gasses and particulates can migrate along opening  21 , through plug  10  and into the inner surface portions of the part. 
     As shown in FIG. 2, prior art plug  10  includes bottom plate  27  which is positioned against plug body first end  13  and top plate  29  positioned against plug body second end  15 . Plates  27  and  29  are typically washers. Annular opening  31  is formed in bottom plate  27  and annular opening  33  is formed in top plate  29 . 
     Also as shown in FIG. 2, rod  35  is positioned loosely through axial opening  21 . Accordingly, rod  35  is moveable within axial opening  21 . Rod  35  includes rod first end  37  and rod second end  39 . Rod first end  37  extends through annular opening  31  in bottom plate  27  while rod second end  37  extends through annular opening  33  in top plate  29 . An appropriate fastener, such as nut  41 , is secured to rod first end  37  along threads (not shown). 
     Cam lever  43  is moveably secured to rod second end  39  by pivot pin  45 . Pivot pin  45  is inserted through hole  47  in rod second end  39  and through holes  49   a  and  49   b  (not shown) provided in cam lever  43 . Cam lever  45  includes handle  51 , cam lever body  53  and cam surface  55 . Movement of cam lever  43  in the direction of arrow  59  urges cam surface  55  against compression surface  57  provided on plate  29 . Nut  43  is moved against bottom plate  27  causing bottom plate  27  to move toward top plate  29  as rod  35  is moved by the action of the cam lever  43 . Compressive force applied through plates  25  and  27  expands the plug body  11  circumferentially forming a seal between the plug outer surface  17  and the interior walls (not shown) of a part. The prior art plug  10  does not close the passageway formed by axial opening  21  and does not solve the problem of preventing infiltration of liquids and other materials through plug  10  and into the interior portions of the part. 
     FIGS. 3-10 show alternative exemplary embodiments of the invention and demonstrate how the abovementioned disadvantages of the prior art plugs have been overcome. FIG. 3 shows the inventive plug  110  inserted into an opening in part  113  formed by at least one wall  111 . Plug  110  is provided in part  113  to mask the opening formed by wall  111  prior to coating of part  113  in a coating operation. Plug  110  is provided to prevent liquids or other coating materials from entering opening and coating, or coming into contact, with part inner surface  115 . Part  113  shown in FIG. 4 is in the form of a tubular pipe. However, plug  110  may be used with any shape part provided that plug  110  is of an appropriate configuration to mask an opening formed by wall or walls  111 . Plug  110  is selected to be of a size slightly smaller than that of the opening formed by wall  111  so that plug  110  can be easily placed into the opening and then held tightly in the opening once the plug  110  circumference is expanded by the compressive forces applied to the plug  110 . 
     Plug  110  shown in FIGS. 3-10 includes plug body  117  made of a suitable elastomeric material, such as silicone, neoprene, EPDM rubber. Plug body  117  includes first end  119 , second end  121  and outer surface  123 . Plug body second end  121  includes a compression surface  125  which is acted against by the compression. mechanism as described below. Internal opening walls  127  form an axial opening  129  partially coextensive with plug body  117 . Opening  129  includes a terminus  131  within plug body  117  spaced apart from plug body first end  119  and an opening  133  along plug second end  121 . The axial opening  129  provided in plug  110 , therefore, does not extend along the entire length of plug body  117 . Terminus  131 , in effect, forms a wall preventing migration of materials through opening  129 . Fluids, gasses and particulates cannot pass through opening  129  and into part inner surface  115  as is the case with prior art plugs. 
     As is further shown in FIGS. 3-10, plug  110  includes internal anchor  135  spaced apart from plug body first end  119 . Anchor  135  shown in FIGS. 3-10 is positioned entirely within plug body  117  by any suitable means. For example, in plugs having a plug body  117  made of a rubber material, anchor  135  may be positioned in plug body  117  prior to vulcanization of the rubber material forming plug body  117 . Anchor  135  may be made of any suitable material such as nylon  6 — 6 , teflon, stainless steel or other metal. 
     As is apparent from FIGS. 3-7 and  9 - 10 , anchor  135  may be provided in any suitable configuration capable of forming a secure fit within plug body  117 . For instance, anchor  135  may include flange  137  (FIGS. 3-7,  9 - 10 ) and/or shoulder  139  (FIGS. 6-7) formed around anchor  135  to better secure anchor  135  within plug body  117 . 
     Neck  141  may be provided be provided in anchor  135  to mate with rod  143 . Neck  141  may include threads  145  for mating with corresponding threads  147  along rod first end  149 . Any suitable manner of connecting anchor  135  to rod  143  may be used. 
     Plate  151  is shown positioned against plug body second end  121 . Plate  151  is optionally provided to serve as a wear surface across compression surface  125  formed by plug body second end  121 . When a plate  151  is used, plate compression surface  153  serves as a surface against which the compression mechanism acts as described below. Plate  151  is typically a washer. Plate  151  may be made of any suitable material such as nylon  6 — 6 , teflon, stainless steel or any other suitable metal. Opening  155 , which may be annular in shape, is formed in plate  151  through which rod  143  is positioned. 
     Rod  141  includes rod first end  149  and rod second end  157 . Rod first end  149  mates with anchor  135 . Rod second end  157  extends away from plug body  117  through opening  155  of plate  151 . As shown best in FIG. 7, rod  143  is positioned through axial opening  129 . Rod  141  has an outside diameter  159  which is less than the inside diameter  161  of axial opening  129 . Accordingly, rod  143  is moveable within axial opening  129 . 
     FIGS. 3-10 show embodiments of preferred compression mechanisms (i.e., compression means) used to apply compressive force to the plug  110  and to expand the plug  110  circumferentially so that at least a portion of plug outer surface  123  will firmly engage walls  111  in part  113  masking the opening and preventing plug  110  from becoming dislodged from part  113  during use. The secure fit provided by the compression mechanism also permits plug  110  to resist movement caused by force applied from expanding gases within part  113 . The compression mechanism is not limited to any particular embodiment as will be described below. 
     The compression mechanism includes cam lever  163  moveably secured to rod second end  157  by pivot pin  165 . Pivot pin  165  is inserted through hole  167  along rod second end  157  and through holes  169   a  and  b  provided in cam lever  163 . Pin  165  may be held in place by an appropriate means such as by forming flanges  171   a  and  b  in pivot pin ends  173   a  and  b . These compression mechanism components may be made of any suitable material including those listed above with respect to the anchor  135  and rod  143  components. 
     Cam lever  163  includes handle  175 , cam lever body  177  and cam surface  179 . When cam lever  163  is moved in the direction of arrow  181  to the first, or compression, position shown in FIG. 3, cam surface  179  is urged against compression surface  153  on plate  151 . In the first position, compressive force applied through anchor  135  and plate  151  expands plug body  117  circumferentially forming a tight seal between the plug outer surface  123  and the interior walls  111  of part  113 . When cam lever  157  is moved in a direction opposite to arrow  181 , to a second, or release, position as shown in FIG. 4, compressive force is released permitting plug  110  to be easily removed from opening  111 . As is apparent, cam lever  163  can be quickly moved between the first and second positions permitting rapid insertion and removal of plug  110  into and from part  113 . 
     Other types of compression mechanisms may be used. As shown in FIG. 10, urging means in the form of a nut  183  (such as a wing nut) could be used in place of cam lever  157 . In such an embodiment, rod second end  157  is provided with a threaded portion  185  for mating with threads  187  of nut  183 . Nut  183  is configured to engage rod second end threaded portion  185  and to engage plug second end  121  along compression surface  125  directly or through plate compression surface  153 . As nut  183  is tightened (i.e., rotated in a clockwise direction) to a first, or compression, position, the nut  183  gradually urges anchor  135  toward plate  151  applying compressive force to plug  110  to firmly secure plug  110  in opening  111 . As nut  183  is loosened (i.e., rotated in a counterclockwise direction) to a second, or release, position, the compressive force is gradually released until plug  110  may be easily removed from opening  111 . This arrangement also permits quick movement between the first and second positions thereby permitting rapid insertion and removal of plug  110  into and from part  113 . 
     Other optional configurations and components may be provided in, or used in conjunction with, the invention so as to customize plug  110  for use in a particular operation. For example, plug body  117  may include a shoulder, such as annular shoulder  189  (FIGS. 3-10) provided to abut part  113 . Shoulder  189  is provided to form a more complete mask over the opening formed by walls  111  during a coating operation. Annular ribs (not shown) could be provided around outer surface  123  of an annular plug to provide for a better frictional fit between plug  110  and an annular opening in a part  113 . The plug body  117  could consist of two body portions (not shown) separated by a spacer. A cap  191  (FIG. 9) fitted over compression mechanism may be provided to cover the compression mechanism and to protect the compression mechanism from liquids and other materials. Other compression mechanisms, such as those using other types of camming mechanisms, may be utilized as deemed appropriate. 
     While the principles of this invention have been described in connection with specific embodiments, it should be understood clearly that these descriptions are made only by way of example and are not intended to limit the scope of the invention.