Abstract:
Systems and methods are provided for attaching flexible conduit to a fitting. Prongs of a conduit retention clip contact opposite sides of the flexible conduit in an aperture of the fitting. By aligning the prongs in grooves of the flexible conduit, the flexible conduit is held in place in the aperture of the fitting without sufficient compression to surpass the structural limits of the fitting.

Description:
TECHNICAL FIELD 
     Embodiments relate generally to fittings for flexible conduit. 
     BACKGROUND 
     Flexible conduit may be made by coiling a self-interlocking ribbed strip of material. The interlocking ribbed structure forms a tube that may bend or flex in multiple directions. The ability to bend allows for flexible conduit to be used in multiple applications where a rigid conduit may not be practical. Unlike rigid conduits, the flexible conduit may change its shape to match each installation or change as repairs are made. Wires are pulled through the tube and are thereby protected by the conduit from damage, both internal and external. 
     Flexible conduit may be attached to one or more terminals or junction boxes. The fitting between the flexible conduit and the terminal needs to be secure enough to withstand a steady pull so that the flexible conduit is unable to be removed by bending or flexing. For a metal on metal connection, a strap or compression based connection may be used. For a metal conduit and non-metallic terminal (e.g. plastic), a compression based connection may not be useful as the compression required to withstand a steady pull may surpass the structural limits of a non-metallic terminal. A new type of fitting is needed to attach flexible conduit to a terminal. 
     SUMMARY 
     A fitting and the use of the fitting with flexible conduit are provided. Prongs of a conduit retention clip contact opposite sides of the flexible conduit in an aperture of the fitting. By inserting the conduit retention clip through holes in the fitting with the prongs aligned to be in grooves of the flexible conduit, the flexible conduit is held in place in the aperture of the fitting. This arrangement may avoid sufficient stress to surpass the structural limits of the fitting. 
     In a first aspect, a flexible conduit fitting system is provided. The system comprises a conduit adapter and a conduit retention clip. The conduit adapter comprises a conduit aperture and two guide holes. The conduit aperture is configured to receive a flexible conduit. The conduit retention clip comprises two prongs configured to be inserted in the two guide holes. 
     In a second aspect, a system is provided for attaching a flexible conduit. The system comprises a conduit adapter, a first removable conduit retention prong, and a second removable conduit retention prong. The conduit adapter is configured to receive a flexible conduit having a minor diameter, a major diameter, and a pitch distance, into an aperture having a central axis. The first removable conduit retention prong is configured to be inserted into a first guide hole in the conduit adapter. The second removable conduit retention prong is configured to be inserted into a second guide hole in the conduit adapter. The first guide hole and second guide hole are located across the central axis of the aperture from one another. The first guide hole and second guide are separated by a distance greater than a minor diameter and less than a major diameter of the flexible conduit. 
     In a third aspect, a method is provided for attaching a flexible conduit to a conduit adapter. The method comprises inserting the flexible conduit having a minor diameter and a pitch distance into an aperture of the conduit adapter. The aperture has a central axis. Two prongs are inserted into two guide holes located across the central axis from one another. The two guide holes are separated by a distance greater than the minor diameter and less than the major diameter of the flexible conduit. The flexible conduit is held in place by the two prongs. 
     Other systems, methods, and/or features of the present embodiments will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. Additional features of the disclosed embodiments are described in, and will be apparent from, the following detailed description and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  illustrates an example segment of flexible conduit. 
         FIG. 2  illustrates an example apparatus of a non-metallic fitting for attachment of flexible metallic conduit. 
         FIG. 3A  and  FIG. 3B  illustrate cross sections of an example non-metallic fitting for attachment of flexible metallic conduit. 
         FIG. 4A  and  FIG. 4B  illustrate perspective and cut-away views of an example non-metallic fitting flexible metallic conduit being held. 
         FIG. 5  is a flow diagram of one embodiment of a method for attaching a flexible metallic conduit using a non-metallic fitting. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth in order to provide a more thorough description of the present invention. It will be apparent, however, to one skilled in the art, that the present embodiments may be practiced without these specific details. In other instances, well-known features have not been described in detail so as not to obscure the invention. 
     An adapter is provided for attaching flexible conduit. The adapter secures the flexible conduit using a conduit retention clip. Due to the geometry of the flexible conduit and placement of the clip, the conduit retention clip axially constrains the flexible conduit to the adapter without over stressing the adapter. 
       FIG. 1  illustrates an example of flexible conduit  95  depicted here as flexible metallic conduit  95  (FMC). FMC  95  may also be referred to as Greenfield or Flex and may be made of aluminum, steel, galvanized steel, or other material. Other types of flexible conduit, made of non-metallic materials such as plastic or rubber, may be used. FMC  95  may be formed from a self-interlocked strip that when interlocked, provides a ribbed tubular structure with a conduit central axis  30 . FMC  95  has both ribs  20  and valleys  25 . A valley  25  may refer to the area between the ribs  20  or the closest point to the center of the FMC  95 . The ribs  20  or raised portions of the FMC  95  have a different profile than the valleys  25  of the FMC  95 . As shown in  FIG. 1 , a diameter calculated perpendicularly from a rib to another rib is shown as distance  35  (referred to as the major diameter  35 ). A diameter calculated perpendicularly from a valley to a valley is shown as distance  40  (referred to as the minor diameter  40 ). The ribs  20  and valleys  25  of the FMC  95  are offset to one another in a spiral or helical pattern such that the ribs  20  are a continuous rib and the valleys  25  are a continuous valley. 
     The offset between the valleys  25  may be referred to as a pitch (or pitch distance  55 ). In  FIG. 1 , the pitch distance  55  is the lateral offset distance along the conduit central axis  30  between the two valleys  45  and  50 . The pitch distance  55  may also be measured by using other similar features on opposing sides. A second pitch distance  56  or offset in an opposite lateral direction may be used. In  FIG. 1 , the second pitch distance  56  is illustrated as the offset from the valley  45  to the valley  51 . Depending on the profile of the FMC, e.g. a width of the ribs  20  versus a width of the valleys  25 , the pitch distance  55  and second pitch distance  56  may be equal or unequal. 
     Different types of FMC  95  may have different minor and major diameters depending on the amount of wires or cable the FMC  95  needs to carry. Different types of FMC  95  may have different pitch distances depending on the structure, the flexibility required, or the materials used. 
     FMC  95  may be used to provide protection for enclosed conductors from an impact or the environment. The enclosed conductors, e.g., wires or cables, may terminate at a junction box or a terminal. A junction box, for example, may serve as an enclosure for electrical connections between incoming wires from the FMC  95  and one or more electrical devices. Junctions or terminals may be formed from metal such as aluminum or steel or a non-metallic material such as plastic. A junction or terminal may have one or more fittings or adapters for attaching a segment of FMC  95 . The fittings may be integrated into the junction box or may be a separate adapter and require an additional connection to the junction box. The fitting may be formed from a non-metallic material, such as injection molded plastic. Using injection molded plastic may be less expensive than using a metal component. However, a drawback for using non-metallic materials such as molded plastic is that the non-metallic material may be prone to cracking or failure when exposed to compression stresses. A metallic fitting may be stronger, harder, and more durable than, for example, a plastic counterpart. A metallic fitting may be able to flex or bend and maintain its structural strength while a plastic counterpart cannot. As such, in order to use a non-metallic fitting, precautions may be taken so as not to stress the fitting to failure. A known method of attaching FMC  95  to a junction by using a screw to compress the FMC  95  against the metallic fitting may not be possible for a non-metallic fitting. The stress on the non-metallic fitting required to hold the FMC  95  may deform a non-metallic fitting. A deformed non-metallic fitting may be prone to cracking or failure. Compression may also damage the FMC  95  or the wires enclosed. A screw driven directly on top of FMC  95  may puncture the FMC  95  and either damage the contents or break a seal allowing moisture or chemicals into the conduit. 
       FIG. 2  depicts an example apparatus for attaching FMC  95  to a fitting. The fitting includes a conduit adapter  87 , which includes an aperture  83  configured to receive the FMC  95 . The conduit adapter  87  includes two or more guide holes  89  (shown as exaggerated dots to better show placement). The guide holes  89  are configured by size and placement to receive a conduit retention clip  85 . The guide holes  89  extend to and beyond the aperture  83 , so the resulting exposed holes of only one guide hole  89  are shown in  FIG. 2  due to the perspective view. The conduit retention clip  85  may be a separate piece from the conduit adapter  87 . Additional, different, or fewer components may be provided. 
     The conduit adapter  87  may be formed from a non-metallic material. For example, the conduit adapter  87  may be plastic formed by an injected plastic molding process. Depending on the use, different types of plastic or polymers may be used to alter the rigidity and strength of the resulting plastic part. The conduit adapter  87  may be molded as a single part or as multiple parts that are subsequently fused or glued together. Certain portions of the conduit adapter  87  may be machined after the initial part is formed. For example, the guide holes  89  may be threaded using a boring machine, drilled using a press, punch, or thermal pin, or may be formed as part of the forming of the conduit adapter  87 . Alternative processes may be used to form the conduit adapter  87 , such as  3 D printing. Alternative material may be used in the conduit adapter  87 , such as rubber. The conduit adapter  87  may be formed from a metallic material. 
       FIG. 2  depicts a conduit adapter  87  with a round shape. The conduit adapter  87  may have multiple structural configurations. For example, the conduit adapter  87  may be rectangular or shaped as a square. Different sized conduit adapters  87  may be used for different sizes of FMC. An entrance of the aperture  83  of the conduit adapter  87  may be flush with a side of a junction box (e.g. the rest of the aperture embedded in the junction box). The conduit adapter  87  may extend outward as shown in  FIG. 2 . Two or more conduit adapters  87  may be connected or integrated into a junction box. The conduit adapter  87  may include a housing  81  for the guide holes  89 . The housing  81  may be formed as part of the conduit adapter  87  or may be a separate part. The housing  81  may hold or contain the top section  88  of the conduit retention clip. As shown in  FIG. 2 , the housing  81  may extend outward from the conduit adapter  87 . The conduit retention clip  85 , once inserted, may be protected from the environment and any impacts. 
     The conduit adapter  87  may be integrated as part of a junction box. In such an embodiment, the conduit adapter  87  and junction box may be a single molded piece of plastic. Cost saving for material and incorporation of two separate parts may be achieved by not needing an additional part for conduit adaption, particularly in non-metallic junction boxes. Alternatively, the conduit adapter  87  may be connected to a junction box or terminal using a screw, tab, pin, or any other coupling mechanism. One or more arms or tabs with one or more holes may be provided for attachment to the junction box or terminal. Other structures may be used to attach the conduit adapter  87  to the junction box or terminal. 
     The conduit retention clip  85  may be configured (e.g., size and shape) to be inserted into the guide holes  89  in the conduit adapter  87 . The conduit retention clip  85  may be formed from a metal, such as steel, or a non-metallic material, such as plastic. The conduit retention clip  85  may include a top section  88  and two prongs  84 . The two prongs  84  may be parallel and perpendicular to the top section  88 . The two prongs  84  may not be parallel. For example, in  FIG. 2 , the distance  87  between the prongs  84  at the ends of the prongs  84  away from the top section  88  may be larger than the distance  86  between the prongs  84  adjacent to the top section  88 . The distance of the holes  89  that the prongs  84  are inserted into may be similar to the distance  86 . As such, the two prongs  84  may be pinched together to fit into the two holes  89 . Alternatively, the distance  87  is less than the distance  86  and the prongs  84  are spread apart for insertion into the holes  89 . 
     The conduit retention clip  85  may be inserted through the aperture  83 . The aperture  83  may have additional holes or indents for the ends of the prongs  84  to rest in (e.g., the bore of the holes  89  extends through the aperture  83  to provide two holes per prong  84  in the aperture  83 . The prongs  84  of the conduit retention clip  85  may be elastic in that the prongs  84  attempt to return to an original shape. The outward pressure of the prongs  84  may hold the conduit retention clip  85  inside the guide holes  89 . 
     The prongs  84  may not be flexible. The conduit retention clip  85  may be rectangular shaped with two parallel prongs  84  and a top of the conduit retention clip  85 . The conduit retention clip  85  may be held in place by gravity or friction from the ribs of the FMC  95  and/or friction from a tight fit with the holes  89 . The conduit retention clip  85  may be held in place by a cap, lid, or stop that prevents the conduit retention clip  85  from being retracted. The guide holes  89  may include a retainer to prevent the two prongs  84  from slipping out. For example, the guide holes  89  may contain a spring loaded ball like structure (or variant) that engages a hole in each of the prongs  84  as a detent holding the prong and clip in place. 
     In an embodiment, the two prongs  84  may be separate parts or pins (i.e., no top section  88 ). Each prong  84  may be inserted separately into the guide holes  89 . Each prong  84  may be retained using a separate retention mechanism. For example, each prong  84  may be a sprung hairpin, a bobby pin, or a small clip. Each prong  84  may be a threaded screw that may be screwed into the guide holes  89 . The guide hole  89  may be threaded to accept the prongs  84 . 
       FIG. 3A  and  FIG. 3B  depict cross sections of an example fitting for attachment of FMC  95 .  FIG. 3A  depicts a cross-section view looking down the aperture  83  from an entrance of the aperture  83 .  FIG. 3A  depicts the conduit adapter  87 , the aperture  83 , the housing  81 , and two guide holes  89  into which the conduit retention clip  85  is inserted. The conduit retention clip  85  is depicted as two separate prongs  84  that may be inserted into the two guide holes  89 .  FIG. 3A  further illustrates a minor circumference  41  relating to the minor diameter  40  of the FMC  95  and a major circumference  36  relating to the major diameter  35  of the FMC  95 . The minor circumference  41  and the major circumference  36  help illustrate how the FMC  95  is secured by the conduit retention clip  85 . Referring back to  FIG. 1 , the minor circumference (minor diameter  40 ) is related to the valleys, the major circumference (major diameter  35 ) is related to the ribs. The area between the minor circumference  41  and the major circumference  36  correspond to one or more valleys in the FMC  95  between the one or ribs. By placing the prongs  84  in the area, the FMC  95  is unable to move in and out of the aperture  83  due to each prong positioned between two ribs. 
       FIG. 3B  depicts a view at different depths of a cross-section from a side of the apparatus (along the axis of the aperture  83  and through the axes of the holes  89 ).  FIG. 3B  includes the conduit adapter  87 , the aperture  83 , the two holes  89  for the conduit retention clip  85 , and a portion of a junction box  93 . The adapter  87  and junction box  93  may be a single molded part.  FIG. 3B  further illustrates an offset  96  between the centers of the two holes  89  laterally along a central axis  82  of the aperture  83 . The offset  96  may correspond to the pitch distance  55  or second pitch distance  56  of the FMC  95  depending on which hole of the two holes  89  is closer to the entrance of the aperture  83 . The two holes  89  and inserted two prongs  84  may be located offset to one another in order to secure the FMC  95 . FMC  95  may have a spiral pattern of ribs and valleys. As illustrated in  FIG. 1 , the FMC  95  does not possess radial symmetry or bi-lateral symmetry. The two holes  89  may be offset at a similar angle to a pitch angle of the FMC  95 . A pitch angle is an angle at which the FMC spiral pattern advances as the interlocking strips are connected. The inserted two prongs  84  are therefore offset along the axis of the aperture  83  to one another so that both prongs  84  may align with a valley of the FMC  95 , thus securing the FMC  95  in place. The offset distance  96  may be similar to the pitch distance  55  of the FMC  95 . The offset distance  96  may be similar to the pitch distance  55  plus one or more integer multiples of the distance of the spiral pattern (e.g. in  FIG. 1 , the distance between points  50  and  51  representing a complete pattern). Using one or more integer multiples of the distance of the spiral pattern, the offset distance  96  may allow a hole to skip a valley. “Similar” in this context allows for ¼ or less difference from the pitch distance  55 . The pitch distance  55  may be the distance between two parallel lines drawn from two corresponding points on the FMC  95 , e.g. the center of two opposing ribs as shown in  FIG. 1 .  FIG. 3B  further shows the minor circumference  41  and major circumference  36  of the FMC  95 . 
     The aperture  83  may be sized to receive the FMC  95 , so is about the size of the major diameter or circumference  36  or larger. “About” allows for a smaller diameter allowing for insertion with a friction fit. The aperture  83  may be circular or oval shaped. The size of the aperture  83  may be related to the size of the FMC  95 . Different diameters of FMC  95  may use different sized apertures (and different sized adapters  87 ). In one embodiment shown in  FIGS. 3A and 3B , the diameter of the aperture  83  is larger than a maximum diameter of the FMC  95 . There is no maximum size of the aperture  83 , however as the size increases, if the diameter of the FMC  95  does not increase, it may become difficult to align the prongs  84  with the valleys of the FMC  95 . 
     At an end of the aperture  83  closer to the junction box  93 , there may be a stop or part to limit the lateral movement of the FMC  95 . For example, the FMC  95  may only be able to be inserted so far into the aperture  83  until the FMC  95  hits the stop or part. 
     The guide holes  89  may be configured to accept the conduit retainer. The guide holes  89  may be aligned so that when the conduit retention clip  85  is inserted, the prongs  84  of the conduit retention clip  85  are located in valleys (spaces between the ribs) of the FMC  95 . The guide holes  89  may be parallel with one another or askew. The guide holes  89  may extend past the aperture  83  in order to anchor the bottom of the prongs  84 , but may instead only extend into the aperture  83 .  FIGS. 3A and 3B  show the guide holes  89  extending past the aperture  83  and partly into the opposite side of the adapter  87 . In other embodiments, the guide holes  89  may extend completely through the adapter  87 , such as to allow insertion of the prongs  84  from either of two directions. The guide holes  89  may include a retainer to prevent the prongs  84  from backing out of the holes  89 . 
     Once inserted, the prongs  84  of the conduit retainer clip  85  are configured to capture the FMC  95  by being positioned tangentially to a valley of the FMC  95 . The FMC  95  is thus unable to move in and out of the aperture  83  as the ribs of the FMC  95  are locked in place. Due to the geometry of the major diameter  35 , minor diameter  40  and pitch of the FMC  95  and the adapter&#39;s offset retention features, the FMC  95  is captured on its minor diameter  40  in two places without compressing or deforming the adapter. The location of the conduit retainer clip eliminates the possibility of cracking the adapter. In alternative embodiments, the prongs  84  may compress the FMC  95  from opposing sides as and/or once inserted against the FMC  95 . 
       FIG. 4A  and  FIG. 4B  depict example views of the apparatus of  FIG. 2  with the FMC  95  being held in place.  FIG. 4A  includes the conduit adapter  87 , the FMC  95 , the housing  81  and the conduit retention clip  85 .  FIG. 4A  depicts the FMC  95  inserted into the aperture  83  of the conduit adapter  87 .  FIG. 4A  further depicts the conduit retention clip  85  inserted into the guide holes  89  (not shown) in the conduit adapter  87 . The top section  88  of the conduit retention clip  85  fits inside of and is protected by the housing  81 . As shown, the housing  81  allows for a level (e.g. head of a screwdriver) to be inserted underneath the top section  88  to pry out the conduit retention clip  85 . Alternative structures for the housing  81  may be used. The housing  81  may include a removable cap that is placed over the inserted conduit retention clip  85 . The housing  81  may be integrated into the conduit adapter  87  or may be a separate part. 
       FIG. 4B  depicts a cut away, top-down view of the apparatus of  FIG. 2 . The FMC  95  has been inserted into the aperture  83  of the conduit adapter  87 . The conduit retention clip  85  has been inserted into the guide holes  89  (not shown) in the conduit adapter  87 . As shown, the prongs  84  of the conduit retention clip  85  are offset from one another in order to match the spiral pattern of the FMC  95 . The inserted prongs  84  align with two of the valleys of the FMC  95  on opposite sides, preventing the FMC  95  from ejecting from the conduit adapter  87 . The offset may be determined based on the pitch angle or pitch distance  55 . The inserted prongs  84  may align with two opposing valleys that are closest one another, or the inserted prongs  84  may skip a valley on one side of the FMC  95 . 
       FIG. 5  depicts a flow chart for attaching a FMC  95  using the apparatus of  FIG. 2 . Additional, different, or fewer acts may be provided. For example, act A 120  may not be performed if the prongs  84  of the conduit retention clip  85  are parallel and configured to be inserted directly into the guide holes  89  without pinching or spreading. 
     At act A 110 , a segment of FMC  95  is inserted into an aperture  83  of a conduit adapter  87 . The FMC  95  has a minor diameter  40 , a major diameter  35 , and a pitch distance  55  as described in  FIG. 1 . The minor diameter  40  corresponds to a distance that is calculated from a distance of an interior diameter plus the thickness of the FMC  95  (i.e., twice the wall thickness of the FMC  95 ). The major diameter  35  is the larger diameter that corresponds to the ribs or the outer diameter of the FMC  95 . The pitch distance  55  corresponds to a lateral distance between opposing valleys. The pitch distance  55  may correspond to the lateral distance that a spiral pattern of the FMC advances over 180 degrees. The aperture  83  of the conduit adapter  87  about the or larger than the major diameter  35  of the FMC  95  so that the FMC  95  may be inserted into the aperture  83  without undue hassle. 
     The conduit adapter  87  includes at least two guide holes  89  that are configured to accept the respective prongs  84  of a conduit retention clip  85 . The segment of FMC  95  may be inserted into the aperture  83  until two or more of the ribs of the FMC  95  have passed the two guide holes  89 . 
     The conduit adapter  87  may include a stop to limit how far the FMC  95  may be inserted. For example, the conduit adapter  87  may be integrated into a junction box  93  that contains electrical connections. The junction box  93  may protect the wiring or cables and thus have no need for the FMC  95  to extend into the junction box  93 . In certain embodiments, the conduit adapter  87  is used to support a length of FMC  95 . The FMC  95  may be inserted through the aperture  83  until the region of FMC  95  that is to be supported is reached. 
     At act A 120 , the prongs  84  of the conduit retention clip  85  are pinched together. The conduit retention clip  85  may be configured to be elastic. The two prongs  84  of the conduit retention clip  85 , for example, may spring back to a first shape if deformed. The two prongs  84  may be configured to push outwards on the guide holes  89  to hold the conduit retention clip  85  in the guild holes  89 . The two prongs  84  may be shaped askew (not parallel) in a first shape. In the first shape, the guide holes  89  may not accept the prongs  84 . However, when pinched, the prongs  84  may become parallel and thus be capable of insertion into the guide holes  89 . In alternative embodiments, the prongs  84  may be spread instead of pinched to align with the guide holes  89 . 
     At act A 130 , the conduit retention clip  85  is inserted into the two guide holes  89  so that the FMC  95  is held in place between the two prongs  84  of the conduit retention clip  85 . The use of the conduit retention clip  85  does not overly compress the conduit adapter  87  or place stress on either the FMC  95  or the conduit adapter  87 . Alternatively, some compression is provided. 
     At act A 140 , the conduit retention clip  85  (and the two prongs  84 ) hold the FMC in the aperture. When inserted after act A 130 , each of the prongs  84  of the conduit retention clip  85  may be located tangentially to the minor diameter  40  of the FMC  95 . Due to the geometry of the major diameter  35 , minor diameter  40  and pitch of the FMC  95  and the adapter&#39;s offset retention features, the FMC  95  is captured on its minor diameter  40  in two places by the prongs  84 . The use of the conduit retention clip  85  eliminates the possibility of cracking the conduit adapter by over tightening a screw or other compression technique. 
     In order to release the FMC  95 , the conduit retention clip  85  may be pulled out from the conduit adapter  87 . The conduit retention clip  85  may be configured to have a lip or tab that may be grabbed. The housing  81  of the retention clip may provide a slot to place, for example, a flat head screwdriver to lever the retention clip  85  out of the adapter  87 . 
     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of this invention. In addition, the various features, elements, and embodiments described herein may be claimed or combined in any combination or arrangement.