Abstract:
A lampholder includes a housing and a plurality of electrical terminals. The lampholder is adapted to hold a light-emitting diode (LED) tube light assembly supported at two ends of the tube light. The lampholder includes at least one terminal that electrically couples before the remaining terminals located in the same housing to ensure a first-connect, last-disconnect electrical connection when inserting the LED tube light into and removing the LED tube light from the lampholder.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present description relates generally to lampholders for electrical devices, such as for example for tube lamps, and more particularly, to methods and apparatus for grounding an electrical device via a lampholder. 
       BACKGROUND OF RELATED ART 
       [0002]    Traditional fluorescent tube lamps, such as for example T-5 and T-8 lamps, use fluorescent technology and only require two pins, e.g., electrical contacts, at the two ends of the tube lamp and in corresponding contacts in the lampholders. These lampholders, typically referred to as tombstone style lampholders are generally well known in the art. 
         [0003]    For example, U.S. Pat. No. 2,247,117 describes a lampholder or socket for a lamp having a double end discharge, such as a fluorescent tube design. The described socket includes a base, a cover, and two contact members. The contact members cooperate with and engage the contact pins extending from a base at each end of the tubular lamp, such as a fluorescent lamp. The base and housing of the socket are typically made of any suitable insulating material. In use, the contacts of the tubular lamp are mounted to the socket by inserting the contacts of the lamp into a slot provided in the socket. Thereafter, the lamp is rotated ninety degrees to engage the contacts of the lamp with the contacts of the lampholder. 
         [0004]    Recently, new light-emitting diode (LED) tubes have been designed to fit into the same lampholders as previously used in fluorescent tube lamps. An LED tube is made up of dozens of individual LEDs. They come in a variety of sizes (e.g., 2, 4 or 6 feet), different color temperatures (i.e., different colors of light), and varying lumen output. LED tubes can be purchased with new fixtures, or used for retrofitting existing fixtures. However, LED tubes don&#39;t require the ballasts that traditional fluorescents need, so the ballasts need to be removed when replacing fluorescent bulbs with LED tubes. Instead of a ballast, LEDs use a driver to convert the line AC voltage to DC and to provide other conditioning and control. Often the driver is contained in the same housing as the LEDs, meaning a line voltage shock risk is present Other times, even with the driver housed separately, the input DC voltage to the lamp can still be high enough to be a shock risk (NEC Circuit Class 1). As such, LED lamps can sometimes pose a safety risk due to exposed metal for reasons such as, for instance, heat-sinking or electrical contacts. 
         [0005]    Recently some LED systems have been developed with switches in the LED tubes for safety purposes. These safety switches, while sufficient for their intended purposes, add cost and complexity to the lamp that may not be desirable in some manufacturing instances. 
         [0006]    Still further, in other LED tube systems, such as the Japanese JELMA 801 standard, an incorporated ground path is provided for performance reasons. For instance, a GX16t-5 LED lamp includes a power input side, having two connectors, and a ground side at the opposite end. In operation, the user can insert the power side into the respective lampholder before inserting the ground side. Oftentimes, insertion of the power side first is without risk to the installer, but that may not always be the case, such as for instance, when the power level is not NEC Circuit Class 2. 
         [0007]    Thus, there is a recognizable need for safe and convenient methods and apparatus for grounding an LED tube as disclosed herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a front perspective view of an example lampholder and tube lamp assembly in accordance with an example of the present disclosure. 
           [0009]      FIG. 2  is a front perspective view of the example lampholder showing the interior of the lampholder housing. 
           [0010]      FIG. 3  is a front elevational view of the example lampholder. 
           [0011]      FIG. 4  is a front elevational view of the example lampholder showing the interior of the lampholder housing. 
           [0012]      FIG. 5  is a front perspective view of the example terminals disposed within the example lampholder housing. 
           [0013]      FIG. 6A  is a right side elevational view of the example lampholder. 
           [0014]      FIG. 6B  is a right side elevational view of the example lampholder showing the interior of the lampholder housing. 
           [0015]      FIG. 7  is a rear perspective view of the example lampholder. 
           [0016]      FIG. 8  is a right side elevational view of the example lampholder showing insertion of the tube lamp into the lampholder. 
           [0017]      FIG. 9  is a right side elevational view of the assembly of  FIG. 8  showing the tube lamp fully inserted into the lampholder. 
           [0018]      FIG. 10A  is a right side elevational view of the assembly of  FIG. 9  showing the tube lamp rotated into an installed position. 
           [0019]      FIG. 10B  is a top plan view of the assembly of  FIG. 10A . 
           [0020]      FIG. 11  is a rear perspective view of another example lampholder in accordance with another example of the teachings of the present disclosure. 
           [0021]      FIG. 12  is a rear perspective view of the lampholder of  FIG. 11 , showing the interior of the example lampholder housing. 
           [0022]      FIG. 13  is a front elevational view of the lampholder of  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The following description of example methods and apparatus is not intended to limit the scope of the description to the precise form or forms detailed herein. Instead the following description is intended to be illustrative so that others may follow its teachings. 
         [0024]    In general, in one example, the present disclosure provides for a three terminal lampholder that assures the ground (earth) terminal of the lamp, such as, for example an LED lamp, makes first contact and break last relative to the power terminals. More particularly, as described herein, the example lamp includes a three terminal design, having two contact terminals and a ground terminal. In operation, as the lamp is inserted into the lampholder, the ground terminal of the lamp makes contact with a ground terminal of the example lampholder. In this instance, once the lamp is fully inserted, the ground terminal is fully engaged, and the power terminals are not yet energized as they do not contact the power terminals of the lampholder. The lamp may then be rotated to electrically couple the power contacts of the lamp and lampholder. The example lampholder may be self-grounding as the ground terminal may be in contact with the luminaire metal to provide a ground path without external wiring between the lampholder and the luminaire. 
         [0025]    In another example, the present disclose may provide for the use a self-grounding terminal in a single terminal lampholder such as the ground end of a GX16t-5 as previously discussed. As with the ground terminal of the example three-terminal design disclosed herein, the single terminal lampholder may be provided with an exposed portion to self-ground the terminal to the luminaire. 
         [0026]    Referring now to  FIGS. 1 and 2 , an example lampholder  10  for grounding an example tube-type lamp  12  is illustrated. In this example, the lamp  12  is an LED tube-type lamp, although the lamp  12  may be any suitable type of lamp as desired. The example lampholder  10  includes a lampholder housing  14 , which in this example comprises an upright housing portion  16  and a base portion  18 . The upright housing portion  16  is adapted to releasably retain the contact terminals of the lamp  12  as will be discussed. The example base portion  18 , meanwhile, is adapted for connection to a luminaire plate of other suitable surface. The housing  14  defines an interior space  20 , in which the example lampholder  10  houses three contacts  22 ,  24 , and  26 , electrically isolated from one another. In this example, two of the contacts  22 ,  26  are arranged to electrically couple to a corresponding power terminal  23 ,  27 , respectively, provided on an end cap  13  of the lamp  12 . Similarly, the third contact  24  is arranged to electrically couple to a corresponding ground terminal  25 , also provided on the end cap  13  of the lamp  12 . 
         [0027]    In this example, the two power terminals are radially offset from a longitudinal axis L of the lamp  12 , while the ground terminal  25  is generally coaxially aligned with the axis L. Thus, as will be appreciated, rotation of the lamp  12  about the axis L will changed the position of the power terminals  23 ,  27 , while maintaining the general position of the ground terminal  25 . 
         [0028]    As shown in  FIGS. 1-4 , an insertion slot  30  for receiving the three terminals  23 ,  25 ,  27  is defined by the housing  14 . The insertion slot  30  extends inward towards the base portion  18  and is sized to receive the terminals  23 ,  25 ,  27  therein. The insert slot includes a pair of arcuate flanges  32 ,  34  extending from the housing  14  and arranged inside the interior space  20 . The flanges  32 ,  34  are shaped such that the fully inserted lamp  12  may rotate in the lampholder  14  such that the terminals  23 ,  25 ,  27  can be pivoted outside of the outer surface of the flanges  32 ,  34  to electrically couple to the contacts  22 ,  24 ,  26 . As will be appreciated by one of ordinary skill in the art, the outer surface of the flanges  32 ,  34  may include at least one notch, cut-out, and/or other detent proximate the contacts  22 ,  26  to provide a retention location and/or visual or physical feedback to the installer that the lamp  12  is properly rotated and retained in the lampholder  14 . 
         [0029]    Still further, it will be understood by one of ordinary skill in the art that the housing  14  may comprise, for example, multiple parts molded and/or otherwise formed and assembled to form the housing. In this manner, the contacts  22 ,  24 , and  26  may be provided in the interior space  20 . Additionally, the interior space  20  may include at least one support structure (not shown) for supporting and/or otherwise maintaining the contacts  22 ,  24 , and  26  within the interior space  20  and in electrical contact with an installed lamp  12  as is well known in the art. 
         [0030]    Turning to  FIG. 5 , an illustration of the example contacts  22 ,  24 , and  26  is shown without the remaining parts of the lampholder  14 . As can be seen, in this example, the contacts  22 ,  24 , and  26  each include a push-in type electrical connector at a first end  22   a ,  24   a , and  26   a , respectively. The push-in type connector allows for the insertion of an electrical wire, post, and/or other suitable connector (as desired) through apertures defined in the base portion  18 . similarly, each of the contacts  22 ,  24 ,  26  are constructed of any suitable electrical conductor, such as a resilient, conductive metal. The flexible material allows the contacts  22 ,  24 ,  26  to flex and/or move towards a bias to maintain the electrical connection as necessary. 
         [0031]    While the ground contact  24  can include an inserted ground wire attached to the push-in type connector  24   a , as illustrated in  FIGS. 5-7 , the ground contact  24  may also and/or alternatively include a self-grounding extension  40 . As noted, most luminaire use a base  42  ( FIG. 6A ,  6 B) such as a metal structure as a ground path. The example self-grounding extension  40  of the example lampholder  10  allows the ground contact  24  to be in contact with the base  42  to provide a ground path without requiring additional wiring to the lampholder  10 . More particularly, the example extension  40  is constructed to be exposed outside of the housing  14  through a slot  44  ( FIG. 7 ) such that the contact  24  is exposed to contact and connect with the metal base  42  of the luminaire. In the presently illustrated example, the extension  40  includes a relatively sharp and/or hard edge that can cut through any surface treatment (e.g., paint) to contact the metal base  42  when properly installed. 
         [0032]    Referring now to  FIGS. 8-10B , to insert the example lamp  12  into the example lampholder  10 , the lamp  12  is inserted with its power terminals  23 ,  27  and its ground terminal  25  into the insertion slot  30  ( FIG. 8 ) until both power terminals  23 ,  27  and the ground terminal  25  are fully inserted into the lampholder  10  ( FIG. 9 ). In this configuration, it can be seen that the ground terminal  25  of the lamp  12  makes contact with the ground contact  24 . In other words, the ground contact is the first contact. It will be appreciated, however, that while the present lamp  12  is inserted radially into the housing, the lamp  12  may be inserted axially into the housing  14  as desired. 
         [0033]    By rotating the lamp  12  about the longitudinal axis L in any direction, such as for example, in the direction of the arrow A ( FIG. 9 ), the power terminals  23 ,  27  override the resilient bias of the contacts  22 ,  26 , allowing the power terminals  23 ,  27  to rotate about and be guided by the flanges  32 ,  34 . Once fully rotated ( FIGS. 10A and 10B ), the power terminals  23 ,  27  push the resilient terminals  24 ,  26  to the side against their bias and as a result the power terminals  23 ,  27  are retained and an electrical contact is produced. The lamp  12  is now ready to operate. It can be seen in the above illustrations that throughout the installation process, and as held in the operating position, the ground contact is first to be created, and is maintained throughout. 
         [0034]    To withdraw the lamp  12 , the process is repeated and the lamp is rotated again in any direction about its longitudinal axis L to align the terminals  23 ,  25 ,  27  in the insertion slot  30 . As a result, the power terminals  23 ,  27  once again are disconnected from the contacts  22 ,  26 , while the ground connection is maintained between the ground terminal  25  and the ground contact  24 . In other words, the ground connection is the last to be broken. Once fully rotated, the lamp  12  can be withdrawn from the lampholder  10 . 
         [0035]    In the presently illustrated example, both when being inserted and when being withdrawn, the power terminals  23 ,  27  do not touch any live circuit part when they are pushed into or withdrawn from the insertion slot  30 . It will be appreciated, however, that the terminals  23 ,  27  and/or the contacts  22 ,  26  may be modified in shape such that the lamp  12  does not need to be rotated and/or may only be required to be rotated an amount other than the ninety degrees illustrated above. In either case, the ground connection is the first connection made during insertion of the lamp  12  into the lampholder  10  to provide a constantly grounded circuit. 
         [0036]    A further example of a self-ground lampholder  100  is illustrated in  FIGS. 11-13 . In this example, the lampholder  100  is adapted to accept an end of a lamp (not shown) in a housing  114  having a single ground terminal. Lamps of the single ground contact type are well known in the art, including, for example, a GX16t-5 lamp. In this example, the housing  11  of the lampholder  100  is similarly constructed to the lampholder  10 , but for a modification in the insert slot  130 , the interior space  120 , and the inclusion of a single contact. In the instance, the lampholder  100  is provided with a single ground contact, which in this example is defined by a first ground contact  124   a  and a second ground contact  124   b . It will be appreciated by one of ordinary skill in the art that while the single contact comprises a first contact  124   a  and a second contact  124   b , the contact may be formed from any number of portions, including a single contact portion. 
         [0037]    As the example GX16t-6 lamp includes a cylindrical ground post, the first ground contact  124   a  and the second ground contact  124   b  together form a generally arcuate shape  125  corresponding to the outer shape of the ground contact of the lamp. Upon insertion of the lamp into the lampholder  100 , the lamp is free to rotate about the ground contact as desired without breaking contact with the ground terminals  124   a ,  124   b.    
         [0038]    In the illustrated example each of the ground contacts  124   a  and  124   b  include a grounding extension  140   a ,  140   b , respectively, extending from the housing  114  through apertures or slots  144  defined by the housing  114 . As with the previous ground contact  24 , in this instance, the example contact extensions  140   a ,  140   b  allow the ground contacts  124   a ,  124   b  to be in contact with a base  142  to provide a ground path without requiring additional wiring to the lampholder  100 . 
         [0039]    Although certain example methods and apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.