Abstract:
An end cap for a light-emitting-diode (LED) light tube includes an end cap housing having an end surface, an electric circuit and a switch for closing the electric circuit or opening the electric circuit. The switch includes a switch body having a pivot axis. The switch body is configured to pivotally move, with respect to the pivot axis, between an on-position for closing the electric circuit and an off-position for opening the electric circuit. When the switch is in the off-position, an end part of the switch body protrudes from the end surface of the end cap housing, and when the switch is in the on-position, the switch body and is substantially flush with respect to the end surface. When the switch is in the off-position, an outer surface of the switch body inclines with respect to the end surface of the end cap housing.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to an end cap for a light tube, in particular, a light emitting diode (LED) light tube. More specifically, the present disclosure relates to an end cap having a protective switch therein. 
       BACKGROUND 
       [0002]    A fluorescent tube lamp  100  is one of the most widely used lighting technologies today, because fluorescent tubes are more energy efficient than incandescent lamps.  FIG. 1  shows an example of a typical fluorescent tube lamp assembly. In recent times, lamps utilizing light emitting diodes have been utilized for their lower energy consumption and longer life, thereby replacing incandescent lamps, compact fluorescent lamps and fluorescent tubes. 
         [0003]    An LED lamp  110  as a replacement for a fluorescent tube  100  typically includes several tens or hundreds of small LEDs  111  assembled on one or more printed circuit boards  115 . The LED circuit board(s) is typically enclosed in a housing including a metallic housing  116  and a transparent plastic housing  117 . The metallic portion  116  of the housing acts as a heat dissipater while the plastic portion  117  of the housing protects the LEDs from external environments.  FIG. 2  shows an example of an LED light tube assembly. 
         [0004]    Since the LED light tube is a replacement of the fluorescent tube, an end cap structure  112  for the LED light tube is compatible with an end cap  102  for the fluorescent tube lamp. In the fluorescent tube lamp and the LED light tube lamp, two bi-pin end caps are typically disposed on each end of the tube (see,  FIGS. 1-3 ). In some applications, instead of bi-pin end cap  102 , a single-pin end cap  103  may be utilized (see.  FIG. 4 ). 
         [0005]    The fluorescent tube lamp is connected to a power source by being inserted to sockets  104 . The fluorescent lamp is operated by allowing electricity to pass through the fluorescent tube via the bi-pins from one end to another end of the tube. The fluorescent tube is operable regardless of the orientation of the tube when the tube is inserted into the sockets of tube holders. Typically, the fluorescent tune lamp is utilized together with a fluorescent tube ballast and a starter. 
         [0006]    When the LED light tube is utilized to replace the fluorescent tube in a lighting fixture, the fluorescent tube ballast and starter, if any, are removed from the lighting fixture during installation of the LED light tube. The sockets are then wired directly to AC main power lines including a power line and a neutral line (i.e., a ground line). 
         [0007]    As set forth above, the LED light tube typically includes metallic portion  116 . The metallic portion of the LED light tube functions to dissipate heat away from the LEDs, a printed circuit board and a LED driver into the air through convection. However, the metallic portion  116 , typically made of extruded aluminum, is electrically conductive as well. This may cause an electrical hazard when there is any leakage from an internal circuit or the AC power lines to the metallic portion. 
         [0008]    Accordingly, it has been necessary to implement a safety device that protects the user from electrical shock in case of electricity leakage. More particularly, a safety device will be necessary when the LED light tube is being inserted into the sockets of the tube holder of a lighting fixture. 
         [0009]      FIGS. 5 and 6  show one example of an end cap having a safety device in a known device. A cross sectional view of the internal mechanism of the conventional end-cap  201  is illustrated in  FIG. 6 . In this conventional example, an end-cap  201  for the LED light tube incorporates a push button switch assembly  203 . This push button switch assembly  203  is activated by a spring  205  connected to switch cap  202 , protruding from an end surface of the end-cap housing  204 . As the LED tube is inserted into the socket, the switch cap  202  is depressed by a wall of the socket and the switch cap  202  in turn pushes the button switch  206  located underneath the switch cap  202 , which are disposed inside the end-cap housing  204 . The button switch  206  closes an electrically open circuit by shorting two internal electrical terminals  211 ,  212  via a bridging contact plate  210  disposed at the end of the push button switch  206 . 
         [0010]    The push button assembly  203  in the conventional end-cap  201  poses a few problems in practice. One problem is that the push button  203  may sometimes fail to close the circuit and may not electrically connect the terminal  211  and  212  when the end cap  202  is depressed, because of the two springs  205  and  209 . More specifically, since the two springs  205  and  209  are connected in series, they may be insufficiently compressed to force the bridging contact plate  210  to be into contact with the electrical terminals  211  and  212 . Thus, it has been necessary to design the end-cap  201  such that the spring force and displacement thereof consistently deliver and release the necessary force to “open” and to “close” the circuit whenever the LED light tube is inserted into or taken out of the socket  104 . Failure to do so would cause unexpected turning-off of the LED light tubes or might cause electrical shock to the user. 
         [0011]    Furthermore, when the switch cap  202  is depressed, there is friction generated between the switch cap  202  and the cap housing  204  and between a push button shank and its housing when the shank slides inside the push button assembly  203 . These frictional forces often result in contact failures due to lack of connecting terminals  211  and  212 . 
         [0012]    Another problem with the conventional end cap switch is that the speed at which the bridging contact plate  210  connects electrically with the terminals  211  and  212  is generally slow, thereby causing “arcing” between the terminals. The arcing likely occurs when an air-gap between the terminals  211  and  212  is small enough for the electrical charges to build up between the bridging contact plate  210  and the terminals  211  and  212 . When a sufficient potential exists between the contacts, the electricity jumps across the air-gap. 
         [0013]    This arcing will cause the surfaces of the bridging contact plate  210  and the terminals  211  and  212  to erode and to form oxides that reduce electrical conductivity. This may result in an intermittent switch “off” problem. In a more severe situation, the arcing may also cause the terminals  211  and  212  to fuse with the contact plate  210 , resulting in a permanent switch “on” position. 
         [0014]    Accordingly, there is a need for an end cap switch for the LED tube lamps which overcomes the foregoing problems and which is more reliable and has a longer life. 
       SUMMARY 
       [0015]    In order to solve the problems associated with the conventional push-button type end-cap, the present disclosure addresses one or more needs for an end-cap for the LED tube lamps which has a quick action, is more reliable and has a longer life. 
         [0016]    In one exemplary embodiment, an end cap for a light-emitting-diode (LED) light tube includes an end cap housing having an end surface, an electric circuit and a switch for closing the electric circuit or opening the electric circuit. The switch includes a switch body and a pivot axis. The switch body is configured to pivotally move, with respect to the pivot axis, between an on-position for closing the electric circuit and an off-position for opening the electric circuit. When the switch is in the off-position, an end part of the switch body protrudes from the end surface of the end cap housing, and when the switch is in the on-position, the switch body and is substantially flush with respect to the end surface. When the switch is in the off-position, an outer surface of the switch body inclines with respect to the end surface of the end cap housing. 
         [0017]    In the exemplary end cap, the switch may further include a first spring. The first spring is configured to make the end part of the switch body protrude from the end cap housing when the switch is in the off-position. The first spring may push the end part of the switch body when the switch is in the off-position so that the end part of the switch body protrudes from the end surface of the end cap housing. In some cases, the first spring may pull another end part of the switch body when the switch is in the off-position so that the end part of the switch body protrudes from the end surface of the end cap housing. 
         [0018]    In the exemplary end cap, the switch further includes an extension member extending from the switch body and an arm member that is a part of the electrical circuit. The extension member is configured to move the arm member to close or to open the electrical circuit. 
         [0019]    In the exemplary end cap, the switch further includes a contact part, and the arm member has a curved portion and a contact portion. When the switch is in the on-position, the extension member is configured to make the contact portion of the arm member to contact the contact part so as to close the electrical circuit, and when the switch is in the off-position, the extension member is configured to make the contact portion of the arm member to be detached from the contact part so as to open the electrical circuit. 
         [0020]    The extension member may include a stud and a second spring elastically connecting the extension member and the stud. The end of the stud is configured to slide on the curved portion of the arm member. 
         [0021]    The exemplary end cap further includes a pin for receiving electric power. The pin protrudes from the end cap housing and is connected to the electric circuit. The pin may be a bi-pin including two pins or a single pin. 
         [0022]    The exemplary end cap may further include a switch housing for enclosing the switch. When the switch includes sub-elements such as the first spring, the extension member and/or the arm member, these sub-elements are also enclosed in the switch housing. The switch housing may have clip-on retainers, and the switch housing is retained to the end cap housing by the clip-on retainers. The switch housing may be hermetically sealed. 
         [0023]    In another example, a light-emitting-diode (LED) light tube includes an LED light tube member on which a plurality of light emitting diodes are disposed and an end cap as set forth above. The end cap is disposed on an end of the LED light tube member. Preferably, the end caps are disposed on both ends of the LED light tube member, respectively. In the exemplary LED light tube, the switch is in the on-position when the LED light tube is inserted into a socket of a lighting fixture and the switch is in the off-position when the LED light tube is removed from the socket. The end part of the switch body is configured to be pressed to the end cap housing by the socket when the LED light tube is being inserted into the socket so that the switch body becomes substantially flush with respect to the end surface. 
         [0024]    The end cap and LED light tube of the present disclosure, together with further objects and advantages, can be better understood by reference to the following detailed description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a view of a conventional fluorescent tube and the assembly thereof. 
           [0026]      FIG. 2  is a view of a conventional LED light tube and the assembly thereof. 
           [0027]      FIG. 3  is a view of a conventional end cap with bi-pin. 
           [0028]      FIG. 4  is a view of a conventional end cap with a single pin. 
           [0029]      FIG. 5  is a view of a conventional end cap with a push-button switch. 
           [0030]      FIG. 6  is a cross sectional view of the conventional end cap with a push-button switch. 
           [0031]      FIG. 7  is an exemplary cross sectional view of an end cap according to one embodiment of the present disclosure. 
           [0032]      FIG. 8  is an exemplary cross sectional view of an end cap according to one embodiment of the present disclosure. 
           [0033]      FIG. 9  is another exemplary cross sectional view of an end cap according to one embodiment of the present disclosure. 
           [0034]      FIG. 10  is an exemplary rear view of an end cap according to one embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. However, it should be apparent to those skilled in the art that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings. 
         [0036]    In an exemplary end cap of the present disclosure, a quick-action snap switch with spring back action is incorporated into the end cap for LED light tubes. The spring back action keeps the switch in an “open” position when the switch cap is not depressed. This spring back action is provided by a switch cap spring. 
         [0037]      FIGS. 7 and 8  illustrate one example of the end cap  10  with a quick-action snap switch  20 . The end cap  10  includes an end cap housing  40  and the switch  20 . The switch  20  includes a switch body  21  which has a pivot axis  22  which is fixed to the end cap housing  40 . The switch body  20  rotates around the pivot axis  22 . The end cap housing  40  has an opening  42  in which the switch is disposed. A switch cap spring  23  is incorporated at one end of the switch body  21  to keep the switch in an “open” position (see,  FIG. 7 ). The switch  20  is located on near the center of the end cap, or off-center of the end cap housing  40 . 
         [0038]    The switch  20  further includes a switch cap shank  24  extending from the switch body  21 , a spring  25  and a stud  26 . The switch cap shank  24  includes a tubular portion. The spring  25  and stud  26  are disposed inside the tubular portion of the switch cap shank  24 . The spring  25  keeps the stud  26  extending at the end of the switch cap shank  24 . The switch cap shank preferably extends from the pivot axis  22 . 
         [0039]    The switch  20  further includes a rocker arm  27 . The rocker arm  27  has a curved portion  27 A and a contact portion  27 B. The curved portion  27 A of the rocker arm  27  is disposed on a convex portion  28  (a bump) of the end cap housing so that the rocker arm can swing. The convex portion  28  works as a fulcrum and is an electric terminal electrically connecting to a terminal  42  disposed on the end cap housing  40 . The rocker arm  27  is placed in a cavity with a left and right slot securing the rocker arm in place. 
         [0040]    One end of the stud  26  is in contact with the curved portion  27 A of the rocker arm  27 . As shown in  FIG. 7 , when the switch body  21  is depressed (i.e., from “off” to “on”), the stud  26  swings from one end of the curved portion  27 A of the rocker arm  27  to the other end of the curved portion  27 A, thereby connecting the contact portion  27 B and a contact part  29  (a bump) of the end cap housing, which is electrically connected to a terminal  44  disposed on the end cap housing  40 . The terminal  44  is connected to one of the bi-pins  50  for receiving electric power from a socket, and the terminal  42  is connected to the LEDs disposed on a circuit board of the LED light tube member. Accordingly, when the switch body  21  is depressed, an electric path from the terminal  42  to the terminal  44  through the convex portion  28 , the rocker arm  27  and the contact part  29 , is closed, thereby supplying the electric power to the LEDs. 
         [0041]    When the stud  26  moves from one end to another of the rocker aim  27 , the moving action provides a “quick snap action” of the switch and generates a “click” sound. This “quick snap action” is advantageous because the electrical connection is quickly closed, reducing the effect of electrical arcing between the contact  27 B of the rocker arm  27  and the contact part  29 . The “quick snap action” also helps to reduce the erosion of the contact, as well as to minimize incidences of fusing of contacts due to a slow switching motion in the conventional end cap switch designs. 
         [0042]    The rocker arm  27  is preferably made of a low resistance material, for example copper. The contact portion  27 B of the rocker arm  27  is preferably made of for example, copper alloys (e.g., beryllium copper alloy), silver (e.g., silver plating) or nickel (e.g., nickel plating). Similarly, the convex portion  28  and the contact part  29  of the housing are preferably made of, for example, copper, silver (e.g., silver plating) or nickel (e.g., nickel plating). The outermost surface of the convex portion  28  and the contact part  29  may be plated with, for example, beryllium copper. 
         [0043]    On the other hand, when the switch body  21  is released from the depressed position (i.e., from “on” to “off”), the stud  26  swings back from the other end of the curved portion  27 A of the rocker arm  27  to the one end of the curved portion  27 A, thereby disconnecting the contact portion  27 B and the contact part  29  of the end cap housing (see,  FIG. 8 ). When the stud  26  moves, the moving action also provides the “quick snap action” and generates the “click” sound. This “quick snap action” reduces the effect of electrical arcing between the contact  27 B and the contact part  29 , and also reduces the erosion of the contact and minimizes incidences of fusing of the contacts. 
         [0044]    The end cap  10  is attached to the end of an LED light tube and terminal  44  is electrically connected to the circuit board for providing electric power to the LEDs. The end-cap  10  may be attached to the LED light tube by one or more screws or by a bonding material including, but not limited to, epoxy or silicone. 
         [0045]    When the LED light tube is inserted into, by a sliding motion, a socket of a lighting fixture, the switch  20  becomes depressed (i.e., in the on-position). More specifically, when the LED light tube is being inserted into the socket, the end part of the switch body  21  is pressed into the end cap housing by a wall of the socket of the lighting fixture. When the LED light tube is removed from the socket, the switch  20  transitions into the off-position. 
         [0046]    When the LED light tube is inserted into the socket and the switch  20  is in the “on” position, the top surface of the switch body  21  is substantially flush with respect to the end surface of the end-cap housing  40 . Here, “substantially flush” does not necessarily mean a perfectly flush state. Rather, the “substantially flush” refers to the state that the switch body  21  is pressed into the end cap housing  40 , and does not significantly protrude from the end cap housing. 
         [0047]    In the “off” position, the outer surface of the switch body  21  inclines with respect to the end surface of the end cap housing (see,  FIG. 8 ) because of the force provided by the spring  23 . It is noted that in this example, the spring  23  is arranged at one end of the switch body  21  and provides a “push” force to the switch body  21 . It is, however, possible to arrange the spring  23  at the other end of the switch body  21 , thereby providing a “pull” force for making the switch body inclined. 
         [0048]      FIG. 9  shows one example of the end cap according to another embodiment of the present disclosure. In this example, the switch  20  is enclosed by a switch housing  60  except for the bi-pins. The switch housing  60  is a separate housing from the end cap housing  40  and can be inserted into an opening of the end cap housing  40 . The switch housing may enclose all of the sub-elements of the switch, such as the springs  23 ,  25 , the switch cap shank  24 , the stud  26 , the rocker arm  27  and the contacts  28  and  29 . The switch housing includes the electrical terminals  42  and  44  disposed outside the switch housing. The terminals  42  and  44  may have screws for receiving metal wires. 
         [0049]    The switch housing is made of plastic, and is secured to the end cap housing  40  by means of clip-on retainers  62 . The clip-on retainers include “claws” disposed on the sides of the switch housing  60 , thereby retaining the switch housing to the end cap housing. The switch housing may be hermetically sealed, thereby providing protection against the external environment and preventing moisture or dust from intruding. Such a sealing extends the life of the end cap. 
         [0050]    As shown in  FIG. 10 , the exemplary end cap  10  further includes a ridge  49  at the bottom of the end cap housing. The ridge  49  facilitates assembling of the end-caps to the LED light tube. 
         [0051]    One of the advantages of the end cap switch of the present structure is that the end cap switch of the present disclosure can consistently deliver and release the necessary force to “open” and to “close” the electric circuit whenever a LED light tube is inserted into or taken out of a socket of a lighting fixture. Another advantage is that the end cap switch of the present disclosure can suppress arcing or fusing of electrodes. Moreover, the end cap of the present disclosure is more reliable and has a longer life than the conventional end cap switch. 
         [0052]    Although certain specific examples have been disclosed, it is noted that the present teachings may be embodied in other forms without departing from the spirit or essential characteristics thereof. The present examples described above are considered in all respects as illustrative and not restrictive. The patent scope is indicated by the appended claims, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.