Patent Publication Number: US-6217195-B1

Title: Lamp with safety shutoff features

Description:
RELATED APPLICATIONS 
     This application claims priority from U.S. provisional application Ser. No. 60/043,434 filed on Apr. 7, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lamp generally and, more particularly, to an improved floor lamp having safety features to prevent risk of fire and injury to persons. 
     2. Description of the Prior Art 
     Presently available standing floor lamps and, more particularly, lamps commonly referred to as “torchiere” halogen floor lamps, are known to produce a significant amount of heat from the 300 watt halogen light bulbs used therein. The heat of these light bulbs is a potential fire hazard as well as a burn hazard to persons coming in contact with the top portion or shade of the torchiere lamp or the halogen bulb itself. 
     Generally, manufacturers of these types of lamps provide warnings to the consumers with respect to potential fire and injury hazards which may be caused by extremely hot halogen lamps. Such warnings may include a tag attached to the power supply cord or a label attached to the inside of the shade near the halogen bulb to warn consumers of the potential burn hazard when changing a halogen bulb. To date, no manufacturer of torchiere style lamps provides any sort of built-in safety feature to protect the consumer from risk of fire or injury due to burns. Accordingly, the present invention is directed to providing safety features for the halogen torchiere style lamps to provide protection to the consumer against risk of fire and injury. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a lamp which includes safety features to prevent potential fire hazards. 
     It is another object of the present invention to provide a lamp having means for preventing a person from contacting the halogen bulb and risking possible injury due to burning and to prevent objects from coming in contact with the halogen bulb to prevent potential fire hazards. 
     It is yet a further object of the invention to provide a lamp having a thermostatic control which is responsive to ambient temperature in the cavity of a shade of an operating lamp which terminates power to the lamp upon air temperature within the shade reaching a predetermined temperature. 
     It is still a further object of the present invention to provide a lamp having a thermostatic safety feature in which the thermostat will not reset until power to the lamp is terminated for a period of time. 
     It is yet another object of the present invention to provide a safety switch which will terminate power to the lamp upon an object being placed within the open end of the shade. 
     It is still a further object of the present invention to provide a lamp having a sensor for terminating power to the lamp should an object be detected as being placed over the lamp by the sensor. 
     In accordance with one form of the present invention, an electric lamp includes a base for supporting the lamp and a stem portion having a first end coupled to the base and the second end coupled to a light bulb socket. The electric lamp further includes an electrical circuit for providing power to the light bulb socket, the circuit including an on/off switch and a thermostatic switch serially connected to the light bulb socket. The thermostatic switch is responsive to ambient air temperature such that, upon reaching a predetermined value, power to the light bulb socket is terminated or shut off. Preferably, the thermostatic switch includes a means for maintaining the switch in an open circuit position until power to the lamp is turned off for a period of time to allow the thermostatic switch to reset thereby permitting normal operation of the lamp. The means for maintaining the thermostatic switch may be in the form of a resistive heating element. When the thermostatic switch opens in response to ambient air temperature reaching the predetermined value, current is directed to the resistive heating element which maintains the ambient air temperature in the vicinity of the thermostatic switch above the predetermined value thereby preventing the thermostatic switch from resetting. Only upon termination of power to the lamp, e.g., turning the on/off switch to the off position or unplugging the lamp, will the thermostatic switch be allowed to cool down and reset. 
     Although the thermostatic switch and resistive heating element may each take many forms, the preferred embodiment of the present invention includes a thermostatic switch which is a bimetallic switch and a ceramic resistive heating element. 
     In order to provide a margin of safety with respect to fire hazards and potential personal injury, the predetermined temperature at which the thermostatic switch opens the electrical circuit is about 65° C. Furthermore, the thermostatic switch is preferably mounted in close proximity to the light bulb socket to sense the ambient air temperature in the hottest region of the lighting fixture. 
     Although the present invention may be used with any type of lamp, the safety features of the present invention are particularly useful with respect to halogen torchiere floor lamps. Such lamps use high intensity halogen bulbs, usually 300 watts. These lamps create significant heat and potential fire and personal injury hazards. These types of lamps usually include a bowl-shaped shade provided at the second end of the stem. To direct light in an upward direction, the shade includes positioned therein a reflector. Such lamps also include a dimmer means for controlling the intensity of illumination provided by the lamp. 
     The present invention also discloses a halogen torchiere floor lamp including a base for supporting the lamp, an elongated hollow stem having a first end coupled to the base and a shade coupled to the second end, a light socket positioned within the shade for receiving a halogen bulb and an electrical circuit means for providing power to the lamp. The halogen floor lamp further includes a protective guard mounted within an interior portion of the shade. The protective guard is positioned over at least a portion of the halogen bulb mounted within the light socket thereby obstructing access to the light socket and bulb with minimal obstruction of light. The protective guard is preferably a convex-shaped wire, but it is envisioned that the protective guard may take many different forms. The halogen floor lamp may also include a reflector located in a bottom portion of the shade and wherein the protective guard is mounted to opposite edges of the reflector. 
     The present invention also discloses an electrical circuit including a detector for sensing when an object is placed within the shade of the lamp and generates a signal in response thereto. The electrical circuit further includes a switching device for terminating power to the lamp in response to the signal generated by the detector. In a preferred embodiment, the detector is a phototransistor which energizes a relay coil upon detection of an object within and/or over a portion of the lamp shade. The changing state of the relay terminates power to the dimmer control module or the power supply to the lamp socket to shut the lamp off. Alternatively, the detector may be a safety switch having an actuator. Upon an object being placed within the lamp shade and in contact with the switch actuator, power to the lamp socket is terminated until the object is removed. 
     A preferred form of the standing floor lamp, as well as other embodiments, objects, features and advantages of this invention, will be apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a standing floor lamp formed in accordance with the present invention; 
     FIG. 2 is a top plan view of the standing floor lamp formed in accordance with the present invention; 
     FIG. 3 is a cross-sectional view of the shade portion of the standing floor lamp formed in accordance with the present invention; 
     FIG. 4 is an electrical schematic of the circuit associated with the lamp formed in accordance with the present invention; 
     FIG. 5 is a side view of the protective guard shown in FIG. 2 formed in accordance with the present invention; 
     FIG. 6 is a top plan view of an alternative embodiment of the protective guard formed in accordance with the present invention; 
     FIG. 7 is a cross-sectional view shade of a floor lamp including a safety switch formed in accordance with the present invention; 
     FIG. 8 is an electrical schematic including a thermostat and a safety switch formed in accordance with the present invention; 
     FIG. 9 is an electrical block diagram illustrating a protection circuit including a sensor formed in accordance with the present invention; and 
     FIG. 10 is an electrical circuit used in connection with the embodiment of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention relates to safety features for lamps and, more particularly, for halogen torchiere-type standing floor lamps. Although the present invention is described herein for use with a torchiere lamp, it is envisioned that these safety features could be used in conjunction with any type of lighting fixture. As illustrated in FIG. 1, a torchiere lamp  10  formed in accordance with the present invention includes a lamp base  2  for supporting the fixture, an elongated stem  4  having a first end attached to a central portion of the base  2  and a second end coupled to a bowl-shaped shade  6 . The stem is hollow and includes a rotary switch  8  for controlling the on/off function of the power supply to the lamp. Furthermore, the switch  8  has associated therewith a dimmer switch for controlling the intensity of the lamp in the on position. Lastly, the lamp includes a power cord  12  which can be plugged into any standard AC electrical outlet. 
     FIG. 2 is a top plan view of the shade portion  6  of the lamp formed in accordance with the present invention. Within the shade portion of the lamp there is a reflector  14  which substantially reflects the light from the lamp in an upward direction. Positioned within the reflector is the halogen bulb  16  which is seated within a socket  18 . The socket  18  is electrically connected to the rotary switch  8  and ultimately the power source through power cord  12 . The reflector formed in accordance with the present invention includes several slots  22  through the thickness thereof Lastly, FIG. 2 illustrates a top view of a protective guard  20  which is positioned across and over at least a portion of the halogen bulb and mechanically connected to edges of the reflector  14 . 
     Referring to FIGS. 2 and 5, the protective guard  20  has a substantially convex shape and is positioned perpendicular to the axis of the halogen bulb  16 . The protective guard  20  may take any shape or form, e.g., a cage, as opposed to a single bar as shown in FIG.  5 . The protective guard  20  will prevent a person from reaching up into the bowl portion of the lamp and possibly coming in direct contact with an extremely hot halogen bulb. Additionally, should something be placed over the shade  6 , the protective guard  20  will keep such articles from directly contacting the halogen bulb. The protective guard  20  of the present invention provides the desired safety feature while obstructing the minimal amount of light produced by the lamp. Preferably, the protective guard formed in accordance with the present invention is made from a metal wire having mounting holes formed at opposite ends thereof. Machine screws  24  may be used to attach the protective guard to the edges of the reflector housed within the lamp shade  6 . As previously noted, the protective guard may take the form of an open wire cage (not shown) to provide even more protection against possible contact with a potential burn hazard. As illustrated in FIG. 6, the protective guard, i.e., protective guard  20 ′, may be formed from two wires crossed in the middle. 
     FIG. 3 is a cross-sectional view of the top shade portion  6  formed in accordance with the present invention. As illustrated in FIG. 3, the reflector  14  is mounted to a lower surface of the shade  6 . The reflector includes positioned therein the sockets  18  for receiving a halogen bulb  16 . Also illustrated in FIG. 3 is protective guard  20  which extends over the bulb mounted in the sockets. 
     The present invention is directed toward safety features for torchiere type halogen lamps. Accordingly, a torchiere lamp formed in accordance with the present invention includes a thermostat switch to prevent overheating of the lamp and a possible fire hazard. The thermostat switch  30 , as illustrated in FIG. 3, is located in close proximity to the halogen bulb, namely, the area between the reflector  14  of the lamp and the metal shade  6 . 
     FIG. 4 is a circuit diagram for the torchiere lamp formed in accordance with the present invention. The circuit includes a power source for providing AC power to the lamp. The power source is connected in series with a switch SW 1  which includes an on/off switch  28  in combination with a dimmer switch  32  so that the intensity of the light may be varied from a dim glow to a high intensity. Any known dimmer switch circuitry may be used. For example, a dimmer circuit using a triac has proven to work well in rotary on/off switches, used for lighting fixtures. In normal operation, the switch SW 1  will control the intensity of the illumination from the lamp. 
     To provide the safety feature of the lamp formed in accordance with the present invention, a thermostat is connected in series between the switch SW 1  and the socket  18  for the halogen bulb  16 . Preferably, the thermostat includes a bimetallic contact  34  and a parallel connected heating element  36 . As illustrated in FIG. 3, the thermostat  30  is mounted in close proximity to the halogen bulb  16 . Furthermore, as illustrated in FIG. 2, the reflector  14  includes slots formed therein so that heat is readily transferred to the area in which the thermostat is mounted. If the temperature of the ambient air surrounding the thermostat reaches a predetermined temperature based upon the rated temperature of the thermostat, the bimetallic contact will change from a short circuit to an open circuit and the voltage supply is then applied across the heating element  36 . Preferably, the heating element is a ceramic element which has been heated by the ambient air and, upon current being applied to the element, generates sufficient heat to maintain the bimetallic contact in an open position until power to the lamp is disconnected by either turning the switch to the off position or unplugging the lamp. Only power disruption will allow the ceramic heating element to cool down and permit the bimetallic element to return to a closed position thus allowing the lamp to operate under normal conditions again. Preferably, the ceramic heating element is a limiting resistor so that current is limited to only the current necessary to maintain the bimetallic contact in an open position. This limited current will not be sufficient to illuminate the halogen bulb. 
     It will be understood by those of ordinary skill in the art that the thermostat may take many forms. However, in the preferred embodiment, to provide for extra safety, a thermostat which cannot reset until power to the lamp is disconnected is most desirable. Such a thermostat is manufactured by Micro Therm under part no. A71C65-5. In the preferred embodiment, the predetermined temperature for the bimetallic contact to open is 65° C. Furthermore, the time required for the ceramic element to cool and the bimetallic contact to once again reset and close is preferably a sufficient amount of time to allow the entire lamp assembly to cool down, i.e., approximately 10 minutes. Once the bimetallic contact has reset to a closed condition and the ceramic heating element has been allowed time to cool, the lamp will be able to operate under normal conditions. 
     Generally, overheating conditions occur if an obstruction to the air flow occurs in the area of the shade  6  thus causing the temperature to rise to an unacceptable level. For example, a curtain or other drapery may be in close proximity to a torchiere lamp similar to that formed in accordance with the present invention. Due to the extremely high temperatures generated by a 300 watt halogen bulb, it is possible that the drapery may ignite causing a fire. The present invention including a circuit having a thermostat to terminate power to the lamp upon ambient air temperature around the lamp reaching a predetermined set point, provides greater safety and substantially eliminates any fire hazard. Accordingly, the halogen torchiere lamp formed in accordance with the present invention overcomes the disadvantages of prior art lamps and provides greater safety to the consumer. These safety features include both the thermostat cutoff as well as the protective guard positioned above the halogen lamp to prevent possible injury caused by burns due to the heat generated by a 300 watt halogen lamp. 
     In one particularly preferred embodiment, the protective guard, i.e., protective guard  50  shown in FIG. 7, includes a pair of elongate intersecting wire members, i.e., lower wire member  52  and upper wire member  54 , which each span from one side of reflector  14  to other side, thus forming an X-shaped dome structure which obstructs access to the halogen bulb by such objects as drapes and curtains without significant blockage of light. Wire members  52 ,  54  are preferably spaced 90° apart from one another about the upper periphery of reflector  14 . Of course, it is contemplated herein that the protective guard could employ more than two wire members. It is also contemplated that the members of the protective guard could be secured to the shade or the light socket rather than the reflector. 
     The wire member  52  may include a U-shaped detent formed at the center thereof The U-shaped detent is sized to receive wire member  54  therein. As will be appreciated by those skilled in the art, wire member  54 , once captured within U-shaped detent, is substantially locked in an upright, vertically oriented position, i.e., it is unable to rotate about the reflector. Each of the wire members preferably has an arch-like configuration to enhance the structural rigidity of the resultant protective guard structure. 
     As will be appreciated by those skilled in the art, it is desirable that the protective guard be installed at the factory, leaving little or no assembly left for the end user upon unpackaging of the lamp. Although protective guards such as protective guard  20  provide the required degree of protection, the rigid non-rotatable members employed in such structure either  1 ) require that the structure be assembled by the purchaser after unpackaging the lamp or  2 ) require its own unique packaging (as compared to packaging for lamps without such guard structures). However, it has been discovered herein that protective guard  50  can be installed on the lamp at the factory and still be packaged in the same packaging used for lamps without such guard structures. 
     In one embodiment, the protective guard structure includes guard members which are permanently fastened to opposing sides of reflector  14  (or alternatively to the shade), but are sufficiently flexible as to allow collapsing thereof for packaging. As shown in FIG. 7, the protective guard structure, i.e., protective guard  50 , includes resilient guard members  52 ,  54 . Also shown is a safety switch  60  which terminates power to the lamp should an object come in contact with the switch. Guard members  52 ,  54  are attached to the reflector by, for example, sheet metal screws. Because the guard members are formed from a resilient material, they may be collapsed for packaging of the lamp and are flexible enough to engage an actuator  60  of a safety switch  62  should an object be placed in contact with the protective guard. Once unpackaged, the resilient guard members return to the dome configuration, thus providing a protective guard structure which obstructs access to the halogen bulb while minimizing obstruction of light from the bulb. It will be appreciated by those skilled in the art that the safety switch may be placed anywhere within the lamp shade to detect if a foreign object is situated within the shade. A more detailed description of the electrical circuit associated with the safety switch appears below. 
     It will be readily apparent to one skilled in the art, and envisioned to form part of the invention to use similar components, although not necessarily identical to those described in the preferred embodiment to provide the safety features discussed herein. Specifically, many different types of thermostats may be used as well as many types of designs for the protective guard. 
     To further enhance the safety of the lamp and avoid fire and burn hazards, the lamp of the present invention may include an electrical circuit  100  as shown in FIG. 8 having a thermostat  102  and a safety switch  104  connected in series with a bulb  106  of the lamp. The thermostat  102  and the switch  104  are preferably mounted in close proximity to the lamp&#39;s bulb within the lamp shade, although many suitable locations for each switch will be readily known to those of ordinary skill in the art. Upon the ambient air temperature in the vicinity of the thermostat reaching a predetermined temperature, the thermostat effectively opens the electrical circuit, shutting the lamp off. As earlier discussed, the thermostat preferably includes a heating element to maintain the open circuit and once power is turned off for a period of time, the thermostat can reset and the lamp may be operated again. 
     As earlier discussed, the present invention also discloses a protective guard which is positioned over at least a portion of the bulb of the lamp. Referring to FIG. 7, the guard is either formed of flexible material or may be spring loaded and upon an object coming to rest on top of the guard, the guard will be pushed downward. When the guard comes in contact with the actuator  60  of the switch  63 , the electrical circuit opens thus shutting off the lamp. When the object is removed from the guard, the lamp may again be operated normally. The switch  62  may be located in any convenient location within the interior space of the lamp shade to detect a foreign object being placed therein. Additionally, the switch may take many forms which will be well known to those of ordinary skill in the art. 
     Referring to FIGS. 9 and 10, an alternative embodiment of the present invention including a sensor for detecting when an object is placed on or falls on top of the lamp is illustrated. 
     Referring to FIG. 9, the protection circuit includes an infrared photo transistor  202  for sensing reflected energy when an object is placed over or within the shade of the lamp. The protection circuit preferably includes a DC power supply  204  (converted from the AC input) electrically connected to a control module  206 . The infrared phototransistor  202  is electrically connected to the control module and provides an input thereto. Upon an object being sensed by the infrared phototransistor  202 , the control module  206  sends a control signal  207  to a dimmer module  208  to terminate power to the lamp  20 . 
     Referring to FIG. 10, a more detailed circuit schematic of the protection circuit of FIG. 9 is shown. The phototransistor may take any known form and preferably is an NPN infrared phototransistor Q 1 . The protection circuit also includes a current limiting resistor R 1  (470 Ω). The DC power supply  204  is preferably provided by a transformer T 1  having a 6.2 VAC secondary winding. The secondary winding is electrically connected to a bridge rectifier B 1 , preferably 50 V or greater. The DC power supply further includes two capacitors, capacitor C 1  (47 μf at 16 V) which acts to eliminate DC ripple and a decoupling capacitor C 2  (0.1 μf) to eliminate any high frequency component of the DC output. 
     The protection circuit  200  of FIG. 10 is activated as follows: 
     1) Reflected infrared energy from the light is directed into the phototransistor Q 1 . 
     2) The phototransistor Q 1  conducts and thereby pulls gate current through silicon controlled rectifier SCR 1  and energizes the coil of relay K 1  (5 VDC SPST relay). 
     3) Relay K 1  contacts open. A suitable light sensitive dimmer switch circuit for use with the protective circuit  200  is disclosed in commonly-owned U.S. patent application Ser. No. 08/714,896, filed on Sep. 17, 1996, the disclosure of which is incorporated herein by reference. When the relay contacts are non-conducting or open the DIAC signal path to the TRIAC, both located in the lamp dimmer module as set forth in U.S. patent application Ser. No. 08/714,896 is opened, thus terminating power to the light bulb socket. 
     4) Gate current through SCR 1  maintains relay coil K 1  energized thereby keeping the lamp de-energized until the lamp switch is turned off, or the power line cord is removed from power receptacle, allowing the protection circuit to reset. 
     In an alternative embodiment in which the lamp does not include a dimmer module as defined herein, the relay K 1  contacts are electrically connected to control the power supply to the lamp socket thus terminating power to the lamp in response to a signal from the phototransistor. 
     Although, illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modification may be effected therein by one skilled in the art without departing from the scope or spirit of the invention.