HK1150650B - Inductively powered lamp assembly - Google Patents

Description

Inductively powered lamp assembly

This application is a divisional application of a patent application having the same name as the patent application having application number 02829228.6 and having application date 6/7 of 2002.

The present invention is a continuation-in-part application of U.S. patent application No.90/592,194 entitled Fluid Treatment System filed on 12/6/2000.

Technical Field

The present invention relates to lighting devices, and more particularly to lamp assemblies associated with inductive power lighting applications.

Background

Although not very widely used, inductively coupled lighting systems are known. Conventional inductively coupled lighting systems generally include a primary circuit having a primary coil (or "primary coil") driven by a power source, and a secondary circuit having a secondary coil (or "secondary coil") that inductively receives the primary coil power. Inductive coupling has several advantages over conventional direct electrical connections. First, inductively coupled lamps are safer and easier to connect and disconnect than hardwired lamps. Direct electrical connection typically necessitates operation of the electrical connector when installing and removing the lamp assembly. This is generally laborious and can also lead to a risk of electric shock. Typically, the electrical connectors need to be at least partially exposed, thus increasing the risk of electrical shock. On the other hand, no electrical connector operation is required for an inductively coupled lamp. In fact, the secondary coil of the lamp assembly simply need only be placed in proximity to the primary coil to provide power to the lamp assembly. The second eliminates problems with conventional electrical connectors, such as their susceptibility to corrosion and wear, by eliminating the electrical connectors, thereby improving the reliability of the system. These problems are more sensitive to outdoor installations when environmental conditions place the electrical connector in a wet condition. Mechanical linkages are also prone to wear and eventual failure when used repeatedly. Third, the inductive coupled lamp inherently reduces electrical hazards on the lamp assembly. As mentioned above, the lamp assembly is electrically isolated from the power supply. All power must be transferred from the power source to the lamp assembly by induction. The risk of electrical hazards is reduced because the power in the lamp assembly is limited due to the inherent limitations of the power that can be inductively delivered to the lamp assembly.

While inductively coupled lamps offer a number of important advantages over directly connected lamps, they suffer from significant drawbacks. Inductive coupling is inherently less efficient than direct electrical connections. This is due in part to the need for electrical energy to generate and maintain the electromagnetic field. The inefficiency of conventional inductive coupling is mainly caused by the poor tuning circuit. These inefficiencies are evidenced by the increase in noise and heat absorption generated by vibrations in the primary and secondary coils. This efficiency problem becomes severe in high power lamp applications. Furthermore, existing lamp circuits require precise positioning of the primary and secondary coils to provide a reasonable level of efficiency. This requires more precise tolerances and limits the design and construction of the lamp assembly and the overall lamp.

One of the biggest reliability issues faced by the lamp industry is caused by the penetration of wires or other electrical conductors through the lamp sleeve. Typically, the electrical wires are threaded through a glass stem into the interior of the lamp. Since glass is not readily able to adhere and seal the wires, there is a risk of material leakage where the wires pass through the lamp. Despite efforts to optimize sealing, significant reliability issues remain.

There are also reliability issues with conventional inductive power lamps that accompany exposure of the lamp circuit components to the environment, for example, water or moisture from the environment may damage the circuit components. To address this problem, at least one inductively powered lighting system encloses the entire lamp assembly within a sealed sleeve. Hutchisson et al, U.S. patent No. 5,264,997, discloses a lamp mounted on a printed circuit board with a plurality of terminals spaced from a secondary coil. The printed circuit board includes the electronic components required for various inductive coupling operations. The partitioned housing and the lens portion are sealed to each other to form a leak-free enclosure around the lamp, the printed circuit board, and the secondary coil. The housing is particularly configured to receive the secondary coil and to interfit with a socket housing the primary coil. Although the sealed housing provides improved protection from environmental conditions, it is relatively bulky and only provides light that is transmitted in the direction of the lens.

It can thus be seen that there remains a need for an inductively coupled lamp assembly that is efficient, has improved reliability under a variety of conditions, and is easily adaptable to a variety of different lamp configurations.

Disclosure of Invention

The above problems are solved by the present invention in which a lamp, an inductive secondary for powering the lamp, and a capacitor are provided in a lamp assembly. A capacitor is connected in series with the lamp and the secondary coil and has a reactance at the operating frequency that is approximately equal to or slightly less than the combined impedance of the lamp and the secondary coil at the operating temperature. As a result, the lamp circuit operates at or near resonance. For discharge lamps, the series capacitor also acts to limit the current in the secondary circuit, precluding uncontrolled increases in current that would otherwise occur for discharge lamps.

In another aspect, the present invention provides an inductively powered lamp assembly in which the entire lamp assembly circuitry is sealed within a transparent sleeve. Preferably, the entire lamp assembly circuit, including the secondary coil and any associated capacitors, is sealed within the lamp sleeve. In an alternative embodiment, the secondary coil and lamp, as well as any capacitors and starting means, are housed in a second enclosed plastic, teflon, glass or quartz sleeve, and no wires or other components pass through the sleeve. The space between the second sleeve and the lamp sleeve is preferably evacuated or filled with a functional gas to provide a desired level of thermal conduction or insulation.

In another aspect, the present invention provides a remote start switch to provide preheating of the discharge lamp. The switch shorts the electrode on the secondary coil for a certain period of time during lamp starting. In addition, the circuit may also have resistors in series to limit preheating current. In one embodiment the switch is an electromagnetic switch which is preferably activated by an electromagnetic field generated by a corresponding coil in the lamp control circuit.

In another aspect, the present invention provides an inductively powered lamp assembly including an inductive secondary for receiving power from an inductive primary, the inductive secondary having a reactance; a lamp disposed in series with the secondary coil, the lamp having an impedance value substantially equal to the reactance of the secondary coil; and a capacitor arranged in series with the secondary coil and the lamp, the capacitor having a reactance value substantially equal to or slightly less than the impedance of the lamp and the reactance of the secondary coil.

The present invention provides a simple and inexpensive lamp assembly for inductive power lighting. The lamp assembly operates at or near resonance, thus having a high power factor and high efficiency. Energy consumption is reduced by heat build-up and quiet operation of the inductive coupling is provided even in relatively high power applications. The efficiency of the secondary coil does not require precise alignment of the primary coil with the secondary coil, thus allowing the lamp and lamp assembly to have greater freedom in arrangement and construction. The sealing sleeve provides a lamp circuit with improved protection from the environment without limiting the transmission of light from the lamp. Despite having many light sources, the emitted spectrum may be compromised based on the specific transmission of the sleeve material, e.g., some materials are not highly transmissive to ultraviolet light. The present invention allows functional gases to be trapped in the sealed sleeve to increase or decrease the degree of isolation of the lamp from the environment. Furthermore, by enclosing the entire lamp circuit within the lamp sleeve, the need for wires or electrical leads through the sleeve can be eliminated. This improves the reliability of the lamp to a large extent while significantly reducing production losses. At the same time, the electromagnetic switch of the present invention provides a cheap and reliable alternative to conventional start-up circuits.

These and other objects, advantages and features of the present invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

Drawings

FIG. 1 is a cross-sectional view of a lamp assembly according to one embodiment of the invention;

FIG. 2 is a cross-sectional view of the lamp assembly of FIG. 1 perpendicular to the cross-sectional view of FIG. 1;

FIG. 3 is a schematic diagram of a lamp circuit according to one embodiment of the present invention;

FIG. 4 is a cross-sectional view of another alternative lamp assembly having an incandescent lamp;

FIG. 5 is a cross-sectional view of an alternative lamp assembly having an incandescent lamp with a universal base;

FIG. 6 is a cross-sectional view of an alternative lamp assembly having a halogen lamp;

FIG. 7 is a cross-sectional view of an alternative lamp assembly having a halogen lamp with a base outside the lamp sleeve;

FIG. 8 is a cross-sectional view of an alternative lamp assembly having a halogen lamp without a base;

FIG. 9 is a cross-sectional view of an alternative lamp assembly having a fluorescent lamp without an outer sleeve;

FIG. 10 is a cross-sectional view of an alternative lamp assembly having a T-5 or T-8 type fluorescent lamp;

FIG. 11 is a schematic diagram of a lamp circuit for use in the lamp assembly of FIG. 10;

FIG. 12 is a schematic diagram of an alternative lamp circuit for use in the lamp assembly of FIG. 10;

FIG. 13 is a schematic diagram of yet another alternative lamp circuit for use in the lamp assembly of FIG. 10;

FIG. 14 is a schematic diagram of an alternative lamp circuit for use in the lamp assembly of FIG. 10;

FIG. 15 is a cross-sectional view of an alternative lamp assembly having a PL type fluorescent lamp;

FIG. 16 is a cross-sectional view of an alternative lamp assembly having a PL type fluorescent lamp, taken perpendicular to the cross-section shown in FIG. 15;

FIG. 17 is a partial cross-sectional exploded view of an alternative lamp assembly;

FIG. 18 is a cross-sectional view of a portion of the alternative lamp assembly shown in FIG. 16;

FIG. 19 is a cross-sectional view of a portion of another alternative lamp assembly; and

FIG. 20 is a cross-sectional view of a portion of yet another alternative lamp assembly.

Detailed Description

A lamp assembly according to one embodiment of the present invention is shown in fig. 1 and 2 and is generally designated 10. For purposes of this disclosure, the invention will first be described in connection with a conventional PL-S type 11 watt Ultraviolet (UV) lamp adapted for use under 38 watt conditions, for example, in a water treatment device. The lamp assembly 10 generally includes a lamp circuit 12 and an outer sleeve 70. The lamp circuit 12 includes a secondary coil 14, a capacitor 16 and a lamp 18, all connected in series (see fig. 3). The secondary coil 14 inductively receives power from a primary coil (not shown) of an associated ballast (not shown). The series capacitor 16 is specifically tuned, as will be described in detail later, to cause the lamp circuit to operate at resonance under specific operating conditions. The entire lamp circuit 12 is completely enclosed within the outer sleeve 70, including the secondary coil 14, the capacitor 16, and the lamp 18. At least a portion of the outer sleeve 70 is transparent and no wires or other elements pass through.

Although the following embodiments are described in connection with a PL-S type 38 watt ultraviolet lamp, the present invention is intended or adapted for use with various types or styles of lamps, including discharge lamps, incandescent lamps, pulsed white light lamps, and light emitting diode ("LED") lamps. The present disclosure provides various other alternative embodiments of display incandescent and discharge lamps. These examples are intended to illustrate the broad application and applicability of the present invention and are not intended to limit the scope of the claims.

A variety of ballasts for starting the inductively powered lamp assembly of the present invention are known to those skilled in the art. Therefore, the ballast will not be described in detail. A ballast particularly suitable for use with the PL-S type 38W ultraviolet lamp in the illustrative embodiment is disclosed in U.S. patent application No.90/592194 entitled "fluid handling System" filed on 12.6.2000, which is hereby incorporated by reference in its entirety. The ballast is adapted to provide efficient operation for all embodiments disclosed herein.

I.Lamp structure

As mentioned above, the PL-S type 38W ultraviolet lamp preferably comprises an outer sleeve 70 for enclosing the lamp circuit 12 to protect it from the environment (see fig. 1 and 2). The outer sleeve 70 preferably includes a body 90 and a cap 92. The body 90 is generally a cylindrical tube having an open end and a closed end. After the lamp circuit 12 is mounted into the body 90, the cover 92 is sealed over the open end of the body 90 to completely enclose the lamp circuit 12. The lamp circuit 12 generally includes a secondary coil 14, a capacitor 16, and a lamp 18. As described below, the lamp circuit 12 may also include an initiator 35 (see fig. 2). Lamp 18 is a generally conventional PL-S type lamp having a quartz sleeve with two parallel legs 72a-b interconnected to define chamber 28. The chamber 28 is partially evacuated and contains the desired discharge gas, such as mercury vapor. Socket 32a-b is disposed at the bottom of each leg 72 a-b. A pair of common or custom designed electrodes 26a-b are disposed within the chamber 28, one mounted on top of each header 32 a-b. In this embodiment, the outer sleeve 70 is preferably made of quartz to transmit ultraviolet light efficiently. In non-ultraviolet applications, the outer sleeve may be made of glass, Teflon, or plastic, depending in part on the heat generated by the lamp and the operating environment of the lamp. For example, another alternative outer sleeve is made from a length of Teflon tubing having sealed opposite ends (not shown). The teflon tube can be fitted over the remainder of the lamp assembly and its opposite end can be rolled up or sealed to enclose the teflon sleeve. Preferably, each end of the teflon tubing is folded back upon itself and crimped using heat and pressure.

The lamp assembly 10 also includes a base 50 and a strip 86 to retain the opposite end of the lamp 18 within the outer sleeve. The base 50 is generally cylindrical and is sized to fit snugly within the outer sleeve 70. In addition to holding one end of the lamp 18, the base 50 also houses various electronic components of the lamp circuit 12. Base 50 defines a circular recess 80 to receive the windings of secondary coil 14, a pair of slots 82a-b to receive the bottom end of each leg 72a-b, and a pair of apertures 84a-b to receive capacitor 16 and any desired actuator 35. The lamp assembly 10 may also include a heat reflector 58 disposed between the secondary coil and the electrodes 36 a-b. The shape of the heat reflector 58 preferably matches the shape of the end face of the lamp sleeve 52 in its installed position and is preferably made of a commonly used reflective material, such as aluminum or aluminum foil on a suitable substrate. The fulcrum 86 is generally disc-shaped and sized to fit snugly within the outer sleeve 70. The fulcrum 86 preferably includes a projection 88 to frictionally fit between the legs 72a-b of the quartz sleeve 52. The exact design and configuration of the base 50 and the support plate 86 will vary from application to application depending upon the design and configuration of the outer sleeve 70 and the various components of the lamp circuit 12. The base 50 and the support 86 are preferably made of a material that can withstand high temperatures, such as ceramic or high temperature plastic.

In one embodiment, the gap 96 between the outer sleeve 70 and the lamp sleeve 52 is configured to provide a lamp assembly with a desired electrical conductivity or insulation. For example, void 96 may be evacuated to insulate the lamp from a cold environment. Alternatively, the void 96 is filled with a heavier gas, such as argon and neon, or a fluid to conduct heat in a hot environment. Conducting heat from the lamp in a hot environment will help protect the lamp from overheating and help provide maximum intensity.

In most applications, the lamp assembly 10 may also include a mechanism that allows the ballast to sense the presence of the lamp assembly 10. This allows the ballast to start the primary coil (not shown) only when the lamp assembly 10 is installed. While the induction mechanism is not necessary in many applications, particularly in low power applications, it does provide a more efficient design to conserve energy, reduce heat generation, and protect the primary coil from some type of damage that accompanies continued operation. In one embodiment, the lamp assembly 10 includes an induction magnet 60 and a ballast (not shown), or associated control circuitry, including a reed switch (not shown) that is actuated by the induction magnet 60. More specifically, the induction magnet 60 is disposed proximate to a reed switch (not shown) when the lamp assembly 10 is installed. The magnetic field from the induction magnet 60 causes the reed switch 62 to close, thereby providing a signal to the ballast or control circuit that the lamp assembly 10 is in place. The induction magnet is preferably mounted on the base 50, but may be mounted in other desired locations. Alternatively, the sensing magnet 60 and reed switch (not shown) may be replaced by a mechanical switch (not shown). For example, the switch may be placed in a position that is mechanically closed by installation of the lamp assembly 10. Another option is to provide the lamp with an on/off switch for manual starting, such as a toggle switch that selectively turns the ballast on and off.

II.Lamp circuit

The lamp circuit 12 will now be described in connection with the above-described PL-S type 38W ultraviolet lamp (see fig. 1 and 2). As described above, the lamp circuit 12 generally includes the lamp 18, the secondary coil 14, and the capacitor 16. A schematic diagram of the lamp circuit 12 is shown in fig. 3. In this embodiment the lamp circuit comprises a single secondary coil 14, preferably constituted by a coil of small diameter wire 22. The precise characteristics of the secondary coil 14 will vary from application to application as a function of the primary coil (not shown) and the load, such as a lamp. The wire 22 is preferably a conventional magnet wire or LITZ wire (LITZ), depending on power settings and heat dissipation. The wire is preferably wound around the base 50 within the annular groove 80, which provides the secondary coil 14 with a hollow core. The hollow core 24 may be replaced with other conventional cores if desired. The type of wire, the number of turns of wire, and the diameter of the core (and thus the diameter of the turns of wire) will vary from application to application depending on various factors such as the primary coil and the load characteristics of the lamp 18. The inductance of the secondary coil 14 is selected as a function of the operating frequency and the impedance of the load (i.e., the lamp) at the supplied power. More specifically, the inductance of the secondary coil 14 is determined by:

in the 38 watt embodiment, the secondary coil 14 is configured to receive power from a primary coil operating at a frequency of approximately 100 kilohertz. The secondary coil 14 includes 72 turns of wire and the primary coil includes 135 turns of wire. In the 38 watt embodiment described, the secondary winding 14 has an inductance value of 196 microhenries at a frequency of 100 kilohertz with a reactance value of about 123 ohms. The secondary coil 14 is preferably disposed in the base 50 of the lamp assembly 10. The diameter of the secondary coil is selected to fit closely within the base 50. The secondary coil 14 is electrically connected to the lamp 18 by leads 51 a-b. Although the secondary coil is preferably circular, it may also vary from application to application. For example, the secondary coil may be square, oval, triangular, trapezoidal, hexagonal, or even spherical. The secondary coil is preferably disposed externally or internally concentric with the primary coil, or the two coils may be disposed end-to-end.

The capacitor 16 is selected to provide optimum power factor correction taking into account mechanical constraints, thereby providing resonance in the lamp circuit. The power factor is preferably.90 or greater, and more preferably.96 or greater, although lower values may be acceptable in some applications. Without sufficient power factor correction, the reactive current in the secondary coil will be reflected back into the primary coil, becoming a lower impedance load. This will result in an upward drift under operating power and current conditions, and higher losses in the form of heat increments in the primary circuit. This effect is contrary to the initial expectation, but it does occur due to the opposite nature of the reflected impedance of the series resonant primary circuit. Experiments have revealed that at factors below.90, the reactive current and losses in the primary coil increase very rapidly. This may have materials that have a detrimental effect on efficiency, especially when these losses are added to the losses caused by the coupling factor and dc impedance. In general, capacitor 16 is selected to have a resistance impedance approximately equal to or slightly less than the resistance impedance of lamp 18 at its operating temperature and the reactance impedance of secondary 14. Similar to the inductance of the secondary winding 14, the reactance of the capacitor is selected as a function of the operating frequency and the load (i.e., lamp) impedance at a given power. More specifically, the reactance of the capacitor is selected according to:

at this reactance value, the capacitor 16, secondary 14 and lamp 18 will operate at near resonant conditions, providing a high power factor and thus high efficiency. In the illustrative embodiment, the capacitor 16 is approximately 12.9 nanofarads (nf). This value will change in response to changes in the primary coil (not shown), the secondary coil 14, and/or the lamp 18.

The secondary and capacitor equations described above give roughly the required capacitance and secondary reactance values. To obtain more accurate values (and thus fine tuning of power factor, current limiting effect and overall operating parameters), a loop test procedure may be used. This loop test is required in some applications to obtain the level of efficiency in the desired secondary circuit. The operating parameters of these designs include preheat, trigger voltage, and operating current. All of these parameters can be configured by the tuning process as a function of ratio, capacitance and inductance.

Although the capacitor 16 is preferably tuned to the secondary coil 14 and the lamp 18 when the lamp 18 is at operating temperature, the capacitor 16 may be tuned at other times to provide optimum efficiency. For example, in a discharge lamp that requires a large current to start the lamp, the present invention may be used for a gain circuit at start-up. In such applications, the capacitor is selected to have a reactance that is approximately equal to the combined impedance of the secondary and the lamp at start-up temperature (rather than operating temperature). This will increase the efficiency of the lamp circuit during start-up, allowing the use of ballasts with lower current maximum values.

Depending on the nature of the plasma, the discharge lamp tries to maintain the voltage at a substantially constant intrinsic voltage value. As a result, the lamp will consume too much power when the secondary coil 14 produces a voltage that exceeds the lamp's natural voltage. Since the impedance of the discharge lamp decreases in response to the current, the lamp voltage generates an increasingly larger current up to the circuit limit or self-destruction. The above problem is solved by a capacitor 16, the function of which is to limit the current supplied to the lamp. The current limiting function is an inherent characteristic of the capacitor. It has been determined that the capacitance value that places the secondary coil at resonance is approximately equal to the capacitance value that provides the proper current limit. Accordingly, it has been determined that the current limiting function is achieved in the present invention by selecting the capacitance value to provide a suitable overall power factor.

When the present invention is incorporated into a discharge lamp assembly, the lamp circuit 12 preferably includes a conventional starter 35 (see fig. 2), glow bulb or other equivalent device. Starter and glow bulbs are well known and will not be described in detail in this application. In one embodiment of the discharge lamp assembly, the usual starter is replaced by a remote start switch, such as an electromagnetic switch 34 (see fig. 3). The electromagnetic switch 34 is coupled in series between the electrodes 36a-b, thereby selectively allowing the switch 34 to close the circuit between the electrodes 36 a-b. When closed, the switch 34 allows current to flow directly through the electrodes 36a-b, rather than breaking down the gas by requiring an arc. As a result, when switch 34 is closed, electrodes 36a-b are rapidly heated. The electromagnetic switch 34 is preferably arranged substantially perpendicular to the direction of the electromagnetic field of the primary coil so that the electromagnetic switch 34 is not activated by the electromagnetic field of the primary coil. Instead, a separate coil 38 is provided adjacent the electromagnetic switch 34 where it can be charged to selectively close the switch 34. The microprocessor 40 preferably controls the operation of the coil 38 and thus the electromagnetic switch. The microprocessor 40 is programmed to charge the coil 38 for a fixed time interval each time the lamp circuit is energized. This closes the electromagnetic switch while shorting the electrodes 36 a-b. Alternatively, the microprocessor 40 may be replaced by a conventional one-shot timer circuit (not shown) configured to charge the coil for the required time each time the lamp is started.

III.Other alternative embodiments

The configuration of the lamp assembly may vary significantly from application to application, generally depending on the type of lamp and the associated power requirements. The invention can be modified to allow use in a wider variety of existing lighting systems. The following alternative embodiments describe a variety of alternative embodiments suitable for various uses. These alternative embodiments are intended to illustrate the broad applicability of the invention and are not exhaustive.

Fig. 4 shows another alternative embodiment of the invention applied to an incandescent lamp. In this embodiment, the lamp assembly 110 includes a glass sleeve 152 and a plastic base 150. The glass sleeve 152 is generally bulb-shaped and includes an inwardly bent and generally cylindrical stem 132. The secondary coil 114 is mounted within a glass sleeve 152 around the stem 132. Filament 136 is mounted on the secondary coil in a conventional manner extending up to the bulb of glass sleeve 152. Unlike the above-described embodiments, the susceptor 150 in this embodiment is fitted to the outside of the glass sleeve 152. The base is configured to be secured to a corresponding socket (not shown). The illustrated base 150 is generally circular and includes an annular recess 156 configured to snap fit into a corresponding socket (not shown). The base 150 also includes an upper flange 158 to provide a gripping edge for removing the lamp assembly 110 from a socket (not shown). However, the base 150 may have a variety of different configurations to allow the lamp assembly to be mechanically coupled to a variety of different sockets. For example, the base may be externally threaded. As shown, the lamp assembly 110 preferably includes an induction magnet 160. The induction magnet 160 may be fitted to a corresponding retaining wall 162 on the bottom surface of the base 150. As described above, the induction magnet 160 cooperates with the magnetically actuated switch to alert the primary coil or control circuit lamp assembly 110 of the presence. This allows the primary coil to be energized only when the lamp assembly 110 is in place. As shown in fig. 5, the incandescent lamp assembly 110' may be configured to work with a conventional universal base. In this embodiment, the base 150' includes a pair of mounting prongs 156a-b that may interlock with mating slots in a conventional universal base lamp socket (not shown).

Fig. 6 shows another alternative embodiment of the invention applied in a halogen lamp. In this embodiment, the lamp assembly 210 generally includes a quartz sleeve 252 and a ceramic pedestal 250. The materials of the sleeve 252 and the base 250 are selected to withstand the particularly high temperatures at which halogen lamps operate. The quartz sleeve 252 is preferably completely sealed and does not include any through components, such as wires or other electrical connectors. The filament 236, secondary coil 214, and capacitor 216 are enclosed within a quartz sleeve 252. In some applications, capacitor 216 is not necessary to provide an acceptable level of efficiency and therefore may be eliminated accordingly. The lamp assembly 210 further includes a heat reflector 258 disposed between the filament 236 and the secondary coil 214. The base 250 may include quarter turn threads 256a-b that threadably mate with one another in a corresponding socket (not shown). The base 250 may have an alternative configuration to facilitate mounting on a socket. The induction magnet 260 is preferably mounted to the inner bottom surface of the base 250.

In an alternative halogen lamp assembly 210 ', the quartz sleeve 252 ' is shortened to terminate just inside the neck of the pedestal 250 ' (see fig. 7). The secondary coil 214 ' is moved outside the quartz sleeve 252 ' and is disposed in the susceptor 250 '. In this embodiment, the secondary coil 214 'is thermally insulated from the filament 236'. This embodiment may also include an induction magnet 260'.

In another alternative halogen lamp assembly 210 ", the pedestal is omitted and the induction magnet 260" is moved into the interior of the sealed quartz sleeve 252 ". As shown in fig. 8, the quartz sleeve 252 "defines an annular recess 256" extending completely around the sleeve 252 "such that the lamp assembly 210" can be snap-fitted into a corresponding socket (not shown).

Another alternative embodiment is shown in fig. 9. In this embodiment, the lamp assembly 310 includes a base 350 disposed outside of a lamp sleeve 352, and the lamp assembly 310 does not include an outer sleeve. A lamp sleeve 352 encloses the electrodes 336a-b and the desired discharge gas, such as mercury vapor. The secondary coil 314, capacitor 316, any required activation mechanism (such as a conventional activator or a magnetically activated switch as described above), and all electrical connectors are housed within the base 350, but outside of the lamp sleeve 352. The base 350 is configured to correspond to a conventional universal base and includes a pair of mounting prongs 356a-b that may interlock with mating slots in a lamp socket (not shown). The base 350 may alternatively be configured to mate with other receptacle structures. The induction magnet 360 is preferably mounted in the base 350. The lamp assembly 310 may also be augmented with an outer sleeve (not shown) to increase its protection from the environment, if desired. If an outer sleeve is included, the outer sleeve preferably extends around the entire lamp assembly except for the base 350. The base 350 is mounted on the outside of the outer sleeve so that it can be interfitted with a lamp socket.

Fig. 10 and 11 show another alternative embodiment of the invention applied to a fluorescent lamp of the T5 or T8 type. Lamp assembly 410 includes an elongated glass sleeve 452 and a pair of secondary coils 414a-b, each located at one end of sleeve 452. Since the two secondary coils 414a-b are in different physical locations, the power supply is preferably configured to include two separate primary coils (not shown) to provide power to the two secondary coils 414a-b, respectively. Two primary coils are disposed adjacent to respective secondary coils. The power is typically distributed evenly among the coils 414a-b, but is not strictly necessary. Preferably, the secondary coils 414a-b are provided with opposite polarities, and each primary coil and secondary coil are configured in combination to maintain the half voltage and current required to power the lamp. Sleeve 452 preferably includes an annular stem 432a-b formed at each opposite end to receive secondary windings 414 a-b. Electrodes 436a-b are electrically coupled to each of secondary coils 414 a-b. A capacitor 416 is connected in series between the two secondary windings 414 a-b. A preferred method of calculating the values of the capacitors 416a-b in this embodiment is to perform an initial analysis of the circuit according to the method described above (in connection with the first disclosed embodiment) assuming that only one coil is used. The single capacitance value in this hypothetical case is then halved as the capacitance value for each of the two capacitors 416a-b in this embodiment. Optional end caps 420a-b, preferably made of aluminum, are fitted over opposite ends of sleeve 452. The light assembly 410 may include a conventional actuator 435, as shown in fig. 11. In this embodiment, conductors 498a-b need to be provided between the two secondary coils 414 a-b. Conductors 498a-b are preferably contained within lamp sleeve 452. Alternatively, magnetic switches 434a-b, or other remotely actuated switches, may replace the conventional actuator. As shown in fig. 12, lamp assembly 410 ' includes a separate switch 434a-b mounted in series between each secondary coil 414a-b ' and its corresponding filament or electrode 436a-b '. By closing the switches 434a-b, power from each secondary coil 414 a-b' is provided directly to the corresponding filament. In this embodiment, there is only one conductor 498 'between the secondary coils 414 a-b'. Capacitors 416 'are connected in series along conductor 498'.

Fig. 13 shows another alternative circuit for a dual coil lamp assembly 410 ". In this circuit, no conductors are required between the two secondary coils 414a-b ". Instead, each secondary winding 414a-b "includes a dedicated switch 434 a-b" and a dedicated capacitor 416a-b ". The lamp controller is preferably configured to cause both switches 434a-b "to be turned on and off simultaneously. The optimal way to calculate the capacitance values of the capacitors 416a-b "is to perform an initial analysis of the circuit according to the method disclosed in the first embodiment, assuming that only one secondary coil is used. The capacitance value of a single capacitor of this hypothetical configuration is then halved as the capacitance value of each of the two capacitors 416a-b "of the present embodiment. In some applications, the electrical energy is not evenly distributed between the two secondary coils. In such an embodiment, the ratio between the capacitance values of the two capacitors should be comparable to the power ratio between the two secondary coils.

Fig. 14 shows another alternative circuit for a dual coil lamp 410' ". In this embodiment, only one secondary coil 414' "is provided. The secondary coil 414 '"is connected to electrodes 436 a-b'" at opposite ends of the lamp. The circuit includes a pair of conductors 498 a-b' "extending between the coils. A conventional actuator 435' "or other actuating mechanism, such as a magnetic switch, is provided to actuate the lamp. In this embodiment, the capacitance value of the capacitor 416' "is preferably selected according to the method of the first disclosed embodiment.

Another alternative embodiment of the invention for use in a PL type fluorescent lamp is shown in fig. 15 and 16. In this embodiment, the entire lamp circuit is enclosed in the lamp sleeve 552 and does not include an outer sleeve. As shown, the lamp assembly 510 includes a lamp sleeve 552 having two interconnected legs 502 a-b. The lamp assembly 510 may include a dual coil lamp circuit of any of the types described above. For illustrative purposes, this embodiment is described in connection with a lamp assembly 510 having a separate secondary coil 514a-b mounted on the base of each leg 502 a-b. The two secondary coils 514a-b are preferably powered by one primary coil that surrounds or is adjacent to one end of the lamp assembly 510. Each secondary coil 514a-b is connected in series with an electrode 536a-b, a capacitor 516a-b and a magnetic start switch 534 a-b. As described above, the embodiment described in connection with embodiment 13 selects the capacitance value of each capacitor 516 a-b. The lamp assembly 510 may also include an induction magnet 560.

An alternative lamp assembly 610 having an alternative sealing structure is shown in fig. 17 and 18. As shown in exploded view in fig. 17, lamp assembly 610 generally includes a locking ring 602, an outer sleeve 670, a lamp 618, and a base 650. Locking ring 602, outer sleeve 670, and base 650 cooperate to seal lamp assembly 610. As will be more apparent from fig. 18, the base 650 includes a cylindrical central portion 652 for housing the secondary coil 614 and the lamp 618. More specifically, the lamp 618 is mounted on a printed circuit board assembly ("PCBA") 654, which preferably supports any capacitors or actuating mechanisms in the lamp assembly 610. The lamp/PCBA assembly is mounted on the base 650, for example, by way of a fixed part or snap fit. The base 650 may also include an annular groove 656 surrounding the base 650 for receiving an end of the outer sleeve 670. An O-ring 604 fits in the annular groove 656 around the central portion 652. The base 650 may include an annular rib (not shown) to prevent the O-ring 604 from riding up the center portion 652. Once installed, the O-ring 604 is disposed between the inner diameter of the outer sleeve 670 and the outer diameter of the central portion 652 of the base 650. In this position, O-ring 604 not only provides an effective waterproof seal, but also acts as a shock damper to dampen shock between the lamp and outer sleeve 670. The outer sleeve 670 is a generally cylindrical tube having a closed end and an open end. A bead 672 or other flange is provided around the open end of outer sleeve 670. The outer sleeve 670 is fixedly mounted to the base 650 by the locking ring 602. Locking ring 602 is generally annular and fits over outer sleeve 670 and base 650. The locking ring 602 has a generally inverted L-shaped cross-section with a radial leg 674 and an axial leg 676. The radial leg 674 engages the bead 672 and the axial leg 676 engages the outer surface of the base 650. Alternatively, as shown in FIG. 19, the locking ring 602 'and base 650' may also be configured such that the axial legs 676 'may fit into the annular groove 656'. In both embodiments, the axial leg 676 or 676 'is secured to the base 650 or 650' to lock the outer sleeve 670 in the annular groove 656 of the base 650. The locking ring 602 may be attached to the base 650 with various connections. For example, the locking ring 602 may be attached to the base 650 by sonic or thermal welding. Alternatively, the lamp assembly 610 "may include a locking ring 602" of the lower flange 678 (see fig. 20) such that the locking ring 602 'is snap-fit onto the base 650', or threads (not shown) may be provided on the locking ring and the base such that the locking ring is threadably secured to the base.

What has been described above is a number of embodiments of the present invention. Various modifications and changes may be made without departing from the spirit and scope defined in the appended claims, which are to be interpreted in accordance with the doctrine of equivalents. Any reference to claim elements in the singular, for example, with the articles "a," "an," "the," and "said," is not to be construed as limiting the element to the singular.

Claims (21)

1. An inductively powered lamp assembly comprising:

an inductive secondary coil for receiving power from the inductive primary coil, the inductive secondary coil having a secondary impedance;

a lamp disposed in series with the secondary coil, the lamp having a lamp sleeve and a lamp impedance; and

a capacitor disposed in series with said inductive secondary and said lamp, said capacitor selected to have a reactance at starting temperature equal to the sum of said lamp impedance and said secondary impedance, whereby said capacitor, said lamp and said secondary operate at resonant conditions during starting.

2. The lamp assembly as set forth in claim 1, wherein the secondary coil is further defined as a litz wire coil.

3. The lamp assembly of claim 2, wherein the secondary coil is further defined as a magnet wire coil.

4. The lamp assembly of claim 1, wherein the lamp sleeve is substantially transparent to light of a desired wavelength.

5. The lamp assembly of claim 1, wherein the lamp sleeve is substantially transparent.

6. The lamp assembly as set forth in claim 1, wherein the lamp is further defined as an incandescent lamp.

7. The lamp assembly of claim 1, wherein the lamp is further defined as a discharge lamp.

8. The lamp assembly of claim 1, wherein the secondary coil is coaxial with the lamp.

9. An inductively powered lamp assembly comprising:

an inductive secondary coil for receiving power from the inductive primary coil, the inductive secondary coil having an impedance;

a lamp disposed in series with the secondary coil, an impedance of the lamp having a magnitude equal to a magnitude of the impedance of the secondary coil; and

a capacitor disposed in series with said secondary coil and said lamp, said capacitor having a reactance at starting temperature equal to the sum of said impedance of said lamp and said impedance of said secondary coil, whereby said capacitor, said lamp and said secondary coil operate at resonant conditions during starting.

10. The lamp assembly as set forth in claim 9, wherein the secondary coil is further defined as a litz wire coil.

11. The lamp assembly of claim 10, wherein the secondary coil is further defined as a magnet wire coil.

12. The lamp assembly of claim 9, wherein the lamp assembly comprises an enclosed transparent sleeve surrounding and completely enclosing the secondary coil, the capacitor, and the lamp, the sleeve not being penetrated.

13. The lamp assembly as set forth in claim 9, wherein the lamp is further defined as an incandescent lamp.

14. The lamp assembly as set forth in claim 9, wherein the lamp is further defined as a discharge lamp.

15. The lamp assembly of claim 9, wherein the secondary coil is coaxial with the lamp.

16. A method of manufacturing a lamp assembly comprising the steps of:

connecting a lamp with an inductive secondary coil, the lamp having a lamp sleeve and an impedance, the secondary coil having an impedance;

connecting a capacitor in series with said lamp and said inductive secondary, said capacitor being selected to have a reactance at starting temperature equal to the sum of said lamp impedance and the impedance of said secondary, whereby said capacitor, said lamp and said secondary operate at resonance conditions during starting.

17. The method of claim 16, wherein the lamp connecting step comprises the steps of:

a first lead connecting a first end of the filament wire to the inductive secondary coil;

a first lead connecting a second end of the filament wire to the capacitor; and

connecting a second lead of the capacitor to a second lead of the inductive secondary.

18. The method of claim 16, wherein the lamp connecting step comprises the steps of:

a first lead connecting a first lamp electrode to the inductive secondary coil;

a first lead connecting a second lamp electrode to the capacitor; and

connecting a second lead of the capacitor to a second lead of the inductive secondary.

19. The lamp assembly of claim 12, wherein the sleeve is a substantially flat plastic tube, opposite ends of the tube being sealed to provide a completely sealed closure.

20. The lamp assembly of claim 19, wherein the opposite end of the tube is crimped.

21. A lamp assembly as set forth in claim 20, wherein the plastic tube is further defined as a polytetrafluoroethylene tube.