Low watt metal halide lamp

A metal halide arc discharge lamp having a power input rating of not more than 35 watts, said lamp comprising:

• an envelope of light transmissive material including a bulb portion, a pair of transitional neck portions extending from said bulb portion, and a pair of stem portions extending from said transitional neck portions respectively,
• said bulb portion of said envelope defining an arc chamber therein and having an external surface area of such value as to produce a wall loading not exceeding about 35 watts /cm.sup.2 ;
• a fill of mercury, inert gas and metal halide contained within said arch chamber, said mercury and said metal halide being adapted to substantially vaporize during operation of said lamp;
• a pair of electrodes, extending into said arc chamber from said pair of neck portions respectively, and having electrode tips spaced apart from one another by a distance A within said arc chamber to produce an arc loading value that is greater than 150 watts/cm,
• said neck portions of said envelope each having a wall surrounding a segment of said electrodes respectively, the walls of said neck portions each having a stretched section with a minimum wall thickness not exceeding about 1.5 millimeters;
• a pair of inlead assemblies electrically coupled to said pair of electrodes respectively and passing from said electrodes through a sealed section in said stem portions to the exterior of said lamp;
• said lamp having a power input of about 11 to 35 watts and wherein the insertion depth of said electrodes is greater than 1.5 mm.

A metal halide arc discharge lamp comprising:

• an envelope of light transmissive material including a bulb portion, a pair of transitional neck portions extending from said bulb portion, and a pair of stem portions extending from said transitional neck portions respectively;
• said bulb portion of said envelope defining an arc chamber therein and having an external surface area of such value as to produce a wall loading not exceeding about 35 watts /cm.sup.2 ;
• a fill of mercury, inert gas and metal halide contained within said arc chamber, said mercury and said metal halide being adapted to substantially vaporize during operation of said lamp;
• a pair of electrodes, extending into said arc chamber from said pair of neck portions respectively, and having electrode tips spaced apart from one another by a distance A within said arc chamber,
• said neck portions of said envelope each having a wall surrounding a segment of said electrodes respectively, the walls of said neck portions each having a stretched section with a minimum wall thickness not exceeding about 1.5 millimeters;
• a pair of inlead assemblies electrically coupled to said pair of electrodes respectively and passing from said electrodes through a sealed section in said stem portions to the exterior of said lamp;
• and
• said lamp having a power input of about 12 watts and said distance A between said electrode tips is in a range of about 0.5 to 0.8 mm to produce an arc loading having a value greater than 150 watts/cm.

A metal halide arc discharge lamp comprising:

• an envelope of light transmissive material including a bulb portion, a pair of transitional neck portions extending from said bulb portion, and a pair of stem portions extending from said transitional neck portions respectively,
• said bulb portion of said envelope defining an arc chamber therein and having an external surface area of such value as to produce a wall loading not exceeding about 35 watts /cm.sup.2 ;
• a fill of mercury, inert gas and metal halide contained within said arc chamber, said mercury and said metal halide being adapted to substantially vaporize during operation of said lamp;
• a pair of electrodes, extending into said arc chamber from said pair of neck portions respectively, and having electrode tips spaced apart from one another by a distance A within said arc chamber,
• said neck portions of said envelope each having a wall surrounding a segment of said electrodes respectively, the walls of said neck portions each having a stretched section with a minimum wall thickness not exceeding about 1.5 millimeters;
• a pair of inlead assemblies electrically coupled to said pair of electrodes respectively and passing from said electrodes through a sealed section in said stem portions to the exterior of said lamp;
• said lamp having a power input rating in the range of between about 18 watts to 22 watts and wherein the distance A between said electrode tips is between about 1.0 to 1.2 mm to produce an arc loading that is greater than 150 watts/cm.

A metal halide arc discharge lamp having a power input rating of not more than 35 watts, said lamp comprising:

• an envelope of light transmissive material including a bulb portion, a pair of transitional neck portions extending from said bulb portion, and a pair of stem portions extending from said transitional neck portions respectively, said bulb portion of said envelope having a wall defining an arc chamber therein, said wall having an external surface area of such value as to produce a wall loading not exceeding about 35 watts/cm.sup.2, said arc chamber having a length W defined between said neck portions of said envelope;
• a fill of mercury, inert gas and metal halide contained within said arc chamber, said mercury and said metal halide being adapted to substantially vaporize during operation of said lamp;
• a pair of electrodes, extending into said arc chamber from said pair of neck portions respectively, and having electrode tips spaced apart from one another by a distance A within said arc chamber to produce an arc loading value that is greater than 150 watts/cm, said electrodes having an insertion factor Y, corresponding to the formula Y=(W-A)/W, with a value greater than about 0.6,
• the wall of said bulb portion having a substantially uniform thickness not exceeding about 0.5 mm over a centrally disposed segment defined between two imaginary parallel planes located at the electrode tips respectively,
• said neck portions of said envelope each having a wall surrounding a segment of said electrodes respectively;
• said lamp having a power input rating in a range of between 1.5 watts and 35 watts and the wall thickness of the neck portions having a reduced section in the range of about between 0.3 and 1.5 mm;
• said arc chamber having a shape selected form the group of shapes consisting essentially of ellipsoids and spheroids and approximations thereof;
• and
• a pair of inlead assemblies electrically coupled to said pair of electrodes respectively and passing from said electrodes through a hermetically sealed section in said stem portions to the exterior of said lamp.