Electrodeless discharge lamp and power coupler therefor

• US 3,873,884 A
• Filed: 02/11/1974
• Issued: 03/25/1975
• Est. Priority Date: 03/01/1973
• Status: Expired due to Term

• Current Assignee: Fred C. Gabriel
• Original Assignee: Fred C. Gabriel
• Inventors: Gabriel, Fred C.
• Primary Examiner(s): Mullins, James B.
• Application Number:
  US05/441,600
• Time in Patent Office: 407 Days
• Field of Search: 315/248,267,344,348 313/161
• US Class Current: 315/267
• CPC Class Codes: H01J 65/048 the field being produced by using an excitation coil

Abstract

An electrodeless discharge lamp, consisting of a transparent envelope containing an ionizing gas and a minor amount of metallic element for producing spectral light, is started and operated by r-f power coupled to the lamp by a resonant coupler that consists of a helically coiled wire conductor mounted concentrically within a grounded hollow cylinder which is open at one end with a grounded base member in the other end.

Claims

1. A resonator coupler for coupling a source of r-f electric power into an electrodeless discharge lamp for starting and operating the lamp, comprising:

a grounded hollow cylinder of electrically conductive material open at one end, with a grounded base member at the other end;

a helically coiled wire conductor concentrically within the cylinder and spaced from the inner walls thereof;

means for mounting a discharge lamp substantially concentrically within one end position of the coil;

the wire of the coil being one quarter wave long relative to the free-space wavelength of r-f power intended to be applied for operating a lamp mounted therein;

the end of the coil at the end portion within which a lamp is adapted to be mounted being toward said base member and being grounded, the other end of the coil being open circuited; and

electrical connecting means for connecting to the coil a source of r-f electrical power that is sufficient to maintain a discharge in a lamp mounted within the coil, said connecting means being tapped into the coil at a point near, but spaced from, the grounded end thereof, said point being selected such that, when a lamp mounted in the coil is in operation by r-f power connected to the coil, the coupler is tuned to the frequency of said r-f power and the impedance of said lamp and coupling means at said tap point substantially matches the impedance of said r-f power source, whereby when said r-f power is applied to the coil, and before a discharge is ignited in the lamp, a voltage maximum occurs at the open circuited end of the coil and creates a potential extending through the lamp portion between said open circuited end and said base member for ionizing the gas in the lamp.

2. The coupler of claim 1 including a capacitor between the wall of said cylinder and a turn of said coil for fine tuning the resonant frequency of the resonator coupler relative to the frequency of an r-f source to be applied thereto.

3. The resonator of claim 1 in which the outside diameter of the coil is substantially one-half the inside diameter of the cylinder, the coil being of silver wire and the interior of the cylinder being polished silver plating.

4. The resonator of claim 1 which the open end of the cylinder extends beyond the open circuited end of the coil at least sufficiently to avoid fringe effects.

5. The resonator of claim 1 in which said base member extends across and substantially closes an end of the cylinder, the outside diameter of the coil and inside diameter of the cylinder being substantially 1 inch and 2 inches respectively, the wire of said coil being silver, and the interior walls of the cylinder and base member being polished silver plating.

6. The combination of an electrodeless discharge lamp and a resonator coupler for coupling the lamp to a source of r-f electric power for starting and operating the lamp, said coupler comprising:

a grounded hollow cylinder of electrically conductive material open at one end with a grounded base member at the other end;

a helically coiled wire conductor concentrically within the cylinder and spaced from the inner walls thereof, said wire being one quarter wave long relative to the free-space wavelength of r-f power intended to be applied for operating the lamp, the end of the wire coil at the base member end of the cylinder being grounded and the end toward the open end of the cylinder being open circuited, and the lamp being mounted with at leaSt the major portion of the lamp within the coil at the grounded end of the coil; and

electrical connecting means for connecting to the coil a source of r-f electrical power that is sufficient to maintain a discharge in the lamp, said connecting means being tapped into the coil at a point near, but spaced from, the grounded end thereof, said point being selected such that, when the lamp is in operation by r-f power connected to the coil, the coupler is tuned to the frequency of said r-f power and the impedance of the lamp and coupler means at said tap point substantially matches the impedance of said r-f power source, whereby when said r-f power is applied to the coil, and before a discharge is ignited in the lamp, a voltage maximum occurs at the open circuited end of the coil and creates a potential extending through the lamp portion between said open circuited end and said base member for ionizing the gas in the lamp.

7. The combination of claim 6 in which said discharge lamp is a transparent sealed envelope containing an ionizing gas at low pressure and a minor amount of a metallic element for producing spectral light of said metallic element.

8. The combination of an electrodeless discharge lamp for providing spectral light and resonator coupler for coupling the lamp to a source of r-f electric power for starting and operating the lamp;

said lamp being a transparent sealed envelope containing a minor amount of metallic element and an ionizing gas;

said coupler comprising;

a grounded hollow cylinder of electrically conductive material open at one end with a grounded base member substantially closing the other end;

a helically coiled wire conductor concentrically within the cylinder and spaced from the inner walls thereof, said wire being one quarter wave long relative to the free-space wavelength of r-f power intended to be applied for operating the lamp, the end of the wire coil at the base member end of the cylinder being grounded and the end toward the open end of the cylinder being open circuited, the lamp being mounted with at least the major portion of the lamp substantially concentrically within the coil at the grounded end of the coil, and the open end of the cylinder extending beyond the open circuited end of the coil to avoid fringe effects; and

electrical connecting means for connecting to the coil a source of r-f electrical power that is sufficient to maintain a discharge in the lamp, said connecting means being tapped into the coil at a point near, but spaced from, the grounded end thereof, said point being selected such that, when the lamp is in operating by r-f power connected to the coil, the coupler is tuned to the frequency of said r-f power and the impedance of the lamp and coupler means at said tap point substantially matches the impedance of said r-f power source, whereby when said r-f power is applied to the coil, and before a discharge is ignited in the lamp, a voltage maximum occurs at the open circuited end of the coil and creates a potential extending through the lamp portion between said open circuited end and said base member for ionizing the gas in the lamp.

9. The combination of claim 8 in which said lamp has a bulbous portion which is said major portion of the lamp, and an elongated stem portion, said base member having a bore therethrough, said stem being received through said bore, and releasable clamping means clamping the stem in a selected longitudinal position through the bore.

10. The combination of claim 8 in which the outside diameter of the coil is on the order of one-half the inside diameter of the cylinder, in which the interior surfaces of the cylinder and base member are polished silver and in which the wire of the coil is essentially silver.

11. A resonator coupler for coupling a source of r-f electric power into an electrodeless discharge lamp for starting and operating the lamp, comprising:

a coiled wire conductor grounded at one end and open circuited at the other, means for mounting a discharge lamp within the coil, a generally tubular member of electrically conductive material surrounding and spaced from the coil so as to be in a capacitor relationship therewith, said member being grounded and being open at one end, the wire of the coil being one quarter wave long relative to the wavelength of r-f power intended to be applied for operating a lamp mounted in the coil, and electrical connecting means for connecting to the coil a source of r-f electrical power that is sufficient to maintain a discharge in a lamp mounted within the coil, said connecting means being tapped into the coil at a point intermediate the ends thereof, said point being selected such that, when a lamp mounted in the coil is in operation by r-f power connected to the coil, the coupler is tuned to the frequency of said r-f power and the impedance of said lamp and coupling means at said tap point substantially matches the impedance of said r-f power source, whereby when said r-f power is applied to the coil, and before a discharge is ignited in the lamp, a voltage maximum occurs at the open circuited end of the coil and creates a potential extending through the lamp for ionizing the gas in the lamp.

12. The combination of an electrodeless discharge lamp and a resonator coupler for coupling the lamp to a source of r-f electric power for starting and operating the lamp, said coupler comprising:

a coiled wire conductor grounded at one end and open circuited at the other, a discharge lamp mounted with at least a major portion within the coil, a generally tubular shield of electrically conductive material surrounding and spaced from the coil so as to be in a capacitor relationship therewith, said shield being grounded and being open at one end, the wire of the coil being one quarter wave long relative to the wavelength of r-f power intended to be applied for operating said lamp, and electrical connecting means for connecting to the coil a source of r-f electrical power that is sufficient to maintain a discharge in the lamp, said connecting means being tapped into the coil at a point intermediate the ends thereof, said point being selected such that, when the lamp is in operation by r-f power connected to the coil, the coupler is tuned to the frequency of said r-f power and the impedance of the lamp and coupler means at said tap point substantially matches the impedance of said r-f power source, whereby when said r-f power is applied to the coil, and before a discharge is ignited in the lamp, a voltage maximum occurs at the open circuited end of the coil and creates a potential extending through the lamp for ionizing the gas in the lamp.