Electric lamps

Claim 2

A lamp comprising an envelope with an ellipsoidal reflecting surface and a transparent window and having a point source of light within said envelope at a focus of the ellipsoidal surface, wherein said point source of light comprises a tungsten ball with a lead for connection to one terminal of an electric power supply, said ball forming an anode of an arc system, a cathode with a lead for connection to a second terminal of said supply, the anode and cathode being arranged so that an arc can strike between the anode and the cathode causing the tungsten ball to become a light source, said anode and cathode leads passing through the reflecting surface along the major axis of the ellipsoid.

Claim 3

A lamp as claimed in claim 1 wherein said envelope is glass and wherein said ellipsoidal reflecting surface is formed by a portion of said envelope coated to form a reflector.

Claim 4

A lamp as claimed in claim 2 wherein the window is formed by a substantially flat portion of the glass envelope lying in a plane normal to the major axis of the ellipsoid.

Claim 5

A lamp as claimed in claim 1 wherein said window is integral with the reflecting surface.

Claim 6

A lamp as claimed in claim 1 wherein said window is sealed to the reflecting surface.

Claim 7

A lamp as claimed in claim 1 wherein said window is formed by a substantially flat portion of glass lying in a plane normal to the major axis of the ellipsoid.

Claim 8

A lamp comprising: a. an envelope having a transparent window portion, at least part of said envelope having an ellipsoidal reflecting inner surface, said ellipsoidal surface having a first focus inside said envelope and a second focus outside said envelope, b. a point source of light at said first focus, said point source comprising a tungsten ball with a lead for connection to one terminal of an electric power supply, said ball forming an anode of an arc system and a cathode with a lead for connection to a second terminal of said supply, the anode and cathode being arranged so that an arc can strike between the anode and cathode causing the tungsten ball to become a light source, c. said cathode being formed as a shield to intercept direct radiation from the ball to the window.

Claim 9

A lamp comprising: a. an envelope having a transparent window portion, at least part of said envelope having an ellipsoidal reflecting inner surface, said ellipsoidal surface having a first focus inside said envelope and a second focus outside said envelope, b. a point source of light at said first focus, said point source comprising a tungsten ball with a lead for connection to one terminal of an electric power supply, said ball forming an anode of an arc system and a cathode with a lead for connection to a second terminal of said supply, the anode and cathode being arranged so that an arc can strike between the anode and cathode causing the tungsten ball to become a light source, c. said cathode being formed as a shield to intercept direct radiation from the ball to the window.

Claim 10

A lamp comprising an envelope having a transparent window portion, at least part of said envelope having an ellipsoidal reflecting inner surface, said ellipsoidal surface having a first focus inside the envelope and a second focus outside said envelope, a point source of light at said first focus and means forming a shield between said first focus and said window to intercept direct radiation from the point source of light to the window, in combination with a horizontal wire positioned near said second focus to partially intercept a light beam from said point source of light, and thereby produce a horizontally extending shadow area extending through the beam.

Claim 11

A lamp comprising an envelope having a transparent window portion, at least part of said envelope having an ellipsoidal reflecting inner surface, said ellipsoidal surface having a first focus inside the envelope and a second focus outside said envelope, a point source of light at said first focus and means forming a shield between said first focus and said window to intercept direct radiation from the point source of light to the window, in combination with a horizontal wire positioned near said second focus to partially intercept a light beam from said point source of light, and thereby produce a horizontally extending shadow area extending through the beam.

Claim 12

A lamp comprising an envelope having a transparent window portion, at least a part of said envelope having an ellipsoidal reflecting inner surface, said ellipsoidal surface having a first focus insiDe said envelope and a second focus outside said envelope, and a point source of light at said first focus, in combination with a horizontal wire positioned near said second focus to partially intercept a light beam from said point source of light and thereby produce a shaped shadow.

Claim 13

A lamp comprising an envelope having a transparent window portion, at least a part of said envelope having an ellipsoidal reflecting inner surface, said ellipsoidal surface having a first focus insiDe said envelope and a second focus outside said envelope, and a point source of light at said first focus, in combination with a horizontal wire positioned near said second focus to partially intercept a light beam from said point source of light and thereby produce a shaped shadow.