Compact fluorescent lamp and method for manufacturing

Abstract

This compact fluorescent lamp comprises a discharge tube arrangement with at least one discharge tube. The tube is formed of glass, encloses a discharge volume filled with a discharge gas and has a fluorescent phosphor coating disposed on the inner surface of the tube. The tube forms a continuous arc path and the tube is provided with electrodes disposed at each end of the arc path. The lamp also comprises a ballast circuit connected to the electrodes for controlling the current in the tube and a lamp base for connecting said lamp to a power supply through a socket. The lamp is enclosed in an outer envelope comprising a substantially spherical portion enclosing the tube arrangement and an elongated end portion enclosing the ballast circuit. The end portion of the outer envelope is closed and sealed by a sealing means of the same material as the material of the outer envelope. The sealing means is connected to the envelope in a hermetically sealing way. A method for manufacturing a compact fluorescent lamp as described above is also disclosed. In the method, an outer envelope with an open end on the base side is provided. The open end of the envelope is closed and sealed with a sealing means to provide a hermetic seal. The envelope is separated by cutting along a circumferential line into an upper part and a lower part. The ballast circuit is introduced into the lower part and respective connection points of the ballast circuit are connected to power supply lead-out wires. The discharge tube arrangement is connected to respective connection points of the ballast circuit by lead-in wires. The lead-in wires and the lead-out wires are short and need not be insulated. The ballast circuit and the discharge tube arrangement are held and supported in the outer envelope by the connecting wires and fixing means.

1 . A compact fluorescent lamp comprising 
 a discharge tube arrangement, said discharge tube arrangement being formed of at least one discharge tube made of glass, enclosing a discharge volume filled with a discharge gas and having a fluorescent phosphor coating disposed on the inner surface of the tube, the tube forming a continuous arc path and further being provided with electrodes disposed at each end of the arc path;    a ballast circuit for controlling a current in the tube and being connected to the electrodes and a power supply;    a lamp base for connecting said lamp to said power supply through a socket;    an outer envelope comprising a substantially spherical portion enclosing the discharge tube arrangement and an elongated end portion with an open end;    the end portion of the outer envelope being closed and sealed by a sealing means of the same material as the material of the outer envelope, and the sealing means being connected to the envelope in a hermetically sealing way.    
   
   
       2 . The compact fluorescent lamp of  claim 1 , in which the outer envelope and the sealing means are made of glass.  
   
   
       3 . The compact fluorescent lamp of  claim 1 , in which the sealing means is a stem assembly comprising 
 a flare which is connectable in an air-tight manner to the open end of the envelope;    an exhaust tube extending through the flare for providing gas communication between the inside volume of the outer envelope and the outside atmosphere; and    power supply lead-out wires with inner ends for providing electrical connection with the ballast circuit and outer ends for providing electrical connection with contact terminals of the lamp base.    
   
   
       4 . The compact fluorescent lamp of  claim 1 , in which the envelope is comprised of two parts separated along a circumferential line in a plane perpendicular to the principal axis of the envelope, the two parts including an upper part for receiving the discharge tube arrangement and a lower part for receiving the sealing means and the ballast circuit, the two parts of the envelope being connectable and sealable to form a hermetically sealed envelope.  
   
   
       5 . The compact fluorescent lamp of  claim 4 , in which the circumferential separation line of the outer envelope is in the region of the elongated portion where the wall of the envelope has a substantially cylindrical form, and the ballast circuit is mounted on a printed circuit board, which is received in the lower part of the envelope and positioned in a plane substantially parallel to the separation plane at a distance below the separation plane sufficient for thermal protection during connecting and sealing the two parts.  
   
   
       6 . The compact fluorescent lamp of  claim 5 , in which the printed circuit board carrying the ballast circuit comprises connection points for connecting the power supply lead-out wires and the lead-in wires of the electrodes of the discharge tubes with the ballast circuit.  
   
   
       7 . The compact fluorescent lamp of  claim 5 , in which the outer envelope has a circumferential groove with an inside surface of the groove being in direct or indirect contact with the printed circuit board of the ballast circuit.  
   
   
       8 . The compact fluorescent lamp of  claim 1 , in which the discharge tube arrangement is connected to a fixing means for fixing the position of the discharge tube arrangement inside the outer envelope.  
   
   
       9 . The compact fluorescent lamp of  claim 8 , in which the fixing means is flexible in order to absorb shocks and vibrations of the envelope.  
   
   
       10 . The compact fluorescent lamp of  claim 8 , in which the outer envelope is provided with an arcuate recess in a top middle region thereof, the recess being connected to the fixing means.  
   
   
       11 . The compact fluorescent lamp of  claim 1 , in which the discharge tube arrangement is comprised of straight sections with a longitudinal axis substantially parallel to the principal axis of the fluorescent lamp and the neighboring sections being connected to each other in series to form a continuous arc path, and the tubes being arranged substantially at equal distance from the principal axis of the fluorescent lamp and from each other to provide a substantially homogenous illumination.  
   
   
       12 . The compact fluorescent lamp of  claim 1 , in which the discharge tube arrangement is comprised of a single tube with substantially straight end sections and an intermediate portion between the end sections and the end sections being at one end of the tube arrangement and in proximity to each other and the intermediate portion having a coiled configuration wound about the principal axis of the lamp to provide a substantially homogenous illumination.  
   
   
       13 . The compact fluorescent lamp of  claim 1 , in which the outer envelope is filled with air at a normal atmospheric pressure.  
   
   
       14 . The compact fluorescent lamp of  claim 1 , in which the outer envelope is filled with air at a decreased pressure.  
   
   
       15 . The compact fluorescent lamp of  claim 1 , in which the outer envelope is filled with inert gas at a normal atmospheric pressure.  
   
   
       16 . The compact fluorescent lamp of  claim 1 , in which the outer envelope is filled with inert gas at a decreased pressure.  
   
   
       17 . Method for manufacturing a compact fluorescent lamp comprising the steps of: 
 a) providing an outer envelope comprising a substantially spherical portion and an elongated end portion being terminated by an open end on a base side;    b) closing and sealing the open end of the elongated portion of the envelope with a sealing means of the same material as the material of the outer envelope to provide a hermetic seal, the sealing means also comprising power supply lead-out wires and an exhaust tube;    c) separating the envelope by cutting along a circumferential separating line in a plane substantially perpendicular to the principal axis of the envelope into an upper part for receiving a discharge tube arrangement with lead-in wires and a lower part closed by the sealing means at the base side for receiving a ballast circuit with connection points for the power supply lead-out wires and lead-in wires of the discharge tube arrangement;    d) introducing the ballast circuit into the lower part and connecting the respective connection points of the ballast circuit to the power supply lead-out wires;    e) connecting the lead-in wires of the discharge tube arrangement to the respective connection points of the ballast circuit;    f) bringing the two separated parts of the envelope along the separating line into contact with each other;    g) connecting and sealing the upper and lower part of the envelope along the separating line;    h) providing the envelope with a base; and    i) connecting the lead-out wires to contact terminals of the base.    
   
   
       18 . The method of  claim 17  in which the step of connecting the lead-in wires of the discharge tube arrangement to the respective connection points of the ballast circuit further comprises the steps of 
 j) providing the ballast circuit with terminal wires connected to the connection points and extending to the base side;    k) bending the free ends of the terminal wires upwards and leading the bent terminal wires through slots at the circumferential portion of the printed circuit board of the ballast circuit; and    l) providing electric connection between the lead-in wires and the free ends of the terminal wires by wrapping the lead-in wires and the terminal wires around each other.    
   
   
       19 . The method of  claim 17  further comprising the step of: 
 m) forming an arcuate recess in a top middle region of the substantially spherical portion of the envelope; and    n) furnishing the discharge tube arrangement with fixing means for fixing the position of the discharge tubes inside the envelope and for absorbing shocks and vibrations of the envelope before bringing the two separated parts of the envelope along the separating line into contact with each other.    
   
   
       20 . The method of  claim 17  comprising the step of filling the envelope with inert gas through the exhaust tube and sealing the exhaust tube after connecting and sealing the upper and lower part of the envelope along the separating line.  
   
   
       21 . The method of  claim 20  comprising the step of exhausting the envelope through the exhaust tube and sealing the exhaust tube after connecting and sealing the upper and lower part of the envelope along the separating line.  
   
   
       22 . The method of  claim 17  comprising the step of filling the envelope with air through the exhaust tube and sealing the exhaust tube after connecting and sealing the upper and lower part of the envelope along the separating line.  
   
   
       23 . The method of  claim 22  comprising the step of exhausting the envelope through the exhaust tube and sealing the exhaust tube after connecting and sealing the upper and lower part of the envelope along the separating line.