Methods of and apparatus for coating the glass envelope and predetermined portions of the end caps of a fluorescent lamp with a coating of polymeric material including securing the end caps against displacement, subsequently, preheating the glass envelope and the predetermined portion of the end caps to a first predetermined temperature above the melting point of the polymeric material for a predetermined amount of time; subsequently, masking the electrical connecting pins and all of the end caps except the predetermined portion thereof; subsequently, exposing the glass envelope and the predetermined portion of the end caps to a fluidized bed of powder of the polymeric material for a predetermined amount of time to apply a coating of the powder to the glass envelope and to the predetermined portion of the end caps; subsequently, reheating the glass envelope and the predetermined portion of the end caps to a predetermined temperature above the melting point of the polymeric material and for a predetermined amount of time to melt and fuse the powder on the glass envelope and the predetermined portion of the end caps to form the applied powder into a substantially uniform thick coating of polymeric material and; subsequently, unmasking the pins and the end caps and unsecuring the end caps. Additionally, the glass envelope and the predetermined portion of the end caps may be cooled after reheating to a predetermined temperature and for a predetermined amount of time to quench and clarify the coating of polymeric material. Additionally, the temperature of the fluidized bed may be controlled to provide more uniform coating and pressurized air may be supplied to surround the connecting pins during coating to further prevent coating of the pins.
CROSS REFERENCE TO RELATED APPLICATIONS
This is a division of application Ser. No. 404,499 filed Aug. 2, 1982, which is a continuation-in-part of application Ser. No. 196,077 filed Oct. 10, 1981 (now abandoned) which is a continuation of application Ser. No. 44,473 filed June 1, 1979 (now abandoned) which is a continuation of application Ser. No. 940,292 filed Sept. 7, 1978 (now abandoned) which is a continuation of application Ser. No. 759,823 filed Jan. 17, 1977 (now abandoned).
A method of shatterproofing a fluorescent lamp having a glass envelope by extruding a polymeric coating over the lamp envelope so that it intimately embraces substantially all of the external contours of the lamp, including its glass envelope and end-ferrules thereby increasing the hoop strength of the glass envelope. The lamp is passed through an air lock into the main lumen of a crosshead which extrudes a cylinder of hot plastic that is radially drawn inward toward the lumen axis by an applied vacuum. A continuous chain of encapsulated lamps emerges from the crosshead that then may be cut apart to reveal individually completely encapsulated lamps.
A coated, labeled fluorescent lamp wherein the label is applied prior to coating, and wherein after labeling, the label, glass tube and portion of the end caps are covered with a coating material which is heated to form a tough, smooth, uninterrupted light-transmitting coating. The coating preferably bonds to the label to provide tamper resistance for the label, in addition to containment of shattered glass and lamp contents in the event of breakage of the lamp.
A method and apparatus for sequentially coating fluorescent lamps with a protective coating. The lamps are advanced continuously through coating apparatus which prepares the surfaces of the lamps for coating, then dips the lamps in a bath of liquid coating material, and subsequently cures the liquid coating material. The lamps may be labeled prior to coating, such that the coating provides tamper resistance for the labeling, in addition to containment of shattered glass and lamp contents in the event of breakage of the lamp.
A method and apparatus for coating the glass envelope and portions of the end caps of fluorescent light tubes in a continuous and sequential manner with a thermo-plastic material. The coating is applied by a cross head extruder through which the light tubes are sequentially fed. A vacuum applied during the coating process promotes direct and intimate contact between the coating and the light tubes. The end caps may be heated prior to coating to ensure adherence of the coating to the end caps and not to the glass envelope. Post-coating processes include cooling the coating, severing individual light tubes from the chain of sequentially coated light tubes, and readying the coated light tubes for packaging. The method is automatic, with the apparatus being automatically controlled by a control unit.
