Field of the Invention

The invention relates to shrouds for use with electrical lamps and in particular to fragment retention lamps.

Background of the Invention

The closest prior art is the applicant's own process of coating fluorescent tubes with a plastics film, so that if the tube shatters in use, the plastics film retains all of the glass fragments. There are two methods of film coating lamps for this purpose. The first method is to form a plastic tube, which is fitted closely over the lamp and then subsequently heat-shrink the tube around the lamp. The second method is the Applicant's own method of feeding an uncoated lamp through a crosshead extrusion, which progressively coats the lamp along its length. The coating of the lamp is subsequently cooled as the lamp emerges from the cone of molten material. Problem to be Solved

The problem/main disadvantage of the fragment retention lamp is that it is a statutory requirement that a representative sample of one of these coated tubes, after coating, should survive a so-called "drop test". In this test, the coated tube is held horizontally and then dropped from a distance of approximately four metres. On impact, the tube fractures and no sliver of glass must escape the tube, otherwise the tube fails the test.

If in practice the tube hits the ground at an angle, i.e. wherein the periphery of its own soft aluminium end cap becomes dented, it then becomes possible for a fragment of glass to escape the tube through the dent-formed gap between the cap and the plastics-film coating.

The invention, by coating the end cap with a suitable plastics material, will contain the glass on impact and therefore seeks to solve this problem.

Therefore, the problem which the invention addresses may be defined as how to improve the containment of glass fragments and debris of a fragment retention lamp, after it has been fractured at one end.

Summary of the invention

In a first broad independent aspect the invention provides a shroud adapted, in use, to shroud a metallic end cap disposed at one end of a fragment retention lamp, said shroud comprising a first body portion and a second body portion; wherein said first body portion covers in use an external wall of said end cap, and said second body portion in use covers an end face of said end cap and incorporates one or more orifices through which, in use, an electrical contact pin or pins can protrude from said shroud. The metallic end cap is preferably disposed at both ends of a fragment retention lamp.

This configuration enables the containment of any glass fragment and / or debris produced when the fragment retention lamp is dropped and fractured at one or more ends. The shroud provides a protective coating about each end of lamp and is an extension of the protective coating that extends along the lamp. The shroud prevents glass fragments and / or debris from escaping the lamp when one end of the lamp becomes fractured or damaged. The shroud prevents glass fragments and / or fragments from escaping the lamp through one or more dents or disfigurations of the associated metallic end cap, which is typically formed from aluminium based material.

Therefore, all fragments and / or debris are contained and can be easily disposed of without cause any contamination to the environment around the lamp. This effect is very advantageous when using fragment retention lamps within clean or sterile environments, such as food production or drug manufacturing facilities.

Preferably, said first body portion of said shroud further comprises an extended portion to cover, in use, a lamp body portion beyond the cap. This enables the shroud to attach itself to the lamp body, as well as the cap. Therefore, if the end of the lamp, which is covered by the shroud is fractured, any glass fragments and / or debris are contained within the shroud are prevented from escaping between the protective coating of the lamp and the outer wall of the end cap

Preferably, said shroud further comprising a friction fitting means for attaching said shroud to said lamp body. This enables the shroud to attach itself to the lamp body, in a manner which prevents the shroud from moving and becoming unattached from the lamp body and/or end cap.

Preferably, said second body portion of said shroud abuts an outer end surface of said end cap. When the end of the lamp is fractured, this configuration prevents any glass fragments and / or debris from escaping the shroud from the end face of the end cap and / or where the electrical pins protrude from the end cap.

This configuration also maximises the pin length of the electrical contact pins of protruding from the end face of the end cap.

Preferably, said shroud is a preformed cap. This provides a quick and less labour intensive way of locating the shroud to the end of the lamp and associated end cap, without having an prior preparations, which are required when forming the shroud on the lamp end. Preferably, said shroud is preformed from a plastics material. This provides a shroud formed from an electrical insulating material, which prevent the electrical contact pins from short circuiting to each other when the shroud is fitted to the lamp end.

Preferably, said shroud is formed from a coating of plastics material. This provides a quick means and efficient means of forming a close and tight fitting shroud on to the end of the lamp and its associated end cap. In a second broad independent aspect the invention provides a method of shrouding a metallic end cap of a fragment retention lamp, characterised in that the method comprises film-coating the or each said lamp end cap in a manner such as to shroud external wall and the end face of the or each said cap and surround the or each electrical contact pin of the cap whilst allowing said pin(s) to protrude by the necessary amount from said end face; in that the film-coating step, which forms the shroud when completed, is on operation distinct from the fragment retention film-coating of the lamp body itself and in that it takes place before or after the last said film-coating.

This method provides a efficient and cost effective method of shrouding the end portions of a fragment retention lamp, which provides a high through put of shrouded lamps, which is also scalable for high volume production.

Preferably, a method of shrouding the end cap of a fragment retention lamp, the method being carried out, substantially as described herein.

Preferably, a fragment retention lamp incorporating said shroud.

Preferably, a fragment retention lamp with one or more of its end caps shrouded by said method.

Brief Description of the Figures

Figure 1 shows a schematic side view of a fragment retention lamp incorporating a damaged end cap. Figure 2 shows a schematic end view of a fragment retention lamp incorporating a damaged end cap.

Figure 3 shows a cross-sectional view of a fragment retention lamp incorporating a shroud cover, over a protective film layer and a metallic end cap.

Figure 4 shows a cross-sectional view of a fragment retention lamp incorporating a shroud, which encloses a metallic end cap, whereby the shroud is underneath a protective film layer.

Figure 5 shows a cross-sectional view of a fragment retention lamp incorporating a protective film layer over one end of the lamp and associated end cap.

Figure 6a shows a cross sectional view of a fragment retention lamp incorporating a coating portion which extends beyond one end of the lamp and its associated end cap.

Figure 6b shows a cross sectional view of the fragment retention lamp incorporating a coating portion which has been folded against the face of its associated end cap.

Detailed Description of the Figures

Figure 1 shows an exaggerated part-elongate cross-section of a conventional fluorescent lamp, generally indicated by arrow 1 , which is coated by a plastics film 2. The film coating 2 does not cover the electrical contact pins 4 and 5. The tube 1 incorporates a

conventional metallic end cap 6, located at one end of the tube 1, which is typically manufactured from an aluminium material. The cap 6 incorporates an upper damaged portion 7, which has been dented inwards. The damaged portion 7 of the cap 6 allows glass fragments from the tube 1, to escape the plastics film coating 2 in the direction indicated by arrow 3.

Figure 2 shows an enlarged cross-sectional end view of the tube 1 , which is identical to the tube shown in Figure 1. The tube 1 is substantially cylindrical in shape and incorporates a metallic end cap 6. The end cap 6 incorporates two electrical contact pins 4 and 5, which are axially arranged about the centre of the cap 6. The cap 6 incorporates an upper damaged portion 7, which has been dented inwards from the cap's outer peripheral edge. Therefore, creating a gap 10 between the metallic end cap 6 and the plastics coating 2, which may allow glass fragments to escape the tube 1.

Figure 3 shows an enlarged elongate section showing a fluorescent lamp end portion, generally indicated by arrow 20, according to the invention.

The tube of the lamp 20 incorporates a metallic end cap 23 located at one end. The tube 20 also incorporates a plastics coating 21 , which is adjacent the outer surface of the tube 20. A shroud 22 is located over the end tube 20 and is attached to the plastics coating 21. The shroud 22 is typically formed from insulating plastics material, which may be in a mouldable, machinable form. Or alternatively, the shroud 22 may be formed from a coating of plastics material. The coating may be typically applied from a spray or dipping means. The shroud 22 is manufactured from a plastics material because it is incapable of short-circuiting the electrical contact pins 24 and 25 together and therefore eliminating any possibility of an electrical hazard. Furthermore, the plastics material is a lightweight material and will therefore not put any excessive mechanical loading on to the electrical contact pins 24 and 25 whist the tube is connected to a light fitting.

The shroud 22 is configured so that it provides a close fitting to both the outer surface of the fluorescent lamp 20 and the end face of the metallic end cap 23. The electrical contact pins 24 and 25 extend through two orifices 26 and 27 within the shroud 22, and subsequently protrude from the outer surface of the end cap by a predetermined amount. The shroud 22 incorporates a portion, which extends over the outer wall of the end cap 23 and a portion of the tube 20. The shroud also incorporates a portion, which covers and abuts the end face portion of the metallic end cap 23, which facilitates in the protrusion of the electrical contact pins 24 and 25 from the outer surface of the shroud 22. Figure 4 shows an enlarged elongate section showing a fluorescent lamp end portion, generally indicated by arrow 30, according to an alternative embodiment of the invention.

The tube 30 of the lamp incorporates a metallic end cap 33 located at one end. The tube 30 incorporates a shroud 32 located over one end of the tube and is attached directly onto the outer surface of the fluorescent lamp 30. A plastics coating 31 is then applied to the outer surfaces of both the illumination tube 30 and the shroud 32. The shroud 32 is shown to extend along the outer wall of the end cap and onto a portion of the tube 30. The shroud 32 also abuts the outer end surface of the end cap 33. The electrical contact pins 34 and 35 extend through two orifices 36 and 37 within the shroud 32 and are free from any plastics coating material.

The shroud may be in a form of a formed plastics shell cap and others, but it is important that the electrical pins project at least by a given minimum distance (set by statutory requirements) from the end face of whatever cap or caps adjoin them.

In an alternative embodiment of the invention, the inner surface of the shroud may incorporate a high friction inner surface, which enables the shroud to attach itself to the plastics coating by a friction fitting means. Or, alternatively, the shroud may incorporate an adhesive/sticky surface, which provides a means of bonding the shroud 22 to the lamp 20.

In an alternative embodiment of the invention, the shroud may be formed from a synthetic rubber material, such as Neoprene (TM). This material enables the shroud to be rolled up, and then subsequently rolled on to the end of the lamp and its associated end cap, whilst enabling the electrical contact pins to be placed through shroud. The material also incorporates a high friction surface, which when attached to the outer surface of the tube, prevents the shroud from being pulled off. The rubber material may also incorporate a bonding / adhesive material upon its inner surface to augment the shrouds attachment of the shroud to the tube end and metallic end cap.

Figure 5 shows an enlarged cross sectional end view of an elongated fluorescent lamp end portion, generally indicated by arrow 40, according to another alternative embodiment of the invention.

The tube of the lamp 40 incorporates a metallic cap 41 located at one end. A protective plastics coating 42 is then applied to the outer surface of the lamp 40. The coating 42 extends along the lamp 40 and onto the outer side surface 43 of the metallic end cap 41. The coating 42 is bonded to the outer side surface 43 of the metallic cap 41 via a bonding/adhesive material 44. The bonding/adhesive material 44 is applied to the outer side surface 43 of the metallic end cap 41 prior to the application of the plastics coating 42.

Or alternatively, the bonding/adhesive material 44 is applied to the inner surface of the plastics coating 42 prior to the plastics coating 42 being applied to the outer side surface 43 of the metallic cap 41.

Or alternatively, the bonding/adhesive material 44 is applied to both the inner surface of the plastics coating 42 and the outer side surface 43 of the metallic cap 41 prior to the plastics coating 42 being applied to the outer side surface 43 of the metallic cap 41. In use, this embodiment of the invention provides a plastics coating along both the lamp and the outer side surface of the metallic end cap. The plastics coating does not extend beyond the outer edge, which is adjacent the end face of the metallic cap. Each electrical pin, which extends from the metallic end cap, is free of any plastics coating along its length, therefore maximising its protrusion from the metallic end cap.

Figure 6a shows an enlarged cross sectional end view of an elongated fluorescent lamp end portion, generally indicated by arrow 50, according to another alternative embodiment of the invention. The tube of the lamp 50 in incorporates a metallic cap 51 located at one end. A protective plastics coating 52 is then applied to the outer surface of the lamp 50. The coating 52 extends along the lamp 50 and onto the outer side surface 53 of the metallic end cap 51. The coating 52 incorporates excess portion 55 about the diameter of the end cap 51, which continues to extend beyond the outer edge 54 that is adjacent the end face 57 of the metallic cap 51. The coating portion 55 extends along the same horizontal plane as that of the tube of the lamp 50.

Figure 6b shows another enlarged cross sectional view of the elongated lamp end portion 50 shown in Figure 6a, wherein the excess coating portion 55 is folded over the outer edge 54 and is adjacent to the end face 57 of the metallic cap 51. The extension of coating portion 55 beyond the outer edge 54 has to be of sufficient length to provide a substantial attachment to the front face 57 of the metallic cap 51, whilst not impeding or depositing any coating material 52 onto either of the two electrical contact pins 58 and 59 protruding from the end face 57 of the metallic cap 51. The length of the extension of coating portion 55 may be typically in the range of 1 to 25 millimetres, or beyond.

The inner surface of the coating material may also incorporate a layer of bonding / adhesive material, which maintains the coating portion in a folded position against the end face of the metallic cap.

The extended coating portion 55 may also incorporate a layer of bonding / adhesive material to maintain the extended coating portion in a folded position against the end face of the metallic cap. The bonding / adhesive material may be activated / cured

conventionally or by being exposed to electromagnetic radiation. The electromagnetic radiation may originate from a source, such as a laser.

In another alternative embodiment of the invention, the plastics coating is heat shrunk to the outer surface of the lamp via a heating source, such as a heating tunnel. Once attached to the lamp, the coating is cut beyond the outer edge of the metallic end cap, which provides a coating portion which extends about the diameter of the metallic end cap in a similar manner to Figure 6a. The outer edge of the extended coating portion is pressed and formed flat against the end face of the metallic end cap during or after the heat shrinking process. The extended coating portion may also incorporate a layer of bonding / adhesive material to facilitate in attaching the extended coating portion to the end face of the metallic end cap. Again the bonding / adhesive material may be conventionally activated / cured or by being exposed to electromagnetic radiation. The electromagnetic radiation may originate from a source, such as a laser. A method of coating a metallic end cap of a fragment retention lamp incorporating the steps of:

• Applying a protective cap over a first metallic end cap of a first fragment retention lamp to cover its end face and electrical contact pins; • Locating a second metallic end cap of a second fragment retention lamp into said protective cap to cover its end face and electrical contacts therefore linking said first fragment retention lamp to said second fragment retention lamp via protective cap

• film coating the body of said first fragment retention lamp and said first end cap and / or said second fragment retention lamp and said second end cap in a manner such as to coat the external wall of said first end cap and / or said second end cap; and

• Separating and / or cutting said film coating between said first fragment retention lamp and said second fragment retention lamp.

Said method of coating a metallic end cap of a fragment retention lamp further incorporates one or all of the following steps:

• applying bonding / adhesive material to the inner surface of said film coating; and

• bonding / adhering said film coat to said external wall of the or each said cap.

In another embodiment of said method of coating a metallic end cap of a fragment retention lamp further incorporates one or all of the following steps:

• Separating and / or cutting said film coating between said first fragment retention lamp and said second fragment retention lamp, wherein a portion of film coating is extends beyond the outer edge of the end face of said end cap adjacent to said protective cap.

• Folding / forming said extended portion of film coating about said outer edge of said cap against the end face of said cap.

• applying bonding / adhesive material to the inner surface of said extended portion of film coating; and

• bonding / adhering said extended portion of film coating to said end face of said cap.