GB2091405A - Light fitting assembly - Google Patents

Abstract

A light fitting assembly, in particular a flame proof light fitting, comprises a translucent tubular housing (1) receiving a tubular light bulb (8), the housing (1) being releasably attached at one end thereof to a second housing (13) containing any required transformer, ballast, starter, choke or other control gear for operating said light bulb (8). The second housing (13) has contacts (20) co-operable with a complementary removable contact assembly associated with an electrical power supply and which preferably embodies automatic switch means for isolating the light fitting as it is removed therefrom. <IMAGE>

Description

SPECIFICATION Light fitting assembly This invention relates to light fitting assemblies, more particularly, but not exclusively, flame-proof fittings of a type capable of being employed for illuminating regions in which explosive or inflammable atmospheres may be present and wherein possible sources of arcing are avoided or rendered adequately shielded from the ambient atmosphere.

Flame proof light assemblies of this general type exist but, in the case of the prior art assemblies, they are generally composed of a multitude of different parts and cannot easily be opened to replace a light bulb or tube or to otherwise service the assembly. In particular, in the case where the light assemblies employ neon or fluorescent type light tubes, a defective,ballast, starter or the like cannot be replaced easily and swiftly, and generally an electrician is required to perform the replacement or repair.

One improved form of simple flame-proof light fitting assembly is disclosed in our co-pending Patent Application filed simultaneously herewith under the title "FLAME-PROOF LIGHT FITTINGS".

Whilst providing an effective and simple light fitting assembly our earlier patent application requires that somewhat costly dies be employed in the manufacture of the light fitting assemblies.

Whilst amortization of such dies can easily be achieved it is considered to be advantageous to provide a light fitting assembly which can be produced by employing lesser financial capital than would be necessary in the case of our earlier proposal. It must be pointed out that whilst financial capital requirements instigated the present invention it is considered that the flame proof light fitting assembly provided by the instant invention is, in any event, advantageous at least from a simplicity point of view.

According to this invention there is provided a light fitting assembly comprising a translucent tubular housing adapted to receive a tubular light bulb or the like and wherein the translucent housing is releasably attached at one end thereof to a second housing containing any required transformer, ballast, starter, choke or other control gear for operating said light bulb, and wherein the second housing has contacts adapted to cooperate with a complementary removable contact assembly associated with an electrical power supply.

Further features of the invention provide for the light fitting to be of a flame-proof type in which case the releasabie connections between the two housings and between the second housing and contact assembly are flame-proof; for the second housing to be adapted to be releasably attached to one end of the tubular housing in substantially colinear relationship relative thereto; for the second housing to have external screw threads on a neck portion thereof adapted for alignment with matching threads on the exterior of the tubular translucent housing and wherein an internally screw threaded sleeve operates to connect the two externally threaded members together in flame proof manner; for any ballast, starter, choke or other control gear located in the second housing to be encapsulated therein; for the contacts on the second housing to be pins projecting from one end of an externally screw threaded cylindrical portion of the second housing; and for the said cylindrical portion of the second housing; and for the said cylindrical portion of the second housing to be adapted for co-operation with an axially movable contact block having cooperating screw threads on the outer surface thereof and adapted to co-operate with an inner contact arrangement of a contact assembly as set forth in our co-pending Patent Application filed simultaneously herewith under the title "FLAME PROOF ELECTRICAL CONTACT ASSEMBLY".

Our said co-pending Patent Application relates to a contact assembly comprising a body having means for supplying electrical power to fixed contacts located at an inner region of a biind tubular housing in which a contact block is movable axially within the housing and has contacts carried thereon for co-operation with the fixed contacts by physical engagement therewith when the contact block is located at an innermost position in the housing. Contact terminals at the outer region of the contact block are provided for co-operation with the fixed contacts on the second housing, in the above case the pins, with means being provided for ensuring that the contact block remains in contact, at its periphery, with the inner surface of the tubular housing in flame proof manner when it is moved axially along said housing.Stop means are provided for operatively preventing at least inadvertent movement of the contact block out of the tubular housing. Finaily, formations are associated with the housing and/or contact block for preventing engagement or disengagement of the contact block with a terminal member unless the contact block is located at an outermost position in which it is disconnected relative to the fixed contacts.

Thus, it will be understood, that engagement and disengagement of the contact block and terminal member, which in the above case is the said part of the second housing, can only take place when the contact block is isolated from the electrical supply as a result of its being disconnected relative to the fixed contacts in the housing of the contact assembly.

An embodiment of the invention will now be described, by way of an example, with reference to the accompanying drawings, in which: Fig. 1 is a longitudinal sectional elevation of a flame proof light fitting according to this invention and, Fig. 2 is a similar elevation of a contact assembly for use in conjunction with the flame proof light assembly.

Referring firstly to Fig. 1 of the accompanying drawings a flame proof electrical light fitting assembly comprises a tubular translucent housing 1 made of a suitable impact resistant material such as a polycarbonate. The tubular housing 1 can be defined by a simple length of extruded tube having an end fitting 2 adhesively or otherwise sealingly and permanently secured to one end 3 of the tubular translucent housing 1. This end fitting 2 conveniently has a deep groove 4 into which the end of the tubular housing 1 fits in order to promote the desired degree to which the fitting 2 is flame proof. The fitting 2 also has, in the preferred form, radially extending support member 5 formed integral therewith so that this end of the light fitting assembly can be supported by such support member.

Located adjacent the end fitting 2, and optionally secured thereto, is a contact arrangement 6, which co-operates with an adjacent end 7 of a fluorescent or other tubular light bulb 8. The wires supplying such contact arrangement may simply be laid inside the tubular housing 1 to extend along a suitable path or, alternatively, where a special extruded housing is produced, an integral contiguous passage (not shown) could be formed adjacent the tubular housing itself for conducting the wires to the opposite end of the translucent housing 1.

A sleeve 10 having external screw threads 11 thereon is secured to the outer surface of the translucent housing 1 at the ends thereof opposite the fitting 2. This sleeve 10 is located somewhat inwardly from the free end of the tubular housing 1 such that a co-acting externally screw threaded neck portion 12 of a second housing 13 can be slid over the free end of the translucent housing 1 to abut with the sleeve 10 thereon. Suitable co-operating locating formations are provided to ensure that the correct relative angular position of the two housings 1 and 13 is achieved in which position the two screw threads form a continuous screw thread which can be held together by means of an internally screw threaded connector sleeve 14 located over the length of both screw threads.A shoulder 1 5 on the second housing 1 3 forms a stop for the connector sleeve 14 at one end thereof and a circlip 1 6 located in a groove 1 7 in the sleeve 10 secured to the translucent housing 1 forms a stop at the other end. The connector sleeve 14 can only be removed thus once the circlip 1 6 has been removed.

These screw threads are designed such that they comply with the required flame proofing standards and generally no further flame proofing would be necessary. However, if additional sealing is required a ring seal 30 can be installed between the end of connector sleeve 14 and shoulder 1 5 on the second housing 1 3. The other end of the connector sleeve 14 can be sealed to the sleeve 10 fixed to the housing 1 by an O-ring 31 located in a groove in the sleeve 10 inwardly of the circlip 1 6 to co-operate with a smooth zone of the internal surface of the connector sleeve 14. Finally an O-ring type seal could be rolled into position in the space 32 between the tubular housing 4 and inside of the neck 12.

The second housing 1 3 is also of tubular shape and is arranged co-axially with the translucent housing 1. The housing 13 can be made of any suitable material and, in this regard it is considered that die cast aluminium would be most suitable from a cost and convenience point of view. The housing 1 3 receives all necessary ballasts, chokes, starters or other control gear for supplying the proper power to the fluorescent or other light tube 8 located in the translucent housing 1. This equipment is all completely encased, or "potted" in synthetic resin material and terminates at the end nearer the light tube 8 in a contact assembly 1 8 for co-operation with the adjacent end of the light tube itself.The arrangement is such that the contact assemblies are each properly in contact with the appropriate portions of the light tube 8 when the connector sleeve 1 4 is properly located to connect the two housings 1 and 1 3 in co-linear relationship.

The opposite end of the second housing 1 3 has external screw threads 1 9 thereon and a pair of projecting current carrying contact pins 20 extending from the free end thereof and an earth pin 21 a. These contact pins are arranged to cooperate with complementary sockets in an axially movable contact block of a contact assembly as illustrated in Fig. 2.

The contact block 21 has associated sockets 22 which receive, in use, the pins 20 on the second housing 1 3 and is externally screw threaded with co-acting screw threads 23 and these screw threads 23 co-operate with complementary screw threads on the inner surface of a blind ended tubular housing 24 as described in our said co-pending Patent Application. This housing 24 has fixed contacts 25 at its innermost end with which spring loaded contacts 26 on the inner end of the contact block 21 co-operate to complete the circuit when the contact block 21 is located in its innermost position. It will be readily understood that the screw threads on the second housing 13 and contact block assembly 21 are made to form one continuous thread arrangement co-operating with the threads on the tubular housing 24.Thus, with the contact block 21 in an outer position and thus with its contacts 26 separated from the fixed contacts 25 at the inner end of the tubular housing 24 the pins on the second housing 1 3 of the light fitting can be engaged or disengaged from the co-operating socket in the contact block assembly 21. However, once the contacts are engaged and the screw threads on the outside of the second housing 1 3 co-operate with those of the tubular housing 24 relative axial movement of the contact block 21 and second housing 13 is no longer possible and thus the assembly can be screwed into the tubular housing 24 until the spring loaded contacts 26 on the contact block 21 close the circuit with the fixed contacts 25. It will be understood that opening and closing of the circuit by screwing and unscrewing the contact block 21 into and out of the tubular housing 24 can be achieved whilst the electricity is connected since any arcing is protected by the screw threads which, as in the above described case, are designed to be flame proof to the required extent.

An elastomeric sealing ring 27 can be provided to seal between the end of the socket and a flange 28 on the second housing 13 in order to enhance the flame proof characteristics if required.

The contact assembly illustrated in Fig. 2 can be provided with flame proof cable glands 29 or other arrangements whereby electrical conductors 30 can be passed into a connection chamber within the contact assembly and the contact assembly could be provided with a support arrangement for co-operation with the axially projecting formation on the fitting at the opposite end of a similar flame proof light fitting assembly.

This arrangement is suited for providing strip lighting assemblies wherein one flame proof light fitting is connected in end on relationship with the next.

It will be understood that numerous variations may be made to the above-described embodiment of the invention without departing from the scope of the appended claims.

It will also be understood that the abovedescribed light fitting can be inexpensively manufactured without an enormous capital outlay being required for dies and the like. Whenever a light fitting needs attention the fitting can simply be disconnected from the circuit by moving the contact block assembly 21 described above axially out of the tubular housing of the contact arrangement to enable the second housing 13 of the light fitting to be removed therefrom. Once removed, the second housing 13 can simply be replaced if the ballast, choke, starter or other equipment contained therein is defective or requires attention or, the electrical light bulb 8 can simply be slid out of the translucent housing 1 and replaced if this is required. Thus, extremely simple maintenance can be carried out easily even in an explosive or inflammable atmosphere and by relatively unskilled labour. The presence of the circlip is considered sufficient to protect the separation of the tubular and second housings.

Claims (11)

1. A light fitting assembly comprising a translucent tubular housing for receiving a tubular light bulb or the like and wherein the translucent housing is releasably attached at one end thereof to a second housing containing any required transformer, ballast, starter, choke or other control gear for operating said light bulb, and wherein the second housing has contacts arranged to cooperate with a complementary removable contact assembly associated with an electrical power supply.

2. A light fitting assembly as claimed in claim 1, in which the light fitting is of a flame-proof type and the releasable connections between the two housings and between the second housing and contact assembly are flame proof.

3. A light fitting assembly as claimed in claim 1 or claim 2, in which the second housing is attached to the one end of the tubular housing in substantially co-linear relationship thereto.

4. A light fitting assembly as claimed in any of the preceding claims, in which the second housing has screw threads on a neck portion thereof arranged for alignment with matching threads on the exterior of the tubular translucent housing and wherein an internally screw threaded sleeve operates to connect the two externally threaded members together in flame proof manner.

5. A light fitting assembly as claimed in claim 4, in which the sleeve abuts a stop formation to prevent it from being rotated in a direction tending to move it axially towards the second housing and a removable stop is associated with the tubular housing to prevent rotation in the opposite direction.

6. A light fitting assembly as claimed in claim 5, in which the removable stop is in the form of a circlip co-operating with a groove in the outer surface of the tubular housing.

7. A light fitting assembly as claimed in any of the preceding claims, in which the contents of the second housing are encapsulated permanently thus providing a replaceable second housing unit.

8. A light fitting assembly as claimed in any of the preceding claims, in which the contacts on the second housing are pins projecting from an externally screw threaded end of the second housing.

9. A light fitting assembly as claimed in any of the preceding claims, in which the second housing and its said contacts are arranged for co-operation with an axially movable contact block having cooperating screw threads on the outer surface thereof and arranged to co-operate with an inner contact arrangement of a contact assembly and wherein the screw threads on the outer surface of the contact block are arranged to form a continuation of matching screw threads on an end of the second housing when its contacts cooperate and movement of the contact block is rendered possible by co-operating internal screw threads in a socket in which the inner contact arrangement is located.

10. A light fitting assembly substantially as herein below described with reference to and as illustrated in the accompanying drawings.

11. A second housing particularly adapted to define the second housing of a light fitting assembly as claimed in any one of claims 1 to 10.