AU713182B2 - Explosion proof fluorescent lighting equipment - Google Patents

Description

1

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

ee tt Name of Applicant/s: Actual Inventor/s: Address of Service: Invention Title: Nordland (Proprietary) Limited Josef Anton BUHLMANN SHELSTON WATERS MARGARET STREET SYDNEY NSW 2000 "EXPLOSION PROOF FLUORESCENT LIGHTING EQUIPMENT" p The following statement is a full description of this invention, including the best method of performing it known to us:- (File: 19589.00) _1 It_ II 1_ M "EXPLOSIVE PROOF FLUORESCENT LIGHTING EQUIPMENT' FIELD OF THE INVENTION This invention relates to equipment to be used with fluorescent lighting under possibly explosive ambient conditions.

BACKGROUND OF THE INVENTION Fluorescent lighting is widely used in conditions such as underground mining and petro-chemical industries for example where it is imperative that ignition of explosive gases is avoided. Stringent specifications have been laid down by ••mining and other authorities to ensure that explosion proof lighting equipment is 10 properly manufactured and supplied.

One of the difficulties encountered with this type of "increased safety" of luminaires has been that standard two pin fluorescent tubes with their internal heating coils for starting cannot be used with conventional tube ballasts under explosive conditions. The use of special single pin cold-start tubes very appreciably increase the cost of explosion proof lighting.

The development of reliable electronic ballasts has enabled single pin or two pin fluorescent tubes to be used and in the latter case standard tubes with the heater S. ooo S• elements bridged out of circuit can be used. This greatly reduces the cost of explosion proof lighting.

The use of electronic ballasts requires a ballast housing which provides either flame proof or explosion proof protection.

I CI__ I_ II -3- OBJECT OF THE INVENTION It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

The present invention, at least in a preferred form, provides an explosion proof electronic ballast for fluorescent lighting which is inexpensive to produce and which meets the required standards for such equipment.

SUMMARY OF THE INVENTION According to this invention there is provided an explosion proof electronic ballast comprising a standard electronic ballast located in a length of standard steel tubing closed at one end, the ballast located by a perforated plate set into the opposite end of the "tube with the ballast electrical leads threaded through the perforations and anchored in non-combustible settable material filling the end of the tube around the leads and set, further including means for retaining the plate in position.

Unless the context clearly requires otherwise, throughout the description and the 15 claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of"including, but not limited to".

Further features of this invention provide a means for retaining the plate, for this means to be a pin extending transversely through the tube and opposite walls thereof, for the plate to be of plastics material such as a suitable polycarbonate and for the settable material to be a synthetic resin adhesive conveniently a structural adhesive such as that sold commercially under the name "Araldite".

-3a- The invention also provides for the one end of the tube to be closed by a metal plate welded into the tube and having a screwthreaded hole therethrough engaged by a sealing plug.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 depicts a plan view of a preferred embodiment of the electronic ballast of the present invention, shown partly in section; and Fig. 2 is a cross-section of the electronic ballast depicted in Fig. 1.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWING As illustrated the housing 1 for an electronic ballast 2 is formed from standard structural rectangular steel tubing. Preferably the tubing is of a size 50.8 x 38.1 x S v 0 -4- 3 mm because this comfortably houses commercially available ballasts. These ballasts are made to the same cross sectional size although they are of different lengths. The electronic ballast sold under the name "Osram" has been found suitable both from quality and cost considerations. This ballast requires a tube length of 450 mm but it will be appreciated that different lengths of tube to accommodate different ballasts can easily be provided.

One end of the tube is closed by a steel plate welded into position. This plate has a central screwthreaded aperture which is sealed by a screwthreaded plug located therein. The plug can be removed to enable the "i 10 housing to be pressure tested and is also used to attach a lug to the •housing. This lug provides means for earthing the ballast in use.

opposite end of the tube has a perforated plate of polycarbonate material inserted as a friction fit therein and set back, conveniently, about mm.

The electrical leads (10) of the electronic ballast are threaded through the apertures (11) through the plate prior to the ballast and plate being inserted into the tube. The size of the components enables the ballast to be freely inserted into the tube without further support means.

A pin (12) is inserted through holes (13) in opposite walls of the tube to extend 20 transversely across the tube and project on either side. The pin is retained in position by circlips (14) adjacent each end.

Structural adhesive such as that sold under the name "Araldite" is introduced to fill the end of the tube around the electrical leads and the pin (12) to complete the ballast assembly. With the adhesive set around the pin (12) it is not possible for the plate and ballast to be unintentionally removed from the tubular housing.

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The ballast assembly above described meets all the specifications set for this kind of equipment and enables standard commercially available components to be used. This enables the product to be economically produced.

While the ballast assembly has been described as suitable for fluorescent lighting it will be understood that it may be used in other circumstances where this kind of equipment is necessary and the invention extends to include such ballasts.

Although the invention has been described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

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Claims (7)

1. An explosion proof electronic ballast comprising a standard electronic ballast located in a length of standard steel tubing closed at one end, the ballast located by a perforated plate which is set into the opposite end of the tube, with the ballast electrical leads threaded through the perforations and anchored in non-combustible settable material filling the end of the tube and set around the leads, the explosion proof ballast further including means for retaining the plate in position.

2. An explosion proof ballast as claimed in claim 1 in which the means for retaining the plate is a pin extending transversely through the tube and opposite walls thereof.

3. An explosion proof ballast as claimed in any one of the preceding claims in which •the plate is made of plastics material.

S4. An explosion proof ballast as claimed in claim 3 in which the plastics material is a suitable polycarbonate and the settable non-combustible material a synthetic resin. 9*O o*

5. An explosion proof ballast as claimed in claim 4 in which the synthetic resin is a 15 structural adhesive.

6. An explosion proof ballast as claimed in any one of the preceding claims in which the closed end of the tube is closed by a metal plate welded into the tube and having a screwthreaded hole therethrough engaged by a sealing plug.

7. An explosion proof ballast substantially as described and illustrated in the accompanying drawings. DATED THIS 30th Day of September, 1999 NORDLAND (PROPRIETARY) LIMITED Attorney: STUART M. SMITH Fellow Institute of Patent Attorneys of Australia of BALDWIN SHELSTON WATERS