AU2005203039B2 - Environmental enclosure - Google Patents

Description

-1-

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant/s: Actual Inventor/s: Alstom Australia Limited Peter Bernard Ketley Address for Service is: SHELSTON IP Margaret Street SYDNEY NSW 2000 CCN: 3710000352 Attorney Code: SW Telephone No: Facsimile No.

(02) 9777 1111 (02) 9241 4666 Invention Title: ENVIRONMENTAL ENCLOSURE Details of Associated Provisional Application No. 2004903954 dated 16 Jul 2004 The following statement is a full description of this invention, including the best method of performing it known to me/us:- File: 43196AUP00 500640143 1.DOC/5844 -1- ENVIRONMENTAL ENCLOSURE FIELD OF THE INVENTION The present invention relates to environmental enclosures and, in particular, discloses an improved form of environmental enclosure.

BACKGROUND OF THE INVENTION In many countries, variable signs are placed at the road side or the like so as to provide information for persons transiting the roadway or the like. The signs may, for example, include variable speed limits that are changed throughout the day or a variable message with the message being projected to the road user.

A number of problems exist with these signs. Regulations often require that they be formed from an aluminium box with a steel frame and be airtight. This can lead to a number of problems. For example, an airtight container exposed to the weather will likely undergo cyclic fluctuating temperature ranges which, in accordance with Boyle's law, will result in an oscillation in the pressures built up within the chamber. This oscillation of pressure is likely to weaken or destroy any seals that may have been put in place to form the airtight container. Upon destruction of the seals, water and or dust may ingress into the chamber thereby fouling the operation of electrical circuits within the chamber.

Further, the oscillating temperature can be magnified due to surface heating of surfaces thereby causing extensive fluctuations in temperature which can again affect the operation of electronics within the container.

SUMMARY OF THE INVENTION It is an object of the present invention to provide for an improved form of variable sign.

-2- In accordance with a first aspect of the present invention, there is provided a variable sign having an environmental enclosure, the enclosure including: an inner case for storing electronic portions of the sign, the inner case substantially sealed against the weather and having display portions on at least one surface thereof; an outer structural case substantially surrounding non-display portions of the inner case.

The outer structural case can be spaced apart from the inner case and preferably can include a series of venting holes for encouraging airflow between the outer case and the inner case. The inner case preferably can include a venting plug for venting moisture from the inner case whilst preventing the ingress of water and dust particles into the inner case. The inner case can be formed from aluminium. The outer case can be formed from steel.

In one embodiment, the sign can be a variable speed sign.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred forms of the present invention will now be described with reference to the accompanying drawings in which: Fig. 1 is a front plan view of a first embodiment according to the invention; Fig. 2 is a rear cut-away plan view of the embodiment of Fig. 1; Fig. 3 is a side sectional view taken along line 3-3 of Fig. 1; Fig. 4 is a top sectional view taken along line 4-4 of Fig. 1, however, with the doors swung into an open position; Fig. 5 is a rear plan view of a second embodiment according to the invention; Fig. 6 is a top sectional view taken along line 6-6 of Fig. 5 again with the doors swung into an open position; Fig. 7 is a sectional view illustrating the utilisation of selectively permeable pressure release valve incorporating a Gortex mesh screen; and -3- Figs. 8 to 10 are alternative display configurations for various sized versions of the preferred embodiments.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS In the preferred embodiment, there is provided a variable sign which has a number of significant advantages over the prior art. These advantages include better thermal characteristics in addition to a "breathable" container which simultaneously limits the fluctuations in internal pressures and also limits the ingress of dust or water.

In the preferred embodiment, there is provided an improved structure which includes an internal aluminium box having a 'breathing' plug with a Gortex (Trade Mark) mesh screen for providing for atmospheric equalisation whilst simultaneously eliminating the dust or water ingress. The average particle size of dust particles is typically about 50 to 70 Lm in diameter. The Gortex screen is ideal since the pore sizing of the mesh is approximately only 5 to 10 [tm therefore providing an impermeable barrier to most particulate impurities.

In the preferred embodiment, the variable road sign, in this case a speed limit sign, is formed having an outer steel casing and a inner aluminium box. The aluminium box includes a breathing plug which can be a plug having a Gortex screen filter. The Gortex plug acts to allow "breathing" of the box so as to provide for pressure equalisation between the inner box and the outer casing which is maintained at ambient temperature and pressure. In the preferred embodiments, the plug has an air flow capacity of about 1 litre/minute or greater.

Further, the outer steel box acts as a insulating barrier so that the internal aluminium box is kept cooler in summer and warmer in winter. Further, the outer steel box acts to allow for effective venting of air around the inner aluminium box.

-4- A series of prototypes have been constructed and will now be discussed with reference to the accompanying drawings. A first example is illustrated in Figs. 1 to 4.

Referring initially to Fig. 1, the front surface 110 of the preferred embodiment includes a series of drilled holes 111 through which light from corresponding LEDs is emitted. Behind the front surface is mounted a clear transparent sheet of a plastics material such as Perspex or polycarbonate. The LEDs are in turn mounted to a circuit board within the inner box. In this embodiment the front surface includes holes and LEDs for the operation of a variable speed sign displaying variable speed information.

Fig. 2 illustrates the back of the preferred embodiment partly in cut away. The back consists of an outer 105, 106 and inner 107, 108 series of swing doors. The arrangement described has two doors hinged on each side. Other arrangements could consist of one door only or another number of doors.

As shown in the side sectional view of Fig. 3, The arrangement of the preferred embodiment includes an outer structure 102 and an inner structure 103 each having access doors. Ventilation is allowed along cavity 103 with the cavity 103 being substantially sealed.

As shown in Fig. 2 and Fig. 4, in this embodiment, the outer structure has a pair of doors 105 and 106, and the inner structure has a pair of doors 107 and 108 show in Fig. 4. The outer structure 101 and doors are formed from steel and the inner box structure 103 is formed from marine grade aluminium. The structural steel is hot dip galvanised before powder coating.

The bottom portion of the inner box 103 includes a breathable plug 109 having a Gortex surface through which air is allowed to ingress and egress from the inner box 103 whilst water and dust are kept outside the inner box. Turning to Fig. 7, there is illustrated a sectional view showing the plug 109 with a Gortex film attached to the inner surface of the door 108. The sectional view of Fig. 3 shows a substantially sealed chamber 103 for holding the control electronics. Natural airflow is allowed along cavity 102 so as to keep the chamber at a reduced temperature. The breathable Gortex plug between the outer structure 102 and the inner structure 103 acts as a pressure equaliser which counteracts the natural daily pressure fluctuations of the inner chamber 103 containing the electronic components of the sign. As the chamber 102 is otherwise sealed from the external environment, dust and water ingress into the inner structure is minimised therefore significantly decreasing the risk of fouling the electronic components.

A second embodiment shown in Figs. 5 and 6 illustrates a slightly modified embodiment 200. In this arrangement having different dimensions, a single rear outer door 205 only is provided in the outer structure for access to the inner door 207..

Similarly, a single door 207 is provided in the inner structure 203 for access to the electronic components contained therein. A breathable plug 209 is also again included for pressure communication between the inner outer structure. Figures 8 to 11 illustrate various alternative display configurations for different sized embodiments of the preferred variable road sign.

By utilising an outer steel structure and an inner aluminium structure the embodiments of the invention have a number of significant advantages including better thermal characteristics. The utilisation of a breathing plug aids and abets these characteristics. Of course, various modifications in the size, shape and location of the breathing plug are possible. In the preferred embodiments, due to the sealed casing and the particle protection provided by the mesh screen, the inner case can be rated against the International Protection rating covered in Australian Standard AS 1939 to a standard of at least 1P65, whereas the outer case can be a much more relaxed rating.

-6- The forgoing described preferred forms of the invention. Modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the invention.

Claims (10)

1. 2. An electronic sign as claimed in claim I wherein said valve includes a mesh screen for providing said selective permeability.
2. 3. An electronic sign according to claim 2 wherein said mesh screen is formed from the material know by the trade mark Goretex.
3. 4. An electronic sign as claimed in any one of the preceding claims wherein said outer case includes a plurality of venting holes for permitting ambient air flow through said outer chamber. An electronic sign according to any one of the preceding claims wherein said inner case provides a higher level of environmental protection than said outer case.
4. 6. An electronic sign as claimed in any one of the preceding claims wherein said display surface is substantially planar, said inner case having a substantially planar rear wall parallel to and spaced apart from said display surface to define said inner chamber, said inner access door being substantially planar and forming at least part of said rear wall of said inner case.
5. 7. An electronic sign as claimed in claim 6 wherein said outer case includes a substantially planar rear wall parallel to and spaced from said rear wall of said inner case -8- to define said outer chamber, said outer access door being substantially planar and _forming at least part of said rear wall of said outer case. O 8. An electronic sign according to any one of the preceding claims wherein said display surface of said inner case includes: a plurality of display apertures permitting visual access to said inner chamber; and a transparent cover sheet overlying said display surface to seal said inner case. N 9. An electronic sign according to claim 8 wherein said electronic components Oinclude a plurality of variable light sources, each said light source aligned with a N 10 respective one of said display apertures. An electronic sign according to claim 9 wherein said light sources are light emitting diodes.
6. 11. An electronic sign according to any one of the preceding claims wherein said inner case is formed from aluminium.
7. 12. An electronic sign according to any one of the preceding claims wherein said outer case is formed from steel.
8. 13. An electronic sign according to any one of claims 8 to 12 wherein said transparent sheet is formed from a plastics material.
9. 14. An electronic sign according to any one of the preceding claims wherein said sign is a variable road sign. An electronic sign according to any one of the preceding claims wherein said sign is a variable speed sign.
10. 16. An electronic sign substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.