AU737997B3

AU737997B3 - Improvements in traffic signals

Info

Publication number: AU737997B3
Application number: AU71438/00A
Authority: AU
Inventors: Keith J Aldrige; Raj N Bhat
Original assignee: ALDRIGE TRAFFIC SYSTEMS Pty LT
Current assignee: ALDRIDGE TRAFFIC SYSTEMS Pty Ltd
Priority date: 2000-10-31
Filing date: 2000-10-31
Publication date: 2001-09-06
Anticipated expiration: 2006-10-31
Also published as: NZ510592A

Description

P00012 Regulation 3.2 Revised 2/98

AUSTRALIA

Patents Act, 1990

ORIGINAL

COMPLETE SPECIFICATION PETTY PATENT TO BE COMPLETED BY THE APPLICANT NAME OF APPLICANT: ACTUAL INVENTOR: ADDRESS FOR SERVICE: INVENTION TITLE: DETAILS OF ASSOCIATED PROVISIONAL APPLICATION NO(S): ALDRIDGE TRAFFIC SYSTEMS PTY

LIMITED

(ACN 001 678 557) RAJ N BHAT and KEITH J ALDRIDGE Peter Maxwell Associates Level 6 Pitt Street SYDNEY NSW 2000 IMPROVEMENTS IN TRAFFIC SIGNALS

NIL

The following statement is a full description of this invention including the best method of performing it known to me:- IP Australia Documents received on: U) 3 1 OC T 2000 Batch No: The present invention relates to improvements in traffic signals and, in particular, to a non-reflective traffic signal in which illumination is provided by a plurality of light emitting diodes (LED's).

LED traffic signals are a fairly recent development that are gradually replacing the more traditional globe traffic signals. Although the use of LED's has many advantages over the use of globes in traffic signals, some problems remain. For instance, LED traffic signals utilizing a clear front lens may result in a "veiling reflection" effect, causing reflected sunlight to be white. The reflected white light could, in some circumstances, be of such an intensity that it appears as an undefined signal causing confusion to drivers approaching the traffic signal. Furthermore, the reflected white light will add to the aspect signal when the aspect (either red, amber or green) is on, causing desaturation of the colour of the aspect signal.

Therefore, the effect of "veiling reflection" on LED traffic signals can cause the colour of the signal to move outside the allowable range of colour for that signal. To some extent, "veiling reflection" can be prevented or made less likely by the use of a coloured front lens (or cover) designed to maintain the colour of the signal within the allowable range under the conditions presently used in the art for measuring "sun-phantom" intensity.

However, the use of coloured front lenses may lead to the creation of a "sun phantom" effect, because any reflected sunlight from the lens will be coloured and so the traffic signal will appear to be on when it is off.

One of the major causes of reflected sunlight from an LED traffic signal is the LED printed circuit board itself, from the anterior (or front) side of which project a plurality of generally evenly distributed LED's and which also supports reflective elements such as resistors, transistors, current diodes and printing.

Each of these elements of the board are, in themselves, reflective to a minor 3/07/01 3 extent, but their combined effect is to create a generally reflective surface, the undesirable consequences of which are as described above.

It is an object of the present invention to overcome, or at least substantially ameliorate, the disadvantages and shortcomings of the prior art.

According to the present invention, there is provided a traffic signal in which illumination is provided by a plurality of light emitting diodes projecting from an anterior side of a printed circuit board on which the diodes are mounted, characterised in that the traffic signal includes a non-light reflective mask covering the anterior side of the board and having a plurality of apertures at locations corresponding to the location of the plurality of light emitting diodes for allowing the diodes to project through the apertures but masking the remainder of the anterior side of the board to prevent reflection of sunlight therefrom, wherein the non-light reflective mask has a matt black colour.

It is preferred that the mask is made of a polypropylene copolymer.

In order that the invention may be readily understood and put into practical effect, reference will be made to the accompanying drawings, in which: Fig 1 is an exploded perspective view of a traffic signal according to a preferred embodiment of the present invention, Fig 1A is an enlarged view of detail A shown in Fig 1, Fig 2 is a front elevational view of the non-light reflective mask used in the traffic signal of Fig 1, and Fig 3 is a cross sectional view through a cut-away portion of the traffic signal shown in Fig 1.

The traffic signal 10 shown in Fig 1 has a board assembly 12, a nonlight reflective mask 14, and a plurality of screws 16 for securing the correctly positioned mask 14 to the board assembly 12.

The board assembly 12 consists of a printed circuit board 18 mounted to a circumferentially surrounding bracket 20 from which extend mounting members 22 for locating the traffic signal 10 to a traffic signal lantern box or the like enclosure.

The posterior (or rear) side of the board 18 has mounted thereto the essential electronic componentry (not shown) for operating the plurality of light emitting diodes 24 which project from the anterior side of the board 18 in a generally even distribution. There are a plurality of reflective elements 26, such as transistors, resistors and current diodes, supported on the anterior side of the board 18 which, together with any white printing that might be displayed on the anterior side of the board 18, combine to create a generally reflective surface.

The mask 14, which, in this embodiment, has a matt black colour and is made of a polypropylene copolymer, has a plurality of apertures 28 at locations corresponding to the location of the plurality of light emitting diodes 24, and when the mask 14 is being correctly positioned over the anterior side of the board 18, each of the light emitting diodes 24 pass through respective apertures 28 of the masks 14 so that they project through the apertures 28, but the remainder of the anterior side of the board 18 is masked or covered to prevent reflection of sunlight therefrom. Once correctly positioned, the mask 14 is secured to the board assembly 12 by the application of screws 16 through overlying holes 30, 32 in respective peripheral regions of the mask 14 and board 18.

The traffic signal of the present invention has been found to prevent the creation of "sun phantom" effect when coloured front lenses (or covers) are used. For instance, in a test conducted by a NATA accredited laboratory, the "sun phantom" intensity measurements (in units of candelas of a traffic signal having a green LED signal with two samples of green coloured front lenses were 38.0 cd and 47.6 cd respectively, both of which measurements represent a fail mark in relation to accepted standards in the art for avoidance of "sun phantom". When tests were conducted under the same conditions but with the use of a mask as described above as part of the traffic signal, the "sun phantom" intensity measurements of the traffic signal were 15.1 cd and 19.0 cd respectively, both of which measurements represent a pass mark in relation to the aforementioned standards. In fact, the reduction in "sun phantom" intensity for the green signal is in the order of about 60% when the traffic signal of the present invention is used as compared to prior art LED traffic signals.

A particularly preferred polypropylene copolymer is that marketed under the name HOSTALEN PPT 2052 by Hoechst.

Various modifications may be made in details of design and construction without departing from the scope and ambit of the invention.

Claims

1. A traffic signal in which illumination is provided by a plurality of light emitting diodes projecting from an anterior side of a printed circuit board on which the diodes are mounted, characterised in that the traffic signal includes a non-lightreflective mask covering the anterior side of the board and having a plurality of apertures at locations corresponding to the location of the plurality of light emitting diodes for allowing the diodes to project through the apertures but masking the remainder of the anterior side of the board to prevent reflection of sunlight therefrom, wherein the non-light reflective mask has a matt black colour.

2. The traffic signal of claim 1 wherein the mask is made of a polypropylene copolymer. Dated this 3rd day of July, 2001 Aldridge Traffic Systems Pty Limited Patent Attorneys for the Applicant PETER MAXWELL ASSOCIATES