AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Innovation Patent Applicant: Roland Clements Invention Title: Security Screens The following statement is a full description of this invention, including the best method for performing it known to me: - 2 Security screens This invention relates to improvements in relation to security screens especially security screens which are 5 attachable to the exterior of windows of vehicles and can be locked thereon to reduce the likelihood of vandalism. Earth moving machines and vehicles are traditionally too bulky to move around and therefore tend to be left on 1o construction sites overnight. The damage caused to such vehicles by vandals is a serious concern and the glass windows of such vehicles appear to be an attractive target to vandals. 15 To prevent damage to the windows of such vehicles when left overnight there have been proposed to place security screens over the exterior of the windows and lock those screens in place by use of locking means such as padlocks. The security screens substantially reduce the opportunity 20 for a vandal to break the window and are often designed to define an open mesh. Although the screens are usually removed by the operator before operating the vehicle it is common practice for operators to simply leave the security screens locked in place. 25 The cabs of earth moving vehicles usually have a rear window which is designed as a safety exit. Because vehicles such as this operate on sites with adverse soil and sloping conditions accidents are known to occur and 30 many accidents occur with the vehicle toppling forwards, jamming the doors, leaving the only method of escape through the rear window. The cabs of such vehicles often include a hammer or other device to enable the operator to, in an emergency, break the window to affect escape. 35 Unfortunately however, if the rear window is covered by a security screen which remains locked thereon by use of 17570441 (GHMatters) 25/09/09 - 3 padlocks, breaking of the window from the inside does not provide a ready access for escape. There have thus been a number of accidents where operators have been killed because it was impossible to escape from the cab due to 5 the presence of security screens locked to the exterior of the windows. These issues were dealt with in Australian Innovation Patent No. 2008100493, details of which are now 10 incorporated by reference. In that patent, there was disclosure of attaching a security screen to a base structure that would be secured to the vehicle. The security screen was secured to the base structure by use of padlocks that engaged lugs that extended from the base 15 structure through the screen. A latch was provided on the inside of the screen that, when released, facilitated separation of the lugs from one side or end of the base structure so that, in the event of emergency, and an occupant of the cabin of the vehicle wished to remove the 20 screen it would be possible to release the screen from the inside. Whilst the use of padlocks provided satisfactory security against vandalism and the latching mechanism allowed an 25 operator in an emergency to break the glass of the vehicle, pull a release wire and push out the screen, there was also a requirement that every time an operator used the vehicle, the operator was required to unlock and remove the padlocks so that if an operator was rendered 30 unconscious during an accident, a rescuer can, from outside the vehicle, remove the guard screen by lifting it from its base. Unfortunately, it is human nature for people to forget or fail to unlock and remove the padlocks and thus the arrangement described in the innovation 35 patent still left a problem that, after an accident, an unconscious, disoriented or dazed operator could be trapped in the vehicle without the ability to release the 17570441 (GHMatters) 25/09/09 - 4 screen from the inside and rescuers would be unable to remove the guard screen to gain access to the operator because of the need to remove the padlocks; the keys of which were often kept inside the machine cabin. 5 It is these issues that have brought about the invention of this application. According to one aspect of the present invention, there is 10 provided a security screen detachably secured to a support structure, the support structure having at least one latch that engages the screen and the screen having at least one lug that engages the support structure, an electrical actuator on the support structure adapted to assume a 15 locked position in which it engages the lug or an unlocked position in which the lug can be separated from the support structure, the latch being releasable from the inside of the screen. 20 Preferably, the support structure is adapted to be secured to the exterior of the window of a vehicle, the electrical actuator being coupled to the electrical circuit of the vehicle so that when the vehicle's ignition is switched on the actuator is in the unlocked position. 25 Brief Description of the Drawings Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: 30 Figures 1 to 3 illustrate embodiments taken from Innovation Patent No. 2008100493; Figure 4 is a rear perspective view of a security screen 35 in accordance with an embodiment of this application; Figure 5 is a front perspective view of the screen; 17570441 (GHMatters) 25/09/09 - 5 Figure 6 is a side elevational view of the security screen; Figure 7 is a plan view of the security screen; 5 Figure 8 is a rear elevational view of the security screen; Figure 9 is a cross-sectional view taken along the lines 10 AA of Figure 8; and Figure 10 is an enlarged view of the detail B in Figure 9. The security screen assembly that is the subject of this 15 application is an improvement over the security screen described in Innovation Patent No. 2008100493, the disclosure of which is incorporated herein by reference. Figures 1 to 3 are taken from the innovation patent and 20 illustrate a removable security screen 20 made of metal or very strong plastics comprising a rectangular frame 21 defining a grid of small open apertures 22. The screen is designed to be secured to top and bottom mounting structures 9, 50, the bottom mounting structure 50 having 25 projecting lugs 11, 12 and the top mounting structure 9 having projecting lugs 13, 14. The mounting structures may be secured by screws, bolts or welded to the top and bottom of the periphery of the window of a vehicle. The lugs 11 to 14 extend upwardly at spaced intervals adjacent 30 the corners of the window. Adjacent each corner of the top of the screen 20 are narrow slits 25, 26 though which the lugs 13, 14 extend. The base of the screen has rectangular cut outs 23, 24 35 which accommodate right angled brackets 28, 29 which are secured to the screen to project upwardly from the screen to abut the lugs 11, 12 of the mounting structure. The 17570441 (GHMatters) 25/09/09 - 6 lugs 11, 12 and brackets 28, 29 have coaxial holes 27 which accommodate a padlock 30. At the top of the screen 20, the lugs 13, 14 have a V-shaped profile or extend upwardly so that they extend through the slits 25, 26 in 5 the face of the screen which is lowered onto the incline of the V so the screen can only be removed by first moving the screen 20 up the V and then pulling it away from the lugs 13, 14. This movement can only be effected by release of the padlocks 30 which are attached to the lugs 10 11, 12 at the base of the screen 20. This is one means for holding a security screen onto the window of a vehicle and causes no problem if the operator of the vehicle is diligent enough to remove the screen 15 every time the vehicle is used. However, because the screen has a perforated structure, the vehicle can still be driven with the screen in place and there has been a tendency for operators to leave the screens locked in position which means escape from the interior of the 20 vehicle through the glass becomes impossible because of the fixed location of the screen 20 to the window frame. In Figures 1 and 2, the lugs 13, 14 at the top of the screen 20 are designed to be held to the mounting 25 structure 10 of a latch assembly 80 (Figure 2), the release of which is effected by a pull on a release wire 40 to allow the lug 13, 14 to become detached from the mounting structure 10 and allows the screen 20 to be capable of pivoting outwardly about the lugs 11, 12 at the 30 bottom of the screen 20 by pressure from within. The latch assembly 80 is discussed in Innovation Patent No. 2008100493 As shown in Figures 2 and 3, a single lug 60 locates the 35 base of the screen 20. The lug projects through a slot 61 in the rectangular mounting plate 50 which has laterally extending mounting points 51, 52 that are screwed or 17570441 (GHMatters) 25/09/09 - 7 bolted to the frame of the vehicle. A spring loaded wire clip 65 extends across the lug 60 to be forced into a groove 62 in one side of the lug to thus prevent the lug from being pulled free of the assembly. The spring is 5 located at either end about mounting points 63, 64. When an occupant wishes to force the screen open, the upper lugs are released as described above. When the upper lugs 13, 14 are released, a small force at the top of screen 20 creates a high leverage to lug 60 which overcomes the 10 tension of the spring. The spring 65 escapes from the groove 62 in the lug 60 and allows the lower lug 60 to be released from the mounting plate 50 allowing the screen to be released and fall or be pushed completely clear of the vehicle. 1s Figure 3 shows the lug 60 in greater detail. The lug 60 has a front flange 71 which abuts the front face of the plate 50. The lower side of the lug 60 has a V-shaped cut-out 72 which engages a similarly shaped projection 73 20 on the edge of the slot 61 in the plate 50. The rear of the plate 50 also has an angled support flange 75 which engages the end and base of the lug 60 to assure that the lug 60 is firmly and fixedly located within the slot 61 in the plate 60. 25 Thus in the event that the screens remained locked to the exterior of the vehicle and an operator becomes trapped in the vehicle, the operator can break the window, release the latches to disengage the lugs to allow the screen to 30 be pushed open thus allowing release of the occupant. The embodiments described above, disclosed in Innovation Patent No. 2008100493, work entirely satisfactorily if the users of the ancillary equipment follow the operational 35 procedure, namely, to remove the padlocks when the vehicle is in use. Removal of the padlocks means it is a simple exercise to remove the screens from the exterior of the 17570441 (GHMatters) 25/09109 - 8 vehicle. Thus if the vehicle is involved in an accident and the operator becomes trapped in the vehicle, outside parties can obtain access through the windscreen of the vehicle by first removing the security screen and then 5 breaking the glass. The problem is, however, that human nature is such that people tend to be lazy and fail to remove the padlocks. If the vehicle is used with the padlocks in place then access from the exterior is impossible unless a key can be found to unlock the 10 padlocks. It is this problem that is solved by the embodiment shown in Figures 4 to 10. This embodiment concerns the design of the lower mounting plate 50 which, like the embodiment 15 shown in Figure 2, comprises a rectangular plate with mounting lugs 51, 52 on either side. Unlike the embodiment shown in Figure 3, where the single lug 60 is held to the plate 50 through a spring 65 and the screen 20 is secured to this lug via padlock 30, in this embodiment 20 a single lug 100 is integrally secured to the centre of the screen 20 and extends rearwardly through the plate 50 to locate within the gap defined by two right angled brackets 101, 102 that are secured to the plate 50 to have co-axial apertures. An electrically actuated actuator 110 25 is positioned on the inside of the mounting plate 50 and includes a cylindrical pin 111 that can be urged outwardly to engage through the apertures in the brackets 101, 102 and a central slot 115 in the rearwardly projecting lug 100. A spring clip 120 of C-shaped profile is attached to 30 the interior of the plate with an end portion 121 wrapped around two vertically spaced pins 122, 123. The spring has an angled, laterally extending arm 125 that, as shown in Figure 9, is arranged to be urged into the base of a groove 126 with an inclined wall that forms a ramp 127 in 35 the rearwardly projecting lug 100 on the screen. 17570441 (GHMatters) 25/09/09 - 9 With the pin 111 in the retracted position, it is possible for a rescuer from the outside of the vehicle to lift the screen from the base causing the spring arm 125 to ride up over the ramp 127 to release the lug 160 from the base 5 plate 50. Once the base of the screen has been released, it is then possible to lift the screen off the upper lugs 13, 14. When the vehicle is not in use, the actuator 110 causes a 10 pin 111 to project outwardly into the locked position where it extends through the apertures in the brackets and the slot 115 in the lug 100. In this manner, it is impossible to pull the base of the screen 20 away from the support 50 and the location of the lugs 13, 14 in the 15 upper slots means it is not possible to remove the screen from the exterior. It is, however, possible to remove the screen 20 from the inside even when the pin 111 is in the extended and locked configuration by releasing the upper lugs 13, 14 in the same manner as disclosed in my earlier 20 innovation patent, namely by a pull on the release cord or wire 40. The actuator 110 is coupled to the electrical circuitry of the vehicle. The control circuitry for the actuator is 25 interlocked with the vehicle ignition so that when the ignition is switched on, the actuator is moved to the open unlocked position. The actuator remains in the open unlocked position until manually instructed to return to the locked position. This is initiated by the operator 30 via an activate button installed inside the cabin of the vehicle. The activate button is interlocked with the machine ignition system such that while the machine is operating, 35 with the ignition on, the actuator cannot be activated to move into the locked position. It is only when the ignition is turned off that the activate button can 17570441 (GHMatters) 25/09/09 - 10 initiate the electric actuator to move to the locked position. The electric actuator contains limit switches in the open 5 and closed position which are interfaced with the vehicle safety warning system to sound an audible warning if the limit switches do not detect that the actuator has moved to the appropriate open or closed positions. Green and red indicator lights are positioned within the cabin of 10 the vehicle to indicate which position the actuator has moved to thus providing the operator with a visual system of indication of the actuator position. It is important that the unlocking of the actuator is 15 automatic when the ignition system is switched on. It is also important that the locking process, that is moving the actuator to the locked position, is manually energised by the operator. This can only occur when the ignition is switched off. A further feature is to interlock the 20 electrics of the actuator with the engine starting circuit so that it becomes impossible to start the engine if the screen is in the locked state or if the system fails to activate. 17570441 (GHMatters) 25/09/09