Outreach screen

Abstract

A pair of spaced upright masts each support at opposite sides two opposed guides providing respective tracks for travellers. The travellers are independently vertically moveable along their respective tracks by cables wound around motor-driven pulleys at their upper ends. A gas strut inside the upper end portion of each track is engaged by the corresponding traveller when the associated screen approaches and passes through a horizontal plane. The compressive resistance offered by the strut when engaged by the traveller increases the load on the traveller. This increase in load compensates for a reduction in the downward thrust exerted on the traveller by the weight of the associated screen as it passes through the horizontal plane. Instability in the positioning of the screen is thus avoided so that the two screens can be stably positioned in parallel sloping but spaced planes. Thus the area protected from above by the screens can be safely maximized.

1 - 10 . (canceled)  
   
   
       11 . An up-and-over screen assembly having at least one upright track for a traveller, a stably-supported screen fixed at one side to the traveller which is moveable up and down the track respectively to raise and lower the screen through ninety degrees or more between a lowered upright position alongside the track and a raised position at which the screen extends transversely from the track to shield a chosen ground area adjacent the track from a particular ambient condition, at least two rigid links rotating at their ends about parallel horizontal first and second pivotal axes to guide movement of the screen between its raised and lowered positions, the first pivotal axis being fixed in relation to the upper-end of the track and the second pivotal axis being fixed in relation to the screen, and, a device positionally fixed in relation to the screen assembly and for absorbing unwanted forces which would otherwise act on the traveller to cause the screen to become unstable when raised through approximately 90 degrees or more.  
   
   
       12 . An assembly as claimed in  claim 11 , in which the device provides a resilient bias.  
   
   
       13 . A screen assembly as claimed in  claim 12 , in which the resilient bias is adjustable and provided by a gas strut.  
   
   
       14 . An assembly as claimed in  claim 13 , in which the gas strut is associated with a track containing a carriage having a part which extends laterally from the track to provide the lower end of a traveller which is pivotally attached to a lower part of the screen.  
   
   
       15 . An assembly as claimed in  claim 11 , in which a drive-transmission mechanism is mounted between a drive source and a pulley controlling the tension of an inextensible cable loop which controls the position of the traveller on the track, the drive transmission mechanism having a drive ratio which is sufficiently large to prevent the reversal of drive through it so that unwanted forces which might otherwise render the screen unstable when in its elevated position are absorbed.  
   
   
       16 . An assembly as claimed in  claim 11 , in which an electric motor is used to move the traveller up and down the track.  
   
   
       17 . An assembly as claimed in  claim 11 , in which a latch mechanism having one component on the screen and a second component fixed in relation to the track is engaged when the screen is moved towards an upright stowage position alongside the track, the latch mechanism being effective to positively locate an upper end-portion of the screen at a position alongside the track, and the pivotal axis at the upper-end of the link associated with the screen being positioned nearer the track with respect to the pivotal axis at the lower end of the link to ensure that the link slopes downwardly slightly away from the track when the screen is in its vertical stowage position.  
   
   
       18 . An assembly as claimed in  claim 17 , in which two screens are respectively provided at opposite sides of spaced parallel vertical masts and are independently moveable by drives provided on a structure interconnecting the upper-ends of the masts, the masts providing at their upper-ends respective horizontal coaxial pivot axes lying in the same plane as the masts and on each of which are pivoted the upper-ends of a pair of rigid links which extend divergently downwardly to respective screens.  
   
   
       19 . An assembly as claimed in  claim 11 , in which the screen is supported by travellers respectively arranged in a line of spaced upright parallel tracks mounted on a wall, each traveller been provided with its own device and being vertically positioned on its track by a cable, a drive common to the cables being used to move the travellers in synchronism along their respective tracks.  
   
   
       20 . An assembly as claimed in  claim 11 , in which the track is provided by the interior of a vertically slotted guide attached to one side of a pole and a second guide providing a second track is attached to the opposite side of the pole, each track having its own traveller fixed to one edge of a respective screen.