Rostrum and support structure for a rostrum

Abstract

In a first aspect, a rostrum support structure for a rostrum comprises a pair of frame units which are inclined towards one another, extending from floor contacting portions to rostrum support points, truss members being provided extending downwardly and inwardly from the first frame members towards a linking member or towards the other frame member, to provide a triangulated structure. In a second aspect, a rostrum structure comprises a first rostrum unit and a second rostrum unit, a latch being provided for fixing the second rostrum unit with respect to the first rostrum unit in an extended position, the latch comprising a movable member mounted on one of the first and second rostrum units and a latch surface mounted on the other of the first and second rostrum units, the movable member being movable into and out of engagement with the latch surface, preferably by rotation, in a direction parallel to the planes of the decks and substantially normal to the retraction direction.

1 . A support structure for a rostrum, comprising:
 a first frame unit and at least a second frame unit, retractable into the first frame unit,   each frame unit comprising:
 a first frame member, extending from a floor contacting part to a first rostrum support point and a first truss extending from the first frame member, 
 a second frame member, extending from a floor contacting part to a second rostrum support point and a second truss extending from the second frame member, 
   wherein, in each frame unit:   (c) there is a linking member, connecting the first and second frame members and first and second trusses, at points displaced from the first and second rostrum support points; or   (d) the first and second trusses are connected to the second and first frame members respectively, at points displaced from the first and second rostrum support points.   
     
     
         2 . A rostrum support structure according to  claim 1 , wherein the first and second frame members and the first and second trusses lie in a first plane, there being a linking member located in a plane displaced from the first plane. 
     
     
         3 . A rostrum support structure according to  claim 1 , wherein the first and second rostrum support points are located closer to one another than the respective floor contacting parts of the first frame member and second frame member. 
     
     
         4 . A rostrum support structure according to  claim 1 , wherein, in a respective frame unit, the first and second trusses contact the linking member at points which are displaced from one another. 
     
     
         5 . A rostrum support structure according to  claim 4 , wherein, in different frame units, the first and second trusses contact the linking member at different points. 
     
     
         6 . A rostrum support structure according to  claim 1 , wherein the first frame member, first truss and linking member define a first triangulated structure and the second frame member, second truss and linking member form a second triangulated structure. 
     
     
         7 . A rostrum, comprising a plurality of decks supported by a plurality of rostrum support structures according to  claim 1 . 
     
     
         8 . A rostrum structure, comprising:
 a first rostrum unit and at least a second rostrum unit, wherein the second rostrum unit is movable in a retraction direction between an extended position and a position in which it is retracted into the first rostrum unit, each rostrum unit having a deck;   a latch, for fixing the second rostrum unit with respect to the first rostrum unit in the extended position, the latch comprising a movable member, mounted on one of the first and second rostrum units, and a latch surface mounted on the other of the first and second rostrum units, with   which the movable member engages to fix the second rostrum unit with respect to the first rostrum unit in the extended position, the movable member being movable into and out of engagement with the latch surface in a direction parallel to the planes of the decks and substantially normal to the retraction direction.   
     
     
         9 . A rostrum structure according to  claim 8 , wherein the movable member is rotatably mounted. 
     
     
         10 . A rostrum structure according to  claim 8 , wherein the movable member is biased into a position in which it engages with a latch surface. 
     
     
         11 . A rostrum structure according to  claim 8 , wherein the movable member is biased into engagement with the latching surface by a weight. 
     
     
         12 . A rostrum structure according to  claim 8 , wherein movement in both the retraction direction and extending direction is prevented by engagement of the movable member with the latch surface. 
     
     
         13 . A rostrum structure according to  claim 12 , further comprising a second latch surface opposed to the first latching surface, the movable member being received between the first and second latch surfaces. 
     
     
         14 . A rostrum structure according to  claim 8 , wherein a cam surface is provided on whichever of the first and second rostrum units comprises the latch surface, the cam surface being configured so that, as the movable member, moving with the respective rostrum unit, approaches the cam surface, it moves over the cam surface against biasing means, the movable member moving into engagement with the latch surface under the influence of the biasing means, when it comes out of engagement with the cam surface. 
     
     
         15 . A rostrum structure according to  claim 8 , wherein means are provided for moving a respective movable member out of engagement with a latch surface. 
     
     
         16 . A rostrum structure according to  claim 8 , comprising a first, upper rostrum unit, a second, intermediate rostrum unit and a third, lower rostrum unit, a movable member being provided on one of the first and second rostrum units and a latch surface being provided on the other of the first and second rostrum units, an unlatching cam surface being provided on the third rostrum unit, arranged so that, as the third rostrum unit is moved into a retracted position with respect to the second rostrum unit, the unlatching cam surface engages the movable member so that it moves out of engagement with the latch surface. 
     
     
         17 - 18 . (canceled)