Abstract:
Fire can spread extremely quickly within structures. To prevent this, fire doors or fire shutters are usually installed. However, security aspects of such doors or shutters are not renown. An attempt to alleviate this problem may be provided by an insulated fire panel shutter including a guide, adapted to receive a shutter and having one or more retractable members moveable between a retracted and extended position; a shutter, moveable between an open and closed position and formed from a plurality of panels each of which is moveable between a stowed and deployed position; their arrangement being such that as the guide receives the shutter during shutter closure, the panel arrangement alters from a stowed side by side relationship to a deployed stacked end to end relationship.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an insulated fire panel shutter, in particular to one which can also serve as a security shutter. 
       BACKGROUND ART KNOWN TO THE APPLICANT 
       [0002]    Fire can spread extremely quickly with the result that it can rapidly get out of control. In order to minimize this risk in structures, it is desirable that openings such as doors or windows in buildings; shafts in mines; and passageways in modes of transport used on land or sea, are provided with ways for preventing fire from passing through them and spreading to other areas. Fire doors or shutters tend to be used (e.g. SG 200905226-7) and these must be capable of resisting the effects of a fire for a period of time often stipulated by legislative regulations with the result that individuals can either safely escape the fire or if trapped, are relatively safe until the fire is dealt with. Nevertheless, enormous heat can be generated by such fires and heat transfer across the face of a fire door and in particular a fire shutter is possible given enough time. When subjected to the effects of fire, fire shutters can turn red hot and emit radiated heat to the other side of the shutter. In some cases, this radiated heat may be sufficient to cause material in the fire free area to eventually ignite and permit the fire to spread further. In addition, so-called ‘fire doors’ or ‘fire shutters’ tend not to be viewed as security doors or shutters. Accordingly, a need still exists to provide a fire shutter which meets both the requirements of preventing the initial spread of the fire and resisting heat transfer with the passage of time during a fire i.e. to act as a better heat insulator. In addition, a need also exists for a fire shutter which can also serve as a security shutter. 
       SUMMARY OF THE INVENTION 
       [0003]    With the foregoing in view, the invention in one aspect resides broadly in an insulated fire panel shutter adapted to close off an area including: 
         [0004]    a guide, adapted to receive a shutter and having one or more retractable members moveable between a retracted and extended position; and 
         [0005]    a shutter, moveable between an open and closed position and formed from a plurality of panels each of which is moveable between a stowed and deployed position; 
         [0006]    their arrangement being such that as the guide receives the shutter during shutter closure, the panel arrangement alters from a stowed side by side relationship to a deployed stacked end to end relationship. 
         [0007]    Preferably the shutter is adapted to bias the one or more of the retractable members into the retracted position as the shutter moves from its open to its closed position and when in the closed position, the shutter no longer biases the one or more retractable members enabling the one or more retractable members to move from the retracted to the extended position, enabling the guide to engage the front and rear face of the or each panel. 
         [0008]    The retractable members are moveable between retracted and extended positions because they are fitted with a plurality of biasing hinges. 
         [0009]    One retractable member may in principle be sufficient as in its extended position, it will narrow the clearance which exists between the guide and the thickness of the or each panel making up the shutter when the shutter is in its closed position. However, having a pair of opposed retractable members adapted to move from a retracted to expanded position to narrow the clearance from opposed sides of the guide would be more advantageous. This is because if only one retractable member was used, it would have to be able to urge the face of the panel it was not coming into contact with against the rest of the guide to narrow the clearance existing either side of the shutter, and given the mass of the or each panel the urging force would have to be very great. It would be better if the movement to narrow the clearance gap between the guide and either side of the shutter were carried out by moving retractable members towards opposed faces of the shutter. 
         [0010]    Typically, shutters which include more than one shutter panel are usually designed so that each shutter panel is pivotally connected to another. In the present invention however, if multiple shutter panels are employed, it is preferable if at least some of the panels are not pivotally connected to each other. It is even more preferable if none of the panels were pivotally connected. Furthermore, conventional pivotally connected shutters tend only to be stowable in one of two manners. 
         [0011]    Either the slats (or panels) of the shutter are rotatably stowed about an axle or translationally stowed along a straight or curved guide when the shutter is in the open position. If the guide is straight, the movement of the panels will be a purely translational movement. If the guide is curved the movement will involve both translation and either a degree of rotation or revolution. In respect of the present invention however preferably, during movement of the shutter, at least one panel undergoes translational movement in two directions, the final position of the panel being parallel with but within a different plane to the first. 
         [0012]    Such an arrangement would allow the panel arrangement to change from a side by side relationship in a ‘door open’ position to a stacked top to bottom relationship in the ‘door closed’ position during deployment of the panels to form the shutter thus closing off the area. 
         [0013]    Such a form of movement would be advantageous over for example, conventional translational stowing as it is likely to involve space (if not volume) saving especially if the side by side arrangement is one where the front face of one panel faces the rear face of another and more than one panel undergoes the same type of movement resulting in the stacking of panels. 
         [0014]    Preferably, the insulated fire panel shutter is provided with means adapted to enable at least some or each of the panels to be stowed in a parallel overlying front face to rear face facing relationship when the shutter is in the open position. 
         [0015]    This is preferably achieved by a pair of opposed sloping (relative to the horizontal) shelves. The slope may be friction compensating or greater and a plurality of such shelf stowed panels would be in a staggered relationship if each of the panels were of the same size and shape. 
         [0016]    Preferably, the insulated fire panel shutter is provided with a driver motor operatively connected to the panels and means to arrest the rate of panel descent during shutter formation in the event of a motor gear box failure. 
         [0017]    Preferably, the insulated fire panel shutter incorporates biasing means adapted to provide a bias to the shutter as the panels forming the shutter move from their stowed to their deployed position. Such a bias would not only enable a smaller motor to be used to move the panels once having formed the shutter from their deployed back to their stowed position, but the bias would (via an appropriately placed pull-chain) also assist someone trapped on the wrong side of the shutter to lift the shutter sufficiently to enable them to roll, ‘commando-crawl’ or otherwise make their way to the right side of the shutter before allowing the shutter to close again. 
         [0018]    Preferably, the means to arrest the rate of panel descent during shutter formation is the biasing means. 
         [0019]    Typically, a counterweight system would be used to provide such a biasing means, however, any form of counterweight system requires a relatively large amount of space to store the counterweights and space may be at a premium. Accordingly, it is preferable if the biasing means is provided by one or more torsion springs operatively connected to the transmission shaft. Such a biasing means occupies far less space and the ability (if required) to use more than one torsion spring provides greater flexibility in the fabrication of the insulated fire panel shutter, as they tend to be bespoke items. Accordingly, the ability to vary the number, length and/or type of torsion spring to fit a particular set of circumstances would be useful. In such form, the transmission shaft may preferably be circular in cross section. However preferably, the transmission shaft is polygonal (ideally square or hexagonal) in cross section. Such anon-circular cross sectional arrangement will enable a fixture securing the winding end of the or each torsion spring to the transmission shaft with more ‘bite’ as it will be less likely to counter-rotate over time once the stored torque has been applied. 
         [0020]    Preferably, the or each torsion spring is so marked as to be able to provide an indication of the number of turns which have been applied to the or each spring, thus providing an indication of its stored torque/potential energy. 
         [0021]    In order to prevent or reduce the possibility of heat transfer during a fire, preferably, the guide is fitted with one or more intumescent ships. In such form, at least one intumescent strip is fitted to a retractable member. 
         [0022]    There are several ways in which the bias exerted on the or each retractable member may be eliminated, for example, the retractable member may possess an aperture into which the member exerting the bias moves into once the shutter is in the closed position. However, preferably, the or each retractable member is fitted with a camber which eliminates the bias exerted on the or each retractable member by the shutter when the shutter is in the closed position, enabling the movement of the or each retractable member from its retracted to its extended position when the shutter is in its closed position. 
         [0023]    The camber has the advantage that the shutter may be opened or closed easily during day to day operations simply by reversing the direction of the drive motor. If an aperture were used instead of a camber, a further means of retracting the member exerting the bias from the aperture would need to be installed and operated before the shutter could be opened again. The panel could simply comprise a normal panel employed in conventional fire panel shutters. However, the panel of the present invention has been specifically designed for use with (and thus forms part of) the present invention. However, the panel itself may be considered to be new and inventive in its own right and could be used with a conventional fire panel shutter. 
         [0024]    Accordingly, preferably, the or each panel is an insulated metal panel. In such form, the metal panel includes
       a) frame having a front and rear face;   b) a sheet of material fitted to and extending across the front and rear faces of the frame; and   c) a thermally resistant wadding housed within the volume between the sheets of material and perimeter of the frame.       
 
         [0028]    Preferably, the frame is metal and the exterior faces of the sheets of material are covered with a metal sheet in a sliding fit arrangement. Such an arrangement has been found to reduce thermal conductivity through the panel to a minimum compared with conventional panels forming fire shutters as there are no screws securing the sheets to the frame. 
         [0029]    In fact there is no metal to metal contact between the sheets and the frame, reducing any heat transfer between, them by conduction to zero. 
         [0030]    Preferably, the panel is formed from a plurality of metal components, which do not contact each other in the finished panel to form an insulated metal panel. This has the advantage of preventing conduction of heat from one metal component to another and from one face of the panel to the other. In such form, the metal is steel and includes a box frame and front and rear steel sheets. In such form, the front and rear steel sheets are folded and fitted to a flame retardant board. Such an arrangement of a box frame, together with front and rear sheets made from metal (ideally steel) also provide a level of security not typically available to (for example) a normal fire door when closed. 
         [0031]    This is because the ability to ‘kick down’ or ‘sledge hammer through’ a conventional locked fire door is relatively facile but a steel construction including a box frame and front and rear sheeting is another matter. The box frame could be strengthened by, for example, including diagonal or a number of horizontal or vertical metal (ideally steel) cross bars. 
         [0032]    Preferably the wadding comprises a ceramic material and a silica fabric material. It has been found that the use of multiple types of wadding components better prevent heat transfer through the material than just a single type of wadding. 
         [0033]    Preferably, when the shutter is closed, the metal components forming each of the panels do not contact each other. Such an arrangement has the advantage of minimizing heat transfer between panels by conduction. In such form, the metal components between adjacent panels are kept apart by a separating member. Again, in such form, the separating member is formed from a ceramic material. 
         [0034]    Preferably, movement of the panels to form the shutter is actuated by a chain and sprocket mechanism powered by a driver motor. This is beneficial over hand actuation as the shutter is heavy and would be difficult to open if it were not powered in some way. 
         [0035]    The present invention may be used to close off a vertical shaft for example in a mine. In such form, the guide would be sloped towards the horizontal. However, the invention is more usually to be associated with conventional horizontal passageways, doorways or the like. 
         [0036]    Preferably therefore, the guide will be a vertical guide in its normal attitude of operation. 
         [0037]    Preferably, the guide includes two metals as it is preferable if precision portions of the guide are made from material which can be extruded whilst non precision portions do not have to be. In such form, the extrudable material is aluminum. 
         [0038]    Although aluminium has a relatively low melting point (around 660° C.) and as a result would normally be considered unsuitable as a material associated with a fire barrier, it has the advantage that as it may be extruded, it can be manufactured to high engineering tolerances. 
         [0039]    Such high tolerances are required if the clearance fit has to be precise. 
         [0040]    The aluminium in the guide is intended to be strong enough to withstand normal wear and tear during everyday use and in the event of a fire, once the insulated fire panel shutter has closed, it will not matter whether the aluminium component melts or buckles under the heat. 
         [0041]    To save on weight and expense, instead of using solid metal for the non-extruded portion of the guide, fire rated cement board covered with metal could be used instead. 
         [0042]    Preferably, the panels forming the shutter are provided with complementary inter-locking members adapted to lock the panels together once the shutter is formed. Such an arrangement serves to add a further level of security to the shutter as without this form of locking, it is conceivable that the panels may be sufficiently flexed at their midpoint to enable entry by an intruder if the shutter is down in a security rather than a fire shutter capacity. 
         [0043]    Although the number and/or placement of the inter-locking members need not extend across the entire length of each panel, in order for example to save on the cost of the production of a panel, in such form, the complementary inter-locking members extend across the length of each panel. 
         [0044]    Further, in such form, the complementary inter-locking members are in the form of a tongue and groove arrangement. 
         [0045]    Preferably, the shutter once formed is also provided with a flexible flame baffle sheet adapted to span any gap between the top of the shutter once formed and the top of a doorway to which the insulated fire panel shutter is fitted to. Such an arrangement will thus provide an additional barrier in this ‘gap area’ to any flames, heat and/or smoke in the event of a fire. 
         [0046]    In another aspect, the invention resides broadly in a building or structure incorporating an insulated fire panel shutter as specified herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0047]    In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying sheets of drawings wherein: 
           [0048]      FIG. 1  is a perspective view of an insulated fire panel shutter of the present invention in its closed position and fittable to a doorway with its protective cover removed to expose the shutter panel storage facility, sprocket and chain mechanism and drive motor which operates the shutter. 
           [0049]      FIG. 2  is a perspective view of the insulated fire panel shutter of  FIG. 1  in its open position showing panels making up the shutter of the insulated fire panel shutter in their stowed position. 
           [0050]      FIG. 3  is a perspective view of the insulated fire panel shutter of  FIG. 1  in its closed position with the protective cover fitted. 
           [0051]      FIG. 4  is a perspective view of the insulated fire panel shutter of  FIG. 1  in its open position with the protective cover fitted. 
           [0052]      FIG. 5  is a rear elevation of the insulated fire panel shutter of  FIG. 1  in its closed position with the protective cover removed. 
           [0053]      FIG. 6  is a side elevation of the insulated fire panel shutter of  FIG. 1  in its closed position. 
           [0054]      FIG. 7  is a plan view of the insulated fire panel shutter of  FIG. 1  in its closed position with the protective cover removed. 
           [0055]      FIGS. 8-11  are sectional views of the insulated fire panel shutter of  FIG. 1  during various stages of opening/closing of the shutter (without separator blocks {see  FIGS. 18 &amp; 19 } in place to show the chains). 
           [0056]      FIG. 12  is an isometric view of one of the guides forming part of the insulated fire panel shutter of  FIG. 1 . 
           [0057]      FIG. 13  is a partially exploded view of the guide of  FIG. 12 . 
           [0058]      FIG. 14  is a sectional view through the upper end portion of the guide of  FIG. 12  when the insulated fire panel shutter is in its closed position showing opposed retractable members in their extended position. 
           [0059]      FIG. 15  is a sectional view through the upper end portion of the guide of  FIG. 12  when the insulated fire panel shutter is in its open position, showing the opposed retractable members of  FIG. 14  biased into their retracted position. 
           [0060]      FIG. 16  is a sectional view through the lower end portion of the guide of  FIG. 12  (without separator blocks {see  FIGS. 18 &amp; 19 } in place) when the insulated fire panel shutter is in its closed position, showing the opposed retractable members of  FIG. 14  in its extended position due to opposed cambers at the lower end of the guide. 
           [0061]      FIG. 17  is a sectional view through the lower end portion of the guide of  FIG. 12  (without separator blocks {see  FIGS. 18 &amp; 19 } in place) when the insulated fire panel shutter is beginning to open, showing the opposed retractable members of  FIG. 14  beginning to be biased into their retracted position. 
           [0062]      FIG. 18  is a side elevation of a panel forming the shutter panel of the insulated fire panel shutter of  FIG. 1  inclusive of separator blocks. 
           [0063]      FIG. 19  is an isometric sectional view through part of the insulated panel of  FIG. 18  showing the arrangement of materials employed in the make-up of the panel inclusive of separator blocks. 
           [0064]      FIG. 20  is an isometric sectional view through the insulated fire panel shutter of  FIG. 1  to show one of the cassette panels housing a chain and sprocket drive mechanism for the shutter panel. 
           [0065]      FIG. 21  is a side elevation of the cassette panel of  FIG. 20  showing the cassette and chain and sprocket drive mechanism. 
           [0066]      FIG. 22  is a plan view of the cassette panel of  FIG. 20  showing the cassette and chain and sprocket drive mechanism. 
           [0067]      FIG. 23  is a perspective view of an alternative embodiment of the motor containing side of the insulated fire panel shutter similar to that shown in  FIG. 1  showing a right handed and left handed pair of torsion springs fitted to the transmission shaft. 
           [0068]      FIG. 24  is a perspective view of the embodiment shown in  FIG. 23  but also showing alternate types of transmission shaft with complementary fixtures securing the winding end of the or each torsion spring to the transmission shaft. 
           [0069]      FIG. 25  is a perspective view of the embodiment shown in  FIG. 23  encompassing both sides of the insulated fire panel shutter with its protective cover removed. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0070]      FIG. 1  is a perspective view of an insulated fire panel shutter generally referenced  10 , fittable to a doorway and adapted to close off an area in the event of a fire. It is shown in its closed position devoid of a protective cover to show some of its moving/working parts. The insulated fire panel shutter  10  includes a pair of opposed mild steel panel cassettes  11  each being fitted to one end of a vertical (steel covered fire rated cement board) guide  12 . 
         [0071]    Mounted to each cassette  11  is a chain and sprocket assembly  13  which is connected to opposite ends of a steel transmission shaft  14  drivable by a drive motor  15  mounted on one of the cassettes  11 . 
         [0072]    In addition, a panel shelf  16  is also mounted to each cassette  11  in an opposed arrangement which act as a storage facility for the insulated panels  17  (see  FIG. 2 ) used to form the shutter  18  of the insulated fire panel shutter  10  when in the open position. Each cassette  11  is also fitted with a panel guide  19  adapted to direct the movement of stowed panels  17  in use (see later).  FIGS. 3 and 4  show the insulated fire panel shutter  10  with the protective cover  20  on in its closed and open position respectively. 
         [0073]    In the event of a fire the shutter  18  in its closed position will offer a degree of protection to the components mounted to the cassettes  11 , however, an additional degree of protection is provided by a flexible flame baffle sheet  21  made of fire rated fabric which spans the gap between the two cassettes  11  and downwardly depends from the top of the insulated fire panel shutter  10  in front of the chain and sprocket assembly  13 . 
         [0074]    The top of the sheet  21  in its normal attitude of operation being fitted to a rod connected to the top of the insulated fire panel shutter  10  and spanning the gap between the cassettes  11 , whilst the bottom of the sheet  21  is connected to the top of the last of the insulated panels  17 , this final panel  17  being adapted to form the uppermost panel of the shutter  18  in the shutter&#39;s closed position. This baffle sheet  21  has the advantage of being able to bridge any existing gap which may be present between the fire panel shutter  10  and the top of the doorway that it is fitted to. Such a sheet  21  will thus provide an additional barrier in this ‘gap area’ to any flames, heat and/or smoke and is shown more clearly in  FIGS. 5 and 7 . 
         [0075]      FIGS. 8-11  show how each of the panels  17  are connected to the chain and sprocket assembly  13 . As shown, the cassette  11  containing the drive motor  15  includes a downwardly depending endless chain  13   a  linking the drive motor  15  to a motor sprocket (hidden from view) and one sprocket of a double sprocket  13   b  and a trans-mission chain  13   c  connecting the second sprocket of the double sprocket  13   b  to a second sprocket of double sprocket  13   d.  A free chain  13   e  connected to the cassette  11  at one end, rides over the first sprocket of double sprocket  13   d  and is linked to a side wall of a panel  17 . Another section of free chain  13   f  connects this panel  17  to the next panel  17  and this process repeats until each of the panels  17  are connected. The same arrange-ment (save for the endless chain connecting the drive motor  15  to the double sprocket  13   b ) occurs with the other cassette (see also  FIGS. 20-22 ). 
         [0076]      FIGS. 8-11  also show how the shutter  18  is formed as the panels  17  stowed in a parallel staggered overlying front face to rear face facing relationship on the shelves  16  move along shelves  16  and (guided by panel guides  19 ) down the guides  12  when actuated by the drive motor  15 . 
         [0077]      FIGS. 12 and 13  show one of the guides  12  in more detail. Each guide  12  once assembled comprises essentially an elongate square ‘C’ shaped member when seen in cross section with a pair of opposed retractable members  22  housed within and forming part of the guide  12 . Each retractable member  22  comprises a series of contiguous ceramic plates bolted to an elongate steel strip that extends along the length of the guide  12  and towards its bottom end each retractable member  22  terminates with a ceramic plate camber  23 . 
         [0078]    Each retractable member  22  is connected to the rest of the guide  12  by three biasing hinges  24  enabling each retractable member  22  to move between a retracted and extended position relative to the rest of the guide  12 . The hinges  24  bias each retractable member  22  towards the extended position. The front face of each retractable member  22  is fitted with a strip of intumescent material  25  and adjacent each retractable member  22 , is an aluminium guide rail  26 . 
         [0079]    The lowest panel  17  of the shutter  18 , where it passes between the guides  12  is fitted at the base of its front and rear faces with a ceramic biasing member  27  (four in all). The function of these biasing members  27  is to bias each pair of opposed retractable members  22  into their respective retracted position as the shutter  18  moves from its open to its closed position. 
         [0080]    When the lowest panel  17  of the shutter  18  reaches the ground the space created by the camber  23  is slightly greater than the thickness of the ceramic biasing member  27  enabling each retractable member  22 , to move from its retracted to its extended position, permitting the guide  12  to engage the front and rear face of each panel  17  making up the shutter  18  (see  FIGS. 14-17 ). 
         [0081]      FIGS. 18 and 19  show more detail of the nature of one of the insulated panels  17 . As can be seen, each panel  17  is formed from a rectangular steel box frame  28 , the volume defined by the inner perimeter of the frame being filled with a ceramic blanket wadding  29 . A sheet of silica fabric material  30  extends across both the front and rear faces of the frame  28  to trap the wadding  29  located within the frame  28 . A further ceramic blanket  29  also extends across both the front and rear faces of the frame  28  over the silica fabric material  30 . The blankets  29  and materials  30  are secured to the front and rear faces of the frame  28  by a series of elongate ceramic plates  31  that are screwed to the frame  28 . 
         [0082]    The series of elongate ceramic plates  31  although flush with the width of the frame  28 , extend slightly beyond the top and bottom of the frame  28 . A further sheet of silica fabric  30  extends across the entire exterior face of each of the ceramic framed ceramic blankets  29  and is secured to the ceramic frame  31  using the same screws which bolt the ceramic frame  31  to frame  28 . Finally, the front and rear face of the panel  17  is covered in a skin of sheet steel  32 . 
         [0083]    The top and bottom portions of each sheet  32  each possess two  90  degree folds to form respective and shapes in cross section, enabling each sheet  32 , in a ‘sliding fit’, to be fitted to each respective set of the upper and lower ceramic plates  31 . The ends of the respective ‘n’ and ‘u’ shaped folds of each sheet  32  are so sized and shaped as not to contact frame  28  once the sheets  32  have been slid into place (and also after any expansion may have taken place after heating in for example, the event of a fire). 
         [0084]    A ceramic end cap  33  composed of a series of elongate ceramic plates  34  (which are ‘n’ shaped in cross section) is screwed to opposing side walls of the frame  28  to prevent the sheets  32  from sliding off, the end cap  33  being flush with the top and bottom of the series of elongate ceramic plates  31 . 
         [0085]    The opposed side walls of each panel  17  also include opposed upper guide rollers  35  fitted with a pair (upper and lower) of lifting shafts  36  and opposed lower guide rollers  37  each fitted with a lead-in panel guide  38 . One end of the free chain  13   e  connected to the cassette  11  connects to the upper lifting shaft  36  and free chain  13   f  connects to the lower lifting shaft  36  and the upper lifting shaft of the next panel  17 . 
         [0086]    The lead in panel guide  38  is somewhat similar to an old fashioned rotatable handle used to wind car windows up and thus consists of two components the arm  38   a  and the handle  38   b.  The purpose of the arm  38   a  is to distance the handle  38   b  or otherwise ‘offset’ the handle  38   b  with respect to the rest of the guide roller  37  enabling free chain  13   f  to pass vertically down the side wall of the panel  17  without interfering with the handle  38   b.    
         [0087]    In addition, a plurality of elongate ceramic separators  39  protrude beyond the top of the sheet  32  covered ceramic plates  31  and, ‘sit’ on the top wall of frame  28  of all but the uppermost panel  17 . These contiguous separators  39  in cross section are similar to an inverted ‘T’ in shape and form the tongue in an otherwise tongue  39  and groove  40  system. A similar plurality of elongate ceramic separators  40  are also screwed to the bottom wall of each frame  28 , are ‘n’ shaped in cross-section and protrude beyond the bottom of the sheet  32  covered ceramic plates  31 . 
         [0088]    The arrangement between respective tongue  39  and groove  40  ceramic separators is such that when respective separators  39 ,  40  come into contact with each other i.e. when one panel  17  sits on another, during shutter  18  formation, there is an air gap between the fold of steel  32  running along the top face of the ceramic plates  31  of the lower panel  17  and the fold of steel  32  running along the bottom face of the ceramic plates  31  of the adjacent panel  17  above it. 
         [0089]    This air gap prevents conduction of heat between panels  17 . 
         [0090]    In addition the design of the tongue  39  and groove  40  is such that the walls of the upwardly extending leg of the inverted ‘T’ are sloping inwardly slightly and contact between the tongue and groove only occurs between the feet of the groove  40  and the base of the inverted ‘T’  39 . 
         [0091]    This arrangement minimizes the risk of the tongue  39  and groove  40  system ‘sticking’ when the shutter  10  is being opened again. 
         [0092]    Although the plates  31  and  34  and the separators  39  and  40  are shown in a contiguous arrangement in this embodiment, in an alternative non illustrated embodiment, they need not be and as such their number may be reduced to save costs. 
         [0093]      FIGS. 20-22  show one of the cassettes  11  in more detail albeit with the drive motor  15  and its endless connecting chain  13   a  to the double sprocket  13   b  missing. 
         [0094]    In operation, assuming the insulated fire panel shutter  10  is in its open position, upon actuation of the drive motor  15 , motor sprocket and the double sprocket  13   b  and transmission shaft  14  begin to rotate in an anti-clockwise direction causing the transmission chain  13   c  and double sprocket  13   d  to similarly rotate. As a consequence, the first panel  17 , connected by the free chains  13   e,  moves from the cassette  11  and as it begins to lower, it engages the guides  12  enabling its ceramic biasing members  25  to retain the retractable members  22  in their retracted position,. As it does so the opposed upper guide rollers  35  eventually pass between and thus engage with the aluminium guide rails  26 . Soon afterwards, the next panel  17  in the sequence (connected to the first panel by free chain  13   f ) and also stowed on the shutter panel storage facility begins to ride up the angled slope of the shelves  16  (via the upper guide rollers  35 ) and the lead in panel guides  38  eventually engage with the panel guides  19  to aid in directing the lower end of this next panel  17  such that the lower guide rollers  37  are able to pass between and thus engage with the aluminium guide rails  26 . 
         [0095]    At this point, this next panel&#39;s translational motion changes direction from being one in the direction up the slope of the shelves  16  to vertically downward, whereupon the upper guide rollers  35  eventually pass between and thus engage with the aluminium guide rails  26 . 
         [0096]    The descent of this next panel  17  terminates when the feet of the separators  40  on the lower wall of the frame  28  of this panel  17  contact the base of the inverted ‘T’ of the separators  39  on the upper wall of the frame  28  of the lower panel  17  to leave an air gap between the metal portions of each panel  17 . 
         [0097]    During this time the next panel in the sequence is following on from the previous one, the final panel  17  connected to the blanket  21  steadily moving as well. 
         [0098]    As the biasing members  27  of the first panel  17  pass the cambers  23 , the biasing hinges  24  are able to bias the retractable members  22  into their extended positions to contact the now fully formed and fully closed shutter  18 , with the blanket  21  deployed as well. In the event of a fire, the heat will trigger the intumescent material  25  and this will generate a seal between the guides  12  and the shutter  18 . Under normal operating conditions, to open the shutter  18 , the drive motor  15  is simply put into reverse. 
         [0099]      FIGS. 23-25  show a variation to the general design of the insulated fire panel shutter, generally referenced  50 . 
         [0100]    This variant incorporates a bias in the form of four marked torsion springs  51 - 54  to counter-balance the panels  17  of the shutter  18 . Two of the torsion springs  51 ,  52  are right handed (RH) springs and the other pair  53 ,  54  are left handed (LH) springs. One end of each respective pairs of torsion springs is securely fastened to an arm  55  which is in turn fitted to a bar  56  connected to each cassette  11 . 
         [0101]    The other end of each respective torsion spring is fitted to a fixture  57  (reminiscent of an anchor windlass on an old sailing ship) which is complementary with and securely fastened to the transmission shaft  14 . With such an arrangement of RH,LH; RH,LH, on the transmission shaft  14  both pairs of springs  51 , 53 ; 52 , 54  will wind up or unwind together, depending on the rotation of the transmission shaft  14 . 
         [0102]      FIG. 24  shows alternate transmission shafts which are square  58  or hexagonal  59  in cross-section and these potentially offer better ‘bite’ for the complementary fixtures  57  fitted to them, as with a polygonal cross-section to the transmission shaft, there will be less chance of counter rotation from the stored torque energy in the or each torsion spring  51 - 54 . 
         [0103]    The purpose of the springs  51 , 53 ; 52 , 54  is to enable either a smaller drive motor to be employed than would otherwise be required as the springs  51 , 53 ; 52 , 54  assist with the opening and closing of the insulated fire panel shutter  50  or the same ‘standard’ drive motor  15  to enable particularly heavy panels  17  to be moved and formed into the shutter  18 . The torsion springs  51 - 54  also act as a safety feature in this embodiment as they will prevent the panels  17  from crashing down should drive motor  15  fail. They will also extend the longevity of the drive motor  15  as it will not need to work as hard to raise the panels  17  of shutter  18 . 
         [0104]    A pull chain  60  of sufficient length is connected to the motor and is also shown in  FIGS. 23-25  the purpose of which is to release the motor brakes and thus disengage the drive motor  15  from the gear box to allow the motor sprocket to move freely. 
         [0105]    When the drive motor  15  is actuated, the shutter  18  is allowed to form in a manner previously described thus closing the insulated fire panel shutter  50 . 
         [0106]    In order to initially apply the appropriate amount of torque to the springs  51 , 53 ; 52 , 54 , one end of a rod (not illustrated) is inserted into one of the apertures  61  of the fixture  57  (which is at this point free to rotate) and is wound such that the appropriate torsion spring begins to store torque, and when sufficient rotations of the torsion spring have been completed (indicated by the marks on the torsion spring  51 ) the fixture  57  is securely fastened to the transmission shaft  14 . 
         [0107]    This process is repeated for each torsion spring  52 - 54  but the number of turns need not be identical. 
         [0108]    Accordingly, in this embodiment, upon actuation of the drive motor  15 , when the fire panel shutter  50  is in its open position, torque in each of the springs  51 , 53 ; 52 , 54 , will slowly build up as the shutter  18  forms.