P/00/009 25.5.91 Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Invention Title: IMPROVEMENTS IN SLIDING DOORS The invention is described in the following statement: -2 FIELD OF INVENTION The present invention relates to improvements in sliding doors, in particular, but not exclusively to vertical sliding doors. BACKGROUND ART KNOWN TO THE APPLICANT 5 Entrances into large enclosed industrial environments tend to be of two general types swing doors made of thick, tough plastics material (to withstand the battering of trolleys or fork lift trucks and the like) and sliding doors normally referred to in the trade as "Rapid Action Doors" or "PVC High Speed Doors" that are adapted to open on the approach of either an individual or a vehicle. 10 In respect of the latter, the majority of sliding doors tend to be vertical sliding (or "vertical rise") doors and fall into two general types so called "Roman" or "Folding doors" and "Roller doors". Roman doors are typically exterior doors formed from a sheet of plastics material provided with parallel spaced apart horizontal fibreglass or steel battens that extend from one edge of 15 the door to the other. As such, the doors are light, yet able to withstand high winds making them ideal for external use and may contain vertical flexible woven cords operatively connected externally to each batten at respective points on the door which enable the door to be raised by allowing the cords to rotate about respective cord collecting reels located above the door. 20 Roller doors by comparison, tend to be internal doors and are again formed from a sheet of plastics material. However, being devoid of battens or cords, they are adapted to rotate about a "roller drum" that usually doubles as a lintel spanning the width of and located above the doorway. Actuation of both of these types of door is typically via an electrical operating mechanism 25 located in close proximity to the door. The rate of door opening or closing is usually very rapid and automatic on the approach of a vehicle or an individual. When roller doors are used in an environment where there is a large temperature difference between the outside temperature and the internal temperature, for example when a roller door -3 separates a freezer section from ambient, the temperature gradient set up on either side of the door inevitably tends to lead to a build up of ice on the ambient face of the door as the door remains in its closed position for extended periods. Subsequent opening and closing of such an ice ridden door may damage the electrical 5 operating mechanism of the door "at worst" or cause the door actuation process itself to jam "at best". In either situation, the result is not satisfactory. Furthermore, such doors are usually subject to impact from vehicles such as fork lifts and the like because the doors fail to open rapidly enough because of their design. It is therefore an object of the present invention to go at least some way towards alleviating 10 these problems or to at least to provide the public with a useful choice. STATEMENTS OF THE INVENTION According to one aspect of the present invention, there is provided a sliding door comprising a frame and a sheet or web of flexible material, each provided with complementary runners and guides operatively connecting the sheet to the frame and means adapted to move the 15 material from a first door closed position to second door open position and wherein at least some of the runners are provided with impact blocks that are so sized and shaped as to absorb the impact of adjacent runners when the door moves from its closed to its open position. In this way, very rapid door opening and closing can be achieved without undue wear and 20 tear on the runners. Preferably, the impact blocks are designed to be replaceable. The impact blocks could be formed from metal, metal alloys, wood or a resilient material such as natural rubber. Preferably, the impact blocks are formed from plastics material. 25 More preferably, the plastics material is a urethane.
-4 The impact block is preferably sandwiched between two plates that form a runner. These paltes provide a degree of flexibility in the event that the door is impacted. Preferably, the plates are formed from a plastics material. More preferably still, the plastics material may selected from the group comprising ultra high 5 molecular weight polyethylene or urethane. Preferably the flexible material is provided with an insulating layer. The material may sandwich this insulating layer thus providing the door with good thermal insulation properties so that there may be a temperature gradient between both sides of the door, eg because the door separates a freezer area from an ambient in a cold storage facility. 10 Preferably, the runners are located on the flexible material and the guides form part of the frame. More preferably, each of the runners is provided with an impact block. Preferably, a batten is placed between one or more opposing runners to add stability to the door. More preferably still the battens consist of fibreglass rods of annular cross-section. 15 This is because it has been found that such battens give greater strength, flexibility and weight although it will be appreciated by those skilled in the art that other materials or shapes may be used as battens. More preferably, the longitudinal axis of the battens is substantially coincident with the longitudinal axis of the opposing runners 20 The battens may be inserted into pockets which run substantially the width of the flexible material however, preferably the battens are sandwiched or otherwise sealed within the flexible material. The flexible material as it moves from a door closed to a door open position will fold/collapse during this movement. Given the rapid nature of opening and closing and the 25 cost of replacing the flexible sheet if it wears out, it would be useful to ensure that areas of uneven wear and tear of the material are kept to an absolute minimum. Furthermore, in order -5 to prevent snagging of the material so designing the sheet so as to always fold or collapse in the same way would be advantageous. Preferably therefore, the flexible material is provided with uni-directional folding means to cause the material to fold or other wise collapse in the same manner each time the material 5 moves between closed and open positions. With such an arrangement the folds tend to be in a direction that is perpendicular to the line of travel of the material when it moves between open and closed positions. Furthermore, the uni-directional folding means ensure that each fold is in the same direction. More preferably, the or each means are located substantially mid way between battens. This 10 enables the flexible material to fold easily and regularly. Preferably, the door opens and closes by moving vertically. Preferably, the base of the door is provided with a flexible weight that runs along its length or some lesser portion thereof to facilitate rapid closure of the door. More preferably still, the said flexible weight is designed such that if the door should hit a 15 person while being lowered the flexible weight will fold over the person thus minimising any personal injury. Alternatively, the door is provided with a 'kick bar' towards the base of the door. This reduces damage being caused to the door by a vehicle such as a fork lift truck ramming the door should it fail to open sufficiently or at all. 20 The or each guide is provided with a wear strip on one side of the guide formed from the same material as the impact block. Preferably, the means adapted to move the material from a first door closed position to second door open position include straps operatively linked to the side opposite the direction of fold or collapse of the material as it moves between positions. 25 Preferably, a runner is so adapted as to be able to freely disassociate itself from its complementary guide if the material is impacted by a sufficient force. This prevents the -6 material form ripping and the runner from snapping and as the runner can be pushed back into place after such an impact, little harm is actually done to the door. The invention includes within its scope a sliding door substantially as herein described with reference to and as illustrated in the accompanying drawings. 5 The invention further includes within its scope a building incorporating a sliding door as specified above. Throughout the description of this specification the word 'comprise' and variations of that word, such as 'comprises' and 'comprising' are not intended to exclude other additives, components, integers or steps. 10 BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will now be more particularly described, by way of example only, with reference to the accompanying sheets of drawings in which: Figure 1 illustrates a view of a sliding door forming the basis of the present invention. Figure 2 illustrates a more detailed view of the sliding door forming the basics of the 15 present invention. Figure 3 illustrates the plastics means. Figure 4 illustrates the plastics means attached to the sliding door. DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 1 shows a vertical sliding door that is generally referenced (1). The sliding door (1) 20 comprises a door (2) formed from two sheets of flexible plastics (PVC) material on either side of a sheet of material having good thermal insulation properties. Attached to opposing sides of the door (2) are a plurality of runners (3) which serve to lift and lower the door (2) and to keep the door (2) within vertical guides (4) that form part of the vertical sides of the oblong frame that surrounds three sides of the door (2). 25 Elongate straight columnar plastics battens (5) of uniform cross section are sandwiched between the sheets of flexible material and span the width of the door (2) , the longitudinal -7 axis of the battens (5) being substantially coincident with the longitudinal axis of each pair of opposing runners (3). The battens (5) provide stability to the material. Parallel with and located substantially mid way between adjacent battens are a pair of castellated moulded plastics strips (6), which project from one side of the door (2) only. This 5 arrangement allows the door (2) to fold about the strips (6) in one direction only when the door (2) is raised. The raising and lowering of the door (2) is accomplished by a power operated winch (7) attached to a pair of parallel downwardly depending strips of webbing material (8) located towards opposing sides of one side of the flexible sheet of material. The strips (8) pass 10 through a gap in each of the runners (3) and are attached to the door (2) close to the base (9) of the door. Figure 2 shows the runners (3), battens (5), folding means (6) and webbing strips (8) in greater detail. Figure 3 shows the make up of the runners (3) in greater detail. As can be seen, each runner (3) consists of an oblong shaped tapered piece of ultra high molecular weight polyethylene 15 (10) adjacent to which is placed a piece of polyurethane (11) which is shorter than the oblong (10) but fatter than it. This item (11) is an impact block. Adjacent to this piece of heavy duty plastics material (11) is placed another oblong shaped piece (12) of a similar shape and dimensions to piece (10) but containing a recess (13) that runs orthogonally to the longitudinal axis of the oblong. When in use the three pieces of 20 plastics material (10), (11) and (12) are screwed, together with the door being held between pieces (10) and (11) and with the strips (8) passing through the recess (13). Figure 4 shows the runners (3) and the strip of material (8) in position on one side of the door (2), together with the wear strip (14). As can be seen, the strips (8) are located on the side of the flexible sheet of material that does not accommodate the folds of the material 25 when the door (2) is raised. When the door (2) is raised from its closed position to an open position by activating a switch, the power operated winch (7) revolves in an anti-clockwise direction and the strips of material (8) are raised. The base of the door (9) is thereby raised and the door folds at the -8 folding means in a direction orthogonal to the direction of movement and away from the side of the material that contains the strips (8). As the door (2) is raised at speed, the impact blocks (11) hit each other thus preventing damage to the PVC curtain (3). When the door is closed, again by activating the switch, the 5 reverse process occurs until the base of the door (9) is touching the floor. ADVANTAGES OF THE PRESENT INVENTION An advantage of the present invention is that in place of the typical elongated substantially 'c' or "u" shaped steel or metal guide positively housing the runners, running parallel to the direction of travel of the door, only a vertical upright of wood, plastics material, metal etc is 10 required as a guide, as the runners embrace either side of the guide making manufacture of the door system simpler, cheaper and providing a superior seal. Another advantage of the present invention is that in the event of a collision between an individual or a vehicle and the door, the probable result is that one or both sides of the door will come out of the door frames, as the runners are designed to "pop out", a process made 15 all the easier by the fact that the battens are designed to flex (if hit) in a direction orthogonal to the longitudinal axis of the batten. The flexible nature of the door described will allow the door to be easily put back into its correct placement, thus reducing the "down time" of the door in the event of such a collision. A further advantage of the present invention is that when impact blocks (11) come together 20 as the door is raised, due to the choice of material used to form the aforesaid blocks, any collision between the blocks is reasonably quiet. As the blocks come together or stack up. The blocks create a gap that allows the soft PVC curtain to fold together without contacting under load. Furthermore, as they are also designed to be replaceable, relatively expensive runners can be used as any impact damage is absorbed by the impact blocks (11) and not the 25 runners per se.