Floor structure for portable unit

Abstract: A floor structure (10) in or for a portable building unit, the floor structure comprising a floor frame comprising a pair of side beams (11,12) interconnected together by transversely extending joists (23), a floor panel (32) supported on the floor frame, an underdrawing and insulation material disposed between the floor panel and the underdrawing, characterised in that the underdrawing comprises a sheet (35,36,37) spaced from the floor panel with the joists disposed between the floor panel and the underdrawing sheet and thermally insulating material disposed between the floor panel and the underdrawing sheet.

Description: This invention relates to a floor structure in or for a portable building unit. EP-B-0,058,354, EP-B-0,105,406 and GB-B-2,084,213 and each disclose an example of a portable building unit which is factory assembled for delivery to a prepared site in assembled condition. EP-B-0,039,592 discloses an example of a building unit which is intended to be transported in a pack for erection when delivered to a suitable site. The building units of the above mentioned examples have a floor structure which comprises a floor frame comprising a pair of side beams connected together by transversely extending joists and a floor panel supported on the floor frame with an underdrawing of bitumen impregnated fibreboard thermal insulation laid between and supported by the joists with mineral fibre insulation laid between the joists between the floor panel and the underdrawing. However, such an underdrawing is susceptible to puncturing, for example during transport or handling and this can lead to, for example, a loss of thermal insulation efficiency and infestation by insects. A further building panel for use in, for example, ceilings is known from DE-A-3711141, in which the panel comprises a plurality of joists. The panel is assembled on site. Floor panels are provided attached to the upper surface of the joists and plasterboard is attached to battens on the underside of the joists. Resistance to shear forces is provided by screws attaching the floor panels to the joists, wherein the screws have a large diameter shank. Insulation material is provided to partly fill the space between the floor panel and the plasterboard. A further building panel is disclosed in DE-A-3400404, in which the panel has a frame which comprises parallel joists connected at a distance by a low thermal conductivity spacer. An object of the present invention is to provide a new and improved floor structure in or for a portable building unit. According to one aspect of the present invention we provide a floor structure in or for a portable building unit, the floor structure comprising a floor frame comprising a pair of side beams interconnected together by transversely extending joists, a floor panel supported on the floor frame, an underdrawing and insulation material disposed between the floor panel and the underdrawing, wherein the underdrawing comprises a sheet spaced from the floor panel with the joists disposed between the floor panel and the underdrawing sheet and thermal insulating material disposed between the floor panel and the underdrawing sheet, characterised in that the thermal insulating material is sandwiched between and bonded to the floor panel and the underdrawing sheet. The thermal insulating material may comprise a rigid foam expanded plastics material such as a closed cell polymer insulating material, for example, polyurethane. The floor panel and the underdrawing sheet may engage top and bottom surfaces respectively of the joists. The underdrawing sheet may be profiled comprising a plurality of spaced parallel recesses in which are received a portion of the joists. The underdrawing sheet may comprise a metal sheet of, for example, zinc aluminium alloy but, depending on desired service conditions and performance, may be made of other sheet material such as galvanised or colour coated steel, or may be made of sheet material such as aluminium or of a synthetic plastics material such as glass reinforced plastics material. Since the bottom part of the floor panel is subjected to tension forces in use, it is important that the bottom part of the floor panel can accommodate tension loads. This is achieved, despite the profiled nature of the underdrawing sheet, by the bonding of the underdrawing sheet to the floor panel with the rigid foam expanded plastics material. Because the floor panel and the underdrawing sheet are made of gas impermeable, or at least substantially gas impermeable, material any gas which permeates outwardly from the expanded plastics material is trapped by the floor panel, underdrawing sheet and the side beams and joists and so is retained within the floor structure, thereby contributing to the thermally insulating properties of the floor panel. Moreover, during manufacture of the floor structure, by injecting a fluid precursor of the rigid expanded plastics material into a chamber or chambers provided between the side beams, transverse joists, floor panel and underdrawing sheet, gas which is evolved during the injection process is trapped within the chamber because of the impermeable nature of the floor panel and underdrawing sheet and of the beams and joists. Depending upon the size of the floor structure, the floor panel may comprise a plurality of floor panel elements disposed in side by side relationship. Similarly, alternatively or in addition, the underdrawing may comprise a plurality of underdrawing sheets. Where a plurality of underdrawing sheets are provided adjacent edge portions of adjacent sheets may be disposed in overlapping relationship, and in particular in the region of the above mentioned recesses. Each recess may be of generally trapezoidal configuration comprising a pair of limbs which extend downwardly away from the floor panel and inwardly towards each other and a web part extending between the lower ends of the limbs parallel to the floor panel. One edge of a one underdrawing sheet of a pair of adjacent underdrawing sheets may be provided with a first downwardly and inwardly inclined limb, a web part at the lower end of the first limb and a second limb which extends upwardly and outwardly away from the web whilst the adjacent edge of the other sheet of the pair is provided with a first, downwardly and inwardly inclined limb, a web part at the lower end of the first limb and a second limb which extends upwardly and outwardly away from the web part, the first limb, web part and the second limb of the other sheet being arranged to be disposed in overlapping relationship with portions of the limbs and web of the one sheet. A joist may be engaged with an inwardly directed surface of the web part of the one sheet and a fastening may extend through a portion of the joist and of the two web parts to secure said elements together. Each end underdrawing sheet may be provided with a flange adapted to engage opposite end joists of the floor structure. Suitable sealing means may be provided between edge parts of each underdrawing sheet where the underdrawing sheet engages end joists and/or the side beams. The sealing means may comprising a foam plastics tape material. A thermal break may be provided between the upper surface of the joists and/or side beams and the undersurface of the floor panels. Examples of the invention will now be described with reference to the accompanying drawings wherein: FIGURE 1 is a plan view of a floor structure embodying the invention but with the floor panel shown broken away. FIGURE 2 is a section on the line 2-2 of Figure 1, FIGURE 3 is a section on the line 3-3 of Figure 1, FIGURE 4 is a section on the line 4-4 of Figure 1, FIGURE 5 is a section on the line 5-5 of Figure 1, FIGURE 6 is a side elevation, with parts omitted, of a first end underdrawing sheet of the floor structure of Figure 1, FIGURE 7 is a side elevation, with parts omitted, of an intermediate underdrawing sheet of the floor structure of Figure 1, FIGURE 8 is a side elevation of a second end underdrawing sheet of the floor structure of Figure 1, FIGURE 9 is a diagrammatic plan view of the floor structure shown in Figure 1, and FIGURE 10 is a fragmentary longitudinal section of the floor structure of Figure 9, drawn to an enlarged scale and with parts omitted. Referring to the drawings, a floor structure for use in a portable building unit of, for example, the kind described in any one of EP-B-0,058,354, EP-B-0,105,406, GB-B-2,084,213 and EP-B-0,039,592 or in any other suitable portable building unit is shown at 10 and comprises two parallel longitudinally extending floor side beams 11, 12 disposed to extend along the longitudinal sides of the floor structure. The floor side beams 11, 12 are identical and are made as rolled sections in steel, preferably cold rolled, and are of essentially channel configuration having a web 13, comprising a main part 13 a and an upper inclined part 13 b which allows an outwardly opening door set to be fitted with a threshold flush with the surface of the floor deck. The side beams 11 and 12 also have top and bottom limbs 14, 15 which extend perpendicular to the web part 13 a . Fastened by rivets to the side beams 11, 12 are a plurality of intermediate cross-beams or joists 23 which extend transversely of the floor structure and are located at spaced positions longitudinally of the side beams 11, 12 at positions intermediate their ends. In addition, end cross-beams or joists 24, 25 are provided to extend between opposite ends of the side beams 11, 12. The end joists comprise a web 26 comprising a main part 26 a and an upper inclined part 26 b corresponding to the inclined part 13 b and provided for the same purpose. The end joists also have top and bottom limbs 27, 28 with a downwardly depending lip 29 at the free end of the upper limb 27. The length of the web 26 is such that the limb 27 lies in the same plane as the upper limb 14 of the side beams 11, 12 whilst the lower limb 28 is in face to face contact with the upper surface of the lower limb 15 of the side joists 11 and 12. The intermediate joists 23 are of essentially the same configuration as the end joists 24, 25 and hence the same reference numerals are used but with the addition of a prime sign. The intermediate joists 23 differ only in that the web 26' is planar and the upper and lower limbs 27', 28' are wider than the corresponding limbs 27, 28 of the end joists and they are made of somewhat thicker section. The joists 23, 25 are provided with cut-outs 30 to accommodate the limb 14 of the side beams 11, 12. The limbs 27' of the intermediate floor joists are joggled downwardly at their opposite ends, as shown at 27' a to receive the upper limb 14 of the side beams 11, 12, the flange 14 of the side beams 11, 12 and to enable a screw fixing, not shown, to be applied, thereby securing the limb 14 to the limb 27' of the side beams 11, 12. In the present example the intermediate joists 23 are 800mm apart and the end joist 24 is at substantially the same spacing from the adjacent intermediate joist 23, whilst the joist 25 is spaced from the adjacent intermediate joists of about 105mm. Supported from the joists 23, 24 and 25 and the upper limbs 14 of the side beams 11, 12 is a floor deck 31 made of, in the present example, three floor panels 32 made of flooring grade with particle board with a fully bonded vinyl covering. However, if desired, other material may be used. The nature of the floor deck, which in the present example is 18mm thick and moisture resistant and gas impermeable, provides the floor structure with a solid feel which is aided by the floor covering of vinyl. The floor structure is provided with an underdrawing which, in the present example comprises a plurality of underdrawing sheets comprising a first end underdrawing sheet 35 as shown in Figure 6, six intermediate underdrawing sheets 36 as shown in Figure 7, and one opposite end underdrawing sheet 37 as shown in Figure 8. The underdrawing sheets in the present example are made of a zinc aluminium alloy but, if desired, may be made of any other suitable material such as galvanised or colour coated mild steel, or a synthetic plastics material such as glass reinforced plastic. The underdrawing sheets have co-operating end formations which provide generally trapezoidal shaped recesses 38. Each recess 38 comprises a pair of downwardly and inwardly inclined limbs 39 with a web 40 extending between their lower ends parallel to the floor deck 31. The first end underdrawing sheet 35 shown in Figure 6 has a main planar part 35 a which, in use, lies parallel to and spaced from the floor deck 31 at a position intermediate the top and bottom ends of the joists 23, 24, 25 and, at one end thereof has a downwardly depending end flange 35 b . At the other end there is an end formation F 1 which is adapted to co-operate with an end formation F 2 or F 3 of an adjacent intermediate panel 36. The end formation F 1 of the underdrawing sheet 35 comprises a first limb part 35 c , a web part 35 d and a second limb part 35 e of shorter extent than the limb part 35 c . Each intermediate underdrawing sheet 36 has a main planar part 36 a which lies in the same plane as the part 35 a and, at one end, an end formation F 2 having a first limb part 36 b , a web part 36 c and a second limb part 36 d and at the other end an end formation F 3 , having a first limb part 36 e , a web part 36 f and a second limb part 36 g . The formations F 2 and F 3 are similarly configured and the sheet thickness is such that a formation F 2 or F 3 of one sheet can nest in a formation F 3 or F 2 respectively of an adjacent sheet, as hereinafter to be described in more detail. The other end underdrawing sheet 37 likewise has a main planar part 37 a which lies in the same plane as planar parts 35 a and 36 a and an end downwardly depending flange 37 b . At its other end it has an end formation F 4 comprising a first limb part 37 c , a web part 37 d and a second limb part 37 e . The web part 37 d of this sheet is somewhat wider than the web parts 36 c and 36 f of the other sheets. In the present example the web parts 36 c and 36 f are 70mm long, whilst the web parts 35 d and 37 d are 80mm long. The underdrawing sheets 35, 36, 37 are assembled together as described hereinbefore and as shown in Figures 2, 5, 9 and 10. Initially, the central sheet marked 1 in Figure 9 is positioned. The remaining sheets 2 a , 2 b and 3 a , 3 b are then positioned working outwards towards each end and finally the end sheets 4 and 5 are positioned. Sheet 1 and the sheets 2 a , 2 b and 3 a , 3 b are underdrawing sheets 36 with the sheets 2 a and 2 b being orientated as shown in Figure 7, whilst the sheet 1 and the sheets 3 a and 3 b are orientated at 180° to the orientation shown in Figure 7. It will be noted that at the junction of the left-hand side of sheet 1 with the sheet 2 the formations F 3 of the respective sheets are nested, whereas at the junction between the two sheets 2 a and 2 b formation F 2 is nested within formation F 3 whilst at the junction between sheet 4 and the left-hand end of sheet 2 b region F 2 is nested with the region F 1 . Similarly, at the junction between sheet 1 and sheet 3 a region F 2 is nested with region F 3 , whilst at the junction between sheet 3 a and sheet 3 b formation F 2 is nested within formation F 3 , and at the junction between sheet 3 b and sheet 5 formation F 2 is nested within formation F 4 . To ensure that end flange 35 b of the first end underdrawing sheet 35 shown in Figure 6 and shown at 4 in Figure 9 and end flange 37 b of other end underdrawing sheet 37, shown in Figure 8 and at 5 in Figure 9, are in contact with the internal faces of the two end joists 24 and 25, and web part 37 d of other end underdrawing sheet 37 is made wider than the web parts 36 c , 36 f of the intermediate sheets 36, (in the present example 10mm wider) to accommodate any tolerance in spacing of the components. If desired the web part 35 d of first end underdrawing sheet 35 may, alternatively or in addition, be made wider than the web parts 36 c , 36 f . Received in the recesses thus formed are the bottom limbs 28' of the intermediate joists 23 and a fastening, such as a rivet 38, extends through apertures provided in the overlapping web parts and in the limb 28' to secure the sheets and limb together. The downturned flanges 35 b , 37 b abut the webs of the end joists 24, 25 respectively whilst the edges of the sheets which are adjacent the side beams 11, 12 abut the webs 13 thereof with a foam tape 39 or other suitable sealing material being provided to provide a gas tight seal therebetween. The floor deck panels 32, which are secured to the upper limbs of the joists and side beams by suitable self tapping screws, together with the underdrawing sheets 35 - 37 and the end beams and joists, provide a plurality of chambers 40 each of which is filled with rigid foam expanded plastics material such as polyurethane foam in conventional manner and preferably using the method and apparatus described in a co-pending application, reference no. A8155GB. The foam material, shown in the drawings diagrammatically at 41, is bonded to the above described components and thus provides a composite structural sandwich floor structure which is capable of accommodating tension forces in the lower part of the panel. If desired, a suitable thermal break such as wood or other thermally insulating material may be provided between the upper surface of joist and/or the side beams and the underside of the floor deck panels 32. The provision of the above described underdrawing sheets ensures that thermal efficiency is maintained and minimises risk of puncturing during transport and handling and because the non-permeable nature of the components of the floor structure which define the chambers 40 any loss of the gas from the cells of the foam plastics material is minimised. In the present example the cells contain carbon dioxide which has relatively good thermal insulation properties and therefore even if carbon dioxide permeates from the foam plastics material it is retained within the floor structure because of the impermeable nature of the components defining the chambers. The composite structure described hereinbefore permits the spacing of the joists to be increased compared with that provided previously for joints of the same size. In the present example the joists are spaced 800mm apart whilst hitherto the spacing had typically been 400mm. If desired the spacing and size of the joists may be varied from that described hereinbefore as appropriate for the load conditions encountered in service. In the present example the foam plastics material has a thickness of approximately 50mm but if desired it may be of a different thickness either greater or smaller and the underdrawing sheets being profiled accordingly. If desired the underdrawing sheets may be planar in which case the foam plastics material would have a thickness corresponding to the depth of the joists. In order to prevent the foam plastics material preventing access to rivet nuts 43, attached to the beams 11, 12 and end joists 24, 25 for securing wall panels and other components to the building structure, wood particle board packers 42 are provided as shown in Figures 3 and 4. In addition a foam tape is positioned between the main parts 35 a and 37 a of the end underdrawing sheet and the particle board packers 42. The end joists 24, 25 and the side beams 11 and 12 are connected together at the four corners of the floor using a connecting angle 9 to which the webs of the joists and side beams are riveted. The end underdrawing sheets 35 and 37 are provided with recesses at the corners having the flanges 35 b and 37 b to accommodate the angle 9. The features disclosed in the following claims may be utilised for realising the invention in diverse forms thereof.

Claims: A floor structure in or for a portable building unit, the floor structure (10) comprising a floor frame comprising a pair of side beams (11, 12) interconnected together by transversely extending joists (23), a floor panel (31) supported on the floor frame, an underdrawing and insulation material (41) disposed between the floor panel (31) and the underdrawing, characterised in that thermal insulating material (41) is sandwiched between and bonded to the floor panel (31) and an underdrawing sheet (35, 36, 37), the underdrawing sheet being spaced from the floor panel with the joists (23) disposed between the floor panel (31) and the underdrawing sheet (35, 36, 37). A floor structure according to claim 1 wherein the thermal insulating material (41) comprises a rigid foam expanded plastics material such as a closed cell polymer insulating material, for example, polyurethane. A floor structure according to any one of the preceding claims wherein the floor panel (31) and the underdrawing sheet (35, 36, 37) engage top and bottom surfaces respectively of the joists (23). A floor structure according to any one of the preceding claims wherein the underdrawing sheet (35, 36, 37) is profiled comprising a plurality of spaced parallel recesses (38) in which are received a portion of the joists. A floor structure according to any one of the preceding claims wherein the underdrawing sheet (35, 36, 37) comprises a metal sheet or a sheet of a synthetic plastics material. A floor structure according to any one of the preceding claims wherein the floor panel (31) and the underdrawing sheet (35, 36, 37) are made of gas impermeable, or at least substantially gas impermeable, material. A floor structure according to any one of the preceding claims wherein the floor panel (31) comprises a plurality of floor panel elements (32) disposed in side by side relationship. A floor structure according to any one of the preceding claims wherein the underdrawing comprises a plurality of underdrawing sheets (35, 36, 37). A floor structure according to claim 8 wherein adjacent edge portions (F 1 , F 2 , F 3 , F 4 ) of adjacent sheets (35, 36, 37) are disposed in overlapping relationship. A floor structure according to claim 4 or any one of claims 5 to 9 when dependent on claim 4 wherein each recess (38) is of generally trapezoidal configuration comprising a pair of limbs (39) which extend downwardly away from the floor panel (31) and inwardly towards each other and a web part (46) extending between the lower ends of the limbs parallel to the floor panel (31). A floor structure according to claim 9 or claim 10 wherein one edge of a one underdrawing sheet of a pair of adjacent underdrawing sheets (35, 36, 37) is provided with a first downwardly and inwardly inclined limb (36 b ), a web part (36 c ) at the lower end of the first limb (36 b ) and a second limb which extends upwardly and outwardly away from the web (36 c ) whilst the adjacent edge of the other sheet of the pair is provided with a first, downwardly and inwardly inclined limb (36 e ), a web part (36 f ) at tile lower end of the first limb (36 e ) and a second limb (36 g ) which extends upwardly and outwardly away from the web part (36 f ), the first limb (36 e ), web part (36 f ) and the second limb (36 g ) of the other sheet (36) being arranged to be disposed in overlapping relationship with portions of the limbs (36 b , 36 d ) and web (36 c ) of the one sheet (36). A floor structure according to claim 10 or claim 11 when dependent on claim 10 wherein a joist (23) is engaged with an inwardly directed surface of the web part (36 c ) of the one sheet and a fastening extends through a portion of the joist and of the two web parts (36 c , 36 f ) to secure said elements together. A floor structure according to any one of the preceding claims wherein each end underdrawing sheet (35, 37) is provided with a flange (35 b , 37 b ) adapted to engage opposite end joists (24, 25) of the floor structure (10). A floor structure according to any one of the preceding claims wherein sealing means is provided between edge parts of each underdrawing sheet (35, 36, 37) where the underdrawing sheet engages end joists (24, 25) and/or the side beams (11, 12). A floor structure according to claim 14 wherein the sealing means comprises a foam plastics tape material (39). A floor structure according to any one of the preceding claims wherein a thermal break is provided between the upper surface of the joists (23, 24, 25) and/or side beams (11, 12) and the undersurface of the floor panels (31).

Inventors: BOTHAM STEPHEN CHARLES, HOGGARTH CHRISTOPHER JOHN, BOTHAM, STEPHEN CHARLES, HOGGARTH, CHRISTOPHER JOHN
Applicants: PORTAKABIN LTD, PORTAKABIN LIMITED
Application year: 1995
Main classification: E04B1
IPC codes: E04B1