Field of the Invention

The invention relates to a roof system comprising roof support and roof, preferably a flat roof, preferably for a food or pharmaceutical manufacturing plant. Such a roof is usually supported by girders and joists.

Description of Related Art

In a typical food plant or pharmaceutical plant, there will be several large rooms containing food or pharmaceutical processing equipment, where the food, etc., is processed and packaged by the workers. The roof of the building will typically be 15-25 feet (4.6-7.6 m) above the floor and the food processing equipment. The flat roof of the building will be supported by a large number of horizontal steel girders and joists. Strict regulations require that the entire room, including the steel girders and joists, be regularly cleaned and sanitized.

In the prior art, the steel girders and joists of a food plant have many flat surfaces, crevices, and nooks and crannies where dust, grease and tiny food particles can collect and where microbial growth can occur. Because of the nooks and crannies, it is difficult to effectively remove the dust, grease and particles and sanitize all the surfaces of the steel girders and joists.

There is a need in food plants and pharmaceutical plants for steel girders and joists having a minimum of flat surfaces, nooks and crannies, so that the girders and joists can be more effectively washed, cleaned and sanitized.

Fig. 1 shows a top plan view of the steel support members (roof support) according to the prior art which support the flat roof, such as of a food plant. Fig. 1 shows five girders 4, each one perhaps 40 feet (12.2 m) long, 8 inches (20.3 cm) wide and 24 inches (61 cm) high. Each girder 4 has two ends 2, 3. Each end 2, 3 is supported from the floor of the food plant by a large long steel post (see, eg., post 5, girder 4 and joist 6a of Fig. 2) which is perhaps 20 feet (6.1 m) high (if the height of the roof of the plant is about 20 feet (6.1 m)). Fig. 1 shows seven joists 6 spanning the gap between adjacent girders 4. Each joist is, for example, 40 feet (12.2 m) long, 3 inches (7.6 cm) wide and 30 inches (76 cm) high. The girders 4 support the joists 6 and the steel posts 5 support the girders 4. Each girder 4 is traditionally a strong I-beam, also called a wide flange girder; a type of strong I-beam is shown at 4 in Fig. 2.

Traditionally, each joist 6 is a bar joist, such as the conventional steel bar joist 6 shown in Fig. 3. With reference to Fig. 3, each bar joist 6 has a top chord 8, a bottom chord 10, and web members 12. As shown in Fig. 3, the top chord 8 can be a pair of angle irons 8a, 8b and the bottom chord 10 can be a pair of angle irons 10a, 10b. A plate 9 can be provided to rest on the top of girder 4 (see, eg., Fig. 2).

Typically, each web member 12 can be a solid steel bar, or an angle iron with its ends squashed to fit between the two angle irons 8a, 8b in the top chord 8 and between the two angle irons 10a, 10b in the bottom chord 10. Fig. 2 shows how each end of the bar joist 6 or 6a can be supported by the girder or I- beam 4.

It is also known in the prior art, instead of using the bar joist 6, 6a (that is, the joist 6 in Fig. 1), to instead use a joist which is called a rectangular steel tube joist or HSS joist. HSS stands for Hollow Structural Section. Fig. 4 shows (not to scale) a rectangular steel tube joist or HSS joist 16 which would be the same length as the bar joist 6, 6a, that is, about 30 to 50 feet (9.1 -15.2 m). To make HSS joist 16, you take a piece of rectangular HSS steel which is hollow and open at both ends (the HSS piece is about 30-50 feet (9.1 -15.2 m) long). Then you weld a steel plate over each end so that you end up with a sealed, hollow steel box about 30-50 feet (9.1 -15.2 m) long. Fig. 4 shows this hollow box (not to scale), having sides 16a (top), 16b (front), 16c (back), 16d (bottom) from the HSS piece, and the two steel plates 16e and 16f which have been welded to seal the ends, to form the sealed box. HSS joist 16 is then used in Fig. 1 in place of joist 6.

The problem with the bar joist 6, 6a is that it has too many flat surfaces to collect dust and too many nooks and crannies to collect microbial growth and dust and which can't be reached to clean.

The problem with the rectangular steel tube joist or HSS joist 16 is that, although it has few nooks and crannies, it is expensive because of all the steel used to make the sealed box. Also, this design with HSS joists 16 still uses girders 4, (see Fig. 1 ) which are I-beams which collect lots of dust on the horizontal flanges.

SUMMARY OF THE INVENTION

A joist comprising a top chord, a bottom chord and a plurality of web members connecting the top chord to the bottom chord, the top chord being hollow, having a rectangular lateral cross section and having two ends which are sealed, the bottom chord being hollow and having two ends which are sealed. A roof system can include one or more of these joists.

Brief Description of the Drawings

Fig. 1 is a top plan view of steel support members of a roof support according to the prior art which supports a flat roof;

Fig. 2 is a perspective view of a post, girder and joist according to the prior art;

Fig. 3 is a perspective view of a joist according to the prior art;

Fig. 4 is a perspective view of a rectangular steel tube joist according to the prior art;

Fig. 5 is a front elevational view of a double sealed tube with web (DSTVWV) joist according to the invention;

Fig. 6 is a cross-sectional view taken along line 6-6 of Fig. 5; Fig. 7 is an enlarged front elevational view of web member 24c;

Fig. 8 is a cross-sectional view of an alternative embodiment of a bottom chord of a DSTWW joist according to the invention;

Fig. 9 is a cross-sectional view of a portion of a roof system according to the invention; and Fig. 10 is a cross-sectional view of an alternative embodiment of a portion of a roof according to the invention.

Detailed Description of Preferred Embodiments of the Invention

In the description that follows, when a preferred range, such as 5 to 25 (or 5-25) is given, this means preferably at least 5 and, separately and independently, preferably not more than 25. As used herein and in the claims, DSTWW joist means double sealed tube with web joist.

The present invention preferably includes 2 parts. First, you replace each bar joist/HSS joist 6 (in Fig. 1) with a double sealed tube with web joist; that is, with a DSTWW joist. Second, you replace each girder 4 (in Fig. 1) with a larger version of a DSTWW joist.

Fig. 5 shows a DSTWW joist 18. Joist 18 comprises a top chord 20, a bottom chord 22 and web members 24a, 24b, 24c, 24d, 24e, 24f, 24g, 24h. DSTWW joist 18 is a conventional length, with the joist 18 and the top chord 20 being typically about 25-60 or 30-50 feet (7.6-18.3 or 9.1 -15.2 m) long. The gap between top chord 20 and bottom chord 22 is preferably about 18-42 or 24-36 inches (45.7-106.7 or 61 - 91 .4 cm). (Fig. 5 is for illustration only and is not to scale; there will usually be more than 8 web members in a 30-50 foot (9.1 -15.2 m) DSTWW joist 18). Preferably all the triangles formed between the chords are isosceles triangles. As shown in Fig. 5, the chords and web members define a series of alternately inverted triangle-shaped spaces, preferably isosceles triangles, along the length of the joist (like a Neville truss); alternatively the triangles are equilateral triangles (like a Warren truss). Each web member 24a etc. is preferably about 20-36, 20-30, or 24-36, or about 24, inches (50.8-91 .4, 50.8-76.2, or 61 -91 .4, or about 61 , cm) long. Fig. 6 shows a cross sectional view of the DSTWW joist 18 taken along line 6-6 of Fig. 5. As shown in Fig. 6, top chord 20 is a square HSS tube (alternatively, it can be rectangular); the ends 20a, 20b have been sealed by welding a square steel plate (alternatively, it can be rectangular) to seal each end. As shown in Fig. 6, top chord 20 has a square and a rectangular lateral cross section. Top chord 20 is preferably about 2-4 or about 3 inches (5.1 -10.2 or about 7.6 cm) wide and about 2-4 or about 3 inches (5.1 -10.2 or about 7.6 cm) high (outside dimensions) and with about 0.25 inch (about 0.64 cm) wall thickness. As shown in Fig. 6, bottom chord 22 is a circular HSS steel pipe preferably about 2-5 or 2.5-4.5 or about 3.5 inches (about 5.1 -12.7 or 6.4-1 1 .4 or about 8.9 cm) in outside diameter; and about 0.2-0.25 inch (about 0.51 -0.64 cm) wall thickness; the ends 22a, 22b have been sealed by welding a circular steel plate to seal each end. Alternatively, bottom chord 22 can be a square HSS tube 26 (of course sealed at each end like chord 22) (see Fig. 8) which has been tilted to a 45° angle, so that dust will tend to fall off and can be easily washed off. Alternatively, HSS tube 26 can be rectangular, optionally tilted about 30-60° for the same reasons. HSS tube 26 is preferably the same width, height and thickness as top chord 20.

Each web member 24a-h is a piece of round steel tube having a circular cross section wherein each end has been squashed flat. Web member 24c has a central section 28 which is a round pipe preferably about 1 -3 or 1 -2 inches (2.5-7.6 or 2.5-5.1 cm) outside diameter; web member 24c has a top end 30 and a bottom end 32, wherein the last inch (2.54 cm) or so of the circular pipe has been squashed flat so that the respective ends can be more easily welded to the bottom of the top chord 20 and to the top of the bottom chord 22 (thus sealing the ends of the hollow pipe) and provides a more sanitary connection. Top end 30 is welded to the bottom of top chord 20 with weld beads 34, 36; bottom end 32 is welded to bottom chord 22 with weld beads 38, 40. In summary, each joist 6 of Fig. 1 has been replaced by a DSTWW joist 18.

Next, with reference to Fig. 1 , you replace each girder 4 with a DSTWW joist, except that this DSTWW joist is preferably much larger and stronger than DSTWW joist 18. See Fig. 9, which shows DSTWW joist 42, which is larger and stronger than the 2 smaller DSTWW joists 18 (described in Fig. 5) which it supports as shown in Fig. 9. DSTWW joist 42 has the same construction and dimensions and the same triangles as DSTWW joist 18, but it is preferably larger; it has a top chord 44, bottom chord 46 and a web member 47 which is a round pipe, which has a central portion 48. Both ends of chords 44, 46 are sealed like chords 20, 22. Top chord 44, bottom chord 46 and joist 42 are preferably about 25-60, 30-60 or 40-50 feet (7.6-18.3, 9.1 -18.3 or 12.2-15.2 m) long; each web member 47 is preferably about 20-60, 34-60 or 36-56 or 36-45 or 40-48 inches (50.8-152, 86.4-152 or 91 .4-142 or 91 .4-1 14 or 101 .6-122 cm) long. Web member 47 has a top end 50 and a bottom end 52, wherein the last inch (2.54 cm) or so of the circular pipe has been squashed flat just like ends 30, 32 so that each end 50, 52 can be more easily welded to the top chord 44 and bottom chord 46 via weld beads 53, 54, 55, 56 and provides a more sanitary connection. Bottom chord 46 may alternatively be a square or rectangular HSS tube that may optionally be tilted at about 30-60° or 45°, similar to chords/tubes 22 and 26 described above. Top chord 44 is preferably about 2-5 or 2-4 or about 3 inches (5.1 -12.7 or 5.1 -10.2 or about 7.6 cm) wide and about 2-5 or 2-4 or about 3 inches (5.1 -12.7 or 5.1 -10.2 or about 7.6 cm) high (outside dimensions) and about 0.25 inch (0.64 cm) wall thickness; bottom chord 46 can be the same as bottom chord 22 or about 10-25- 50% larger, web member 47 can be the same as web member 24a or about 10-25-50% larger.

To make web members 24a-h and 47, preferably take a long length of pipe and, every 20-36 (for 24a-h) or 34-60 (for 47) inches (50.1 -91 .4 or 86.4-152 cm), squash flat an about 3 inch (7.6 cm) section. Then cut the pipe at a 45° angle in the middle of the 3 inch (7.6 cm) flat section. The yields the web members 24a-h, 47 with a flat section about 1 .5 inches (3.8 cm) long at each end with a 45° cut or tip, with no waste of material.

Fig. 9 shows metal flanges 72, 74 fixed to the sides of top chord 44 and corresponding flanges 76, 78 fixed to the ends of top chords 20, 20 so that DSTWW joists 18, 18 can be mounted on DSTWW joist 42. Fig. 9 also shows the flat roof which is above the girders and joists. First, on top of the joists 18, place a large flat layer of 3 inch (7.6 cm) insulated metal panels (IMP) 58; each IMP panel has a 3 inch (7.6 cm) core of foam insulation and a top skin and a bottom skin of galvanized steel (or steel with baked enamel finish). On top of the layer of IMP panels 58, place a flat layer 60 (not to scale) of thermoplastic polyolefin (TPO) single ply roof membrane or similar material. Preferably, a 0.5 inch (1 .3 cm) isolation board layer 70 (see Fig. 10) is placed between the TPO membrane 60 and the IMP panel layer 58. The isolation board can be a polyisocyanurate rigid foam insulation board as known in the art. Other flat roofs known in the art can be used.

To prevent dust and particles collecting between the top 68 of the top chord 44 and the bottom of the IMP panel 58, seal the front and back edges 62, 64 of the top 68 to the bottom of the IMP panel layer 58 with sealant; similarly, seal the front and back edges 66, 67 (see Fig. 6) of the top chord 20 of each DSTWW joist 18 to the bottom of the IMP panel layer 58 with sealant (see Figs. 6 and 9).

A roof system comprises roof support and roof. The roof support comprises the traditional girders and joists (or the DSTWW joists of the present invention) which support the roof. The roof comprises layers of material like IMP panels and TPO membrane (which are supported by the roof support) to keep snow, rain, weather, etc. out of the building.

The roof system of the present invention preferably comprises (a) a plurality of first joists (preferably like DSTWW joists 42) extending substantially horizontally and substantially parallel to each other (as shown in, e.g., Figs. 1 and 9) and (b) a plurality of second joists (preferably like DSTWW joists 18). Each first joist acts as a conventional roof girder like girders 4; each second joist extends between and is supported by a pair of adjacent first joists, similar to or like the joists 6 extend between and are supported by a pair of adjacent girders 4 in Fig. 1 .

As a result of the roof system using large DSTWW joists 42 for the girders 4 and smaller DSTWW joists 18 for the joists 6, you have a food or pharmaceutical plant roof support with almost no flat surfaces and almost no nooks and crannies. In particular, each DSTWW joist 18, 42 is hollow and sealed, in that each top chord 20, 44, each bottom chord 22, 46 and each web member 24a-h, 47 is hollow and sealed, and there are almost no flat surfaces where dust, grease and food particles can collect. The invented roof support and roof system is easier to wash, clean and sanitize. The roof system can preferably include a flat roof with minimal pitch for rainwater drainage and be a roof system of a food manufacturing plant or a pharmaceutical manufacturing plant.

The invention can be used preferably for roofs for the following types of food plants, or plants processing or making these goods: bakery or bakery goods, meat packing or processing, fruits, vegetables, sauces, canned food, bottled food, pet food, cereals, beverages, snack foods, candy, jams, jellies, etc. The invention can be used preferably for pharmaceutical plants making or processing injectables, oral medications, ointments, salves, lotions, etc. and for aseptic processing, wet processing, sterile product filling, tissue culture manufacturing, equipment manufacturing, reagent production, packaging, coating and filling operations, etc. and for electronics plants making electronic chips, electronic components and other electrical devices and goods. The invention can be used in any plant where it is necessary to minimize dust and particles and to sanitize the area.

While the invention has been described with reference to the preferred embodiments, it is understood that various changes can be made and equivalents may be substituted for elements thereof without departing from the scope of the invention.