Roof curb structures and methods of manufacture

Roof curb structures include side shells made by cutting a series of transversely aligned V-shaped notches and straight slots along top and bottom edges of a continuous length of sheet metal strip material at spaced apart intervals corresponding to the length of each side of the side shells to be formed therefrom. Then the strip material is cut to length corresponding to the length of one, two or four sides of the side shells and the top and bottom edges are roll formed in opposite directions to form oppositely extending top and bottom flanges. Next the severed lengths of strip material are folded at each transversely aligned intermediate notch and slot (if the length is greater than the length of one of the sides) to form continuous right angle corners at such intermediate notches and slots, and the ends of such strip material are either seam welded together or the ends of additional lengths of strip material are fitted and seam welded together to form box-like shells having inturned top flanges and outturned bottom flanges. Then the outturned bottom flanges of the shells are positioned against four identical bottom strips that extend a substantial portion of the length of the outturned bottom flanges and beyond one end into underlying relation to an end of the next adjacent outturned bottom flange, and the outturned bottom flanges and the next adjacent outturned bottom flange are spot welded to the same bottom strips to form rigid bottom supports for the shells.

FIELD OF THE INVENTION 
This invention generally relates to roof curb structures for mounting 
ventilators on the roof penetrations of buildings and methods of making 
same. 
BACKGROUND OF THE INVENTION 
Roof curbs are commonly used for mounting ventilators on roof penetrations 
of buildings. However, existing roof curbs are relatively expensive to 
manufacture and difficult to make square and precise for dimensional 
stability because of the relatively large number of parts that comprise 
the roof curbs including particularly the side shell and curb bottom. As 
an example, one such existing side shell and curb bottom is made out of a 
total of twenty different pieces. 
SUMMARY OF THE INVENTION 
The roof curb structures of the present invention including particularly 
the side shells and curb bottom consist of substantially fewer parts than 
previous known roof curb structures, making them less expensive to 
manufacture and easier to make square and precise for greater stability 
and dimensional uniformity. 
In accordance with one aspect of the invention, the side shell and bottom 
of the roof curb structure for most sizes (for example up to 40 inches 
long on a side) consists of a total of four pieces, e.g., a one piece side 
shell having a single weld seam and a bottom made out of four identical 
(and thus interchangeable) pieces. 
In accordance with another aspect of the invention, the side shells and 
bottoms for larger size roof curbs (for example, exceeding 40 or 80 inches 
on a side) consist of a total of six or eight pieces, e.g., a two or four 
piece side shell having two or four weld seams, respectively, and a four 
piece bottom. 
In accordance with another aspect of the invention, an optional damper tray 
consisting of four identical (and thus interchangeable) pieces is provided 
for the roof curbs. 
In accordance with another aspect of the invention, the roof curb 
structures include a simple and effective means of mounting insulation on 
the interior surface of the side shells. 
In accordance with another aspect of the invention, an efficient, cost 
effective method is provided for making the side shells for such roof curb 
structures from a continuous length of sheet metal strip material with a 
minimum amount of cutting, forming and welding. 
To the accomplishment of the foregoing and related ends, the invention, 
then, comprises the features hereinafter fully described and particularly 
pointed out in the claims, the following description and the annexed 
drawings setting forth in detail certain illustrative embodiments of the 
invention, these being indicative, however, of but several of the various 
ways in which the principles of the invention may be employed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now in detail to the drawings, and initially to FIGS. 1 and 2, 
there is shown a preferred form of roof curb structure 1 in accordance 
with the present invention including a box-like side shell 2 having four 
sides 3 made out of a suitable sheet metal such as galvanized steel of the 
required thickness (18 gauge being typical). The length and height of the 
sides 3 may vary depending on the size of roof curb structure required for 
a particular application. Extending inwardly from the top edge of each 
side 3 is a top flange 5 (see FIG. 2). At the inner edge of the top flange 
5 is a downturned lip 6 for added rigidity and to help support and retain 
insulation against the interior surface of the side shell 2 as described 
hereafter. 
Extending outwardly from the bottom edge of each side 3 is a bottom flange 
8. Attached to the bottom flange 8 is a bottom subassembly 9 which as best 
seen in FIG. 3, consists of four identical (and thus interchangeable) 
sheet metal strips 10 each having an upturned lip 11 extending along the 
inner edge from one end toward the other end. The upturned lips 11 have a 
length substantially corresponding to the length of the downturned lips 6 
of the side shell 2, whereas the bottom strips 10 have a length 
substantially equal to the length of the bottom flanges 8. This permits 
the four bottom strips 10 to be fitted together in box-like fashion with 
the ends of the upturned lips 11 butted up against each other and the 
protruding length of each bottom strip butted up against the end of the 
next adjacent bottom strip and secured together as by tack welds 12 as 
shown in FIG. 3. 
Alternatively, the ends 14 of the bottom strips 10' may also be made to 
extend a short distance beyond the associated lip 11' into underlying 
relation with the end of the next adjacent bottom strip so that the 
overlapping ends may be secured together as by spot welds 12' as shown in 
FIG. 3A. Otherwise, the bottom subassembly 9' shown in FIG. 3A is 
substantially the same as the bottom subassembly 9 shown in FIG. 3, and 
the same reference numerals followed by prime symbols are used to 
designate like parts. 
Also, if desired, a damper tray 15 made of four identical (and thus 
interchangeable) sheet metal strips 16 may optionally be mounted within 
the opening defined by the four upturned lips 11 of the bottom strips 10 
for attaching a back draft damper (not shown) to the roof curb to keep air 
from blowing back into the building through the roof penetration when the 
ventilator is turned off. As best seen in FIG. 3, each damper tray strip 
16 has a length substantially equal to the interior spacing between 
opposed upturned lips 11 on the bottom strips 10 less the width of the 
damper tray strips 16. This allows the damper tray strips 16 to be fitted 
within the box-like opening defined by the upturned lips 11 of the bottom 
strips 10, with one end of each damper tray strip 16 pressed up against a 
respective upturned lip 11 at each corner and the other end of each damper 
tray strip butting up against an inner edge of the next adjacent damper 
tray strip. Extending along the outer edge of each damper tray strip 16 is 
an upturned lip 17 that is pressed up against an adjacent upturned lip 11 
of the bottom strips 10 for securing the damper tray strips 16 to the 
bottom strips 10 as by spot welding the respective upturned lips 17 and 11 
together at spaced apart intervals along the length thereof. 
Referring further to FIGS. 1 and 2, the bottom strips 10 have outer 
portions 18 that underlie the outturned bottom flanges 8 of the side shell 
2 and inner portions 19 extending inwardly of the sides 3 of the side 
shell 2 in vertically spaced relation to the inturned top flanges 5 of the 
side shell with the upturned lips 11 on the inner edges of the bottom 
strips 10 in substantial vertical alignment with the downturned lips 6 on 
the inner edges of the inturned top flanges 5. This facilitates easy 
positioning of a continuous strip of insulation 20 around the inner 
periphery of the shell 2 between the inturned top flanges 5 and inner 
portions 19 of the bottom strips 10 and retention therebetween by the 
downturned and upturned lips 6 and 11 as shown in FIG. 2. 
The outturned bottom flanges 8 of the shell sides 3 have squared off ends 
(see FIG. 1). Also, the bottom strips 10 have a length substantially equal 
to (or slightly greater than) the length of the outturned bottom flanges 8 
as aforesaid. Thus, when the outer portions 18 of the bottom strips 10 are 
placed in underlying relation to the outturned bottom flanges 8 with their 
outer edges in substantial alignment with each other and the upturned lips 
11 on the bottom strips 10 oriented symmetrically within the interior of 
the side shell 2 in substantial vertical alignment with the downturned 
lips 6 of the side shell, the bottom strips 10 will extend a substantial 
portion of the length of the outturned bottom flanges and beyond one end 
with their protruding portions 18 in underlying relation to the ends of 
the next adjacent outturned bottom flanges. This has the advantage that 
when the outturned bottom flanges 8 are spot welded to the bottom strips 
10 at spaced apart intervals along the lengths thereof, the spot welds 22 
adjacent the corners will secure the ends of adjacent outturned bottom 
flanges to the same bottom strips adjacent the corners to tie the shell 
sides 3 together at each corner to provide a more rigid, straight sided 
profile for the side shell. 
Extending along the inturned top flanges 5 of the side shell 2 are wood 
nailers 23 which may be secured in place as by driving spiral shank nails 
24 through the tops of the wood nailers into the inturned top flanges as 
shown in FIG. 2 and in the sides of the wood nailers adjacent one end as 
shown in FIG. 1 into the end of the next adjacent wood nailer. 
FIG. 4 schematically shows a preferred sequence of manufacturing the side 
shells 2 for the roof curbs 1 of the present invention from a continuous 
length of sheet metal strip material 30 with a minimum amount of cutting, 
forming and welding. First a supply coil 31 of the strip material 30 is 
fed from a decoiler 32 which pays out the strip material. Then the strip 
material is fed through a notching mechanism 33 that cuts transversely 
aligned V-shaped notches 34 and straight slots 35 in the top and bottom 
edges of the strip material as shown in FIG. 5 after each indexing 
movement of the strip material which corresponds to the length of each 
side of the side shells to be formed from the strip material. Next the 
strip material 30 is cut to length and conveyed by a feed conveyor 36 to a 
roll former 37 that roll forms the top and bottom edges of each severed 
length of strip material in opposite directions at the full depth of the 
notches 34 and slots 35 to form the top and bottom flanges 5 and 8 along 
the top and bottom edges as well as the downturned lips 6 along the inner 
edges of the top flanges 5 as schematically shown in FIGS. 6 and 7. Then 
the severed length 38 of strip material 30 is conveyed to a tangent former 
40 where the severed length of strip material is sequentially folded 
(e.g., formed) along the center of each transversely aligned notch 34 and 
slot 35 intermediate the ends of each severed length of strip material in 
the direction of the top flanges 5 to form continuous right angle corners 
41 with the adjacent edges 42, 43 of the top flanges 5 in abutting 
engagement with each other as schematically shown in FIGS. 8 through 11. 
Depending on the required length of each side 3 of the side shells 2 and 
the length of the feed conveyor 36, the strip material is desirably cut to 
a length corresponding to the length of all four sides as shown in FIGS. 5 
and 12. In that event, after the top and bottom edges have been roll 
formed as previously described, the tangent former 40 will progressively 
fold the strip material three times as schematically shown in FIGS. 9 
through 11 to form a box shape side shell 2 having three continuous right 
angle corners 41 and one non-continuous right angle corner 44 which 
requires one seam weld 45 at the non-continuous corner, as schematically 
shown in FIG. 13. 
For the larger size side shells, the feed conveyor 36 may not be able to 
handle a length of strip material corresponding to the length of all four 
sides of the side shells. Where the length of the sides 3 of the side 
shells 2 is such that the feed conveyor 36 can only handle a length of 
strip material corresponding to the length of two sides of the side 
shells, the strip material is cut to length corresponding to the length of 
two of the sides as schematically shown in FIG. 14. After the top and 
bottom edges have been roll formed, the strip is folded at the aligned 
intermediate notch 34 and slot 35 in the direction of the top flanges 5 to 
bring the edges 42, 43 of the intermediate notch 34 into abutting 
engagement with each other to form two sides 3 with one continuous right 
angle corner 41 as shown in FIG. 15. Then two such folded lengths of strip 
material are fitted together to form a side shell 2 having two continuous 
right angle corners 41 and two non-continuous right angle corners 44 which 
must be seam welded together as schematically shown in FIG. 16. 
Where the length of the sides of the side shells is such that the feed 
conveyor 36 can only handle a length of strip material corresponding to 
the length of one side of the side shells, the strip material is cut to 
length corresponding to the length of one side as schematically shown in 
FIG. 17. Then, after the top and bottom edges have been roll formed as 
shown in FIG. 18, opposite ends of four such sides 3 are fitted together 
with the top flanges 5 extending inwardly and the bottom flanges 8 
extending outwardly to form a side shell 2 having four non-continuous 
right angle corners 44 that must be seam welded together as schematically 
shown in FIG. 19. 
If for example the feed conveyor 36 is of a size that can only handle a 
total length of strip material up to 160 inches, as long as the length of 
each side of the side shell is no more than 40 inches, the side shells can 
be made out of a single piece of strip material that is folded three times 
to form a one-piece side shell having three continuous right angle corners 
and just one non-continuous right angle corner that must be seam welded 
together. If the length of each side is greater than 40 inches but less 
than 80 inches, each side shell will have to be made in two pieces each 
including two sides and one continuous right angle corner, and such pieces 
will have to be seam welded together at opposite corners. However, if the 
length of each side is greater than 80 inches, each side shell will have 
to be made out of four separate pieces each having a length corresponding 
to the length of one side of the shell and seam welded together at all 
four corners. As previously indicated, FIG. 13 shows a one piece side 
shell with one seam weld; FIG. 16 shows a two piece side shell with two 
seam welds; and FIG. 19 shows a four piece side shell with four seam 
welds. 
Of course, the feed conveyor equipment could be made large enough to be 
able to handle strips longer than 160 inches, in which event at least one 
and possibly all three continuous corners of the larger size side shells 
could be roll formed in each strip to minimize the number of seam welds 
required to make the side shells. 
Although the invention has been shown and described with respect to certain 
preferred embodiments, it is obvious that equivalent alterations and 
modifications will occur to others skilled in the art upon the reading and 
understanding of the specification. The present invention includes all 
such alterations and modifications, and is limited only by the scope of 
the claims.