Grease absorption box for roof use

A grease absorption curb system for use in conjunction with roof top cooking exhaust fans to prevent grease which accumulates around restaurant exhaust fans from degrading roof top materials. The curb comprises a plurality of durable, lightweight, non-biodegradable blocks which are releasably joined together by a tongue and groove system to define a perimeter curb around the exhaust fan, with at least some of the blocks having drain tubes to allow water to drain from within the perimeter curb system to outside of the curb system.

BACKGROUND OF THE INVENTION 
Restaurants and fast-food facilities do much cooking in grease. Typically 
the deep fat fryers have a hood which exhausts the vaporized grease away 
from the fryer via an exhaust fan and out to the roof area. However, the 
grease does deposit on the exhaust fan and also on the roof of the 
restaurant. Over a period of time this grease gradually builds up and 
collects about the fan structure, the fan housing, and as well on the 
roof. If not removed in time, the grease will become highly corrosive to 
the roofing materials, eventually causing deterioration of shingles and 
rotting of the underlying boards. Accumulated grease is also known to 
provide a significant fire hazard, and since it makes the surrounding area 
highly slippery, also a safety hazard. There is, therefore, a continual 
need to prevent such grease accumulation so that the attendant problems 
associated therewith can be eliminated. 
In the past, it was known to arrange wooden sandboxes beneath the exhaust 
fan housing on a restaurant roof. However, this is not very satisfactory 
in that it requires frequent and troublesome maintenance. Particularly the 
sandbox itself is susceptible to the same roof rot caused by grease. Other 
forms of grease collectors have been proposed, including complex systems 
which use solvent catch basins, see for example U.S. Pat. No. 4,635,617 
issued Jan. 13, 1987. The trouble with solvent catch basins is that they 
are simply not practical. This is true because they are extremely 
expensive, and in areas where there is subjection to wide ranging 
temperature variations such as in the Northern parts of this country, 
there may be a distinct temperature effect, not only the grease but also 
on the solvent system. Moreover, solvent systems are difficult to install 
and expensive. Simply put, the cost outweighs the benefits achieved. 
There is, therefore, a continuing need for the development of a simple, 
reusable, and economical sandbox type system, which achieves the economic 
advantages of a wooden sandbox without the attendant inherent problems in 
sandbox systems. This invention has as its primary objective the 
fulfillment of this need. 
Yet another objective of the present invention is to develop a perimeter 
curb system for use in roof top traps for grease, which system is 
lightweight, durable, noncorrosive with exposed grease, and which allows 
collected water to weep away so that there is collection of grease only. 
A further objective of the present invention is to provide a universally 
usable perimeter curb system which can be easily modified on site for the 
variety of differing types of roof top fan exhaust systems. 
An even further objective of the invention is to provide a perimeter curb 
system which is long lasting, durable, and economical. 
The method of accomplishing these and other objectives of the present 
invention will become apparent from the detailed description which follows 
.

DETAILED DESCRIPTION OF THE INVENTION 
Looking first at FIGS. 1 and 2, in FIG. 1 particularly there is shown a 
perspective view of the grease absorption curb system, referred to 
generally at 10. The curb system 10 is comprised of a plurality of 
individual blocks, with 12 representing an intermediate or center block 
and 14 representing a corner block. Each of the blocks has at one end a 
groove 16 and at the other end a tongue 18. Thus, a series of the blocks 
may be joined to form the perimeter curb system 10. The size of the 
perimeter curb can vary, of course, depending upon the number of blocks 
used. Thus, a curb system can be built to accommodate fans of differing 
size. 
The details of construction of one of the blocks can be seen by looking at 
FIG. 2 which is a sectional view of side block 12 along line 22 of FIG. 1. 
It can be seen that side block 12 is a shell 20 which defines a hollow 
interior portion 22. The shell 20 can be comprised of any durable, 
lightweight, non-biodegradable, and moldable plastic material. Suitable 
materials are made of moldable polymeric resins. One especially suitable 
material is reinforced fiberglass. However, the shell may be made from 
moldable polymeric resinous materials other than fiberglass and one can 
use polyvinyl chloride, polyethylene, polypropylene, styrene, and other 
moldable resinous materials as well. The important point is that the 
material is non-biodegradable, durable, and lightweight. The term 
non-biodegradable as used here refers to corrosion resistance to grease. 
It is to be distinguished from wood which is known to rot after continued 
exposure to grease. The shape of the shell 20 of block 12 is generally 
illustrated in FIG. 2. It has a bottom or flattened perimeter edge 26, a 
vertical exterior wall 28 joined to a top 30, a downwardly extending 
interior wall 32 joined to an interior shoulder 34 which is at a sloping 
angle, preferably at 45.degree. to downwardly extending into interior wall 
32. Sloping wall 34 joins a flattened perimeter edge 36 which is of like 
construction to flattened perimeter edge 26. Thus, the block will rest 
against a horizontal surface on flattened perimeter edges 26 and 36 
respectively. This precise configuration of shell 20 is not essential but 
is highly preferred. 
FIG. 3 shows a plan view of a corner block 14. It is of similar shape to 
intermediate or side block 12, except that it has a defined 90.degree. 
corner. As also illustrated in FIG. 3, corner block 12 has two weep tubes 
38 and 40 which allow water that drains downwardly through the material 
filling the curb system to be drained away from the bottom, through the 
shell 20 of the blocks, from where it spills on to the roof and is drained 
away in conventional fashion. In this way the improved sandbox of the 
present invention does not hold substantial amounts of water which must be 
manually drained away. Weep or drain tubes 38 and 40 can be separately 
installed in the blocks or may be integrally molded therewith. One 
satisfactory way is to simply drill and mount within the blocks a quarter 
inch inside diameter polyvinyl chloride tube. FIG. 4 illustrates the 
mounting of the weep tube in detail and is a view taken along line 44 of 
FIG. 3. 
FIG. 5 represents an elevated perspective view with parts broken away 
showing the completely installed perimeter curb system of the present 
invention. The system 10 is mounted on a roof top to define a perimeter 
edge around a roof top exhaust fan. In actual installation the individual 
blocks forming the system are taken to the roof, and put together in 
tongue and groove fashion around the exhaust fan in order to see how many 
pieces and in what particular dimension they will be put together. After 
this rough assembly around the roof fan, the corner locations are marked 
and the grease absorption curb is then taken apart, a conventional 
polymeric adhesive is applied to the tongue and groove joints and they are 
reassembled in the same location. The curb is now cemented together. The 
bottom of the curb system is filled with pea gravel 42 to a depth of about 
2 inches. The pea gravel or pea rock are small rocks having diameters of 
from about 3/8 inch to about 1/2 inch ideally. On top of the bottom layer 
of pea rock 42 is a flexible sheet of material, for example 6 milliliter 
visqueen 44. The visqueen 44 is perforated so that water may drain 
therethrough. On top of visqueen layer 44 is about 3 inches of grease 
absorption material, for example medium grade silica sand 46. Once 
installed the grease catcher works in the following manner. Grease 
expelled from the interior of the kitchen in a vaporized fashion goes up 
through the vent and accumulates on and around the exhaust fan. Eventually 
it drips down from the fan and is caught in the grease absorption media 
(silica sand) 46. Water is not accumulated because water that does come 
off drains through the sand 46, passes through the perforations and 
visqueen sheet 44, down into the pea gravel 42. It drains through the pea 
gravel 42 and out through the weep tubes 38 from where it can drain away 
off of the roof in conventional fashion. Periodically as the amount of 
grease that accumulates in the sand 46 is such that it becomes nearly 
saturated, the sand is removed and discarded, if necessary a new visqueen 
sheet 44 laid down and the collection process repeated. 
After noticeable periods of long usage, there is no evidence of roof 
destruction from the use of the present system. It can therefore be seen 
that the system accomplishes all of its stated objectives.