Waste grease collection tank and method for its use

A double walled waste grease collecting tank for use in collection system in which the collecting tank is partially submersed in a hot water bath to soften or melt grease at the container walls to facilitate emptying the solid or semi-solid collected grease. The double walled collecting tank has fill openings in its outer wall adjacent its bottom which are normally closed by removable plugs. The plugs are removed to enable hot water to enter the space between the double walls when the tank is submerged into the hot water bath, then replaced when the tank is emptied. Closable vent openings provided adjacent the top of the outer wall are opened to permit rapid filling and emptying the air space between the double walls, and closed when the tank is emptied.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved collection tank for the in situ collection of waste grease such as cooking oils or grease, and to a method of collecting the grease by elevating the tank and lowering it into a hot water bath to warm the walls and facilitate dumping of the grease.

2. Description of the Prior Art

It is well known to collect used or waste greases in collection or holding tanks at the point of use such as at a fast food restaurant or the like, then to collect the waste grease from such tanks for processing and/or recycling. U.S. Pat. No. 4,450,828 and U.S. Pat. No. 5,718,220 disclose waste grease tanks used for collecting grease products, and a process for collecting the grease by a transport truck including a heating bath for heating the tank so that the grease can be easily dumped.

With reference toFIG. 4, which is a copy of FIG. 1 found in U.S. Pat. No. 4,450,828, the numeral11generally designates a truck, which has conventional wheels13and a cab15associated with a conventional engine (not shown). The cargo part17is a large tank for holding the dumped grease. In the bottom of the tank17there is a tube by which steam can be fed through in-out openings20to melt the collected grease from drainage (at a warehouse) through a valved outlet coupler21.

The mechanism for lifting, immersing, and dumping the containers comprises a pair of lever arms24simultaneously swung by hydraulic cylinders26. The upper ends of the arms24are bridged by a bar and by a shaft having winch spools29thereon for winding and unwinding cables or chains31thereon. The winch29is opened by a reversible hydraulic motor33of know construction.

The on-site left-there container35is of a size of equal several of the barrels previously employed. It has downwardly inwardly tapered sides to facilitate dumping the semi-sold grease block after its sides are heat-softened by immersion of the container in a hot-water-bath vat located, for example, at the rear of the truck (heated in known manner by an immersion electric heater or by hot-water or exhaust-gas coils, not shown). The container35has lift lugs39and dumping-tilting lugs40.

The grease-dumping operation is best illustrated inFIG. 4. Firstly the container is sitting at ground level (left phantom). Secondly, it is winch-lifted to the full-line-shown position. Thirdly, it is lowered into the hot-water bath at the rear of the truck. Fourthly, it is again lifted and is swung to the last (right) position shown inFIG. 4. Fifthly, it is dumped by lowering the container35, so that the lugs40enter J-shaped pockets53, which are welded to the inner faces of the lift levers24. After this, further lowering of the container35makes it pivot around said lugs40to dump its grease contents.

Under certain conditions, environmental protection considerations now require waste grease collection tanks to have double walls to guard against spillage or leakage in the event of an accidental rupturing or puncturing of the tank wall. However, such double-walled construction provides an insulating air space between the inner and outer container walls which makes submergence into a hot water bath particularly ineffective in warming the inner container wall to facilitate dumping of the solid or semi-solid waste grease.

It is therefore an object of the present invention to provide an improved double-walled collection tank which facilitates emptying of waste grease from the tank.

It is another object to provide a double-walled collection tank which may be quickly and effectively heated by dipping into a hot water bath to facilitate emptying of the solid or semi-solid grease stored therein.

Another object is to provide an improved method of emptying solid or semi-solid waste grease from a double-walled collection tank.

SUMMARY OF THE INVENTION

In the attainment of the foregoing and other objects, an important feature of the present invention resides in providing an improved double-walled waste grease collection tank, and an improved method for heating the tank and dumping the waste grease by use of a collection truck of the type disclosed, for example, in the above mentioned U.S. Pat. No. 4,450,828 and U.S. Pat. No. 5,718,220, in which the collection tank is dipped into a container of hot water for melting or softening the grease at the tank surface to facilitate dumping. The disclosures of U.S. Pat. No. 4,450,828 and U.S. Pat. No. 5,718,220 are incorporated herein by reference.

The improved grease tank of the present invention comprises spaced inner and outer container portions each having a bottom wall and upwardly extending sidewalls which, container portions are rigidly joined and retained in spaced relation to provide a defined space therebetween. The inner and outer container portions are joined at the top by a continuous flange or top wall portion. The sidewalls of the inner container portions may incline slightly outwardly from the bottom wall to facilitate dumping.

In order to enable use of a double-walled collection tank of the invention with a waste grease collection truck in which the tank is partially submerged in hot water, the outer container wall of the tank is provided with one or more openings which may be closed with a removable plug or other closure element. In use of the tank for in situ collection of waste grease, a removable closure is mounted in the opening to provide a sealed outer container meeting the requirements of environmental protection regulations. When the tank is to be emptied, it is prepared for removal and emptying at the collection site by removing the removable closure plugs, whereupon it is then lifted into position above the hot water bath on the collection truck. The tank is then lowered into the hot water bath so that hot water flows through the apertures in the outer wall of the tank into the space between the double walls to heat the inner wall and thereby melt or soften adjacent solid or semi-solid grease. The tank is then lifted above the hot water bath and the water in the double-walled tank portion is permitted to drain from the openings before the waste grease is dumped in the conventional manner shown in U.S. Pat. No. 4,450,828 and U.S. Pat. No. 5,718,220. The tank is then returned to its previous position and the removable closures are then replaced to provide a sealed double-walled tank.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, an improved waste grease collection tank according to the invention is designated generally by the reference numeral10inFIGS. 1 and 3and includes an inner container portion12and an outer container portion14, each of generally rectangular configuration adjoined at or near their opened tops by a continuous, stepped flange-like top wall16to retain the inner and outer containers12and14, in spaced relation to one another to define an open space18therebetween. Preferably the inner and outer container portions12and14, are each formed of substantially flat steel plates continuously welded, although the respective containers can be formed by other means such as by deep drawing.

The inner container portion12, has opposed upwardly extending and preferably slightly outwardly inclined sidewalls20,22, end inner walls24, only one of which is shown inFIG. 1, and a substantially flat bottom wall26. Similarly, outer container14portion comprises upwardly extending sidewalls28,30, opposed end walls each spaced outwardly from the end walls24, and a bottom wall32. The stepped flange16provides a ledge34which serves as a seat for a suitable lid or cover (not shown) for the tank.

The outer container portion14is provided with a plurality of closable openings36formed in the side- and/or end walls thereof adjacent to its bottom wall and one or more vent openings38adjacent its top edge.

The openings36serve as fill openings to permit hot water to enter the space18when the collection tank is submersed in the hot water bath carried by a collection truck to fill the space18to the level of submergence of the tank. To facilitate this filling, air in the space18can escape through the vent openings38.

In use, in order to provide the double-walled environmental protection feature, the fill openings36are closed by removable closures or plugs until the tank is to be emptied. Thus, as shown inFIG. 2, the wall30may be provided with a threaded weldment40which will normally be closed by a removable threaded plug42. Alternatively, the fill holes36may be sealed by a quick release expanding plug (not shown) suitable to maintain the fluid tight integrity of the outer container portion14. Also, vent openings38may, if desired, be closed by removable closure members, for example, as shown inFIG. 2.

The improved collection tank according to the invention is disposed normally at the place of use to collect waste grease. During this time, the fill openings36are sealed by the closure members42, and if desired, the vents38may also be closed. When the full tank is to be emptied, the grease collection tank is moved into the collection position and the fill plugs42are removed. At the same time, if vent closures are used, those closures are also removed. The filled tank is then lifted and lowered into the hot water bath carried by the collection truck so that the hot water flows through the openings36to fill the space18to the level of submersion. The hot water in contact with the walls of the inner container portion12quickly melts or softens the portion of the solid or semi-solid grease in the container adjacent the walls. The tank is then lifted and held above the hot water bath for a sufficient time for the water to drain from the fill openings36. The container is then moved into a position over the waste grease transport tank on the collection truck, and dumped in the conventional manner. The tank is then lowered and returned to the in situ collection site, whereupon the drain plugs42and vent plugs are replaced. Thus, one can see that providing direct contact of the hot water bath with the inner wall of the double-walled waste grease collection tank speeds the collection tank emptying process.

While a preferred embodiment of the invention has been disclosed and described, it is to be understood that the invention is not restricted solely thereto but rather that various modifications may be made without departing from the spirit and scope of the invention.