Patent application title: Collapsible Fire Pit and Propane Tank Holder
John T. Unger (Mancelona, MI, US)
IPC8 Class: AF24B1181FI
Class name: Stoves and furnaces fireplaces or accessories front barrier or guard
Publication date: 2012-09-06
Patent application number: 20120222668
A fire pit designed to be stored and shipped in a flat configuration, and
assembled without tools in a matter of minutes into a freestanding,
durable structure capable of functioning as well or better than a
non-collapsible fire pit. The fire pit comprises an essentially flat base
with a unique slot and flange structure adapted to receive and support
side panels. The side panels include female sides with vertical corner
members on their side edges that allow flat male sides to mate securely
with the female sides, and with the intersecting edges of the sides both
covered and reinforced for a neat appearance and robust structure. A top
includes a slot and flange structure that fits over and unifies and hides
the upper edges of the sides, completing the assembly.
1. A collapsible structure suitable for use as a fire pit or fire pit
accessory comprising: a base comprising a substantially flat bottom
panel, raised peripheral side edges in a polygonal pattern, and raised
interior flanges generally parallel to and spaced inwardly from each of
the side edges to define receiving slots between the side edges and the
flanges; at least three substantially flat sides having upper, lower, and
side edges; a top comprising an outer frame comprising an inner polygonal
vertical frame spaced outwardly from the inner edge and extending
downwardly from the outer frame in a polygonal array corresponding to the
peripheral side edges of the base, and further comprising interior
vertical flanges generally parallel to and spaced inwardly from the
vertical frame to define joining slots between the vertical frame and the
interior vertical flanges; wherein, the sides fit vertically into the
receiving slots in the base, and wherein the joining slots in the top fit
vertically over upper edges of the sides; and wherein, the base, the
sides, and the top stack substantially flat when disassembled for storage
2. The collapsible structure of claim 1, wherein the sides comprise two female sides, each female side comprising a substantially flat side panel and at least one V-shaped vertical outer corner piece associated with and generally parallel to a vertical side edge of the side panel, the vertical outer corner piece connected to the side edge of the side panel and adapted to receive a side edge of an adjacent side, and two male sides each comprising a substantially flat side panel and two male side edges adapted to be received by the vertical outer corner pieces of the female sides, the two female sides fitting vertically into two of the receiving slots in the base, and the two male sides fitting vertically into two of the receiving slots in the base and into the outer corner pieces of the two female sides.
3. The collapsible structure of claim 1, wherein the base is rectangular and comprises four side edges, and wherein the female sides each comprise two vertical outer corner pieces.
4. The collapsible structure of claim 1, wherein the outer corner pieces overlie the side edges of the female and male panels when the fire pit is assembled.
5. The collapsible structure of claim 1, wherein the female sides are square, and wherein the horizontal edges of one female side mate with the vertical outer corner pieces of the other female side when the female sides are packed substantially flat.
6. The collapsible structure of claim 1, wherein all side edges of the flat panel portions of the fire pit are covered by a perpendicular flange member when the fire pit is assembled.
7. The collapsible structure of claim 1, wherein the raised interior flanges on the base extend less than a full length of the sides and are spaced from both ends of the sides.
8. The collapsible structure of claim 1, wherein the interior vertical flanges on the top extend less than a full length of the sides and are spaced from both ends of the sides.
9. The collapsible structure of claim 1, wherein the corner pieces extend less than a full length of the female side edges such that a free portion of the female side edges is exposed at each end of each corner piece.
10. The collapsible structure of claim 1, wherein the top comprises an opening and an inner edge.
11. A collapsible structure suitable for use as a fire pit or fire pit accessory comprising: a base comprising a substantially flat bottom panel, raised peripheral side edges in a polygonal pattern, and raised interior locking flanges generally parallel to and spaced inwardly from each of the side edges to define receiving slots between the side edges and the flanges; at least three sides, each side comprising a substantially flat side panel and at least two of the sides comprising at least one angled vertical outer corner piece generally parallel to and spaced outwardly from a vertical side edge of the side panel, the vertical outer corner piece connected to the side edge of the side panel, and adapted to receive a free edge of an adjacent side; a top comprising an outer frame comprising an inner edge defining a top opening, a polygonal vertical locking frame spaced outwardly from the inner edge and extending downwardly from the outer frame in a polygonal array corresponding to the peripheral side edges of the base, and further comprising interior vertical locking flanges generally parallel to and spaced inwardly from the locking frame and spaced outwardly from the inner edge to define joining slots between the locking frame and the inner edge; wherein, the sides fit vertically into the receiving slots in the base, with at least one free edge of at least one of the sides located behind a free leg of the vertical outer corner piece of at least one of the other sides, and wherein the joining slots in the top fit vertically over upper edges of the sides, and wherein, the base, the sides, and the top stack substantially flat when disassembled for storage or shipping.
RELATED APPLICATIONS/PRIORITY BENEFIT CLAIM
 The subject matter of the present application is in the field of portable fire pits and propane tank storage containers.
 Portable fire pits made from iron, steel, aluminum, ceramic and other fireproof materials are widely used for outdoor fire containment on lawns, on patios, on decks, in backyards, on beaches, and generally anywhere it is desired to enjoy an open fire without marring the landscape or platform. Fire pits can also reduce the worry associated with having an uncontained fire in such locations.
 Quality fire pits are generally bulky and heavy, and can be difficult and expensive to ship from a manufacturer or seller. While it is known to make campfire "rings" collapsible for portability or shipping, they tend to be light but not very durable or long-lasting, and they lack a bottom plate for lawn and patio use. Heavier-duty fire "pits" with substantial bottom plates or bowls are suitable for long-term lawn and patio use, but are not made to be packed flat for shipping, and they can be difficult to assemble, requiring tools and special fasteners.
 Fire pits typically burn wood, charcoal, and other combustibles, but gas-burning fire pits are becoming more common, in which a gas fire insert or burner, often fueled from a portable propane tank, is installed in the fire pit and supplied with gas from the tank. A problem with gas fire pits, gas grills, and other propane-fueled devices is the unsightly nature of portable propane tanks. Common attempts to hide such propane tanks include homemade solutions such as garbage cans with holes cut in the sides for fuel hoses, and cabinets built into grills, but these tend to be unsightly, and at a minimum they are bulky and thus difficult to store or ship.
 I have invented a box-shaped, heavy-duty fire pit that can be made from thick metal plate such as steel for sustained lawn and patio use, that can be assembled/disassembled easily and quickly without tools, and that packs flat for cost-effective shipping.
 "Box-shaped" is used herein to include any multi-sided (polygonal) shape with three or more substantially flat sidewalls. "Lawn and patio" is used herein to mean any location where a fire pit needs a bottom to protect the underlying platform or ground from burning or scarring.
 My fire pit uses a unique joinery between the sides and the bottom and the top to achieve this functionality. The fire pit has a base comprising a substantially flat polygonal bottom panel, with raised peripheral side edges defining a preferably continuous side edge, and raised interior flanges generally parallel to and spaced inwardly from each of the side edges to define receiving slots between the side edges and the flanges. The raised interior flanges are preferably discontinuous relative to the continuous side edge, preferably extending only partway between the corners of their respective sides and centered on their edges, to facilitate ease of assembly and re-assembly after burning.
 The fire pit has at least three sides, each side comprising a substantially flat side panel, with at least two of the sides preferably comprising at least one angled vertical outer corner piece connected to a side edge of the side panel and generally parallel to and spaced outwardly from and covering the associated side edge, the vertical outer corner piece optionally having a vertical gap or slot between the side edge of the panel and the corner. In a preferred, rectangular form, the fire pit comprises two female sides each with two corner pieces, and two male sides with no corner pieces. The two male sides each comprise a substantially flat side panel with two male side edges adapted to fit the corner pieces on the female sides.
 The fire pit also has a substantially flat top plate with a top opening, and a preferably continuous inner vertical locking frame offset outwardly from the inner edge and extending downwardly from an inside surface of the top plate around the opening in a polygonal array corresponding to the base and the upper edges of the assembled sides. The top further includes preferably discontinuous interior vertical locking flanges generally parallel to and spaced inwardly from the inner locking frame and spaced outwardly from the inner edge to define joining slots between the inner locking frame and the inner edge.
 The base, the sides, and the top plate are substantially flat, and they pack substantially flat for shipping. For assembly, the female sides fit vertically into some of the receiving slots in the base, and the male sides (or those sides with one or more free edges) fit vertically into the other receiving slots in the base and behind the outer corner pieces of the female sides. The joining slots in the top fit vertically over upper edges of the upright assembled sides to lock the sides in place.
 All edges of the top, bottom, and side panels are hidden from view, and framed, by the corner pieces and by the vertical edge and flange structures. This gives the assembled fire pit a consistent, tool-finished look, and also reinforces the fire pit structurally.
 My fire pit construction is also useful for providing sturdy, protective, decorative storage for portable propane fuel tanks of the type commonly used to fuel grills and gas-burning fire pits. By closing or covering the top plate opening and/or providing a door in either the top or a side plate, and by using an existing opening or providing a dedicated hose port, the fire pit alternately functions for propane tank storage. I will refer to this use as a "fire pit accessory". Alternately, the same fire pit used for holding fires in-season can be used for propane tank storage off-season.
 These and other features and advantages of the invention will become apparent from the detailed description below, in light of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 is a perspective view of a fire pit according to the invention, disassembled and packed flat for shipping.
 FIG. 2 is a perspective view of the base from FIG. 1 separated from the remaining disassembled/stacked pieces.
 FIG. 3 is a perspective view of the female side plates from FIG. 1 being assembled to the base plate.
 FIG. 4 is a perspective view of the male side plates from FIG. 1 being assembled to the base plate and female side plates.
 FIG. 5 is a top plan view of the partially assembled fire pit of FIG. 4, with the male and female side plates assembled to the base plate.
 FIG. 6 is a perspective view of the top of the fire pit from FIG. 1 being assembled to the upper edges of the side plates.
 FIG. 7 is a perspective view of the fully assembled fire pit of FIG. 1.
 FIG. 8 is a perspective view of the fire pit of FIG. 7, modified for propane tank storage.
 Referring first to FIG. 1, a disassembled fire pit 10 is shown in exemplary form in order to teach how to make and use the claimed invention. Fire pit 10 includes a substantially flat base 12, substantially flat female sides 14, substantially flat male sides 16, and a substantially flat top 20. The illustrated fire pit 10 is rectangular when assembled, specifically square, with four square side panels and square top and base plates. It will be understood, however, that non-rectangular fire pits with three or more substantially flat sides, are possible. It will also be understood that although the outside edge geometry of the base 12 and top 20 preferably match the polygonal shape defined by the assembled flat sides 14 and 16, they may take other shapes provided they connect the assembled flat sides in the requisite polygonal shape.
 The illustrated fire pit 10 is made from heavy-gauge sheet or plate steel, although other fireproof metals or non-metals or combinations thereof could be used.
 Still referring to FIG. 1, base 12, sides 14 and 16, and top 20 pack essentially flat for shipping, portability, and storage. Female sides 14 each include corner pieces 15 on their edges 14b that are aligned vertically for assembly, and in the square panel embodiment illustrated, the free upper and lower edges 14c and 14e (best seen in FIG. 3) of each female side 14 nest or mate within the corner pieces 15 on the other of the two female sides, due to the outward spacing of the corner pieces from the edges of the flat panel portions 14a, to further reduce the volume of the disassembled and flat-packed fire pit 10. Corner pieces 15 extend less than the full length of sides 14b, leaving exposed portions of edges 14b extending beyond each end of each corner piece.
 FIG. 2 shows base 12 removed from the stack of disassembled fire pit parts and laid flat with its inner side facing up. Base 12 includes a flat bottom plate 12a, raised side edges 12b defining a continuous raised peripheral outer flange, and interior locking flanges 12c generally parallel to and spaced inwardly from the side edges 12b. In the illustrated example, interior locking flanges 12c are formed from L-shaped angle iron welded or otherwise secured to the inner face of bottom plate 12a. Locking flanges 12c define assembly slots 13 between the flanges and the raised side edges 12b. In the illustrated example, flanges 12c are discontinuous relative to side edge 12b, only extending partway along their respective side edges, for example being centered relative to each side edge 12b of base 12 and spaced from each end (corner) of each side edge 12b.
 Base 12 may include other features, including but not limited to one or more holes P for ash removal or use as a fuel hose port, and removable feet/legs and associated structure for attaching the feet/legs.
 FIG. 3 shows the female side plates 14 being assembled to base 12. Free edges 14c are inserted into slots 13 defined between locking flanges 12c and raised side edges 12b. Slots 13 are sized to receive and hold side plates 14 in an upright, freestanding manner without the need for tools or fasteners.
 Female side plates 14 include flat panel portions 14a and optional (but preferred) corner-forming pieces 15 running along their vertical side edges 14b. In the illustrated embodiment, corner pieces 15 are angle iron with one leg 15a welded or otherwise secured to the outer faces of the side plates, and the other leg 15b free. Corners 15c are preferably spaced from edges 14b, creating a gap for receiving the edge of a mating male side. While the structural integrity of the assembled fire pit is assured by the locking flange connections between base 12 and top 20 and the top and bottom edges of the sides 14 and 16, corners 15 can provide some structural reinforcement if toleranced with a close enough fit to the male side edges, and enhance the finished look of the fire pit.
 FIG. 4 shows male sides 16 as flat panels dimensionally identical to panel portions 14a of female sides 14, although the "front" panel is illustrated with an optional decorative or functional opening or cutout 16d. The lower edges 16a of male side plates 16 fit the remaining slots 13 in base 12, and their side edges 16b fit behind the free legs 15b of corner pieces 15. In the illustrated example, best shown in FIG. 5, side edges 16b are spaced from corners 15c, shown as gap 17, to provide some assembly tolerance and to accommodate warping and ash build-up, and to ensure easy nesting of the free sides 14c and 14e of each female side 14 between the corner pieces 15 of the other female side 14 when packed flat as shown in FIG. 1.
 FIG. 5 shows a preferred joined relationship of female sides 14 and male sides 16 once they are assembled into the slots 13 in base 12, and their edges/corners are engaged with one another in a unified structure. Optional additional corner pieces 115 can be added to the interior side edges of male sides 16 as illustrated in phantom lines. Optional additional corner pieces 115 would form a structural slot and reinforcement for the corner-supporting side edges 14b of the female sides 14 when the male sides 16 are joined with the female sides, and would make the entire fire pit more solid when fully assembled.
 FIG. 6 shows top plate 20 with a square outer frame 20a having inner edges 20b in a square shape defining a square opening 20e matching the arrangement of the upper edges of the assembled sidewalls 14 and 16. A vertical inner locking frame 20d extends downwardly from the interior surface of frame 20a, spaced outwardly from inner edges 20b of opening 20e and defining a continuous peripheral flange around the opening on the underside of the top plate matching the square shape of the assembled sides 14 and 16, and overlying and hiding the upper edges of the sides 14 and 16 when assembled.
 Discontinuous interior locking flanges 20c (similar to locking flanges 12c in base 12) are spaced outwardly of inner frame edges 20b and inwardly of vertical framing flanges 20d to define partial-length joining slots 21 between them, preferably centered with respect to each side. Fire/smoke opening 20e is defined by inner edges 20b, for example matching the square shape of the assembled sidewalls, although the shape of opening 20e can vary, like the shape of the outer frame portion 20a of top plate 20. Top 20 is placed over the upper edges 14e and 16e of previously assembled sides 14 and 16, with upper edges 14e and 16e inserted in slots 21, to securely lock the assembled sides together.
 FIG. 7 shows the assembled fire pit 10, and how all edges of sides 14 and 16 are hidden behind the flanges 12b and 20d and corner pieces 15. The appearance of fire pit 10 is accordingly uniform and neat, and gives the impression of a non-collapsible fire pit. The resulting structure is also sturdy, with very little play between the assembled pieces despite the lack of fasteners, and allows the use of thick steel or other plate material for the base, sides, and top for durability and longevity. FIG. 7 also shows an optional recessed "shelf" formed by inner edges 20b when inner edges 20b are created by angle iron used for vertical frame 20d. The horizontal legs of the angle iron that form inner edges 20b extend beyond the inner edge 20b' defined by the opening cutout in top plate 20, in a plane below that of the upper surface of top plate 20, such that a decorative or functional cover such as a glass or metal plate (see FIG. 8) can be fitted securely onto the shelf formed by angle iron legs 20b to close opening 20e.
 Disassembly of the fire pit is simply done in reverse of the operations shown in FIGS. 1-6. Top 20 is removed first, followed by male sides 16, followed by female sides 14, until the fire pit is stacked flat again for storage or shipping, as in FIG. 1.
 FIG. 8 shows the collapsible fire pit modified with a cover 38, a side panel door 40 in "front" side 16 in place of the decorative cutout, and an additional dedicated hose port P in side 14 to make the fire pit more useful for storing a propane tank, for example a 20-lb propane tank of the type commonly used for barbecue grills, although the size may vary. The basic flat panel structure 12, 14, 16, and 20 is essentially unchanged, and still stacks flat as shown in FIG. 1 and assembles and disassembles without tools or fasteners as shown in FIGS. 2 through 6. It will be understood that although both a top cover 38 and side door 40 are shown, one of these two access features would be sufficient for inserting or removing the illustrated propane tank. It will also be understood that the modifications of FIG. 8 could be originally manufactured into the fire pit structure to make it a dedicated propane tank holder, or they could be added-on to a fire pit used for burning in some seasons and then used for propane tank storage in other seasons. It will be further understood that the illustrated propane tank holder of FIG. 8 could also be used as a fire pit, without modification, when not used for tank storage.
 A further advantage of using the same structure for both fire pit and propane tank storage uses is that two such devices could be used side by side on a patio, etc., one as a fire pit and the other as a propane tank holder, while providing an aesthetically matching look.
 In the preceding description, various aspects and examples and configurations of making and using the invention as defined by the claimed subject matter (the "invention") have been described, for purposes of explanation, to provide a thorough understanding of the invention, and to enable those skilled in the art to make and use the invention. It will be understood that the disclosed embodiments are representative of presently preferred forms of the invention, but are intended to be explanatory rather than limiting of the scope of the invention as defined by the claims below. Variations and modifications of the invention as disclosed in the foregoing written specification and drawings are possible without departing from the scope of the invention as defined in the claims below. It should further be understood that the use of the term "invention" in this written specification is not to be construed as a limiting term as to number of inventions or discoveries or the scope of any invention or discovery, but as a descriptive term which has been used conveniently to describe advances in science and the useful arts. The scope of the invention is accordingly defined by the following claims.
Patent applications in all subclasses Front barrier or guard