Abstract:
A steamer for steam cooking food. The steamer has a base unit and a soft top and is particularly suited for steaming large quantities of food. The soft top is made of gas-impermeable fabric and seals around the base unit to provide a tightly sealed cooking enclosure for steaming food, such as lobster, corn, and steamer clams. The soft top has a zipper opening to provide access to the internal cooking enclosure. The soft top is provided in various sizes and shapes. The base unit includes a shallow reservoir for liquid and may include brackets for semi-permanently attaching a multiple-jet gas burner.

Description:
BACKGROUND INFORMATION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to the field of steam-cooking food. More particularly, the invention relates to a steam cooker.  
           [0003]    2. Description of the Prior Art  
           [0004]    Many types of portable cooking apparatus have been developed for preparing food. Such portable cooking apparatus include grills for cooking food directly over an open flame and cookers for heating, frying, steaming, or boiling food. Nevertheless, preparing large amounts of food that requires steaming, such as for a traditional lobster and clam dinner for a large group of people, the equipment and apparatus available has certain disadvantages that result in inconvenience, greater cost, and/or safety hazards. One of the largest conventional kettles available today is the turkey fryer, which comes with a support stand to support the cooker over a propane burner. The fryer can handle approximately 10-15 lobsters. So, for example, food preparation for a traditional lobster dinner for a group of 40 persons requires three kettles or turkey fryers, three gas burners, and three propane gas tanks, each with the necessary hose, connectors, and regulator, and this just for the lobster alone.  
           [0005]    The disadvantages of such cumbersome cooking equipment are numerous. The preparation of food for a steamed lobster and clam dinner for 40 or more people requires so much heavy, and cumbersome equipment that a large vehicle, such as a pick-up truck or a van, is needed to transport it to the dinner site. The safety hazards multiply because of the need for multiple gas burners. In addition, because of the inherent safety risks involved with using gas and an open fire to prepare food, preparation of such a picnic or dinner generally requires more than one person to prepare, manage, and monitor the multiple cooker and fuel set-ups.  
           [0006]    At a traditional lobster bake, all guests should be served all of the food, or at least the same food, at approximately the same time. With the conventional cookers, either a series of cookers are used or the guests are served in stages. Theoretically, it is possible to develop a kettle that would be large enough for steaming the lobsters, clams, and corn for a group of forty people. The cost of such a kettle would be prohibitive, the weight unmanageable, and the kettle far too bulky to be handled by a single person.  
           [0007]    What is needed, therefore, is apparatus that is capable of steam-cooking large amounts of food at one time. What is further needed is such apparatus that is easy to carry and transport, and that requires only one heat and fuel source. What is yet further needed is such apparatus that is adaptable to accommodate various amounts of food.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    For the reasons presented above, it is an object of the present invention to provide a steamer that is lightweight, easy to transport, and provides the necessary capacity to steam-cook a large quantity of food. It is a further object to provide such a steamer that includes a semi-permanently attached gas burner and that requires only one fuel source. It is a yet further object to provide such a steamer that is easily adaptable so as to accommodate and cook varying amounts of food in an efficient manner.  
           [0009]    The objects are achieved by providing a steamer according to the present invention that includes a base unit and a soft top that attaches to the perimeter of the base unit and provides a tight enclosure for steam cooking food. The base unit has collapsible or otherwise adjustable legs, a shallow pan that serves as a liquid reservoir, a steam plate that fits across the shallow pan above the reservoir, and a lip around the perimeter of the base. The steam plate has an open, grid-like surface or perforations of some type that allow steam to rise from the reservoir and circulate within the steamer, and the shallow pan has curved, sloping sides, similar in shape to that of a wok, that encourage steam to roll up along the sides of the soft top to promote even distribution of heat and steam. The soft top is made of a flexible, food-grade fabric that is substantially gas impermeable. The bottom edge of the soft top fits tightly around the lip of the base unit so as to provide a sealed enclosure in which to steam-cook food.  
           [0010]    The underside of the base unit is fitted with brackets that receive a conventional multiple-jet gas burner that is sized properly to produce the necessary heat to raise the water in the steamer to the desired temperature. The gas burner is semi-permanently attached to the brackets with threaded fasteners or some other suitable fastening means in such a manner that it does not have to be removed from the base unit when the steamer is collapsed for transport or storage between uses. This feature provides several advantages. Primarily, it reduces the chances of improperly securing the gas burner to the unit, since, ideally, it is attached to the base unit only once when the unit is assembled for the first time. It also reduces set-up time and storage needs if the burner remains securely attached to the base unit.  
           [0011]    The base unit of the steamer according to the invention may be height-adjustable. The legs of the base unit are collapsible or foldable to allow the base unit to collapse to a relatively flat unit that can be placed in a storage case that is only a few inches high. This greatly simplifies storage and transportation of the unit. There are numerous ways of providing height-adjustable or collapsible support legs and it is intended that the scope of the invention include all suitable means for providing such support legs. One example of such support legs includes telescoping tubes, whereby an outer tube slidingly receives an inner tube of a slightly smaller diameter. The selected height is maintained by inserting a locking pin through aligned through-holes through the inner and outer tubes, or simply by an interference fit between the two tubes. Another example includes legs comprising a lower leg that is pivotably connected to an upper leg. The lower leg folds down or out into a support position and the pivot joint is locked into the support position by means of a pawl or snap-button, or other suitable means of locking the joint so that the lower leg is not inadvertently moved out of the support position.  
           [0012]    The soft top of the steamer, when assembled over the base unit for use, may drape directly over the food without any additional support. As steam builds up within the cooking enclosure, the soft top is pushed up and out, providing a larger space in which steam can collect, as a means of maintaining relatively even cooking conditions throughout the cooking enclosure.  
           [0013]    It is also within the scope of the present invention to provide a soft-top support frame that will support the soft top in a particular shape. Many types of support frame are suitable and possible, and it is intended that the scope of this invention include any type of support frame that fits the particular configuration of the soft top and is suitable for the purposes of cooking food within the steamer. For example, one configuration of the soft top has an essentially cylindrical shape with a sidewall and a top wall. A cylindrical support frame for this soft top configuration includes a lower ring that is supported on the perimeter of the base unit and vertical support members that extend from the lower ring to a removable upper ring. The vertical support members are dimensioned such that they hold the top wall of the soft top a specific distance above the perimeter of the base unit; the upper ring is dimensioned to fit within the contour of the soft top at the interface between the sidewall and the top wall.  
           [0014]    The soft top according to the invention may be constructed such that it is pulled down over the support frame and cinched or otherwise tightly sealed around the perimeter of the base to provide a snug, sealed fit that impedes the escape of air or steam from the steamer at the interface between the soft top and the base unit. It is also within the scope of the invention to provide a soft top with a bottom edge that is vulcanized to the rim of the base unit. With this type of soft top, the support frame is assembled while the soft top is collapsed down around the base unit. Once the support frame is in place, the soft top is pulled up and fitted around the frame. With this particular configuration, loading/unloading product into the steamer is done from the top, without detaching the soft top from the base unit.  
           [0015]    Another cylindrical support frame includes a center support pole having a pole base that is seated on the floor of the base unit. The upper end of the center support pole is topped with a center collar for receiving and holding ends of support members that are cantilevered out toward the perimeter of the top wall and secured by a retainer ring. The soft top may also have a configuration similar to that of a dome tent. A domed support frame includes semi-circular, flexible support members that fit into support-member receiver slots or holes spaced around the perimeter of the base unit.  
           [0016]    Numerous configurations of the soft top are suitable for providing a structure for holding food within the base unit and include, in addition to the cylindrical and some shapes mentioned above, rectangular, and oval shapes. It is intended that all such suitable configurations be included within the scope of this invention.  
           [0017]    The soft top is a key feature of the steamer according to the invention. One function of the soft top is to provide a structure for holding food stacked above a heat source. Another function is to provide a sealed enclosure in which the conditions of temperature and pressure allow food to be cooked. Suitable for this purpose are materials that are heat-resistant and relatively gas-impermeable and allow a build-up of steam slightly above atmospheric pressure and a temperature slightly above the boiling point of water. The soft top can be made of a single piece of fabric or multiple pieces that are sewn together or otherwise held together to form a sealed cooking enclosure when properly assembled over the base unit. In order to allow a person to open up the top of the soft top to check on the progress of the cooking or to load/unload the steamer, the soft top may have a sealable opening in it. For example, with the cylindrical soft top configuration, the side wall and top wall are connected by a zipper so that the top wall is partially separable from the side wall to provide access to the cooking enclosure or to release steam as a means of controlling the speed of the cooking, or it is completely removable to provide greater access to the cooking enclosure for ease of loading/unloading product. With the dome-tent configuration, multiple wall sections extend from the bottom edge of the soft top to the top center, having curved seams connecting adjacent wall sections. One or more zippers are used at the curved seams to provide a sealable connection between the respective two or more wall sections.  
           [0018]    Other suitable means of creating a sealable opening in the soft top are also included within the scope of the present invention. One other means is that of using a hook-and-loop type fastener, such as VELCRO, to sealably connect the edges of two wall sections or the side wall and top together. The hook-and-loop material is attached to each edge of fabric that is to be connected in such a way that the edges of the soft-top fabric are first folded to impede the release of air or steam, with the folds then fastened in place with the hook-and-loop material.  
           [0019]    As mentioned above, the soft top for the steamer according to the present invention allows a slight overpressure to build up inside the soft top when it is properly assembled around the base unit and heat is applied to the base unit. The soft top is constructed such, that when the pressure exceeds a certain point, air or steam escapes around the bottom edge of the soft top and/or through the zipper or hook-and-loop closure. A fold or flap of soft-op fabric or other gas-impermeable material is attached to the under side of the soft top to cover the zipper seam area to further impede the flow of steam through the closure and thereby to increase the pressure that builds in the cooking enclosure.  
           [0020]    Food caterers or others who provide food to groups of people that vary widely in number may desire a steamer that is adaptable to the particular required capacity. For such cases, the steamer according to the present invention includes a multi-stage soft-top that extends upward to expand capacity. This multi-stage soft top has a base side wall with a lower edge that fits snugly around the perimeter of the base unit and multiple side wall sections that attach to the soft top between the base side wall and the top. As with the soft top described above, the multi-stage soft top may drape directly over the food assembled in the cooking enclosure, without an upper support frame, or may have a support frame comprising one or more support sections. For example, the upper support frame may include a base frame section and multiple extender frames that mount on top of the base frame section to create a steamer “tower.” Numerous methods of stacking and securing frame sections one atop the other are known and it is intended that the scope of this invention include any suitable means of stacking frame sections. Such methods includes seating an upper frame section on the upper edge of the base frame section and securing the sections to each other with fastener means, such as pawls that snap around the edges of the frame sections. Also included are methods of stacking sections that decrease in circumference from bottom to top, in order to minimize the tendency of the steamer tower to topple.  
           [0021]    Since the steamer according to the invention may be used as a portable steamer, it is important that it be easily transportable and stowable in a single container. The steamer has multiple component pieces and is easily disassembled for storage. In one embodiment of the invention, the steamer is provided with a carrying case for receiving and carrying the component pieces. The steamer is partially disassembled for transportation in the carrying case by folding, collapsing, or removing sections of the legs of the base unit and collapsing or folding the soft top to form a substantially flat configuration that fits into the carrying case. In another embodiment, the steamer itself includes a transport structure that is attached to the base unit and is deployable as needed. For example, a transport structure similar to that of conventional rollable suitcases with an extendable handle is mountable on the base unit of the steamer. In this case, casters are attached to two or four of the legs and a telescoping frame that serves as a handle is attached to the base unit or the legs.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    [0022]FIG. 1 shows the steamer according to the invention, assembled, with the soft top cinched around the base, the base supports fully extended, and the gas burner with burner shield in place.  
         [0023]    [0023]FIG. 2 is a perspective view of the base of the steamer of FIG. 1, showing shallow pan, stanchion supports, collapsible base supports, and drain pipe.  
         [0024]    [0024]FIG. 3 is a partial elevational view of the steamer of FIG. 1, illustrating the shape of the shallow pan and an embodiment of the upper frame that supports the soft top.  
         [0025]    [0025]FIG. 4 is a cross-sectional elevational view of the Preferred Embodiment of the steamer according to the invention, showing a center-pole support frame for the soft top.  
         [0026]    [0026]FIG. 5 is an elevational view of the base unit of the steamer, showing the location of the jet burner under the shallow pan.  
         [0027]    [0027]FIG. 6 shows the steamer of FIG. 4, disassembled for storage or transportation.  
         [0028]    [0028]FIG. 7 shows a travel carrier in which to transport the steamer of the present invention.  
         [0029]    [0029]FIG. 8A shows the steamer according to the invention with an accordion-pleated, expandable soft top.  
         [0030]    [0030]FIG. 8B shows the steamer according to the invention with an expanded, full-framed soft top.  
         [0031]    [0031]FIG. 9 shows the steamer according to the invention with a dome-shaped soft-top.  
         [0032]    [0032]FIG. 10 shows a detail of a flap of material covering the soft top enclosure.  
         [0033]    [0033]FIG. 11A shows a rectangular-shaped steamer according to the present invention.  
         [0034]    [0034]FIG. 11B shows an oval-shaped steamer according to the present invention.  
         [0035]    [0035]FIG. 12 is an illustration of a steamer combined with a transport structure according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]    [0036]FIG. 1 shows a steamer  10  according to the invention. The steamer  10  comprises a base unit  20  and a soft top  40 . The base unit  20  is shown in greater detail in FIGS. 2 and 3, and includes a shallow pan or reservoir  22  and base supports  24 . A drain and drain pipe  28  with a drain cock are provided in the reservoir  22 . A heat shield  30 , shown in FIG. 1, is not shown in FIGS. 2 and 3 in order to more clearly illustrate the base unit  20 .  
         [0037]    The base supports  24  of the base unit  20  are shown as height-adjustable legs formed from metal tubing. In the embodiment shown, a lower tube  24 B is slidingly received in an upper tube  24 A and secured in position with a locking pin  24 C. It is understood that numerous types of supports are suitable for the steamer  10  according to the invention, such as, for example, telescoping tubes with a height-adjustable locking mechanism, tubes with an interference fit, similar to the typical “vacuum-cleaner” or tent-pole extension tubes, pivotably secured supports that fold out of the way for storage, etc.  
         [0038]    A first embodiment of the soft top  40  is shown in FIGS. 1 and 3. The soft top  40  is supported on an upper frame  42  that comprises a plurality of stanchions  44  that are seated in receptacles  45  on a support ring  46  that is mounted on the rim of the shallow pan  22 . In order to maintain the proper orientation of the stanchions  44 , an upper ring  39  may be fitted atop the upper ends of the stanchions  44 , or loops or other types of retainers constructed to receive the upper ends of the stanchions  44  may be provided in the soft top  40 . The soft top  40  comprises a side wall  50  and an openable top  52 . In the embodiment shown, the side wall  50  is cylindrical in shape. Other suitable shapes are included within the scope of the invention and are shown in FIGS. 9, 11A, and  11 B. In the embodiment shown in FIGS. 1 and 3, the openable top  52  is flat and is removably attached to the side wall  50  by means of an openable closure  53 , which, in the embodiment shown in FIG. 1, is a zipper. A bottom edge  54  of the side wall fits around the outer perimeter of the shallow pan  22  and is sealable around a lip  23  formed on the shallow pan  22  by means of an adjustable sealing means  56 . In the embodiment shown, the adjustable sealing means is a drawstring and a spring-loaded drawstring fastener. Other suitable means of sealing the bottom edge  54  of the soft top  40  around the shallow pan  22  are included within the scope of the invention. Such means include, but are not limited to, an elasticized bottom edge, a snap fastener, a draw-bolt, a hook-and-loop type closure, a vulcanized seal between the bottom edge  54  and the perimeter of the shallow pan  22 , or any combination thereof that allows the soft top  40  to provide a sufficient seal with the shallow pan  22  that will allow a slight overpressure to build up within the enclosure.  
         [0039]    Preferably, the material used for the soft top  40  is a food-grade, flexible, heat-resistant and gas-impermeable material. Examples of suitable materials include composite materials comprising a substrate of woven fiberglass mat or fabrics made of aramid fibers, such as KEVLAR®, covered with a food-grade flexible material such as a rubber silicone material, silicone rubber, canvas, aluminum foil, and other suitable materials. When cooking some types of food, for example, when steaming lobsters and clams, it is desirable to have steam accumulate within the cooking enclosure sufficiently to create a slight overpressure. This ensures an even distribution of heat and steam, resulting in uniform cooking conditions throughout the enclosure, despite the large amount of food that is being prepared within the enclosure at one time. For this reason, a gas-impermeable material is preferable. The steam will eventually escape the cooking enclosure, not through the material but at the upper and lower extremes of the cooking enclosure, for example, at the interface between the bottom edge  54  of the soft top  40  where it is cinched around the base unit  20 , and also through the seams connecting the side wall  50  and the openable top  52 , and, if a zipper is used as the means of enclosure  53 , through the interfaces at the zipper teeth. In order to impede the escape of steam, a flap  51  is provided in the soft top  40  that covers the enclosure  53 , as shown in FIG. 10.  
         [0040]    A second embodiment of the soft top  40  is shown in FIG. 4. The soft top  40  is essentially cylindrical in shape, with the side wall  50  and the openable top  52  as described above. A center-pole support frame  49  of this embodiment, however, resembles more an “umbrella” support frame that includes a single center-pole  43 , having a lower pole base  43 B and an upper pole end with a spoke receptacle collar  43 A, a plurality of spokes  48 , and a retainer ring  43 C. The lower pole base  43 B sits on the bottom of the shallow pan  22 . As shown, the base  43 B sits over the drain in the pan and is perforated to allow water to drain from the shallow pan  22 , without first removing the center pole  43 . The plurality of spokes  48  are attached to the collar  43 A at the top of the center-pole  43  and extend outward toward an outer perimeter of the openable top  52 . For reasons of stability, the outer ends of the plurality of spokes  48  are retained in the retainer ring  43 C. As with the embodiment described above, the soft top  40  is draped over the center-pole support frame  49  and cinched tight around the perimeter of the shallow pan  22 , thereby providing a support that maintains the essentially cylindrical shape of the soft top  40 .  
         [0041]    The shallow pan  22  is shown in profile in FIGS.  4 - 5 . With the traditional lobster dinner, the food (lobster, steamers, corn-on-the-cob) is steamed, not boiled. A steam plate  47  or perforated flat plate is fitted across the open top plane of the shallow pan  22  to allow steam to rise from the shallow pan  22  into the cooking enclosure formed by the soft top  40 , and to prevent food from coming into contact with water. In the embodiments shown, the shallow pan  22  has the shape similar to that of a wok, rather than a cylindrical shape. This shape encourages the steam to roll up along the sides of the cooking enclosure formed when the soft top is closed, thereby promoting even distribution of steam throughout the enclosure. A suitable material for the steam plate  47  is 14 gauge stainless steel and for the shallow pan  22  is 11 or 12 gauge stainless steel, finished on both sides.  
         [0042]    [0042]FIG. 5 shows the base unit  20  of the steamer  10 , with a conventional, multi-jet gas burner  60  fitted into burner brackets  62  that are mounted on the bottom of the shallow pan  22 . The burner used in the first embodiment is a 23-jet conventional burner that produces 100,000 Btu. Ideally, the gas burner  60  is semi-permanently attached to the base unit  20  when the steamer  10  is initially set up. Threaded fasteners or other types of suitable fasteners that allow the burner  60  to be removed as required are preferably used to attach the gas burner  60  to the base unit  20 , which then remains affixed to the base unit  20 , even when the steamer  10  is partially disassembled for transportation and storage. This provides the advantage that the burner  60  can be properly and securely installed during the initial set-up and then remain so installed for repeated, subsequent uses. In addition to reducing set-up time, having such a partially pre-assembled base unit and burner also ensures optimal conditions for cooking, with respect to the distance of gas jets from the steamer and proper position of burner unit under the center of the base unit.  
         [0043]    The steamer  10  according to the invention is also usable without the semi-permanently attached gas burner  60 . For example, the steamer can be placed over an open fire pit or coals, or any other suitable heat source, depending on the intended use.  
         [0044]    [0044]FIG. 6 is an illustration of the steamer  10  disassembled for transportation. The lower tubes  24 B of the height-adjustable legs or base supports  24  have been removed, the soft top  40  unzipped, the upper support frame  42  removed and taken apart, and the soft top  40  collapsed down into the shallow pan  22 . The gas burner  60  is still attached. The entire disassembled steamer  10  is only a few inches high and is easily stored in a carrying case  70 , such as the one shown in FIG. 7  
         [0045]    [0045]FIGS. 8A, 8B, and  9  illustrate various configurations of the soft top. An expandable soft top  41  is shown in FIG. 8. As shown, an expansion section  57  is added to the soft top  40  between an upper edge of the side wall  50  and the outer edge of the top wall  52 . In the configuration shown, the upper support frame  42  does not extend up into the area of the expansion section  57 , but rather, the expansion section  57  is allowed to rest in a folded or collapsed state on top of the food within the cooking enclosure. As steam builds within the enclosure, the expansion section  57  may rise to accommodate the increased volume of steam until a certain pressure is reached. It is, of course, possible to seat an expansion frame section on top of the upper support frame  42  so that the expansion section  57  is held as a substantially rigid expansion section, as shown in FIG. 8B. FIG. 9 illustrates a dome-shaped soft top  59  which is constructed of a plurality of panels sewn together and fitted over a frame formed by a plurality of flexible support struts  36  fitted into strut retainers  35  that are provided around the outer perimeter of the base unit  20 . The openable closure  53  is a zipper. The dome-shaped soft top  59  can also be used without the frame, whereby the bottom edge  54  is fitted over the base unit and the upper portion of the top allowed to drape across the top of the base unit  20  (and across any food that is placed within the enclosure formed by the soft top  59 . FIGS. 11A and 11B illustrate a rectangular soft top  40 A and an oval soft top  40 B, respectively.  
         [0046]    [0046]FIG. 12 illustrates a portable steamer with a transport structure  200  according to the invention. Two or four of the base supports  24  are fitted with lockable casters  201 . A handlebar  203  is removably attached to a portion of the base unit  20  with a conventional tube locking mechanism and allows one to pull the steamer along on the two or four casters  201 . The soft top  40  of the combination steamer with transport structure  200  as shown in FIG. 12 has been collapsed into a storage and transportation configuration and the handlebar  203  is attached for use. Ideally, a separate protective covering  74  is fitted over the soft top  40  and attached to the base unit  20  to protect the soft top  40  when the steamer  10  is not in use. It is, of course, possible, to cover the soft top  40  with a flexible cover that is simply secured with elastic shock cords or straps to the base unit  20 . Indeed, the types of protective coverings that are suitable for covering the soft top are numerous and it is intended that the scope of the invention encompass a portable steamer with transport structure that allows one to roll the steamer onto the site, and to cover the steamer in its collapsed state for transportation and storage.  
         [0047]    Although the steamer  10  according to the present invention has been described above with reference to preparing large quantities of food, it is well within the scope of the present invention to size the steamer  10  appropriately for preparing individual or family-sized portions of food. For such an application, the steamer  10  is placed directly over the burner on a conventional stove or heat source. Accordingly, the base unit  20  does not require the base supports  24 . Since the steamer  10  is sized for smaller quantities of food, it is easily manageable by a person and no longer requires a drain for draining liquid from the shallow pan as a person can pick up the shallow pan and pour the liquid into a sink, for example. In a further embodiment, an individual- or family-sized steamer  10  is constructed specifically for use with a microwave, and, as such, the base unit  20 , as well as the soft-top  40  is made of heat-resistant, microwavable material.  
         [0048]    The detailed description of the invention includes descriptions of specific embodiments. It is understood, however, that a person skilled in the art is capable of implementing many variations and modifications of the invention without straying from the intended scope of the present invention.