Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – Of inorganic materials
Reexamination Certificate
2000-11-22
2002-05-07
Kuhns, Allan R. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
Of inorganic materials
C264S046700, C264S050000, C264S279000, C264SDIG006
Reexamination Certificate
active
06383421
ABSTRACT:
BACKGROUND
The ambiance and physical sensation associated with a natural flame such as those found in campfires and fireplaces are widely desired. But because of a number of economic and environmental issues, including the pollution and physical mess of wood burning, the use of wood-burning appliances and open campfires has been severely restricted in recent years. There have been a number of attempts to produce a realistic appearing system of synthetic logs, burning wood pellets, natural gas, propane, LPG, or butane that would duplicate the ambiance of wood burning without the liabilities. Several systems have reached the market place and have enjoyed some commercial success. However, none of these systems have achieved the appearance, ambiance, and functional realism of real wood fires.
Gas log devices currently are all constructed on a similar pattern. The gas is burned by allowing it to escape from a series of small holes in a metallic tube or more complex burner device. The burner is then positioned under an artificial log in an attempt to simulate a natural log. The resulting gas flame is then allowed to play across a series of artificial log shapes to produce the visual illusion that the logs are actually burning. Prior to the instant invention, in all cases, the degree of realism relies on successfully hiding the obviously artificial nature of the burner itself. This is usually accomplished by placing the burner and its flames below and/or behind one or more of the artificial logs. To enhance realism, the design of the shapes of the artificial logs and the placement of the burner restricts the viewing area of the flames to those areas that look most realistic and to prevent viewing of the burner. Thus, area over which the flame may be viewed is small. A more realistic design is impossible with this technology because much of the flame must be hidden from view to prevent view of the artificial burner from some angles, or view of jets of flame suggesting that gas rather than wood was being burned.
Using current technology, a designer of an artificial log device must somewhat restrict the view of the flames to those portions that appear more natural, such as the upper part of the flame. Similarly, view of the burner must be obstructed by placement of a log or other obstruction in the predicted line of view. Unfortunately, a trade-off results in that to completely obstruct the view of the burner, the view of the logs and flames must be excessively blocked. As a result, in most applications, the burner is sometimes visible and portions of the flame, which are somewhat attractive, are sometimes blocked from view.
The need to block the view of the burner severely restricts the emission of radiant energy, primarily infrared (IR), that can be emitted by the flame. For those designers hoping to capture a portion of the available heat from the device, it is then necessary to place a heat exchanger in the hot zone above the flames, and to provide a blower system to force the resulting heated air into the surroundings.
Using such heat transfer devices allows a person near the prior art artificial logs to feel warmth from a stream of moving hot air. The resulting sensation is unlike a real wood fire, in part because the IR does not warm the person. In fact, the radiant or IR portion of the available energy is simply lost, having been blocked by the artificial logs that prevent view of the burner. These disadvantages seriously degrade the sensory illusion of the fire and combine with visual discrepancies related to the use of burners and the need to block view of the lower portions of the flames.
The artificial logs of the current art are generally formed by one of two candidate technologies. In the older of these, a ceramic or cementitious material is cast into a mold. Sometimes the mold is derived from a natural log. As an alternative, particularly when the “log” shape needs to conform to a specialized geometric requirement of the fireplace or gas stove, the mold is created by copying a machined or carved piece of some easily worked material such as plaster, plastic foam or soft wood. This piece is generally a “positive” of the desired final log shape. From the man-made “positive,” a “negative” is generally constructed of some material, which then provides the cavity into which the “log material” will be cast or otherwise placed. The “negative” provides copies (castings) that are as nearly identical as possible to the original positive. These pieces generally are lacking the realism of a natural piece of wood because of the extensive effort needed to actually duplicate the almost infinite complexity of a piece of natural wood, either split or bark covered. Another disadvantage is that the ceramic or cementitious material that is cast into such a mold is generally quite dense, hard, and of necessity must be quite refractory to allow it to withstand the play of flames over it at temperatures often exceeding 1300 F. Given these design and performance constraints, it is not surprising that these high-density logs are not “active” in the sense of contributing more than their physical shape to the creation of the fire illusion. And in fact, they actually act as a large heat sink, absorbing both the visible light and the IR emitted by the flames, significantly reducing the warmth, which would otherwise be radiated. A person sitting by the fire feels very little warmth and sees very little light. In a dimly lit room, the logs are generally only visible as a dark profile, while the flames play around them in a predetermined and usually near-static pattern. This is not a very convincing illusion of a real wood fire, and is not a very efficient or pleasant way to provide heat to the room. For applications involving portable campfires, these logs would be wholly unsuitable because they are very heavy. A set of such logs would generally involve the use of 1-2 gallons of the liquid castable material to provide the necessary log shapes, and therefore would typically weigh approximately 30-40 lbs, not including all the accompanying fittings and other structure. This excessive weight would make design of any portable device difficult or impossible.
A more modern alternative method of creating the artificial logs employs the technology of vacuum-formed ceramic fibers to produce lightweight log shapes. These ceramic fiber logs are “semi-active,” emitting a glow in response to the play of the flame and reducing the heat sink effect. They are also significantly lighter, presenting the possibility that they could be used in a portable device. However, they suffer from their own set of limitations. These limitations arise primarily from the limitations of the vacuum-forming technique itself. All such logs will of necessity have at least one side that must remain hidden from the viewer because it has no log-like detail and is essentially a flat surface. This results because at least one side of the vacuum-mold must remain open to the slurry from which the log is made. That surface will be random and slightly lumpy because that is the way that the slurry of fibers naturally flows under the influence of the vacuum. Furthermore, in order to allow the wet fiber shape to be removed from the vacuum mold, the logs generally are restricted to those having more planar surfaces rather than the detailed, curved surfaces of natural bark-covered wood. It is far easier to give the illusion of a planar, split piece of wood than it is to create a vacuum mold that has the fully round natural shape. With considerable creativity and clever placement, the vacuum-formed logs can be made to appear more natural when burning than the heavy ceramic logs, but the illusion is still incomplete, especially so since the vacuum-formed logs have the extra restriction of being unable to achieve a full round shape. And, because the ceramic fiber logs only provide an illusion of being on fire, they still require the use of a hidden metallic tube or similar burner. The viewing area must, in many cases, be even more restricted than with the
Kuhns Allan R.
Thompson David S.
LandOfFree
Method of manufacturing a gas burning artificial log from... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing a gas burning artificial log from..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing a gas burning artificial log from... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2883620