Aeronautics and astronautics – Landing gear – Water landing
Reexamination Certificate
1999-02-09
2001-03-13
Swiatek, Robert P. (Department: 3643)
Aeronautics and astronautics
Landing gear
Water landing
C114S292000
Reexamination Certificate
active
06199797
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of aircraft floats and, in particular, to an aircraft float having a one-piece molded shell for attachment to experimental, ultralight and light general aviation aircraft.
BACKGROUND OF THE INVENTION
Aircraft floats of various types have been attached to the undercarriages of aircraft to allow the aircraft to operate from bodies of water. The three principal types of float that are in common use are aluminum floats, fiberglass floats, and inflatable floats, with the type of float that may be used for a given aircraft depending, in part, upon the aircraft's size and classification. General aviation aircraft, which are all “type certified” by the Federal Aviation Administration (FAA), are commercially assembled aircraft such as corporate executive jets and Cessna light airplanes. Experimental aircraft must be home built and are typically sold as kits. Ultralight aircraft are usually tubing and fabric construction and, again are typically sold in kit form and home built.
Aluminum aircraft floats are typically manufactured from sheets of aircraft grade aluminum riveted and/or bonded onto a series of bulkheads and stringers to form a float having a predetermined shape. Though in widespread use, these floats have a number of drawbacks. First, the aircraft aluminum utilized in the manufacture, and the labor expended in assembling the floats, makes these floats fairly expensive. Second, the use of rivets along the seams on the underside of the float increases the chance that water will seep into the inside of the float. Such seepage can create a dangerous situation due to unpredictable shifts in the center of gravity of the aircraft. In some designs, a water-proof closed-cell foam is utilized to at least partially fill the inside volume of the float to prevent water seepage. However, these foams add weight to the floats and further increase their cost.
Fiberglass floats, such as those described in U.S. Pat. No. 3,208,421, are often utilized on experimental and ultralight aircraft. These floats are typically manufactured either by forming two mating fiberglass shell pieces in two female molds and subsequently bonding the shell pieces together, or by forming a water-proof foam into the desired shape and forming the fiberglass over the foam. Fiberglass floats also have a number of drawbacks. First, the cost of manufacturing fiberglass floats is relatively high as a result of the labor expended in forming the completed float. Second, fiberglass is not very impact resistant and can crack and leak if subjected to impact from rocks, logs, or other underwater obstructions. Third, the seam between the two pieces of the float creates a fault line that is subject to cracking and water leakage. Fourth, the use of foam within many of these floats increases the weight of such floats. Finally, the nature of the fiberglass process creates a hazard to manufacturing workers due to the friability of the fiberglass and the potentially toxic chemicals used to promote bonding.
Inflatable floats, such as those described in U.S. Pat. No. 4,697,762, typically include an outer shell manufactured of a tough fabric and an interior portion that is segregated into a plurality of inflatable interior chambers or bladders. In operation, the chambers are inflated with air until the chambers press against the outer shell to form a relatively hard surface upon which the aircraft may land. Inflatable floats, like the aluminum and fiberglass floats described above, have a number of significant drawbacks. First, water may penetrate the outer shell and occupy the spaces between the inflatable interior chambers causing the same unpredictable changes in weight and shifts in the center of gravity of the aircraft that may occur with aluminum and fiberglass floats. Second, the tough fabric on the outside of the float is prone to absorbing water and carrying water on its upper surface, thus increasing the weight of the aircraft during take-off. Finally, one or more chambers of an inflatable float may deflate unexpectedly, creating a potentially hazardous situation for the pilot.
Therefore, there is a need for an aircraft float that may be utilized with experimental, ultralight, and light general aviation aircraft, is less expensive than existing aluminum and fiberglass floats, is lighter than existing aluminum and fiberglass floats, and is more impact resistant than existing fiberglass floats.
SUMMARY OF THE INVENTION
The invention is a lightweight, high strength aircraft float for use by ultralight, experimental, and light general aviation float planes. The float consists of a unitary outer shell that is formed into a desired shape using rotational molding, or blow molding, from a suitable polymer. In the preferred embodiment, the float includes a shell formed of a thin outer layer of high strength, cross-linked high density polyethylene (HDPE), and a thicker foamed polyethylene inner layer that is created by the use of a foaming agent during the molding process. The preferred shell is manufactured of HDPE due to its high strength and impact resistance across a broad temperature range and its resistance to degradation by ultraviolet light. It is also preferred that an internal reinforcing structure be utilized to provide additional stiffness and rigidity to the upper and lower surfaces of the float. This structure may consist of two extruded aluminum box sections, formed to appropriate profiles, which are inserted through one or more small apertures at the front or rear of the roto-molded shell and secured within the shell by mechanical fasteners. Two or more mounting devices may be attached to the upper surface of the float to allow the float to be attached to the fuselage of the floatplane. The preferred mounting devices allow for adjustment of the longitudinal placement of the floats, and thus the center of gravity of the floats relative to the center of gravity of the aircraft, by a small amount, typically a few inches. Finally, the float may be filled, or partially filled, with a closed-cell foam of a suitable polymer, such as expanded polyethylene foam, though floats without such a foam are preferred.
Therefore, it is an aspect of the invention to provide a floatplane float with a rotationally or blow molded unitary polymer shell.
It is a further aspect of the invention to provide a floatplane float that may include an internal reinforcing structure that is installed by insertion through one or more small openings in a one-piece polymer shell.
It is a further aspect of the invention to provide a floatplane float that has no seams, joints, rivet or penetrations of any kind through the wetted lower surface of the float.
It is a further aspect of the invention to provide a floatplane float that includes a mounting device to allow quick adjustment of the center of gravity of the float relative to the center of gravity of the floatplane.
It is a further aspect of the invention to provide a floatplane float that may be filled with internal foam or may be utilized without internal foam.
It is a further aspect of the invention to provide a floatplane float that performs as well as existing floats but reduces cost, reduces the probability of water leakage in service, and reduces weight relative to existing floats.
It is a still further aspect of the invention to provide a floatplane float that does not need to be inflated with air and that, consequently, cannot deflate during operation.
These aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims and accompanying drawings.
REFERENCES:
patent: D. 390527 (1998-02-01), Niemier
patent: 3208421 (1965-09-01), Landes et al.
patent: 3467345 (1969-09-01), Windecker
patent: 4418634 (1983-12-01), Gerbus
patent: 4697762 (1987-10-01), Arney
patent: 4915052 (1990-04-01), Reeser
patent: 5039297 (1991-08-01), Masters
patent
Ritchie William B.
Swiatek Robert P.
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