US3881439A

US3881439A - Buoyancy body

Info

Publication number: US3881439A
Application number: US369145A
Authority: US
Inventors: Erik V Svanholm
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-06-15
Filing date: 1973-06-12
Publication date: 1975-05-06
Anticipated expiration: 1992-05-06
Also published as: GB1429246A; SE395131B; FR2189256A1; FR2189256B3; DE2329996A1

Abstract

A buoyancy body intended to be used in motorboats and sailing boats consists of a hermetically sealed flexible envelope containing a multiplicity of relatively small pieces of expanded plastic. The pressure within the envelope is slightly reduced so that the atmospheric pressure compacts the contents of the envelope.

Description

United States Patent [191 Svanholm May 6,1975

[ BUOYANCY BODY [22] Filed: June 12, 1973 [21] Appl. No.: 369,145

[30] Foreign Application Priority Data June 15, 1972 Sweden 7862/72 [52] US. Cl 114/69; 9/8 R; 114/50 [51] Int. Cl B63b 43/00 [58] Field of Search 9/8 R, 8 P, 314, 344; 114/.5 F, 50, 69; 244/5 [56] References Cited UNITED STATES PATENTS 1,089,617 3/1914 Adams ll4/.5 F 3,050,750 8/1962 Harrison 9/8 R 3,378,864 4/1968 Comes 9/314 3,450,374 6/1969 Moore 244/5 3,727,252 4/1973 Bauermeister 9/344 FOREIGN PATENTS OR APPLICATIONS 734,640 8/1955 United Kingdom 114/.5 F

Primary ExaminerRobert J. Spar Assistant ExaminerDonald W. Underwood Attorney, Agent, or Firm-l-Iill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57] ABSTRACT A buoyancy body intended to be used in motorboats and sailing boats consists of a hermetically sealed flexible envelope containing a multiplicity of relatively small pieces of expanded plastic. The pressure within the envelope is slightly reduced so that the atmospheric pressure compacts the contents of the envelope.

2 Claims, 2 Drawing Figures BUOYANCY BODY BACKGROUND OF THE INVENTION This invention relates to a buoyancy body and more particularly to a buoyancy body that is intended to be used for increasing the buoyancy of boats, such as motorboats and sailing boats, so as to help keeping them afloat in case they should be filled with water.

It is known to increase the buoyancy of boats by filling empty spaces in the hull with expanded plastic or by providing hermetically sealed air pockets. Both of these methods are fairly expensive and, besides, cannot easily be used in the case of existing boats but are best suited for use in conjunction with the production of the boats.

In accordance with the invention there is provided a buoyancy body comprising a multiplicity of pieces of a buoyancy material having a density substantially less than that of water and a hermetically sealed flexible envelope enclosing the pieces of buoyancy material.

The buoyancy body according to the invention may be produced in a single size or possibly a few sizes, e.g. one size having a buoyancy of one kilogram and one size having a buoyancy of 5 kilograms in water, meaning a volume of slightly more than 1 liter and 5 liters, respectively. Depending on the required or desired increase of the buoyancy of the boat, a smaller or larger number of buoyancy bodies are used. Since the buoyancy bodies are relatively small, they can advantageously be placed where a small space is available that cannot otherwise be utilized. Thus, since almost every boat has several smaller or larger spaces which are not normally used for any practical purpose but which can be filled with the buoyancy bodies, the latter need not detract appreciably from the useful space.

The invention will be better understood from the following description of an exemplary embodiment shown in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view of a buoyancy body according to the invention, a portion of the envelope being broken away;

FIG. 2 is a view in cross-section taken along line II-Il of FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawing, there is shown a buoyancy body which comprises a multiplicity of balls 11 of expanded plastic, viz. expanded polystyrene, enclosed in a hermetically sealed flexible envelope 12 made from a length of plastic tubing. The sealing of the envelope has been effected by pinching and heat sealing the ends 13 of the length of tubing after the balls 11 have been inserted and a slightly reduced pressure has been produced within the envelope. Conventional packaging machines can be used for mass production of buoyancy bodies according to the invention.

Owing to the reduced pressure within the envelope, the atmospheric pressure acting on the exterior side of the body will slightly compact the buoyancy material constituted by the mass of polystyrene balls without deforming the individual balls, which are rigid, that is, they are capable of withstanding a pressure difference between the interior and the exterior of the envelope of 0.1 atmosphere or more (assuming that the envelope is infinitely flexible). Therefore, the body as a whole exhibits some degree of plasticity so that its shape can be adapted to the shape of the space where it is placed.

The numerical value of the slight vacuum or reduced pressure within the envelope 12 is not very critical and should be chosen in dependence of the size of the balls 1 l and the envelope 12 and the thickness and flexibility of the film from which the envelope is made so that the desired degree of compactness, plasticity and shape permanence is obtained. The best value is most easily found through experiments but generally the absolute pressure within the envelope should be below one atmosphere, but not lower than 0.8 atmospheres, at temperatures within the envelope below 25C. A preferred lower limit is 0.9 atmospheres.

The film from which the envelope of the buoyancy body is made of course has to be of such thickness and quality as to prevent the surrounding air from penetrating it and destroying the reduced internal pressure. In the exemplary embodiment shown, the envelope 12 is made from a triple laminate consisting of two outer layers of polyethylene and an intermediate layer of polyamide and having a thickness of about 0.1 millimeter. This laminate is capable of conferring on the buoyancy body the necessary mechanical strength and resistance to attack from oils or fuels. It should be noted, however, that films or laminates of other materials and of a thickness up to 0.5 millimeters can be used. A preferred thickness range is 0.05 to 0.2 millimeters.

Although polystyrene in ball form and having a density of about 30 kilograms per cubic meter is presently believed to be the best buoyancy material, other materials may be used as long as they have a density that is sufficiently low; the density should be not more than 100 kilograms and preferably less than 50 kilograms per cubic meter. Moreover, although a buoyancy material in ball form is advantageous in that it simplifies the filling of the envelope and also can facilitate the plastic shaping of the buoyancy body, the bouyancy material may be in the form of more or less irregular pieces, e.g. pieces obtained by disintegration of larger pieces of scrap material. The size of the balls or pieces is not very critical but the maximum linear cross-sectional dimension of the largest balls or pieces preferably is not more than 15 millimeters, and for best results percent (by number or more of the balls or pieces should have a maximum linear cross-sectional dimension much less than 15 millimeters, preferably between 2 and 5 millimeters.

The drawing illustrates the approximate preferred proportions between the length, width and thickness of the buoyancy body according to the invention, the volume of the illustrated buoyancy body being slightly more than one liter. The flat configuration permits the surfaces of a space to be covered with one or more fairly smooth and coherent layers of buoyancy bodies which layer or layers will not only increase the buoyancy of the boat but also form a heat and sound insulation.

What I claim is:

l. A buoyancy body comprising a multiplicity of individual pieces of a substantially rigid buoyancy material having density substantially less than that of water and a hermetically sealed substantially flat and rectangular flexible envelope enclosing the pieces of buoyancy material, the absolute pressure within the envelope being lower than one atmosphere at sea level, but higher than 0.8 atmosphere, at temperatures between 0 and 25C.

2. Buoyancy body as claimed in claim I in which the maximum linear cross-sectional dimension of the individual pieces is 15 millimeters or less.

Claims

1. A buoyancy body comprising a multiplicity of individual pieces of a substantially rigid buoyancy material having density substantially less than that of water and a hermetically sealed substantially flat and rectangular flexible envelope enclosing the pieces of buoyancy material, the absolute pressure within the envelope being lower than one atmosphere at sea level, but higher than 0.8 atmosphere, at temperatures between 0* and 25*C.

2. Buoyancy body as claimed in claim 1 in which the maximum linear cross-sectional dimension of the individual pieces is 15 millimeters or less.