Accumulator

The invention disclosed herein will be better understood with reference to the following drawing of which:

FIG. 1 is an elevation view, partially broken away, of the accumulator disclosed herein.

With reference to FIG. 1, the accumulator 10 includes a synthetic rubber core 12 having a circular cross-section and a diameter of 1 3/8 inch. A suitable rubber material is Duro-4S cord available from Delford Industries of Middletown, N.Y. Such material has a durometer of 45-55 and a tensile strength of 2500-2700 lbs. per sq. in. Such material can stretch approximately 700% before breaking. Although the preferred core material is a single, solid piece, multiple elastic strands can be used. The core 12 is surrounded loosely by an overbraid 14 made of nylon strands. Suitable strands are made from plied nylon yarns and have at least a 10,000 lb. breaking strength. Suitable nylon braid is available from New England Ropes, Inc., of New Bedford, Mass. As shown in FIG. 1, the nylon overbraid 14 is seized to the core 12 at intervals by means of tape 16. It is preferred that the tape 16 be a glass reinforced tape having high tensile strength. A suitable tape is available from Permacel of New Brunswick, N.J., under the designation P-162 Strap-it.RTM..

The preferred method of manufacturing the accumulator 10 will now be described. A length of the rubber core material 12 is selected according to the desired relaxed or working length of the finished accumulator. This length of rubber core material 12 is then stretched to approximately three times its relaxed length. A length of the overbraid material 14, corresponding in length to this stretched length of the rubber core 12, is then slid over the rubber core 12. To facilitate this sliding operation, it may be desirable to coat the core material 12 with talcum powder. While the core material 12 remains stretched, the overbraid 14 is seized to the rubber core 12 by means of the glass reinforced tape 16. Although the separation between places where the seizing takes place is not critical, it is preferred that the separation be approximately 5 feet when the accumulator is in its relaxed state. Thus, after the overbraid 14 has been seized to the rubber core 12 by means of the tape 16, when the accumulator 10 is allowed to resume its relaxed state, the overbraid 14 will tend to bunch up and loosely surround the rubber core 12. The diameter of the accumulator 10 in its relaxed state is thus about 2.25 inches, substantially greater than the 1 3/8 inch diameter of the core. This degree of looseness of the overbraid provides hydrodynamic damping which is desirable for mooring sensitive instruments in an ocean wave environment. The final operation is terminating the ends in loops. As can be seen in the figure, the loops include galvanized steel thimbles 18 surrounded by the core material 12 and overbraid 14. The loop around the thimbles 18 is made by the conventionally known technique of splicing an overbraided material which is often known as the "Chinese Finger Puzzle" principle. In such a case, the more tension that is placed on the accumulator, the tighter the nylon braid grabs to make a secure termination.

During operation, as the accumulator 10 begins to stretch, all of the load is carried by the rubber core 12, because the nylon overbraid 14 is very loosely surrounding the core 12. When, however, the accumulator 10 is stretched to approximately three times its relaxed length, the strands of the nylon overbraid 14 go into tension and carry the full load. As discussed above, since the core element itself can stretch about 700%, stretching 300% will not break the rubber core. In this way maximum loads of 15,000-17,000 lbs. can be maintained before the accumulator 10 breaks. Because the accumulator 10 can stretch to approximately three times its relaxed length, loads encountered at sea are reduced so that sensitive instruments are not damaged in a rough sea environment. In addition, the accumulator 10 has a high ultimate breaking strength to avoid breakage and instrument loss even in severe storm conditions.

It is to be noted that the accumulator 10 can be made in a variety of lengths and diameters. The accumulator 10 shown in FIG. 1 has a preferred active or relaxed length of about 46 feet, and the rubber core 12 has a diameter of about 1 3/8 in. For this embodiment, about 400 lbs. are required to stretch the accumulator to three times its relaxed length. An accumulator might also have a rubber core with a 1 in. diameter, in which case about 200 lbs. are required to stretch it to three times its relaxed length.

It is thus seen that the objects of this invention have been achieved in that there has been disclosed an accumulator which is capable of a 300% elongation and which has an approximately 15,000 lb. breaking strength. The accumulator is resistant to abrasions since the inner elastic core is surrounded by a tough nylon braid having a high tensile strength. The accumulator disclosed herein is easy and inexpensive to manufacture and has terminations which are resistant to slippage.

It is recognized that variations and modifications will occur to those skilled in the art, and it is intended that all such modifications and variations be included within the scope of the appended claims.