US2577077A - Buoyant tow and communication line - Google Patents

Description

1951 G. E. FORSBERG 2,577,077

BUOYANT TOW AND COMMUNICATION LINE Filed June 2, 1947 HIGH MOLECULAR WEIGHT F G I SAPONIFIED CELLULOSE ACETATE,

CONTINUOUS BODY OF ELECTRIC INSULATING POLYETHYLENE ELECTRIC F 3 CONDUCTOR HIGH MOLECULAR WEIGHT SAPOEEIED CELLULOSE ACETATE,

ECTRIC INSULATING 6 FIG. 5 CONT'NUOUS BODY OF POLYETHYLENE 23 24 26 L' 2 6 ELECT RIC CONDUCTOR INVENTOR aEoRaE E. FORSBERG wmww ATTORNEY Patented Dec. 4, 1951 UNITED STATES PATENT OFFICE BUOYANT TOW AND COMMUNICATION LINE George E. Forsberg, Worcester, Mass., assignor to Surprenant Electrical Insulation Company, Clinton, Mass., a corporation of Massachusetts Application June 2, 1947, Serial No. 751,679

4 Claims. (Cl. I'M-101.5)

This invention relates to improvements in buoyant tow and communication lines for marine operations and it is the general object of the invention to provide a composite tow line containing relatively heavy elements sufficiently strong to withstand considerable tension inclosed in a light weight water resistant coating or sheath which causes the line to float in water.

In certain naval landing operations it is necessary to connect a small boat to a mother ship by a tow line which can be reeled in to draw the boat away from enemy fire. Several attempts have been made to provide such a line, but they have been unsatisfactory either because they did not have the requisite strength, or the floats used to keep them on the surface of water interfered with reeling. In order that the small boat may be under immediate control of the mother ship it is important that the tow line be able to float so that it can remain substantially straight. The sea floor is not always smooth and may have formations such as coral with which a tow line would become entangled if it sank. The line should also be flexible to permit coiling, and should be non-absorbent to prevent increase in weight when immersed.

Itis an important object of the present invention to provide a tow line made of strong cords or cables heavier than water surrounded and kept dry by an inclosing sheath made of material having a specific gravity less than that-of water and of suflicient size to cause the line to float in water.

It is a more specific object of the invention to make the cords or cables of high tensile strength relatively heavy plastic or artificial fibers or filaments and make the sheath of a light weight extrudable plastic. The cables may be made of a saponified cellulose acetate type of extruded fiber, while the sheath may be made of polyethylene. The cables carry the greater part of the load, but their stretch or elongation in use is within the elongation limits of the sheath and the latter remains intact without breaking or cracking.

The occupants of the small boat should be able to communicate with the mother ship and to this end it is a further object of the invention to inclose small electric conducting wires within the tow line so that telephone connections may be maintained between the two vessels.

If enemy fire is such as to require withdrawal of the landing party the mother ship will reel in the tow line and the small boat will follow a zigzag course to avoid gun fire. In order that such a course may be impeded as little as possible by the line the latter is so made that it will lie flat on the water surface and cut the water edgewise as the small boat moves first to one side and then the other.

The invention is not limited to tow lines, and may for instance be adapted for use in diving operations.

With these and other objects in view which will appear as the description proceeds, my invention resides in the combination and arrangement of parts hereinafter described and set forth.

In the accompanying drawings, wherein two forms of the invention are set forth,

Fig. 1 shows a plan view of the preferred form of the invention adapted more particularly for towing operations,

Fig. 2 is an enlarged vertical section on line 2--2, Fig. 1,

Fig. 3 is a detailed view of one of the cords or cables inclosed in the tow line set forth in Fig. 1, certain of the strands being opened out to show the location of the electric Wire carrying strand.

Fig. 4 is an enlarged transverse section on line 4-4, Fig. 3..

Fig. 5 is a view similar to Fig. 1 but showing the modified form of the invention adaptable more particularly to diving operations,

Fig. 6 is an enlarged transverse section on line B6, Fig. 5,

Fig. 7 is a view similar to Fig. 3 but showing the cable used with the modified form of the invention, and

Fig. 8 is a diagram indicating how the preferred form of the invention is used in naval operations.

Referring more particularly to Figs. 1 to 4- which illustrate the preferred form of the invention, the tow and communication line L includes two cords or cables l0 and II spaced from each other and extending side by side throughout the length of the line. Each cable is made up of several peripheral strands I 2 surrounding a central or inner strand l3, and each strand is formed of a plurality of filaments or threads l4 twisted on themselves as indicated in Fig. 3. Each central strand I3 may have wrapped therearound a metallic electric conductor 15 which may include several separate tin coated copper wires. Each conductor 15 is insulated by the peripheral strands 12 which are wrapped hellcally around the central strand as shown in Fig. 3. The two cables l0 and H are inclosed within a water resistant electric insulating plastic sheath I8 which is lighter than water and is of such size as to cause the line to float in water. Part of the sheath is located between the cables and holds them in spaced substantially parallel relation throughout the length of the tow line,

see Fig. 2.

In the manufacture of the preferred form of the invention the conductors or copper wires I5 are first wrapped helically around the central strands !3. The other strands 12 are then wrapped around the central strands to form a cable. Two cables thus made are then drawn through a suitable die and the solid plastic sheath or jacket I8 is extruded around them. Because of this mode of manufacture the tow line can be made of any desired length, and the sheath l8 fits closely into the spaces between the strands and threads to establish a strong connection with them. The wires l need not be present for all uses of the invention, and may be omitted if telephone commumcation is not needed. As shown in Fig. 2 the width of the tow line is greater than its thickness and for this reason the tow line can be wrapped on a drum or the like, and will also tend to lie flat in water.

In Fig. 8 it is assumed that the small boat B is being drawn away from the shore S by the mother ship M. The line L will be attached to the boat in any approved manner and the mother ship will have a reel IS on which the tow line is wound. When the telephonic signal to withdraw is given the ship M will move away from the shore and the boat B will be guided by the occupants to pursue a zig-zag course to avoid enemy fire by manipulating rudder ll. When the boat moves as indicated by dotted line a the tow line will move from the full line to the dotted line position. Since the tow line L is flat and floats it will cut the water edgewise and offer a minimum of resistance to lateral movement as the boat zigt zags.

The modified form of the invention, shown in Figs. 5 to 7, is adapted more particularly for use in diving operations to connect the helmet of the diver with the ship conducting the diving operation. The line L is preferably of circular cross section with the strands located centrally thereof, and the electric communicating wires are wrapped around certain of the strands which are spaced from each other by other interposed strands.

Referring to Fig. 6, the central or inner strand 20 is similar to strand l3 of the preferred form of the invention and has wrapped therearound an electric conductor 2| similar to conductor l5. Surrounding strand 20 is a group of strands 22 similar to strands l2 of the preferred form. In addition, there is a. third group of strands 23 around the inner group, one of these latter strands, indicated at 23a, being similar to the central strand in that it is wrapped with an electric conducting wire 24. The group of strands 22 is thus located between the wire carrying strands 20 and 23a to keep the electric conductor wires of these two strands insulated from each other throughout the length of the line. The strands 2|], 22, 23 and 23a together form a cable 25 or more or less circular cross section as indicated in Fig. 6. The core 25 is surrounded by a plastic sheath 26 similar to coating or sheath l8 and of such volume as to cause the line L to float in water.

The manufacture of the modified form of line L is similar to that of the preferred form and results in a line the various component parts of which are held in close relationship with each other. The surrounding sheath 26 is embedded partly at least in the strands 23 and 23a, and also provides insulation for the electric wires, particularly the wire around strands 23a.

The threads l3 and H of the strands have high tensile strength, and may be made of deacetylated or cold drawn high molecular weight saponified cellulose acetate fibers or filaments which are ordinarily heavier than water. In practice I have used a material known in the trade as "Fortisan" having a specific gravity of 1.5, but I do not wish to be thus limited, as any strong and relatively heavy fiber possessing the general properties of Fortisan, such as nylon, can be used to make the threads. The material of which the cables 10, H and 25 are made W111 ordinarily be electric insulating and heavier than water and of themselves would sink if used as tow lines unless supported by the sheaths. In order to prevent possibility of chemical action between the fibers and copper wires the latter are coated with tin.

Tne plastic sheath for the cables is lighter than water and is present in sufficient amount to counteract the tendency of the cables to sink. The sheaths l8 and 26 may be made of a high molecular weight plastic, such as polyethylene, which has sufiicient strength in tension and compression at ordinary temperatures to withstand the uses to which it is put. Polyethylene has a specific gravity of approximately 0.92 and is flexible, electric insulating, chemically inert, and will stretch at least as much as the cables in normal use without rupture. Since the sheath has a very low factor of water absorption it keeps the cables dry.

The form of the invention shown in Fig. 6 has been described as suitable for diving operations, but by the omission of the electric wires and a reduction in size with fewer strands such a cable can be adapted to use as a clothes line. In this connection I have used seven strands, six around a central strand, and coated the cable thus formed with a sheath made of polyethylene. The seven strand cable is similar to one of the cables of the preferred form of the invention without the wires, the fibers of the threads composing the strands being preferably though not necessarily extruded and having considerable strength. The fibers can be similar to those used in the tow line form of the invention. For clothes line use the sheath will be relatively thin, and since the cable will be compressible to some extent due to the flexibility of the strands, the clothes line can be deformed slightly by a clothes pin to prevent slipping along the smooth surface of the sheath. While this may be a desirable feature in some instances, I do not wish to be limited to it.

In practice I find that polyethylene and similar plastics suitable for use as described hereinbefore are subject to crazing when exposed to strong light, such as exists in certain marine areas where landing operations may be made. Thi crazing is due to penetration of the sheath by light rays, and in order to prevent such penetration I incorporate preferably opaque coloring matter in the material of which the sheath is made prior to extrusion thereof. For naval operations the color may be a gray which will make the line invisible except at very close range. For diving operations a color readily distinguished in water may be used, while for clothes line use a white pigment such as titanium oxide may be used.

The sheath is made of plastic material prefer ably lighter than water and for this purpose polyethylene is quite acceptable, but it will be apparent that any other sufficiently light weight material, such as expanded or cellular cellulose acetate, may be used if desired. It will be sufllcient for the purposes of the invention if the materials of which the line is made are of such volume and weight that the line as a whole has the requisite strength and floats in water. The plastic sheath which incloses the cables should be resistant or impervious to water and of good insulating properties when communication wires are used. The cables carry the greater part of the load and have an elongation when normally loaded within the elongation limit of the sheath. The latter therefore does not break or crack when the line is in tension, and the communication wires are protected and can be used for telephone purposes while the small boat or diver is being reeled in by the mother or attendant ship. Also, the tow line of the preferred form lies fiat on water and cuts the latter edgewise when the small boat follows a zig-zag course.

From the foregoing it will be seen that I have provided a simple tow line made of materials chosen for their weight and volume to be sufliciently strong to serve as a tow line and also float in water. The cables are kept dry by the sheath and preserve their strength while the line is in use. Both forms of line can if desired be made with telephone communication wires. In the preferred form of the invention two cables arranged side by side are surrounded by a plastic material impervious to and lighter than water and of suflicient volume to cause the line to float. More than two cables can be used if greater strength is desired. The modified form of the invention has a single cable and the electric wires, if used, are wound around strands which are separated from each other by other strands so that the wires are kept insulated from each other. The cables can be made of a deacetylated or cold drawn high molecular weight saponified cellulose acetate. Furthermore, an anti-crazing agent, such as an opaque pigment, may be used to prevent cracking or deterioration of the sheath by light. When adapted for hanging clothes the line will be of relatively small cross section but will otherwise be similar to the form used for diving operations.

Having thus described my invention it will be seen that changes and modifications may be made therein by those skilled in the art without departing from the spirit and scope of the invention and I do not wish to be limited to the details herein disclosed, but what I claim is:

1. In a combined communication and tow line, an inner strand heavier than water composed of a plurality of high molecular weight saponified cellulose acetate threads, an electric conductor wrapped around said strand, a plurality of peripheral stands heavier than water each composed of a plurality of high molecular weight saponified cellulose acetate threads disposed around said inner strand, and a sheath lighter than water made solely of a continuous body of polyethylene surrounding and in contact with said plurality of peripheral strands, the latter strands spacing the conductor rrom the sheath, and the specific gravity of the communication and tow line as a whole being less than that of water.

2. In a combined communication and tow line, an inner strand composed of a plurality of high molecular weight saponified cellulose acetate threads heavier than water, an electric conductor wrapped around said strand, a plurality of peripheral strands each composed of a plurality of high molecular weight electric insulating saponifled cellulose acetate threads heavier than water, said peripheral strands being disposed around said inner strand and insulating said conductor, and a sheath made solely of a continuous body of polyethylene lighter than water surrounding and in contact with said peripheral strands, the latter strands being located between the sheath and conductor and wrapped helically around the latter, and the specific gravity of the communication and tow line as a whole being less than that of water.

3. In a combined communication and tow line, a central strand composed of a plurality of high molecular weight saponified cellulose acetate threads, an electric conductor wrapped around said strand, a plurality of peripheral strands each composed of a plurality of high molecular weight saponified cellulose acetate threads, said peripheral strands being wrapped around said central strand and conductor, said strands and conductor being heavier than water, and a sheath made solely of a continuous body of polyethylene lighter than water surrounding and in contact with said peripheral strands, the latter strands spacing the conductor from the sheath, and the specific gravity of the line being less than that of water.

4. In a combined communication and tow line, a central strand composed of a plurality of electric insulating high molecular weight saponified cellulose acetate threads twisted on themselves, an electric conductor wrapped around said central strand, a plurality of peripheral strands wrapped around said central strand and conductor, each of said peripheral strands being com- Posed of electric insulating high molecular weight saponified cellulose acetate threads wrapped on themselves, said central and peripheral strands and conductor being heavier than water, and a sheath made solely of a continuous solid body of polyethylene lighter than water surrounding and in contact with said peripheral strands, the latter strands spacing the conductor from the sheath, and the line as a whole having a specific gravity less than that of water.

GEORGE E. FORSBERG.

REFERENCES CITED The following references are of record in the file of .this patent:

UNITED STATES PATENTS Number Name Date 563,274 Guilleaume July 7, 1896 1,978,041 Dodge Oct. 23, 1934 2,133,301 Martin Oct. 18, 1938 2,145,153 Christiansen et al. Jan. 24, 1939 2,175,389 Hauif Oct. 10, 1939 2,235,523 Hull Mar. 18, 1941 2,319,312 Finlayson May 18, 1943 2,336,219 Brown Dec. 7, 1943 2,376,813 Robins et a1 May 22, 1945 2,382,355 Warren Aug, 14, 1945 2,409,660 Briggs Oct. 22, 1946 2,418,192 Pierce Apr. 1, 1947 2,424,388 Duna July 22, 1947 2,435,956 Craig Feb. 17, 1948 2,454,800 Hartenstein et al. Nov. 30, 1948 FOREIGN PATENTS Number Country Date 5,275 Great Britain of 1894 OTHER REFERENCES Sherman: The New Fibers (1946), page 280. (Copy in Div. 21.)

An Article: A New Dielectric for Cables, by Cratton and Slade; found in Modern Plastics for July, 1944, pages -93. (A copy in P. 0. Library.)

Ser. No. 298,490, Hoekstra: (A. P. C.) published May 18,1948.

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