US3296996A - Method and apparatus for slowing the forward speed of a towed submerged vessel - Google Patents

Description

114-253. XR 3,296,996 SR an. 10, 1967 w. J. MILLER 3,296,996 METHOD AND APPARATUS FOR SLOWING THE FORWARD SPEED 1 OF A TOWED SUBMERGED VESSEL Filed March 24, 1965 2 Sheets-Sheet 1 ELLE-r4 Tia-5 A TI'OP/VEY Jan. 10, 1967 w. J. MILLER 3,296,996

METHOD AND APPARATUS FOR SLOWING-THE FORWARD SPEED OF A TDWED SUBMERGED VESSEL Filed March 24, 1965 2 Sheets-Shet 2 fits- E INVENTOR. W/LL /'A M d. 1L4/L4 E-Q A TTOQA/EY 3,296,996 PatentedJan. 10, 1987 3,296 996 5 METHOD AND APPARATUS FOR SLOWING THE FORWARD SPEED OF A TOWED SUBMERGED VESSEL William J. Miller, Ponca City, Okla, assignor to Contimay occur, or that the tow line may become fouled in nental Oil Company, Poaca City, Okla., a corporation of Delaware F lied Mar. 24, 1965, Ser. No. 442,285

25 Claims. (Cl. 114-235) invention relates to amethod for deceleratingv a subspeed by'fa towirig slung: it has previously been proposed to provide cargo carrying submersibles which can be moved by a towing vessel 7 through relatively deep bodies of water at relatively high speeds while submerged. Transport of cargoes such as crude oil and other liquids by this method presents a number of advantages over surface transport. These advantages may be generally summarized as the relatively great improvement in the economy of locomotion of the cargo carrying vessel which is achieved, the reduction in manpower requirements for servicing the towed vessel and maintaining it on a correct course during the tow, and, lastly, a saving in maintenance cost of the towed cargo vessel as a result of the avoidance of structural deterioration which normally results in surface cargo vessels due to subjection of the vessel to wave action and high winds which are encountered during surface towing.

With the recent development of a submersible which can be towed at a predetermined depth in the water at relatively high speeds with a high degree of control of buoyancy and depth, large cargoes of crude oil or other liquids can be towed over substantial distances at a fraction of the cost which would be entailed in moving the same cargo by surface transport. One successful recent development permits the submersible barge to be towed at a depth of from 10 to 40 meters at speeds up to 14.5 knots while carrying a cargo of at least 5,000 tons of crude oil. The drag imposed upon the towing vessel has been reduced to the extent that, at speeds of about 15 knots, only about 1 knot of speed is lost by the towing vessel as a result of the submerged tow.

The development of a submerged barge which encounters a minimum of resistance to its forward movement as a result of hydrodynamic forces gives rise to a serious problem which must be overcome before the barge can be safely towed at relatively high speeds. Concisely stated, this problem is that of rapidly decelerating the tow at any time when continued forward movement of the tow will ultimately present a hazard to the towing vessel, or to any object forward of the tow in its line of movement. sirability of being able to quickly decelerate the tow under circumstances where a decrease in tension on the tow line interconnecting the tow to the towing vessel is likely to result in the movement of the submerged vessel through the water becoming erratic, and particularly, where the submerged vessel is characterized in having hydrodynamic characteristics which will permit it to dive when tension is decreased in the tow line.

A condition sometimes requiring rapid deceleration of the submerg d vessel will be that occurring when the towing vessel finds it necessary to come to an emergency stop, or to back down full in order to rapidly reduce the way on the towing vessel. In this situation, it will be apparent that the submerged vessel, unless braked or decelerated in some manner, will quickly overtake the towing vessel with the result that a disastrous collision Another aspect of this problem is the de-' the screws of the towing vessel. In a recent design of submersible barge, a reduction in the tension of the tow cable which may result from an emergency stop on'the part of the towing vessel can also permit the barge to rapidly dive to an excessive depth as the result of the'inclination of diving planes provided on the barge. This situation may cause the hull of the submersible barge to be ruptured by excessive hydrostatic pressure. or. in one barge design, may require the employment of emergency pressure sensitive equipment to blow reserve ballast cartied by the barge. thereby causing it to rise to the surface. Difficulties of reballasting the barge are then presented. which in some designs, cannot be overcome while underway or adrift in the high seas, but can be effected only by returning to port.

Another situation which may make it highly desirable to rapidly decelerate the tow is that which may be experienccd where the towing ship must necessarily undergo an emergency turn. In this. situation, the turning radius which can be achieved by the towing vessel may be considerably smaller than the turning radius of the towed submersible with the result that the submersible swings through a wider arc than the towing vessel and may collide with any objects outside the turning radius of the towing vessel unless in some manner decelerated.

Under any of the described'conditions making it clesirable to rapidly decelerate or brake the submerged barge, reliance upon devices carried by. or located within. the towed vessel for accomplishing such deceleration presents certain disadvantages. The use of sea anchors or other devices carried on the tow and actuated by an electrical circuit connected between the towing vessel and the tow. or any similar type of device actuated from the tow. would, in most instances, require that the tow be stopped and brought to the surface in order to reset the braking device and prevent it from retarding the normal movement of the tow through the water following the emergency. Alternatively, if it were necessary to reach the braking device or the connections thereto during the towing omrations and without surfacing the tow. a diver would be required and special tools for underwater work would be necessary. Extending electrical circuitry or other actuating means between the towing vessel and the tow also presents certain technical difficulties.

The present invention comprises a method and apparatus for decelerating a submerged towed vessel, which device can be actuated and controlled from the towing vessel and which can be returned to an inactivated status immediately after the submerged vessel has been decelerated to the extent desired. Inactivation of the braking apparatus can be accomplished without access to the towed vessel, and therefore without the requirement that the towed vessel be brought to the surface. The apparatus employed in the invention to accomplish deceleration does not provide any interference with the forward movement of the towing vessel by the submerged towed vessel during normal operation when the device is inactivated. Moreover, the braking device can be made compact in size to facilitate storage at times when it is not in use, and is relatively simple and inexpensive in construction.

Broadly described, the brakin devii used in practicing the method of the present invention comprises means for resisting fluid flow slidably mounted on the tow line interconnecting the towing vessel with the submerged flow resisting means along the luw line, said control means being connected to and operable from the towing vessel. Most embodiments of the bnking device also include shock absorbing means disposed along the tow line between the fiuid flow resistance means and the towed vessel for cushioning the impact of the towed vessel with the resistance means. In a preferred embodiment of the invention, the means for resisting fluid flow comprises an annular body slidably surrounding the tow line and a plurality of elongated hydrodynamic resistance fins extending radially from the body for'opposing fluid flow .thereby in the direction of the towed vessel. 2

It should be pointed out that the fluid flow resistance means accomplishes its braking or decelerating action by the resistance which it ofifers to the flow of water past the device, and also by the creation of a turbulent condition around the hull of the submerged tow, imposing a drag thereon, and interfering with the hydromatic streamlining of the tow so as to cause it to encounter more resistance to continued forward movement through the water. The method of the invention can thus be summarized as moving on the tow line which interconnects the submerged tow and the towing vessel, a turbulence generating and fluid flow resistance device which offers greater resistance to the flow of water thereby than does the submerged vessel, such movement of the device being from a position on the tow line which is above the water and adjacent the towing vessel to a position in the water and closer to the submerged vessel.

As the turbulence generating and fluid flow resistance device is moved to this position in the water, the towing vessel continues to move away from the device and to simultaneously pull the tow line through the turbulence generating and fluid flow resistance device so that the submerged tow converges on the device until the device is contacted thereby. Continued forward movement of the submerged tow and the fluid flow resistance device is then opposed by the turbulence generated by the device and the resistance offered by the device to fluid flow thereby until the submerged tow has been decelerated to the desired extent. As the final step in the process, the turbulence generating and fluid flow resistance device can be returned to its original position by movement along the tow line, using movement control means actuated from the towing vessel.

From the foregoinng description of the invention, it will have become apparent that it is a major objective of the present invention to provide aiwmparatus for de- An additional object of the present invention is 5 56 vide a device for decelerating a submerged tow, which device is continuously within the control of the towing vessel, is not carried by, or directly connected to, the submerged tow at any time during its use, and can be returned to an inactivated status without the nece ssit oi Restor ng rn q ch so a d h E T- An additional object of the present invention is to provide apparatus for decelerating a submerged tow, which apparatus is relatively simple and inexpensive in construction, and can be utilized successfully a plurality of times without mechanical failure.

In addition to the foregoing objects and advantages, additional objects and desirable features of the present invention will become apparent as the following detailed description of the invention is read in conjunction with the accompanying drawings which illustrate the invention.

In the drawings:

FIGURE 1 is a somewhat schematic illustration of the environment of the use of the present invention, and depicts a submerged barge being towed astern of a towing vessel by means of an interconnecting tow cable which carries one embodiment of the decelerating device of the present invention.

FIGURE 2 is an enlarged perspective view of the embodimcnt of the decelerating device schematically illustrated in FIGURE 1.

FIGURE 3 is a view in section taken through the longitudinal axis of the decelerating device shown in FIGURE 2 and illustrating various details of construction of the device.

FIGURE 4 is a view in elevation of a modified embodiment ofthe decelerating device of the invention.

FIGURE Sis a view in elevation of another modification of the decelerating device of the invention.

FIGURE 6 is a detail sectional view illustrating a particular'structure which may be used in combination with the movable elements of the decelerating device of the invention for cushioning the impact of the decelerating device With the towed vessel during the practice of the method of the invention.

Referring now to the drawings in detail, and particulariy to FIGURE 1, a submerged tow, such as a submersible barge 10, is connected by a flexible tow line 12 to the stern of a towing vessel 14. The barge 10 is a streamlined, hydrodynamically stable craft which is specially designed for underwater movement, and which contains suitable compartmentation (not shown) for the transport of crude oil or other liquids. The tow line 12 is preferably a suitable multi-stranded steel cable of from 1 to 3 inches in diameter, and in normal towing situations may be streamed from the towing vessel 14 so that a length of from 300' to 1,500 feet of cable extends between the towing vessel 14 and the tow 10. A suitable capstan or winch 16 is positioned on the stern or fantail of the towing vessel 14, and one end of the tow line 12 is reeled thereon so that the line can be paid out or retrieved by the winch. Preferably, an automatic tensioning device (not shown) is associated with the winch 16 for maintaining a relatively constant tension in the tow line 12 for purposes hereinafter described.

Under normal towingconditions, the decelerating device 18 of the present invention is movably mounted on the tow line 12 in a position which is above the water and relatively close to the stern of the towing ship 14. The decelerating device 18 is retained in this position by a return cable 20 which extends through suitable checks in the fantail of the vessel 12 to a small capstan or winch 22. The winch 22 is free running in one direction so that little or no resistance is offered to the paying out of the return cable 20 when a brake (not shown) is released to permit the decelerating device 18 to move down the tow line 12 toward the tow 10. It is further highly desirable that the brake release (not shown) of the return cable 20, and also the motor and clutch (not shown) for driving the winch 22 in a direction to return the decelerating device 18 to the position illustrated in FIGURE 1 include remote control electrical or hydraulic circuitry to permit this apparatus to be operated from the bridge of a towing vessel 14.

The details of construction of one embodiment of the decelerating device of the invention are best illustrated in FIGURES 2 and 3. The device includes an annular body which may suitably take the form of a sleeve 24 dimensioned to slidably encircle the tow line 12. The sleeve 24 is preferably provided with a plurality of friction reducing elements, such as wheels or rollers 26, rotatably mounted in the sleeve 24 at each end thereof and projecting radially inwardly from the sleeve to bear against the tow line 12.

At its end closest to the tow 10, the sleeve 24 is connected to and supports a shock absorbing device designated generally by reference character 28 which includes an annular flange 39 secured to the sleeve 24, a plurality of piston elements 32 extending from the flange 30 axially along, and spaced outwardly from, the sleeve 24, and a plurality of apertured cylinder 34- which function conjunctively with the pistons provide a dashpot action in the shock absorber 28. The cylinder: 3! are secured to' a base plate 36 which encircles, and is bonded to, an elastomeric annular cushion 38 which projects axially along the tow line 12 from the retainer flange 36. The

annular cushion 38 is carried by anapnular ring 40 which loosely and slidably encircles the tow line 12. A helical' Slidably mounted on the sleeve 24 is a turbulence generating, fluid flow resistance means designated generally by reference character 44. The turbulence generating, fluid flow resistancemeans 44 includes an annular resistance fin collar 46 which slidably surrounds the sleeve 24 and is axially movable therealong, and an annular retrieving ring 48 which is positioned on the towing vessel side of the sleeve 24 from the fin collar 46. The retrieving ring 48 is dimensioned to loosely encircle the sleeve 24, and in FIGURE 3, is shown in contact with a bumper ring 50 fins 52 is connected by a rigid brace 54 to the retrieving ring 48. The opposite ends of each brace 54 are pivotally connected to the respective resistance fin 52 and a lug 56 on the retrieving ring 48 so that as the distance separating the fin collar 46 from the retrieving ring 48 is varied, the rigid resistance fins 52 are pivoted about their points of pivotal connection to the fin collar 46. Thus, the rigid resistance fins 52 may be pivoted from a flared or expanded, radially extending position as illustrated in FIG- URE 2, to a collapsed, compact position as illustrated in FIGURE 1. Preferably, in collapsing the resistance fins 52 to the inactive status illustrated in FIGURE 1, the fins are moved inwardly toward the sleeve 24 to a position such that each of the fins define an angle of less than 45 with the axis of the sleeve. Most preferably, the fins 52 are moved into near parallelism with the axis of the sleeve 24. In order to prevent the resistance fins 52 from overriding their radially expanded positions under the influence of water pressure, the bumper ring 50 is positioned to prevent the retrieving ring 48 from moving too far along the sleeve 24.

A plurality of flexible members 60 interconnect adjacent resistance fins52 at points relatively close to the outer or free ends of the fins. .The flexible members 60, which may conveniently be chains, are preferably slightly shorter in length than the distance between the two points on the adjacent fins which each of them interconnects, as such distance would exist at a time when the fins are ,moved into a truly radial position relativeto the fin collar 46 or, stated differently, "to a position in which they extend at precisely 90 from the axis of the sleeve 24. Thus, in addition to their major function as turbulence generating and fluid flow. resistance elements, the chains 60 also limit the pivotal movement of the resistance fins 52 to an angle of slightly less than 90 and prevent the fins from being forced by hydrostatic pressure to a position beyond their preferred radial arrangement illustrated in FIGURE 2. The chains 60 also prevent lateral bending of the fins 52 under hydrodynamic pressure.

Positioned between the lugs 56 on the retrieving ring 48 is at least one return cable pad eye 64. Preferably, a pair of the return cable pad eyes 64 are located on opposite sides of the retrieving ring 48, and are connected to the ends of two branches of the return cable 20. The other end of the return cable is, as previously indicated, connected to the return cable winch 22 located on the stern of the towing vessel 14.

A modified embodiment of the decelerating device of the invention is illustrated in FIGURE 4. In this form of the invention, the turbulence generating and fluid flow resistance means 44 takes the form of an annular propeller hub 68 which is rotatably mounted on the sleeve 24 by means of suitable bearings (not shown). At least two propeller blades 72 extend radially outwardly from the hub 68 and are pitched to assure that a rapidly rotating movement will be imparted to the blades 72 and hub 68 I by hydrostatic pressure exerted on the faces of the prope'ller blades. A bearing 74 is provided between the hub 68 and the flange 30 of the shock absorbing device 28 to prevent frictional drag on the hub as a result of its contact with the shock absorbing device. In the FIGURE 4 embodiment of the invention, the pad eyes employed for connecting the return cable 20 to the decelerating de'- vice are secured to the sleeve 24 adjacent the forward end thereof and are designated by reference character 76.

Yet another embodiment of the invention is illustrated in FIGURE 5 of the drawings. In'this construction pad eyes 76 have again been provided at the forward end of the sleeve 24 for connection to the return cable 20. The turbulence generating and fluid flow resistance means, howeyer, takes the form of a plurality of cup-shaped turbulence ijenerating elements 78 which are connected by flexible lines 80 to lugs 82 secured in circumferentially spaced relation to each other around the sleeve 24. In a preferred construction of this embodiment of the invention, the tar bulence generating elements 78 each comprises a drogue which deflects the water outwardly as it passes over the external surface-thereof and thus creates a substantial turbulence in the wake of the drogue and over the skin of the tow, as well as offering substantial resistance to the flow of water past the drogue. The lengths. of the flexible lines 80 interconnecting the cup-shaped turbulence generating elements 78 with their respective lugs 82 is such that in the operation of the decelerating device as hereinafter described, the elements 78 can be streamed by their lines 80 a sufiicient distance to the rear of the de ticing the method of the present invention is deserving of consideration. This element is shown in FIGURE 6 of the drawings, and comprises a bumper 84 of elastic material which is secured immediately adjacent the end of the tow line 12 which is connected, or made fast, to the bow of the tow 10. The bumper 84 may be constructed of rubber or any other suitable elastomer having a high degree of elasticity and corrosion resistant characteristics. As an alternative construction to that depicted in FIGURE 6, the elastic bumper 84 may be fixed to the bow of the barge 10 and configured so that the tow line 12 may be passed through the center of the mass of the elastomer and attached to the bow of the barge.

Operation The declerating device of the invention is used when the tow 10 is connected through the tow line 12 to the towing vessel 14 in the manner illustrated in FIGURE 1. At this time, the towing vessel 14 and tow 10 both have way on and the towing vessel may frequently be cruising at a relatively high speed such as, for example, about 14 to 16 knots. In this situation, the decelerating device 18 is retained by the return cable 20 in the position illustrated in FIGURE I, that is, relatively close to the stern of the towing vessel 14 and above the water. It will be noted that in the case of the embodiment of the decelerating device 18 which is illustrated in FIGURE 2, the resistance fins 52 are in their collapsed status and lie generally along the axis of the sleeve 24. This condition is brought about by the pullof the return cable 20 on the retrieving ring 48, a

At any time that it becomes desirable or necessary to rapidly brake or decelerate the movement of the tow 10 through the water, the return cable 20 is released to run freely from the winch 22. This permits the decelerating device 13 to slide down if" line 12 into the water.

.2 -During this movement of the lerating device 18, the

tension in the tow line 12 is maintained relatively constant by the constant tensioiting device associated with the winch 16, despite variations in the distance between the tow l0 and the towing vessel 14.

when the decelerating device 18 moves into the water in its movement along the tow line 12, the movement of the water relative to the decelerating device actuates the turbulence producing-fluid llow resistance elements. In the cas of the embodiment of the decelerating device illustrntzxin FIGURES 2 and 3, this hydrodynamic actua lion consi. ts of flaring or expanding the resistance fins 52 to the illustrated position.

. in FIGURE 4 of the drawings, the propeller blades 72 it soon comes to rest therein and the relative movement of the towing vessel 14, tow line 12 and tow 10 relative to the decelerating device is such that the tow line 12 continues to move through the decelerating device in the direction of the towing vessel and thetow 10 rapidly approaches the decelerating device. The towing vessel 14 meanwhile continues to move away from the decelerating device so that the net effect may be considered to be a relative movement of the decelerating device down the tow line 12 to the tow 10. It will be perceived that the tow 10 will move through the distance to the decelerating device 18 at a speed substantially equivalent to the velocity of the water past the tow.

When the tow 10 contacts the decelerating device 13, a considerable impact results, and a portion of the energy lost in the impact is absorbed in the shock absorbing device 28 so that the decelerating device is not damaged.

With the decelerating device 18 hearing against the bow of the tow 10, both the tow and decelerating device continue to move forward through the water at the same speed. The decelerating device 18, however, olfers substantial resistance to the flow of water thereby, and additionally, creates a substantial turbulence in the water which creates a drag on the hull of the tow 1 0. The combined flowresistance and turbulence effects of the decelerating device cause the tow 10 to slow its forward motion to an extent such that a collision with the towing vessel 14 can be avoided and, in cases where no means is provided for maintaining constant tension in the tow line 12, fouling of the screws of the towing vessel by the tow line is avoided.

It will be apparent that one of the most useful applications of the decelerating device 18 is in permitting the tow 10 to be safely controlled in its movements at such time as it may become necessary to make an emergency stop or turn with the towing vessel 14. In such a situation, where the system is constructed for remote control from the bridge of the towing vessel, the captain of the towing vessel can release the return cable 20 from the bridge at the same instant that the command to reverse engines is given to the engine room. Since it normally will take several seconds for the screws to be reversed, and several additional seconds for the effect of such reversal to be felt on the towing vessel 14, the decelerating device 18 will normally be well on its way to the tow 10 before any substantial deceleration of the towing vessel 14 occurs.

The decelerating effects obtainable by the use of the several embodiments of the decelerating device 18 illustrated in the accompanying drawings are generally similar. The understanding of the invention may be further enhanced, however, by briefly describing the manner in which each achieves such decelerating-effects. In the case of the embodiment illustrated in FlGURES 2 and 3, the radially extending resistance fins 52 resist flow of the water thereby and result in a gradually increasing braking force. The second action of the resistance fins 52 is to set up a turbulent condition behind the fins which causes a corresponding increase in the skin resistance of the tow 10. The tow is thereby caused to slow its forward speed.

and hub 74 are caused to rotate rapidly upon the sleeve 24 by the hydrostatic pressure of the passing water. The propeller thus causes actually less drag due to frictional resistance to thepassage of water than it would were it not permitted to rotate on the sleeve 24. The turbulence which is created by the rapidly rotating propeller is, however, the primary decelerating effect attributable to this embodiment of the invention, and this turbulence causes a considerable braking action due to its friction and drag upon the skin of the tow 10. The braking effect achieved is graduated in that as the tow commences to slow, the speed at which the propeller blades 72 are rotated is decreased, and thus the amount of turbulence generated by the propeller assembly is also decreased.

The drogue arrangement illustrated in FIGURE 5 of the drawings depends upon both the frictional resistance to the passage of the water developed by the drogues 78 and also upon the turbulence which is created by the drogues as they pass through the water. The drogues are streamed along the tow 10 on all sides thereof so that the turbulence created by the drogues acts over substantially the entire surface area of the tow.

In addition, it should be noted that when the drogues are slowed to a predetermined speed they surface and are further slowed by wave action at the waters surface. Moreover, once the tow ship is under way the braking device can be hauled in to the towing ship and used again when necessity demands, either automatically or manually.

From the foregoing description of the invention. it will be perceived that the present invention provides a novel and highly effective apparatus for decelerating or braking a towed vessel as it moves through the water in a submerged status. The devices are all relatively simple. and have relatively few moving parts so that there is little likelihood of malfunction during their use. All are capable of being actuated and retrieved from the towing vessel and do not depend in any way upon actuating mechanism or electrical circuitry which must be located upon. or extended to, the tow.

Although several embodiments of the invention have een hereinbefore described in detail so as to atford examples of the invention and the manner of its practice sullicient to permit those skilled in the art to benefit from the practice of the invention, it is to be understood that various modifications and innovations may be made in the described structures and procedures without departing from the basic principles which underlie the invention. Insofar, therefore, as changes and modifications to the herein described method and apparatus continue to rely upon and utilize the basic principles which have been disclosed and described. such changes and modifica tions are deemed to be circumscribed by the spirit and scope of the present invention except as the same may be necessarily limited by the appended claims or reasonable equivalents thereof.

I claim:

1. A device for decelerating a submerged vessel towedby a vessel'ohth e s urface by mziirs'ara fiiib'le tow line,

said devic'ec'omprisingz ....ths-

9 t 2. A device as claimed in claim 1 wherein said control means comprises an elongated flexible member secured at one of its ends to said fluid flow resistance means and of a length to extend from said resistance means to the towing vessel.

3. A device as claimed in claim 1 wherein saidhydrodynamic resistance element comprises a plurality of rigid resistance fins extending radially outwardly from said annular body.

4. A device as claimed in claim 1 wherein said hydrodynamic resistance element comprises a plurality of elongated flexible members each attached at one of its ends to said annular body'and each having a cup-shaped, turbulence generating element attached to the other end thereof.

5. A device as defined in claim 1 wherein said hydrodynamic resistance element comprises a propeller mounted on said annular body and extending radially outwardly therefrom whereby said propeller is caused to spin about the axis of said annular body by the flow of water past the propeller.

6. A device as claimed in claim 1 and further characterized to include bearing elements mounted in said annular body and projecting radially inwardly therefrom for contact with said tow line whereby said annular body can move more easily along said tow line.

7. A device as claimed in claim 2 wherein said elongated flexible member is a return cable and said control means is further characterized to include winch means adapted for securement to said towing vessel and con nected to the other end of said return cable for reeling in and paying out said return cable.

8. A device for decelerating a submerged vessel towed by a vessel on the surface by means of a flexible tow line, said device comprising:

' fluid fiow resistance means adapted for movement on said tow line between said submerged vessel and the towing vessel, and including:

an annular body dimensioned to slidably encircle said tow line for sliding movement therealong;

shock absorbing means secured to said annular body and disposed to one side of said annular body along the axis thereof;

a hydrodynamic resistance element extending outwardly from said annular body in a direction which is generally away from the axis of said annular body; and

control means connected to said fluid fiow resistance means and dimensioned to extend at least from said resistance means to said towing vessel whereby the movements of said resistance means on said tow line can be controlled from said towing vessel.

'9. A device for decelerating a submerged vessel towed by a vessel on the surface by means of a flexible tow line, said device comprising:

fluid flow resistance means adapted. for movement on said tow line between said submerged vessel and the towing vessel, and including:

an annular body dimensioned to slidably encircle said tow line for sliding movement therealong;

a hydrodynamic resistance element extending outwardly from said annular body in a direction which is generally away from the axis of said annular body, said hydrodynamic resistance element comprising:

a plurality of rigid resistance fins extending radially outwardly from said annular body;

a fin collar slideably mounted'on said annular body and pivotally connected to one end of each of said resistance fins; and

actuating means for pivoting said resistance fins between said radially outwardly extending position and a position in which said fins extend at angle of less than 45 to the axis of said annular body; and

control means connected to said fluid flow resistance means and dimensioned to extend at least from said resistance means to said towing vessel whereby the movements of said resistance means on said tow line can be controlled from said tow vessel.

10. A device for decelerating a submerged vessel towed by a vessel on the surface by means of a flexible tow line, said device comprising:

fluid flow resistance means adapted for movement on towingvessel, and including:

an annular body dimensioned to slide'nbly encircle said tow line for sliding movement therealong:

a hydrodynamic resistance element extending out wardly from said annular body in a direction which is generally away from the axis of said annular body, said hydrodynamic resistance element comprising:

a plurality of rigidjresistance fins extending radially outwardly from and pivotally mounted on said annular body; and

actuating means for pivoting said resistance fins inwardly toward said annular body from and radially outwardly extending position; and control means connected to said fluid flow resistance means and dimensioned to extend at least. from said resistance means to said towing vessel whereby the movements of said resistance means on said tow line can be controlled from said towing vessel.

11. A device as defined in claim 9 wherein said actuating means includes a retrieving ring slidably surrounding said annular body and spaced therealong from said fin collar; and

braces extending from each of said fins to said retrieving ring and each pivotally connected at one of its ends to one of said fins at a point intermediate the length of the respective fin and pivotally connected at its other end to said retrieving ring.

12. A device as claimed 'in claim 11 and further characterized to include a flexible member interconnecting each of said resistance fins to the next adjacent resistance fins at points adjacent the radially outer ends of the interconnected resistance fins.

13. Apparatus for the marine transport of a liquid cargo comprising:

a towing vessel;

a submersible tow adapted to be towed under the water by said towing vessel;

a flexible tow line interconnecting the vessel and tow;

hydrodvnamicall actuatedadecelerating means mov- .ably mounted on said tow line for movement theli' along between said towing vessel and tow;

shock absorbing means positioned between said decelerating means and said tow for cushioning the impact between said decelerating means and the tow; and

c 9ntrol means extending from said decelerating means to said vessel for controlling the movementof characterized to include automatic tensioning means on saidvessel for automatically maintaining a predetermined connected to said deceler:

with on said tow line.

17. An apparatus as defined in claim 13 wherein said shock absorbing means includes a shock absorbing device positioned around said tow line adjacent its end secured to the tow.

said tow line between said submerged vessel and the l 1 18. Apparatus as defined in clain 13'wherein said decelerating means.-comprises a. sleeve slidably surrounding said tow line; and turbulence generating, fluid flow resistance means connected to said sleeve and extending outwardly there from in a direction away from the axis of said sleeve. 19. Apparatus as defined in claim 18 wherein said turbulence generating. fluid flow resistance means includes at least one hydrostatically actuated movable element attached to said sleeve for movement relative thereto in response to relative movement between the sleeve and the water when the sleeve is in contact with the water.

20. Apparatus as defined in claim 19 wherein said hydrostatically movable element is a propeller rotatably mounted on said sleeve for rotation about the axis thereof. 21. Apparatus as defined in claim 19 wherein said hydrostatically movable element comprises a drogue; and

generating device so that said turbulence generating device and submerged vessel move relatively closer to each other until they contact each other;

dissipating a portion of the energy released upon contact between said submerged vessel and said turbulence generating device in a shock absorber; and

after deceleration of the submerged vessel to the exlaQifiis moved past the turbulence generating device in part a flexible member connecting said drogue to said sleeve.

22. Apparatus as defined in claim 19 wherein there are a plurality of said hydrostatically movable elements and said elements each comprise an elongated resistance fin pivotally mounted on said sleeve and movable in a plane containing the axis of said sleeve.

23. The method of decelerating the forward movement of a submergedvessel connected by a tow line to a towing vessel comprising:

moving on the tow line from a position on the tow line above the water and adjacent the towing vessel to a position in the water and closer to the submerged vessel, a turbulence generating device which offers greater resistance to the fiow of water thereby than does the submerged vessel;

moving the towing vessel away from the turbulence generating device and simultaneously moving the tow line after the towing vessel and past the turbulence by the forward motion of said towing vessel and in part by reeling in said tow line on the towing vessel.

- References Cited by the Examiner UNITED STATES PATENTS 346,689 8/1886 Schoening 114-209 X 2,359,366 10/1944 Katcher et al 114-235 3,039,419 6/1962 Rimar l14-209 3,074,321 1/1963 Draim et al. 1l4--235 X References Cited by the Applicant UNITED STATES PATENTS 637,142 ll/l899 Miller. 2,491,564 12/1949 Ivcrsen.

3,047,259 7/ 1962 Tatnall et 8-].

3,086,490 4/1963 Nichols.

MILTON BUCHLER, Primary Examiner.

T. M. BLIX, Assistant Examiner.

Claims (1)

1. A DEVICE FOR DECELERATING A SUBMERGED VESSEL TOWED BY A VESSEL ON THE SURFACE BY MEANS OF A FLEXIBLE TOW LINE, SAID DEVICE COMPRISING: FLUID FLOW RESISTANCE MEANS ADAPTED FOR MOVEMENT ON SAID TOW LINE BETWEEN SAID SUBMERGED VESSEL AND THE TOWING VESSEL, AND INCLUDING AN ANNULAR BODY DIMENSIONED TO SLIDABLY ENCIRCLE SAID TOW LINE FOR SLIDING MOVEMENT THEREALONG, AND A HYDRODYNAMIC RESISTANCE ELEMENT MOUNTED ON AND MOVABLE RELATIVE TO SAID ANNULAR BODY; AND CONTROL MEANS CONNECTED TO SAID FLUID FLOW RESISTANCE MEANS AND DIMENSIONED TO EXTEND AT LEAST FROM SAID RESISTANCE MEANS TO SAID TOWING VESSEL WHEREBY THE MOVEMENTS OF SAID RESISTANCE MEANS ON SAID TOW LINE CAN BE CONTROLLED FROM SAID TOWING VESSEL.

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