US2482106A - Device for controlling the buoyancy of subfloating bodies - Google Patents

Description

Sept. 20, 1949. R. c. DUNCAN ET AL 2,432,106

DEVICE FOR CONTROLLING THE BUOYANCY OF SUBFLOATING BODIES 3 Sheets-Sheet 1 Filed Dec. :50, 1941 INVENTORS R. C. DUNCAN A. H. SELLMAN A ORNEY Sept. 20, 1949.

Filed Dec. '50, 1941 C. DUNCAN ET AL DEVICE FOR CONTROLLING THE BUOYANCY OF SUBFLOATING BODIES 3 Sheefs-Sheet 2 INVENTORS G. DUNCAN H. SELLMAN AT RNEY Sept. 20, 1949. DUNCAN ETAL 2,482,106

.C. DEVICE FOR CONTROLLING THE BUOYANCY OF SUBFLOA'IING BODIES Filed Dec. 30, 1941 3 Sheets-Sheet 3 R. C. DUNCAN A. H. SELLMAN AT RNEY INVENTORS Patented Se t. 20, 1949 DEVICE FOR-CONTROLLIN G THE BUOY- ANCY-LOF SUBFLOATING BODIES Robert C. Duncan and Albert H. Sellman, Washington, D.C.

Application December EO, 1941, Serial No. 424,954

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 '0. G. 757) Claims.

This invention relates to a device for-control= ling the buoyancy of 'a 'subfloating 'body in which the subiloating body is caused 'to "float freely-on the surface of abody'of water withsubstantially all of the body submergedbeneath the surface of the water. More specifically the invention rclates todevices to be attached to or incorporated within the structure of a 'subfioa'ting body, such as a submarine mine in which a plurality of weights are dropped from the mine in succession in accordance with 'the degree of submergence thereof as the mine is launched within the body of water-until'a positive degree of buoyancy is acquired just suiiicient to cause the mine to float on the surface of the water.

In devices heretofore proposed for causing a submarine mine -to float onthe surface ofabody of water it has been the general practice either to construct the mines such that they are positively buoyant before launching the same or to provide the mines with-a substantial weight or anchor adapted to be released after the mine has been launched thereby to cause the mine to float on the surface of the water. 'Such devices are, in general, not adapted to impart a positive degree of buoyancy to the mine just 'sufiicient to cause the mine to rise within the body of water but, on the-contrary, theloss in Weight of the mine, when such devices-are employedis usually sufficient to cause themineto'fioat'on'the surface of the water with a considerable portion of the mine extending above the surface of the water and the mine, therefore, is readily detectable at a distance sufficient to enable an approaching vessel to avoid the same.

The present inventionprovides an arrangement in which a plurality of relatively small weights are released from the mine in succession in accordance with the .depth of submergence thereof within the body of water whereby the weight of the mine is progressively adjusted to a value slightly less than the weight of the water displaced. As the weights are released, the rate of descent of the mine within the water is progressively reduced until the downward movement of the mine is arrested and the .mine starts to rise within-the water. by reason oi'the small positive degree of buoyancy thus acquired. An ar rangement is thus provided in whichthe' mine is caused to ficat on the surface of the water in a substantially submerged condition with only a small fractional portion of the mine projecting above the surface of the watenand thus the mine is practically indistinguishable from the surrounding water and the possibility of detection of the mine by anobse'rver is greatly reduced.

Qne of theobjects of the present invention is to' provide new and improved means for causing the specific gravity of a subfioating body "to 'be 2 adiustedto a value slightly less than the specific gravity of the surrounding water.

Another of the objects isthe'provision of means for reducing the specific gravity of a subfloating body'progressively in steps in accordance with=the degree ofsubmergence'of the body within a body of water as 'thebody is launched.

Another object is the provision of means for reducing theweight of a subfloating body by'iore-' determined decrements of decreasing amounts until the specific gravity thereof is slightly less than the specific gravity of the surrounding Water.

Anotherobject is the provision of means-set table at will for controllingthe rate of "change in the specific'gravity of a submarine mine in re sponse *to predetermined variations in the depth of submergence thereof within a body of Water beforethe-mine starts to rise within the water in response to a small positive degree of buoyancy thus acquired.

Still another object is the provision of new and improved depth controlling mechanism for a subfloating body which will be simple in construction, economical to manufacture, and which possesses all of the qualities of ruggedness and reliability in service.

Further other objects, "improvements and advantages will be apparent from the following-description taken in connection with the accom panying drawings of which:

Fig; 1 is a View in elevation of the buoyancy control device operatively connected to a submarinemine; V

Fig. 2 is an'enlarged side elevation view of the buoyancy-control device of Fig. 1;

Fig. 3 is 'an'enlarged detail section view'takeii along the line 3-3 of Fig. 2;

4 is a View in front elevation of the device of Fig. 2.

Fig. 5 is a sectional view taken along the line 5-5 of 'Fig. 4, and

Figs. 6 and 7 show alternative forms of the weights suitable for use with'the present invention.

Referring now to the drawings on which like numerals of reference are employed to designate like parts throughout the several views, and more particularly to Fig. 1 thereof on which 'is shown a buoyancy control device comprising a mecha-' nism for dropping a plurality of weights" in suecession in accordance with the extent of operation ofan expansible bellows, the device being in dicated generally by the numeral 1 l. The device comprises an inverted U-sha'ped frame member l2 havingbent-over portions 13 and 1% extending downward therefrom and-secured 'toa submarine mine l5 as by the bolt [6 passing through the brackets l1 secured to the mine in mannenas by brazing or Welding the parts toany suitable" 'gether. The mine is provided preferably with a cover I8 secured thereto as by the bolts 19 in watertight relation as by the gasket 20 disposed between the cover and the casing of the mine. The mine is also provided preferably with a plurality of firing horns 2| adapted to cause the mine to explode upon coming into contact with an object such, for example, as a vessel although it will be understood that, if desired, other types of mines may be employed with the device of the present invention such, for example, as types known as influence controlled mines in which the mine is not required to be brought into physical contact with a vessel in order to detonate the mine.

Secured to the portion M as by the nut 23 is an expansible bellows 24 adapted to actuate a pair of arms 25 pivoted at 26 against the pull of theretractile spring 21. An adjusting screw 28 having a nut 29 thereon is preferably disposed Within a suitable aperture within the portion l3 of the U-shaped frame thereby to control the movement of the bellows 24 and arms 25 in accordance with the increase in pressure of the surrounding water as the device sinks within the water. The expansible bellows is connected to the arms 25 as by the pin 3|] disposed within the slot 3| therein. The arms 25 are also slotted as at 32, a suitable bearing pin 33 disposed within the slot 32 connecting a notched bar 34 to the arms. Secured to the portion |3 of the frame in any suitable manner as by the rivets 35 is a bearing 36 adapted slideably to support one end of the notched bar 34 and having a stop pin 31 provided with cotter pins 38 whereby the movement of the bar within the bearing is limited by the ends of the aperture 39 engaging the stop pin. The other end of the notched bar passes through the bearing plate 4| secured to the portion M as by the rivets 42, a suitable aperture 43 being provided within the portion M to permit movement of the bar therein.

The bar 34 is provided with a plurality of stops formed by the notched portions 44 thereof adapted to engage the arms or latches 45 each porvided with a hub 46 rotatably mounted preferably on a sleeve bearing disposed on the rod 48 secured to the frame portions l3 and I4 as by the nuts 50 whereby the arms are maintained in spaced relation with respect to each other and with respect to the notched portions 44 of the slideable bar. Arranged between each pair of sleeves 41 on the rod 48 is a plate or partition 49 having an aperture in the lower portion thereof within which is disposed the rod 5| secured to the portions |3 and I4 as by the nuts 52'. Disposed on the rod 5| are a plurality of sleeves 53 whereby the plates 49 are maintained in a predetermined position in spaced relation with respect to each other and the arms 45.

Releasably supported by the rod 5| and sleeves 53 are a plurality of weights 54 having a portion 55 thereof somewhat heavier than the portion 56 whereby the weights are caused to rotate about the rod 5| by the force of gravity acting thereon as the arms 45 are successively'released by the movement of the slideable bar 34. The weights A to J indicated generally by the numeral 54 are each provided with a shoulder or stop 51 adapted to engage the rod 58 and prevent movement of the weight in the reverse direction. The rod 58 passes through the frame portions l3 and I4 and is provided with cotter pins 59 at each end thereof for maintaining the rod in engagement with the hooks or brackets 6| secured to the casing of the mine in any suitable manner. The arms 45 are each provided with a curved end 62 adapted to engage a complementary recessed portion 63 of the weights 54. When the bar 34 is moved sufficiently by the hydrostat 24 a particular one of the stop members thereof is moved from the path of travel of the upper end of the pivoted arms 45 thereby releasing the arms for rotation about the sleeve bearings 41 and permitting the weights to rotate about the sleeves 53 disposed on the rod 5| and. to be dropped as the arms rotate clockwise in" the direction indicated in dashed outline on Fig. 5.

The arrangement of notches in the slideable bar 34 is such that the weights A to J are dropped in successive order in accordance with the degree of movement of the bar, and thus an arrangement is provided in which the weight of a submerged floating body is progressively decreased as the body sinks within a body of water in response to the launching thereof until a sufiicient reduction in the weight of the body has been effected to cause the direction of travel thereof to be reversed by reason of the small degree of positive buoyancy thus acquired. By adjusting the screw 28 in a direction to increase the tension of the spring 21, a greater degree of hydrostatic pressure is required to actuate the expansible bellows 24 and thus a greater depth of submergence is required to drop the weights 54. Conversely, a decrease in the tension of the spring 21 permits the Weights to be dropped successively at relatively lesser depths of submergence within the water.

The weights A to J may, if desired, be composed of different materials such, for example as iron, brass, aluminum and the like whereby the mass of each of the weights varies in accordance with the material of which the weight is composed. Also the mass of the weights may be varied by providing suitable apertures or recessed portions therein such, for example, as illustrated on Figs. 6 and '7. 0n Fig. 6 the weight 54 is provided with an aperture 64 generally rectangular in shape and of a'size sufficient to reduce the mass of the weight to apredetermineddesired value. In a similarrnanner the Weight 54 may be provided with an aperture such as the circular aperture 65 illustrated, to effect a desired reduction in the mass thereof. 'It will, of course, be understood that the arrangement of weights shown on Figs. 6 and '7 represents but a few of the various arrangements that may be applied to the weights to effect variations in the mass thereof and various other shapes and arrangements may be employed for this purpose. Also, if desired, the weights may be composed of a combination of materials such, for example, as brass and lead, iron and brass or the like arranged within suitable apertures or recesses within the weights provided for this purpose, or attached thereto as desired, thereby to cause the weights to impart a predetermined degree of positive buoyancy to the subfloating body as the Weights are released therefrom.

Assume, by way of example, that the mine l5 at the time of launching is ten pounds heavier than the weight of the water displaced thereby causing the mine to sink within the water. As the mine sinks to a predetermined depth such, for example, as ten feet below the surface of the water the slideable bar 34 is moved sufliciently by the expansible bellows 24 to cause the first weight A to be dropped. This weight may be composed of such a material as to decrease the weight of the mine by four pounds as the weightis released, the mine now being six pounds negativel'y buoyant.

Let it be assumed further that a second weight B is dropped as the mine reaches a depth of twenty feet within the water, this weight being of such material and shape that the weight of the mine in the water is decreased by three pounds, the mine now having a negative buoyancy of three pounds. As the mine passes a level corresponding toa depthoi submergence of twenty-six feet, for example, a third weight C is dropped of sufficient mass to decrease the buoyancy of the mine by anadditional two pounds, the mine now being but one pound negatively buoyant. It will, of course, be understood that as the negative buoyancy of the mine is progressively decreased by the release of the different weights in succession the rate of' descent thereof through the water is correspondingly reduced.

As the mine reaches a depth of submergence of thirty-one feet, for example, a fourth weight D isdropped thereby reducing the buoyancy of the mine two pounds and thus changing the buoyancy fromone pound negative to one pound positive buoyancy. It may also be assumed that the weight dropping mechanism is adjusted to drop an additional weight E when the mine has reached a depth of submergence of thirty-six feet beneath-the surface of the water and that as the fourth weight D is released at a depth of submergence-of thirty-one feet, the positive buoyancy of the mine thus acquired is sufficient to overcome the force of gravity acting thereon therebybringing the mine to rest and starting the upwardmovemen-t of the mine within the water before the mine has descended to a depth of thirty-six feet whereby the fifth Weight E and the succeeding weights F and J therefore are not dropped.

The mine rises slowly within the water and comes to rest in a nearly completely submerged position beneath the surface of the water, being maintained in the submerged position by a force of buoyancy equal to the weight of the water displaced when the mine has assumed a position therein such that one pound of water corresponds to-that portion of the mine protruding above the surface of the water.

It-will be apparent from the foregoing that the mine will assume a state of equilibrium at the surface of the water such that practically all of the mine is submerged beneath the water and the mine, therefore, is practically indistinguishable from the surrounding water. During the foregoing cycle of operations a subfloating body having a negative degree of buoyancy at the time of launching Within a body of water has been successively adjusted at intervals of time during the travel of the mine downward within the water suchthat the specific gravity thereof has been reduced to a value slightl less than the specific gravity of the surrounding water thereby causing the-subfioating body to rise within the water and assume a floating position therein such that the subfloating body is almost entirely submerged within the water and the possibility of detection otthe' subfloating body by an observer is greatly reduced. When applied'to a submarine mine, the present invention provides new and improved means: for adjusting the specific gravity of the mine toa value sufficiently close to the specific gravity of the surrounding water to cause the mine to maintain a floating position at the surface of: the water without a substantial portion of the mine extending above the surfacev of the: to enable an observer to detect.

water sufficiently the same in-timeto alter the course of: thevessel sufiicientiy to avoid striking the mine or otherwise explode the mine inresponse tothe approach of the vessel;

Whereas inthe foregoing example it hasbeen dropped to change the buoyancy of the mine from a negative to a small weights sired, to

may be of greater or lesser mass, as dethermore, while in the illustrative embodiment of the-invention the weight dropping mechanism is shown as comprising a structure adapted to reiease and drop selectively ten weights A to'J,

it Will-be understood that this has been done for illustrative purposes only and that, if desired, the W dropping mechanism may be adapted to' release or drop a greater or lesser number of weights; also the stops on the slideable bar-may be arranged to drop two or more weights simultaneously, or larger weights maybe employed in accordance with the degree of buoyancy control desired.

While there'is shown and described herein a certain preferred embodiment of the invention satisfactory results, many other and.

which gives varied forms and uses will present themselves to those versed in the art without departing from. the invention, and the invention, therefore, is not limited" either in structure as indicated by the terms andscope of the. appended claims.

The invention, herein described and claimed may-be. manufactured and used by or for the Government of the United States of America for governmental purposes without the payment, of any royalties thereon or therefor.

What is claimed as new and desired to be securedby Letters Patent of the United, States is:.

1; In a device for controlling. thebuoyancy of a subfioating body disposedwithina body of. water, a weight dropping mechanism. comprising a hydrostatic. device, a slideable bar adapted to be.

actuated selectively by. said, hydrostatic deviceand having a plurality of stop devices therein, a

plurality of rotatable arms respectively disposed:

adjacent each of said stop devices and adapted' to be selectively released thereby, and a plurality ofreleasably supported weights associated respectiy'ely with each of said rotatable arms andadapted to be released in succession by said arms as the arms are selectivelyreleased by saidstop devices.

2. Ina device for controlling the buoyancy of asubfloat-ing body disposed within a body of was ter, a weight dropping mechanism comprising a hydrostatic; device, a slideable bar adapted to be actuated selectively by said hydrostatic device and having a plurality of stop devices thereon, a

plurality of rotatable arms respectively associated withzeach of said stop devices and adapted to be rotated: in successive order as the stop devices are moved from the path of travel of said arms, a plurality of releasably supported weights associated respectively with each of said rotatable arms and adapted to-rotate the arms, and means forreleasing the weights in succession as thearms;

positive value andthat theadjust the buoyancy of the mine and the specific gravity thereof to a desired-value. Furor in use except.

are rotated in response to movement of said slideable bar.

3. In a device of the character disclosed for adjusting the specific gravity of a subfioating body, a framework having a hydrostatic device secured thereto in communication with the water within which the device is submerged, a notched bar slideably supported by said framework, means including an arm rotatably supported by said framework for causing said bar to be moved selectively in accordance with the degree of operation of said hydrostatic device, a plurality of weights releasably supported by said framework, and means including a plurality of rotatable arms respectively associated with each of said'weights and having one end thereof adapted to be released for rotation selectively by said notched bar in accordance with the degree of movement thereof.

4. In a device of the character disclosed for adjusting the specific gravity of a subfloating body, a framework having a hydrostatic device secured thereto in communication with the water within which the device is submerged, a notched bar slideably supported by said framework, means including an arm rotatably supported by said framework for causing said bar to be moved selectively in accordance with the degree of operation of said hydrostatic device, a plurality of weights releasably supported by said framework,

means including a plurality of rotatable arms respectively associated with each of said weights and having one end thereof adapted to be released for rotation selectively by said notched bar in accordance with the degree of movement thereof, and means settable at will for adjusting said hydrostatic device in accordance with the degree of hydrostatic pressure required to release said weights.

5. In a device of the character disclosed for adjusting the buoyancy of a subfloating body, the combination of a frame, a horizontal shaft supported by said frame, a plurality of detachable weights having complementary recessed portions therein adapted to receive said shaft and be disengaged therefrom when the weights have rotated a predetermined angular distance about the shaft, means for preventing movement of the weights about said shaft beyond a predetermined setting thereof, a plurality of rotatable arms respectively associated with each of said weights and adapted to maintain the weights in said predetermined setting, a slideable bar having a plurality of stops thereon adapted to prevent the rotation of said arms when the bar is in an initial position, and means controlled by the pressure of the water within which the device is submerged for actuating said slideable bar variably to release the arms and the associated weights in accordance with the depth of submergence of the device within the body of water,

6. In a device of the character disclosed for adjusting the specific gravity of a subfioating body to a value slightly less than the specific gravity of the surrounding water, the combination of a hydrostat in communication with the water, means including a retractile spring for controlling the degree of movement of said hydrostat as the depth of submergence thereof within the water is varied, a plurality of releasably supported weights, means including a latch device controlled by said hydrostat for releasing a sufficient number of said Weights in succession as the pressure of the water on the hydrostat is increased to adjust the specific gravity of the body to a value slightly less than that of the surrounding water, and mean-s settable at will for controlling the degree of vertical travel of the device during the adjustment of the specific gravity thereof.

7. In a weight dropping device of the character disclosed adapted to adjust the specific gravity of a subfioating body to a predetermined value slightly less than the specific gravity of the surrounding water, a plurality of releasably supported weights having a recessed portion therein, a shaft disposed within said recessed portion for supporting said weights in predetermined spaced relation, a slideable bar settable to an initial position and a plurality of different moved positions and having a plurality of stop members thereon, a plurality of rotatable latches adapted to retain said weights in said predetermined spaced relation, said rotatable latches being normally engaged by said stop members when the slideable bar is in said initial position, a hydrostatic device in communication with the water within which the device is submerged, and means operatively connected to said hydrostatic device for causing said slideable bar to be actuated selectively to said different moved positions in accordance with the depth of submergence of the device within the water thereby to release said weights selectively in succession as said slideable bar moves into each of said moved positions.

8. In a device of the character disclosed for adjusting the specific gravity of a subfioating body, the combination of a frame, a horizontal shaft supported by said frame, a plurality of detachable weights having complementary recessed portions therein adapted to receive said shaft and be disengaged therefrom when the weights have rotated a predetermined angular distance about the shaft, a plurality of rotatable latches respectively associated with each of said weights and adapted to maintain the weights in a predetermined initial position on said shaft, a slideable bar having a plurality of stop members thereon less in number than the number of said latches adapted to prevent the release of th latches when the bar is in an initial position, and means controlled by the pressure of the water within which the device is submerged for actuating said slideable bar sufficiently to release Said latches and the associated weights in predetermined sequential order as the stops are moved in succession from the path of travel of the latches by said pressure controlled means.

9. In a device for adjusting the specific gravity of a subfloating body to a value slightly less than the specific gravity of the surrounding water, the combination of a plurality of detachable weights having recessed portions therein, a shaft disposed within said recessed portions for releasably supporting said weights in an initial position, means for preventing substantial movement of the weights along said shaft, a plurality of rotatable alined arms operatively connected to said weights for releasing the weights in a predetermined order of sequence as the arms are released, a slideable bar having a plurality of stop members thereon adapted to prevent the release of said arms when the bar is in an initial position, means for maintaining each of said rotatable arms in predetermined axial relation to said stop members, and means controlled by the pressure of the water within which the device is submerged for causing said stop members to be moved from the path of travel of said latches and thereby release the latches and'weights in predetermined successive order as the slideable bar is progressively 9 actuated by said pressure responsive means sufficiently to move said stop members from the path of travel of said latches.

10. In a weight dropping mechanism adapted to adjust the buoyancy of a subfloating body, the combination of a frame having a horizontal shaft supported thereby, a plurality of detachable weights having complementary recessed portions therein adapted to receive said shaft and be disengaged therefrom when the weights have rotated a predetermined angular distance about the shaft, a stop member secured to said frame adapted to engage complementary projecting portions of said weights and arrest-the weights in a predetermined position whereby the center of gravity of each of the weights is disposed at sumcient distance from the vertical plane of the axis of said shaft to urge the weights rotatably away from said stop member, a plurality of latches respectively associated with said weights and adapted to prevent movement of the weights away from said stop member until the latches are released, a hydrostatic device secured to said frame, and means including a slideable bar having a plurality of notches therein controlled by said hydrostatic device in accordance with the depth of submergence of the device within the water for releasing said rotatable arms and weights in predeterminedsequential order in accordance with the degree of progressive movement of said slideable bar.

11. In a device of the character disclosed for controlling the buoyancy of a subfioating body disposed within a body of water, a weight dropping mechanism comprising a hydrostatic device, a plurality of detachable weights of different masses, means for releasably supporting said weights, a slideable bar controlled by said hydrostatic device having a plurality of stop members thereon adapted to release and drop a certain number of said weights selectively in predetermined sequential order in accordance with the initial depth of submergence of the body within the water as the body is launched therein sufiicient to impart a positive degree of buoyancy thereto, and means for preventing the release of the remainder of said weights durin the movement of the body upward within the water after said certain number of weights have been dropped.

12. In a device for controlling the buoyancy of a body disposed within a fluid, a weight dropping mechanism comprising a control means, a slideable bar adapted to be moved to different positions in succession by said control means and having a plurality of stop devices therein, a plurality of movable elements adapted to be released by said stop devices selectively in accordance with the degree of movement of said bar, and a plurality of releasably supported weights associated respectively with each of said movable elements and adapted to be released thereby.

13. A device of the character disclosed for adjusting the buoyancy of a subfioating body from an initial negative value of buoyancy to a predetermined positive value of buoyancy during a single continuous downward movement of the body within the water, comprising, a supporting member secured to the body, a plurality of weights pivotally and releasably mounted on said member with the center of gravity of each of the weights arranged above and to one side of the pivot axis thereof whereby the weights upon release pivot on the member and fall free of the body, a plurality of normally locked latch devices respectively associated with said weights for releasably securing the weights to the member, a hydrostatic device operable progressively as the body sinks within the water, and a plurality of unlocking means individual to said latch devices and constructed and arranged to be moved progressively by said hydrostatic device to positions for releasing the latches individual thereto, said latch devices and said unlocking means being arranged in predetermined spaced relation whereby said release positions correspond to different predetermined depths of submersion of the body within the water, thereby to release a number of weights in predetermined successive order sufiicient to adjust the buoyance of the body to said positive value.

14. In a device of the character disclosed for adjusting the buoyancy of a subfloating body, the combination of a plurality of weights detachably supported on said device for adjusting the buoyancy of the body upon successive release of said weights therefrom, a plurality of latch members each individual to one of said weights and adapted to releasably attach the weights to the device, slideable retaining means for said latch members and movable progressively to different release positions individual to the latch members and efiective to release a predetermined number of said latch members in successive order in accordance with the number of release positions through which the slideable means has been moved, and hydrostatic means on said device and including a movable element operatively connected to said slideable means for moving the slideable means progressively to said diflerent positions during a single continuous descent of the device within the water.

15. In a device of the character disclosed for adjusting the buoyancy of a subfloating body having an initial negative buoyancy to a slightly positive buoyancy, the combination of a supporting member secured to said device, a plurality of weights rotatably mounted on said supporting member and releasable therefrom by rotation thereon in response to the influence of gravity, a plurality of latch members individual to said weights for preventing rotation of the weights on the supporting member, a hydrostatic device including an element movable progressively in accordance with the increase in the depth of submersion of the hydrostatic device, and means operatively connecting said element to said latch members and constructed and arranged to unlatch said members in succession as the body descends within the water to predetermined successive depths of submersion thereinuntil a sufficient number of weights has been released to cause said slightly positive buoyancy of the body.

ROBERT C. DUNCAN. ALBERT H. SELLMYAN.

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

UNITED STATES PATENTS Number Name Date 303,843 Hammond Aug. 19, 1884 952,452 Leon n Mar. 22, 1910 1,035,021 Laubeuf Aug. 6, 1912 1,295,067 Riley et al. I Feb. 18, 1919 V FOREIGN PATENTS Number Country Date 256,008 Germany Jan. 28, 1913

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