US 3087427 A
Description (OCR text may contain errors)
A ril 30, 1963 KARL-JOHN 'r. THORILDSSON POWER DRIVEN, MINE CLEARING EXPLOSIVE SNAKE Filed Oct. 18, 1960 INVENTOR. KARL-JOHN THOR/L0 THOR/LDSSDN A T'T'ORNE rs States The present invention relates to power driven explosive snakes as are used for clearing a safe path through a mine field.
Such snakes generally consist of a hose or tube made of a pliable material and filled with an explosive material, such as TNT. The snake is usually about 100 to 200 meters long. The driving power may be and is usually supplied by a rocket, and the snake is fired with a trajectory such that it will land across a mine field. The shock waves generated by a detonation of the snake will set oif all the land mines within the vicinity of the snake, thus clearing a safe path for the advance of troops.
It is common practice to stabilize the trajectory of the snake by attaching a brake parachute to the snake, for instance by fastening the canopy of the parachute to the rear end of the snake by means of guy ropes secured to the canopy in circumferential spacing.
The braking action of the parachute is intended to assure that the snake lands fully stretched out in a perpendicular plane to utilize fully the effective length of the snake. As is ew'dent, the braking action of the parachute is a function of the wind pressure acting upon the parachute during the flight of the snake, and the wind pressure, in turn, is a function of the flight velocity of the snake. As is also evident, the flight velocity of the snake declines during the last part of the trajectory and the thus correspondingly declining wind pressure may be balanced or even overcome by side winds. In consequence, the rear portion of the snake may drift laterally in reference to the true forward course of the snake still maintained by the forward part of the snake in a perpendicular plane. Accordingly, the effective length of the snake when it lands is shortened, so that the depth of the mine field may not be fully spanned and a safe passage is not clearly defined. As a result, several snakes may have to be used to clear a passageway which is often difiicult under conditions of warfare.
It is the broad object of the invention to provide a novel and improved trajectory stabilizing device for an explosive mine-clearing snake of the kind above referred to which assures that the snake will land substantially fully stretched out, thus clearing a path of a length corresponding to the full useful length of the snake through a mine field.
A more specific object of the present invention is to provide a novel and improved trajectory stabilizing device for an explosive mine-clearing snake which impedes lateral drifting of the rear portion. of the snake during the terminal part of the flight of the snake, thus holding the snake in a substantially fully stretched out position until it lands.
Another more specific object of the invention is to provide a novel and improved trajectory stabilizing device for an explosive mine-clearing snake which compensates for the declining stabilizing power of the parachute during the terminal part of the flight by causing a change in the configuration of the parachute, such that the braking power of the parachute is reduced, for instance, by causing a. partial collapse of the parachute.
Other and further objects, features and advantages of the invention will be pointed out hereinafter and set forth aten in the appended claims forming a part of the application.
In the accompanying drawing, several prefer-red embodiments of the invention are shown by way of illustration, and not byway of limitation.
in the drawing:
FIG. 1 is a diagrammatic view of an installation for firing a mine-clearing snake, the snake being shown in the condition ready for firing;
FIG. 2 is a graph showing the variations of the driving force and the braking force acting upon the snake during its trajectory;
FIG. 3 is a diagrammatic view of the stabilizing device according to the invention;
FIG. 4 is a similar view of a modification of the stabilizing device;
FIG. 5 is a similar view of another modification of the stabilizing device; and
FIG. 6 is a similar view of still another modification of the stabilizing device.
Referring first to FIGS. 1 and 2 in detail, FIG. 1 shows a coiled snake consisting of a hose or tube 1 made of any suitable pliable material, such as a plastic, and filled with an explosive material. A folded or packed parachute 4, including the stabilizing device according to the invention, is attached to the rear end of the snake, that is, to the end which is rearward during the flight of the snake. The parachute assembly will be more fully described hereinafter. The snake is fired by means of a launching device '12, in which is inserted a rocket 3; attached to the forward end of the snake and supplying the driving force. The firing of the snake and the arrangement of the driving rocket do not constitute part of the invention and should be visualized as being conventional. The parachute opens by being pulled out of its bag when the rear part of the snake has obtained a certain predetermined velocity. The manner in which the parachute opens should also be visualized as being conventional.
Turning now to FIG. 2, the graph, according to this figure, shows the driving force F as a function of the time t. The curve F shows the driving force and, as is apparent, the driving force first increases rapidly and then remains substantiallyconstant until the rocket motor burns out and the driving force ceases. The braking power exerted by the parachute is shown by the curve F 7 As is seen, the opening of the parachute causes a sharp surge of the braking power. This surge is of very short duration and, after it subsides, the braking power remains substantially constant and declines gradually during the terminal part of the flight until it finally reaches a zero value. It is desirable that the braking power should cease as abruptly as possible when it has declined to the value F and it is the purpose of the present invention to obtain such abrupt termination of the braking force to avoid, or at least minimize, the aforedescribed tendency of lateral drifting of the rear part of the snake close to the end of the trajectory.
Referring now to FIG. 3, the stabilizing device according to the invention comprises a parachute, the canopy 4 of which is joined by circumferentially spaced shrouds or guy ropes 6 to a swivel joint 5 which, in turn, is attached by means of connector 2 to the snake 1 proper. 'Swivel joint 5 permits spinning of the parachute during the flight without twisting the snake. According to the invention, an elastically stretchable means 7 extends between swivel joint 5 and the center part of canopy 4. The elastically stretchable means is shown as a coiled tension spring, but it may also be an elastic rope, such as a rope consisting of a plurality of twisted rubber strands encased in a sheath.
Spring 7 is relaxed prior to the opening of the parachuteand in that state, it-tends to hold the canopy in 'a more or less collapsed shape and in any event in a shape such thatthe canopy cannot assume the fully opened shape in 'which it exerts-its-maxiinumbraking-power.
When the parachute opens during flight, spring is tensioned and is soshown in FIG. 3. It is'held in its tensioned state as longas the braking powerFj; is still appreciably above the value F As the braking power approaches the value F or in other words as the wind pressure acting upon'the parachute declines below a predetermined value, the'tensional force'stored in the spring begins to overcome the counteraction of the wind pressure and, as a result, spring 7 begins to contract towards its relaxed state, thereby effecting an at least partial collapse of the canopy, thus spilling the air out of the canopy and terminating abruptly more or less completely the brakingpower of the parachute and, at the same time, making the parachute less susceptible to the action of side winds.
According to FIG. 4,- the elastically strechable means is shown in the form of an elastic ribbon, band or rope '8, attachedto the canopy 4 along the circumference thereof. The function of rope 8 is the same in principle as that of spring 7. The rope, when in its relaxed state, more or less holds the canopy in a configuration in which the same cannot exert its maximum braking power. The
rope is expanded when and while the parachute has opened and is exposed to a wind pressure above the value F FIG. 4 shows the rope in its expanded or tensioned state. As soon as-the brakingpower declines below the value F the rope contracts thus effecting a more or less complete collapse of the canopy.
According to FIG. 5, the same result is obtained by replacing one of the guy ropes 6 by anelastic'ally stretchable spring or rope 9. The function of the rope or spring "9'- is apparent from the previous description and is, in effect, the same as that of spring 7 or rope 8.
Finally, according to FIG. 6, the same effect -is obtained byattaching elastically stretchable ropes or springs .10 crosswise to the circumference of the canopy. Both ropes or springs 10 remain stretched as long as the braking force is above the value F and begin tocontract 'when thatvalue is approached, thus collapsing the canopy more or less and spilling the wind out'of the-parachute.
While the invention has been describedin detail with respect to certain-now preferred examples and embodiments of the invention, it will be understood by those skilled in the art, after understanding the invention, that various' changes and modifications may be made" without departing from the spirit and scope of the irrvention, and it is intended, therefore, to cover all'suchchan ges and modifications in the appended claims.
What'isclaimed as new and desired to be secured'by Letters Patent is:
1. A power driven explosivesnake for clearing a path acrossa mine fieldb'y firing the snake across the mine held in free-flight and ma substantially stretched out condition, said snake comprising a rollable and 'pliable tube-filledwith an explosive materialand a s tabilizing means for stabilizing the trajectory of the snake, said stabilizing means being attached to the rearward end of the tube and including a parachute having a canopy arranged to be opened by the windpressure acting upon the canopy due to the flight velocity of the snake, said parachute exerting astabilizing braking force for holding the snake on its trajectory, the strength of said braking force being a function of the effective area of the canopy and said'effective area being a function of the wind pressure, and yieldable compensating means attached to the parachute to hold the canopy thereof in a partially collapsed shape in a relaxed state of the compensating means and to permit full opening of the canopy in a tensioned state of the compensating means, said compensating means being tensioned by the opening of the parachute and maintained tensioned by a wind pressure above a predetermined value, a decline of the wind pressure below said value releasing the compensating means for return into the relaxed state thereof thereby efifecting an at least partial collapse of the canopy causing an abrupt decrease of the braking power of the parachute below said predetermined wind pressure.
2. A snake according to claim 1 wherein shroud lines attached to the rim of the canopy secure the parachute to said rearward end of the snake, and wherein said yieldable compensating means comprise elastically stretchable means extendingbetween said rearward end and the center part of the canopy, said elastically stretchable means being tensioned by the opening of the canopy whereby the tensioned elastically stretchable means exert a force pulling said center part of the canopy toward said rearward end of the snake to effect the at least partial collapse of the canopy.
3. A snake according to claim 2 wherein said elastically stretchable means comprise a coiled spring.
4. A snake according to claim 1 wherein shroud lines attached to the rim of the canopy secure the parachute to said rearward end of the snake, and wherein said yieldable means comprise elastically stretchable means attached to the canopy along the rim thereof, said elastically stretchable means when relaxed holding said canopy in an at least partially collapsed configuration and being stretched by an opening of the canopy in response to a wind pressure above said predetermined value, the tensional force stored in the elastically stretchable means constituting a force tending to elfect the partial collapse of the parachute when the wind pressure acting-upon the parachute declines below said predetermined value.
5. A snake according to claim 1 wherein'shroud lines attached to the rim of the canopy secure the parachute to said rearward end of the snake, and wherein said yieldable means comprise elastically stretchable means constituting one of said shroud lines, said elastically stretchable means when relaxedholding the canopy in an at least partially collapsed configuration and being stretched by an opening of the'canopy in response to a wind pressure above said predetermined value, the tensional force stored in the elastically stretchable means effecting the partial collapse of the parachute when the wind pressure declines below said predetermined value.
6. A snake according to claim! 1 wherein shroud lines attached't'o the rim of the canopy secure the parachute to said rearward end of the snake, and wherein said yieldable means cornprise elastically stretchable means extending across the canopy attached to the rim thereof, said elastically stretchable means when relaxed holding the canopy inan at least partially collapsed configuration and being stretched .by an opening of the canopy in response to a wind pressure above said predetermined value, the tensional force stored in the elastically stretchable means effeoting'the partial collapse of the parachute when the wind pressure acting upon the parachute declines below said predetermined value.
References Cited in the file of this patent UNITED STATES PATENTS 1,340,259 Taylor May 18, 1920 1,519,857 Lucas Dec. '16, 1924 1,978,641 Martin ,Oct. 30, 1934 *2,77l1,841 De Fino Nov. 27, 1956