US 3637449 A
A method, or process, is disclosed of preparing flechettes in packs for insertion in a projectile, and a flexible web of flechettes, which is formed during the process, is also disclosed. In preparation of the pack, the flechettes are initially arranged on a rack in an interdigitated array, and a soluble, elastic adhesive is applied, in strip form, to the array. After the strips of adhesive are melted into the array, a flexible web is formed which can be removed from the rack. The web is folded into a mold with an internal cavity in the shape of a pack suitable for insertion into a projectile. A solvent is passed through the mold to dissolve the adhesive, and a matrix material is introduced in liquid form into the mold. The matrix binds the flechettes into a frangible pack which is then installed in a projectile.
Description (OCR text may contain errors)
llnited States Patent Raech, Jr.
 PROCESS FOR PREPARATION OF MISSILES  Inventor: Harry Raech, Jr., San Jose, Calif.
 Assignee: FMC Corporation, San Jose, Calif.
 Filed: Feb. 20, 1969  Appl. No.: 800,971
[451 Jan. 25, 1972 FOREIGN PATENTS OR APPLICATIONS 621,608 2/1927 France ..102/92.4
Primary Examiner-Robert F. Stahl Attorney-F. W. Anderson and C, E. Tripp [5 7] ABSTRACT closed. In preparation of the pack, the flechettes are initially arranged on a rack in an interdigitated array, and a soluble, elastic adhesive is applied, in strip form, to the array. After the strips of adhesive are melted into the array, a flexible web is formed which can be removed from the rack. The web is folded into a mold with an internal cavity in the shape of a pack suitable for insertion into a projectile. A solvent is passed through the mold to dissolve the adhesive, and a matrix material is introduced in liquid form into the mold. The matrix binds the flechettes into a frangible pack which is then installed in a projectile.
12 Claims, 10 Drawing Figures PLACE STRlP OF ADHESIVE ON WEB ASSEMBLE lN PROJEGTlli PAIENIFI] JAN25 ISTZ SHEET 1 I]? 4 v T I 13 1 ASSEMBLE FLECHETTE WEB PLACE STRIP OF ADHESIVE ON WEB MELT ADHESIVE FOLD WEB INTO FINAL SHAPE DISSOLVE ADHESIVE ASSEMBLE IN PROJEGTILE INVENTOR. HARRY RAECH, JR.
BY J01 WV INTRODUCE MATRIX MATERIAL ATTORNEYS BACKGROUND OF THE INVENTION The present invention relates to the installation of flechettes into a projectile such as an artillery shell.
It is known to install flechettes in a projectile, such as an ar' tillery shell, for dispersion upon explosion of the shell. Frequently, the flechettes are woven together with thread. The thread, however, has a tendency to prevent complete dispersion of the flechettes. Sometimes, the flechettes are assembled in the form of a frangible pack which is convenient to handle and install in the projectilepThe pack will readily shatter on explosion of the shell, and the dispersion of the flechettes will not be impaired. In either case, however, it is difficult to handle the small flechettes as they are being prepared in a suitable form for assembly into the shell.
SUMMARY OF THE INVENTION In the present invention, the flechettes are prepared in a convenient manner for easy handling, by forming an elastic flexible web thereof, as they are put into a form for installation in a projectile. 1
In brief, in the preferred form of the invention, the flechettes are first arranged in an interdigitated array, in a single layer, on a rack. Strips of hot melt elastic adhesive are laid on the array, and the adhesive is then melted to bind the flechettes into a flexible web which can be folded into any desired conformation. The web is not, however, installed in the projectile at this time since the adhesive would prevent complete dispersion of the flechettes. Instead, the web is placed in a mold, and a solvent is passed through the mold to dissolve the adhesive. Thereafter, a matrix material is poured into the mold. This material solidifies into a frangible matrix which holds the flechettes in the shape established by the mold. This frangible flechette pack is then installed in the projectile.
It is therefore one object of the present invention to provide a method for assembling flechettes in an easily handled form for preparation of the flechettes for assembly into a projectile.
It is another object of the present invention to provide a method for preparing flechettes for a projectile in which the flechettes are temporarily bound with an adhesive.
It is yet another object of the present invention to temporarily bind flechettes into a convenient form with a soluble adhesive for insertion into a mold where'the adhesive is dissolved and the flechettes are formed into a pack of desired shape.
It is still another object of the present invention to produce a flexible web of flechettes held together by an elastic band for easy and convenient handling of the flechettes in producing a pack of flechettes for a projectile.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart of the steps of the preferred form of the present invention;
FIG. 2 is a view, in perspective, of the rack on whichthe flechettes are arranged, with some flechettes arranged thereon in interdigitated relationship;
FIG. 3 is an enlarged plan view of flechettes as arranged on the rack;
FIG. 4 is a view taken on the line 44 of FIG. 3;
FIG. 5 is a view in perspective of the web of flechettes formed on the rack;
FIG. 6 is a view in perspective of the mold into which the web is folded;
FIG. 7 is view in perspective of the mold, with a manifold head and back, and of apparatus to circulate solvent through the mold;
FIG. 8 is a view in elevation of the application of a matrix material in liquid form to the mold;
FIG. 9 is a view, in perspective, of four frangible packs of flechettes as taken from the mold, spaced apart for clarity; and
FIG. 10 is view, in elevation, with parts broken away, of an artillery shell with an internal cavity to receive the four frangible packs of flechettes of FIG. 9., in side-to-side contact, therein.
DESCRIPTION OF THE PREFERRED EMBODIMENT A method of preparing the flechettes in the form of a pack for insertion into a projectile is shown in FIG. 1. A rack 10, as shown in FIG. 2, has an inclined upper surface 1 l with grooves 9 therein. As shown in FIGS. l to 4, flechettes 12 are placed on the rack in seven rows 13a, 13b, 13c, 13d, 13e, 13f, and l3g. Each flechette 12 is made of steel and has a pointed nose 12a, a body or shank 12b, and a four-vaned tail 12c. The flechettes in each row are staggered so that the tails IZcof every other flechette extend'beyond the tails of the alternate flechettes, and the tails of the alternate flechettes rest against the body of adjacent flechettes in interdigitated relation. It will be noted that there is a groove 9 for each row of flechettes to receive the vaned tails of the flechettes, and that the grooves are wide enough to accommodate the staggered tails.
The flechettes are placed in the rack to all face in the same direction and with the vanes at 45 from the horizontal and vertical, as shown in FIGS. 3 and 4. It will be noted that the staggered flechettes of one row are in interdigitated relation with the flechettes of an adjacent row. For example, the noses of the flechettes in row 13b are contiguous with the tails of the flechettes in row 13a, so that the nose of every other fiechette in row 13b extends between the tails of alternate flechettes in row 13a. The flechettes can be placed in the rack manually or mechanically by the use of feeding devices such as vibrators which cause the flechettes to travel down the grooves in the rack in regular interdigitated rows.
After (or during) the placement of the flechettes on the rack,-the flechettes are cemented together. A soluble adhesive is deposited on the flechettes, either over the entire upper surface of the array, or preferably, along a band A on each row. Cementing can be accomplished by the application of a rubber adhesive, by a plasticized adhesive such as vinyl plastisol, by a'thermosetting adhesive such as epoxy or phenolic-polyvinyl butyral, or by a hot melt adhesive such as a polyamide. In the cases of the thermosetting and hot melt adhesives, the application may be by means of a tape thermally fused in place. In all cases, the glue may be applied in the liquid phase. In all cases also it is desirable that the adhesive have the properties of good adhesion to steel, elongation in the range 50-200 percent, and good solvency in solvents such as water, benzene or acetone. It has been found that the hot melt adhesive offers the best combination of physical properties and processability. This adhesive may, for example, be adhesive 74 DPN-l of ADHESIVE PRODUCTS, Albany, Calif. The adhesive, which is available in chunks, is melted, and then cooled, to form a thin flat sheet. Strips S are cut from the sheet and placed on the flechettes to cover band A, as shown in the rows of FIG. 1. The rack is then placed in an oven 14 (FIG. 1) to meltthe strips of adhesive and bind the flechettes together.
The adhesive solidifies in elastic form to permit flexing of the rows, and the rows are mechanically locked together because of the manner in which alternate flechettes extend between cemented flechettes of an adjacent row. Thus, a flexible web 15 is formed which can be handled, as shown in FIG. 5, and folded.
The web 15 is then folded into the bottom 20 of a mold 21 as shownin FIG. 6. The bottom 20has an internal cavity 20:: which is as long as the web is wide. The web fills the mold cavity 20a and the top 22 of the mold, which has an internal cavity 22a, is then bolted to the bottom of the mold to close the mold. The internal cavity of the closed mold, made up of cavities 20a and 22a, has a cross section in the form of a segment of an annulus. The flechette web 15 is folded to conform to the shape of the internal cavity of the mold.
The adhesive bond is then removed from the web. This may be done by simply submerging the mold in a container of solvent. Preferably, the adhesive is removed by flushing the solvent through the mold under pressure, preferably at an elevated temperature to speed dissolving. To this end, as shown in FIG. 7, a manifold head 23, having a plenum chamber 24, is secured to the mold 21 by bolts 25. Ports 26 connect the chamber 24 with the interior cavity of the mold. A pump 27 has a discharge port 28 connected to the chamber 24 by conduit 29. Conduit 30 extends through a manifold head 23, which is secured to the mold opposite the other manifold head, and is in communication with the internal cavity of the mold. Conduit 30 leads to a tank 32 of benzene, which is heated by heating coil 33. A conduit 34 connects the benzene tank to the inlet port 35 of the pump 27. Thus, hot benzene can be circulated through the mold to dissolve the adhesive on the flechettes. It should be noted that applying the adhesive in strips, instead of over the entire flechette array, leaves small spaces between the flechettes which can easily be penetrated by the benzene for quick and easy access to the adhesive.
After the adhesive is dissolved, the mold is set upright and the manifold heads are removed from the mold. A plate 31 is secured to the bottom of the mold to seal the bottom closed. A matrix material is then poured into the mold, as shown in FIG. 8. The matrix material, which can, for example, be microcrystalline wax, is heated by heater 40, into a liquid form for application to the flechettes in the mold. When the liquid wax cools, the flechettes are held together by the solidified wax, and the pack 41 of flechettes is then removed from the mold. Each pack 41 will be of the shape shown in FIG. 9, in which four packs 41 are shown in spaced relation for clarity. When the four segmental packs 41 are in side to side contact (moved inwardly as far as possible from the position shown in FIG. 9) they will form a cylinder 42 with an opening therethrough.
An artillery shell 43 has a central core 44 and a cavity 45 of annular cross section surrounding the core. Four flechette packs are then installed in the shell to form a cylinder 42. The flechette packs are readily frangible, and the flechettes will be dispersed when the shell explodes.
Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.
What I claim is:
1. The method of preparing a plurality of flechettes for use as missiles comprising the steps of arranging the flechettes in a closely spaced array, applying a removable adhesive to the array of flechettes to hold the flechettes together for handling,
placing the flechettes into a rigid receptacle of desired conformation, and removing said adhesive.
2. The method of preparing a plurality of flechettes for use as missiles comprising the steps of arranging the flechettes in a closely spaced array, applying a soluble adhesive to the array of flechettes to bind the flechettes together for handling, placing the bound array of flechettes into a mold of desired conformation, and dissolving the adhesive.
3. The method of preparing a plurality of flechettes for use as missiles comprising the steps of arranging flechettes in an interdigitated single layer array, applying a strong, soluble, elastic adhesive to said array to bind the flechettes into flexible webbing, placing a plurality of sections of webbing into a mold to produce a pack of flechettes of desired conformation, and introducing a solvent into the mold, to dissolve the adhesive.
4. The method of claim 3 including the additional step of introducing a frangible matrix into the mold to bind the flechettes into a frangible pack.
5. The method of claim 4 including the additional step of placing the frangible pack into a projectile.
6. The method of preparing a plurality of flechettes for use as missiles comprising the steps of arranging the flechettes in closely spaced array, applying an elastic adhesive to said array to bind the flechettes into flexible webbing, placing the webbing into a casing and dissolving the elastic adhesive.
7. The method of c aim 6 including the additional step of in troducing a matrix material into the casing to produce a pack of flechettes.
8. The method of claim 7 including the additional step of inserting the easing into a projectile.
9. The method of claim 6 including the additional step of introducing a frangible matrix material into the casing to produce a pack of flechettes, removing the pack of flechettes from said casing, and inserting the pack of flechettes into the projectile.
10. The method of preparing flechettes having noses and vaned tails for handling comprising the steps of arranging the flechettes in rows, displacing every other flechette in a row to overlap the tail thereof with the nose of alternate flechettes in the adjacent row, and applying adhesive to hold the flechettes together.
1 l. The method of claim 10 in which the adhesive is applied in strips to each row.
12. The method of claim 20 in which the strips of adhesive are melted to flow onto and between the flechettes of each row.
UNETED STATES PATENT OFFER QE'HFKCTE @F QQRECHGN Patent NO. q gq-y a q. Dated Inventor(s) HARRY RAECH, Jr.
It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as'shown below:
Column 4, line 45, change "20 to ll Signed and sealed this Zhth day of October 1972,
EDWARD MFLETCHER,JR ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE or CoRREGMoN Patent N0. :1 517 AAq.
Inventor(s) HARRY RAECH, Jr.
It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
E olumn 4 line 45, change "20 to 11 Signed and sealed this Zhth day of October 1972.
ROBERT GOTTSCHALK EDWARD M.FLE TC HER JR Attesting Officer Commissioner of Patents