US2983224A

US2983224A - Plastics sabot

Info

Publication number: US2983224A
Application number: US712283A
Authority: US
Inventors: Stanley P Prosen; Fredrick R Barnet
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-01-30
Filing date: 1958-01-30
Publication date: 1961-05-09
Anticipated expiration: 1978-05-09

Description

y 9, 1961 s. P. PROSEN ET AL 2,983,224

PLASTICS SABOT Filed Jan. 30, 1958 2 Sheets-Sheet 1 FIG.1.

INVENTORS STANLEY P. PROSEN BY FREDRICK RBARNET ATTYS.

May 9, 1961 s. P. PROSEN ET AL 2,983,224

PLASTICS SABOT Filed Jan. so, 1958 a 2 Sheets-Sheet 2 34 27 I FICA.

INVENTORS STANLEY P. PROSEN FRE RICK R. BARNET BY ATTYS.

Unite PLASTICS SABOT Stanley P. Prosen, Lanham, and Fredrick R. Barnet, Kensington, Md., assignors to the United States of America as represented by the Secretary of the Navy Filed Jan. so, 1958, set. No. 712,283

11 Claims. (Cl. 102-52) (Granted under Title 35, US. Code (1952), see. 266) efieotive against high flying aircraft and against the thick armour plate of present day tanks and ships.

In order to achieve this high velocity, it has been the practice to adapt sub-caliber projectiles so that they can be fired from a higher caliber gun. This in effect, provides a greaterrthan normal amount of propellant powder for propelling the projectile. The sub-caliber projectile, not being as heavy as the standard projectile, therefore, has a much greater amount of energy imparted to it and thus attains a greater velocity. One method of adapting a projectile for firing from a higher caliber gun is to encase the projectile in an expendable sabot which provides a' gas seal as the projectile moves through the bore of the gun and which disintegrates as it emerges therefrom so that it does not unduly interfere with the trajectory of the projectile. I

Plastics or fiber reinforced plastics possess certain des-irable properties which make them suitable foruse as a sabot material, since they are light weight non-critical materials and are easily fabricated. l

In spite of the desirable properties of plastics, plastics materials have certain disadvantages for use as sabot material, the major disadvantage being that those plastics-which possessrthe required strength do not engrave properly as the projectile moves through the .bore of the gun while plastics which engrave properly have insufiicient strength to withstand the initial pressure build-up in the' chamber as the gun is fired. w Most sabots are manufactured by machining a plastics billet into a cup-shape of suitable interior dimensions to provide a tapered interference fit between the projectile and the sabot and of external dimensions compatiblewith the bore'of the gun. The machining process is expensive and tends to weaken the sabot to such an extent'that there is a danger that it may break up before the projectile completes its travel through the bore of the gun thereby resulting in erratic and unpredictable trajectories and possible danger to personnel in the immediate vicinity of the gun. Furthermore, slight eccentrioities' f the sabot with respect to the projectile result in stresses being set up in the sabot as it moves through the gun bore thereby increasing the probability of premature breakup within the gun.

Some sabots are presently molded directly onto the projectile in an effort to overcome the disadvantages of a machined sabot.. These sabots burn away. as the proates Patenr.

that the rotating band of the projectile itself contacts the interior of the gun as it nears the muzzle. The sabot is generally enclosed in a combustible envelope in order to assure uniform initial burning of the projectile. Not only must a gun having a special bore be used to fire the projectile, but the sabot must burn at a rapid and precisely controlled rate if the trajectory is to be accurate.

Accordingly, it is an object of this invention to provide a new and improved sabot that is molded directly to the projectile for firing through a standard gun bore, which sabot is adapted to breakup in flight without undue distortion to the trajectory of the projectile.

Another object of this invention is to provide a new and improved molded plastics sabot that is exactly concentric with respect to the projectile. v

' Still another object is the provision of a projectile which includes a relatively thick basic sabot of high strength molded to a slug and a relatively thin plastics bourrelet --rotating bandobturator of suitable engraving properties molded to the basic sabot.

An additional object is the provision of a sabot composed of a filled thermosetting resin to withstand the pressures generated in a gun and a thermoplastic resin shell on the sabot adapted to cooperate with the gun barrel to provide a gas seal and to rotate the projectile as it moves through the gun bore.

A further object is the provision of a plastics sabot having a thin easily engraveable thermoplastic shell on its outer surface to reduce radial compressive loads on the sabot and prevent premature breakup of the sabot in the gun.

A still further object is the provision in a molded plastics sabot having an aerodynamic break-out flange and a. preweakened portion in the sabot to assure controlled breakup thereof.

These and many other objects will become apparent When the following specification is considered in the light of the attendant drawings wherein like numerals designate like or similar parts throughout the views and in which:

' Fig. 1 is an elevation partly in section of a compression mold showing the plastic being molded about the prov jectile to form the basic sabot;

jectile moves through a bore of decreasing diameter so s Fig. 2 is an elevation partly in section showing a mold for forming the relatively weak plastics shell about the basic sabot formed in the first step of the process;

Fig. 3 is a view of a finished sabot and projectile with various parts removed to show the internal structure of the sabot particularly the filled longitudinal slots; and

Fig. 4 is a section taken along the line 4-4 of Fig. 3 andviewed in the direction of the arrows.

Referring now with greater particularity to the drawings'; the mold is formed of a support plate 10 carrying a body 11 encasing a hollow female mold 13 disposed therein.

lower end, as viewed in the drawing, to receive the nose of an armour piercing projectile or slug 16 and to position it accurately within the mold. A plurality of inward- 1y extending vanes 17 are formed integral with mold 13 to provide a series of longitudinal slots 12 in the basic sabot thereby providing a preweakened portion to assure proper breakup of the sabot as the projectile leaves the gun. A quantity of thermosetting plastic is introduced into the mold above the slug 16 and a force or plunger 18 is driven downwardly through body 11 to urge the plastics material into the annular space between the slug 16 and the interior of mold 13. In order to provide greater strength of the basic sabot, a quantity of glass The female portion 13 has an accurately machined, downwardly tapering insert 14 disposed at its of high strength could be used.

characteristics:

11,000 p.s.i.; compressive strength 4,900 p.s.i.; modulus of The physical characteristics of one such resin .(diallylphthalate) are as follows: Specific, gravity 1.55; tensile strength 5000 p.s.i.; compressive strength 20,000 p.s.i.; modulus of elasticity 1.25 X psi. and percentage of elongation 1%.

Thermoplastics, on the other hand, soften when heat is applied andharden upon cooling They. may be reworked'time afteritime. The thermoplastic used as the thin-walled shell is nylon which has the followingphysical Specific gravity 1.14; tensile strength elasticity 420,000 psi; percentage of elongation 60%.

Where a thermosetting resin is used as a mold or where a thermoplastic is molded onto a thermosetting resin there is substantially no adhesion between the twoplastics material material, however nylonthas been found to be especially 7 encased in the outertliefnflo'plasticshell 31 defining the bourrelet area 32 which rides in the grooves ofthe gun barrel, the rotating band area 33 and the obturator 34 which provides a gas seal as the projectile moves through i the gun barrel. i

This outer shell maybe composed of any thermoplastic suitable since it is slippery" and tends to lubricate the bore of the gun as itmoves through the bore. Furthermore, the nylon bourrelet-rotating band is easy on the gun bore and greatly extends the life of the gun. This a has been established in tests of nylon rotating bands on "I'heinsert '14 contains an annular crown or ring 19 V which abuts the slug 16 when it is placed in the mold 13 so that a slight cusped relief portion 15 is formed between the forwardend of the sabot and the projectile. This relief portion 15 forms the aerodynamic breakoutflange 21 is to; be understood that the mold as illustratedin Fig. l is shown only representatively, that is to say the force heating and mold heating apparatus is not shown and the ejection system is shown but schematically as an '20 mm. projectiles.

' form manner.

When i the projectile is ing the. trajectory of the armourpiercing projectile 16 so that the projectile flies unerringly to the target.

The aerodynamic break out flange 21 serves to enhance breakupof the sabot as it moves through the air because this flange acts as a scoop ramming air into the annular I cusp 15 formed between the sabot 27 and slug 16 thereby tending to ripthe" sabot frornthe slug in a radially uni- Although.this inventionhasbeen described with reference to one'e'mbodiment it should be apparentito those "skilled in the art after reading'and understanding the specificatiorithat it is byno means so limited. ,Accordingly, the scope of this invention is to be limited only by the scope of the appended claims.

elongated receptacle 22 extending through a bore inplate 10 and receiving the nose of the projectile which receptacle may bemoved upwardly by raising an externally operable knock out bar 24 after the plunger 18 has been withdrawn from the mold thereby to eject the projectile containing the basic sabot 23.

The projectile, now secured to the basic sabot, is removed from the mold and any excess plastics material such as might be formed due to clearance between the force 18 and the female mold 13 is removed. The projectile containing sabot 23 is then placed in an injection mold of the type shown generally at 25. A quantity of thermoplastic material is injected into the mold through channel 26 and flows into the annular space between basic sabot 23 and the accurately machined mold insert 28. Mold 25 may be of any convenient design and, for the purposes of illustration, isshown as. a-split mold opening along line a-a to permit removal of the finished piece 27 from the mold. .Member 29' centers the projectile and the basic sabot within the mold 28 to assure that the thin outer shell 31 will be disposed symmetrically with respect to the inner shell. The rotating band bourrelet--obturator combination is all formed simultaneously and integrally during this process and the preweakcned longitudinal portions 12 .are filled with the thermoplastic material. The, thermoplastic material is formed over the basic sabot but there is substantially no adherence between them, the locking of the shell to the basic sabot being strictly mechanical thru the grooves in the sabot and the thickened portions of the shell. After the thin outer shell 31 is formed on the basic sabot 23, the entire unit is removed from the mold, the risers are machined off and the shell is ready to be attached to an appropriate cartridge case (not shown) in theconventional manner. A cartridge case retaining lip 35 and a crimping groove 36 are provided for this purpose.

The ultimate configuration of: the shell is best appreciated by referring to Figs: 3 and. 4 which more clearly sliow the projectile 16 surrounded by the basic sabot 23 What is claimedas new and desired to be secured by Letters Patent of. the United States is:

1. An armour piercing projectile comprising; an armour piercing slug, a thick-walledshock resistant plastics basic sabot formed of a thermosetting resin molded to said slug a thin-walled easily engaged shell molded on said basic sabot and'providing; a rotating band assembly for the projectile, said shell being composed of a thermoplastics material and a breakout flange integral with the sabot to insure separation of the sabot and slug during the early stages of the flight of the slug.

2. An armour piercing projectile comprising; an armour portions therein, a deformable thin-walled shell of thermoplastic material formed on the outer surface of said member to provide a readily engraveable rotating band, obturator, and bourrelet at the outer surface thereof and a break out flange formed as partof the member to insure separation of the member and slug during the early stages of the flight of the slug.

3. The projectile of claim 2 wherein the thin-walled shell is composed of nylon.

4. An armour piercing. projectile comprising; an armour piercing slug, a substantially cylindrical thermosetting plastics member disposed about a portion of said slug in intimate contact therewith, said member having a plurality ofjgrooves formed therein to provide preweakened portions in the member to promote breakup of said member during flight, a deformable shell of thermoplastic material formed on the outer surface of said member and filling said grooves thereby providing a readily engraveablerotating band assembly at the outer surface of the member and a mechanical coupling with said member to insure rotation of the cylindrical plastics member with the deformable shell, and a break out flange integral with the member to insure separation of the member and slug during the early stages of the flight of the slug.

5. The projectile of claim t wherein the thermosetting' plastics member is composed essentially of a glas fiber fired the sabot forms a gas seal, against thebore of the gun, guides and rotates the projectilc properly through the bore of the gun and breaks up immediately upon exit from the gun without disturb,

reinforced plastics material and the shell is composed of nylon.

6. An armour piercing projectile comprising; an armour piercing slug, a glass fi ber reinforced thermosetting plastics member molded about said slug, said member adapted to break up during flight of the projectile without substantially alfecting the trajectory thereof, a plurality of grooves formed in said member, an aerodynamic breakout flange formed integral with the foreward end of said member and together with the foreward portion of the slug defining an annular recess formed between the slug and the member, said breakout flange adapted to direct air into the annular recess during flight of the projectile. To promote uniform breakup of the member, a thermoplastics shell formed on the outer surface of said member and filling said grooves to provide a readily engraveable rotating band assembly and a mechanical connection to insure rotation of the plastics member and its molded slug.

7. An armour piercing projectile comprising an armour piercing slug having a body portion and a nose portion, a thick-walled thermosetting plastics basic sabot molded to said slug, a thin-walled comparatively easily engraved thermoplastics shell disposed about said basic sabot and providing a rotating band assembly for the projectile, means integral with said thin-walled shell engaging said thick-Walled sabot to insure rotation of said sabot with said shell and an annular breakout flange, said flange being integral with the sabot and encircling said slug in spaced relation to the nose portion of said slug.

8. An armour piercing projectile comprising an armour piercing slug having a body portion and a nose portion, a substantially cylindrical thick-walled thermosetting plastics sabot disposed about said slug in intimate contact therewith, said member having a plurality of longitudinal grooves formed therein, a comparatively easily deformable thin-walled shell of thermoplastic material formed on the outer surface of said sabot and providing a rotating band assembly for the projectile, said thermoplastic material entering and filling the grooves of the sabot, but not adhering thereto, to insure simultaneous turning of the shell and sabot with its attached slug through mechanical contact, and an annular breakout flange integral with the sabot and formed in spaced relation encircling the nose portion of the armour piercing slug. I

9. An armour piercing projectile according to claim 8 wherein the thin wall thermoplastics shell is composed of nylon.

10.'An armour piercing projectile according to claim 8 wherein the sabot is essentially of a glass fibre reinforced diallylphthalate and the shell is composed of nylon.

11. A method of forming a two-piece plastics sabot for a projectile comprising centering a slug in a compression mold, packing a thermosetting resin about said slug, hardening to form a basic sabot attached to said slug, removing the slug and its attached basic sabot, centering said sabot and slug in an injection mold, and injecting a thermoplastic resin to form a shell about said basic sabot.

Great Britain Mar. 25, 1946