US3738279A

US3738279A - Sabot for sub-calibre projectile

Info

Publication number: US3738279A
Application number: US00058027A
Authority: US
Inventors: F Eyre; F Groundwater
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1970-07-24
Filing date: 1970-07-24
Publication date: 1973-06-12
Anticipated expiration: 1990-06-12

Abstract

A sabot for locating a finned missile in a rifled gun barrel, consisting of a rear sealing ring, an intermediate wedge unit and a front petal unit. The sealing ring and wedge unit have peripheral grooves to slidably fit a rifled barrel and the petal unit has a smooth periphery for sliding engagement with lands of the rifling. The petal unit and the wedge unit each consists of a set of separable complemental segments and the two units have complementally frusto-conical adjacent end faces so that the wedge segments are urged outwardly and the petal segments inwardly by a forward axial force on the sealing ring.

Description

United States Patent [1 1 Eyre et a1.

[ June 12, 1973 SABOT FOR SUB-CALIBRE PROJECTILE [75] Inventors: Frank W. Eyre, Montreal, Quebec;

Fergus M. Groundwater, St. Lambert, Quebec, both of Canada [73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: July 24, 1970 [21] Appl. No.: 58,027

52 us. Cl. 102/94, l02/D IG.'7 [51] Int. Cl. F42b 13/16 [58] Field of Search 102/93, 94

[56] References Cited UNITED STATES PATENTS 3,262,391 7/1966 Shober 102/93 2,699,094 l/l955 Musser 102/93 X 3,107,615 10/1963 Brady ..lO2/93X Primary Examiner-Robert F. Stahl AttarneyR. S. Sciascia and J. A. Cooke [57] ABSTRACT A sabot for locating a finned missile in a rifled gun barrel, consisting of a rear sealing ring, an intermediate wedge unit and a front petal unit. The sealing ring and wedge unit have peripheral grooves to slidably fit a rifled barrel and the petal unit has a smooth periphery for sliding engagement with lands of the rifling. The petal unit and the wedge unit each consists of a set of separable complemental segments and the two units have complementally frusto-conical adjacent end faces so that the wedge segments are urged outwardly and the petal segments inwardly by a forward axial force on the sealing ring.

7 Claims, 4 Drawing Figures PMENTED 313%279 INVENTORS Frank W. Eyre Fergus M. Groundwafier 1 SABOT FOR SUB-CALIBRE PROJECTILE This invention relates to new and useful improvements in sabots for locating sub-calibre projectiles or missiles in gun barrels and although the use of the invention is not limited to any particular type of projectile, it especially concerns itself with the locating of finstabilized missiles launched from rifled gun barrels.

In order to increase the muzzle velocity and/or the altitude or range of performance of guns, it is customary in the art to use saboted sub-calibre shells or missiles. Such sub-calibre shells may be either finstabilized or spin-stabilized, but it is undesirable to spin a finned missile at high rates.

It is the principal object of the invention to provide an improved sabot which may be effectively used to transfer gun gas load to a sub-calibre missile in a rifled gun barrel without imparting any excessive amount of spin or rotation to the missile, thereby substantially avoiding spin problems and permitting a significant increase in the velocity and range or altitude of the gun.

Another object of the invention is to provide a sabot which is wholly compatible with the mechanical loading system of conventional guns and which functions effectively in new as well as in worn gun barrels.

With the foregoing more important objects and features in view and such other objects and features which may become apparent as this specification proceeds, the invention will be understood from the following description taken in conjunction with the accompanying drawings, in which like characters of reference are used to designate like parts and in which:

FIG. 1 is a perspective view of a finned missile equipped with a sabot in accordance with the invention;

FIG. 2 is an enlarged fragmentary view, partly in side elevation and partly in longitudinal section, of the missile and sabot thereon; I

FIG. 3 is a fragmentary perspective view showing serrated interfaces of the segments; and

FIG. 4 is a fragmentary perspective view of one of the grooved wedge segments.

Referring now to the accompanying drawings in detail, the general reference numeral in FIG. 1 designates a conventional finned missile of sub-calibre for use in a rifled gun barrel, wherein the missile body 11 is substantially smaller in diameter than the gun barrel and the fins 12 on the rear end portion of the missile body porject radially to a sufficient extent as to ride along lands of the barrel rifling to assist in stabilizing travel of the missile through the barrel. The improved sabot of the invention is positioned on the missile body 11 and is designated generally as 13.

The sabot 13 consists of three main components, namely, a rear sealing ring 14, an intermediate wedge unit 15, and a front petal unit 16. In addition, a washer 17 may be provided between the units l5, 16 as will be hereinafter described.

The sealing ring 14 is made of elastomeric material such as rubber or the like, and is provided integrally at the rear face or end thereof with flared lips 14a, 14b for an effective sealing engagement with the missile body 11 and the gun barrel, respectively. The periphery of the ring 14 is engraved with helical grooves 14c which are complemental to and slidably engageable with the rifled barrel.

The wedge unit 15, disposed forwardly of the sealing ring 14, is preferably made of a suitable plastic material and is also engraved on its periphery with helical grooves for sliding engagement with the rifled barrel. The inside of the wedge unit is provided with a shoulder 18 which is seated in an annular groove 19 formed in the missile body 11, whereby to prevent axial displacement of the wedge unit relative to the missile body. The wedge unit consists of a set of separable, complemental segments, as for example the

segments

15a, 15b, and the radial interfaces between these wedge segments are serrated as indicated at 20 in FIG. 3 so as to provide a labyrinth type seal and prevent gas leakage axially through the wedge unit.

The petal unit 16 is disposed forwardly of the wedge unit 15 and is preferably made of metal, as for example aluminum. The inside of the petal unit 16 is provided with a series of load transfer grooves 24 which mate with a series of grooves 25 formed in the missile body 1 1 to prevent axial displacement of the petal relative to the missile body. The outer periphery of the petal unit is smooth for sliding engagement with lands of the barrel rifling, and the petal unit also consists of a set of separable, complemental segments, as for example the

segments

16a, 16b, 160, as shown in FIG. 1. The radial interfaces between the petal segments are also serrated, as at 21, to prevent gas leakage.

Preferably, the number of segments in the wedge unit 15 is different from the number of segments in the petal unit 16, so that for purposes of preventing gas leakage, the radial interfaces between the wedge segments are always circumferentially spaced from the radial interfaces between the petal segments. Thus, for example, the wedge unit may consist of two segments and the petal unit of three segments.

As an important feature of this invention, the rear of the petal unit 16 and the front of the wedge unit 15 have complemental frusto-

conical faces

22, 23, respectively, slanting forwardly and outwardly as will be apparent from FIG. 2. The aforementioned washer 17 may be interposed between these

faces

22, 23, and may be radially split to facilitate its separation from the missile at the muzzle of the gun barrel, such separation of the petal unit 16 and wedge unit 15 also being possible by separation of the petal segments and wedge segments in each set.

The sealing ring 14, as stated, is made of elastomeric material or the like and separates due to structural failure at muzzle exit.

The exterior profile of the petal unit 16, the wedge unit 15, and the front end of the sealing ring 14 are such as to fit a new gun barrel, but the flared lip 14b at the rear of the ring 14 will also seal against a worn barrel.

When the missile l0 equipped with the sabot 13 is placed in the barrel and the gun is fired, the sealing ring 14 provides an initial gas tight seal against both the missile and the barrel. As the missile travels through the gun barrel, gas pressure against the sealing ring 14 exerts a forward axial force on the wedge unit 15 and on the petal unit 16. This force acts through the complemental frusto-

conical faces

22, 23 so that the segments of the wedge unit 15 are urged outwardly against the barrel while the segments of the petal unit 16 are urged inwardly against the missile, thus centering the petal unit and missile in the barrel and minimizing ballotting loads. Also, some deformation of the plastic wedge segments occurs and generates a secondary travelling seal against the barrel and missile.

In the meantime, the grooved peripheries of the sealing ring 14 and wedge unit 15 slide in the rifled barrel and rotation is thus imparted to these parts. However, the wedge unit 15 slips relative to the petal unit 16 at the washer 17 (or at the

interfaces

22, 23 if no washer is present), with the result that the petal unit 16 rotates at a lower rate. The petal unit 16 may rotate upon the missile in turn so that the missile rotates only at an acceptable low rate of spin by residual friction forces. Finally, at the muzzle exit positive rotation of the wedge unit 15 and acceptably low rotation of the petal unit 16 causes the petal segments and the wedge segments to separate from the missile by centrifugal force.

In many instances it may be desirable for the rear, finned end of the missile to protrude rearwardly into the propellant charge chamber of the gun, and the sabot must therefore enter barrel rifling during loading prior to firing. To facilitate this, the groove engraving 150 at the leading edge of the wedge unit 15 is modified by a reverse bevel as shown at 15d in FIG. 4, so that the grooves of the wedge unit are self-indexing upon entering the barrel rifling.

We claim:

'l. A sabot for locating a finned missile in a rifled barrel comprising, in combination:

a rear sealing ring of elastometric material adapted to seal against the missile and having a grooved periphery for slidable sealing engagement with a rifled barrel;

an intermediate wedge unit disposed forwardly of said sealing ring and also having a grooved periphery for sliding engagement with a rifled barrel, said wedge unit comprising a set of separable complemental wedge segments;

a front petal unit disposed forwardly of said wedge unit for sliding engagement with the lands of a rifled barrel and comprising a set of separable complemental petal segments, the rear of said petal unit and the front of said wedge unit having complemental frusto-conical faces slanting forwardly and outwardly so that the wedge segments may be urged outwardly and the petal segments inwardly by a forward axial force acting on said sealing ring; and

a slip washer interposed between said complemental frusto-conical faces to permit relative rotation of said petal, unit and wedge unit.

2. The device as defined in claim 1 wherein the leading edges of the grooves of said wedge unit are provided with reversed bevels.

3. The device as defined in claim 1 wherein said sealing ring is provided at the rear thereof with flared lips for sealing against the barrel and the missile.

4. The device as defined in claim 1 which is further characterized in that the number of segments in said wedge unit is different from the number of segments in said petal unit, and radial interfaces between the wedge segments are always circumferentially spaced from radial interfaces between the petal segments.

5. The device as defined in claim 4 which is further characterized in that said radial interfaces are complementally serrated.

6. The device as defined in claim 1 which is further characterized in that said petal unit is made of metal.

7. The device as defined in claim 1 which is further characterized in that said wedge unit is made of plastic material.

Claims

1. A sabot for locating a finned missile in a rifled barrel comprising, in combination: a rear sealing ring of elastometric material adapted to seal against the missile and having a grooved periphery for slidable sealing engagement with a rifled barrel; an intermediate wedge unit disposed forwardly of said sealing ring and also having a grooved periphery for sliding engagement with a rifled barrel, said wedge unit comprising a set of separable complemental wedge segments; a front petal unit disposed forwardly of said wedge unit for sliding engagement with the lands of a rifled barrel and comprising a set of separable complemental petal segments, the rear of said petal unit and the front of said wedge unit having complemental frusto-conical faces slanting forwardly and outwardly so that the wedge segments may be urged outwardly and the petal segments inwardly by a forward axial force acting on said sealing ring; and a slip washer interposed between said complemental frustoconical faces to permit relative rotation of said petal, unit and wedge unit.