US3351013A

US3351013A - Illuminating mortar shell

Info

Publication number: US3351013A
Application number: US542774A
Authority: US
Inventors: Simmons Bjorn Herman Olof
Original assignee: Bofors AB
Current assignee: Saab Bofors AB
Priority date: 1965-04-20
Filing date: 1966-04-15
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07
Also published as: IL25329A; BE679665A; DE1578055A1; CH444716A; GB1079098A; NL6604035A; AT261450B

Description

Nov 7, 1967 Filed April 15. 1966 B. H. o. SIMMONS 3,351,013

ILLUMINATING MORTAR SHELL 2 Sheets-Sheet l INVENTOR. BJ'R/V HERMAN 01.0: SIMMONS BY Howe, awb NW Nov. 7, 1967 H. o. SIMMONS 3,351,013

ILLUMINATING MORTAR SHELL Fild April 15. 1966 2 Sheets-Sheet 2 INVENTOR. BdbEN HERMAA OLOF SIMMONS BY MM A 7- ram/sm- United States Patent Oflce 3,351,013 ILLUMKNATENG MGRTAR SHELL Bjorn Herman (lief Simmons, Karlskoga, Sweden, as-

signor to Aktiebolaget Bofors, Bofors, Sweden, a Swedish corporation Filed Apr. 15, 1966, Ser. No. 542,774

Claims priority, application Sweden, Apr. 20, 1965,

5,219/65 5 Claims. (Cl. 102-355) ABSTRACT OF THE DISCLOSURE The present invention relates to a luminous or illuminating shell to be fired from a mortar and more particularly to an illuminating mortar shell including a flare to be supported by a parachute after ignition.

Illuminating mortar shells of this kind as heretofore known are inserted, tail end first, into the launching barrel of a mortar. At the bottom of the tube, a striker mechanism actuates a percussion type detonator in the tail portion of the shell. The percussion detonator ignites the propellant charge in the shell which, in turn, develops the required propellant force when ignited. The shell further contains a suitable flare material in its nose end. This material or more specifically the container therefor is attached to a parachute disposed in the tail portion of the shell which is joined to the nose portion by a suitable frangible joint such as a shear pin. After a predetermined flight time of the shell a time fuze usually arranged in the tip of the shell, causes ignition of the flare. As a result, gas pressure is developed which causes the tail portion of the shell to be sheared off from the nose portion. The flare now leaves the nose portion and the parachute is pulled out of the tail portion whereupon the parachute can open to cause a slow descent of the flare.

An illuminating mortar shell of the general kind above referred to has generally a rather poor stability when in flight in that the shell will tend to oscillate about an axis normal to the longitudinal axis of the shell. Such oscillations are highly undesirable but are unavoidably caused by the fact that in illuminating shells of conventional design the center of gravity of the shell is in or close to the tail portion of the shell. Such rearwardly located center of gravity is due to the fact that the tail portion must be made of a material strong and heavy enough to withstand the pressures to which it is subjected during the firing of the shell.

Another disadvantage of illuminating shells of the kind above referred to is that the unfolding of the parachute is uncertain. At the moment of separation of the nose portion from the tail portion the latter has a high moment of inertia so that it will tend to follow closely the parachute and thereby may interfere with the unfolding thereof.

It is an object of the invention to provide a novel and 3,35i,l3 Patented Nov. 7, 1967 improved illuminating mortar shell of the general kind above referred to in which the center of gravity of the shell is moved into or at least close to the nose portion of the shell thereby stabilizing the shell while in flight.

Another object of the invention is to provide a novel and improved illuminating mortar shell of the general kind above referred to in which interference of the tail portion, after separation thereof from the front portion, with the parachute during release and opening thereof is effectively prevented.

Still another object of the invention is to provide a novel and improved illuminating mortar shell of the general kind above referred to the costs of which are materially reduced due to relieving the tail portion of the shell of the high firing stresses experienced by the tail portion of conventional illuminating shells so that the tail portion can be safely made of an inexpensive light weight material such as a suitable plastic.

The afore pointed out objects, features and advantages and other objects, features and advantages which will be pointed out hereinafter are attained by arranging the shell so it can be fired through the launching barrel of the mortar with the tail portion leading. For this purpose, the propellant charge and the ignition means therefor are placed in the nose portion of the shell. As a result, the tail portion is not subjected to the heavy pressure of the propellant gases and can be made considerably weaker and lighter than heretofore possible thereby causing the center of gravity of the shell to move correspondingly forward. Such forward movement of the center of gravity obviously results in a high instability of the shell immediately after it leaves the launching barrel with the tail portion facing forwardly. As a result of such high instability the shell will turn itself around into a position in which its nose portion faces forwardly, that is, the shell will turn itself into a stable position.

As the stress demands on the tail portion are very low due to facing forwardly at the moment of firing, the tail portion can be safely divided into several releasably joined lengthwise parts. These parts of the tail portion will be released from each other and thrown into different directions during the flight of the shell at the moment the flare material in the shell is ignited causing separation of the tail portion from the nose portion. As a result the scattered parts of the tail portion will not interfere with the unfolding of the parachute.

In the accompanying drawing a preferred embodiment of the invention is shown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is a perspective view, partly in section, of an illuminating mortar shell according to the invention;

FIG. 2 shows a mortar in position for receiving a shell;

FIG. 3 shows the shell in three different phases of flight just after it has been fired; and

FIG. 4 is a perspective view showing the parts of the tail portion of the shell after having been just separated from the nose portion and the beginning of the unfolding of the parachute.

Referring now to the figures more in detail, the illuminating mortar shell as exemplified in FIG. 1 comprises a charge 1 of suitable and conventional combustible flare material encapsulated in a cylindrical casing 2 which is closed at one end by a wall 3. The casing and the flare material therein are so constructed in a well known manner that they can be propelled as a unit. End Wall 3 mounts an eye 4 for a ring 5 linked to a second ring 6 to which is secured a cord '7 of a parachute 8 (see FIG. 4).

The end of casing 1 opposite to end wall 3 is closed by a cover 9 which is held in position by a peripheral flange 10 on one end of an outer casing 11 made of suitable sheet material such as sheet metal. A nose cone comprising a cylindrical portion 13 and a frusto-conical portion 14 are secured to cover 9. A percussion type detonator 15 of conventional design is fitted in the tip of frustoconical portion 14. The detonator when activated serves to ignite a propellant charge 16 also placed in frustoconical part 14. The wall of nose cone part 1 2- includes a plurality of circumferentially spaced exhaust ports 17 through which the propellant gases developed when charge 16 is ignited, can escape. Cylindrical nose cone portion 13 contains a suitable priming charge and delay composition both designated by 18. The priming charge serves to ignite flare material 1 at the end of the period of time for which the delay composition is set. Time delay composition and priming charges of this kind are well known in the art and do not constitute part of the present invention.

The tail portion of the shell is in the form of a truncated cone and comprised of two separate sections 19 and 20. A plurality of guide fins 21 are provided at the narrow end of the tail portion. Tail sections 19 and are secured to each other at the outer end by suitable selfreleasing fastening means such as a hook 22 on tail section 19 engageable with a slot or a counterhook on tail section 21) (see FIG. 4). The other ends of tail sections 19 and 20 terminnate in an outwardly turned flange 23 the outer diameter of which is substantially the same as that of casing 2 and is in abutment with the same. Flange 23 is also in engagement with an inwardly turned flange 12 which may be in the form of a plurality of circumferentially spaced lips as is best shown in FIG. 4.

Flanges

12 and 23 join the nose portion and the tail portion of the shell and also sections 19 and 20 and constitute a frangible joint which yields to the gas pressures which are developed during the flight of the shell after firing the same, as will be more fully explained hereinafter,

Referring now to FIGS. 2 and 3, these figures show a portable mortar or launcher suitable for launching an illuminating shell according to the invention. The launcher comprises a box 24 including a support in which one end of a launching barrel 25 is pivotally mounted. The barrel is pivotal between an inactive position in which it is completely within the box and an elevated firing position which is shown in FIGS. 2 and 3. The barrel may be secured in any selected angular position by a rod 27 of variable effective length which is linked to the barrel 25 by a suitable hinge 28. The space in the box not occupied by the barrel in its lowered position may be used as a storage space for shells. A cover (not shown) for box 24 is preferably provided and also a carrying handle so that the entire mortar assembly can be conveniently carried.

The shell and mortar assembly as hereinbefore described operate as follows:

A shell to be fired is inserted into barrel 25 with its nose portion first as it is indicated in FIG. 2 by a hand 29 holding a shell in reversed position. The shell will slide down the barrel by gravity and detonator 15 of the shell will hit a percussion mechanism of conventional design (not shown) provided at the inner end of the barrel. As a result, detonator 15 is activated and ignites the propellant charge 16. The gases now developed escape through ports 17 and the resulting pressure built up ejects the shell from the barrel.

FIG. 3 shows three positions of the shell. One position is the position in which the shell is still reversed, that is, immediately after leaving the barrel. The second position is the one in which the shell has begun to turn due to the previously explained pronounced instability of the shell while flying backwards. The third position shows the shell after it has fully turned and now continues along its trajectory with the nose portion facing forwardly. As has also been pointed out before, in this position the shell is stabilized due to moving forwardly the center of gravity of the shell. At the end of the period of time for which the delay composition coacting with the priming charge 18 is set, the priming charge is activated and ignites flare material 1. The ignited flare material, in turn, develops a gas pressure which when reaching a predetermined magnitude exerts upon the flare material and its casing 2 a pressure strong enough to bend outwardly peripheral flange lips 12. As a result, the tail portion and the nose portion of the shell are separated from each other. Moreover,

tail sections

15 and 20 are released from each other at the forward end. Such release of the tail sections at the forward ends thereof causes a release at the rear ends also by the self-releasing fastening means. Accordingly, the two tail sections will tend to move into the positions of FIG. 4, or into even further scattered positions in which they cannot interfere with the opening of parachute 8.

FIG. 4 shows the condition in which casing 2 with the flare material has just left outer casing 11 and parachute 8 has started to unfold. As is now evident, tail sections 19 and 20 are not subjected to any substantial pressure during firing of the shell. They can hence be made of very light material thereby causing the center of gravity of the shell to be moved forwardly to a substantial extent. As previously explained such forward movement of the center of gravity increases the stability of the shell during flight.

Suitable materials for tail sections parts 19 and 211 are for instance, thin sheet metal or plastic sheets in particular sheets made of a thermoplastic such as polycarbonate or acryl-butadiene styrene (ABS).

While the invention has been described in detail with respect to a certain now preferred example and embodiment 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 invention, and it is intended, therefore, to cover all such changes and modifications in the appended claims.

What is claimed is:

1. An illuminating mortar shell comprising a casing having a hollow nose portion and a hollow tail portion, of lighter Weight than the nose portion so that the center of gravity of the shell is in the nose portion thereof, a propellant charge and a percussion type detonating means disposed in the tip of the nose portion for igniting said charge upon activation of the detonating means, a frangible joint securing said nose portion to said tail portion, a container containing combustible flare material loosely fitted in the part of the nose portion adjacent to the tail portion, a folded parachute disposed in the tail portion and secured to sail container, and ejecting means including time delay means in said nose portion, said ejecting means being activated by ignition of said propellant charge and when activated igniting said flare material at the end of a delay period controlled by said time delay means, ignition of the flare material developing a directional force breaking said frangible joint thereby separating the tail portion from the nose portion and ejecting the container with the parachute attached thereto out of the nose portion.

2. An illuminating mortar shell according to claim 1 wherein said tail portion comprises two lengthwise extending separate sections secured together at one end by said frangible joint and at the other end by self-releasing fastening means, said fastening means being released when said joint is broken.

3. An illuminating mortar shell according to claim 2 wherein said frangible joint comprises an inwardly directed flange at the respective end of one of said casing portions and an outwardly directed flange at the respective end of the other of said casing portions, said flanges overlapping each other, at least one of the flanges being made of a material readily forcible out of said overlapping position by the directional force developed upon ignition of the flare material.

4. An illuminating mortar shell according to claim 3 wherein said inwardly directed flange is on the nose portion and is formed by a plurality of circumferentially spaced lips.

5. An illuminating mortar shell according to claim 1 wherein said ejecting means comprises a combustible priming charge including a time delay composition and is disposed in the nose portion between the propellant charge and the container to effect ignition of the priming charge upon ignition of the propellant charge, ignition of the priming charge causing ignition of the flare material at the end of said delay period.

References Cited UNITED STATES PATENTS 2,362,534 11/1944 Brandt 102-35 3,088,403 5/1963 Bartling et al 102-49 FOREIGN PATENTS 818,967 6/1937 France.

SAMUEL FEINBERG, Primary Examiner. BENJAMIN A. BORCHELT, Examiner. V. R. PENDEGRASS, Assistant Examiner.

Claims

1. AN ILLUMINATING MORTAR SHELL COMPRISING A CASING HAVING A HOLLOW NOSE PORTION AND A HOLLOW TAIL PORTION, OF LIGHTER WEIGHT THAN THE NOSE PORTION SO THAT THE CENTER OF GRAVITY OF THE SHELL IS IN THE NOSE PORTION THEREOF, A PROPELLANT CHARGE AND A PERCUSSION TYPE DETONATING MEANS DISPOSED IN THE TIP OF THE NOSE PORTION FOR IGNITING SAID CHARGE UPON ACTIVATION OF THE DETONATING MEANS, A FRANGIBLE JOINT SECURING SAID NOSE PORTION TO SAID TAIL PORTION, A CONTAINER CONTAINING COMBUSTIBLE FLARE MATERIAL LOOSELY FITTED IN THE PART OF THE NOSE PORTION ADJACENT TO THE TAIL PORTION, A FOLDED PARACHUTE DISPOSED IN THE TAIL PORTION AND SECURED TO SAIL CONTAINER, AND EJECTING MEANS INCLUDING TIME DELAY MEANS IN SAID NOSE PORTION, SAID EJECTING MEANS BEING ACTIVATED BY IGNITION OF SAID PROPELLANT CHARGE AND WHEN ACTIVATED IGNITING SAID FLARE MATERIAL AT THE END OF A DELAY PERIOD CONTROLLED BY SAID TIME DELAY MEANS, IGNITION OF THE FLARE MATERIAL DEVELOPING A