Method and apparatus for reducing projectile spread

• US 4,765,566 A
• Filed: 03/04/1987
• Issued: 08/23/1988
• Est. Priority Date: 01/29/1986
• Status: Expired due to Fees

• Current Assignee: Aktiebolaget Bofors
• Original Assignee: Aktiebolaget Bofors
• Inventors: Gustafsson, Thomas, Fixell, Jan-Olov, Engfors, Stig, Hogberg, Gosta, Franzen, Arne, Albrektsson, Kjell
• Primary Examiner(s): Jordan, Charles T.
• Assistant Examiner(s): Carone, Michael J.
• Application Number:
  US07/021,827
• Time in Patent Office: 538 Days
• Field of Search: 244/3.1, 244/3.23, 244/3.3, 102/473, 102/501, 273/421, 273/423, 29/1.2
• US Class Current: 244/3.23
• CPC Class Codes: F42B 30/08 Ordnance projectiles or missiles, e.g. shells
• CPC Class Codes: F42B 33/00 Manufacture of ammunition; Dismantling of ammunition; Apparatus therefor F42B5/188 takes precedence; manufacturing processes for hollow charges F42B1/036; manufacture of blasting cartridge initiators F42B3/195
• CPC Class Codes: G01M 1/32 by adding material to the body to be tested, e.g. by correcting-weights
• CPC Class Codes: Y10T 29/25 Lacing-stud making

Abstract

A method and an apparatus for reducing the spread of hit pattern for a rotationally-stabilized ammunition unit such as a projectile, which is discharged in a ballistic trajectory from an artillery piece towards a target which is to be combated including dynamic balancing of the shell (1) to reduce the effect of the air resistance between different shells, and increase hit probability. The inclination between the main axis of inertia of the shell and the geometric axis of the shell case are measured, whereafter these axes are set in parallel in that an adjustment weight (2) is mounted on one side of the point of gravity of the shell seen in its longitudinal direction. The adjustment weight (2) preferably consists of a disk or washer provided with an eccentric recess (4) for suitable weight and mass eccentricity.

Claims

1. A method of reducing the spread of shots in a hit pattern for a rotationally-stabilized ammunition unit in the form of a projectile discharged in a ballistic trajectory from a launching device towards a target which is to be combated, by dynamic balancing of a shell in order to reduce the differences in air resistance between different projectile shells and increase hit probability, comprising the steps of:

measuring the inclination between the main axis of the inertia of said shell and the geometric axis of the shell case

setting said two axes in parallel by providing a weight adjustment on one side of the point of gravity of said shell seen in its longitudinal direction, in the rear region of said shell at the rear plane substantially perpendicular to the longitudinal axis of said shell.

2. A method of reducing the spread of shots in a hit pattern for a rotationally-stabilized ammunition unit in the form of a projectile discharged in a ballistic trajectory from a launching device towards a target which is to be combated, by dynamic balancing of a shell in order to reduce the differences in air resistance between different shells to increase hit probability, comprising the steps of:

measuring the inclination between main axis of inertia of said shell and geometric axis of the shell case,

setting said two axes in parallel by providing a weight adjustment on one side of the point of gravity of said shell seen in its longitudinal direction, in the rear region of said shell at the rear plane substantially perpendicular to the longitudinal axis of said shell, wherein said adjustment weight is mounted in a tracer cartridge of said shell and may constitute retaining means for an igniter of the tracer cartridge.

3. The method as claimed in claim 2 wherein said adjustment weight for adjustment of the imbalance of said shell is also employed for adjusting the weight of said shell.

4. The method as claimed in claim 3 further comprising the steps of:

calculating suitable weight and mass eccentricity for said shell, and selecting therefrom a suitable adjustment weight from a set of calibrated weights of different mass and mass eccentricity.

5. An apparatus for reducing the spread of a hit pattern for a rotationally-stabilized ammunition unit in the form of a projectile shell discharged in a ballistic trajectory from a launching device towards a target which is to be combated, by dynamic balancing of a shell in order to reduce the difference in air resistance between different shells to increase hit probability, comprising;

an adjustment weight located on one side of the point of gravity of said shell, seen in its longitudinal direction, in the rear plane of said shell substantially perpendicular to the longitudinal axis of said shell for parallel setting of the main axis of inerta of said shell and the geometric axis of the shell casing.

6. The apparatus as claimed in claim 5 wherein said adjustment weight includes a washer mounted on the rear plane of said shell.

7. The apparatus as claimed in claim 5 wherein said adjustment weight includes a washer disposed in a tracer cartridge of said shell so that it may simultaneously constitute a retainer means for an igniter of the tracer cartridge.

8. The apparatus as claimed in claim 6 or 7 wherein said adjustment washer is provided with an eccentric recess which determines the mass and mass eccentricity of said washer.