Method and apparatus for setting a projectile fuze during muzzle exit

• US 4,649,796 A
• Filed: 06/18/1986
• Issued: 03/17/1987
• Est. Priority Date: 06/18/1986
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Schmidt, Jimmy Q.
• Primary Examiner(s): Brown, David H.
• Application Number:
  US06/875,843
• Time in Patent Office: 272 Days
• Field of Search: 89/6.5, 73/167, 324/179, 324/178, 102/209
• US Class Current: 89/6.5
• CPC Class Codes: F42C 17/04 for electric fuzes

Abstract

A method and apparatus for setting a time delay value in an electronic fuze of a projectile exiting the muzzle of a gun barrel, in which a single transmitter coil concentrically mounted to the gun muzzle is utilized both to sense the presence of the projectile at the gun muzzle and to inductively transmit a radio frequency signal having a duration proportional to the fuze time delay value to a receiver coil disposed on the projectile. The transmitter coil is energized from a radio frequency oscillator before the projectile is fired. As the front end of the projectile begins to emerge from the gun muzzle, its presence is detected by a change in the transmitter coil impedance, and the transmitter coil is automatically deenergized. The receiver coil is spaced from the front end of the projectile so that it is not inductively coupled to the transmitter coil, the transmitter coil is reenergized from the oscillator for a time period proportional to the fuze time delay value to be set, then again deenergized until the projectile has completely emerged from the gun muzzle. The signal received by the receiver coil is processed by circuitry within the projectile to set the fuze time delay value.

Claims

1. A method of setting a time delay value in an electronic fuze of a projectile exiting the muzzle of a gun barrel, wherein the time delay value is inductively transmitted in a form of an alternating oscillator signal, from a transmitter coil concentrically mounted to the gun barrel at the muzzle to a receiver coil disposed on the projectile and spaced from the front end of the projectile, during the time period that the receiver coil is inductively coupled to the transmitter coil, comprising the sequential steps of:

connecting the transmitter coil to an oscillator to receive and radiate a fixed frequency oscillator signal;

detecting a change in the transmitter coil impedance caused by the front end of the projectile passing through the transmitter coil;

disconnecting the transmitter coil from the oscillator;

after a first time interval of sufficient duration to allow the receiver coil to begin passing through the transmitter coil, reconnecting the transmitter coil to the oscillator for a second time interval having a duration directly proportional to the time delay value to be set in the fuze, then again disconnecting the transmitter coil from the oscillator, the proportion between the second time interval and the time delay value being selected such that the receiver coil is inductively coupled to the transmitter coil during the second time interval corresponding to a maximum time delay value to be set in the fuze; and

processing the oscillator signal received by the receiving coil to set the time delay value in the fuze.

2. A method, as described in claim 1, which comprises the further step of reconnecting the transmitter coil to the oscillator after the projectile has passed completely through the transmitter coil.

3. A method, as described in claim 1, which comprises the further step of disabling the circuitry in the projectile for performing the signal processing step so that any later signal received by the receiver coil is not processed to set an erroneous time delay value in the fuze.

4. Apparatus for setting a time delay value in an electronic fuze of a projectile exiting the muzzle of a gun barrel, comprising:

a transmitter coil insulated from and concentrically mounted to the gun barrel in front of the muzzle;

an oscillator for generating an alternating oscillator signal at a given signal frequency;

an electrically-actuated oscillator switching means, having first and second control inputs, for connecting the transmitter coil to receive the oscillator signal whenever a switch closing signal is supplied to either the first or second control inputs, wherein a switch closing signal is normally supplied to the first control input and the transmitter coil radiates an electromagnetic field into the gun barrel which interacts with the projectile passing through the transmitter coil to cause a change in the impedance of the transmitter coil;

detector means for sensing the change in the transmitter coil impedance and generating a detector signal indicating that the projectile has started to pass through the transmitter coil;

first switch control means, actuated by the detector signal, for discontinuing the switch closing signal supplied to the first control input of the oscillator switching means, at least until the projectile completely passes through the transmitter coil, to open the oscillator switching means and disconnect the transmitter coil from the oscillator;

second switch control means, actuated by the detector signal, for supplying a switch closing signal to the second control input of the oscillator switching means after a first predetermined time interval for a second time interval proportional to the time delay value to be set in the fuze;

a receiver coil, which is insulated from and mounted to the projectile so that it is inductively coupled with the transmitter coil during a maximum second time interval corresponding to a maximum time delay value to be set in the fuze, for receiving the oscillator signal radiated by the transmitter coil during the second time interval, the receiver coil being spaced from the front end of the projectile so that it is not inductively coupled to the transmitter coil at the beginning of the first time interval; and

signal processing means, disposed in the projectile, for processing the oscillator signal received by the receiver coil to set the time delay value in the fuze.

5. Apparatus, as described in claim 4, which further comprises circuit disabling means, disposed in the projectile, for disabling the signal processing means after the oscillator signal received by the receiver coil has been processes by the signal processing means to set the time delay value in the fuze.

6. Apparatus, as described in claim 4, wherein the first switch control means includes signal reactivating means for reactivating the switch closing signal supplied to the first control input of the oscillator switching means after the projectile has completely passed through the transmitter coil.