Patent ID: 6951161

Claim:
A safety and arming apparatus for arming a fuze of a smooth bore projectile, comprising: a first sensor and a spin rate sensor, the first sensor in cooperative electronic communication with the spin rate sensor, such that, when the first sensor senses a predetermined first condition and the spin rate sensor detects a predetermined second condition, the predetermined second condition being a predetermined number of spins within a predetermined window of time, the fuze is armed, wherein the spin rate sensor comprises: (a) a counting mechanism for counting each said rotation of the smooth bore projectile as it rotates around its longitudinal axis, the counting mechanism comprising: (i) spin signal mechanism for generating a spin signal which varies over time as the smooth bore projectile rotates about its axis in the earth's magnetic field and where the magnitude of the spin signal reaches a predetermined threshold a predetermined number of times for each said rotation of the smooth bore projectile; (ii) a counter operatively connected to the spin signal mechanism for counting the number of times the spin signal reaches its predetermined threshold; and (b) a spin rate computation mechanism for determining a spin rate of the smooth bore projectile, wherein the spin rate computation mechanism is comprised of a timing mechanism operatively connected to the counter for determining the time for the smooth bore projectile to rotate a predetermined number of times.