Abstract: A graduated-load spring washer system for screws and threaded fasteners uses a deflection coil spring of slightly less than one coil with special end configurations for anti-marring. A cross-section of the coil spring is substantially trapezoidal, with the outer periphery thickness being the dimension of the trapezoid base and larger than the inner thickness dimension. When placed under the head of a threaded fastener and flattened upon tightening of the fastener, the device maintains a large tailored preload to prevent loosening even during and after stress relaxation and creep, and eliminates the need for a usual flat washer below the coil to prevent marring. The device also eliminates requirement for use of torque application measuring tools because preload can be determined by sight or tactile sensing.

Abstract: Linear frequency modulation having a large time-bandwidth product and an remely linear frequency versus time waveform, is provided by a feedback technique utilizing a linear ramp voltage generator whose output is summed with a correction voltage to drive a voltage controlled oscillator to output the LFM waveform. Part of the LFM waveform is fed back through a digital discriminator for error signal generation and comparison with a preset value associated with the output slope linearity, thus yielding the basis for generating the correction voltage.