Abstract: A shaker test system with a class D power amplifier having an analog to digital converter to receive an analog input signal and convert the analog input signal to a digital signal, pulse width modulation logic coupled to the analog to digital converter to provide a delay time to a delay line to control a transition time of a pulse width modulated signal responsive to an output of the analog to digital converter, and a class D power output stage coupled to the delay line and responsive to the pulse width modulated signal to provide an output of the class D power amplifier stage. The class D amplifier allows use of a low cost microcontroller to obtain very small pulse width increments using a low cost microcontroller to provide a low cost shaker test system incorporating the class D power amplifier.

Abstract: A vibration mount having a body for coupling to an object to be supported by the vibration mount, a flexible member forming a foot on the body and together with the body, forming a chamber therein, a center member within the chamber and coupled to move in unison with the body, a valve having a first valve member coupled to move in unison with the central member and a second valve member coupled to move in unison with the flexible member, a connection for coupling air under pressure to the chamber through the valve member, and a vent for venting the chamber though the valve.

Abstract: Shakers and methods of testing suitable for various applications, including those presenting adverse test environments. The shakers have a permanent magnet assembly mounted in a sealed housing for vibration along a shaker axis. The permanent magnet assembly is double ended, and includes at least one shorting ring to hold down the inductance of the driving coils at higher frequencies. Fluid cooling (or heating) of both the shaker housing and the permanent magnet assembly allows placement of the shakers inside a temperature test chamber. The shakers may be coupled directly to the article to be tested, or coupled singularly or in a plurality to a test table to which an article to be tested is coupled. Various embodiments and methods of testing are disclosed.

Abstract: An improved mail sorting computer keyboard, having a plurality of keys arranged in first and second groups for rotational movement, is provided. A first rod is disposed through apertures of each key of the first group of keys while a second rod is disposed through apertures of each key the second group of keys. A third rod extending transversely across the keyboard and under a front portion of the first group of keys and a fourth rod extending above the first group of keys define the rotational arch for the first group of keys. A fifth rod transversely disposed under a front portion of the second group of keys and a sixth rod transversely disposed under the rearward portion of the second group of keys defines the rotational arch for the second group of keys. Each key of the keyboard actuates a corresponding electrical switch for sending impulses to a mail sorting computer.

Abstract: An optical switch for use as a modular keyboard switch designed to provide tactile and audible feedback to the keyboard operator. The switch includes an opaque housing in which a light emitting device and a light activated detector are mounted. A "U" shaped spring shutter rests within the housing between the emitter and detector and has an aperture through which light from the emitter may illuminate the detector. A spring loaded key stem moves longitudinally within the housing and is designed to penetrate the open end of the shutter. The key stem and shutter are shaped such that as the key stem is depressed the upwardly extending arms of the shutter are at first forced outward by projecting shoulders on the key stem and then snap back along upwardly sloping surfaces of the shoulder, thereby causing the shutter to spring upwards and block the optical path between the emitter and detector. The snap action of the shutter causes an audible "click" and also provides tactile feedback to the operator.

Abstract: An improved switch assembly is disclosed, having particular application as part of a key in a computer keyboard. The switch includes a housing including a base, having electrical contacts secured above the base of the switch housing. A generally flat and deformable electrically conductive spring having a central area with outwardly extending spiral arms is disposed above the electrical contacts. A keystem is slidably mounted for longitudinal movement within the housing above the flat spiral spring. A user activates the switch by depressing a key cap mounted to the keystem, which deforms the spiral spring downward and forcing a portion of the spring against the electrical contact, thereby completing the circuit. The keystem includes outwardly extending tapered cam nubs. A "hairpin" cam spring is provided which in an inactive state rests in an oversize slot below the outwardly extending keystem cam. The depression of the key cap forces the tapered cam to spread the cam spring.

Abstract: An improved switch assembly is disclosed having particular application as part of a key in a computer keyboard. The switch includes first and second pairs of spaced apart electrical contacts, the first pair extending above the second. A conductive and resilient diaphragm is disposed over both pairs of contacts physically contacting only the first. A deformable generally bell shaped actuator member is disposed over the diaphragm, the walls of the actuator member being tapered in thickness so as to buckle upon the application of a known vertical force. Actuator means are provided to deform the actuator member in response to the activation of the switch by a user, thereby forcing the diaphragm to physically contact the second electrical contact completing a circuit.