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: A stray magnetic field control system compensates for the generation of stray magnetic flux by the magnetic structure (body) of a load support shaker apparatus. The circuit includes a Hall effect magnetic field sensor for measuring the stray magnetic field, an amplifier/filter connected to the sensor output, and an A/D converter connected to the output of the amplifier filter. A degauss coil for compensating for the stray flux is energized by an SCR phase controlled power supply which is in turn controlled as to its triggering time by a microprocessor.

Abstract: A linkage in an electro-mechanical shaker. The linkage has link arms which have two end members coupled to a center member. The three members provide three pivoting points in an axial direction and prevent lateral movement between the relatively movable structures to which they are attached.

Abstract: A load support servomechanism circuit controls the armature of a shaker apparatus. The circuit includes a position sensor, peak detectors connected to outputs of the position sensor, an A/D converter connected to outputs of the peak detectors through a switching bank, a power supply and a microprocessor which provides clock, read, write and ready signals and which automatically controls the position of the armature through solenoids operating on an exhaust valve and a pressure valve. Manual operation of the shaker armature is also provided.

Abstract: An electro-mechanical shaker apparatus utilizing a novel design is disclosed. The shaker apparatus includes an armature frame which is directly coupled to an armature coil to form an integrated unit. The shortened height of the unit effectively raises telescoping resonant frequencies above the spectrum of test frequencies. The armature frame is comprised of a top plate, bottom plate, and an intermediate section to form a laminated/honey-combed design. The top and bottom plates have a higher modulus of elasticity, while the intermediate section has a lower mass density, which effectively raises bending resonant frequencies above the spectrum test frequencies.

Abstract: An electro-mechanical shaker apparatus utilizing a novel design is disclosed. The shaker apparatus includes a bearing housing which includes a plurality of return channels located concentric to the inner wall of the housing. A plurality of balls are positioned between the shaft and inner wall of the housing, as well as in the channels. Top and bottom retainers, having recessed areas which permit the balls to move from the interior position next to the shaft to one of the channels, are placed to enclose the balls within the housing. As the shaft moves axially, the balls recirculate through the channel. Because there are no movement restrictions to balls located in the interior position next to the shaft, the bearing may also be used for rotational movement of the shaft.