Measuring and testing – Vibration – Vibrator
Reexamination Certificate
1999-06-03
2001-04-24
Moller, Richard A. (Department: 2856)
Measuring and testing
Vibration
Vibrator
Reexamination Certificate
active
06220100
ABSTRACT:
TECHNICAL FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a vibration table and, more particularly, to a vibration table that provides substantially uniform vibration across the table to test a plurality of devices mounted on the table for device reliability.
Shaker or vibration tables are often used in an assembly line to screen devices for any possible defects which may result or may have resulted from the manufacturing process. In this manner, products which have defects identified by the vibration table may be screened out of the production line process before being shipped to a customer. Often vibration tables are used in conjunction with a heating and cooling temperature cycling or burn in chamber so that the devices can be further screened for defects that may arise from exposure to elevated and lowered temperatures or from the combined synergism of both temperature and vibration.
Typical vibration tables include a base and a floating platform on which devices are secured or mounted for testing. The vibration table includes a plurality of vibration assemblies or “hammers”, which are secured to the lower surface of the platform to induce vibration in the platform. The vibration assemblies are typically secured to the platform at angles between thirty five degrees (35°) to forty-five degrees (45°) with respect to the vertical axis to induce vibration pulses in three axes of the platform.
FIGS. 21 and 22
illustrate a standard vibrator to table mounting configuration for pneumatic vibrator vibration systems, i.e., a horizontal table with vibrators attached to the horizontal plane. There are varying modifications made to this arrangement by different table manufactures in an effort to produce more desirable table acceleration characteristics, i.e. consistent acceleration levels from point to point and in all three axes (x, y, and z). For example, the vibration tables described in U.S. Pat. Nos. 4,181,026; 4,181,027; 4,181,208; and 4,181,029 each use multiple layers of honeycomb and elastomers to spread and dampen the localized vibration energy of each vibrator. U.S. Pat. Nos. 5,412,991; 5,589,637; 5,675,098; 5,744,724; and 5,836,202 disclose vibration tables which incorporate a very thick aluminum plate for rigidity with cored-out sections to reduce the weight. In U.S. Pat. No. 5,594,177, a table is disclosed which uses two thin aluminum plates separated by spaces to achieve rigidity while still reducing the table weight.
Vibration tables available from THERMOTRON include spacers mounted on top of the table for product mounting to try and isolate the product from acceleration hot spots. As illustrated in
FIGS. 21 and 22
with these standard mounting techniques, there are only three primary force vectors, i.e. a, b, and c. Depending on the rotational position of the mounted vibrator, forces a and b may be imparting acceleration forces in an x direction, a y direction or any angle between the two. Although the plate is solid in most cases, and vibration energy will be distributed over the entire plate, the energy imparted by the vibrator will be greater directly over the vibrator than any other place on the plate.
Notwithstanding these various improvements, heretofore, known vibration tables do not achieve uniform vibration across the platform. As a result, one part on the platform is subjected to one set of vibration levels and another part in another section of the platform is subjected to another set of vibration levels. Consequently, multiple parts tested by a presently known vibration table may not be tested or screened at the same stress levels.
Accordingly, there is a need for a vibration table that can generate substantially uniform vibration energy across the full spectrum of the platform support surface along each of the axes in order to provide a reliable testing procedure.
SUMMARY OF THE INVENTION
According to the present invention, the vibration table includes a base and a floating platform. The floating platform is movable with respect to the base and may be supported via any method that allows the platform freedom of movement in any of the x, y, and z axes, including any rotational directions derived from the three axes. The vibration table translates the pulses generated by the attached vibrators into a multi-axially acceleration spectrum. The vibrators are attached to the table via reinforcing members that act as load spreaders and aid in force vectoring of the vibrator energy pulses.
In a preferred embodiment, the vibration table includes a top plate with a grid of multiple threaded holes for product retention, multiple reinforcing members secured to the underside of the plate with mounting holes for vibrators, and a plurality of support springs to float the platform on a base. The top plate may be of any material that can withstand the high energy impacts of the vibrators without incurring damage. The top plate may be of any physical size or configuration. Furthermore, the number of mounting holes in the mounting hole grid may be increased or decreased as desired and may assume a number of different configurations.
In the preferred configuration, the reinforcing members comprise cross-beams and perimeter beams. Additionally, the reinforcing members may include mounting brackets which are used between the cross-beams and perimeter beams. It should be understood, that other configurations of beams and mounting brackets may also be used. The reinforcing members spread the energy from the vibrators into larger areas on the top plate at lower energy levels. In addition, the reinforcing members vector the energy pulses from the vibrators into a desired horizontal axis brackets x or y. In one preferred configuration, the cross-beams cross the platform lower surface at an angle of 45°. Furthermore, the vibrators are preferably mounted in a range of 35° to 45° with respect to the mounting surfaces of the respective reinforcing members. When the vibrators mounting angles combined with the angular orientation of the cross-beams, the vibrators produce a maximum thrust to the tables x and y axes.
In further aspects, the vibrators are mounted to vertical mounting surfaces of the reinforcing members. By mounting the vibrators to the vertical mounting surfaces of the reinforcing members, the vibration assemblies may now have an adjustable vertical angle in combination with a fixed horizontal angle. This dual mounting angle imparts in effect four energy thrust vectors into the vibration table instead of the three thrust vectors associated with conventional vibration tables. This fourth force vector combined with the load spreading function of the reinforcing members, which also aid in producing more x and y axes motion, create a more even point to point energy distribution across the platform which exhibits less differences between the energy levels of each individual axes x, y, or z than previous vibration table design.
According to one form of the invention, a vibration table includes a base and a floating platform. The floating platform is movable with respect to the base and includes first and second spaced sides, with the first side for supporting articles to be vibrated by the vibration table. The platform further includes at least one projecting mounting surface which extends outwardly from the second side of the platform. The platform is vibrated by a plurality of vibration assemblies, with at least one of the vibration assemblies coupled the projecting mounting surface of the platform.
In one aspect, the platform includes at least one transverse member which extends over and is mounted to the second side of the platform in order to increase the stiffness of the platform. The transverse member includes the projecting mounting surface and may comprise, for example, a beam.
In other aspects, a first group of the vibration assemblies is mounted on the transverse member on the second side of the platform and are angled with respect to the transverse member mounting surface in a range of approximately 40° to 50° and, more preferably, at an angle
Botruff Dwayne D.
Felkins Charles F.
Gilles Gregory M.
Langfeldt Gregory J.
Envirotronics
Moller Richard A.
Van Dyke Gardner, Linn & Burkhart, LLP
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