Origin of Internal Separators

Q. I am curious about the origin of internal separation in vibratory finishers. Perhaps with your background in vibratory finishing you can fill me in. In the late 1960s I had a tumbling job shop with two bowl vibrators that had internal separation devices. I can readily understand that the internal separators are what drove the popularity of round over tub style vibrators. I am wondering where, or when, this improvement was invented.

More than one company has claimed to be the first. Do you have any information on this? R.M.

A. Time tends to obscure history, and maybe some reader can help with this one. The question can be answered, for sure, with a search of old patents—a project for someone else.

The first internal separating vibratory finisher I saw in production was a tub style, not a bowl style, machine. It was called a “MediaMatic,” if my memory is correct. RotoFinish manufactured it in the late 1950s. The machine had two equal-capacity tubs configured such that one tub would empty into the other when the two tubs were rotated about the common axis.

When processing parts, the process tub was in the normal vertical position; the second tub was canti-levered at a right angle. The process tub had a bottom mounted vibrating motor, and the tub was rubber lined. The second tub, probably known as the “receiving” tub, had a screen lid with openings sized to separate parts from media.

At the end of the finishing cycle, the entire system was rotated about 100° while still vibrating. The mass would flow out of the process tub and over the screen deck, the media would fall through into the receiving tub. Parts traveled across the screen and discharged into a waiting container. When the process tub was empty, the system was rotated back, still vibrating, and the media went through the screen again and into the process tub, ready for more parts. The particular system I was familiar with also had a skip loader for parts, and the entire system worked on timers. The next batch of parts would be ready and waiting in the skip loader and the operator would just push a button to start the cycle all over.

The MediaMatic was short lived because it was massive, complex, noisy and had several maintenance issues. Also, round machines were becoming popular, and RotoFinish developed an internal separation system for the round machines. For many years, domestic and foreign equipment manufacturers paid royalties to RotoFinish to use its internal separation invention in helical-bottom round vibrators.

This system allows parts to be processed as long as necessary, then discharged across a screen deck located above the process channel so that media stays in the machine while parts are removed. The machine does not have to be stopped during the transition from process to separation modes. Patents have now expired and most manufacturers of bowl machines offer this system.

Flat-bottom round machines have also been configured in many ways in an attempt to compete with the helix-bottom separation devices. They have met with varying degrees of success. There was an accessory called a “Tilton” (or was it Tilson?) blade. This was a vertical, removable dam installed in the process chamber. It obstructed media travel, causing it to rise up the face of the dam and onto a screen deck installed over the process chamber. Parts traveled across the screen to be discharged while media would fall back in the work chamber.

Other designs have included a hinged dam activated by reversing the flow of the mass, or by powering the dam to raise and lower into the mass. Most of these designs require stopping the machine to install the blade or dam, giving a significant advantage to the helical- bottom design.