Page:Popular Science Monthly Volume 90.djvu/439

 Popular Science Monthly

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��Finding a New Use for the Back of a Chair

A FOLDING desk, invented by a young school teacher, Paul Anderson, of Oak- land, Cal., recommends itself for its extreme simplicity combined with exceptional stabil- ity. Neither bolts nor screws are employed in its construe tion. The folding desk i< merely hung over the back of any chair without any ad- justment.

The desk is especially adapt- ed for the tak- ing of notes by students during a lecture, by at- torneys or report- ers during court pro ceedings and in fitt up temporary class rooms in schools. When not in use the desk may be left hanging on the back of the chair; or it may be folded into a com- pact package and easily carried about.

���The desk attachment fits over the back of any chair without bolts or screws

��-Direction of RCfTATioN

��New Cream Separator Governor Is Based on Novel Principles

A STRIKING instance of the simple yet effective in mechanical design is afforded b}' an automatic governor recently devised for use with cream separators.

This new governor consists merely of a small bronze ball which rolls back and forth in 'a slot in the base of a bell, the whole ap- paratus being mount- ed on the cream sepa- rator's handle. If the operator does not re- volve the crank fast enough, the bell rings at every turn. When the speed is right the operator hears only clicks — the bell is silent. If he goes too fast, even the clicks stop, which fact apprises him that he should slow down. This is all there is to the device. There are no indicator hands to watch and no erratic brakes nor clutches to come into action.

The slot in which the ball rolls

��is parallel to the crank handle. One end of the slot is closed; the other is open. In striking the closed end the ball gives forth a "click," while at the open end it rolls against the bell, causing the latter to ring. Two forces act on the ball — gravity, and centrifugal force, which is the same as that causing mud to fly off a buggy In the same way in a bugg}- wheel, this force tends to make the small ball of the gov- ernor fly as far outward as it can get; that is, toward the closed end of its slot.

The further out the handle the gov- ernor is mounted the greater will be the centri- fugal force operating on the ball, and the less swiftly the handle will have to be revolved in order to get the governor to "click- click" in satisfactory fashion. This fact is utilized in adapting the governor to the different makes of cream separators, each of which requires a certain set speed of its own. If upon timing, the speed is found to be too slow, the governor is merely slid closer in toward the center and the oper- ator turns the handle faster.

��DIRECTION OF ROTATION

���The slot in which the ball rolls is parallel to the handle. The ball is thrown toward the closed end of its slot by centrifugal force and is drawn back by gravity

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