Popular Science Monthly 



423 



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 



