262 



Popular Science Monthly 



A Saw That Stands Up 



ONE of the inconveniences of the 

 ordinary handsaw is that it will not 

 stand readily against a wall or a saw- 

 horse. The least jar causes it to fall. 

 This is neither good for the saw nor 

 pleasant for the owner. 

 A saw invented by 

 a California man 

 has two small 

 teeth on the 

 end of the 

 blade which 

 catch in 



The two small teeth prevent the saw from 

 slipping when leaned against a box 



the floor just enough to keep it from 

 slipping. With these points against the 

 floor only a very slight support at the 

 side is sufficient to keep the saw upright. 



Josef Hoffman Invents a 

 Shock Absorber 



THE avocations of gen- 

 ius are always interest- 

 ing, and sometimes really 

 valuable. The hobby of Jo- 

 sef Hoft'man is science and 

 mechanics, and above all au- 

 tomobiles. He has patented 

 several automobile improve- 

 ments. The latest of these 

 is a pneumatic spring and 

 shock absorber for automo- 

 biles, on which he was re- 

 cently granted a United 

 States patent. 



Mr. Hoffman has found 

 that the ordinary automo- 

 bile spring or shock ab- 



sorber tends to bind when there is a side 

 displacement between the body and the 

 spring, as for example, on a curve. His 

 pneumatic spring is an improved type 

 which is designed to eliminate all the 

 sliding contact both from between the 

 parts of the pneumatic spring and from 

 the parts of the steel springs. 



The device consists of a cylinder, a 

 plunger, a diaphragm, and a connection 

 between the ends of the steel springs and 

 the plunger of the pneumatic spring. 

 The plunger is guided solely by the air 

 held with the cylinder, which contains 

 the diaphragm. Thus, when once the 

 plunger is set centrally within the cylin- 

 der, the air will not permit the plunger 

 head to get out of center; but if, by 

 some unusual force, its center is dis- 

 turbed, the plunger will immediately 

 spring back to its normal position. A 

 perfectly safe guiding of the plunger is 

 thus provided, and all sliding contact 

 eliminated. 



The diaphragm is made of a grooved 

 fal^ric, so as to enable the compressed 

 air in the cylinder to reduce the diam- 

 eter of the plunger. This reduction in 

 size permits the diaphragm to enter the 

 cylinder, whose walls it has shortly be- 

 fore been touching. Thq entire device 

 may be connected to the body and the 

 semielliptic springs of the ordinary car. 



This apparatus is inexpensive and so 

 simple in its construction that it cannot 

 readily get out of order. 



Josef Hoffman found the ordi- 

 nary shock absorbers far from 

 soothing so he invented a 

 pneumatic one of his own 



