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
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