Popular Science Monthly 



813 



Floor Scrubber Propels Itself 



A MACHINE for cleaning floors has 

 been brought out, so quiet in its oper- 

 tion that it can be used in hospitals and 

 so gentle in its action that a frail woman 

 can manipulate it without difhculty. 

 Its chief feature of interest 

 is that it departs radically 

 from the suction or vacuum 

 type of cleaner. Attached 

 to the lower end of a long 

 iron handle is an indus- 

 trious but small electric 

 motor. As the motor spins, 

 it rotates a circular brush, 

 which can be applied with 

 any desired pressure to the 

 floor surface. Behind the 

 brush motor are two rubber 

 wheels serving a double 

 purpose — to act as a lever 

 for regulating the pressure 

 of the rotating bristles 

 against the floor and as a 

 carriage fcr rolling the equipment from 

 one part of the building to another. 



Because of the brush's rotary motion 

 the machine is self-propelling. Various 

 grades of brushes are supplied for various 

 floor surfaces. For polishing hard- 

 wood floors and mosaic or tile, brushes 

 of other types are employed. 



No matter how swift a ball is thrown it is 

 returned to the player with uniform speed. 



Detachable Blades for Hatchets 



HERE is a hatchet with detachable 

 blades, made possible by spring 



A 



Curved Spring Device Returns 

 Bowling Balls 

 RETARDING 

 device consisting 

 of a spring chute lead- 

 ing from the gutter to 

 the rack in the rear of 

 a bowling alley serves 

 the two-fold purpose of 

 returning all balls to 

 the player and return- 

 ing them without the 

 usual concussion 

 resulting by the 

 method now used. 

 Tiie curved spring 

 has one end firmly 

 fixed to the base of 

 the housing 

 and the other 

 to an 

 a d - 



A simple spring device retards the balls as they return 

 to the player 



clips co-operating with apertures and 



slots of the blades. When attached 



each new blade 



is as rigid and 



stable as the main 



body of the 



hatchet itself, and 



when it becomes 



dull it can be 



readily detached 



and reground. 



Thus the body of 



the hatchet be- 



A detachable blade 



comes continuously serviceable, and one 

 is always assured of a sharp blade. The 

 blades can be economically made by 

 stamping from sheet steel. From the 

 standpoint of pure efficiency the hatchet 

 makes a very eff'ective weapon. 



The motor 



propels the 



brush 



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tor. 



Listening to an Electric Current 

 AX interesting electrical experiment, 

 xVillustrating the fact that sound accom- 

 panies the passage of electricity through 

 the body, can be shown in the following 

 manner: Let two persons each hold an 

 electrode from a small magneto or shock- 

 ing-coil. Let one person, with his free 

 hand, touch the other person behind and 

 just below the ear. A buzzing sound, 

 otherwise inaudible, can be heard. The 

 tone of the sound depends upon the 

 number of interruptions of the current. 



