90 



THE INDIA RUBBER WORLD 



[November 1. 1919. 



New Machines and Appliances. 



ONE of llic first considerations of the rubber engineer in 

 equipping a modern plant is the selection of motors, con- 

 trollers, and safety devices to secure maximum protection 

 to the workmen and uniformity of finished product. 



In the typical installation here shown small constant speed 

 squirrel-cage motors, not requiring any special control ap- 

 paratus, are used for most of the machines ; the three-roll calen- 

 der, however, necessitated an adjustable speed, direct-current 

 motor, special automatic controller, and certain safety features: 

 while the three mixing mills are driven by a slip-ring motor, the 

 liability of accident being reduced to a minimum through the 

 installation of a magnetic clutch and brake operated by safety 

 release switches. 



Direct current is furnished to the calender motor by a motor- 

 generator set consisting of a three-phase, 220-voIt alterating-cur- 

 rent motor and two direct-current generators. A three-wire, 

 double voltage system is used with the two generators connected 

 in series. The calender motor is supplied with either 230 volts 

 by using the combined voltage of both generators, or 115 volts 

 by using either generator singly. By means of the double volt- 

 age system and a field rheostat, a 4 to 1 speed ratio is obtained 

 with the motor, and fine variation may be had at all speeds. 



The motor is started by a push-button switch located con- 

 veniently on the calender. It is stopped by the slight move- 

 ment of either of two cradle-operated switches situated on each 

 side of the calender, or by a push-button safety switch or a 

 push-button master switch, both of which are mounted on the 

 calender. Each cradle has three positions, namely, horizontal, 

 up, and down. The horizontal is the running position, the down 



The three mixing mills, which do not require speed variation, 

 are driven from one line shaft, by a 200-h.-p. slip-ring motor. By 

 using sliding pinions for engaging the large gear wheels of each 

 mixing machine, any of the mixing mills can be thrown out of 

 gear when their service is not needed, but this method of stopping 

 is too slow to be of any value as a safety device. The best 



ETic Control Bo.\rd for Calenders. 



effects an ordinary service stop, while an upward movement 

 causes a quick stop by dynamic braking, accomplished by short- 

 circuiting the motor armature through a resistance. The change 

 from one voltage to the other is made by operating a push-but- 

 ton switch on the control board. The motor field rheostat, which 

 is mounted on the left of the control board, is adjusted by hand, 

 and is short-circuited by a push-button switch on the controller, 

 thus allowing two different speeds — fast and slow — for each 

 setting of the rheostat. The motor can be run in either direc- 

 tion by means of a reversing switch on the control board. 



Magnetic Clutch and Brake Between Motor and Mixers 



Operated by Release Switches. 

 provision for safety would require that any mill in the line 

 could be stopped quickly by some means within easy reach of 

 each operator. 



These requirements were met by inserting a magnetic clutch 

 and brake on the line shaft between the motor and the first mill. 

 F.ach mill is provided with cradle-operated switches for break- 

 ing the circuit energizing the magnetic clutch. Attached to the 

 shaft on the side of the clutch next to the mills is a brake 

 wheel which receives the brake band, which is tightened by the 

 falling of a weight when magnetically released by the operation 

 of one of the cradle switches. Therefore, the braking action is 

 positive, and an accidental interruption of the circuit results in 

 a safe condition. The instant one of the cradles is moved, the 

 clutch is released and the brake applied. (The Cutler-Hammer 

 Manufacturing Co., Milwaukee, Wisconsin.) 



rubber solution and cement mixer. 



The Eimco Cement Churn. 



Rubber cement making has grown in importance and volume 

 during recent years, resulting in the development of special 

 churns designed to reduce the working time and improve the 

 product. For example the mixer here pictured is a strong, 

 heavily built machine designed to stand hard work and the strain 

 of high speed. The mixing tank is of cylindrical type and made 

 of heavy boiler plate. It has a hinged cast-iron man-hole cover 

 which makes the machine absolutely gas-tight and prevents the 

 escape of solvent fumes. 



A special patented agitator is one of the features which it is 

 claimed reduces by one-half the time required to mix the product 

 and also greatly improves the quality. The agitator is so de- 

 signed that it scrapes every inch of the interior of the mixing 

 tank; brings all of the solution into treatment and prevents 

 any of the material from collecting in the corners, thus keeping 

 the inside of the tank clean. 



The speed arrangement permits using a slow mixing action 

 at the start and an exceedingly high speed tn finish the opera- 



