•18 



THE INDIA RUBBER WORLD 



Jiji.v 1, 1921 



cut in strips and thrown into the requisite amount of solvent in 

 the cement mixer. Solution may be effected by churning 18 to 

 20 hours. 



When dissolved the cement is drawn into a tall, narrow tank 



Mill Room 



provided with a cjuick-opening gate-valve at the bottom and one 

 or more similar valves higher up for testing the clearness of the 

 cement. In a settling tank of this sort the solution is allowed to 

 stand until the impurities are deposited. It is customary to allow 

 24 hours for settlement, and at the end of that time to draw off 

 the upper half of the cement, passing it through a fine-mesh 

 brass wire screen as a further precaution before transfer to the 

 dipping tank. 



The cement remaining in the settling tank is sufficiently clean 

 for the manufacture of pure-gum articles of non-transparent 

 grade. But the additional precaution is always taken to strain 

 It through a fine-mesh brass screen when drawn from the settling 

 tank. Settling impurities from the cement is not practiced for 

 stock intended for goods other than transparent nipples, although 

 it is good practice to strain the cement in any event. 



MACHINERY AND PROCESSES 



MILLING AND CEMENT MAKING 



Fig. 3 shows a mill room containing two mills and two cement 

 mixers. These are of the ordinary types. The cement mixers 

 are preferably of the revolving drum type to prevent loss of 

 solvent by evaporation. In preparing rubber cement for any 



l-iG. 4. Cement Mixers and Stor.\ge T.\nks 



purpose, precautions should be observed against fire. One of 

 "thcsS is not to allow the same man to cut the rubber from 

 the mill and place it in the naphtha-filled churn on account-^of 

 the danger from static electric discharge. The gum should be 

 cut and laid down by one person, picked up by a second and by 



him placed in the solvent. Also before opening a tightly-closed 

 cement mixer the pressure of gas should be released at a valve 

 provided for this purpose. 



It is not desirable to soak the rubber before starting the mixing 

 mechanism because that serves to mass the gum and make it 

 difficult to operate the stirrers. Dipping cement should be very 

 thoroughly dissolved to a smooth consistencj-. The process re- 

 quires from 18 to 20 hours for proper completion. 



DIPPING FORMS OR MODELS 



The forms for balloons are usually of wood shellacked, and 

 for other articles, of glass or porcelain. Some of these shapes 



Fig. S. Dipping M.\chines — The Orn.\ment.\l Iron Works Co. 



may be seen in several of the illustrations shown in this article. 

 In service, forms are detachably mounted on bars of wood. The 

 sticks are held in groups for dipping by sliding into grooved 

 cleats on the board seen in Fig. 10. 



DIPPING MACHINES 



A dipping machine comprises a tank for holding the rubber 

 solution and mechanism for lowering and raising the forms on 

 which the goods are made. Such a machine may be designed 

 either for intermittent or continuous dipping and for work with 

 one or more colors at the same time. 



INTERMITTENT DIPPING MACHINES 



A battery of three gear-lift, glove-dipping machines is shown 

 in Fig. 5. These machines are equipped with one truck to locate 

 the cement tank under any one of the three lifts which hold the 

 forms and raise and lower them in the process of dipping. For 

 smaller work a single-lift hand-power machine, operated by 

 hand-crank and link-belt, is generally used. A machine of this 

 sort is set on a fi.xcd tank and the reversible rack holds the 

 form-boards on both sides and allows double dipping or alternate 

 dipping and drying from either side of the rack. Machines of 

 this sort may be identified in Fig. 7. 



.CONTINtjOUS DIPPING MACHINE 



A recently perfected machine for forming dipped go5d!s contin- 

 uously is shown in the accompanying illustration. It is in the 

 form of a reel that revolves on a shaft driven by a chain gear- 



