310 



THE INDIA RUBBER WORLD 



[June i, 1904. 



accomplished by throttling the steam valve. If the steam 

 pressure on the lines were always uniform, the valve might be 

 so nicely throttled that the temperature could be maintained 

 without appreciable variation, but the steam pressures vary, 

 and the throttling of the valve must be changed frequently to 

 correspond, and the thermometer requires constant watching. 

 With a careless man in charge, this means serious results, but 

 even with the most careful men, the recording thermometer 

 has shown that in most cases it is absolutely impossible to ob- 

 tain uniform results by hand regulation, as the throttling of 

 the valve cannot be changed with sufficient rapidity and ac- 

 curacy. 



On presses, however, such changes are not so apparent, as it 

 takes some time to materially change the temperature of the 

 iron mass. 



RUBBER FACTORY APPLIANCES. 



PEARCE AUTOMATIC MIXER AND FEEDER. 



CARE in handling compound, and in incorporating it evenly 

 and thoroughly, are vital to good mixing, and would seem 

 to be perfectly attained in the device here shown. It consists 

 primarily of a box, into which the compounding materials are 

 weighed in the compound room. This is then carried to the 

 mill that has been fitted with the automatic feeder, and placed 

 in the square case at the top. The box has a sliding bottom 



which when opened allows ne compound to fall into the mix- 

 ing cylinder below. In this cylinder is a mechanism that 

 thoroughly stirs and mixes its contents. After this is done and 

 when the rubber below on the rolls is ready to receive com- 

 pound, a slide in the bottom of the cylinder is opened and the 

 materials drop evenly between the rolls. The feed is so ar- 

 ranged that it may be regulated to suit any type of mixing, and 

 is said to produce the most homogenous mixed sheet that could 

 be desired. In addition to this there is the cleanliness of the 

 method, a more uniform vulcanization, and a decreased shrink- 

 age of the finished sheet. This mechanism can be attached to 

 any type of mixing mills, with rolls of any dimensions. [Far- 

 rel Foundry and Machine Co., Ansonia, Connecticut.] 

 TESTING ACCURACY OF VALVE BALLS. 

 Molded rubber valve balls are usually shaped to fit the 

 mold approximately and pressed twice in position 90 degrees 

 apart in order to form them as nearly as possible into spher- 



ical shape. The resulting balls, even under this plan of 

 double molding, are not strictly spherical. It is always desir- 

 able to determine their accuracy of shape. Perhaps the sim- 

 plest method of doing this is by applying the geometric truth 

 that any section of a sphere is a circle. For this purpose a 

 beveled edge ring, of less diameter than the ball to be tested, 

 is laid on the sphere and moved over its entire surface. All 

 inaccuracies may be plainly detected by inspecting the contact 

 between the ring and surface, the observation being made by 

 viewing the contact toward the light. In this way the extent 

 and location of every deviation from a true sphere becomes ap- 

 parent. 



TESTING THERMOMETERS. 

 All thermometers, and particularly vulcanizing thermom- 

 eters that are not "gas filled," are liable to derangements 

 which result in faulty indications. They should therefore be 

 tested frequently, to insure confidence in their indications. An 

 excellent arrangement for this purpose is that shown in the ac- 

 companyiug illustration. It consists of a 3 or 4 inch wrought 

 iron pipe, about 3 feet long, with capped ends provided with 



steam inlet and outlet. There are a number of openings on the 

 top and side to receive both straight and angle thermometers. 

 The work of verifying any instrument whose readings are ques- 

 tioned is easily accomplished by comparison with a standard 

 thermometer kept as a part of the apparatus. The range of 

 test temperatures is readily controlled by the steam circulation. 



INDIA-RUBBER GOODS IN COMMERCE. 



EXPORTS FROM THE UNITED STATES. 



OFFICIAL statement of values for March, 1904, and the 

 first nine months of five fiscal years, beginning July 1, 

 from the treasury department at Washington: 



CUBAN IMPORTS OF RUBBER GOODS. 



Official statement of values, and of derivation of such im- 

 ports, for the calendar year 1902 : 



