January, 1912.] 



07 



Miscellaneous. 



tice many thousand rods were repeat- 

 edly fired and afterwards tested to 

 yield a few hundreds of satisfactory 

 product. All the cost of making an 

 entire batch would have to be charged 

 against the lew units which might be 

 found satisfactory, and in many cases 

 there were none good in a thousand 

 tested. It was evident that regulation 

 and control of temperature was neces- 

 sary. This was found to be imprac- 

 ticable in case any considerable number 

 were to be fired at one time, as the 

 heated mass was so great that the rods 

 near the walls of the retort received a 

 very different heat treatment from those 

 near the middle, and were consequently 

 electrically different. This was still the 

 ease eveu when electrically heated 

 muffle° were used. This difficulty led to 

 experiments along the line of heated 

 pipe through which the rods could be 

 automatically passed. Some time was 

 spent in trying to make a practical 

 furnace out of a length of ordinary iron 

 pipe, which was so arranged as to carry 

 enough electric current to be heated to 

 the proper baking temperature. Trou- 

 bles here with oxidation of the iron 

 finally led to substitution of carbon 

 pipes. This resulted in a carbon tube 

 furnace, which is merely a collection of 

 six-foot carbon pipes, embedded in coke 

 powder to prevent combustion, and 

 held at the ends in water-cooled copper 

 clamps, which introduced the electric 

 current. By control of this current the 

 temperature could be kept constant at 

 any point desired. When this was com- 

 bined with a constant rate of mechanical 

 feed of the air-dried rods of porcelain 

 mixture, a good product was obtained. 

 For the past seven years this furnace 

 has turned out all the arrester rods, the 

 number produced the last year being 

 over 100,000 units. 



In this work we were also forced to 

 get into close touch with the electro- 

 plating department. The rods had to 

 be copper plated at the ends to insure 

 good electrical contact. The simple 

 plating was not enough. This intro- 

 duced other problems, which I will pass 

 over, as I wish to follow the line of 

 continuous experiment brought about, 

 in part at least, by c ingle investigation. 

 The electric furnace, consisting of the 

 carbon tube packed in coke, was a good 

 tool for other work, and among other 

 things, we heated the carbon filaments 

 for incandescent lamps in it. We were 

 actuated by a theory that the high 

 temperature thus obtainable would 

 benefit the filament by removal of ash 

 ingredients, which we knew the ordin- 

 ary firing methods left there. While 



these were removed, the results did not 

 prove the correctness of the theory, but 

 rather the usefulness of trying experi- 

 ments. It was found by experiment 

 that the graphite coat on the ordinary 

 lamp filament was so completely changed 

 as to permit of a hundred per cent, 

 increase in the lamp life, or over 20 per 

 cent, increase in the efficiency of the 

 lamp for the same life, so that for the 

 past four or five years a large part of 

 the carbon lamps made in this country 

 have been of this improved type. This 

 is the Metallized, or " Gem " lamp. 

 Naturally this work started a great deal 

 of other work along the lines of incandes- 

 ceut lamp improvement. At no time 

 has such work been stopped, but in addi- 

 tion to it, the new lines of metallic fila- 

 ment lamps were taken up. In fact, 

 during the past five or six years, a very 

 large proportion of our entire work has 

 been done along the line of metallic 

 tungsten incandescent lamps. In this 

 we have been able to keep in the van of 

 this line of manufacture. The carbon 

 tube furnace has been elaborated for 

 other purposes so as to cover the action 

 under high pressure in vacuo. Parti- 

 cularly in the latter case a great deal of 

 experimental work has been carried out, 

 contributing to work such as that con- 

 nected with rare metals. In such a 

 furnace, materials which would react 

 with gases have been studied to advant- 

 age. Our experience with the metal- 

 lized graphite led to production 

 of a special carbon for contact 

 surfaces in railway signal devices, 

 where ordinary carbon was interior 

 and suggested the possibility cf our con- 

 tributing to improvements in carbon 

 motor and generator brushes. On the 

 basis of our previous experience and by 

 using the usual factory methods, we 

 became acquainted with the difficulties 

 in producing carbon and graphite motor 

 brushes with the reliability and regular- 

 ity demanded by the motor art- Furnace 

 firing was a prime difficulty. Here 

 again we restored to special electrically 

 heated muffles, where the temperatures, 

 even below redness, could be carefully 

 controlled and automatically recorded. 

 This care aided by much experiment- 

 ation along the line of composition, of 

 proportionality between the sevaral 

 kinds of carbon in the brush, etc., put 

 us into shape to make really superior 

 brushes. The company has now been 

 manufacturing these for a couple of 

 years, with special reference to particu- 

 larly severe requirements, such as rail- 

 way motors. In such cases the question 

 of selling price is so secondary that we 

 can and do charge liberally foi delicacy 



