June 1, 1914. 



THE INDIA RUBBER WORLD 



501 



it will be noted that when operating at full speed the peripheral 

 velocity of the drive roll is 22 inches per second. 



Fig. 2 shows diagramniatically the installation of the magnetic 

 clutch and brake described above. The shaft of the electric 

 motor A carries the driving member B of the clutch. This part 

 of the clutch is mounted on the end of the motor shaft. The 

 end of the driven shaft C carries the armature D of the clutch. 

 Thus it will be seen that when the clutch is 

 disengaged the two shafts are indeiieudcnt 

 of each other. The shaft C also carries the 

 automatic brake li, which is applied when 

 the clutch circuit is broken. The tlirec mills 

 referred to above, only one of which is 

 shown at F, are driven from the common 

 shaft G through the pinion H and gear /. 

 In other respects the drive of the three 

 mills is the same as in any ordinary installa- 

 tion. 



There is installed on each mill a safety 

 switch by means of which the operator can, 

 in case of emergency, open the circuit to both 

 clutch winding and brake .solenoid, thereby 

 releasing the clutch and applying the brake. 

 THE TEST. 



For the purpose of measuring the roll 

 travel from the moment of opening 



the safety switch to the moment of the machinery coming 

 to rest, a tape of drawing paper was glued to tlie periphery 

 of the 20-inch roll. An electromagnet so designed as to 

 be particularly quick-acting was mounted in a position im- 

 mediately above the paper tape on the roll, so that a pencil at- 

 tached to the armature of this electromagnet was held clear of 

 the roll when the magnet was energized ; but when the magnet 

 was de-energized the pencil was dropped on the paper, and the 

 distance traveled in stopping accurately measured thereby. It 

 should be particularly noted that this magnet not only indi- 

 cates the movement of the rolls during the period after the re- 

 lease of the clutch when the brake is bringing the equipment 

 to rest, but it also indicates the time lag between the operation 

 of the safety switch and the releasing of the clutch and applica- 

 tion of the stopping brake, because, as already stated, the pencil 

 relay employed was so designed as to be practically instantaneous 

 in operation. 



The first test made was to start the equipment, bring it to 

 full speed and shut down by opening the motor line switch at 

 a time when none of the mills was loaded. Under these con- 

 ditions the drift of the roll in coming to rest measured 276 

 inches. A second test was made with one mill loaded, under 

 which conditions the distance traveled by the drive roll in 

 stopping was S1.9 inches. 



A second series of tests was made to indicate the travel of 

 the rolls before coming to rest by merely opening the circuit to 

 the magnetic clutch without applying the solenoid brake. Dur- 

 ing these tests the solenoid brake was blocked so as to prevent 

 its application. The first test of this series was made with the 

 rolls operating light, and the distance traveled measured 86 

 inches. With one mill loaded, the distance traveled by the drive 

 roll before stopping was 18 inches. 



The next test was made with the three mills operating light, 

 the clutch and brake circuits being opened simultaneously, and 

 an 18-pound weight being used on the brake lever. Under these 

 conditions the travel of the drive roll was 10.5 inches. During 

 this test it was noted that the brake applied considerably in ad- 

 vance of the releasing of the clutch. 



The weight on the brake lever was next changed from 18 to 

 31 pounds, and two tests were made with this weight on the 

 lever — one with the mills operating light, and the other with 

 one mill loaded. Under the first condition the travel of the 



front roll before stopping was 6.75 inches, and with one mill 

 loaded the travel was 4.5 inches. On both of these tests it 

 was noted that the brake applied considerably in advance of the 

 release of the magnetic clutch, and in one case the mills were 

 practically at rest before the clutch fully released. It was, there- 

 fore, determined to accelerate the releasing of the clutch by 

 arranging to reverse the dircciion of current flow in its wind- 



Di.vcKA.M Showing Inst.\li..\tion of Clutch .\xd Hr.vke. 



ing, a preventive resistance being included in the circuit, which 

 was of such value as to prevent the re-engagement of the clutch 

 after release. Two tests were made with the reverse switch in- 

 stalled, the first of which was made with 18 pounds on the 

 brake lever and one mill loaded, under which conditions the 

 travel was 4 inches; the second with 31 pounds on the brake 

 lever and one mill loaded, under which conditions the distance 

 traveled after operation of the safety switch was only 2 inches. 



As a result of these tests it was determined to install a re- 

 verse switch and to leave the equipment with the 18-pound 

 weight on the brake arm. Under these conditions, as already 

 noted, the travel of the roll periphery, after operation of the 

 safety switch, will be 4 inches with one mill loaded, and less 

 than 4 inches in case more than one mill is loaded. It was 

 not deemed advisable to install the 31-pound weight perma- 

 nently, on account of the severe strains to which the machinery 

 was necessarily subjected to bring the rolls to rest with a move- 

 ment of but 2 inches. 



The following tabulation shows the results obtained in the 



above tests, in a form which will permit of easier comparison : 



Clutch Clutch 



Clutch Clutch 



Circuit Outch Opened, 



Opened Opened, 31 lb. Brake 



, '' , 18 lb. Brake , — '■ * , 



Light 1 Mill Light Light 1 Mill 



86" 18" 10.5" 6.75" 4.5" 



Motor 

 Circuit 

 Opened 



Light 

 276" 



1 Mill 

 51.9" 



Opened Opened 

 and Rev. and Rev. 



18 lb. 31 lb. 



Brake Set Brake Set 

 1 Mill 1 Mill 

 4" 2" 



QUICK CttRING MOLDS. 



A new system of making soft metal mold castings for the 

 manufacture of all blown rubber work is the subject of a recent 

 patent. Under the present system the walls of molds are of 

 unequal thickness. This causes loss of time in vulcanization and 

 cooling, extra effort in handling and uneven vulcanization. 



.The soft metal used also costs from 15 to 25 cents per pound, 

 according to quality, and approximately eighty pounds of metal 

 is contained in a two-cavity mold formed for the purpose of man- 

 ufacturing the ordinary auto horn bulb. Manufacturers fre- 

 quently use more than 500 molds of this sort weighing approx- 

 iinately 40.000 pounds. Under the new process molds are made 

 with the walls of a uniform thickness of about one-eighth of an 

 inch. This is done by means of pressure, by the use of a die 

 and a polished steel plunger. The metal is thus solid and 

 homogeneous, and the interior finished with a glassy, smooth 

 surface, which prevents scaling and warping. A light iron 

 frame outside of the soft metal protects it from injury. 



