TYPEWRITER RIBBONS. 51 



appears overinked or uuderinked, and tendency to smear. If the ribbon is a 

 copy ribbon, take a press copy of the record and make the same observations 

 on the copy and copied original as on the original record. 



4. Life of Ribbon. 



For this test the special machine shown in figure 3 is used. This machine 

 was designed and constructed by F. M. Allen, tool maker for the Bureau of 

 Chemistry. The machine has ten types, including the vowels, both capitals 

 and small letters, each type being mounted on the end of a plunger weighing 

 60 grams. The plunger is raised by a cam, and a uniform blow is obtained 

 by allowing it to fall freely for 1.8 cm. The plungers fall, one after another, 

 in a manner similar to that on a typewriting machine, except that each key 

 strikes a different part of the ribbon. The cams are controlled by a geared 

 mechanism which is operated by an electric motor connected with the testing 

 machine proper by a belt. When a complete line has been struck the platen 

 roll is moved forward one space automatically. The ribbon is fastened firmly 

 at one end and the other end passes over a bar and has clamped to it a weight 

 of 45 grams, thus insuring a uniform tension on all ribbons tested. The paper 

 is fed from a long roll 14 cm wide, or it may be in strips of this width and 



MS. 

 FIG. 3. Machine for testing the life of typewriter ribbons. 



41 cm long (5 by 16 inches). It works under the ribbons as in a typewriter. 

 The life of a ribbon is measured by the number of lines of writing which can 

 be made before one or more holes appear in it or before one or more types 

 fail to make a clear impression. 



5. Resistance to Sunlight and Reagents. 



Cut up the sheets used in making the typefilling test, and subject the original, 

 the copy, and the press-copied original to the same tests as to resistance to 

 sunlight and reagents as were recommended for writing inks. Expose to sun- 

 light for at least fourteen days, and continue the exposure as long as possible. 



6. Rating 1 . 



Length and width are recorded, but are not included in the rating, which 

 is based on quality only, and the ribbons are marked on a scale of 100. Type- 

 filling is given a maximum rating of 5 and is marked as follows : 1,000 or fewer 

 clear impressions of the small letter e, rate as 1 ; 1,000 to 3,000 such impres- 

 sions, as 2; 3,000 to 5,000, as 3; 5,000 to 8,000, as 4; and 8,000 or more, as 5. 



Application for patent requested. 



