Pressure Tester of Fruit Maturity 5 



in markedly increased friction and inaccurate readings.^ This trouble 

 has not been encountered when an ample end has been left for 

 soldering the spring firmly in place. 



The plunger rod (G) should fit loosely through the opening in the 

 cap (H). This cap and the end of the barrel are designed as illus- 

 trated in order to adjust the zero point of the apparatus. The 

 plunger tip is made of monel metal, since brass may not always be 

 sufficiently stiff to prevent bending. Steel, on the other hand, would 

 corrode in the fruit juices to which this portion of the apparatus 

 is continually exposed. By using contact tips, as shown on the 

 collar, all difficulty with poor contact due to the presence of fruit 

 juice, etc., has been eliminated. 



ESSENTIALS OF MANUFACTURE 



While the equipment as a whole should be very carefully made, 

 there are certain details which should be given particular care. The 

 cross-section area and depth to point of contact of that portion of 

 the plunger which penetrates the fruit should be checked carefully. 

 The curvature of the plunger tip should closely approximate that 



BOREO Ano 



TH/^eAOED TO n 



/=t<//iKS£» Tip I 



LOkVEft Cno or pLurfGem ffoo 



— f — I 



OtSK 



FcffnuLC Collar UppeR Eno or Plungcp Rod 



Fig. 2. — Details of various parts of the pressure tester 



shown. Slight variations in the shape of the surface of the plunger 

 tip have been found to have practically no effect on the test, so long 

 as the projected cross area of the plunger tip is correct. The spring 

 which determines the number of pounds pressure being applied 

 should be of the best grade piano-wire steel and when extended by 

 the application of pressure should work freely and easily. It should 

 be carefully calibrated by putting the end of the plunger on an 

 accurate platform scale, pressing down until the scale registers a 

 certain number of pounds, and marking accordingly. When the 

 tester is being used it is important to check the reading from time to 

 time by testing with a platform scale, as heretofore described. An 

 adjustment in the reading is possible by loosening the set screw and 

 moving the cap (H) up or down. 



USE OF THE PRESSURE TESTER ON APPLES 



So far this type of tester has been fairly extensively used only 

 on apples, and the suggestions relative to methods of use are par- 



s Since this description was written, this diflBculty has been overcome by using a 

 threaded cap on which the spring itself is screwed. 



