Pressure Tester of Fruit Maturity 3 



inexpensive, and convenient to use is necessary. The purpose of 

 this circular is to describe such an apparatus. 



DESCRIPTION OF THE APPARATUS 



A general assembled drawing of the pressure tester is shown in 

 Figlire 1, with details of the various parts in Figure 2. The ap- 

 paratus consists of a barrel (N) within which works a plunger 

 (G) attached to the barrel by a steel tension spring (J). At- the 

 end of the plunger rod is the plunger tip (C) which penetrates the 

 fruit. One end of the spring (J) is attached to the upper end of 

 the plunger rod (G), while the other end is attached to the cap 

 (H), which screws on to the end of the barrel, as illustrated. The 

 plunger works freely through the cap (H). When the plunger 

 tip (C) is placed in contact with the fruit the spring is extended 

 in proportion to the pressure applied on the barrel at M. The pres- 

 sure is then read in pounds on the scale on the milled side of the 

 barrel. The sleeve (K), the lower end of which is turned down 

 slightly to reduce the size and painted black as indicated, is at- 

 tached to the top of the plunger rod and fits loosely over the spring. 

 The sharp line between the black paint and the metal surface, 

 termed the " indicator line," which moves directly under the milled 

 slot (O), is the point which shows the number of pounds of pres- 

 sure being applied. 



Details of construction of the plunger tip and the collar (A) 

 surrounding it are shown in Figure 2. As the plunger tip (C) pene- 

 trates the fruit, the collar is pushed up until it comes in contact with 

 the disk (F). A small flashlight is grounded from one side by 

 clamping on to the apparatus as shown. A wire leads from the 

 other side to the insulated ferrule (D). When this ferrule comes 

 into contact with the disk (F) it completes the circuit and lights the 

 flashlight. Consequently, when the plunger has penetrated to a 

 certain definite depth, the flashlight is lighted, and the number of 

 pounds pressure required to force the plunger tip into the fruit for 

 that depth is read directly on the scale. 



DETAILS OF MANUFACTURE 



There are certain precautions and suggestions regarding the manu- 

 facture of the equipment which may be made, based on rather ex- 

 tensive experience with this type of instrument. The barrel (N) 

 is made of stock half -inch brass pipe, the inside of which should 

 be carefully smoothed out. The sleeve (K) which works within 

 this pipe should fit very loosely, with an outside diameter at least 

 one sixty-fourth of an inch less than the inside diameter of the pipe. 

 This is necessary to reduce friction. The spring (J) should in turn 

 fit loosely in the sleeve (K) and about the plunger rod (G) , to reduce 

 friction. 



Considerable difficulty has been experienced in holding the spring 

 (J) firmly attached to the cap (H). The end of the spring should 

 pass through the cap and then over sideways to the edge of the cap, 

 where it is bent down, as shown in Figure 1, and soldered in place. 

 Where a smaller end has been used the tension and twisting of this 

 end of the spring have resulted in the spring breaking loose from the 

 soldering. Then, as tension is applied, the spring slips sideways and 

 in some cases has come into contact with the plunger rod, resulting 



