Battery electrode hardness tester

An electrode plaque hardness tester of the indentation type for use in testing the hardness of an electrode plaque specimen which is of a thickness of approximately only 0.75 mm and which is made of a non-homogenous, sintered material, said electrode plaque hardness tester comprising:

• a. a frame, including a base member upon which is positioned said specimen of said electrode plaque to be tested for hardness;
• b. means, operably connected to said frame and in contact with said specimen, for applying in sequence a first preselected compression load and a second preselected compression load on said specimen, with said second load being greater than said first load, whereby a first indentation is formed in said specimen by said first load and a second indentation, superimposed on said first indentation, is formed in said specimen by said second load, wherein said compression loads applying means includes:
• a first weight of approximately 100 grams which is used in applying said first preselected compression load;
• a second weight of approximately 400 grams attached to said first weight, wherein said first and second weights are used together in applying said second preselected compression load;
• a drive means for applying said first and second preselected compression loads, with this means connected to said first and second weights, and wherein this means includes a reversible drive motor, and a weight-support line interconnecting said drive motor and said first and second weights;
• and
• means, adjacent said weights and said specimen, for transmitting said first and second compression loads from said first and second weights to said specimen, wherein this means includes a beam balanced on a knife-edge type fulcrum member on said base member of said frame, to allow repeatability to be within a fraction of a gram, with said beam having an indentation-forming member rigidly connected to one end thereof to prevent affecting repeatability, and with said indentation-forming member in contact with said specimen;
• and
• c. means for measuring the depth, respectively, of said first indentation and of said second indentation, thereby a difference between the respective depths is ascertained, and wherein this means includes a linear voltage displacement transducer;
• whereby relative hardness of said specimen is represented by, and is inversely related to, said difference in said depths, in that said specimen is relatively hard if such difference in said depth is relatively small, whereas said specimen is relatively less hard if said difference in said depths is relatively great.