Hardness tester

#This invention relates generally to equipment for testing material properties, and more specifically relates to hardness testers used to determine the hardness of a material.

#Penetration hardness testers are well-known in the art. These hardness testers generally include an indentor tip that is driven to apply a load to the test specimen. Some hardness testers known as deadweight testers utilize gravity acting on weights to create the force which drives the indentor into the test specimen. Other hardness testers utilize an electric motor to drive the indentor. In either case, the force or load on the indentor relative to the depth of penetration of the indentor into the surface of the specimen, or relative to the diameter of the indentation, will give a hardness number measured on a common scale such as Rockwell or Brinell.

#Inaccuracies in testing arise due to many sources, such as relative movement between mechanical components. Recent improvements to such hardness testers have come by the use of various electronic equipment, such as load cells to measure the applied force and displacement sensors to measure the depth of penetration. Closed-loop systems utilizing a central processor or computer, especially in conjunction with load cells and displacement transducers, have provided improved reliability to hardness testers. Despite these advances, there remains a need to provide a hardness tester with improved accuracy.

#FIG. 1 is a partially cut-away side view of an embodiment of the hardness tester constructed in accordance with the teachings of the present invention;

#FIG. 2 is a partially cut-away front view of the hardness tester of FIG. 1;

#FIG. 3 is a partially cut-away top view of the hardness tester of FIG. 1;

#Turning now to the figures, the hardness tester 20 generally comprises a frame assembly 30 connected to a tester assembly 60. The frame assembly 30 is best seen with reference to FIGS. 1-3, and generally comprises a very rigid housing including two fabricated sidewalls 32 of a general C-shape. The sidewalls 32 are connected to a bottom wall 34, while six triangular supports 36 provide lateral support to the sidewalls 32. Four holes in the bottom wall 34 can be used to securely mount and level the frame assembly 30. The inner edge of the C-shaped sidewalls 32 are supported by a vertical plate 38 and two horizontal plates 39 extending between the sidewalls.

#Adjacent the end of the lower arm of the C-shape frame 30 are two support plates 40 upon which a block 42 rests. The block 42 supports an anvil 44, which in turn supports the test specimen. At the end of the upper arm of the C-shape frame 30 is a vertically oriented mounting plate 46. The mounting plate 46 includes four mounting holes 47 for bolting the tester assembly 60 to the frame assembly 30. The mounting plate 46 also includes a large hole 48 for passing wires and the like from the tester assembly 60, since the frame 30 can be used to house various electronic components of the tester 20 such as the central processing unit (CPU), the power supply, the signal conditioner, and the capacitor to name a few. Finally, the mounting plate 46 includes two laterally spaced key members 49 that project forwardly to assist in mounting the tester assembly 60, as will be described in more detail herein.

#The frame assembly 30 is preferably welded together as shown, and a housing or cover (not shown) encloses the frame members. Importantly, the sidewalls 32 are fabricated from a single sheet of material such as sheet steel of at least ⅜″ thickness. Alternately, the frame could be cast iron. By fabricating the frame in this manner, the cost and difficulty of casting the frame is eliminated, while a stronger frame is provided. More specifically, the fabricated C-shape reduces the deflection between the upper arm of the C-shape and the lower arm of the C-shape during testing.