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Descriptions of Mechanism Parts
This tester is of lever structure, which features compact structure and easy operation. So it is widely used in the
workshops. For the structure of this tester, please refer to Fig-3. The tester is composed of loading and unloading
parts, main shaft parts, lever system, worktable parts and electronic control system.
For normal operation, the specimen is placed on the worktable and the tungsten carbide ball indenter is fitted at the
low end of main shaft. The test forces are amplified by the lever system and applied onto the tungsten carbide ball.
The test force presses the ball indenter into the surface of specimen. After the test forces are removed, the diameter
of indentation shall be measured, by which the hardness value is obtained.
In the front of cast-iron machine body (1), the screw rod seating (2) is fitted, inside which screw rod (5) is fitted.
Over the screw rod, there is replaceable work table (7). The elevation of work table relies on the elevation of screw
rod, which is enabled by hand wheel (4) and nut (3). Lever mechanism is composed of larger lever components
(12), smaller lever components (17) and hoist ring (22), etc.
Test force is applied onto the specimen via lever system. Replaceable weights (24) are hanged on the hoist ring
along the longer arm of larger lever. The composition of weights makes up the following test forces: 1839, 2452,
7355, 9807 and 29420 N (187.5, 250, 750, 1000, 3000Kgf). The application of test forces is carried out
automatically by the loading and unloading parts which are fitted inside the machine body. The rotation of motor is
transferred to the screw rod. When the screw rod descends, the test force is passed onto the indenter via larger lever
(12), smaller lever (17) and main shaft.
Main shaft parts are composed of main shaft bench, main shaft, indenter seating, rotary parts seating, rotary part,
connection nut and connection seating, etc. At idle conditions, the spring limits the connection nut on the
supporting frame so that the main shaft is
pressed closely against the knife support in the center of smaller lever,
maintaining the precise position of main shaft.
Electronic control system is consisted of wiring board of front display screen and photoelectric switches, etc. When
the “START” button is pressed, the motor starts to rotate and the screw rod will descend, test force being applied
and retained. After the test force is retained for a certain time (12s, 30s, 60s), the motor rotates in reverse direction,
screw rod will rise up to remove the test force. Herein, the larger lever will be reset under the action of spring.
When bumper iron chip touches the travel switch, the motor will stop running and the test force is unloaded.
Optical measuring System is composed of micrometer, objective lens, ocular lens and prism. After the indentation
is obtained, turn hand wheel to shift away the indenter, pinpoint the objective lens to the indentation (1x leftwards
and 2x rightwards). Herein, the press shaft of locator parts will be located on the pit groove of locator bumper iron
chip, and then a round indentation pit can be observed within the field of view.
Fig-3 Schematic diagram of mechanism
