GB578496A - Improvements in instruments for measuring properties of rubber and rubber-like materials - Google Patents

Abstract

578,496. Testing physical qualities. HENLEY'S TELEGRAPH WORKS CO., Ltd., W. T., and MAcDONALD, H. A. Sept. 5, 1944, No. 16917. [Class 106 (ii)] In a rotary cylinder plastometer for measuring the properties of rubber-like materials, the chamber, which houses the driven rotary member and is adapted to be filled with the material to be tested under pressure, is mounted to be rotatable about its axis, but is locked, when it is desired to measure the shearing viscosity, by means which can be released when the rotor is stopped so that the chamber rotates under the forces of recovery to an extent that can be observed with the aid of an indicating device associated with the chamber. In its simplest form (Fig. 1) the apparatus comprises a chamber 1 and rotor 2, between which the material under test is contained under pressure, and an electric motor 6 which drives the rotor through a high ratio worm and worm-wheel gear 8. For shearing viscosity measurements, the chamber is locked by a pin 9 and the torque, which is a measure of the shearing viscosity, is obtained by measuring the endwise thrust on the worm-wheel shaft. By means of relays (not shown) the motor is then switched off and simultaneously a brake 12, 13 is operated electromagnetically. A retarded relay then operates a solenoid which withdraws the pin 9, allowing the chamber to rotate on ball bearings 3 under the forces of recovery of the material, the rotor being locked by the worm gear. A scale on the chamber co - operates with a stationary pointer 11 to indicate the extent of the rotation. Owing to the large inertia of the armature of the motor, it is advantageous to insert a clutch so that the armature may be disconnected from the rotor. The clutch may be inserted between the motor and the reduction gear or between the latter and the rotor as shown in Fig. 3. In this case, when the motor is switched off, a solenoid 26 is also deenergized so that, under the action of a spring 31, a lever 25 disengages the clutch and brings a friction plate 32 on the shaft of the rotor into contact with a similar but stationary plate. The rotor is thus stopped and then further movement of the lever 25, allowed by compression of the spring 35, withdraws the pin 9. To repeat the procedure, the motor and the solenoid 26 are re-energized, whereupon the latter re-engages the clutch and, when the chamber has rotated sufficiently, the pin 9 is pressed into its recess in the chamber under the action of a spring 36.