Repeating elongation-fatigue testing machine of elastic materials under a constant load

Claim 1

In a fatigue testing machine for elastic material repeatedly elongated under a selected load using loading means to load and unload a sample of elastic material to be tested, which sample is grasped at both ends by upper and lower grips respectively wherein the upper grip is connected to said loading means for reciprocating movement, the fatigue testing machine comprising: a weight used to apply a load on said sample when said upper grip is raised until the load on said sample is equal to said weight; a stationary weight base; a weight supporting structure provided below the lower grip and resting on said stationary weight base, said structure being connected to said lower grip so as to apply a load to said sample during the rise of the upper grip wherein said load applied on said sample starts from 0 and increases until equal to said desired weight; a first sensing means responsive to the change of the position of the lower end of said sample and actuating said loading means to cause the upper grip to move back toward the positon when said first sensing means detected the change of the position of the lower end of said sample; and a second sensing means responsive to the arrival of the upper grip, after descending movement, at the original position at which the load applied to the sample becomes zero and actuating said loading means to cause the upper grip to ascend.