Audio insulators used widely among audio users are convenient to control the reproduced sound under audio equipment despite the difference in their material and shape. However, there are no theoretical analysis of those works and effects. In this study, to clarify the works of common circular cone used as insulator, its vibration transmission characteristics is evaluated by driving impedance at input by using four-terminal matrix of insulator after describing its input-output by an equivalent circuit. Consequently, we could clarify that the circular cone has a changing frequency point to pass through or insulate the vibration related with material and shape. This tendency is also confirmed experimentally by measuring the attenuation of vibration velocity between input and output ends of them. Moreover, this method is also effective for composite structure to design the vibration transmission characteristic of entire system. This selective transferring characteristic will be useful to eliminate or insulate inevitable vibration.
Lift carts of the type in which the loading platform is lifted up and down by human power are widely used. In the operation of such conventional lift carts, the cart's horizontal movement and the load's vertical movement on the cart's loading platform must be operated separately. This paper presents a novel adjustable lift cart with a function that lifts the loading platform up or down to a desired height while it is moved horizontally by human power. The loading platform of the adjustable lift cart moves forward and upward (or downward) as if it is on a virtual ramp. The adjustable lift cart's structure joins the left and right wheels of the cart to a differential gear whose output is coupled with a Continuously Variable Transmission (CVT) that raises the loading platform up and down. We call this mechanism, which consists of a CVT and a differential gear, “a linear equation mechanism”. In this paper we first propose the concept of a novel adjustable lift cart and explain how our linear equation mechanism can be applied to it. Second, we illustrate a mechanism of the CVT that consists of a roller and wheels and derive the CVT's ratio. Finally, we explain the design of an experimental model of the adjustable lift cart and show experiment results.