flush state and when they have passed by the through hole 8 a the through hole 8 a is opened to the vacuum chambers of both the main vacuum cylinder 101 and the auxiliary vacuum cylinder 102 so that a shared vacuum chamber is formed via the through hole 8 a at this time air within the through hole 8 a flows into the shared vacuum chamber but the amount of air that flows in is small enough that the vacuum in the vacuum chamber can be maintained so there is no effect on operation of the vacuum cylinders further as shown in fig2 a and 2 b when the auxiliary vacuum cylinder 102 is non responsive the through hole 8 a is always plugged by the thickness of the piston 32 of the auxiliary vacuum cylinder 102 therefore with respect to sliding of the piston of either of the vacuum cylinders air outside of the vacuum chamber does not newly flow in via the through hole 8 a rather the slight amount of air that is initially present within the through hole 8 a only creates a slight air wall within the vacuum chamber therefore presence of a slight amount of air that is initially present within the through hole 8 a or the structure of the through hole 8 a does not result in an adverse effect so as to prevent vacuum response of the vacuum cylinders or maintaining of a vacuum action counteraction in this apparatus are indicated by arrows x and y and stress in the apparatus is indicated by arrow z fig3 is a cross sectional view for illustrating a modified example of the load weighting.