Patent ID: 8752807

Claim:
A seat block comprising: a seat portion base body which is provided in a housing provided with a valve passage and allows at least one valve body for opening and closing the valve passage to be pressed on the seat portion base body; and an elastic mechanism for applying an elastic force to the seat portion base body such that the elastic mechanism cooperates with the housing to retain the seat portion base body; wherein the elastic mechanism is a spring mechanism configured to apply to the seat portion base body the elastic force against a pressing force applied from the valve body pressed on the seat portion base body or from a fluid; and wherein the spring mechanism is a non-linear spring mechanism which is configured to increase a load as a displacement amount of the spring mechanism increases such that an increase rate of the load decreases as the displacement amount increases; and wherein the non-linear spring mechanism is arranged to apply the elastic force to the seat portion base body when the spring mechanism is compressed to a state in which the increase rate of the load decreases as the displacement amount increases.