Patent ID: 8529519

Claim:
A tight-sealing cap made of an elastic material for tightly sealing a liquid drug-expelling part of a syringe in which a tubular luer lock part is installed to form a gap around an outer periphery of a luer nozzle, the tight-sealing cap comprising: a thick top surface part providing an external form, said top surface part having a thickness (D), an outer tubular part formed below an outer periphery of said thick top surface part, the outer tubular part having a tip end, and an inner tubular part formed below said top surface part at the inside of and separate from said outer tubular part, the inner tubular part having a tip end, wherein: said inner tubular part is formed such that a tip end portion of said luer nozzle is tightly insertable into said inner tubular part such that said inner tubular part tightly seals said luer nozzle at a contact site between said inner tubular part and said luer nozzle; said outer tubular part is formed such that said luer lock part closely contacts with the inside of said outer tubular part, such that said outer tubular part tightly seals said luer lock part at a contact site between said outer tubular part and said luer lock part; the tip end of said inner tubular part is arranged to protrude in a longitudinal direction relative to the tip end of said outer tubular part a length at the contact site between said outer tubular part and said luer lock part is shorter than a length at the contact site between said inner tubular part and said luer nozzle; and said tight-sealing cap has a height (T), and wherein a ratio of D/T is between 0.20 to 0.50.