| 摘要 |
Pumping and floating pistons ( 70 ) suitable for a hand pump ( 10 ) for a viscous fluid material such as a toothpaste, made of a plastics material coated with a barrier layer ( 75 ). A preferred barrier layer is a thermoplastic elastomer. The barrier layer of the pumping piston may be integrally formed into a one way outlet valve. The barrier layer reduces leakage of components of the fluid material out through the piston, or ingress of environmental components through the piston.
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