| 摘要 |
The lance has a hollow outer cylinder (1) with a reciprocating piston (2). The end of the cylinder has a spray head (3). The spray head (3) has two nozzles (4). The piston is hollow and has an internal sleeve (5). A very coarse pitch spiral (7) between the outer cylinder (6) and the piston acts to force water back via an internal valve (14)into a pressure accumulator (11), during the back stroke of the pump.
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