| 摘要 |
An improved pile driving drop hammer of the free piston internal combustion engine type preferably has integral pistons on each end of a ram that reciprocates, usually vertically, in an enclosing bore. There is a combustion chamber on each end of the bore and exhaust ports situated near each combustion chamber such that the ports are opened, two cycle engine fashion, by the associated piston, after some movement of the piston, after combustion takes place to vent the active combustion chamber and then serve as intake ports when the piston moves some distance farther along the bore. At each end of the bore an anvil extends from the bore, axially movable some amount, to serve as an end to each combustion chamber. The lower anvil delivers ram impact energy to the driven piling and the upper anvil delivers impact energy from the ram to a free rising mass that is the essential element of this invention as an improvement to existing hammer designs. The mass allows impact and combustion energy to be delivered to the downward movement of the ram without delivering lifting energy to the body. The mass rises and falls by gravity influence. Alternatively, a limited force means such as an air cylinder may apply a pull down force between the body and the mass to add some body weight to the ram energy. The down force is limited to an amount that will never lift the body off the driven piling. Controls are provided to time the fall of the mass to achieve advantageous cadence with the reciprocating ram.
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