Dawson HPH 1200, User Manual

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2.0 HOW DOES THE HAMMER WORK? (See fig. 1)
The D.C.P. Hydraulic Hammer consists of a 'drop weight' driven up and down by a 'hydraulic ram'
inside a 'casing.' The hydraulic ram is double acting which means the drop weight is accelerated
both on the upstroke and on the downstroke. This gives the hammer its very efficient energy output
and high blow rate.
The oil supplied to the hydraulic ram comes from the power pack via a 'control valve' mounted
inside the top of the hammer. This control valve switches the oil supply on or off at the upstroke
side of the hydraulic ram i.e. oil supply 'on' lifts the drop weight and oil supply 'off' drops it.
The control valve itself has to be switched from one position to another at precisely the right times
for optimum performance. The control valve is switched by hydraulic pilot signals from two
mechanically actuated sensors mounted on the hammer casing. The 'bottom sensor,' when actuated
by the drop weight, switches the control valve to the on (lift) position and the 'top sensor' switches
the control valve to the off (drop) position. The stroke of the drop weight is adjusted by moving the
position of the top sensor e.g. moving the sensor down reduces the stroke or vice versa.
The position of the top sensor is altered by a small 'height adjusting ram' mounted inside the top of
the hammer. This is adjusted as required by the operator who can view an indicator on the side of
the hammer.
The hammer is fully controlled using a hand-held control pendant. This unit enables the hammer to
be started/stopped, run on single/automatic blows and have its stroke varied. The controller may be
used from a remote position.