Doosan DCT10PV Manual De Funcionamiento Y Mantenimiento página 51

DISASSEMBLING THE DCT10PV AND DCT12PV PICKHAMMERS
GENERAL INSTRUCTIONS
• Clean the Pickhammer outer surface.
• Do not disassemble the pickhammer any further than
necessary to replace or repair damaged or worn parts.
• Whenever grasping a pickhammer or a part in a vice,
always use leather or copper-covered vice jaws to protect
the surface of the part and help prevent distortion. Take
extra care with threaded parts and housings.
• Do not remove any part that is a press fit in or on a sub-
assembly unless the removal of the part is necessary for
repairs or replacement.
• Do not disassemble the pickhammer unless a complete
set of O-rings is available for replacement.
DISASSEMBLY OF THE FRONTHEAD
Screw retainer models
Unscrew retainer (12) off the cylinder (1) and remove chisel
buffer (13) from inside retainer. Remove seal ring (8) from
its groove in the cylinder.
Latch retainer models
Remove nut (17) and fronthead pinch bolt (16) from the fron-
thead (15). Lightly tap the fronthead (using a hide mallet if
necessary) off the cylinder (1).
Press or drift out the two fronthead spring pins (18, 19) and
remove the latch lever (20).
The plunger (22) and plunger spring (21) can be removed
from the fronthead.
MAIN DISASSEMBLY
Grip handle body casting (24) firmly in a vice (use leather or
copper covered vice jaws).
Insert three or four pieces of thin sheet steel approximately
8mm wide up into the muffler and beneath the retaining lip
of the muffler moulding (9) from the handle end of the cylin-
der. This will allow the rubber retaining lip of the muffler to
slide along past the groove in the cylinder nut (11) and make
removal of the muffler easier. Note that the bearing sleeve and
muffler are removed together. Slide muffler (9) and bearing
sleeve (10) off over the cylinder assembly (1).
Use a small screwdriver to disengage the end of the locking
ring (40) from the hole in the cylinder nut (11). Rotate the
locking ring in its groove a little to prevent re-locking. (Re-
moval of the locking ring is not necessary unless replacement
is required.)
Use a large spanner (75 mm) across the flats of the cylinder
nut (11) and unscrew the nut from the cylinder assembly.
Remove the anti-rotation key (7) from its slot in the handle
body (24). The key is provided with an M5 tapped hole to aid
removal by a jacking screw if nessesary.
The cylinder assembly (1) may now be slid from the handle
assembly (23), take care to prevent loss of the cylinder spring
(6) and o-ring (38).
HANDLE DISASSEMBLY
Grip handle body (24) in a vice (use leather or copper covered
vice jaws).
Unscrew throttle valve plug (29) using a 13 mm spanner.
Withdraw throttle valve spring (28), throttle valve ball (27)
and throttle valve plunger (26).
Remove the throttle lever (25) by pressing or drifting out
spring pin (26).
Unscrew quick release coupling (31) from inlet bushing (30).
The inlet bushing (30) can be removed if required though it
is assembled into the handle using a high strength retainer
and disassembly is not normally necessary.
CYLINDER DISASSEMBLY
Note: The cylinder assembly should not be disassem-
bled unless there is evidence of excessive wear of the
piston striking face, or evidence of excessive wear of
the cylinder (1) bore, cushion bore or piston (3) dia-
meters. Physical inspection of the above parts will
require a new cylinder plug (6) and all O-rings to be
available for re-assembly.
Tests to estimate wear in cylinder assembly components.
First thoroughly clean and degrease the whole cylinder
assembly inside and out and blow dry. – Caution: wear su-
itable personal protection, barrier cream, gloves and
eye protection. Read any instructions and warnings
specific to the degreasing agent.
• Piston striking face.
If an indent caused by chisel contact, of approximately
0.5mm deep can be felt in the piston striking face – replace
the piston.
• Cushion wear. (Test dry without oil)
Hold the cylinder so the piston slides fully towards the
valve end. Quickly invert and bring the cylinder vertical
allowing the piston to fall towards the retainer end. If a
metal to metal noise can be heard at the end of the piston
stroke an air cushion is not present and a new cylinder
assembly (1) and /or piston (3) may be required.
Note: Continued use of the hammer with insufficient
cushion will result in premature cylinder failure.
• Cylinder bore or piston diameter wear.
Wear affecting these parts may have occurred if low hit-
ting power is reported.
First ensure all airways into, and out from exhaust ports
including muffler of tool are clear. Disassembly and pre-
cise measurement of the diameters will be required to
confirm wear.
Disassembly
Grip the cylinder (1) horizontally in a vice (use leather or
copper covered vice jaws).
Insert a mild steel bar of approx 20mm diameter by 300mm
long into the nozzle end of the cylinder and using a copper
mallet drive out the cylinder plug (5) with the piston (3).
Note: The cylinder plug (6) is non metallic and is retained
by a lip which will be destroyed when removed in this man-
ner.
Caution:
Wear suitable eye protection, and be aware that the
piston may be ejected or fall and cause injury.
The valve ring (4) may be removed by gently opening at the
split and sliding the ring over the end of the cylinder.
Note: Take care not to stretch the ring.
Remove O-rings (38 may stick in handle body), (37), (36),
and (39).
The nozzle (2) is pressed into the cylinder and retained
with Loctite 601 – do not disassemble unless replacement
is necessary.
The cylinder plugs (35) should not be removed, however check
that they are present.
Inspect valve spring pins (33) and (34) for signs of wear and
security.
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