Chapter 5 Maintenance and Inspection
UD-series Screw Compressor
5.4 Disassembly and Inspection
5-20
5.4.4 Unloader Cover
The unloader cover [74] is mounted with the indicator cam [77] which converts the linear motion
of the unloader slide valve to a rotational motion, and their mounting parts.
The indicator cam is supported by the ball bearing [78] and fixed to the cover with a bearing
gland [80].
To make it airtight, the V-ring [82], spring [83], and spring retainer [84] are also attached.
The indicator cam has a spiral groove of 340° to cover the moving range of the unloader slide
valve. The indicator cam shaft is rotated being pushed by the guide pin [68] on the top end of the
unloader push rod [67].
Disassembly
a) Unscrew and remove the unloader cover mounting hexagon socket head cap screws [76].
b) Pull the cover out in the direction parallel to the axis of the push rod in the unloader cylinder.
Carefully pull it straight, because if the unloader cover is pulled sideways, the shaft of the
indicator cam may be bent.
c) If the indicator cam will not move normally, check the groove of the indicator cam, bearing,
and guide pin. The disassembly sequence is as follows:
c-1) As the bearing gland [80], which fixes the indicator cam in place, is secured by three
hexagon socket head cap screws [81] on the cylinder side of the unloader cover,
unscrew and remove these bolts.
c-2) Then, the indicator cam can be pulled out with the ball bearing [78] and the snap ring
(retaining ring) [79] attached to the shaft.
c-3) Inside the unloader cover, the spring retainer [84], spring [83], and then V-ring [82]
are assembled in this order. Because the V-ring is tightly engaged with the bore of
the unloader cover, the lip of the V-ring will be damaged when it is once removed,
making it unusable again. Therefore, be sure to replace it with a new one once it is
disassembled.
Unloader Cover
Unloader Cover Mounting Parts
