Maintenance
Section 5
Page 43
MSD SABER SERIES SHEARS
SPEED VALVE ADJUSTMENT
continued
REGENERATIVE VALVE DESIGN
The design of the regenerative fl ow valve used in Stanley LaBounty Mobile Shears consists of a pilot valve
mounted onto a spool valve. The pilot valve is used for regulating the movement of the spool valve in shift-
ing the valve into and out of regenerative mode. See
Figure 5-46
. The only component that is in the working
fl ow path of the fl uid to the shear cylinder is the valve spool. The valve spool is of similar construction to that
of the excavator’s main control valve spool. Therefore, it is considerably larger than the components found in
a typical cartridge type regenerative valve.
OPERATING CHARACTERISTICS
The function of the regenerative valve is to provide for rapid advance of the shear hydraulic cylinder during
the closing phase of the shear cycle. The valve accomplishes this function by shifting a valve spool to open
the rod side of the cylinder to the bore side of the cylinder, thus allowing the fl uid in the rod side to fi ll the
bore side when the cylinder is extending. This function only occurs when the cylinder is advancing in a “low
load” condition, which occurs as the shear jaw is closing down onto the material that it is about to be cut. As
the shear enters the cutting phase, the operating pressure requirements increase. The pilot valve portion of
the regenerative valve, which in turn causes the valve spool to shift out of regenerative mode, senses the
increased pressure. During this phase, the rod-side fl uid is directed to the work line and back to the base
machine’s reservoir (low pressure). Meanwhile, only the fl ow from the excavator’s control valve is directed
to the bore side of the cylinder, allowing it to reach full system operating pressure. This allows the shear to
cut by utilizing the full power of the excavator with resistance coming only from the material being cut by the
shear.
TROUBLESHOOTING
There are two operating conditions that affect the
performance of the speed valve and will require
some troubleshooting by an equipment mechanic or
service representative. These conditions are:
a.
The speed valve does not seem to shift out of
regenerative mode at the appropriate time resulting
in the shear appearing to lose cutting power, or
b.
The speed valve does not appear to shift into
regenerative mode resulting in a slow closing move-
ment of the shear jaw. Both of these conditions can
be remedied by following the speed valve adjust-
ment procedure discussed on the following pages.
If making the appropriate adjustments does not
remedy the above conditions, refer to page 6-11 of
this manual for further troubleshooting guidelines. If
further diffi culties are encountered, the speed valve
may require replacement of the hydraulic seals.
Seal kits are available from the Stanley LaBounty
Customer Service Department. Shear serial number
will be required when ordering.
NOTICE
