12
retaining ring is arranged at its left, and a tool withdrawal groove is located at the center of the valve spool, then
a radial through-hole is drilled on the valve sleeve which is matched with the tool withdrawal groove. The limit
valve is developed and designed into a reasonable and ingenious structure, the radial through-hole, tool
withdrawal groove and spring are perfectly mounted, thus not only effectively controlling the diaphragm
flexural deformation of the a limit spring at the rear dead point and automatically controlling the oil make-up
quantity, but also improving the measurement accuracy of pump and the service life of diaphragm.
A.
Structure (see Figure 6)
1
2
3
4
5
6
7
Serial number
Code
Name
Quantity
Material
1
GB894.1-1986
Retaining ring 14
65Mn
2
GB894.1-1986
Retaining ring 22
65Mn
3
GB3452.1-1982 O-ring 17x2.65
4
GB3452.1-1982 O-ring 20x2.65
5
Limit valve sleeve
45
XWF-45-01
6
XWF-45-02
imit valve spring
4Cr13
7
XWF-45-03
Limit spool
40Cr
1
1
1
1
1
1
1
NBR
NBR
Figure 6 Structure Diagram of Limit Valve
The limit valve is mainly composed of valve sleeve, valve spool and limit spring. The complete set of limit
valve is installed at the center of the cylinder block and fixed with a circlip for shaft, and two O-rings (see the
structure diagram of pump hydraulic end) are placed on the outer ring of limit valve sleeve for connecting the
limit valve to the cylinder block seal. Furthermore, the valve spool fits valve sleeve with a clearance left so that
they can axially move under the action of spring, and a circlip for shaft is installed at the end of the valve rod for
limiting the axial movement of the valve spool. The through-hole in the middle of the valve sleeve and
corresponding small groove in the middle of the valve rod are used as oil makeup channels of the valve spool.
Common diaphragm ruptures mainly result from failure of the two O-rings on the limit valve sleeve or excessive
fit clearance between the limit valve spool and the valve sleeve, so the diagram shall be checked and controlled
during maintenance.
