Motors: expansible chamber type – With motive fluid valve – Manual control carried on or operated from load or output...
Reexamination Certificate
2001-05-17
2002-12-10
Ryznic, John E. (Department: 3745)
Motors: expansible chamber type
With motive fluid valve
Manual control carried on or operated from load or output...
Reexamination Certificate
active
06490962
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to hydraulic tools, and more particularly to hydraulic tools that can use a constant pressure fluid delivery system or a constant volume fluid delivery system. In particular, this invention relates to a hydraulic tool having a selector sleeve that is selectively adjustable to operate the tool in an “open center” (OC) mode or a “closed center” (CC) mode.
2. Description of Related Art
U.S. Pat. No. 5,778,755 is directed to a control apparatus
22
for operating a hydraulic tool
20
that can use a constant volume or constant pressure fluid system. The constant volume or OC mode of operation is shown in
FIGS. 1-3
, and the constant pressure or CC mode of operation is shown in
FIGS. 4 and 5
.
The control apparatus
22
includes a housing
32
having a cavity
34
in which a piston
36
reciprocates. The piston
36
divides the cavity
34
into a drive chamber
44
, which is positioned to the left of the piston
36
, and a retract chamber
42
, which is positioned to the right of the piston
36
. An adjustment assembly
48
is retained in the drive chamber
44
to control fluid flow between the retract chamber
42
and the drive chamber
44
in a neutral mode. The control apparatus
22
also includes a handle structure
49
containing a valve assembly
50
. Inlet and outlet ports
52
,
54
can be connected to a constant volume or constant pressure fluid source. A central port
56
selectively connects the inlet port
52
with the retract chamber
42
. A cross port
58
communicates with the drive chamber
44
and selectively with the outlet port
54
.
The piston
36
includes a plurality of shuttle valves
66
having shuttle spools
68
that are retained in shuttle ports
70
formed in the piston
36
. Enlarged heads
72
,
74
are provided on each end of the shuttle spool
68
. Each shuttle valve
66
operates along a valve axis
78
that is generally parallel to the central axis
76
.
The adjustment assembly
48
allows the control apparatus to be operated in the OC or CC mode. The adjustment assembly
48
includes a control body or annular member
82
which is attached to adjustment shafts
84
extending through a shaft bore
86
in the housing
32
. The control body
82
can be moved between a first position (
FIGS. 1-3
) and a second position (
FIGS. 4 and 5
) by use of drive heads
96
that are connected to the adjustment shafts
84
, and are accessible to the outside of the housing
32
. In the first position, the control body
82
extends away from a recess
106
, and in the second position, the control body
82
is received within the recess
106
. The control body
82
has an annular shape that provides a continuous circumferential contact surface
102
that can contact the shuttle valves
66
(
FIG. 1
) regardless of their circumferential orientation.
When the adjustment assembly
48
is configured for use with a constant volume system, the shuttle valves
66
are moved as a result of contacting the adjustment assembly
48
when the piston
36
is retracted. Movement of the spool valves
66
unseats valve heads
74
from the shuttle port
70
. By disengaging the heads
74
fluid flows from the retract chamber
42
to the drive chamber
44
when the piston is in a neutral position as shown in FIG.
1
. As shown in
FIG. 4
, the adjustment assembly is spaced away from the spool valves
66
for use with a constant pressure system thereby preventing engagement with the shuttle spool valve
66
causing the spool valve heads
74
to seal the shuttle port
70
when the piston
36
is in a neutral position.
A step-by-step description of the operation is now described. In
FIG. 1
, the adjustment assembly
48
is positioned in the constant volume or OC mode. The piston
36
is in the fully retracted position in which the shuttle valves
66
are opened by contact of the head
72
against the control body
82
. This neutral position allows fluid to continuously flow from the inlet port
52
, through the control apparatus
22
(i.e., the central port
56
, tubular conduit
108
, retract chamber
42
, and around valve spools
66
), and back through the outlet port
54
via cross port
58
.
In
FIG. 2
, trigger
64
is actuated to communicate the inlet port
52
with the cross port
58
, which in turn supplies pressurized fluid to the drive chamber
44
to drive the piston
36
. During this movement, the heads
72
are maintained in their position against the piston. Fluid from the retract chamber
42
is exhausted through the central conduit
108
, the central port
56
and the outlet port
54
.
In
FIG. 3
, the trigger
64
has been released following a crimping operation. Release of the trigger
64
re-establishes communication between the inlet port
52
and the central port, central conduit
108
and the retract chamber
42
to slide the piston
36
to its retracted position. During this movement, the spool valves
66
slide on the piston
36
so that the heads
74
contact the piston
36
, until such time as the piston reaches the fully retracted position. At that time, the heads
72
engage the control body
82
, and the heads
74
are separated from the piston
36
to allow pressurized fluid to pass though the piston
36
and to the outlet port
54
via the cross port
58
.
The closed volume or CC mode of operation is shown in
FIGS. 4 and 5
. The only difference in these figures is that the control body
82
has been placed in the recess
106
so that it does not contact the heads
74
when the tool is in the neutral position, (FIG.
4
). As such, the pressurized fluid (that is supplied via the inlet port
52
, central conduit
56
and tubular conduit
108
) is maintained in the retract chamber
42
and does not pass through the piston
36
.
The operation of the tool in the CC mode in
FIG. 5
is the same as the operation of the tool in the OC mode in FIG.
2
. Further, when the trigger is released, the shuttle valves
66
will slide such that heads
74
contact the piston
36
. However, upon reaching the fully retracted position, the heads
72
will not contact the control body
82
so that constant pressure is maintained on the piston
36
.
U.S. Pat. No. 5,442,992 patent discloses a reciprocating hydraulic tool
20
in the form of a shade tree pruner. The tool
20
includes a cylinder
40
having a piston
34
that reciprocates between a fully extended position and a retracted position. The tool
20
is referred to in the art as a “pull to cut” tool since the blades
26
,
28
of the pruner start in the open position, and when the trigger
90
is actuated, hydraulic fluid is supplied to the side of the piston
34
remote from the trigger
90
. This causes the piston to move toward the trigger, and the blade
26
is pulled toward the blade
28
to perform a cutting operation.
The tool
20
can use either a constant pressure (CC) or a constant volume (OC) source of hydraulic fluid. A selector
60
is rotatably mounted on the cylinder to enable the tool to be used in the OC or CC modes.
FIGS. 1 and 2
show the selector
60
in the OC mode, and
FIGS. 3 and 4
show the selector in the CC mode.
In
FIGS. 1 and 2
, the selector
60
defines a passageway
62
that communicates between opposite sides of the piston
34
when the piston is in its fully advanced position with respect to the cylinder, as shown in FIG.
1
. In this fully advanced position, the piston is fully advanced with respect to the end
58
of the cylinder which is opposite its end
44
at which the valve body
42
is coupled.
In the second position of the selector
60
as illustrated in
FIGS. 3 and 4
, the passage
62
is rotated out of a position for communicating between the opposite sides of the piston
34
. Additionally, the passage
62
mounts a one-way check valve
68
that limits fluid flow to a single direction, from a side
70
of the piston
34
that faces the first end
44
of the cylinder and the opposite side
56
of the piston that faces the opposite end
58
of the cylinder
40
.
In
FIGS. 1 and 3
, the tool
20
is
Pillsbury & Winthrop LLP
Ryznic John E.
The Stanley Works
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