Motors: expansible chamber type – Single chamber formed by mutually relatively movable...
Reexamination Certificate
2000-03-20
2001-07-10
Lin, Kuang Y. (Department: 1722)
Motors: expansible chamber type
Single chamber formed by mutually relatively movable...
C091S18900A, C060S560000, C164S314000
Reexamination Certificate
active
06257117
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fluid cylinder for driving a die applied to a die-casting or injection machine or the like, and more particularly to a cylinder apparatus that pulls a piston rod with a strong force at the time of opening a die, and operates quickly at other stages.
2. Description of the Related Art
In a die-cast machine or an injection machine, at the stage at which a die is set into a cavity and closed, there is generally a need for quick movement, but no need for a large driving force, while at the stage of opening a die, at the initial, short step of peeling the die away from the product during cooling, there is a need for a large driving force. However, once the die is peeled away to the open condition, there is a need for quick retraction of the die, similar to the case of the step in which the die is set.
Seen from the cylinder side, in the above-noted steps there is a need for quick drive at the step in which the piston rod is extended, and a need for a large driving force at the initial step of pulling in the piston rod after it is extended, after which there is a need for quick retraction.
With respect to the need for the above-described functional requirements, cylinder apparatuses having a variety of constructions have been developed in the past, an exemplary one being that of Japanese Patent No. 2623075, granted for a “fluid cylinder.”
This fluid cylinder is shown in
FIG. 13
of the accompanying drawings, and is described as “fluid cylinder comprising a cylinder casing
113
having its interior formed with a main cylinder chamber
111
and a pressure intensifying cylinder chamber
112
; a main piston
117
, slidably housed in said main cylinder chamber
111
and provided with a piston rod
114
linked to a load on its front edge side, for sectioning said main cylinder chamber
111
into a front main cylinder subchamber
115
positioned on the front side and a rear main cylinder subchamber
116
positioned on the rear side; a front supply/discharge path
118
, formed within said cylinder casing
113
, for supplying a fluid to said front main cylinder subchamber
115
; a rear supply/discharge path
119
, formed within said cylinder casing
113
, for supplying the fluid to said rear main cylinder subchamber
116
; and a pressure intensifying piston
123
, slidably housed in said pressure intensifying cylinder chamber
112
, for sectioning said pressure intensifying cylinder chamber
112
into first and second pressure intensifying cylinder subchambers
120
and
121
positioned on one side but shut off from each other in terms of a fluidity and an other-side pressure intensifying cylinder subchamber
122
positioned on the other side, wherein said first pressure intensifying cylinder subchamber
120
is connected to said front main cylinder subchamber
115
, said second pressure intensifying cylinder subchamber
121
is connected to said rear supply/discharge path
119
, said other-side pressure intensifying cylinder subchamber
122
is connected to said front supply/discharge path
118
, a large fluid force acting backward is imparted to said main piston
117
by guiding a high pressure generated in said first pressure intensifying cylinder subchamber
120
to said front main cylinder subchamber
115
with a movement of said pressure intensifying piston
123
toward one side when the fluid is supplied from said front supply/discharge path
118
to said other-side pressure intensifying cylinder subchamber
122
, and said pressure intensifying piston
123
is, on the other hand, moved up to an other-side limit in advance of said main piston
117
when the fluid is supplied from said rear supply/discharge path
119
to said rear main cylinder subchamber
116
and said second pressure intensifying cylinder subchamber
121
.”
While it is difficult to comprehend from the above-noted basic constitution alone, with regard to, as recited in a dependent claim, the pressure intensifying piston
123
must be interpreted as “being constructed of a cylindrical portion
124
and a disc member
125
having its outer periphery integrally linked to the inner periphery of the other edge portion of said cylindrical portion, said first pressure intensifying cylinder subchamber
120
is, at the same time, disposed in a face-to-face position with one edge surface of said cylindrical portion
124
, said second pressure intensifying cylinder subchamber
121
is disposed in a face-to-face position with one edge surface of said disc member
125
, said other-side pressure intensifying cylinder subchamber
122
is disposed in a face-to-face position with the other edge surface of said disc member
125
, and said cylindrical portion
124
is, further, slidably fitted to the outer portion of said main piston
117
.
The first pressure intensifying cylinder subchamber
120
and front main cylinder subchamber
115
are connected by forming a path within the main piston
117
, and a valve
126
is provided midway in the rear supply/discharge path
119
, when the rear supply/discharge path
119
or front supply/discharge path
118
is at a set pressure, receives this pressure and opens, and which is closed when both the supply/discharge paths
118
and
119
are at a low pressure, the closed valve
126
causing fluid locking of the rear main cylinder subchamber
116
, thereby limiting the movement of the main piston
117
.
Referring to the patent publication, the operation of the above-noted fluid cylinder is as follows. (Because this application omits the drawings that illustrate the operation steps described below, it is recommended that the drawings in the cited patent publication be referred to as the following description is read.)
First, the main piston
117
(referring collectively to the large-diameter piston
127
and the small-diameter piston
128
) is at the forward limit, the large-diameter piston
127
being in contact with the bottom part of the first cylinder tube
113
a
, and the small-diameter piston
128
being stopped in contact with the stopper
129
of the large-diameter piston
127
, with the pressure intensifying piston
123
is at the rear limit, stopped in contact with the rear cover
130
.
At this stage, because the front supply/discharge path
118
and the rear supply/discharge path
119
are both connected to a tank and at a low pressure, the spools
131
and
132
are impelled by the springs
133
and
134
, so that they are pressed up against the respective valve seats, so that the front valve
135
and the rear valve
126
are in the closed condition.
Therefore, the front main cylinder subchamber
115
, the other-side pressure intensifying subchamber
122
, and the rear main cylinder subchamber
116
are in the fluid locked condition, thereby fluidly limiting the movement of the main piston
117
and the pressure intensifying piston
123
.
At this stage, the piston rod closes the die at the extension limit, and the piston rod
114
is fixed because of the above-noted fluid locked condition.
Next, when a selection valve connects the front supply/discharge path
118
to the fluid source and connects the rear supply/discharge path
119
to the tank, fluid at the set pressure at the fluid source side is supplied from the front supply/discharge path
118
via the second connection passageway
136
to the other-side cylinder subchamber
122
, so that the pressure intensifying piston
123
is moved forward by the fluid pressure.
When this occurs, because the surface area of other side of the pressure intensifying piston
123
that receives the fluid pressure within the other-side pressure intensifying cylinder subchamber
122
(total surface area of the cylindrical portion
124
and the disc member
125
) is quite a bit larger than the surface area of on the other side of the pressure intensifying piston
123
that receives the fluid pressure within the first pressure intensifying cylinder subchamber
120
(surface area of the cylindrical portion
124
), the fluid within the first pressure intensifying cy
Lin Kuang Y.
Nambu Co., Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Tran Len
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