Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1999-07-19
2001-11-27
Larkin, Daniel S. (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
Reexamination Certificate
active
06321590
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a leakage measuring device for measuring a leakage rate of a circuit or the like which constitutes a measuring object.
2. Description of the Prior Art
As a measuring device for the above purpose, a measuring device shown in
FIG. 6
has been known conventionally.
This conventional measuring device incorporates a piston
2
in a cylinder
1
slidably and divides the inside of the cylinder
1
into one pressure chamber
3
and the other pressure chamber
4
.
A piston rod
5
is mounted on a side surface of the piston
2
which faces the other pressure chamber
4
and this piston rod
5
is protruded outwardly from the cylinder
1
.
A rack member
6
is provided to a distal end of the piston rod
5
and a rack
6
a
formed on the rack member
6
is meshed with a pinion
8
of an encoder
7
. Accordingly, when the piston
2
is moved, the pinion
8
is rotated and a digital signal in response to the movement of the piston
2
is outputted from the encoder
7
.
In the drawing, numeral
9
indicates a seal member provided around the periphery of the piston
2
for preventing a leakage between both chambers
3
,
4
, while numeral
10
indicates a seal member for sealing the periphery of the piston rod
5
.
In an actual use of the measuring device having the above-mentioned construction, for example, one pressure chamber
3
is connected to a pressurizer not shown in the drawing and the other chamber is connected to a circuit or the like which constitutes a measuring object or an object to be measured.
When pressure is applied to one pressure chamber
3
, if there is no leakage at the measuring object side, the piston
2
is not moved. However, if there is a leakage at the measuring object side, the piston
2
is moved. Accordingly, the movement of the piston
2
is proportional to the leakage at the measuring object side. Then, the movement of the piston
2
is measured by the encoder
7
so as to measure the leakage at the measuring object side.
In case the leakage rate at the measuring object side is zero and the piston
2
is stopped at a fixed position, the pressure generated in the other pressure chamber
4
is higher than the pressure generated in one pressure chamber
3
. It is because that the pressure receiving area of the piston
2
in the other pressure chamber
4
is smaller than the pressure receiving area of the piston
2
in one pressure chamber
3
by the cross-sectional area of the piston rod
5
.
Because of the presence of the pressure difference between these pressure chambers
3
,
4
, the measuring device must be provided with the seal member
9
around the periphery of the piston
2
. It is because that the greater the pressure difference between these chambers
3
,
4
, the leakage from the high pressure side to the low pressure side is increased.
Furthermore, in proportion to the increase of the pressure in the other pressure chamber
4
, the necessity of the seal member
10
is increased.
Besides the measuring device shown in
FIG. 6
, a measuring device shown in
FIG. 7
has been also known conventionally.
The measuring device shown in
FIG. 7
incorporates a piston
12
in a large diameter cylinder
11
and defines a pressurizing chamber
13
. Air pressure is introduced into this pressuring chamber
13
by means of a pressurizer not shown in the drawing.
A plunger
14
is provided to a side surface of the piston
12
which is opposite to the pressurizing chamber
13
. The plunger
14
has a distal portion thereof slidably incorporated in a small diameter cylinder
15
which is formed contiguously with the large diameter cylinder
11
. A measuring pressure chamber
16
formed in the small diameter cylinder
15
is connected with a circuit which constitutes a measuring object.
The piston
12
is provided with a scale indication rod
17
and this scale indication rod
17
is protruded outwardly from the large diameter cylinder
11
in parallel with the small diameter cylinder
15
. On the outside of the small diameter cylinder
15
, a scale
18
is marked and this scale
18
and the scale indication rod
17
face with each other in an opposing manner as shown in the drawing.
In the drawing, numeral
19
indicates a drain chamber and numerals
20
,
21
indicate seal members.
The measuring device having the above-mentioned construction adopts an operation principle similar to that of the measuring device shown in FIG.
6
. Namely, when air pressure is supplied to the pressurizing chamber
13
, the piston
12
is stopped at a position where the piston
12
is balanced with a pressure action of the measuring pressure chamber
16
. Then, when an oil leakage occurs at the circuit side which constitutes the measuring object, the piston
12
is moved and this movement can be inspected visually in view of the correspondence between the scale indication rod
17
and the scale
18
. Based on the movement of the piston
12
detected in this manner, the leakage at the measuring object side can be measured.
The measuring device shown in
FIG. 6
has following problems.
Namely, as the pressure difference between both pressure chambers
3
,
4
becomes large, the leakage from the other pressure chamber
4
which is at a high pressure to one pressure chamber
3
which is at a low pressure occurs.
When the leakage occurs between both pressure chambers
3
,
4
, it becomes difficult to determine whether the movement of the piston
2
is caused by a leakage at the measuring object side or the internal leakage of the measuring device per se. Accordingly, the leakage at the measuring object side cannot be measured accurately.
As means for preventing such a leakage, it is considered to increase an interference of the seal member
9
. When the interference of the seal member
9
is increased, however, the piston
2
cannot enjoy the smooth movement and a so-called stick-slip phenomenon occurs. Accordingly, the measured value outputted from the measuring device is vigorously fluctuated resulting in the inaccurate measurement of the leakage.
Furthermore, even in case the interference is not increased, the seal members
9
,
10
are deformed when they are respectively subjected to a high pressure and hence, the friction of the seal members
9
,
10
is increased. In this manner, in case the friction of the seal members
9
,
10
is increased during the measuring process, the relative relation between the pressure action of one pressure chamber
3
and the movement of the piston
2
cannot be fixed. In this case, the leakage cannot be measured accurately also.
The measuring device shown in
FIG. 7
also has a problem that it cannot avoid adverse effects caused by the seal members
20
,
21
and it is considerably difficult to inspect the movement of the piston
12
visually.
In any case, the above-mentioned conventional measuring devices have a problem that it cannot measure the leakage easily and accurately due to the interaction among various factors.
Accordingly, it is an object of the present invention to provide a leakage measuring device capable of always performing the accurate measurement of the leakage.
SUMMARY OF THE INVENTION
The present invention is based on a leakage measuring device which is constructed such that a cylinder has an inside thereof divided into one pressure chamber and the other pressure chamber by a piston rod mounted in the cylinder, one pressure chamber is connected with a pressurizer and the other pressure chamber is connected with a circuit or the like which constitutes a measuring object, and based on the movement of the piston when one pressure chamber is pressurized, a leakage of the circuit or the like which constitutes the measuring object is measured.
Based on the above measuring device, a first aspect of the present invention is characterized in that pressure receiving areas of the piston in both pressure chambers are made equal to each other, and a detection rod which is fixedly secured to the cylinder side is inserted into a detection hole formed along an ax
Garber C D
Kayaba Industry Co. Ltd.
Larkin Daniel S.
Steinberg & Raskin, P.C.
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