Pipes and tubular conduits – With pressure compensators – Variable capacity chambers
Reexamination Certificate
2001-05-29
2004-09-14
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
With pressure compensators
Variable capacity chambers
C138S031000, C220S721000, C303S087000
Reexamination Certificate
active
06789576
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an accumulator used for, for example, hydraulic circuits in hydraulic control apparatuses, specifically relates to a securing structure for hydraulic ports with respect to sealed vessels (shells) for hydraulic fluids and gases, and relates to a protecting structure for a partitioning member installed therein.
2. Background Art
The accumulator such as the above generally comprises a cylindrical shell partitioned into a gas chamber and a hydraulic chamber by a bellows. The pressure variation of the hydraulic fluid flowing into the hydraulic vessel is accommodated by the expansion and compression of the gas in the gas chamber according to the elastic motion of the bellows. The accumulator is widely used in devices such as a hydraulic circuit in automobiles for effectively inhibiting pulsation in the hydraulic fluid flowing therein.
In
FIG. 5
, an example of a conventional accumulator is shown, and reference numeral
80
is a cylindrical shell which forms a sealed vessel by joining a bottom shell
81
and a cap shell
82
. Reference numeral
83
is a metallic bellows assembly partitioning the interior of the shell
80
into a hydraulic chamber
91
and a gas chamber
92
. Reference numeral
93
is a port comprising a flow path
93
a
for communicating a hydraulic circuit (not shown) and the hydraulic chamber
91
. The bellows assembly
83
forms the hydraulic chamber
91
therein, and comprises bellows
84
elastically moving in the axial direction of the shell
80
, and a bottom seal
85
and a bellows cap
86
joined to both ends of the bellows
84
. The bottom seal
85
is joined to the cap shell
82
.
The bellows cap
86
is a free end of the bellows assembly
83
. The circumference of the bellows cap
86
is mounted with a circular bellows guide
87
which slides with the inner surface of the shell
80
so as to guide the elastic movement of the bellows
84
in the axial direction.
The axial length of the bottom shell
81
is longer than that of the cap shell
82
. The joining portion of the shells
81
and
82
approximately faces the bellows
84
even if the bellows
84
is in the most contracted condition.
In such an accumulator, when the hydraulic fluid flows into the hydraulic chamber
91
via the flow path
93
a and the pressure of the hydraulic fluid exceeds the gas pressure in the gas chamber
92
, the bellows
84
expands, and the gas in the gas chamber
92
is compressed. In contrast, when the hydraulic fluid pressure in the hydraulic chamber
91
is below the gas pressure in the gas chamber
92
, the bellows
84
is contracted and the gas in the gas chamber
92
is expanded. Due to the expansion and compression of the gas in the gas chamber
92
, the variation of the pressure of the hydraulic fluid in the hydraulic circuit is accommodated and pulsation thereof is inhibited. The two-dot chain line in
FIG. 5
shows the position of the bellows cap
73
when the bellows assembly
70
is in the most expanded condition.
The port
93
in the conventional accumulator is joined to the cap shell
82
by projection welding, or the like, which is one type of resistance welding. Welding produces sparks in some cases, and splashed material adheres to the inner surface of the port
93
and the cap shell
82
, thereby contaminating therein. When the accumulator is assembled with the contamination, the hydraulic fluid is contaminated and results in malfunctioning of the accumulator. Although cleaning is performed to remove the contamination, it is difficult to completely remove the contamination since there are portions where the cleaning is not easily performed. Furthermore, the cleaning is labor intensive, and the production efficiency is decreased.
In assembly of the conventional accumulator, the bottom shell
81
is welded to the cap shell
82
after joining the bellows assembly
83
to cap shell
82
by welding. Similarly in this case, when the shells
81
and
82
are welded by projection welding, sparks are emitted to the interior of the shell
80
, and the bellows
84
may be damaged. Although the service life of the bellows is shortened when the bellows
84
is damaged, it cannot be ascertained whether the bellows
84
is damaged since it is contained in the shell
80
, and the normal operation of the accumulator cannot be ensured.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an accumulator in which contamination of the interior thereof due to sparks emitted in welding a port can be inhibited and the production efficiency can be improved.
Another object of the invention is to provide an accumulator in which damage to a bellows due to sparks emitted in welding shells can be inhibited and the normal operation of the accumulator in over the long term can be ensured.
The present invention provides an accumulator comprising: a cylindrical shell including a cylindrical portion; a partitioning member for partitioning the interior of the shell into a hydraulic chamber and a gas chamber; and a port including a hydraulic fluid flow path for communicating the exterior of the shell and the hydraulic chamber. Variation of pressure of a hydraulic fluid flowing into the hydraulic chamber is accommodated by expansion and compression of a gas in the gas chamber according to expansion and contraction of the partitioning member. The port is approximately airtightly inserted into the cylindrical portion of the shell, and is welded to an outer circumference of the cylindrical portion by means of welding.
According to the invention, the port is approximately airtightly press fitted into the cylindrical portion of the shell, and the inner surface of the cylindrical portion and the outer surface of the port are closely contacted to each other. Therefore, the outer ridge portion of the cylindrical portion is isolated from the interior of the shell. As a result, when sparks occur during welding, the sparks are not emitted into the interior of the shell, and the interior of the shell is not contaminated by splashing of the sparks. Therefore, the contamination in the shell can be easily controlled and the production efficiency can be improved. Furthermore, even if sparks are emitted in the shell the sparks remain in the gas chamber and do not enter into the hydraulic chamber, so that the system including the hydraulic circuit to which the accumulator is connected is not contaminated by splashing of the sparks.
According to the preferable feature of the invention, in which the overall length of the accumulator can be shortened, the cylindrical portion is projected into the interior of the shell. Several kinds of forming method can be applied to the feature, but burring in which a through hole is formed in the shell and a punch having larger diameter than that of the through hole is press fitted thereinto is preferable.
The partitioning member may comprise a fixed portion and a movable portion mounted to the fixed portion via an elastic member, which corresponds to the bellows assembly
83
in the conventional accumulator in FIG.
5
. The fixed portion, the elastic member, and the movable portion correspond to the bottom seal, the bellows, and the bellows cap respectively. It is preferable feature that the fixed portion is integrally formed with the port. Heretofore, the fixed portion (bottom seal) has been joined to the inner surface of the cap shell, so that sparks occurring in welding results in problems of contamination similarly in the port. However, by integrating the fixed portion with the port, the fixed portion needs not to be welded to the cap shell, and the problems due to the sparks can be solved.
According to another preferable feature of the invention, the shell comprises plural divided shell bodies joined to each other. The partitioning member includes a guide for sliding on an inner surface of the shell so as to guide the expansion and contraction of the partitioning member along an axial direction thereof. The joined portion between the divided shell bodies is position
Mizukami Hiroshi
Nakamura Koji
Umetsu Chiharu
Yamada Koichiro
Arent & Fox PLLC
Brinson Patrick
NHK Spring Co., Ltd
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