Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
1999-02-26
2001-03-06
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
C242S584100, C072S148000
Reexamination Certificate
active
06195867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing a spiral wound gasket for sealing fluid such as liquid including water and oil, and a gaseous body including vapor and gas.
Also, the present invention relates to a device for producing the spiral wound gasket.
2. Description of the Prior Art
In a joint portion of each laying pipe employed under a high temperature and a high pressure condition, a gasket is disposed between a pair of flanges, each flange is fastened by a bolt, and the gasket is closely fitted in each flange, thereby preventing a fluid flowing inside the pipe from leaking to the outside.
For the gasket, a spiral wound gasket is usually employed. As shown in
FIGS. 9 and 10
, the spiral wound gasket has a structure wherein a filler material
92
made of an asbestos paper, an expanded graphite tape, a 4-fluorinated ethylene resin tape, or the like is stuck on a hoop material
91
made of a long and thin stainless plate having a wave shaped or chevron shaped section so that they may be wound in a spiral state.
A general method of producing this spiral wound gasket is described below.
First, as shown in
FIG. 11
, the tip portion of the hoop material
91
is folded and inserted in a checking groove
93
a
of the outer periphery of a core drum
93
, whereby the hoop material
91
is stopped by connecting it to the core drum
93
. In this state, the core drum
93
is rotated so that only the hoop material
91
is wound around the outer periphery of the core drum
93
at least once. Then, the filler material
92
is stuck on the hoop material
91
so as to be wound in a spiral state. Thereafter, only the hoop material
91
is further wound two or three times. Moreover, the hoop material
91
and the filler material
92
wound
16
in a spiral state are removed from the core drum
93
, thereby cutting off the folded area on the tip portion of the hoop material
91
, which is inserted in the checking groove
93
a
of the core drum
93
.
An initial portion of the hoop material
91
to be wound is fixed in a predetermined zone of the hoop material
91
by spot welding or the like. A last portion of the hoop material
91
to be wound is fixed in a predetermined zone of the preceding-round of the wound hoop material
91
by the welding spot or the like.
However, the conventional producing method mentioned above requires that the hoop material
91
and the filler material
92
wound in a spiral state are removed from the core drum
93
, before positioning a step for cutting off the tip portion of the hoop material
91
inserted in the checking groove
93
a
of the core drum
93
. Consequently, the number of steps is increased, and it is required to manually perform a cutting operation, thereby incurring an expensive production cost. Moreover, the cut-off portion of the hoop material
91
has to be wasted, which results in a problem wherein a yield of the hoop material
91
is worse.
In order to overcome the above problems, a method shown in
FIG. 12
is proposed as below. A pressing force is applied to the tip portion of the hoop material
91
, thereby forming a flat portion
91
a
. A checking hole
91
b
is formed on the flat portion
91
a
by piercing the hoop material. On the other hand, the core drum
93
is provided with a checking pin
94
whose tip can protrude or retract elastically from the outer periphery of the core drum
93
. The checking pin
94
catches the checking hole
91
b
of the hoop material
91
, thus permitting winding the hoop material
91
around the core drum
93
. (See the gazette of Japanese Patent Publication No. H8-33180.)
According to the method, the step of cutting off the tip portion of the hoop material
91
is not required. However, it is required to form the flat portion
91
a
for providing the checking hole
91
b
by a step of applying pressure or the like to the tip portion. A width of the tip portion after forming the flat portion
91
a
, is greater than the reminder of the portion thereof, whereby local unevenness is generated on the sealing surface of the completed gasket owing to a shape of the tip portion thereof. As a result, there is a fear wherein the unevenness adversely affects the sealing property.
Furthermore, a great gap is generated between the flat portion
91
a
and the chevron portions
91
c
,
91
c
of a second-round hoop material
91
wound around the outer periphery thereof, whereby welding the flat portion
91
a
to the hoop material
91
on the outer periphery thereof is not ensured, thereby, in some cases, causing a problem wherein it is easy to separate the flat portion
91
a
therefrom.
In addition, though the second-round hoop material
91
directly wound around the outer periphery thereof unforcedly presses the checking pin
94
to move downwardly, the operation of winding the first-round hoop material
91
is not fully completed at the time when the checking pin
94
is pressed to move downwardly. Moreover, the hoop material
91
is intensively drawn, thereby increasing the contact pressure between the checking pin
94
and the checking hole
91
b
. In some cases, the unforced friction between the tip portion thereof and the checking hole
91
b
greatly damages the tip portion of the checking pin
94
, when the checking pin
94
is pressed to move downwardly, with the result that there are problems wherein the durability of the device is bad and the operation of replacing the checking pin
94
is required.
SUMMARY OF THE INVENTION
The present invention from a consideration of the above circumstances.
An object of the present invention is to provide a method of producing a spiral wound gasket for ensuring excellent sealing property and a device for producing the same.
Another object of the present invention is to provide a method of producing a spiral wound gasket wherein there is no fear that a tip portion of a hoop material is separated from an outer periphery of the hoop material, and to a device for producing the same.
A further object of the present invention is to provide a method of producing a spiral wound gasket which is excellent in durability, and a device for producing the same.
In order to achieve the noted objects, a method of producing a spiral wound gasket of the present invention, wherein a tip portion of a hoop material having a chevron or wave shaped section is stopped by connecting it to a core drum for winding the hoop material, the core drum being rotated so as to wind the hoop material around an outer periphery of the core drum at least once, thereby overlapping a filler material onto the hoop material so that both of them are wound in a spiral state, comprises the steps of:
forming a checking stepped-portion by cutting and raising a chevron portion of the tip portion of the hoop material or a valley portion thereof,
rotating the core drum in a state wherein the checking stepped-portion of the hoop material is caught by a checking pawl which makes the tip portion protrude from the outer periphery of the core drum, thereby winding the hoop material around the outer periphery of the core drum at least once,
overlapping the filler material onto the hoop material together so that both of them are wound in a spiral state,
retracting the checking pawl from the outer periphery of the core drum into the inner periphery of the core drum at a predetermined time after winding the hoop material around the outer periphery of the core drum at least once, thereby separating the checking pawl from the checking stepped-portion.
According to the method of producing the spiral wound gasket, the checking stepped-portion being caught by the checking pawl is formed by cutting and raising the chevron portion or the valley portion of the tip portion of the hoop material. Therefore, forming a flat portion on the tip portion of the hoop material is not required. This enables a width of the tip portion of the hoop material to correspond to the remaining portion thereof, thereby preventing local unevenness from being generated on the sealing surface of the g
Hashiguchi Hideto
Kato Shoji
Konaka Masao
Okada Keiji
Takaoka Masahiko
Blount Steven
Cuda Rosenbaum I
Jones Tullar & Cooper P.C.
Nippon Pillar Packing Co. Ltd.
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