Pipes and tubular conduits – With pressure compensators – Variable capacity chambers
Reexamination Certificate
2001-07-03
2004-02-10
Hook, James (Department: 3752)
Pipes and tubular conduits
With pressure compensators
Variable capacity chambers
Reexamination Certificate
active
06688335
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for preventing liquid hammer. More particularly, the present invention relates to a device for preventing water hammer or fluid hammer which may occur inside a water pipe, or in a fluid channel of a hydraulic apparatus or other water related apparatus.
2. Description of the Related Art
There have been several types of liquid hammer prevention device (arrestor) in conventional and popular style, for example known as “water hammer arrestor,” which effectively reduce liquid hammer occurring in a fluid channel such as inside a water pipe. The conventional liquid hammer prevention device may be roughly classified into two types, that is, an external attachment type connected at any intermediate position of the fluid channel, and a built-in type incorporated in an operation handle or the like which controls open/close of the fluid channel.
Further, the conventional liquid hammer prevention device may also be classified into other two groups, that is, an outer flange type in which an outer rim of a diaphragm is supported by an outer flange, and an inner flange type in which an outer rim of a diaphragm is supported by an inner flange. The fundamental structure of outer flange type of liquid hammer prevention device mentioned above, serving to effectively absorb and reduce the liquid hammer, is illustrated in FIG.
26
. There is a cylindrical form of elastic cushion K of which outer diameter D and height H are substantially identical with each other, incorporated in a casing K
0
of a liquid hammer prevention device
700
. There is a hat-shape of diaphragm C comprising a stretch portion C
1
and an outer rim C
2
, positioned at the exposed surface (i.e. not the surface being in touch with the casing K
0
) of the elastic cushion K. The outer rim C
2
is in contact with the upper surface of a flange C
3
and pressed down by the outer flange of the casing K
0
by means of caulking at around the caulking means
725
, thus the elastic cushion K is sealed. Further, the elastic cushion K incorporated in the casing K
0
is attached to a pipe P
1
via a mounting screw portion C
4
of the flange C
3
. As illustrated in
FIG. 27
, the diaphragm C is a hat-shape diaphragm having the stretch portion C
1
so that the stretch portion C
1
may follow the displacement of the elastic cushion K by a considerable large amount of L in the direction of the height H thereof, which occurs when the elastic cushion K receives a liquid hammer force P through a passage hole
701
and a certain volume of buffer space.
The reason for adopting the cylindrical shape for the liquid hammer prevention device
700
as above discussed is to secure more than a predetermined volume of the elastic cushion K in order to effectively serve the liquid hammer absorption function. To satisfy this requirement, it is necessary to provide the elastic cushion K with a predetermined hardness, and with the height allowing the compression displacement by a predetermined amount. In addition, since the liquid hammer prevention device
700
is in the cylindrical shape, the diaphragm C of the elastic cushion K may have the durability in order to prevent the exposed surface of the elastic cushion K from being hollowed due to liquid hammer force, and may also have the stretchability being able to follow the compression displacement of the elastic cushion K.
The above discussed elastic cushion K uses, as the material thereof, the elastic hollow spheres added type of silicone gel, comprising a silicone gel cushion K
1
as the essential material of the elastic cushion K, and elastic hollow spheres K
2
incorporated in the silicone gel cushion K
1
.
However, when the elastic hollow spheres added type of silicone gel discussed above repeatedly absorbs the liquid hammer force for a long period of time, the contact surface between the elastic hollow sphere K
2
and the silicone gel cushion K
1
would collapse or exfoliate, consequently it has been found that the long-term liquid hammer absorption effect cannot be guaranteed according to the above liquid hammer prevention device
700
. This is so-called “softening” of the elastic hollow sphere added type of silicone gel, which softens the elastic hollow sphere added type of silicone gel when an external forth exceeding the predetermined amount is continuously applied to that silicone gel.
This softening would spread even to portion where the displacement of the elastic hollow sphere added type of silicone gel becomes in contact with the casing K
0
due to liquid hammer force. Consequently, the softening would cause the so-called “bottom thrust” in which the liquid hammer absorption function cannot be guaranteed, thereby the pressure energy conversion efficiency would be seriously reduced due to decrease of modulus of impact resilience.
The bottom thrust has been supposed to occur because of the softening of the whole body of elastic cushion due to multiple-stage factor. First, because of continuous compression displacement of the elastic hollow spheres K
2
, there occurs the exfoliation of elastic hollow spheres K
2
out of the portion at which the silicone resin has been in contact with the elastic hollow spheres K
2
. Then, the exfoliation brings about the deterioration of external force transmission to the elastic hollow spheres K
2
, which eventually causes the softening of the whole body of the elastic cushion. Therefore, when using the silicone gel cushion K
1
, it has been necessary to secure the sufficient volume more than the predetermined amount, and the sufficient height allowing the compression displacement by the predetermined amount.
FIGS. 28 and 29
illustrate typical embodiments of the inner flange type of liquid hammer prevention device. A liquid hammer prevention device
800
of
FIG. 28
is attached to any intermediate position of piping by means of a branch connection. The liquid hammer prevention device
800
has a main body
803
of which thread portion
803
A is engaged with a thread portion
805
B of a mounting ring
805
, and the main body
803
is eventually led to a fluid channel through a passage hole
801
, by means of engagement of a thread portion
805
A of the mounting ring
805
with the fluid channel. A casing K
0
is attached to and covers the outer periphery of the mounting ring
805
by engagement of a thread portion
805
C of the mounting ring
805
with a thread portion
807
of the casing K
0
. There is formed an engagement groove
803
E at the space between the mounting ring
805
and a head
803
D of the main body
803
being inserted and placed inside the casing K
0
. A diaphragm C has an engagement protrusive portion C
1
formed at the opening of diaphragm C and inwardly protruding in the radius direction thereof, and this engagement protrusive portion C
1
is engaged with the engagement groove
803
E. Thus the diaphragm C partitions the space inside the casing K
0
into two areas, that is, an area S
801
led to the fluid channel via the passage hole
801
, and an area S
802
provided for an elastic cushion
809
incorporated in the casing K
0
. The tightness of sealing of fluid between the areas S
801
and S
802
is maintained by means of the engagement protrusive portion C
1
being caught toward the axis X by two elements, that is the head
803
D and the mounting ring
805
, on account of engagement of the thread portion
803
A with the thread portion
805
B.
Further,
FIG. 29
illustrates another type of liquid hammer prevention device
900
. This liquid hammer prevention device
900
is in a form of faucet handle, in which a water hammer arrestor unit is incorporated. In particular, the liquid hammer prevention device
900
is provided inside a handle
919
which controls open/close of a spindle
911
. The spindle
911
comprises a thread portion
911
A being engaged with an accepting female thread portion of a valve main body (not shown) and a valve element
913
positioned below. There is a passage hole
901
penetrating through the axis X of the spindle
9
Kobayashi Tatsuya
Suzuki Eiji
Hook James
McGinn & Gibb PLLC
Suzuki Sogyo Co., Ltd.
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