Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to valves, and more particularly to over-
range valves or the like to protect structures from excessive pressures.
Overrange valves are employed in conventional differential pressure
units. Examples of the same are disclosed in the following:
Jones United States Patent No. 2,664,749 issued January 5, 1954.
Greenwood et al United States Patent No. 3,820,755 issued June 28,
1974.
Neither of the said Jones and Greenwood et al. disclosures have
the best construction to prevent overrange valves from sticking or, locking
closed. However, Greenwood et al. discloses a tiltable poppet valve.
In accordance with the valve of the present invention, the above-
described and other disadvantages of the prior art are overcome by providing
a fluid pressure responsive apparatus, said apparatus comprising: a mounting
ring assembly; first and second bellows each having an open end and a closed
end, said open ends being sealed around respective opposite sides of said
mounting ring assembly; first and second disc-like planar springs, said first
spring being fixed at its periphery to one side of said mounting ring assembly,
said second spring being fixed at its periphery to the other side of said
mounting ring assembly, each of said springs having a pair of spiral slots of
polar symmetry; a first stem having one end fixed to the center of said first
spring and another end fixed to the center of said first bellows closed end;
a second stem having one end fixed to said second spring and another end fixed
to the center of said second bellows closed end, the centers of said first
and second springs being fixed relative to each other, said first and second
springs biasing both of said first and second bellows against a differential
pressure thereacross and guiding the same and said first and second stems and
limiting movement of said first and second stems and said bellows approximate-
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ly to an axial direction; and a housing around each of said bellows to admit
fluids of the same or different pressures to the respective exteriors of each
of said bellows.
A feature of the invention resides in the use of a vented seal to
prevent lock-up.
In the accompanying drawings which illustrate exemplary embodiments
of the present invention:
Figure 1 is a longitudinal sectional view of a differential pressure
unit (DPU) constructed in accordance with the present invention;
Figure 2 is an enlarged longitudinal sectional view of a portion of
the DPU shown in Figure l;
Figure 3 is a front elevational view of parts shown in Figures 1 and
2;
Figure 4 is a vertical sectional view of the parts taken on the line
4-4 shown in Figure 3; and
Figure 5 is a broken away, exploded perspective view illustrating
the manner in which spiral springs are mounted in Figure 1.
The DPU shown in Figure 1 may be conventional except for arrangements
10 and 11 providing overrange valves, and spiral springs 12 and 13 which may be
identical to each other and to spiral spring 14 shown in Figure 5.
The DPU assembly is held together by cap screws 15 and 16, the
outer portions of the DPU including hat-shaped sections 17 and 18. Hat-shaped
sections 17 and 18 have two openings thereinto, only one of which is shown at
19 in Figure 1. See also the said Jones patent.
Sections 17 and 18 provide chambers 19 and 20 in which bellows 21
and 22 are mounted.
A stem 23 extends through most of the interior of the DPU, and all
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parts thereto are substantially fixed relative to each other. part 24 is fixed
relative to the right end of bellows 22, and is threaded to part 25. A central
part 26 is threaded inside parts 27 and 25. Part 27 is threaded inside part
28.
The DPU has a central portion 29 sealed to portions 30 and 31 to
which sections 17 and 18 are sealed respectively.
Seals are indica~ed at 32, 32', 33, and 33'. An arm 34 rotates a
torque tube 35 responsive to reciprocation of stem 23, the operation of which
and construction of which may be identical to those shown in the said Jones
patent.
Due to the fact that arrangement 10 is essentially the same as an
arrangement 11, although arrangements 10 and 11 are reversed, only arrangement
11 will be described in greater detail. An enlarged view of arrangement 11 is
shown in Pigure 2. An elastomer s~ch as rubber at 37 is bonded to a disc 38.
Elastomer 37 is pressed against a fixed surface of an annular valve seat 36
(Pigures 1 and 2) by a plate 39 welded or sealed at 40 to hub part 25.
Note will be taken that surface 36 lies in a plane substantially
transverse to the longitudinal axis of the DPU in Eigure 1 and is annular.
As shown in Figure 2, a snap ring 41 is substantially fixed in a
groove 42 in part 25. When elastomer 37 is spaced from surface 36 as in Figure
1, note will be taken that disc 38 can move in a radial or in an axial direction
or can tilt. This makes it possible for a good seal to be provided by elasto-
mer 37 between surface 36 and the right hand surface of plate 39.
In Figure 2, note that space is provided at A so that the fit of
disc 38 is somewhat loose.
Disc 38 and elastomer 37 are shown again in Figures 3 and 4 to a
scale substantially the same as that to which the~ have been shown in Figure 1.
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In Figure 3, note that disc 38 has 3 holes 43 extending completely
therethrough. As shown in Figure 2, holes 43 permit the escape and ingress of
an incompressible liquid respectively from and to the space between dics 38 and
plate 39. Note will be taken that without holes 43, if the said spaces are
sealed, stem 23 may stick with the valve of one of the arrangements 10 or ll
closed.
Spring 14 shown in Figure 5 may be entirely conventional, if desired.
Screw holes are indicated at 44. Spring 13 would fit in DPU portion 31 in the
same manner that spring 14 would and as shown in Figure 5. Spring 12 would be
similarly mounted in DPU portion 30.
Cap screws 52 and 53 in Figures 1 and 5 are typical.
In Figure l, chambers 19 and Z0 are essentially cylindrical having
an axis the same as that of stem 23.
Bellows 21 and 22 may be old in the art. For example, see the
bellows in British Patent No. 1 356,783.
A single spiral spring such as spring 14 in a differential pressure
unit is old in the art. See for example, spring 76 in Figure 3 of British
Patent No. 843,144.
In Figure l, 19' and 19" are threaded ports allowing fluid to enter
and to fill chambers 19 and 20.
Stem 23 has parts 24, 25, 26, 27 and 28. Springs 12 and 13 are
substantially identical to spring 14 shown in Figure 5. Parts 24 and 25 are
fixed relative to spring 13. Parts 27 and 28 are fixed relative to spring 12.
A typical countersunk screw is provided at 54.
OPERATION
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The mode of operation of the device is as follows:
If the pressure inside section 17 an~ outside bellows 21 exceeds that
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in section 18 but outside bellows 22, stem 23 moves to the right and turns
torque tube 35 clockwise. If the differential pressure is large enough, elasto-
mer 51 seals against shoulder 50 ~Figure 1) and keeps excessive pressure inside
and outside the bellows 21 from bursting bellows 22.
Conversely, excess pressure within section 18 will not burst bellows
21 because elastomer 37 will seal with surface 36 (Figures 1 and 2).
Otherwise, without elastomers 37 or 51 sealing, torque tube 35 is
rotated an amount proportional to the difference between the pressures in
sections 17 and 18.
When the pressure in chamber 20 is higher than that in chamber 19,
torque tube 35 is rotated in a counterclockwise direction.
The differential pressure unit CDPU) of Figure 1 may be described
as "apparatus." Central portion 29 and portions 30 and 31 may be described
as a mounting ring assembly. Bellows 21 has an open end 55 and a closed end 56.
Similarly, bellows 22 has an open end 57 and a closed end 58. Discs 55 and
57 are sealed at 59 and 60, respectively, and have openings 61 and 62.
Springs 12, 13 and 14 all are disc-like planar springs fixed in the
manner shown in Figure 5 to portion 31.
Springs 12, 13 and 14 may be entirely conventional, if desired. All
three may have a pair of spiral slots of a polar symmetry. The same type of
slots are shown in Figure 5.
