PRESSURE COMPENSATING DEVICE

COMPENSATEUR DE PRESSION

English Abstract

ABSTRACT


The present invention provides a pressure compensating device through which two
separate fluid streams flow separated by a diaphragm. The flow of fluid on one
side if the diaphragm is unimpeded whilst flow on the other side of the diaphragm
is controlled as a result of movement of the diaphragm caused by pressure
differentials.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A pressure compensating apparatus comprising a vessel body
defining two chambers separated by a diaphragm, an inlet
an outlet for each of the two chambers, the first of said
chambers including valving means for controlling the entry
of fluid into the chamber the second chamber allowing the
free passage of fluid therethrough, the inlet to said
first chamber incorporating a valve opening which is
aligned with a removable cap providing access to the valve
opening and incorporating a valve seat, a floating valve
head positioned over said valve seat said floating valve
head being constrained by a bridge which straddles the
inlet to the first chamber and which is connected to said
diaphragm, movement of the diaphragm controlling the
closure of the valve head on the valve seat and the flow
of fluid through said first chamber such movement
occurring when a pressure differential exists between the
first and second chambers.

2. A pressure compensating device as claimed in claim 1,
including pressure relief means providing a venting path
across the diaphragm in the event that pressure in the
first chamber exceeds a predetermined level, and, wherein
said bridge is attached to the diaphragm by a pin or bolt
and the venting path is provided between the sides of the
pin or bolt and an aperture in the diaphragm through which
the pin or bolt passes, access to the venting path under
normal conditions being blocked by a washer mounted on the
pin or bolt the opening of said pressure relief means
being controlled by a spring which retains the diaphragm
in a closed position under normal conditions.

-8-

Description

lZ9~756


This inver- tion relates to pressure compensating devices.

In general diapllragm operated pressure regulators are well known and used in many
diFferent applications. Tllere are however some as yet unsolved difficulties with
respect to systems dealing with two fluid streams at significantly different
pressures where these are delivered via a common outlet. An example of the
problem is perhaps in water supplies where it is common for hot water pressures to
be significantly lower than the mains cold water pressures. This is mast noticeable
when a householder takes a shower and when another applicance or tap is turned on
there is a most disconcerting change to water temperature delivered from the
shower rose.

There is also available on the market today a range of sophisticated tapware where
tlle tap is in fact a water mixer. Unfortunately these taps cannot operate in the
manner for which they are designed unless the water delivered from the hot and
cold systerns is at substantially equal pressures.

lt is an object of the present invention to provide a pressure compensating device
which addresses the aforementioned problems and which may have a broader
general application.

Further objects and advantages of the present invention will become apparent from
the ensuing description which is given by way of example.

According to tlle broadest aspect of the present invention there is provided a
method of controlling pressures between two fluid streams delivering fluid to a
common outlet the method comprising the steps of causing the two fluid streams to
pass throuyh a common vessel where the streams are separated by a flexible
member and controlling the entry of one of the fluid streams into the vessel on at
least one side of the flexible member using valvlng means which are operatively
connected to the flexible member so that the pressure on the controlled side of the
flexible member Is substantially equal to the pressure on the other side thereof.

lZ98'7S6


According to a furtl er aspect of the present invention an apparatus for performing
the aforementioned method comprises a vessel body defining two chambers
separated by a flexible mernber an inlet and outlet for each of the two chambers,
at least a first of said chambers including valving means for controlling the entry
of fluid into the vessel, said valving means being operatively connected to the
flexible member and adapted to operate said valving means to control the ingressof fluid into the first chamber when a pressure differential exists between the first
chamber on one side of the flexible member and the second chamber on the other
side of the flexible member.

Aspects of the present invention will now be described by way of example only with
reference to the accompanying drawings in which:
iqure 1: is a top view of a pressure compensating device in accordance with
one possible embodiment of the present invention, and
~ure 2: i8 an end view of the pressure compensating device of figure 1, and
iqure 3: is a section through ttle pressure compensating device of figure 1, and
iqure 4: is an exploded view showing the relationship of the components of the
pressure compensating device of figures 1.

With respect to the drawings the pressure compensating device comprises a body
generaJly indicated by arrow 1 which i8 split into two halves 2, 3 about a flange 4.
The flange 4 captures a diaphragm generally indicated by arrow 5 (figures 3 and 4)
which separates the interiors of the body into a first chamber 6 and a second
chamber 7. The first chamber is provided with an inlet 8 and an axially aligned
outlet 9. The second chamber 7 i8 likewise provided with an inlet lU and an outlet
11. The first chamber is provided with a screw theaded cap 12 which engages witha threaded opening 13 in the top of the body 1. An o-ring seal 14 ts located in a
recess in the mouth of the threaded opening to provlde a fluid tlght seal. The ends
of the inlets 8 and 10 and the outlets 9 and 11 are threaded.

--3--




.

'

lZ98756


The pressure compensating device is designed to be installed in a situation where
two pipes feed a single appliance. If the pressure compensating device is used to
control uneven pressures in a shower system in a dwelling the device is positioned
adjacent to the shower mixer valve. The higher pressure pipe (usually the cold
water pipe) is connected to the inlet 8 and the lower pressure pipe (usually the hot
water pipe) is connected to the inlet 10. The outlets 9 and 11 are connected to the
shower mixer unit (not shown).

The two halves 2 and 3 of the body 1 are fastened together by a series of bolts or
screws 15 so that an outer flange 16 of the diaphragm 5 locates in complementarygrooves 17 of the flange 4.

Apart from the intrusion of the diaphragm 5 the flow of low pressure fluid through
the second chamber 7 is unimpeded. The inlet 8 of the half section 2 of the body 1
intrudes into the first chamber where a throttling valve generally indicated by
arrow 19 is positioned.

The throttling valve 19 comprises a valve seat 20 mounted on the inner end of the
Inlet 8, a valve head 22, the valve 19 being operatively connected to the diaphragm
5 via a bridge generally indicated by arrow 23.

The valve seat 20 is a T-section member having a threaded part 24 which engages
in a complementary thread of the inlet 8. An o-ring seal 26 is used to prevent
leakage via the common thread.

'The bridge 23 comprises a U-shaped section 27 fixed to the diaphragm 5 and 8
removable strap 28 which engages in complementary apertures 29 at the upper endsof the U-sl-aped section 27 of the bridge 23.

~ assembly of the device the upper end of the bridge 23 and thetvalve head 22 are
accommodated within the cap 12 with the star shaped valve head 22 a loose fit
within the cap 12 and being positioned above the valve seat 20. The valve head 22

1298756

is restrained ct~-axially in its position above the valve seat 20 by the internal bore
of cap 12 with the limbs of the U-shaped section 27 fitting between adjacent legs
30 of the valve head 22. In the example illustrated the valve head 22 is provided
with an inbuilt washer 31. The axial travel of the valve head 22 relative to thevalve seat 20 is limited by the strap 28. The diaphragm 5 which can be moulded in
any suitable durable flexible material such as rubber, nylon or plastics i5 protected
by cup-shaped plates 32 and as aforesaid is connected to the throttling valve 19 by
the U-shaped section 27 of the bridge 23, the means of connection being a pin 33.
The pin 33 passes through the base of the U-shaped section 27 and into an aperture
34 in a T-section sleeve 35 with a flange 36 of the sleeve 35 being secured by the
inner edges 37 of the cup-shaped plates 32 there being in addition an o-ring seal 3B
between the sleeve 35 and the undersurface of the U-shaped section 27 of the
bridge 23. A passage is provided between the sleeve 35 and the portion of the pin
33 passing through it. Pin 33 is provided with a nut 40 which tightens on a discspring 42 and the o-ring seal 38 is held firmly against the under surfaces of the U-
stlaped r,ection 27. A Deal 43 is provided at the top end of the pin 33.

Mentioned earlier was the application of the present device to hot and cold water
pipes at unequal pressures feeding common appliances such as a shower mixer/roseor a mixer/tap. In this situation cold water at high pressure is fed into the first
chamber 6 and hot water at low pressure into the second chamber 7. If at the
shower mixer/rose or mJxer/tap there is a demand for hot water only the water
flows unimpeded through the second chamber 7 slightly reducing pressure in the
first chamber 6 with the higher pressures in the first chamber 6 and diaphragm
movement holding ths valve head 22 on the valve seat 20. If on the other hand cold
water is exclusively drawn by the appliance the valve will open to compensate for a
pressure drop within the first chamber 6 and cold water will be delivered as
required at substantially the same pressure as the hot water in chamber 7.

Where there is a requirement for hot and cold water to be delivered in equal or
unequal volumes the throttling valve 19 operates to compensate for unequal waterpressures. If for example the appliance was drawing one gallon of hot water per

_5--

`` i298756


two gallons of cold there is a greater loss of pressure in the first chamber 6 than in
the second chamber 7 and the throttling valve 19 opens in proportion to the
volumetric flow ratios to compensate for the lower pressures. Because this happens
automatically water is delivered to the mixer at substantially equalised pressure. If
you take the other example of there being a greater demand for hot water at low
pressure than cold at a higher pressure then the valve 19 only opens to the extent
that is determined by the drop in pressure in the second chamber containing the hot
waLer.

During normal operating conditions the device may have pressure differentials inthe orcler of 15kpa to 6U kpa depending on the inlet pressure of the cold water. If
some foreign matter should become trapped between the valve head 22 and the
valve seat 20 so that cold water was not stopped completely when an associated
appliance 15 was turned off the pressure in the first chamber would continue to
rise. This would exert excessive forces on the moving parts of the device and
diaphragm rupture may occur. To limit the pressure differential to a predetermined
maximum value of say 80kpa a relief valve is incorporated in the device. In
accordance with the example illustrated the relief valve is embodied in the means
by which the diaphragm 5 is connected to the bridge 23. Excessive pressures in the
first chamber 6 will cause the diaphragm 5 and thus the o-ring seal 3~ to move
away from the U-shaped section 27 of the bridge 23 to allow for fluid to pass down
the passage 39 into the second chamber 7. Any excess of water in the second
chamber 7 can be discharged through the hot water systems pressure relief vent
such discharge from the relief system giving a visual indication of a fault.

Back flow through the device can be protected against either by provlding a biasing
spring (not shown) to the valve head 22 or by the provision of a non-return valve 44
in the outlet 11.

The pressure relief valve is designed to fit within a 75mm wall frame and the valve
is mounted so that the cap Is accessable from ths most convenient side in the event
maintenance is required.

--6--

12987~i6


Whilst the valve has been described in relation to hot and cold water systems and
two specific applicances which feed off hot and cold water it is to be appreciated
that the valve could be used in other applications.

Aspects of the present invention have been described by way of example only and
modifications and additions thereto may be made without departing from the scopeof the invention as defined in the appended claims.




--7--

Representative Drawing