GB2348477A - Thermostatic float vent - Google Patents

Abstract

A thermostatic float vent consists of two valves. The first is a float type 2 which raises to shut off the escape of air once the radiator water level has risen sufficiently to close the float valve piston against the seating 5. The second, a heat - activated expansion valve 6 operates at a pre-determined temperature to close off all air and water egress at the same time as opening the float valve, thereby re-setting. Upon system cooling the heat expansion valve opens and releases the float valve, allowing one of two outcomes :- a) If there is air in the radiator it will escape until the raising water level lifts and closes the float valve, b) If there is already sufficient water in the system to raise the float valve, the float valve will shut immediately and neither water nor air will escape. In this way the radiators vents automatically.

Description

Thermostatic Float Vent The invention relates to a device that automatically vents gas (primarily air) from a liquid filled system (primarily water).

Gas venting devices are used in industrial and domestic applications as a means to expel alien gas products (entered via leaks) from liquid-filled systems so as to maintain system efficiency; The most common being (on a domestic scale), the air vent valve on top of a domestic hot water radiator which is used periodically to release air that has entered the system.

Most domestic radiators are provided with a manual vent that is operated by a'key' initially to fill the system, then at periodic intervals to ensure system operating efficiency, and occasionally it is opened to drain the system.

Automatic vents are available and provide several attractive features not associated with the manual version: They relieve the heating system fitter from the awkward task of visiting each radiator in turn to close the manual vents while the system fills during the'priming'phase (a task exacerbated by multi-level radiator installations).

They eliminate the need for manual venting at undefined periods to ensure radiators operate at full efficiency (it requires using a'key'and is difficult for the unable or uninitiated), and on the occasion when the system requires draining (to clean, replace rust inhibitors, or cure leaks), eliminates the need to manually vent each radiator.

The problem is that current designs exhibit associated detractors which deter heating system engineers and do-it-yourself inclined individuals from installing automatic vents.

The first type currently commercially available is a float on a lever type vent which utilises raising water levels in the system to elevate a float which exerts force via a lever on a valve to close the air way. The weight of the float and lever cause the valve to open when the water level drops so allowing expulsion of unwanted air. This type is reliable, but large, due to the necessary weight of the float to open the airway against a pressure difference between system pressure inside the radiator and that of atmospheric pressure outside. This makes it aesthetically unacceptable, eliminating it as a viable option for fitting to most domestic radiators and is traditionally fitted as a single unit to a system high-point. This doesn't vent air that has entered the radiators.

The second type is a hygroscopic vent which is small but liable to leak water. Its operating principle utilises a series of fibre washers that are sensitive to water and expands to prevent the escape of air molecules but traps the larger water molecules.

This is unreliable and British Standard BS 5449 does not recommend this type as it may permit water to escape.

The object of this invention is to provide a reliable automatic vent that is small and doesn't leak water therefore acceptable for domestic and other applications that require miniaturisation of the vent.

According to the present invention, there is a valve housing with an independently rotatable threaded collar which secures in place of the existing manual vent. Two valves are contained within the housing. The first operates via floatation and prevents the escape of gas when liquid rises to a pre-set level (but allows venting before it reaches this level), and the second that is self-powered, which operates when a pre-set temperature or pressure is reached and acts directly upon the float valve to re-set it, while at the same time closing itself A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 shows in perspective, the Auto-vent attached to the radiator vent port in side elevation (cross-sectional view) with the vent in the'cold'position and the radiator expelling air. This diagram applies for system draining conditions also.

Figure 5,2 shows a cut-away view of the vent in the'cold'condition with the float valve in the raised (floated) position with cessation of air expulsion.

Figure 5,3 shows the vent in the'hot'condition with the thermo-expansion valve operated and the float depressed (Auto-venting mode).

Figure 5,4 shows an isometric view of the Auto-vent.

Figure 5,5 shows an adaptor for narrow-threaded radiator vents.

Referring to the drawing (Fig. 1), the Auto-vent is secured via the collar 1 to the radiator vent port 9, either by the standard sized thread, or, via an adaptor (Fig. 5,5) which is used for the narrow threaded type radiator vents.

The unit is screwed into the radiator valve port by using a spanner on the hexagonal portion of the collar 11. The vent housing 10 is now rotated by hand to the correct operating orientation (ie. the float in the vertical position) and secured at this angle by the grub screw 3 (Fig 5,4).

The vent comprises of a float valve 2 which is centred and rides inside guide rails 4.

The float is shaped so that the air-flow dynamics on its surfaces allow it to remain open with air flowing over it until a point where it's proximity the valve seat 5 due to floatation is closed. The float has no protruberances and tends to'depress'rather than rise when the venting air expels. The float can only raise via floatation by water entering the vent housing via port 8 (strained through gauze 13). Integral to the float (at the top) is the float valve piston that meets the seating 5 when raised.

In addition, there is a thermal expansion disc valve taking the form of multiple metallic convex discs 6 which when heated to a pre-determined temperature'invert'.

Attached to these are the thermal valve piston 7 which upon operation performs two functions. One, is to close against the upper portion of the valve seating 5 thus preventing air egress, the second, is to depress and unseal the float valve.

Exit port 11 allows expulsion of air, while maintaining a restricting'back-pressure' that prevents escaping air from ramming the float valve closed before it closes via floatation from the correct water level being achieved. Blanking cap 15 seals the float chamber and circlip 12 retains the thermal expansion valve.

In operation two modes are to be considered (a) Initial system filling and emptying with float valve actuating upon water reaching a pre-determined height, (b) Thermalexpansion valve actuation upon system reaching a pre-determined temperature (Autoventing mode). a) Systemfilling 1emptying (Fig. I). This is performed while the system is cold.

Once the Auto-vent has been installed the radiator will fill with water as the system is'primed'. During this process, air present in the empty radiator evacuates through the entry port 8, passes the float 2 (presently unfloated), through seating 5, and out of the thermal expansion valve air cavity 14 via the exit port 11. Air Expulsion continues until a sufficient level of water in the radiator enters the entry port 8, floats the float valve and it's piston seats against seating 5, preventing further venting (Fig. 5,2). The radiator is now fully vented and operational.

At a time when the system needs emptying (to replace the radiator, clean the system, introduce rust inhibitors, or fix a leak) the system needs to be drained.

This is performed with the system cold and is the reverse of the above process.

The system can be emptied normally via a drain plug that will have been fitted to a system'low-point'. The process of draining water causes a vacuum in the radiator which sucks the float down into its unfloated position and allows air to be drawn into the Auto-vent via exit port 11, past the valve seating 5, through entry port 8 and into the radiator allowing complete system draining. b) Auto-venting mode (Fig. 5, 3). This takes place as the radiator heats and cools.

If the only mechanism in the vent was a float valve no auto-venting could take place because when air gradually fills the top of the radiator, even though the water level falls, the float valve would remain sealed due to the system pressure inside the radiator (approximately 1-1. 2 bar) keeping it in place. Consideration was given to enlarging the float so it's weight caused it to fall with the water level, but this defeated the object. This method required a very large float and reciprocally an enlarged vent. The problem was overcome with a second Thermally-activated valve.

In standard operating conditions the float valve will be raised with the water level to seal against seating 5 (Fig 5,2.).

When the system heats up and reaches a pre-determined temperature (Fig. 5,3) (approximately 60 C), the Thermal disc 6'inverts'due to thermal expansion (as similar to the type of thermal shut-off in a domestic kettle). The result of this is two-fold; Firstly, the discs piston 7 seals against the seating 5 preventing expulsion of air or water, and secondly, it depresses the piston on top of the float pushing the float down into its chamber, breaking its seal on the seating 5, thus re setting it.

The thermal discs remain inverted until the Auto-vent body temperature drops below 60 C. Several discs are employed in order to provide sufficient pressure to ensure the vent remains closed at elevated system temperature (thus pressure).

Below 60 C the thermal valve opens into the'cold'position (Fig. 1).

From here, either of two events occur. If air has leaked into the radiator the water level will not be high enough to raise the float, therefore air will be vented until the water level raises the float and seals, completing venting. If there no air in the system the float will raise immediately and shut off before water can escape.

This automatic venting cycle occurs each time the thermal valve operates.

Additional features relevant to this invention are that the top of the thermal valve may be manually depressed several times to ensure the system has fully vented (water droplets escape from the exit port 11).

It is envisaged that the float will be filled by a gas less dense than air so as to increase it's buoyancy, therefore potentially reducing the float size.

Scaled up or down versions of the Auto-vent may be used for radiators with smaller or larger vent holes, or an adaptor (as of the type shown in Fig. 5,5) may be utilise to attach the Auto-vent to the radiator/heating system.

Consideration was given to alternative thermally-activating valves constructed in Bi-metal and substances with a high coefficient of thermal expansion (wax, alcohol etc), but these were rejected in favour of the more convenient thermal disc variety which exhibits faster actuation in response to temerature change therefore minimising possible leakage.

An alternative to the thermostatic valve is a pressure valve consisting of a 'resevoir'that fills with vented air at elevated pressures (when the system heats, the system therefore air pressure raises). This could be utilised to unseal the float valve while the'pressure valve'seals.

Additionally, the Auto-vent could be used for venting other heated/cooled systems requiring a venting mechanism (such as oil, liquid gas, refrigeration situations, or medical applications/human body), where the liquid element activates the float valve and a temperature change operates a thermal valve acting upon the float.

Claims (8)

1. Thermostatic Float Vent : Claims 1) An automatic venting device comprising a valve housing with an independently-rotatable threaded collar which secures in place of the existing manual vent. Two valves are contained within the housing. The first operates via floatation and prevents the escape of gas when liquid rises to a pre-set level (but allows venting before it reaches this level), and the second that is self-powered, which operates when a pre-set temperature is reached and acts directly upon the float valve to re-set it, while at the same time closing itself.
2. 2) An automatic venting device (as claimed in claim 1) consisting of a float valve which, without a lever mechanism, prevents gas escape once a pre-set liquid level is reached.
3. 3) An automatic venting device consisting of a heat-activated valve which is self powered (not requiring external energy input) and operates to prevent gas or liquid egress from a system when a pre-set temperature is reached.
4. 4) An automatic venting device (as claimed in claim 1 and 3) consisting of a heat-activated valve which, at a pre-set temperature, opens a float valve. When the heat valve operates in its opposite mode due to temperature change, allows the float valve to release its seal and vent until a pre-set liquid level is reached.
5. 5) An automatic venting device (as claimed in claim 1 and claim 2) utilising a restricting (back) pressure that arrests the closure of a float valve that would otherwise shut due to unrestricted air-flow.
6. 6) An automatic venting device (as claimed in claim 1 and 2) utilising a float valve with air-flow dynamics such as will allow it to remain open with air flowing over it until a point where its proximity to the valve seat due to floatation is closed.
7. 7) An automatic venting device (as claimed in claim 1) comprising two valves.

   The first operates via floatation and prevents the escape of gas when liquid rises to a pre-set level (but allows venting before it reaches this level), and the second that is self-powered, which operates when a pre-set pressure is reached and acts directly upon the float valve to re-set it, while at the same time closing itself.
8. 8) An automatic venting device substantially described herein with reference to Fig. 1-5 of accompanying drawing.