GB2455138A

GB2455138A - Float and thermal expansion vent valve

Info

Publication number: GB2455138A
Application number: GB0723492A
Authority: GB
Inventors: Charles Bonello
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-11-30
Filing date: 2007-11-30
Publication date: 2009-06-03
Anticipated expiration: 2027-11-30
Also published as: GB0723492D0; GB2455138B

Abstract

An automatic venting device for venting gas from a system containing liquid comprises a float valve 14 and a temperature-dependent valve 30 formed of thermally expansive material. Above a predetermined temperature the volume of the temperature dependent valve increases so that a surface of the thermally expansive material closes a vent path 20 and the float valve 14 is displaced from its closed position.

Description

Float Vent This invention relates to a device adapted to automatically vent gas, for example air, from a liquid filed system.

Background

Gas venting devices are used in industrial and domestic applications as a means to expel gas products from liquid-filled systems so as to maintain the system efficiency. A common domestic example is an air vent valve on top of a domestic hot water radiator which is manually operated periodically by a key to release air that has entered the system.

Automatic vents are available and tend to fall into two categories (or a combination thereof). 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 causes 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, which does not then vent air already collected in 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 allows the passage of air when they are dry but expand when contacted by water thus closing an exit port. This has been considered unreliable and British Standard BS 5449 does not recommend this type as it may permit water to escape for the first few seconds until the fibre washers expand.

There have been attempts to provide improved automatic air venting devices which address the aforementioned problem. However, such prior art devices still suffer from disadvantages.

By way of example, GB2348477 discloses an automatic air venting device comprising a float valve and a piston which are activated by the level of liquid and the temperature of the system. More particular, the prior art device of GB2348477 uses a temperature activated bi-metallic disc that inverts above a predetermined temperature so as to prevent egress of air and displace the float valve from its closed position. To allow egress of air when the bi-metallic disc is not inverted, it is formed with one or more small apertures.

Use of a temperature activated bi-metallic disc in this way exhibits numerous disadvantages. Firstly, the disc is susceptible to rusting and becoming clogged by foreign particles, especially since it can come into contact with fluid from the system during manual operation (i.e. manual inversion of the disc to vent the system). Secondly, the area under the disc to allow for its inversion collects fluid and foreign particles which further inhibit its operation. Attempts have been made to alleviate the problem of rusting by applying a rust inhibiting coating to the disc. However, this has proven to be unsatisfactory since the coating deteriorates over time due to repeated flexing of the disc and contamination by inhibitors, de-sludging and de-scaling agents used in the system fluid.

Summary of the Invention

The invention provides an automatic venting device for venting gas from a system containing liquid is presented. In addition to a float valve, a temperature dependent valve is provided which is formed of thermally expansive material so that, above a predetermined temperature, the volume of the temperature dependent valve is such that a surface of the thermally expansive material closes the vent path of the venting device and the float valve is displaced from its closed position.

According to one aspect of the invention, there is provided an automatic venting device for venting gas from a system containing liquid, comprising: a body having: a connector for connecting to the system; a chamber in fluid communication with the connector; and a vent in fluid communication with the chamber via an orifice, the body defining a vent path from the connector through the orifice to the vent; a float contained in the chamber and movable between a closed position, in which the orifice is closed, and an open position in which float is spaced apart from the orifice; and a temperature dependent valve movable between a vent position in which the temperature dependent valve is spaced apart from the orifice, and an operation position, in which the orifice is closed, wherein the temperature dependent valve is formed of thermally expansive material so that, above a predetermined temperature, the volume of the temperature dependent valve is such that the temperature dependent valve is in the operation position and the orifice is closed by a surface of the thermally expansive material, and wherein movement of the temperature dependent valve from the vent position to the operation position acts to displace the float from its closed position.

The invention therefore provides a temperature dependent subsidiary valve which caused the float valve to move away from its closed position to unseal.

Thus, the float valve is no longer held in its closed position by air pressure and so venting of air can proceed if required. Embodiments therefore ensure that the float valve (or other valve closing means) is not forced closed by the pressure in the system forcing it up against the orifice, even against the force of gravity.

Unlike known automatic venting devices, the temperature dependent subsidiary valve uses bulk expansion of its volume to close the orifice and displace the float valve. Known automatic venting devices rely on differential expansion of differing materials or inversion of a convex disc to suddenly activate the subsidiary valve, whereas the temperature dependent subsidiary valve of the invention may use only a single lump of material simplifying manufacture and reducing costs. For example, preferred embodiments may use a temperature dependent subsidiary valve formed from a single lump of thermally expansive and non-corrosive material. Such subsidiary valves may therefore be injection moulded and manufactured at considerably lower costs than the temperature dependent subsidiary valves of prior auto-venting devices.

Embodiments of the invention may be less susceptible to corrosion than prior automatic venting devices due to not using metallic discs.

Embodiments of the invention may also comprise an over-riding shut down mechanism or feature which enables the fluid level in the system to be fixed at a low level, thereby enabling power flushing of the system to remove sludge or foreign debris.

Detailed Description of the Invention

An example of the invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 shows a side section of a first embodiment of the automatic venting device according to the invention with the vent in the "cold" position and the radiator expelling air. This diagram applies for system draining conditions also; Figure 2 shows a cut-away view of the automatic venting device of Figure 1 in the "cold" condition with the float valve raised (floated) position with cessation of air expulsion; Figure 3 shows the automatic venting device of Figure 1 in the "hot" condition with the thermo-expansion valve operated and the float depressed but contacting the thermo-expansion valve; Figure 4 shows a side section of an automatic venting device according to another embodiment of the invention; and Figure 5 shows a side section of a second embodiment of the automatic venting device according to the invention with the shut down cap screwed into the device to prevent egress of air from the device Referring to the drawing Fig.1, the automatic venting device of the first embodiment comprises a body having a housing 10 with a threaded connection portion 12. The venting device may be secured via the threaded connection portion 12 to a radiator vent port (not shown) on a system, either by the standard sized thread, or, via an adapter (not shown) used for narrow threaded type radiator vents.

The venting device comprises float valve 14 which is centred and rides inside a chamber 16 defined by the housing 10, between a raised closed position (Fig.2) and a lowered open position (Fig.1). In the closed position the float engages with a rubber valve seat 18 arranged around an orifice 20 in a plate member 22.

The housing defines an entry port 24, and exit vents 25. Thus, there is provided a vent path between the entry port 24 and the exit vents 25 through the orifice that is closed when the float valve 14 is in its closed position engaging the rubber valve seat 18 and so closing the orifice 20. Preferably, the entry port 24 contains gauze 26.

The float valve 14 is shaped so that the airflow dynamics on its surfaces allow it to remain open (i.e. spaced apart from the rubber valve seat 18 of the orifice 20) with air flowing over it until a point where it engages the rubber seat 18, due to floatation, to close the orifice 20. The float valve 14 tends to "depress" rather than rise when the venting air expels. The float valve 14 is adapted to only raise via floatation by water entering the housing 10 via the entry port 24 strained through the gauze 26. Integral to the float 14 at its top surface is a float valve piston or protrusion 28 with sloped edges which meet the valve seat 18 when raised.

The automatic venting device also comprises a temperature dependent valve in the form of a thermal expansion valve 30, the thermal expansion valve 30 being a single block of non-metallic and non-corrosive material 30 which significantly expands in volume when heated up (i.e. has a coefficient of thermal expansion significantly greater than ceramic material, for example, and preferably a multiple of that of metal) The thermal expansion valve 30 is located above the orifice 20.

Integral to the thermal expansion valve 30 on its lower surface is a thermal valve piston or protrusion 32 with sloped edges which, upon operation, performs two functions. Firstly, it moves from its vent position, in which the thermal expansion valve 30 is spaced apart from the orifice 20, to an operation position in which the thermal expansion valve 30 engages against the upper portion of the valve seat 18 to close the orifice 20. Secondly, it depresses and unseals the float valve 14 (Fig.3) from the orifice 20.

From Figure 1, it will be seen that the thermal expansion valve 30 is spaced apart from the sides of the housing 10 when in a "cold" condition (when unexpanded due to being at or below a predetermined temperature). Thus, the body 10 is adapted to accommodate three dimensional movement (i.e. expansion of the thermal expansion valve 30 in any of the three perpendicular directional axes) of the thermal expansion valve 30 when in a venting position.

In this way, expansion of the volume of the thermal expansion valve 30 as the temperature of the system increases is enabled, wherein a predetermined increase in the volume of the thermal expansion valve 30 moves the thermal expansion valve 30 to the operation position in which it engages against the upper portion of the valve seat 18 to close the orifice 20.

The thermal expansion valve 30 is formed with a release vent 34 extending through it along its central axis. The release vent 34 provides a release path from the chamber 16 to the exit vents 26 through the release vent 34. Release vent 34 therefore acts as a vent to allow expulsion of air, while maintaining a restricting "back-pressure" that prevents escaping air from ramming the float valve 14 closed before it closes via floatation from the correct water level being achieved.

The release vent 34 branches into three channels towards the upper surface of the thermal expansion valve 30. Further, the position of the release vent 34 on the underside of the thermal expansion valve is adapted to coincide with the float valve piston 28, so that the valve piston 28 closes the release vent 34 when the float valve 14 is in contact with the thermal expansion valve 30. To provide a good seal of the release vent 34, the valve piston 28 may be rubberised.

A hygroscopic washer 40 is provided on the upper surface of the thermal expansion valve 30 is also provided to prevent as a fail safe provision and prevent fluid spillage from the device. In the event that fluid seeps through the orifice 20 past the thermal expansion valve, such fluid is absorbed by the washer 40 and the washer 40 then expands so as to seal against the internal surface of the housing 10 and push down the thermal expansion valve 30 against the rubber seal 18 to form a (firmer) seal and prevent fluid from passing through the orifice 20. Thus, in such an event, the washer 40 expands to contact the inner surface of the top of the device so as to prevent fluid passing through the exit vents 25.

For use, the vent housing 10 is rotated to the correct operating orientation (with the float valve 14 in the vertical position) and secured at this angle. 0-rings (not shown) may be used to seal the housing 10 to the radiator vent port.

The operation of the automatic venting device will now be described with reference to Figures 1 to 4, showing a sequence of possible configurations Figure 1 shows an initial operation mode to be considered in which the system is to be filled with liquid (for example, water). System filling is performed while the system is cold. Once the apparatus has been installed the radiator will be filled with water as the system is primed". During this process, air present in the empty radiator evacuates through a vent path consisting of the entry port 24, past the float 14 in its open position, through the release vent 34 of the thermal expansion valve 30 in its operation position, and out of the device via the exit vents 25.

As air expulsion continues, the liquid level 36 rises (see Figure 2) lifting the float vent 14 upwards. As the float 14 rises, the float valve piston 28 extends through the orifice 20 and pushes the thermal expansion valve 30 upwards.

Eventually, the configuration of Figure 2 is reached where a sufficient level 36 of liquid in the chamber 16 seats the sloped edges of the piston 28 against the rubber seat 18, thereby preventing further venting of air from the system. The radiator is now fully vented and operational.

If gas now enters the system and subsequently lowers the liquid level 36, the float valve would remain sealed against the rubber seat 18 due to the internal pressure of the system (approximately 1-1.2 bar in domestic systems, and more systems for commercial/high-rise buildings) being greater than normal atmospheric pressure holding it in place. The float valve 14 must therefore be displaced from the rubber seat 18 in order to enable future venting cycles.

At a time when the system needs emptying (for example, to replace the radiator, clean the system, introduce rust inhibitors, or fix a leak) the system needs to be drained of liquid. 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 apparatus via exit vents 25, through the release vent 34 of the thermal expansion member 30 and into the radiator allowing complete system draining In standard operating conditions the float valve will be raised with the water level to close the orifice 20 and seal against seat 18, as shown in Fig. 2.

As the system heats up, the thermal expansion valve 30 increases in volume.

At a pre-determined temperature (for example, approximately 45 Degrees Celcius), the volume of the thermal expansion valve 30 is increased by such a value that the sloped surfaces of the thermal piston 32 contact the upper surface of the rubber seat 18 and the orifice 20 is closed. In other words, as a predetermined temperature, the thermal expansion valve 30 is moved to the operation position by thermal expansion of its volume (as shown in Figure 3).

The result of this is two-fold. Firstly, the surface of the thermal expansion valve contacts the rubber seat 18 and closes the orifice 20, preventing expulsion of air or water. Secondly, the thermal piston 32 depresses the top of the float W valve 14 pushing the float down into its chamber 10, breaking its seal on the lower surface of the rubber seat 18 and thus resetting it.

While the temperature of the system is above the predetermined value (i.e. while the system is "hot") the volume of the thermal expansion valve is such that the thermal expansion valve 30 remains in contact with the rubber seat 18 and the orifice 20 is closed.

If the temperature of the system falls below the predetermined value (i.e. the system condition is "cold"), the volume of the thermal expansion valve 30 reduces. The position of the thermal expansion valve will then depend on the water level. However, the design of the venting device is such that the venting of air will be enabled so as to maintain a desired level of water within the system.

As shown in Figure 3, if only a small amount of air has leaked into the radiator the water level will be high. When the system goes cold and the volume of the of the thermal expansion valve 30 reduces so that the float no longer closes the release vent 34, air can be immediately be vented through the release vent, preventing immediate ramming of the float valve 14 against the rubber seat 18.

Therefore, air will be vented until the water level 36 raises the float 14 and closes the orifice, completing venting. On the other hand, if there is no air in the system the float 14 will rise immediately and shut off before water can escape.

As shown in Figure 4, if the water level 36 is at a medium level, the float 14 contacts the thermal expansion valve and holds it in a position spaced apart from the rubber seat 18. Thus, the orifice 20 is not closed by either the thermal expansion valve 30 or the float valve. Air is then able to evacuate past the float 14 in its open position, through the orifice 20 past the thermal expansion valve in its vent position, and out of the device via the exit vents 25.

Referring now to Figure 5, a device according to another embodiment of the invention the housing 10 is provided with a screw cap 42 through which the exit vents 25 are formed. The screw cap 42 is formed with a central projection 44 extending downwardly along the axis about which is can be screwed into the housing 10. The central projection is sized such that it covers the release vent(s) 34 of the thermal expansion valve 30 so as to close the release vent(s) when the central projection contacts the top of the thermal expansion valve 30.

Thus, when a desired fluid level within the system has been attained, the screw cap 42 can be screwed into the housing to push down on the thermal expansion valve 30 and push it against the rubber seal 18, thereby closing the orifice 20 and closing the release vent(s) 34 to prevent egress of air/fluid through the device.

While specific embodiments have been described herein for purposes of illustration, various modifications will be apparent to a person skilled in the art and may be made without departing from the scope of the invention.

For example, scaled-up or -down versions of the vent may be used for radiators with smaller or larger vent holes, or an adapter may be utilised to attach the vent to the radiator/heating system.

Additionally, although the above embodiment is described as being a vent for a radiator system the 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.

The embodiment of Figure 5 may be further modified so that the screw cap is provided with a transparent window which allows the hygroscopic washer to be visible from the outside of the device. By adapting the hygroscopic washer so that it changes in colour, for example, when it absorbs liquid from the system (or providing other similar liquid indication means), a user can then quickly and conveniently check the operation of the device.

Claims

Claims 1. An automatic venting device for venting gas from a system containing liquid, comprising: a body having: a connector for connecting to the system; a chamber in fluid communication with the connector; and a vent in fluid communication with the chamber via an orifice, the body defining a vent path from the connector through the orifice to the vent; a float contained in the chamber and movable between a closed position, in which the orifice is closed, and an open position in which the float is spaced apart from the orifice; and a temperature dependent valve movable between a vent position in which the temperature dependent valve is spaced apart from the orifice, and an operation position, in which the orifice is closed, wherein the temperature dependent valve is formed of thermally expansive material so that, above a predetermined temperature, the volume of the expansion of the temperature dependent valve urges a surface of the thermally expansive material against the orifice to close the orifice, and wherein movement of the temperature dependent valve from the vent position to the operation position acts to displace the float from its closed position.
2. A device according to claim 1, wherein, the body is adapted to accommodate three dimensional movement of the temperature dependent valve when in the vent position and such that a predetermined increase of the volume of the temperature dependent valve moves the temperature dependent valve from the vent position to the operation position.
3. A device according to claim br 2, wherein the temperature dependent valve is formed from a non-metailic material.
4. A device according to any preceding claim, wherein the temperature dependent valve comprises a release vent adapted to provide a release path from the chamber to the vent through the release vent, and wherein the float is adapted to close the release vent when the float is in contact with the temperature dependent valve.
5. A temperature dependent valve for an automatic venting device having a float valve movable between a closed position, in which the an orifice of the venting device is closed to seal a vent path, and an open position in which the float is spaced apart from the orifice, wherein the temperature dependent valve is formed of thermally expansive material and adapted so that, above a predetermined temperature, the volume of the temperature dependent valve is such that a surface of the thermally expansive material closes the orifice of the venting device and the float valve is displaced from its closed position.
6. A temperature dependent valve according to claim 5, wherein the temperature dependent valve comprises a release vent adapted to provide a release path for air to pass through the temperature dependent valve.
7. A temperature dependent valve according to claim 5 or 6, wherein the temperature dependent valve is formed from a non-metallic material.
8. An automatic venting device substantially as hereinbefore described with reference to the accompanying figures.