GB2392226A

GB2392226A - Thermostatic float vent

Info

Publication number: GB2392226A
Application number: GB0328303A
Authority: GB
Inventors: John Francis Steeple Heffernan
Original assignee: NLB Engineering Ltd
Current assignee: NLB Engineering Ltd
Priority date: 2003-12-05
Filing date: 2003-12-05
Publication date: 2004-02-25
Anticipated expiration: 2023-12-05
Also published as: GB0328303D0; GB2392226B

Abstract

An automatic venting device for venting gas from a system containing liquid e.g. a domestic radiator, comprising a float (34) a valve member (46) and a temperature activated valve (58). Upwards movement of the float with the liquid level of the systems acts to close the valve member. An increase in temperature of the system causes activation of the temperature activated valve, which acts to open the valve member. The valve member preferably contains a ball bearing.

Description

AUTOMATIC VENTING DEVICE

The present invention relates to a device that automatically vents gas from a system containing liquid.

5 Automatic gas venting devices are used in industrial and commercial situations to expel gasses from a range of liquid filled systems. The most common domestic application is to vent or bleed air from water- filled heating systems.

Typically, a domestic heating system comprises a number of 10 radiators through which hot water is pumped. The radiators are usually provided with a manual vent which can be opened by a user with a key to periodically bleed the system of air.

However, this system has a number of disadvantages.

When installing or refilling such a heating system, a 15 user must visit each radiator to manually vent air. This is particularly problematic where the system has a large number of radiators situated on different levels of a building.

Once the system is operational, the user should then periodically check each radiator and manually vent any air 20 which is present. Air tends to leak into such systems through a variety of sources, such as leaks in connections in the system and through precipitation of dissolved gasses in the liquid itself.

There have been attempts to provide automatic venting 25 devices. However, these prior art devices have suffered from

a number of disadvantages.

For example, GB1479678 discloses an automatic air vent comprising a float valve and a piston which are activated by the level of liquid and the internal pressure of the system.

30 The device has a relatively complicated construction and depends upon the internal pressure of the system to operate

l effectively. As a result, the device disclosed does not effectively automatically vent gas from liquid-containing systems. GB2348477 and EP1041324 both disclose a float vent for 5 automatic venting of gas from a liquid-filled system. The device is shown in figure 1 and uses a float valve which engages a valve seat when raised by the liquid level in the system. The prior art venting device is shown generally at 1 and

lO comprises a body 2 having a threaded connector 3 for connection to a radiator 4, or the like. The connector 3 defines an opening which leads to a chamber 5. The upper wall of the chamber 5 has an orifice 6 which leads to a vent port 7 open to the atmosphere. The device 1 thus defines a 15 vent path leading from the system 4 through the connector 3, chamber 5, orifice 6 and vent port 7 to the atmosphere.

A float valve 8 is contained within the chamber 5, having a substantially cylindrical shape with a projecting tip 9 on its upper surface. The float valve 8 has a density 20 less than that of the liquid in the system and so rises and falls within the chamber 5 with the level of liquid. As the float valve 8 rises, the tip 9 enters the orifice 6 and comes into contact with an O-ring 10 therein, closing the vent path. The O-ring 10 defines a valve seat. Thus, from an 25 initial position with the float valve 8 spaced away from the orifice 6, any gas present may be expelled through the vent path, allowing the liquid level to rise. As the liquid level rises, the tip 9 eventually closes the vent path by coming into contact with the O-ring 10.

30 If air subsequently enters the system, the level of liquid drops. However, because the internal pressure of the

system 4 is higher than atmospheric pressure, the float valve 8 tends to remain engaged against the valve seat 10 and does not drop with the liquid level.

In order to allow an automatic venting cycle, there is 5 also provided a temperature activated subsidiary valve 11.

The subsidiary valve 11 comprises a concave bi-metallic disc 12 having a substantially cylindrical piston 13 projecting away from the centre of the concave face of the disc. Once the temperature of the system reaches a predetermined level, 10 the subsidiary valve 11 activates by inversion of the disc 12 to move the piston 13 downwards into contact with the valve seat 10 and to also contact the float tip 9 to displace the float valve 8 from the valve seat 10. In this way, the vent path remains closed although the float valve 8 has been 15 displaced from the valve seat 10.

Once the temperature of the system drops below a predetermined level, the subsidiary valve 11 deactivates by the inversion of the disc 12 to its initial concave configuration, causing the piston 13 to move away from the 20 valve seat 10. If there is any gas present in the system 4, it may now vent through the open vent path. The rising level of the liquid will then raise the float valve 8 again to engage the valve seat 10 thus close the vent path.

Alternatively, if no gas was present in the system 4, 25 the float valve 8 would simply re-engage the valve seat 10 as the piston 13 of the subsidiary valve 11 moves away. The cycle of these events thus allows automatic venting of gas from the system 4.

Although this system was a marked improvement over the 30 prior art, it suffers from a number of disadvantages.

In order to work efficiently and to reliably and

effectively close the vent path, the tip 9 of the float valve 8 must be very precisely shaped. Furthermore, the O-ring 10 must be lubricated in order for the tip 9 of the float valve 8 to effectively engage and seal the vent path. However, 5 with time, the lubricant may be leached away thus reducing the reliability and effectiveness of the seal. Also, the presence of the lubricant itself also attracts debris and dust thus reducing the effectiveness of the seal.

Also, the level of machining required to precisely and 10 accurately shape the float tip leads to high manufacturing time and expense and also a high failure rate. Each valve unit must be partially assembled and tested before sale.

Minor incompatibilities between the O-ring and the tip of the float valve leads to a relatively high failure rate. This is 15 exacerbated by rotation of the float valve within the chamber to present new orientations of the float tip against the valve seat. Some orientations may give a reliable fit whereas other combinations may not effectively seal.

Furthermore, repeated contact between the piston of the 20 subsidiary valve and the float tip may lead to damage to one or both parts, again leading to loss of reliability over the long term.

There exists a need, therefore, for an improved automatic venting device.

25 According to the present invention there is provided a automatic venting device for venting gas from a system containing liquid, comprising: a body having a connector portion for connecting to the system, 30 a chamber in fluid communication with the connector

portion, a vent in fluid communication with the chamber by an orifice, the body defining a vent path from the connector portion 5 through the chamber and orifice to the vent, a float contained in the chamber and moveable between a first position and a second position, a valve member moveable between a closed position in which the orifice is closed and an open position in which the 10 orifice is open, a temperature activated valve moveable between an open position in which the orifice is open and a closed position in which the orifice is closed, wherein movement of the float from the first position to 15 the second position acts to move the valve member from the open position to the closed position, and wherein movement of the temperature activated valve from the open position to the closed position acts to move the valve member from the closed position to the open 20 position.

Preferably, the valve member comprises a ball-bearing.

Conveniently, the valve member comprises a flap.

Advantageously, the valve member comprises a piston.

Preferably, the temperature activated valve comprises a 25 thermal disc that inverts above a predetermined temperature.

Conveniently, guide means are provided to guide the float between the first position and the second position.

Advantageously, the device is for attachment to a radiator.

Preferably, the device comprises means to manually move the temperature activated valve between the open position and the closed position.

According to another aspect of the present invention, 5 there is provided a radiator comprising an automatic venting device of the invention.

The present invention will now be described, by way of example, with reference to the enclosed figures in which: Figure 1 is a cross-sectional view of an automatic 10 venting device according to the prior art;

Figure 2 is a cross-sectional view of an automatic venting device according to the present invention; Figure 3 shows a sequence of events of the operation of an automatic venting device of the present invention; and 15 Figure 4 is a sequence showing the operation of an alternative embodiment of the automatic venting device; Turning to Figure 1, a prior art automatic venting

device is shown generally at 1. The structure and function of the device 1 has been explained in detail above.

20 As mentioned above, the shape and dimensions of the float tip 9 must be controlled to very low tolerances in order to effectively seal against the O-ring 10. Debris in the system and movement of the float reduces the reliability of the seal formed by the float tip 9 against the O-ring 10.

25 Also, the necessary use of lubricants on the O-ring 10 attract dust and reduces the life of the device.

Turning to figure 2, a venting device of the present invention is shown generally at 20, comprising a body 22.

Tile body 22 defines a connector portion 24 for connection to 30 radiators and the like. The connector portion 24 defines an

opening leading to a chamber 26 of generally cylindrical shape. The upper wall 28 of the chamber defines an orifice 30 leading to vent ports 32 on the upper face of the device 20. The device 20 defines a vent path from a system 5 sequentially through the connector portion 24, into and through the chamber 26, through the orifice 30 and finally through the vent ports 32 to the external atmosphere. A [loaf valve 34 is housed within the chamber 26 and has a generally cylindrical shape. The float valve 34 has tapered 10 or sloping upper shoulders which allow for flow of gas over the float valve 34, as will be described in more detail below. On the lower planar surface of the float valve 34 there is located a downwardly extending guide rod 36 which is 15 received as a close sliding fit within a complementary shaped aperture 38 in the lower wall of the chamber 26. The movement of the guide rod 36 within the aperture 38 helps to maintain the axially-central position of the float valve 34 within the chamber 26 as it moves up and down with the liquid 20 level. There are also depressions 40 in the floor of the chamber 26 below the float 34 which allows for debris to settle without impeding the movement of the float 34.

Also, the float 34 is spaced away from the sides of the chamber 26 by a predetermined amount to leave a gap 42.

25 On a small scale, liquids, especially water, behave quite differently than on a large scale. For example, a small liquicl-filled gap between two parts may act to impede their relative movement. In order to alleviate these unwanted effects, the float 34 is positioned away from the

side walls of the chamber 26 to leave a sufficiently large gap 42 to allow unimpeded movement.

An upwardly projecting cylindrical tip 44 extends from the centre of the upper surface of the float 34.

5 Below the orifice 30 there is located a valve 46 comprising a downwardly extending tubular member 48. The member 48 has a first orifice 50 located at its lower end and a plurality of orifices 52 located in its side wall at a point towards the upper wall of the chamber 26.

10 Within the member 48 there is housed a steel ball bearing 54 having a diameter larger than the first orifice 50. The member 48 leads to the orifice 30 in the upper wall of the chamber 26, in which is located an Oring 56 defining a valve seat.

15 Above the orifice 30 is located a temperature activated valve 58 comprising a concave bi-metallic disc 60. A cylindrical piston 62 extends downwardly from the centre of tile concave face of the disc 60. An aperture 64 is provided in the disc 60 to allow the venting of gas from the orifice 20 50 through to the vent ports 32.

The operation of the device 20 will now be described with reference to figure 3, showing a sequence of possible configurations A to F. An initial position of the device 20 is shown in A with 25 a low liquid level 66. The float 34 is positioned towards the bottom of the chamber 26. The ball bearing 54 is positioned at the bottom of the tubular member 48 and the temperature activated valve 58 is in its "normal" concave configuration.

In this configuration, the vent path is open, allowing gas to vent from the system through the device 20 and out through the vent ports 32. As the gas vents, the liquid level 66 rises, lifting the float 34 upwards. As the float 5 34 rises, the tip 44 extends through the first orifice 50 of the member 48 and so pushes the ball bearing 54 upwards.

Eventually, configuration B is reached where the ball bearing 54 has been lifted up and pressed against the O-ring 56, closing the vent path. Substantially all of the gas has now 10 been vented.

If gas now entered the system and lowered the liquid level 66, the ball bearing 54 would tend to remain against the O-ring 56 because the internal pressure of the system is -sigher than atmospheric pressure. The ball bearing 54 must 15 therefore be displaced from the O-ring 56 in order to allow for future venting cycles.

Once the system reaches a predetermined temperature (about 47 C), the temperature activated valve 58 operates, with the disc 60 inverting from its normal concave 20 configuration to its activated convex configuration. This activation forces the piston 62 downwards to close the vent path and to displace the ball bearing 54 from the O-ring 56.

The piston 62 contacts the O-ring 56 to seal the vent path.

This leads to configuration C. 25 If no air enters the system in configuration C, the system will return to configuration B as follows. As the temperature drops, the temperature activated valve 58 returns to its normal position, moving the piston 62 upwards away from the O-ring 56. As the liquid level 66 is still high,

the float valve 34 is already raised in the chamber 26, holding the ball bearing adjacent to the O-ring 56. As the piston 62 moves away from the Oring 56, the ball bearing 54 irniediately moves into contact with the Oring 56 to close 5 the vent path.

However, if air enters the system during configuration C, the liquid level 66 drops, lowering the float 34. As the hall bearing 54 had been displaced from the O-ring 56, it is free to drop down towards the bottom of the member 48. As 10 the system is still hot, the piston 62 is pressed against the O-ring 56 to close the vent path.

Once the temperature of the system drops below a predetermined valve (about 35 C), the temperature act:ivated valve 58 returns to its normal position, moving the piston 15 62 away from the O-ring 56, thus opening the vent path. This is shown as configuration E. Gas may then be vented, raising the liquid level 66 and the float valve 34, to return to configuration B. Another possible sequence is the appearance of gas 20 during configuration B. leading to configuration F. IJere, the system is "cold", and the temperature activated valve 58 is in its normal position. The float 34 lowers with the liquid level 66, and the ball bearing 54 remains pressed against the O-ring 56 by the internal pressure of the system.

25 No gas may vent in the configuration.

As the system heats up, the temperature activated valve 58 activates, forcing the piston 62 downwards into contact with the O-ring 56. In doing so, the piston 62 also displaces the ball bearing 54 from the O-ring 56, leading to

configuration D. Again, as the piston 62 is in contact with the O-ring 56, the gas cannot vent. However, as the system cools down, the temperature activated valve 58 returns to its normal position, leading to configuration E. Gas may now 5 vent from the system, leading back to configuration B. The use of a ball bearing as a means to close the vent path has a number of advantages. As mentioned above with regard to the prior art, direct contact between a fd oat tip

and an O-ring had several disadvantages. The high level of 10 precision required in order to adequately shape the float tip leads to high manufacturing costs and a high failure rate.

The necessary use of lubricants also leads to attraction of debris, reducing the reliability of the seal. In contrast, ball bearings may be manufactured to a very high level of 15 accuracy, for example, by a grinding process. Ball bearings of a wide range of sizes and materials are available at relatively low cost. Furthermore, the highly symmetrical shape of ball bearings leads to a 'self-locating' sealing mechanism. In other words, as a ball bearing is pushed 20 towards and against a valve seat, such as an O-ring, it will automatically guide itself towards the centre of the valve-

seat to accurately and reliably form a seal. Use of a stainless steel ball bearing reduces problems associated with wear and tear and corrosion, giving a long working life of 25 the device.

Overall, the use of ball bearings in this way can lead to low manufacturing costs, a low failure rate, a reliable seal-forming mechanism and a long working life of such a device.

Figure 4 shows an alternative embodiment of a device according to the invention, shown generally at 68. The device 68 is similar to tile device 20 discussed above and shown in figure 2. The device 68 comprises a body 70 5 defining a chamber containing a float 72, having a relatively short tip 74 on its upper surface. An orifice 76 is defined in the upper wall of the chamber containing an O-ring 78.

Above the orifice 76 is located a temperature controlled valve 80, comprising a concave bi-metallic disc 82 and a 10 downwardly projecting piston 84.

Below the orifice 76 is located a valve 86 comprising a flap 88 pivotably attached to the upper wall of the chamber.

The upper surface of the flap 88 is provided with a projection 90.

15 The device 68 operates in a similar way to that shown in figure 3 in relation to device 20. As the float 72 rises, the tip 74 contacts the lower face of the flap 88, pivoting it upwards to come into contact with the bottom of the O-ring 78, closing the vent path. The projection 90 is then 20 positioned through the orifice 76. Upon activation of the temperature activated valve 80, the disc 82 inverts forcing the piston 84 downwards. The tip of the piston 84 then contacts the tip of the projection 90 on the flap 88, forcing the flap 88 to pivot downwardly away from the O-ring 78.

25 Also the piston 84 comes into contact with the O-ring 78 thus closing the vent path. Automatic venting cycles can then take place for device 20 in a similar way to that shown in figure 3.

Claims

CLAIMS:

1. An automatic venting device for venting gas from a 5 system containing liquid, comprising: a body having a connector portion for connecting to the system, a chamber in fluid communication with the connector portion, 10 a vent in fluid communication with the chamber by an or l i l ce, the body defining a vent path from the connector portion through the chamber and orifice to the vent, a float contained in the chamber and moveable between a 15 first position and a second position, a valve member moveable between a closed position in which the orifice is closed, and an open position in which Lie orifice is open, a temperature activated valve moveable between an open 20 position in which the orifice is open and a closed position in which the orifice is closed, wherein movement of the float from the first position to the second position acts to move the valve member from the open position to the closed position, 25 and wherein movement of the temperature activated valve from the open position to the closed position acts to move the valve member from the closed position to the open position.

2. A device according to claim 1 wherein the valve

member comprises a ball-bearing.

3. A device according to claim 1 wherein the valve member comprises a flap.

4. A device according to claim 1 wherein the valve 5 member comprises a piston.

5. A device according to any preceding claim wherein the temperature activated valve comprises a thermal disc that inverts above a predetermined temperature.

6. A device according to any preceding claim wherein 10 guide means are provided to guide the float between the first position and the second position.

7. A device according to any preceding claim for attachment to a radiator.

8. A device according to any preceding claim 15 comprising means to manually move the temperature activated valve between the open position and the closed position.

9. A radiator comprising an automatic venting device as defined in any preceding claim.

10. An automatic venting device substantially as herein 20 before described with reference to and as shown in the accompanying drawings.