GB2399168A

GB2399168A - Thermostat valve cap

Info

Publication number: GB2399168A
Application number: GB0412657A
Authority: GB
Inventors: Bjarne Frederiksen
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 2001-12-20
Filing date: 2002-12-13
Publication date: 2004-09-08
Anticipated expiration: 2022-12-13
Also published as: AU2002366849A1; GB2399168B; CN1608232A; GB0412657D0; DE10162606A1; CN100524137C; WO2003054651A1; DE10162606B4

Abstract

Disclosed is a thermostat valve cap (1) comprising a thermostat element (7) provided with a pressure chamber (8) whose volume changes depending on the temperature. The inventive thermostat valve cap (1) also comprises an actuating element (17) interacting with an expansion area (14) of the thermostat element (7), and a safety device. Said safety device encompasses an expanding pressure relief area (12) outside the expansion area(15) so as to keep the space requirement as little as possible.

Description

23991 68 Thermostat valve top part The invention concerns a thermostat

valve top part com prising a thermostat element provided with a pressure chamber, whose volume changes depending on the tempera- ture, an actuating element interacting with an expansion area of the thermostat element, and a safety device.

Such a thermostat valve top part is known from, for exam- ple, DE 199 17 781 Al.

Radiator valves are in many cases provided with thermostat valve top parts, which control the flow of a heat carrying medium, for example hot water, through the radiator in de- pendence of the room temperature. For this purpose, the radiator valve is prestressed in the opening direction.

The actuating element of the thermostat valve top part presses on a pin in the radiator valve in the closing di rection. When the volume of the pressure chamber expands due to a higher temperature, the actuating element is pressed out of the thermostat element; the actuating ele- ment then presses on the pin, and the radiator valve is closed. When, however, the volume of the pressure chamber is reduced with sinking temperatures, the pressure on the actuating element decreases, and the radiator valve can open again.

From time to time, cases occur, in which the radiator valve is already completely closed, however a higher tem- perature endeavours to further increase the volume of the pressure chamber. As the actuating element cannot move further in the direction of the radiator valve, a safety device is provided. The safety device gives an evasion op- portunity, into which the thermostat element can expand further without damaging itself or other parts. Also in this case, the deformability of the expansion area is utilised, the actuating element, however, no longer being pressed away, but the thermostat element itself being dis- placed. This applies particularly for thermostat elements with a liquid filling. With a vapour filling, the thermo- stat element can usually be dimensioned so that it can adopt the higher pressure occurring in connection with an overtemperature, without being damaged. For example, 5 bar occur in the normal situation, 10 bar in connection with an overtemperature.

With thermostat valve top parts, particularly radiator thermostat valve top parts it is endeavoured to keep the size small. On the one hand for optical reasons, on the other hand, the top part should not project too far from the radiator into the room.

The demand for a small size, however, collides with the technical necessity of providing an evasion space for the thermostat element in connection with an overtemperature.

The invention is based on the task of keeping the space requirement small.

With a radiator thermostat valve top part as mentioned in the introduction, this task is solved in that the safety device has an expanding pressure relief area outside the expansion area.

With this embodiment, it is no longer necessary to cause the volume expansion of the thermostat element in connec- tion with an overtemperature by a deformation of the ex- pansion area. Usually, the expansion area has a relatively small diameter, so that for a volume expansion an accord- ingly large movement is required. When the volume expan- sion of the thermostat element is made by deformation in another spot, for which the thermostat element comprises the expanding pressure relief area, for example, a larger diameter can be deformed, and a substantially smaller movement will be sufficient for the same volume change.

Thus, the length of the thermostat valve top part will be substantially reduced. The larger diameter is usually available without problems. The thermostat valve top part is particularly meant for use with radiators. However, it can also be used with other temperature control devices, for example air-conditioning systems.

Preferably, the actuating element is inserted in a cavity of the thermostat element, which is bordered by an inner wall, and the overpressure area is located on a wall, which borders the thermostat element on the outside. The thermostat element thus has a cup-shaped cavity, whose wall, the socalled "inner wall" is often formed by a bel lows. If the volume expansion were made exclusively here, only the relatively small diameter of the cavity could be used for the volume expansion. When, however, another part of the thermostat element wall is used for the volume ex- pansion, the dimensioning is substantially more free. The volume expansion can be realized with a substantially smaller movement. - 4 -

This applies particularly, when the expanding pressure re lief area is made on a circumferential wall of the ther mostat element. Here is the largest diameter, that is, when the circumferential wall of the thermostat element is slightly enlarged, this gives a substantially larger vol- ume increase than a corresponding shortening of the inner wall surrounding the cavity.

Preferably, the expanding pressure relief area is formed by a corrugation of the circumferential wall of the ther- mostat element. This is a relatively simple way of permit- ting a length change on the circumferential wall of the thermostat element. Further, this corrugation has an addi- tional advantage: the corrugation provides a larger active surface, via which a heat exchange of the pressure chamber with the environment can take place. Thus, the thermostat element can follow changes in the ambient temperature faster. In case that the inlet temperature of the heat me- dium takes influence on the temperature of the filling of the thermostat element via heat lines in the radiator valve, the corrugation may be regarded as "cooling ribs", via which an improved heat transfer to the environment can take place.

Preferably, the corrugation on the circumferential wall has a smaller number of waves than a corrugation in the expansion area. Thus, the thermostat element is formed by a case, two walls of which, namely the outer circumferen- tial wall and the inner wall, are made as bellows. As the circumferential wall has to perform smaller length changes than the inner wall, less deformation areas may be pro- vided here. Less waves will be sufficient. This simplifies the manufacturing of such thermostat elements.

Preferably, an overpressure spring acts in the area of a largest diameter upon the thermostat element. This embodi- ment has several advantages. Firstly, the overpressure spring is kept away from the actuating element. The over- pressure spring is usually made of a metal, thus having a relatively good heat conductivity. When the heat is led into the outer area of the thermostat element, it can be dissipated relatively fast from the thermostat element.

There is no risk that this heat will be carried to the in- side of the thermostat element via the actuating element.

Additionally, the support in the area of the largest di- ameter has the advantage that the force of the overpres- sure spring acts in the area of the circumferential wall of the thermostat element, where the forces can be adopted in the best manner. Thus, the "bottom" of the thermostat element can have a relatively weak dimensioning, which makes the manufacturing even cheaper.

Preferably, the overpressure spring is supported in a twist handle, in which the thermostat element is located.

The twist handle serves the purpose of setting the desired value, through which the thermostat element shall be con- trolled. Usually, this occurs through a position change of the thermostat element in relation to the radiator valve.

When the overpressure spring is supported in the twist handle, it is turned together with the twist handle and the thermostat element. Relative movements between the thermostat element and the twist handle or the spring, re spectively, should therefore not be feared.

Preferably, the overpressure spring cooperates with a length limitation device. In a manner of speaking, the - 6 - length limitation device defines the "zero position", that is, the position, which the thermostat element assumes, when an overtemperature is not occurring. From this position, the temperature control via the radiator valve can take place without problems.

Preferably, the length limitation device exists in the form of a stop in the twist handle. This is a relatively simple embodiment. The twist handle then defines the "zero position" of the thermostat element.

In an alternative embodiment, the length limitation device exists in the form of a stop inside the thermostat ele- ment. This is particularly advantageous, when the thermo stat element is only fixed in the twist handle with one front side, however, otherwise is free to move in the twist handle.

Preferably, the overpressure spring bears on the twist handle from the radial inside. The overpressure spring is then supported radially outwards by the twist handle. This permits the use of a spring, which has a relatively poor natural stability, and which is otherwise merely dimensioned for the forces, which it must oppose during an overpressure caused by an overtemperature. The overpres- sure spring cannot "buckle out" radially outwards. An in- ward deformation is practically not to be feared.

Preferably, the expansion area and/or the expanding pres sure relief area have a sliding sealing area with two mu- tually displaceable parts of the thermostat element. In many cases, the expansion area and the expanding pressure relief area are formed by a bellows, as stated above. An alternative to this involves displacing of two parts of the case forming the thermostat element, in relation to each other, and at the same time sealing these parts in relation to each other.

It is particularly preferred that in the sliding sealing area a deformable wall section of a part, which is acted upon by the pressure in the pressure chamber, bears on a supporting wall of the other part. This is a relatively simple embodiment, which ensures an excellent tightness in spite of the relative displacement of the two parts. The higher the pressure in the pressure chamber is, the more is the deformable wall section pressed against the sup- porting wall.

Additionally or alternatively, the thermostat element can have a deformable bottom. Also a deformable bottom permits a volume expansion of the thermostat element pressure chamber, without acting upon the expansion area.

It is preferred that the bottom is made as a diaphragm.

Diaphragm is to be understood as all components, which can be deformed and return to their original position, when the pressure subsides. Actually, almost any flexible mate rial can be used for this purpose, preferably, however, an elastomer plastic.

In an alternative embodiment, it may be ensured that the bottom has an edge area, in which it has a bellows shape.

Here, the deformation of the bottom is substantially lim- ited to the edge area. However, the bellows shape here en- sures the deformability. - 8 -

Preferably, the edge area is compressible, when the pres- sure in the pressure chamber increases. This gives the same kind of volume expansion as the expansion area. The volume expansion here occurs through a length change with a larger diameter, so that a substantially smaller length change, that is, a substantially smaller movement, will be sufficient for the same volume expansion than in the case of a volume expansion through a deformation of the expan- sion area.

Preferably, the actuating element is made of a poorly heat conducting material, particularly plastic, glass or ce- ramic. This prevents a direct heat conduction from the ra- diator valve into the pressure chamber, as this heat con auction could have a negative influence on the control behaviour of the thermostat valve top part.

Preferably, the actuating element has an actuating end, a heat isolating and/or heat reflecting protective plate be ing located between the actuating end and the thermostat element. The actuating end is the end, with which the thermostat valve top part acts upon the radiator valve, or rather, the tappet. When, now, a protective plate is lo- cated between this end and the thermostat element, a ther mal influence between the radiator valve and the thermo- stat element through heat conduction or heat radiation via the room is avoided.

In a particularly preferred embodiment it is provided that the pressure chamber is divided into two different partial pressure chambers having a spatial distance from each other and being connected with each other by means of a line, one partial pressure chamber comprising the expan - 9 sion area and the other partial pressure chamber compris- ing the expanding pressure relief area. This embodiment is particularly advantageous in connection with a remote sensor, with which the actual temperature detection for the radiator takes place at a position remote from the ra- diator. Via the line, the thermostat element reports the pressure conditions at the measuring position back to the radiator valve. The expanding pressure relief area can then be located in the remote sensor element.

In the following, the invention will be described in de- tail on the basis of preferred embodiments in connection with the drawings, showing: Fig. 1 a schematic sectional view through a radiator thermostat valve top part Fig. 2 a schematic view explaining the mode of opera tion Fig. 3 a sectional view of a second embodiment of a thermostat valve top part Fig. 4 a third embodiment of a thermostat valve top part Fig. 5 a fourth embodiment of a thermostat valve top part Fig. 6 a fifth embodiment of a thermostat valve top part - 10 Fig. 7 a sixth embodiment of a thermostat valve top part Fig. 8 a seventh embodiment of a thermostat valve top part Fig. 9 a schematic view of a thermostat valve top part with remote sensor element A thermostat valve top part 1 for a radiator valve com- prises a housing 2 with a connection geometry 3 for con- nection with a radiator valve (not shown in detail). A un- ion nut 4 is provided to fix the top part 1 in the radia- tor valve.

The thermostat valve top part 1 comprises a twist handle 5, which is rotatable by means of a thread 6 in relation to the housing 2, whereby its position can be changed.

In the twist handle 5 is located a thermostat element 7.

The thermostat element 7 comprises a pressure chamber 8 with a liquid filling (not shown in detail). The liquid is made so, that its volume expands during a temperature in- crease and is reduced during a temperature reduction.

The thermostat element 7 comprises a front side 9, which bears on a front side 10 of the twist handle 5. The ther- mostat element 7 further comprises a bottom 11, which is connected with the front side 9 via a circumferential wall 12. The circumferential wall has the shape of a bellows, that is, it has a corrugation with a plurality of waves 13, so that, within certain limits, the circumferential wall 12 can change its length.

Further, the thermostat element comprises a cup-like cav- ity 14, which is bordered by an inner wall 15. Also the inner wall has the shape of a bellows. Its corrugation has a plurality of waves 16, the number of which is larger than the number of waves 13. However, the number of waves 13 can be kept smaller, than was previously the case, as in case of an error, the actuating element 17 has to move less.

In the cavity 14 is located an actuating element 17, coop- erating during operation with the tappet 18, shown with dotted lines of the radiator valve, which is otherwise not shown in detail.

At the lower end in Fig. 1, the actuating element 17 has an actuating end 19. This actuating end 19 may have a pre determined design for better cooperation with the tappet 18. Between the actuating end 19 and the thermostat ele ment 7 is located a protective plate 20, which is designed to be heat isolating and/or heat reflecting. The actuating element is made of a poorly heat conducting material, for example a plastic, glass or ceramic. Thus, it is avoided that a heat transfer occurs from the tappet 18 via the ac tuating element 17 into the inside of the thermostat element 7. A heat radiation is interrupted by the protective plate 20.

By means of an overpressure spring 21, the thermostat ele ment 7 is retained in the twist handle 5. The overpressure spring 21 is suspended between a circumferential projec- tion 22 in the twist handle and thermostat element 7, which bears on a step 23 in the wall of the twist handle. - 12

The step 23 forms a length limitation device for the over pressure spring 21.

During "normal operation" the thermostat element 7 is in the position shown. The overpressure spring 21 has assumed its largest length. Accordingly, the bottom 11 of the thermostat element 7, or a radially projecting part 24 of the circumferential wall 12 bears on the step 23.

From this position, a temperature increase in the thermo- stat element causes an expansion of the pressure chamber 8. This expansion is caused in that the cavity 14 is re- duced. Thus, the actuating element 17 is pressed out of the thermostat element 7 in the direction of the radiator valve. The radiator valve is closed.

It may happen that with a closed radiator valve the room temperature continues to increase, for example due to in- tensive sun radiation or the body heat from several people staying in the room. This higher temperature, which is called overtemperature, causes a further pressure increase in the pressure chamber 8, which could, without further measures, cause the risk of damaging the thermostat ele- ment 7 or other parts. To avoid such damage, a further volume expansion is permitted in that the bottom 11 of the thermostat element 7 moves in the direction of the radiator valve under extension of the circumferential wall 12 against the force of the overpressure spring 21. A rela- tively small movement is sufficient for this movement of the bottom 21, as will be explained in connection with Fig. 2.

- 13 - Fig. 2a shows the volume expansion in the traditional case, which was practically limited to the volume expan- sion of the pressure chamber 8 through reduction of the volume of the cavity 14. With a given diameter of the cav- ity 14, for example, a movement a is required.

When now the volume expansion is caused in connection with the larger diameter, namely on the circumferential wall 12, merely a movement b is required. This movement b has the same relation to the movement a than the relation of the cavity 14 base with the base limiting the circumferential wall 12. The relation can easily amount to the factor 3 or more, particularly the factor 5 or more. When, for example, with a given thermostat valve element 7, a move ment of 9.2 mm is required, when the safety device is ex- plicitly concerned with pressing the actuating element 17 out of the thermostat element 7, the movement b is limited to a length of 1.6 mm, when the circumferential wall 12 is made to be deformable. The fact that the overpressure spring 21 is located in the area of the largest diameter of the thermostat element 7 in particular involves two ad- vantages: Firstly, it is avoided that a heat transfer to the actuating element 17 occurs via the overpressure spring 21. On the contrary, a heat, which is transferred to the thermostat element 7 via the overpressure spring 21, can very quickly be dissipated outwards. Secondly, the overpressure spring 21 acts in the area of the circumfer- ential wall 12, that is, the circumferential wall 12 can adopt the forces directly from the overpressure spring 21.

When the temperature drops again, the thermostat element 7 will move back to the initial position shown in Fig. 1.

For this purpose, the overpressure spring 21 must of - 14 - course be coordinated with the corresponding return spring.

The Figs. 3 to 8 show further embodiments of thermostat valve top parts, which in principle correspond to the em- bodiment shown in Fig. 1. Merely modifications and devia- tions will be considered.

With the thermostat valve top part shown in Fig. 3, the volume change of the pressure chamber 8 of the thermostat element 7 occurs in that the thermostat element 7 consists of two parts, namely a bottom part 25 and a top part 26, which are in contact with each other via a sliding sealing area 27. In the sliding sealing area is located an O-ring 28 or another sealing, which permits a displacement of the bottom part 25 in relation to the top part 26 against the force of the overpressure spring 21, when the pressure in the pressure chambers exceeds a certain amount, and a further movement of the actuating element 17 is no longer possible. Such a sliding sealing area 27 is possible in principle, as the movements to be performed by the bottom part 25 in relation to the top part 26 are relatively small. As suggested above, they are limited to the range from 1 to 2 mm or are even smaller.

Also in Fig. 4 a sliding sealing area 27 is provided.

Here, the sliding sealing area 27 has a somewhat different embodiment. The top part 26 has a deformable wall section 29, which is, for example, made of an elastomer material.

This wall section 29 bears on a supporting wall 30 of the bottom part 25. It is acted upon by the pressure in the pressure chamber 8. The larger the pressure in the pres- sure chamber 8 is, the more is the deformable wall part 29 - 15 - pressed against the supporting wall 30 of the bottom part 25. This increases the sealing effect with the pressure in the pressure chamber 8. Also here, merely small displace- ment movements between the bottom part 25 and the top part 26 are required, so that in practically all operating situations the tightness is ensured.

With the embodiment in Fig. 5, the expansion of the pres- sure chamber 8 is enabled in that the bottom of the ther mostat element 7 is made as a diaphragm 31, that is, a de- formable disk of an elastomer material. When the natural strength of the diaphragm 31 is not sufficient for the expected pressures, a support plate 32 may be provided, which bears on the diaphragm 31 during undisturbed peri oafs, that is, without overtemperature. The support plate 32 is kept in its position by the overpressure spring 21.

When the overpressure occurs in the pressure chamber 8, the support plate 32 is pressed downwards by the diaphragm 31, that is, in the direction of the radiator valve.

Also in the embodiment according to Fig. 6, merely the bottom is deformable. The thermostat element 7 has a bot- tom plate 33, which is pressed into its normal position by the overpressure spring 21. The bottom plate 33 is con nected with the circumferential wall 12 via a double bellows 34. When the temperature in the pressure chamber 8 increases, thus requiring a volume expansion, the bellows 34 is compressed, when the bottom plate 33 moves down- wards.

Fig. 7 is an embodiment, which substantially corresponds to the embodiment according to Fig. 1, the thermostat ele ment 7 being located upside down. Accordingly, the bottom - 16 plate 11 is here located on the front side 10 of the twist handle 5, and the front side 10 has an opening 35, through which the actuating element 17 is guided.

As the front plate 10 has a smaller diameter than the bot- tom plate 11, the overpressure 21 is made to be conical. A stop 36, which limits the largest deflection of the over- pressure spring 21 and thus the maximum movement of the front side 10, is located inside the thermostat element 7.

In the present case, it is made as a hollow cylinder.

Fig. 8 shows an embodiment similar to that in Fig. 6. Also here, the bottom plate 33 is connected with the circumfer- ential wall 12 of the thermostat element 7 via a bellows 34. However, here the bottom plate 33 is located com- pletely inside the thermostat element 7.

Fig. 9 shows a thermostat valve top part 1 with a remote sensor 40. The thermostat element 7 is located inside the remote sensor 40 and has the circumferential wall 12 with corrugation, so that the bottom 11 moves against the force of the overpressure spring 21 under expansion of the vol- ume of a part pressure chamber 8a, when the temperature in the part pressure chamber 8a exceeds a predetermined value. This value is reached as soon as the actuated valve is closed. Via a tube 41, the part pressure chamber 8a is connected with a part pressure chamber 8b, which is located in the thermostat valve top part itself. Via an ac- tuating element 17', which is located inside the part pressure chamber 8b, more precisely inside a bellows 42, which has the same function as the inner wall 15 according to Fig. 1, the pressure in the part chamber 8b acts upon the bottom of the bellows 42. The actuating element 17' - 17 could also be avoided. In the present case, it serves the purpose of keeping the free volume in the part pressure chamber 8b small.

It is common for all embodiments that, like traditional thermostat elements, they have an expansion area, whose deformation pushes the actuating element i7 out of the thermostat element 7 in the direction of the radiator valve and that additionally they have an expanding pres sure relief area, which permits a volume change of the pressure chamber outside a change of the expansion area.

The overpressure area can be made as a corrugated wall, as displaceable wall sections or a deformable bottom.

Changes, which can be made in similar ways, are of course also comprised by the basic idea of the invention.

In all cases, the additional advantage exists that with a thermostat element 7 with a flexible, large, bellows- shaped circumferential wall 12 the pressure chamber 8 can be more or less filled, compared with a traditional ther- mostat element, thus changing the amplification of the thermostat element 7. The amplification is the relation between the thermostat element 17 movement and the tem- perature change.

Claims

Patent Claims 1. Thermostat valve top part comprising a thermostat ele

ment provided with a pressure chamber, whose volume changes depending on the temperature, an actuating element interacting with an expansion area of the thermostat element, and a safety device, characterized in that the safety device has an expanding pressure relief area (12, 27, 31, 34) outside the expansion area (15).
2. Top part according to claim 1, characterized in that the actuating element (17) is inserted in a cavity (14) of the thermostat element (7), which is bordered by an inner wall (15), and the overpressure area is located on a wall (12), which borders the thermostat element (7) on the outside.
3. Top part according to claim 2, characterized in that the expanding pressure relief area is made on a circumferential wall (12) of the thermostat element (7).
4. Top part according to claim 3, characterized in that the expanding pressure relief area is formed by a corrugation of the circumferential wall (12) of the thermostat element (7).
5. Top part according to claim 4, characterized in that the corrugation on the circumferential wall (12) has a smaller number of waves (13) than a corrugation (16) in the expansion area.
6. Top part according to one of the claims 1 to 5, char acterised in that an overpressure spring (21) acts in the area of a largest diameter upon the thermostat element (7).
7. Top part according to claim 6, characterized in that the overpressure spring (21) is supported in a twist handle (5), in which the thermostat element (7) is lo cased.
8. Top part according to claim 6 or 7, characterized in that the overpressure spring (21) cooperates with a length limitation device (23, 36).
9. Top part according to claim 8, characterized in that the length limitation device (23) exists in the form of a stop in the twist handle.
10. Top part according to claim 8, characterized in that the length limitation device exists in the form of a stop inside the thermostat element.
11. Top part according to one of the claims 7 to 9, char acterised in that the overpressure spring (21) bears on the twist handle (5) from the radial inside.
12. Top part according to one of the claims 1 to 11, char acterised in that the expansion area and/or the ex pending pressure relief area have a sliding sealing area (27) with two mutually displaceable parts (25, 26) of the thermostat element (7). -
13. Top part according to claim 12, characterised in that in the sliding sealing area (27) a deformable wall section (29) of a part (26), which is acted upon by the pressure in the pressure chamber (8), bears on a supporting wall (30) of the other part (25).
14. Top part according to one of the claims 1 to 13, char acterised in that the thermostat element (7) has a de formable bottom (31, 33).
15. Top part according to claim 14, characterised in that the bottom (31) is made as a diaphragm.
16. Top part according to claim 14, characterised in that the bottom (33) has an edge area (34), in which it has a bellows shape.
17. Top part according to claim 16, characterised in that the edge area (34) is compressible, when the pressure in the pressure chamber (8) increases.
18. Top part according to one of the claims 1 to 17, char acterised in that the actuating element (17) is made of a poorly heat conducting material, particularly plastic, glass or ceramic.
19. Top part according to one of the claims 1 to 18, char acterised in that the actuating element has an actuat ing end, a heat isolating and/or heat reflecting pro tective plate being located between the actuating end and the thermostat element. - 21
20. Top part according to one of the claims 1 to 19, char acterised in that the pressure chamber is divided into two different partial pressure chambers (8a, 8b) hav ing a spatial distance from each other and being con nected with each other by means of a line (41), one partial pressure chamber (8b) comprising the expansion area and the other partial pressure chamber (8a! com prising the expanding pressure relief area (12).