GB2398621A

GB2398621A - Thermostat valve cap

Info

Publication number: GB2398621A
Application number: GB0412658A
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: 2004-08-25
Anticipated expiration: 2022-12-13
Also published as: GB2398621B; DE10162608B4; GB0412658D0; AU2002366848A1; CN100501627C; WO2003054650A1; CN1606722A; DE10162608A1

Abstract

Disclosed are a thermostat valve cap (1) and a method for adjusting the set point thereof. The inventive thermostat valve cap (1) comprises a thermostat element (7) provided with a pressure chamber (8) in which volume-adjusting means are arranged, and an actuating element (12) interacting with an expansion area of the thermostat element (7). External shape-modifying means modifying the shape of the pressure chamber (8) outside the expansion area from outside are used to keep the size of the thermostat valve cap as small as possible.

Description

Thermostat valve top part The invention concerns a thermostat valve top

part com prising a thermostat element provided with a pressure chamber, in which inner volume-changing means are located, and with an actuating element interacting with an expan- sion area of the thermostat element. Further, the inven- tion concerns a method for adjusting a desired value of a thermostat valve top part comprising a thermostat element provided with a pressure chamber, in which inner volume- changing means are located, which change the volume of the pressure chamber in dependence of a temperature.

Most radiator thermostats in residential and office build- ings are provided with such thermostat valve top parts.

The radiator thermostat valve itself is preloaded in the opening direction, so that a valve pin bears on the actu- ating element of the thermostat valve top part. At a low temperature, the pressure chamber in the thermostat ele- ment has its smallest volume, so that under the effect of the valve pin the actuating element can be pushed very far into the thermostat element. The valve is then completely open. When the temperature increases, the filling of the thermostat element expands, for example a gas or a liquid, in some cases also a wax filling, so that the volume of the pressure chamber expands. This will push the actuating element further in the direction of the radiator valve, thus closing the radiator valve more.

In order to change the desired value of the thermostat valve top part, it is known to displace the thermostat element, either in the direction of the radiator valve to set a low desired temperature value, or away from the ra- diator valve to set a higher desired temperature value.

This displacement usually occurs by means of a twist han- dle, which is fixed on a housing by means of a screw thread. Then the thermostat element can be fixed immedi- ately in the twist handle. However, it is also possible for the thermostat element to be located in an auxiliary device, which is displaced by the twist handle.

The displacement of the thermostat requires a certain di- mension of the thermostat valve top part. The thermostat valve top part must be so large that it can adopt all po- sitions of the thermostat valve.

However, it is endeavoured to keep the dimensions of a thermostat valve top part as small as possible, in order to avoid that the thermostat valve top part extends too far into the room. This could involve the risk of damages.

Further, usually an optically more attractive embodiment occurs, when the thermostat valve top part can be kept small.

The invention is based on the task of keeping the dimen- sions of the thermostat valve top part small.

With a thermostat valve top part as mentioned in the in- troduction, this task is solved in that external shape- changing means are provided, which, from the outside, change the shape of the pressure chamber outside the ex pension area.

With this embodiment, it is no longer necessary to dis- place the whole thermostat element. When a change of the desired value is wanted, the shape of the pressure chamber is changed, that is, the size of the thermostat element is reduced from the outside to press the actuating element further out of the thermostat element, or it is enlarged, so that the actuating element can penetrate further into the thermostat element. Changing the outer shape of the thermostat element can effect this outer volume change.

Thus, the thermostat element can be completely or partly compressed or expanded. This shape-changing means usually require less space than means, which are required for dis- placing the thermostat element.

It is particularly preferred that the outer shape-changing means act upon the whole surface of a cross-section face of the thermostat element. Thus, relatively small compres- sion or expansion changes of the thermostat element will be sufficient to cause an accordingly large volume change of the pressure chamber. In this case, a transmission ra- tio is utilized, which exists between the cross-sectional area of the thermostat and an active surface, via which the thermostat element acts upon the actuating element.

When, for example, the actuating element is inserted in the thermostat element in a cup-shaped cavity, which is supplied with a bellows wall, in which the thermostat ele ment is inserted, merely the cross-section of this cavity acts upon the actuating element. When, now, the shape of the pressure chamber is changed from the outside, the vol- ume of the pressure chamber itself, however, shall remain constant, this shape change causes that the actuating ele ment is pushed further out of the thermostat element or sinks further into the thermostat element. Thus, the shape change of the pressure chamber gives the actuating element a different starting position, from which it can act upon 1,. 4 _

the radiator valve. The thermostat valve top part is par ticularly provided for radiator valves. However, it can also be used with other temperature controlling devices, for example air-conditioning systems.

Preferably, the thermostat element has an outer circumfer ential wall, which is made to be able to change its length. Thus, a length change of the thermostat element as a whole is possible. The thermostat element can be com pressed, which means that the actuating element is pressed further out of the thermostat element. However, the ther- mostat element can also be expanded, which causes that the actuating element can be pushed further into the thermo- stat element.

It is particularly preferred that the outer circumferen- tial wall has a corrugation. A corrugation, that is, a bellows-shaped wall, is a particularly simple embodiment for making the circumferential wall able to change its length. The length changes are small. Thus, the corruga- tion is only stressed weakly with regard to bending. A corrugation on the outer circumferential wall of the ther- mostat element has the additional advantage that it ex- pands the surface of the thermostat element, which is in touch with the environment. This further improves the heat transition between the thermostat element and the environ- ment.

It is particularly preferred that the corrugation on the outer circumferential wall has a smaller number of waves than a corrugation in an expansion area formed by a cav- lty, into which the actuating element is inserted. Here, it is considered that the actuating stroke of the actuat - 5 - ing element is substantially larger than the required length change of the thermostat element. As the length changes of the thermostat element are small, a small num- ber of waves is sufficient. However, also the number of waves in the expansion area can be made smaller than was the case with the previous state of the art. Now, the ex- pansion area merely serves the purpose of actuating the actuating element. A safety or protection function at a too high temperature can be provided by the corrugation of the circumferential wall.

Preferably, the outer shape-changing means have a screw thread, by means of which a rotation of two parts will change a space available for the thermostat element. For example, two front sides of the space can be approached to each other or be removed from each other. When they are approached to each other, the thermostat element is com- pressed, so that - assuming a constant pressure chamber volume at constant temperature the actuating element is pressed further out of the thermostat element. An expan- sion of the space, however, will expand the thermostat element, so that the volume is kept constant, and the ac- tuating element is displaced further into the thermostat element.

Preferably, the screw thread is located between the ther- mostat element and a twist handle. When turning the twist handle, a part of the thermostat element, for example a bottom plate, is displaced to compress or expand the ther mostat element as a whole. However, the position of the thermostat does not have to be changed by this.

In an alternative embodiment, it is provided that an ex- tension of an actuating handle projects into a case, in which the thermostat element is located. Also this is a relatively simple possibility of letting the thermostat element compress or expand.

It is particularly preferred that the screw thread is lo- cated on the extension. The force transmission then occurs immediately between the screw thread and the thermostat element. There is no risk that transmission elements will deform in an impermissible manner, so that a precise defi- nition of the desired value is no longer ensured.

Preferably, the thermostat element has a distortion pro section. Thus, a turning of the twist handle or the actu- ating handle can be made without fearing that the thermo- stat element turns along.

Preferably, the thermostat element is supported by an overpressure spring. This embodiment has the advantage that the shape change of the thermostat element can also be used as an overpressure protection. An overpressure protection is required, when the radiator valve is already completely closed under the influence of the actuating element, and outside influences, for example a strong sun radiation or a large number of people in the room, make the temperature increase further. In this case, the higher temperature causes the pressure in the pressure chamber to increase so heavily that the risk of damaging the thermo stat element or other parts occurs. The actuating element cannot estop parse further, as it is prevented from a fur- ther movement by the closed radiator valve. In this case, however, the thermostat element can change due to its de - 7 formability, for example, it can change its length against the force of the overpressure spring. This length change is relatively small, as the length change acts over a large cross-sectional area. Thus, the length change occurs from the stroke of the length change and the crosssectional area of the pressure chamber.

The task is also solved by a method as mentioned in the introduction in that the shape of the pressure chamber is changed from the outside, outside the expansion area.

On condition of a constant temperature, the shape change of the pressure chamber causes that the volume conditions or volume divisions inside the pressure chamber must change. In fact, this change can only occur in that the actuating element is pushed further out of the thermostat element or in the opposite case - is pushed further into the thermostat element. This gives other starting posi- tions for the actuating element, in other words, a change of the desired value.

Preferably, the shape is changed by a small stroke, which acts upon a large cross-sectional area. Thus, large volume displacements can also be achieved with small strokes. The movement of the actuating element can be achieved even with relatively small strokes.

Preferably, the length of the thermostat element is changed. This is a relatively simple measure of changing the shape of the pressure chamber from the outside, so that the corresponding effects occur on the actuating ele- ment. - 8 -

In the following, the invention is described on the basis of preferred embodiments in connection with the drawings, showing: Fig. 1 a schematic cross-section through a first em- bodiment of a radiator valve thermostat top part Fig. 2 a second embodiment of a thermostat valve top part Fig. 3 a schematic view explaining the mode of opera tion A thermostat valve top part 1 serves the purpose of actu ating a radiator valve 2, shown schematically with dotted lines, and thus influencing an ambient temperature, which is heated by the radiator controlled by the radiator valve 2. The radiator valve 2 has an actuating pin 3, which is prestressed in the opening direction, that is, is pressed out of the radiator valve 2.

The thermostat valve top part has a housing 4, on which a twist handle 5 is arranged to be rotatable. The twist han- dle 5 is connected with the housing 4 via a bearing 6. A rotation of the twist handle 5 in relation to the housing 4 causes practically no extension of the thermostat valve top part 1.

Inside the twist handle 5 is located a thermostat element 7, which has a pressure chamber 8. In the pressure chamber 8 is located a fluid or gas filling, the filling having a heavily temperature dependent volume, that is, with a low temperature the volume of the filling in the pressure chamber 8 is smaller than with a higher temperature.

In a manner known per se, the thermostat element 7 has a cavity 9, which is surrounded by a bellows-shaped wall 10, also called "inner wall". The bellows-shaped wall 10 has a corrugation with a plurality of waves 11. In the cavity 9 is inserted an actuating element 12, which has an actuat- ing end 13, which again interacts with the operating pin 3. In other words, the operating pin 3 presses the operat- ing element 12 as far into the thermostat element 7 as possible. With a temperature increase in the pressure chamber 8, which causes a volume change of the filling in- side, the actuating element 12 must then be pressed fur ther out of the thermostat element 7. This again causes that the operating pin 3 is pressed further into the ra- diator valve 2, meaning that the radiator valve 2 is fur- ther throttled.

The thermostat element 7 has a bottom plate 14 and a front plate 15. The bottom plate 14 and the front plate 15 are connected with each other by means of a circumferential wall 16, which also comprises a corrugation 17 with a pre- determined number of waves 18. Thus, the circumferential wall 16 can change its length. When the length of the circumferential wall 16 is changed, the shape of the ther- mostat element 7 changes.

The lower end 19 of the circumferential wall 16 is re shaped radially outwards. This end 19 engages in a short inner thread 20 in the twist handle 5. This "inner thread" can also be made as a simple bearing surface with a prede- termined inclination. By means of a distortion protection, 10 the thermostat element 7 is protected against a rotation in relation to the housing 4.

When, now, the twist handle 5 is turned in the rotation bearing 6 in relation to the housing 4, the axial position of the bottom 14 in the twist handle 5 changes due to the transmission of the thread 20. However, the thread 20 has a relatively small pitch of, for example, 3 mm per rotation or less, particularly 1.5 mm per rotation or less.

Thus, the change of the bottom plate 14 position is ex- tremely small.

With the change of the bottom plate 14 position; maintain- ing the front plate 15 position, a change of the thermo stat element 7 shape is involved. When the bottom plate 14 is approached to the front plate 15, a constant volume in the pressure chamber 8 will require the actuating element 12 to be pressed further out of the thermostat element 7.

In this connection, a certain transmission ratio is util ised: in connection with a stroke, the bottom plate 14 acts upon the total cross-section of the thermostat ele- ment 7. In order to cause a corresponding volume equalisa- tion, the operating element 12 must then be moved out of the thermostat element 7 by a distance, which corresponds to a multiple of the stroke of the bottom plate 14. This multiple corresponds to the relation of the cavity 9 cross-section with the bottom plate 14 cross-section.

This will be explained by means of Fig. 3. It is assumed that the volume of the pressure chamber 8 is constant when displacing the bottom plate 14. This assumption is merely made to simplify the explanation. It is not required to - 11 adjust the desired value of the thermostat valve top part 1.

When the bottom plate 14 is moved by a small stroke a, this causes that a corresponding volume must be displaced in the cavity 9. However, this requires a movement of the actuating element 12 by a distance b. Depending on the re- lation between the extension of the bottom plate 14 and the cross-section of the cavity 9, this can give a trans mission of approximately the factor 3 or more, particu- larly 5 or more. This applies for the error-free case, that is, as long as the valve is not closed and the actu- ating element 12 can still move.

With traditional thermostat valve elements, a position change of the actuating element 12 of 0.2 mm/ C is antici- pated. Accordingly, with a desired value change in the range of 20 C, for example 10 to 30 C, a movement of 4 mm would be required. When, thus, the desired value, as has been the case until now, is changed by means of a dis- placement of the thermostat element 7, the thermostat ele- ment 7 would have to be displaced by 4 mm. The fact that now only the shape of the thermostat element 7 is changed, that is, the bottom 14 is displaced, causes that merely a stroke of 0.8 mm is required.

Thus, the required stroke a of the bottom 14 can be calcu- lated to cause a desired change of the starting position of the actuating element 12 and then, in dependence of the maximum permissible rotating angle of the twist handle 5, to select the pitch of the thread 20. - 12

Fig. 2 shows a modified embodiment, in which same parts have the same reference numbers. The radiator valve 2 and the actuating pin 3 are not shown.

The housing 4 has a case 22, in which the thermostat ele- ment 7 is located. In its front side 23, the twist handle has an extension 24, which engages in a threaded bore 25 in the case 22. The threaded connection between the exten- sion 24 and the case 22 also has a very small pitch of, for example, 3 mm per rotation or less, particularly 1 mm per rotation or less. The extension 24 bears on the front plate 15 of the thermostat element 7, the front plate 15 having certain rigidity here.

The bottom plate 14 of the thermostat element 7 is pressed in the direction of the front plate 15 by an overpressure spring 26, which is supported on the housing 4. However, in this case, the case has a projection 27, on which the lower end 19 of the circumferential wall or a radial pro jection of the bottom plate 14 bears, so that the bottom plate 14 can move downwards in the direction of the radia- tor valve 2, the movement away from the radiator valve 2, however, being limited.

A rotation of the twist handle 5 in relation to the hous- ing 4 and thus also in relation to the case 22 moves the projection 24 further into or out of the case 22. This movement of the projection 24 causes compression or expan- sion of the thermostat element 7, and thus a change of the shape of the pressure chamber 8, which - with constant volume - results in a movement of the actuating element 12. i

- 13 - When, during a shape change of the pressure chamber 8, the temperature in the pressure chamber 8 changes at the same time, this is of course also possible. Then, the adjust- ment of the desired value usually overrides a change of the control value.

The embodiment according to Fig. 2 requires a somewhat smaller torque, that is a smaller actuating force, for ad- justing the desired value than the embodiment according to Fig. 1.

In the embodiment according to Fig. 2, the possibility of changing the shape of the thermostat element gives an ad- ditional advantage: Imagining a situation, in which the radiator valve is completely closed, the actuating element 12 already being pushed as far as possible out of the thermostat element 7, the room temperature, however, in- creasing further, there is a risk of damaging the thermo- stat element 7, as the pressure in the pressure chamber 8 continues to increase. In the present case, however, the increase of the pressure in the pressure chamber 8 is possible without problems, as, with such a pressure increase the bottom plate 14 can be displaced against the force of the overpressure spring 26, thus causing a volume expan sion of the pressure chamber 8, which prevents a critical pressure increase in the pressure chamber 8. In this connection, it is particularly advantageous that the desired increase of the volume occurs already with a relatively small displacement movement of the bottom plate 14.

As the displacement movement of the bottom plate 14 is relatively small, both during the desired value adjustment and during the overpressure protection, it is sufficient - 14 - for the corrugation 17 of the circumferential wall 16 to have a smaller number of waves 18 than the corrugation of the inner wall 10.

Both cases involve the additional advantage that with a thermostat element 7 with a flexible, large, bellows- shaped circumferential wall 16, the degree of filling of the pressure chamber 8 can selected, compared with tradi- tional thermostat elements, thus changing the amplifica Lion of the thermostat element 7. The amplification is the relation between the movement of the actuating element 12 and the temperature change.

Claims

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

ment provided with a pressure chamber, in which inner volume-changing means are located, and with an actuat ing element interacting with an expansion area of the thermostat element, characterized in that external shape-changing means (5, 20; 24, 25) are provided, which, from the outside, change the shape of the pres sure chamber (8) outside the expansion area.
2. Top part according to claim 1, characterized in that the outer shapechanging means (5, 20; 24, 25) act upon the whole surface of a crosssection face of the thermostat element (7).
3. Top part according to claim 1 or 2, characterized in that the thermostat element (7) has an outer circum ferential wall (16), which is made to be able to change its length.
4. Top part according to claim 3, characterized in that the outer circumferential wall (16) has a corrugation (17).
5. Top part according to claim 4, characterized in that the corrugation (17) on the outer circumferential wall (16) has a smaller number of waves (18) than a corru gation in an expansion area formed by a cavity, into which the actuating element (12) is inserted. - 16
6. Top part according to one of the claims 1 to 5, char acterised in that the outer shape-changing means (5, 20; 24, 25) have a screw thread, by means of which a rotation of two parts (5, 14; 5, 22) will change a space available for the thermostat element (7).
7. Top part according to claim 6, characterized in that the screw thread (20) is located between the thermo- stat element (7) and a twist handle (5).
8. Top part according to claim 6, characterized in that an extension (24) of an actuating handle (5) projects into a case (22), which is located in the thermostat element (7).
9. Top part according to claim 8, characterized in that that the screw thread (25) is located on the extension (24).
10. Top part according to one of the claims 6 to 9, char acterised in that the thermostat element (7) has a distortion protection (21).
11. Top part according to one of the claims 1 to 10, char acterised in that the thermostat element (7) is sup ported by an overpressure spring (26).
12. Method for adjusting a desired value of a thermostat valve top part comprising a thermostat element pro vided with a pressure chamber, in which inner volume changing means are located, which change the volume of the pressure chamber in dependence of a temperature, characterized in that the shape of the pressure cham - 17 ber is changed from the outside, outside the expansion area.
13. Method according to claim 12, characterized in that the shape is changed by a small stroke, which acts upon a large cross-sectional area.
14. Method according to claim 12 or 13, characterized in that a length of the thermostat element is changed.