The present invention refers to a changeover valve.

Such valves allow to switch from one gas source to another gas source which serves as a reserve. See for example US 2,397,670.

US 4 648 427 A discloses a bistable two position valve which utilizes a valve mechanism that employs a valve operator that is pivoted about a point and includes a pair of outwardly extending port closures at an angle with respect to each other and each being operable to open and close a port in a housing. As the valve operator rocks about its pivot point, one or the other of the valve closures covers its corresponding port and thus alternately opens and closes that port to the flow there through of a gas or liquid.

Further, US 2 702 050 A discloses a valve having a conical-shaped core with means for releasing the gripping action of the core against the inner surface of the valve body to facilitate rotating the core to open and close passages between connections of the valve body.

In US 2 397 670 A, a changeover valve is described which includes means to prevent escape of pressure through any disconnected station on the system, without the need for auxiliary back-flow check valve devices. This is achieved by the use of a single pressure diaphragm and spring, which serve to Index a multi- lobed cam with respect to the desired plurality of Inlet valves, by means of an appropriate ratchet gear.

For the changeover from the active gas cylinder to the reserve gas cylinder the user usually has to rotate a knob from one end position to another end position. This requires, for example, a rotation of 180°. It might be the case that the user stops the rotation before the full 180°.

An object of the invention is to provide a changeover valve that deals with the situation that a user does not perform a full rotation required for a changeover. The object is achieved with a changeover valve comprising two inlets, an outlet, a switch mechanism, a knob, and a push mechanism, wherein the switch mechanism allows to connect one of the two inlets to the outlet, wherein the knob is being rotatable around an axis with two end positions, wherein the knob and the switch mechanism are coupled to another, wherein a rotation of the knob causes the switch mechanism to switch from a connection between one of the two inlets and the outlet to a connection between the other of the two inlets and the outlet, wherein the knob and the push mechanism are coupled to each other, and wherein in case the knob is located between the two end positions, then the push mechanism pushes the knob to one of the two end positions.

The rotation of the knob around an axis forces the switch mechanism to changeover from one inlet to the other inlet. Especially, the switch mechanism changes the connection between outlet and one inlet to the other inlet if the knob is rotated from one end position to the other end position. Hence, the two end positions of the knob are associated with the two possible connections between the outlet and one of the two inlets. The push mechanism pushes the knob to one of these two end positions if a rotation of the knob by the user does not reach an end position. Hence, the push mechanism ensures that the knob is always in one of the end positions.

The following embodiments refer to the push mechanism.

In an embodiment, the push mechanism pushes the knob back to the end position if the rotation is less than the half of the necessary rotation between the two end positions. Further, the push mechanism pushes the knob forward to the other end position if the rotation caused by the user is greater than the half of the necessary rotation.

According to an embodiment, the push mechanism comprises a contour element with a contour, a cover with a counter contour, and a push spring, wherein the knob and the cover are coupled to another so that a rotation of the knob rotates the cover and vice versa, wherein the contour element and the cover are rotatable with respect to another around the axis and are moveable with respect to another along the axis, wherein a relative movement between the contour element and the cover along the axis compresses the push spring, and wherein the contour and the counter contour are designed and arranged with respect to another so that a rotation between the contour element and the cover causes an axial movement between the contour element and the cover and vice versa.

An embodiment provides that the contour and the counter contour are designed and arranged with respect to another so that two relative positions between the contour element and the cover are given in which a compression of the push spring by the contour element and/or the cover is minimal.

In this embodiment, the push mechanism comprises two elements (contour element and cover) and a push spring. They are designed and arranged with respect to another that a rotation between the elements causes a compression of the spring. Hence, the force of the spring can rotate the elements relative to another. The surfaces of the two elements have a contour and a counter contour which are associated with two orientations with a minimal compression of the spring. These orientations belong to the two end positions of the knob. Between the two orientations, the spring is compressed to a different degree. Hence, the force of the spring will move the knob to one of the two end positions as they are associated with the minimum of compression.

According to an embodiment, in case the knob is located between an end position and a middle between the end position and the other end position, then the push mechanism pushes the knob back to the end position, and wherein in case the knob is located between a middle between an end position and the other end position and the other end position, then the push mechanism pushes the knob forward to the other end position.

The following embodiments refer to the switch mechanism that performs the actual changeover between the two inlets.

An embodiment provides that the two inlets are connected by a respective passage to a chamber, wherein the outlet is connected to the chamber, wherein the switch mechanism comprises an axe, two levers, and two lever springs, wherein the axe is being rotatable around the axis, wherein the axe comprises a disk with a structured surface, wherein each of the two levers is associated with one of the two inlets, wherein each of the two levers opens or closes with a first end the passage of the associated inlet to the chamber, and wherein the structured surface of the disk and the two levers are such designed and arranged with respect to another so that the structured surface depending on a rotational position of the disk around the axis rests on a second end of one of the two levers and compresses by the second end one of the two lever springs.

According to an embodiment, the structured surface rests depending on an axial position of the disk along the axis on second ends of both of the two levers and compresses by the second ends both of the two lever springs. Here, the disk opens both inlets if the gas pressure of the active inlet becomes too small. This embodiment allows the switch mechanism to open automatically the reserve inlet if the gas pressure at the active inlet falls below a certain level. The gas pressure at the outlet in this case is preferably lower than the gas pressure if the active inlet provides enough gas.

An embodiment provides that the chamber is partially encompassed by a diaphragm, wherein the diaphragm and the axe are mechanically coupled to another, and wherein an axial position of the disk along the axis depends on a pressure within the chamber. In this case, the diaphragm moves the axe. Due to this, a drop of pressure in the chamber will pull the axe and by this the disk downwards. This will cause the opening of both inlets.

The following embodiments refer to an indicator mechanism. It indicates whether the active inlet provides enough gas or whether either no gas is present or the automatic switch to the reserve inlet has happened.

According to an embodiment, the changeover valve further comprises an indicator, wherein the indicator is being rotatable around the axis, wherein the knob comprises two windows, and wherein the indicator and the two windows are such designed and arranged with respect to another, so that parts of the indicator being visible through the windows.

An embodiment provides that the changeover valve further comprises a torsion spring, wherein the axe is being movable along the axis, wherein the indicator and the torsion spring are designed and arranged with respect to another, so that a force of the torsion spring rotates the indicator around the axis, and wherein the indicator and the axe are such designed and arranged with respect to another, so that at one position of the axe along the axis, the axe interacts with the indicator and hampers a rotation of the indicator around the axis. In an embodiment, the position of the axe depends on the pressure within the chamber. If the pressure drops and the axe moves downwards, the axial movement of the axe will allow the rotation of the indicator. Hence, a different section of the indicator will be visible through the knob.

In detail, there is a plurality of possibilities to design the changeover valve. Reference is made to the following description of a preferred embodiment in conjunction with the drawing.

It shows:

Fig. 1 : a sectional drawing of an embodiment of the changeover valve,

Fig. 2: an exploded view of some components of the valve of Fig. 1 ,

Fig. 3: a) and b) views of two different embodiments of a knob,

Fig. 4: part of a sectional drawing of the valve of Fig. 1 ,

Fig. 5: a) and b) enlarged sectional drawings of the upper end of the axe in two different situations,

Fig. 6: a view of an embodiment of the indicator

Fig. 7: a) and b) two views of the valve of Fig. 1 with two different positions of the indicator,

Fig. 8: a sectional drawing of a cut through the axe and the middle element,

Fig. 9: a) and b), a view of the semi-transparent cover and a sectional drawing of the cover,

Fig. 10: a view at the contour element,

Fig. 11 : a sectional view of the cover and the contour element, and

Fig. 12: a sectional view of the enlarged upper part of the valve of Fig. 1. The changeover valve shown in Fig. 1 and Fig. 2 is a pressure regulator that adjusts an unregulated gas pressure of a - not shown here - cylinder with liquified petroleum gas (LPG) to an adjusted pressure value.

The unregulated gas pressure can change according to the temperature of the LPG. A typical range is between 0,3 bar and 16 bar. The adjusted gas pressure is, e.g., 0,5 bar when the gas cylinder is in active condition and 0,3 bar when it is in reserve condition. When such a reserve condition with just a small amount of gas within the cylinder is reached, the valve allows the user a manual changeover from one gas cylinder to a different gas cylinder. Both gas cylinders (active and reserve cylinder) are connected via the changeover valve to one gas appliance. Further, if the gas pressure of the active gas cylinder becomes too low, then the valve will open the reserve gas cylinder.

Both figures Fig. 1 and Fig. 2 will be discussed simultaneously for an overview description of the entire valve. Details will be discussed subsequently with the following figures.

The changeover valve fulfills different functions:

- connecting one of two gas cylinders at the two inlets to one appliance via one outlet,

- adjusting the gas pressure to a set value,

- allowing a changeover from the active gas cylinder to the reserve gas cylinder by the user,

- automatically switching the supply to the reserve cylinder if the active cylinder runs empty, and

- indicating the status of the active gas cylinder.

For the changeover function, a user has to turn the knob 4 of the changeover valve from one end position to another end position. If the user does not perform the full rotation, a push mechanism of the inventive valve will either bring the knob 4 back to the starting position or will perform the missing part of the rotation towards the other position. If the other position has been reached, the actual switch from one inlet to the other inlet will be done. Hence, the push mechanism ensures that the valve is always in one of two situations. Based on Fig. 1 and Fig. 2, the components of the valve will be described and some basic information concerning the functions of the valve and the associated mechanisms will be given:

The valve has two inlets 11, 12 and one outlet 2. The change from one, i.e. active, inlet to the other, i.e. reserve, inlet 11 , 12 is initiated by a rotation of the knob 4 around the longitudinal axis 60. This is done mechanically by a user. For the actual changeover, the valve comprises a switch mechanism 3 (for more details, see Fig. 4).

Both inlets 11 , 12 are connected via an associated passage 110, 120 to a chamber 1 within the housing 10 of the valve. This chamber 1 is limited at one - the upper - side by a diaphragm 9. At the outside of the chamber 1 , there is a cover 13 which is here made out of a metal alloy, e.g. Zamak. Between the cover 13 and the outer side of the diaphragm 9 a diaphragm spring (also called adjustment spring) 90 is located which pushes the diaphragm 9 towards the chamber 1. If the pressure in the chamber 1 is greater than a certain value, then the diaphragm 9 will act against the diaphragm spring 90 and will move upwards. As the diaphragm 9 and the axe 6 are connected to each other, the axe 6 will also move upwards. As a result of the upward movement of the axe 6, the lever 30 rotating on its axis 33 throttles or closes the gas passage hole 110 and consequently reduces the pressure in the chamber 1 (compare Fig. 4)

The characteristics of the diaphragm 9 and of the diaphragm spring 90 allow to set the value of pressure the gas will have after leaving the chamber 1 through the outlet 2. This is the regulation or adjustment function of the valve.

On top of each of the two passages 110, 120 rests a sealing punch 32 that is connected to a lever 30 (compare Fig. 4). Associated with each lever 30 is also a lever spring 31 that pushes the respective lever 30 towards a closing position for the associated passage 110, 120. The force of the lever springs 31 is sufficient to ensure that, independent of the pressure given at the inlets 11, each passage 110, 120 remains closed. In order to open one of the two passages 110, 120, it is necessary for the pressure in the chamber 1 to be reduced so that the diaphragm 9, pushed by the spring 90, in its descent pulls the disk 62 downwards until it gets into contact with the respective lever 30 and forces the lever 30 to open the associated passage 110, 120. The switch mechanism 3 allows the changeover from one of the two inlets 11 , 12 to the other by acting at the levers 30. Which of the two levers 30 is activated and, thus, which inlet 11, 12 is connected to the outlet 2 depends on the position of the disk 62 that is connected to the axe 6.

The disk 62 activates one lever 30 while de-activating the other lever 30. The disk 62 is rotated by a rotation of the axe 6. If the axe 6 and, consequently, the disk 62 are rotated, the switch from the active inlet to the reserve inlet happens. Thus, the reserve inlet becomes the active inlet.

In the shown embodiment, the knob 4 and the middle element 7 are mechanically coupled to another so that a rotation of the knob 4 rotates the middle element 7 around the axis 60. Further, the middle element 7 transfers the rotation to the axe 6 (compare Fig. 8). The rotation axis 60 is here the longitudinal axis of the axe 6. Thus, the user can rotate by the knob 4 the axe 6 and switch from one inlet to the other inlet of the two inlets 11 , 12.

The knob 4 has two end positions associated with the connection of one of the two inlets 11, 12 to the outlet 2. The push mechanism 5 takes care of the case that the force acted by a user on the knob 4 does not correspond to the force required for the full rotation from one end position to the other end position. The push mechanism 5, thus, pushes the valve to one of the two end positions: either back to the current end position or forward to the desired end position (compare also Fig. 5 and Fig. 9 - Fig. 12).

The push mechanism 5 comprises a contour element 51 , a push spring 52, and a counter contour 130 which here belongs to the inner side of the cover 13 (compare Fig. 9, Fig. 11 and Fig. 12).

The middle element 7 and the contour element 51 are connected to another in order to exchange rotations around the axis 60. The push spring 52 is arranged in the shown embodiment coaxially within the diaphragm spring 90. The contour element 51 and the counter contour 130 translate a vertical movement of the contour element 51 along the axis 60 into a rotation around this axis 60 and vice versa. The vertical movement compresses the push spring 52 whose force is directed along the axis 60. Hence, the force of the push spring 52 will cause a rotation of the contour element 51 and the middle element 7 around the axis 60. The contour element 51 and the counter contour 130 are such designed with regard to another that there are two positions with a minimal compression of the push spring 52 and an increasing compression between these two positions. These two positions are associated with the two end positions of the knob 4. By this, the push spring 52 forces - in the shown embodiment - the valve to one of the two end positions. Hence, the knob 4 will always be in one of the two end positions and one of the two inlets 11, 12 will be connected to the outlet 2. Details will be explained in the following.

The valve gives the user also a clear indication concerning the status of the cylinder (empty or with remaining liquid gas) of the gas cylinder connected to the active inlet.

For this indication function, e.g. two different colors are used: red and green. The color green indicates that due to the amount of gas given by the active cylinder, the gas pressure at the outlet 2 exceeds a first pressure value, e.g. 0,5 bar. The color red indicates that there is either no gas or that the gas pressure is below than a second pressure value, e.g. 0,3 bar.

For this indication function, the knob 4 comprises two windows 40 covered by two pieces of transparent glass 41. Through them, a rotatable indicator 80 within the dome shaped knob 4 is visible that belongs to an indicator mechanism 8 of the valve. The indicator 80 has areas with different colors, e. g. green and red for indicating that there is gas at the selected inlet 11, 12 or not. Here, one color is associated with gas having a pressure above one first value and the other color is associated with the case that the gas pressure at the selected inlet 11 , 12 is lower than a second value lower than the first value. The values are 0,5 bar and 0,3 bar, respectively. Hence, the user can see whether there is gas or not at the selected inlet 11, 12. For example, a green field indicates a gas pressure above 0,5 bar and a red field indicates no gas pressure or a pressure below 0,3 bar.

The indicator mechanism 8 comprises the mentioned indicator 80 which has an asymmetric design (compare Fig. 6 and Fig. 7) and which can be rotated around the axis 60. Further, there is a torsion spring 81 in interaction with the indicator 80. Hence, the rotation of the indicator 80 can compress the torsion spring 81 and the force of the torsion spring 81 can rotate the indicator 80. The indicator 80 and the middle element 7 interact with another based on the ribs 71 at the upper side of the middle element 7. The axe 6 reaches with its upper end through the middle element 7 and through the indicator 80. As the axe 6 can be moved along the axis 60, the indicator 80 comes in contact with different sections of the axe 6. These sections either hamper or enable a rotation of the indicator 80 around the axis 60 (details will be discussed with regard to Fig. 5).

There are two causes for a rotation of the indicator 80:

1) A rotation of the knob 4 is followed by a rotation of the middle element 7 which rotates the indicator 80. Hence, the indicator 80 follows the movement of the windows 40 of the knob 4.

2) The position of the axe 6 along the axis 60 depends on the pressure at the selected inlet 11, 12. Due to this, the indicator 80 will rotate with respect to the widows 40 and a different section - with a different color - of the indicator 80 will be visible.

Details of the changeover valve will be discussed based on the following figures.

In Fig. 3 a) and b), two different embodiments of a changeover valve are shown. This allows to explain the changeover and the indication function (compare Fig. 7).

Both embodiments of the valve have two inlets 11, 12 and one outlet 2 forming the letter T. The knob 4 has in both embodiments two windows 40 which enclose either the angle of 90° (Fig. 3 a)) or the angle of 180° (Fig. 3 b)).

In the embodiment of Fig. 3 a), the locations of the windows 40 indicate which inlet (here the left one, 12) is connected to the outlet 2. An additional arch at the knob 4 symbolizes the connection. A changeover from one inlet (here 12) to the other inlet (here 11) requires a rotation of 90°.

In the embodiment of Fig. 3 b), the windows 40 are aligned along an axis in the middle between the inlets 11, 12 and, thus, above the outlet 2. Here, a mark at the left side of the knob 4 indicates that inlet 12 is connected to the outlet 2. Changing from the active inlet 12 to the reserve inlet 11 requires a rotation of 180°. Fig. 4 shows how the switch mechanism and the pressure regulation work.

Shown is one of the two levers 30 with the associated passage 110 within the housing 10. The passage 110 connects one inlet 11 (compare Fig. 1) to the chamber 1. The lever associated with the other inlet 12 has the identical design. One side of the chamber 1 is given by a flexible diaphragm 9. At the back - and here also upper - side of the diaphragm 9 rests the diaphragm spring 90 allowing to adjust the value of the pressure of the gas leaving the output 2.

The shown lever 30 can be tilted around the rotation axis 33. A first end 301 of the lever 30 rests on the lever spring 31. A second end 302 rests via a sealing punch 32 on the passage 110.

The force of the lever spring 31 closes the passage 110 irrespective of the gas pressure present at the inlet 11 that is connected to the passage 110. Hence, the sealing punch 32 closes the passage 110 tightly. If the pressure in the chamber 1 is reduced, the diaphragm 9 moves downwards pulling the disk 62 downwards. The disk 62 forces the first end 301 of the lever 30 downwards and, thus, the second end 302 upwards. By this, the passage 110 is opened. The disk 62 at the lower end of the rotatable axe 6 is located above the first ends 301 of both levers 30. By the asymmetric design of the surface of the disk 62, it interacts differently with the levers 30, thus, activating one while deactivating the other.

Here, the axe 6 is rotated towards a position so that the disk 62 pushes the first end 301 of the activated lever 30 downwards against the force of the level spring 31. Hence, less pressure acting at the second end 302 is required for opening the passage 110. The lever of the other passage - not shown here - is not pushed downwards and the associated lever spring of the other inlet closes the passage.

In case that the active gas cylinder runs empty, the valve automatically opens the connection to the reserve gas cylinder. In this case both passages 110, 120 are open.

This opening happens this way: When the gas pressure of the active gas cylinder falls below the second pressure value (e.g. 0,3 bar), then the diaphragm 9 starts moving downwards. The axe 6 passes through a central opening of the diaphragm 9 and is mechanically coupled to the diaphragm 9. Hence, due to the downward movement of the diaphragm 9, the axe 6 will also move downwards. As the disk 62 of the axe 6 is located above both levers 30, the disk 62 will contact not only the lever 30 of the active inlet but also the lever 30 of the reserve inlet. Hence, the passage of the inlet connected to the reserve gas cylinder will open.

The lever 30 has on its upper side directed towards the disk 62 a kind of elevation that moves the axe 6 along the axis of rotation 60. This is used for the indicator mechanism 8 explained with regard to Fig. 5 a) and b).

In Fig. 5 a) and b) the upper end of the axe 6 is shown in two different situations: In Fig. 5 a) the end of axe 6 is at a higher position than in Fig. 5 b). Due to this, a nose 61 at the upper end of the axe 6 is either in form fit with the inner surface of the indicator 80 (Fig. 5 a)) or is not as it is below the indicator 80 (Fig. 5 b)).

The indicator 80 is connected to the torsion spring 81 so that the force of the torsion spring 81 and the rotation of the indicator 80 around the axis 60 are coupled to another. If the axe 6 is pushed upwards along the axis 60, then the nose 61 will hamper a rotation of the indicator 80 (Fig. 5 a)). If the axe 6 moves downwards - here in the direction of the gravitational force - along the axis 60 (Fig. 5 b)), then the torsion spring 81 can act on the indicator 80 and rotate it around the axis 60. Due to the rotation of the indicator 80, a different section of the indicator 80 will become visible in the window 40 of the knob 4 (compare Fig. 3).

As the movement of the axe 6 along the axis 60 is affected by the pressure of the gas at the activated inlet 11 , 12, a change of the pressure becomes clearly visible to the user.

Fig. 6 shows the upper side of the indicator 80 that is partially visible under the windows 40 of the knob 4 to the user.

There are four sections for indicating the pressure of the gas supply. The sections have for example the following sequence of colors: red, green, red, and green. Green indicates that the gas pressure is higher than a first pressure value (e.g. 0,5 bar) and red indicates that there is no gas present or the gas pressure is below a second pressure value (e.g. 0,3 bar). In the shown embodiment, the second pressure value is smaller than the first pressure value.

The indicator 80 is asymmetric with a ring-like part rounded at the outer side. This part is limited by two rather two flat edges (here at the top and at the right side) that enable to stop a rotation of the indicator 80 around the axis of rotation (here highlighted by the crosshair). This will be discussed with reference to the following Fig. 7.

By Fig. 7 a) and b) the indicator mechanism 8 is shown.

In Fig. 7 a) and Fig. 7 b), the indicator 80 has two different positions around its axis of rotation. This axis is also the axis 60 of rotation of the knob 4.

The middle element 7 comprises ribs 71 at its upper surface directed towards the indicator 80 and - here - reaching out of the plane of projection and being located at different positions of the rotational path of the indicator 80 (compare Fig. 2). The torsion spring 81 rotates the indicator 80 until an edge of the indicator 80 reaches one of the ribs 71 of the middle element 7 and is stopped. Thus, the ribs 71 limit the rotation of the indicator 80.

The limitation of the rotation by the position of the ribs 71 is in such a way that the indicator 80 will rotate exactly one of its sections. This can be seen, for example, by the section under the window 40 at the left side of the indicator 80: In Fig. 7 a), the last but one section is below the window 40. In Fig. 7 b) the last section is under the window 40. The same holds for the other window. As neighboring sections have different colors (green and red), the rotation of the indicator 80 will show that a change of the gas pressure has happened.

Fig. 8 shows the connection between the middle element 7 and the axe 6.

The middle element 7 has a central opening through which the axe 6 reaches. The outer contour of the axe 6 and the contour of the opening of the middle element 7 are designed with regard to another so that a form fit is given concerning a rotational movement. Hence, if the middle element 7 is rotated, the axe 6 will be rotated and vice versa.

The form fit nevertheless allows a movement of the axe 6 along the axis of rotation 60 (compare Fig. 5 a) and b)). Fig. 9 a) and b) show the cover 13 with its counter contour 130 used for the push mechanism 5.

At the upper end of the cover 13, the counter contour 130 is located which is directed towards the upper surface of the contour element 51 (compare Fig. 1 and Fig. 2).

The counter contour 130 comprises two depressions which are opposite to each other. The contour element 51 is located within the cover 13 and, thus, below the counter contour 130. Depending on the relative orientation between the contour element 51 and the cover 13, the depressions will push the contour element 51 downwards and, thus, against the force of the push spring 52. The depressions are associated with the maximal displacement caused by the interaction between the counter contour 130 and the contour 510 of the contour element 51.

Fig. 10 shows an embodiment of the contour element 51 with the contour 510 at its upper end. This contour 510 comes into contact with the counter contour 130 of the cover 13.

The contour element 51 has two regions with a reduced height and an identical design. The regions have a form similar to the letter w and are symmetrical with respect to their middle axis. In the middle of each region is top elongation that has less height than the rim of the contour element 51 between the two regions. From the sides of each region, there is a recess and an inclination reaching to the top elongation. Hence, the regions can be described by the following sequence: end of region, recess, inclination to top elongation.

When the contour element 51 is arranged under the cover 13, then the two depressions of the counter contour 130 (see Fig. 9) are located above the mentioned regions of the contour element 51. Considered may be the case that a rotation of 90° is required for the change from one end position of the knob 4 to the other end position.

If the user rotates the knob 4 for less than 45° - i.e. less than half of the required rotation - away from one end position, then the push mechanism 5 will turn the components backwards to this end positions and the force of the push spring 52 will push the knob 4 back to end position (compare Fig. 12). If the rotation caused by the user is greater than 45° - i.e. more than half of the required rotation then the push mechanism 5 will rotate the knob 4 to the other end position.

The interaction between the counter contour 130 of the cover 13 and the contour 510 of the contour element 51 is shown by Fig. 11.

The depression of the counter contour 130 is above one of the two mentioned regions of the contour 510. To the left of the depression, the contour 510 has a rising slope to the top elongation in the middle of the region (compare Fig. 10). Hence, if the contour element 51 is rotated around the axis 60, then the depression of the cover 13 will push the contour element 51 downwards and compress the push spring 52.

Comparing figures Fig. 9 - 11 , it becomes obvious that there are two positions with a minimal compression of the push spring 52. This can also be seen in Fig. 12.

In Fig. 12 the upper part of the changeover valve of Fig. 1 is shown.

The depression of the counter contour 130 is above a depressed region of the contour 510 of the contour element 51. If the knob 4 is rotated, the contour element 51 will follow and will compress - due to the contact with the counter contour 130 - the push spring 52. If the user stops the rotation before reaching the other end position of the knob 4, then the push spring 52 will force the contour element 51 upwards. Due to the matching between the contour 510 and the counter contour 130, this movement will be translated into a rotation of the contour element 51 around the axis 60. Thus, the axe 6 will either be rotated back to the end position or to the other end position. Thus, even an insufficient rotation of the knob 4 by the user will end at one of the two end positions. List of reference signs

Chamber

Outlet

Switch mechanism

Knob

Push mechanism

Axe

Middle element

Indicator mechanism

Diaphragm

Housing

Inlet

Inlet

Cover

Lever

Lever spring

Sealing punch

Rotation axis

Window

Transparent glass

Contour element

Push spring

Axis

Nose of axe

Disk of axe

Structured surface of disk

Rib at the surface of the middle element

Indicator

Torsion spring

Diaphragm spring

Passage

Passage

Counter contour of cover First end of lever Second end of lever Contour of contour element