Sauna stove and method for momentarily increasing the heat transfer of a sauna stove

Abstract

The invention relates to a sauna stove (10) including a frame (12), a stone space (14) including a thermal mass capable of being heated to a temperature of 200-700 °C and of evaporating water dispensed into the stone space (14), a flow channel (20) with a first opening (21) outside the frame (12) and a second opening (22) inside the frame (12) in the stone space (14), and a valve (30) configured to limit the flow of a fluid in the flow channel (20), The valve (30) is configured to open under the action of the pressure of the water evaporating in the stone space (14), which allows water vapour to flow in the flow channel (20) from the second opening (22) to the first opening (21) and air from outside the frame (12) to flow from the first opening (21) to the second opening (22), through the stone space (14) and back outside the frame (12), and the valve (30) is configured to close automatically in the absence of a pressure of evaporating water. The invention also relates to a method for momentarily increasing the heat transfer of a sauna stove (10).

Description

[0001] SAUNA STOVE AND METHOD FOR MOMENTARILY INCREASING THE HEAT TRANSFER OF A SAUNA STOVE

[0002] The invention relates to a sauna stove including

[0003] - a frame,

[0004] - a stone space including a thermal mass capable of being heated to a temperature of 200-700 °C and of evaporating water dispensed into the stone space,

[0005] - a flow channel with a first opening outside the frame and a second opening inside the frame in the stone space, and

[0006] - a valve configured to limit the flow of a fluid in the flow channel .

[0007] The invention also relates to a method for momentarily increasing the heat transfer of a sauna stove.

[0008] A sauna stove in what is known as a Finnish sauna includes a stone space that is filled with heat-retaining stones or some other heat-retaining mass, such as ceramic material. The mass in the stone space is typically heated to a temperature of around 200-700 °C in operation. The water dispensed into the stone space of the sauna stove in operation thus evaporates quickly and forms vapour, or steam, which mainly rises upwards out of the stone space and spreads into the room. The hot stone space of the sauna stove simultaneously also heats the air in the sauna room, typically to a temperature of around 60-120 °C, mainly by natural convection.

[0009] Typically, the structure of a sauna stove is designed so as to allow air to be conducted through the stone space. Nevertheless, the air flow through the stone space is poor in sauna stoves based on natural convection.

[0010] One problem with sauna stoves according to the prior art is the poor sauna steam experience. If there is no air flow through the hot stone space, there is no "surge" of steam, i.e. the hot steam and the air do not leave the sauna stove quickly enough. Furthermore, when the sauna stove is used both to heat the air in the room and to form a hot stone space used for the production of steam, there is hardly any way to control the intensity of the steam, as the temperature of the stone space directly affects both the intensity of the steam and the temperature in the room. There is thus no way of controlling the intensity of the steam without affecting the temperature of the room at the same time.

[0011] Sauna stoves are known in the prior art that include a fan, wherein the fan blows air through the sauna stove and thereby momentarily increases the transfer of heat to the sauna room by forced convection. This is mainly intended to accelerate the heating of the sauna room in the initial stages of heating. There is, however, the further problem with this type of sauna stove that it is not able to synchronize this increase with a throwing of water onto the hot stones, i.e. so that the increase is simultaneous with the dispensing of water into the stone space by the user. Sauna stoves according to the prior art that are equipped with a fan are therefore not able to improve and control the sauna steam experience of the user. In addition, a forced convection produced by a fan complicates the design of the sauna stove.

[0012] The object of the invention is to provide an improved sauna stove and an improved method that can improve and regulate the intensity of sauna steam. The characteristic features of a sauna stove according to the invention are set out in claim 1, while the characteristic features of a method according to the invention are set out in claim 15. A sauna stove according to the invention includes a frame, a stone space including a thermal mass capable of being heated to a temperature of 200-700 °C and of evaporating water dispensed into the stone space, a flow channel with a first opening outside the frame and a second opening inside the frame in the stone space, and a valve configured to limit the flow of a fluid in the flow channel. The valve is configured to open under the action of the pressure of the water evaporating in the stone space, which allows water vapour to flow in the flow channel from the second opening to the first opening and air from outside the frame to flow from the first opening to the second opening, through the stone space and back outside the frame, and the valve is configured to close automatically in the absence of a pressure of evaporating water.

[0013] The flow channel of the sauna stove can thus be configured to be opened synchronously in connection with the throwing of water into the stone space to produce sauna steam, whereby the intensity of the sauna steam can be increased by controlling the flow of air through the stone space at the moment that water is thrown into the hot stone space.

[0014] As the water dispensed into the stone space turns into water vapour, its volume increases significantly, and this increases the pressure inside the stone space. The thus created pressure opens the valve in the flow channel, which lets air into the stone space, which flows through the stone space. The flow of air transports energy into the sauna room and simultaneously increases the intensity of the sauna steam and the potency of the sauna steam experienced by the user. When the pressure increase caused by the water dispensed into the stone space ceases, the valve closes automatically and again limits the flow of a fluid in the flow channel. When the valve is closed, the air in the closed flow channel and stone space is heated to the temperature of the stone space, so that when the valve is opened again in connection with the throwing of water into the stone space, the air flowing through the flow channel pushes the heated air out of the stone space, thus producing a sauna steam effect that is experienced as pleasantly potent by the user .

[0015] In other words, the valve is configured to open when the steam pressure in the stone space exceeds a selected limit value, and the valve is configured to close when the steam pressure drops below a selected limit value.

[0016] The valve referred to here does not have to be completely airtight, but rather the valve limits the flow of a fluid by preferably at least 90% in the closed position compared to the open position.

[0017] Preferably, the air from outside the frame can flow from the first opening to the second opening by natural convection. This makes it possible to influence the air flow in a sauna stove based on natural convection, in which the air flow through the stone space is typically poor.

[0018] Any solution according to the prior art can be used to heat the stone space. The stone space can be configured to be heated by resistors or by burning wood or gas or a combustible liquid, such as oil, or by the friction generated by an electrically driven turbine. It is thereby possible to produce a desired temperature in the stone space.

[0019] The stone space can be partially enclosed in such a manner that the frame of the sauna stove covers at least 50%, preferably at least 80%, of the stone space. In other words, at most 50 %, preferably at most 20 %, of the surface area of the edges of the stone space is thus visible from outside the sauna stove. This makes it easier to maintain a desired temperature in the stone space.

[0020] The sauna stove can additionally include a cover over the stone space in which an opening of a selected size is arranged for the dispensing of water. This makes it possible to store heat in the stone space during operation better than to date, which enables an improved control of the temperature of the stone space. The stone space can also be thermally insulated and include a cover that is closed when the sauna is not in use to keep the heat in the stone space.

[0021] An opening with a smaller diameter than the diameter of the stone space can be provided at the top of the sauna stove for dispensing water into the stone space. In other words, the stone space widens in this case below the opening at the top of the stone space. The pressure created during the evaporation of the water is thus guided to the valve better.

[0022] Preferably, the first opening of the flow channel is arranged in a lower part of the sauna stove. This allows cool air from the lower part of the sauna room to be drawn in to the flow channel when the valve opens, wherein this air heats up as it travels through the flow channel and the stone space, the heated air exiting the stone space into the room air through the top.

[0023] The valve can be configured to close by the force of gravity or mechanically, preferably by means of a spring force. An automatic closing of the valve can thus be implemented easily. Other types of automatically closing valves according to the prior art are also possible. The valve can include a retarder for slowing down the closing movement. This allows the flow channel to be kept open longer, so that the sauna steam can be made to last longer.

[0024] The flow channel can include a damper for regulating the flow in the flow channel. This makes it possible to regulate the steam output of the sauna stove quickly and easily. The damper can adjust the cross-sectional surface area of the flow channel in order to limit the flow. The damper can be configured so as to be adjustable even during a sauna session when the sauna stove is hot, so that a user can regulate the maximum flow of the flow channel during a sauna session, so that it is possible to generate a more intense sauna steam experience by opening the damper and a milder sauna steam experience by closing the damper .

[0025] The damper can be a manual or electric control device. The damper can thus be configured to be readily adjustable .

[0026] The sauna stove can include a pipe, which pipe has a first opening for an air inlet and a second opening for an air outlet, and said valve is configured to control the flow of a fluid in the pipe, and the flow of fluid in the pipe is configured to be heated by the heat produced in the stone space. The air flowing into the stone space can thus be guided so as to be discharged at a desired location. This also further enhances the sauna steam effect. When the valve is closed, the air in the pipe essentially stands still, so that the air in the pipe heats up to the temperature of the stone space. Thus, when the valve opens, the air from outside the frame of the sauna stove pushes the warm air in the pipe to the desired location, thus providing the user with a pleasant and potent sauna steam effect. It is thus possible to effectively control the warm air discharged from the sauna stove in connection with the throwing of water into the stone space by means of the pipe.

[0027] In one embodiment, the second opening of the pipe can lie outside the stone space and above the stone space in a height direction. The warm air discharged from the pipe can thus be mixed with the water vapour rising from the stone space, so that a potent sauna steam effect is produced that feels pleasant to the user.

[0028] Alternatively, the second opening of the pipe can also lie inside the stone space.

[0029] In a second embodiment, the second opening of the pipe lies outside the stone space and below the centreline of the stone space in a height direction. It is thereby possible to produce warm air in the lower part of the sauna room in connection with the throwing of water into the stone space. It is thereby possible to even out temperature differences in the sauna room, in which the air in the upper part is typically significantly warmer than the air in the lower part during operation.

[0030] In the second embodiment just described, the pipe preferably runs between the first opening and the second opening above the stone space. This produces a natural convection, whereby air is made to flow through the pipe.

[0031] The pipe described in the foregoing can also be used without the valve described in the foregoing. In this case, the pipe can be used to guide the flow of warm fluid flowing out of the sauna stove to a desired location in the sauna room.

[0032] Preferably, a radiation shield is provided between the part of the pipe located outside the stone space and the stone space. It is thereby possible to prevent heat from the sauna stove from radiating into the pipe, so that the flow of air in the pipe is not disturbed. The radiation shield can be a separate component or part of the frame of the sauna stove.

[0033] The pipe can include a damper for regulating the flow in the pipe. Alternatively, the damper can be arranged in an optional pipe, so that the damper achieves the same effect as a damper arranged in the flow channel.

[0034] The damper in the pipe can be a manual or electric control device .

[0035] Preferably, the height of the stone space is at least twice the width of the sauna stove. The steam pressure in a stone space that is high and narrow in shape flows better to the valve.

[0036] In a method according to the invention for momentarily increasing the heat transfer of a sauna stove, the amount of air flowing through a sauna stove is controlled, which sauna stove includes a frame, a stone space that includes a thermal mass, which is heated to a temperature of 200—700 °C and into which water is dispensed in order to form steam, a flow channel with a first opening outside the frame and a second opening inside the frame in the stone space, and a valve configured to limit the flow of a fluid in the flow channel. When water is dispensed into the stone space, the valve opens under the action of the pressure of the water evaporating in the stone space, which allows water vapour to flow in the flow channel from the second opening to the first opening and air from outside the frame to flow from the first opening to the second opening, through the stone space and back outside the frame, and the valve closes automatically when the pressure increase caused by the water dispensed into the stone space ceases. The flow channel of the sauna stove can thus be opened synchronously in connection with the throwing of water into the stone space to produce sauna steam, whereby the intensity of the sauna steam can be increased by controlling the flow of air through the stone space at the moment that water is thrown into the hot stone space.

[0037] Preferably, the valve closes the flow channel and limits the flow of fluid in the flow channel. A perfect closure, however, is not required. For example, the valve can limit the flow of a fluid by at least 90% in the closed position compared to the open position.

[0038] Preferably, air is conveyed into and through the stone space by natural convection in the method. More specifically, air from outside the frame is preferably conveyed from the first opening to the second opening by natural convection. An actuator is thus not needed to convey the air as in a forced convection.

[0039] The invention is described in detail in the following with reference to the attached drawings illustrating embodiments of the invention, wherein

[0040] Figure 1 shows a sauna stove according to the invention in a situation where water is being dispensed into the stone space and the valve is closed,

[0041] Figure 2 shows a sauna stove according to the invention in a situation where the water dispensed into the stone space has evaporated and the valve has opened,

[0042] Figure 3 shows a second sauna stove according to the invention in a situation where the valve is still closed, Figure 4 shows the second sauna stove according to the invention in a situation where the valve is still open,

[0043] Figure 5 shows a third sauna stove according to the invention .

[0044] Figure 1 shows a sauna stove 10 according to the invention, which includes a frame 12, a stone space 14 capable of being heated to a temperature of 200-700°C and of evaporating water dispensed into the stone space 14, and a flow channel 20 with a first opening 21 outside the frame 12 and a second opening 22 inside the frame 12. The stone space 14 here is configured to be heated by resistors 16. The invention does not depend on the way in which the stone space 14 is heated and can consequently be adapted to any sauna stove according to the prior art. The stone space 14 here is partially enclosed in such a manner that the frame 12 of the sauna stove 10 covers more than 50% of the stone space 14. The stone space 14 here contains stones 15 as the heat-storing mass. The cross section of the sauna stove 10 shown in the figures is illustrative and the frame 12 does not have to be continuous around the stone space 14, but rather the frame 12 can include, in addition to the flow channel 20, other openings via which air can flow through the stone space 14. The sauna stove 10 can also be what is known as a caged sauna stove, in which the frame of the sauna stove consists at least partially of a metal mesh.

[0045] The sauna stove 10 includes a valve 30, which valve 30 is configured to limit the flow of a fluid in the flow channel 20, and which valve 30 is configured to open under the action of the pressure of water evaporating in the stone space 14, which allows water vapour to flow in the flow channel 20 from the second opening 22 to the first opening 21 and air from outside the frame 12 to flow from the first opening 21 to the second opening 22, through the stone space 14 and back outside the frame 12, and which valve 30 is configured to close automatically in the absence of a pressure of evaporating water.

[0046] The operation of the sauna stove 10 is based on natural convection here. Air from outside the frame 12 can flow from the first opening 21 to the second opening 22 by natural convection. In other words, the sauna stove 10 does not include a fan for producing a forced convection.

[0047] In the situation shown in Figure 1, water 61 is being dispensed into the stone space 14 with a ladle 60 and the valve 30 is closed .

[0048] In the situation shown in Figure 2, the water 61 dispensed into the stone space 14 has evaporated and turned into water vapour 41, so that its volume has significantly increased, thus raising the pressure in the stone space 14. The resulting pressure has opened the valve 30 in the flow channel 20. The valve 30 here is a hinged metal plate. The generated water vapour 41 thus flows in part in the flow channel 20 from the second opening 22 to the first opening 21. The generated water vapour 41 also flows upwards out of the stone space 14, thus forming steam in the sauna room. However, for the sake of simplicity, this is not designated in the illustrations. The first opening 21 of the flow channel 20 is arranged here in a lower part of the sauna stove 10, i.e. below the centreline of the sauna stove 10 in a height direction, so that cool air 42 can be drawn into the flow channel 20 from the lower part of the sauna room, and so that the distance travelled by the air 42 in the stone space 14 is as long as possible, the air 42 exiting the stone space 14 as heated air through the top. When the valve 30 is open, air 42 from outside the frame 12 of the sauna stove 10 flows from the first opening 21 of the flow channel 20 to the second opening 22 and further into the stone space 14. The air 42 flows further through the stone space 14 back outside the frame 12 and above the stone space 14 while mixing with the water vapour flowing upwards.

[0049] When the pressure increase caused by the water 61 dispensed into the stone space 14 ceases, the valve 30 closes automatically and again limits the flow of the fluids, i.e. the air 42 and the water vapour 41, in the flow channel 20. The valve 30 is configured to close automatically by means of any arrangement according to the prior art, such as by the force of gravity or mechanically, for example by means of a spring force. In the embodiments shown in Figures 1 - 5, the valve 30 is configured to close by the force of gravity. The valve 30 can include a retarder to slow down the closing movement. For the sake of simplicity, a retarder is not shown in the figures. The retarder can be any retarder according to the prior art, such as a hydraulic retarder.

[0050] Figures 3 and 4 show a second embodiment in which the sauna stove 10 includes a pipe 50, wherein the pipe 50 is arranged partly in the flow channel 20 and a valve 30 is configured to control the flow of a fluid in the pipe 50, wherein the pipe 50 has a first opening 51 for an air inlet and a second opening 52 for an air outlet, and the flow of fluid in the pipe 50 is configured to be heated by the heat produced in the stone space 14. In this embodiment, the pipe 50 is arranged coaxially to the flow channel 20. However, in an alternative embodiment, it is possible for the flow channel 20 and the pipe 50 to run, for example, side by side through the frame 12 of the sauna stove 10 and for a same valve 30 to be attached to the sauna stove 10 on the outside of the frame 12 in order to control the flow in both the flow channel 20 and the pipe 50. In other embodiments of the invention, the valve 30 can designate any arrangement that can control the flow in both the flow channel 20 and the pipe 50. The pipe 50 runs here through the stone space 14, although it is also possible to arrange the pipe 50 so as to run, for example, beside the stone space 14.

[0051] In Figure 3, the valve 30 is closed, so that the first opening 51 of the pipe 50 is closed. The heat of the stone space 14 is thus transferred to the air trapped in the pipe 50.

[0052] In Figure 4, water vapour 41 has opened the valve 30, so that air 42 from outside the frame 12 flows into the first opening

[0053] 51 of the pipe 50. This air 42 pushes the warm air in the pipe

[0054] 52 out of the second opening 52 of the pipe 50, and the cool air 42 flowing into the pipe 50 from outside the frame 12 heats up as it travels through the stone space 14. The second opening 52 of the pipe 50 lies here outside the stone space 14 and above the stone space 14 in a height direction, so that the air discharged from the second opening 52 of the pipe 50 mixes with the water vapour or steam flowing upwards out of the stone space 14.

[0055] Figure 5 shows a variant of the embodiment shown in Figures 3 and 4 in which the second opening 52 of the pipe 50 lies outside the stone space 14 and below the centreline of the stone space 14 in a height direction. The pipe 50 runs here from a lower part of the stone space 14 to an upper part of the stone space 14, running through the stone space 14 before it curves downwards outside the stone space 14. The pipe 50 includes a segment between the first opening 51 and the second opening 52 that lies above the stone space 14. In this embodiment, the warm air discharged from the second opening 52 of the pipe 50 is conveyed to the lower part of the sauna room, so that it is possible to even out temperature differences in the height direction of the sauna room. In this embodiment, a radiation shield 56, for example a metal plate, is provided between the part of the pipe 50 located outside the stone space 14 and the stone space 14.

[0056] The flow channel 20 or pipe 50 can include a damper which limits the cross-sectional surface area of the flow channel 20 or pipe 50 and thereby the flow of air 42 in the flow channel 20 or pipe 50. For the sake of simplicity, the damper is not illustrated in the figures. The damper can be any damper according to the prior art, such as a manual or electrical control device, that can adjust the cross-sectional area of the flow channel 20 or pipe 50. In its simplest form, the damper is a metal plate that is configured to be movable in the flow channel 20 or pipe 50. In one embodiment, the user can regulate the cross-sectional surface area of the flow channel 20 or pipe 50 during a sauna session by means of the damper, so that the user can influence the intensity of the sauna steam by regulating the flow of air 42 in the flow channel 20 and / or pipe 50 when the valve 30 is opened. The user can thus control a sauna steam effect to his or her liking without affecting the temperature of the room.

Claims

CLAIMS1. A sauna stove (10) including- a frame ( 12 ) ,- a stone space (14) including a thermal mass capable of being heated to a temperature of 200-700° C and of evaporating water dispensed into the stone space (14) ,- a flow channel (20) with a first opening (21) outside the frame (12) and a second opening (22) inside the frame (12) in the stone space (14) , and- a valve (30) configured to limit the flow of a fluid in the flow channel (20) , characterized in that said valve (30) is configured to open under the action of the pressure of the water evaporating in the stone space (14) , which allows water vapour to flow in the flow channel (20) from the second opening (22) to the first opening (21) and air from outside the frame (12) to flow from the first opening (21) to the second opening (22) , through the stone space (14) and back outside the frame (12) , and said valve (30) is configured to close automatically in the absence of a pressure of evaporating water.

2. The sauna stove (10) according to claim 1, characterized in that air from outside the frame (12) can flow from the first opening (21) to the second opening (22) by natural convection.

3. The sauna stove (10) according to claim 1 or 2, characterized in that the stone space (14) is configured to be heated by means of resistors (16) or by burning wood or gas or a combustible liquid, such as oil, or by the friction generated by an electrically driven turbine.

4. The sauna stove (10) according to any one of claims 1- 3, characterized in that the stone space (14) is partially enclosed in such a manner that the frame (12) of the sauna stove (10) covers at least 50%, preferably at least 80%, of the stone space (14) .

5. The sauna stove (10) according to any one of claims 1- 4, characterized in that said first opening (21) of the flow channel (20) is arranged in a lower part of the sauna stove (10) .

6. The sauna stove (10) according to any one of claims 1- 5, characterized in that said valve (30) is configured to close by the force of gravity or mechanically, preferably by means of a spring force.

7. The sauna stove (10) according to any one of claims 1- 6, characterized in that said valve (30) includes a retarder for slowing down the closing movement.

8. The sauna stove (10) according to any one of claims 1- 7, characterized in that said flow channel (20) includes a damper for regulating the flow in the flow channel (20) .

9. The sauna stove (10) according to claim 8, characterized in that said damper is a manual or electric control device.

10. The sauna stove (10) according to any one of claims 1- 9, characterized in that the sauna stove (10) includes a pipe (50) , which pipe (50) has a first opening (51) for an air inlet and a second opening (52) for an air outlet, and said valve (30) is configured to control the flow of a fluid in the pipe(50) , and the flow of fluid in the pipe (50) is configured to be heated by the heat produced in the stone space (14) .

11. The sauna stove (10) according to claim 10, characterized in that the second opening (52) of said pipe (50) lies outside the stone space (14) and above the stone space (14) in a height direction.

12. The sauna stove (10) according to claim 10, characterized in that the second opening (52) of said pipe (50) lies outside the stone space (14) and below the centreline of the stone space (14) in a height direction.

13. The sauna stove (10) according to any one of claims 10 - 12, characterized in that a radiation shield (56) is provided between the part of said pipe (50) located outside the stone space (14) and the stone space (14) .

14. The sauna stove (10) according to any one of claims 10 - 13, characterized in that said pipe (50) includes a damper for regulating the flow in the pipe (50) .

15. A method for momentarily increasing the heat transfer of a sauna stove (10) , in which method the amount of air flowing through a sauna stove (10) is controlled, which sauna stove (10) includes- a frame ( 12 ) ,- a stone space (14) that includes a thermal mass, which is heated to a temperature of 200-700 °C and into which water is dispensed in order to form steam,- a flow channel (20) with a first opening (21) outside the frame (12) and a second opening (22) inside the frame (12) in the stone space (14) , and- a valve (30) configured to limit the flow of a fluid in the flow channel (20) , characterized in that, when water (61) is dispensed into the stone space (14) , said valve (30) opens under the action of the pressure of the water evaporating in the stone space (14) , which allows water vapour to flow in the flow channel (20) from the second opening (22) to the first opening (21) and air from outside the frame (12) to flow from the first opening (21) to the second opening (22) , through the stone space (14) and back outside the frame (12) , and said valve (30) closes automatically when the pressure increase caused by the water (61) dispensed into the stone space (14) ceases.

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