The present invention concerns a damper for linear adjustment of a fluid flow such as an air flow, a liquid flow or the like.

A damper for linear adjustment of a fluid flow is essentially designed in such a manner that the fluid through-flow is linear and approximately directly proportional to the damper's degree of opening. The object of such a damper with linear adjustment characteristics is, amongst other things, to facilitate the use of standard adjustment strategy and adjustment technology in order to adjust the fluid through-flow in a fluid pipe.

On account of its construction a standard damper or valve which is used to adjust the through-flow in a fluid pipe will have an opening and closing characteristic in the form of the amount of medium which has flowed through as a function of the damper's or the valve's degree of opening. In by far most of the cases where only a simple adjustment is required, an approximate adjustment can be undertaken with limited knowledge of the valve's or the damper's characteristic, thereby achieving the desired result in the form of through-flow volume. If, however, a more accurate adjustment of the through-flow volume is required, it is necessary to have additional detailed knowledge of the damper's or the valve's characteristic both for opening and closing, while at the same time a great number of flow-related factors concerning the valve or the damper also have to be considered. The transition between laminar and turbulent flow, different resistance as a result of increased flow rate, pressure resistance, etc. are factors which will affect the total flow picture and which in turn will be controlled by, amongst other things, the damper's or the valve's opening/closing characteristics.

If the damper or the valve is designed in such a manner that a linear characteristic is obtained in the relationship between fluid volume passed and degree of opening, it will be easier to use the damper in a standard adjustment system where traditional elements with regard to sensors, adjustment and programming can be employed. This in turn contributes to substantially lower costs when employing a linear damper/valve in an adjusted system, while at the same time the possibility will exist for obtaining a more accurate adjustment of the fluid flow. In connection with, e. g., adjustment of ventilation systems where it is essentially difficult to

adjust variable air volume, a damper or a valve with linear characteristics will be able to provide lower costs for installation of the adjustment system by means of standardised adjustment elements, lower costs in connection with start-up and subsequent operation of the adjustment system, more reliable control with regard to variable air volume together with more reliable control with regard to pressure changes, resulting in a lower energy consumption by means of a further optimal control of the ventilation system.

In particular, it will be possible to achieve an automatic adjustment in a substantially simpler manner if dampers or valves in an adjustment system have a linear or approximately linear characteristic.

Thus it is the object of the present invention to provide a damper for installing in a channel with a fluid flow, which damper has a linear adjustment relationship between percentage opening and volume flowed through. The damper should be designed so as to provide good flow-related conditions, low pressure resistance, and possibly a low noise level and simple design for altering the damper's characteristics. The damper consists essentially of a profile plate and one or more adjustment plates, which profile plate and adjustment plate are movable relative to each other and which plates are provided with one or more apertures. The plates are preferably mounted close to each other in order to avoid eddying and flow disturbances.

The apertures in the profile plate have a design which is adapted to operative conditions and which provide linear conditions between the aperture and through-flow volume. According to the invention the apertures in the profile plate are designed on the basis of a triangle with a bottom line and two vertical sides. The bottom line remains unchanged and represents the full opening in the damper and the vertical sides and the top are adapted so as to permit the damper to provide an optimally adapted linear adjustment characteristic. The adaptation in this design has to satisfy in particular the requirements for a linear relationship in the lower part of the characteristic, i. e. where there is little through-flow and a small opening.

It is a further object of the present invention to place the profile plate and the adjustment plate relative to each other in a flow pipe in order to obtain flexibility with regard to subsequent changes in the fluid system's shape, etc.

If the system where the damper is employed is reconfigured with respect to pressure, volumetric rate, through-flow volume, etc., it is an object of the damper according to the present invention that it should be capable of being

easily adapted to the new conditions. This may be implemented, for example, by replacing one or both of the plates or altering their position in the fluid pipe. According to an embodiment of the present invention the profile plate is provided with one or more apertures and the adjustment plate is provided with one or more apertures adapted in size in shape, with the result that the adjustment plate's aperture forms an area corresponding to or larger than the total area of the aperture in the profile plate. In a further embodiment the size and shape of the aperture in the adjustment plate may be adapted so that the aperture in the adjustment plate co-operates with the aperture in the profile plate, thus together providing the best possible linear adjustment of the fluid flow. Out of consideration for the flow-related conditions the profile plate and the adjustment plate are placed substantially across the channel and may be at an angle relative to the vertical plane in the channel's longitudinal direction. By altering the angle the damper can be adapted to the various operating conditions and achieve the desire pressure resistance and flow- related environment. The two plates may further be installed at an angle of up to 90° relative to the vertical plane, i. e. in an approximately horizontal relationship to the channel's longitudinal direction where the plates can be moved relative to each other in the channel's longitudinal direction. Thus it will be possible to place a transition to the channel's walls at each end of the plates. These transition pieces can be adapted to the flow conditions in the channel by means of, e. g., their angle relative to the horizontal plane.

Nevertheless it is an important feature that the plates can be moved relative to each other substantially in the channel's longitudinal direction.

Two different approaches have been employed in previous attempts to solve the problem and the task. Attempts have been made to evolve various methods for controlling volumetric flow rate by means of a programmed adaptation of control signal relative to the characteristic properties of a valve or a damper when opening and closing. In Norwegian laid open patent application no. 166462 a solution is described in which volumetric flow through an air conditioning channel is controlled by a control means which, for example, may be a control damper. A method is described for controlling the damper or a body equivalent to a damper which is based on the real effective characteristic curve for the control means and the desired effective characteristic curve. The opening and the closing of the control damper are then controlled by means of a non-linearised control signal function. The

solution which is described in the said laid open patent application can be employed in connection with by far most of the standard valves and dampers as long as the characteristic curve for the damper or the valve is known.

Furthermore, the characteristics must be known for different pressure situations, flow rates, etc. if it is to be possible to non-linearise the control signal for the conceivable situations which may arise, for example in a ventilation system. The solution still does not solve the problems mentioned above regarding adaptation to existing adjustment technology and evades the problem by employing programmed functions which may act together with sensor technology which contributes to correction of the control. It will not be possible, however, to deviate from the programmed conditions and thus when the system is altered either a reprogramming will have to be undertaken or a local adaptation which in most cases will entail substantial expenses in connection with adaptation of altered operating conditions to characteristic data for existing dampers and valves. In short, it can be established that the use of existing valves and dampers with an adaptation of control signal according to real characteristics for opening and closing of dampers and valves is not a very flexible method for producing linear adjustment of a fluid flow. This is particularly attributable to lack of adaptability to standard adjustment technology, together with lack of flexibility in connection with subsequent alteration of existing systems.

A second approach to the problem of linear adjustment of a fluid flow has been attempted by adapting the actual adjustment body in the air flow, such as a valve or a damper. In this case it has been shown that it is possible to achieve a greater degree of linear adjustment of a fluid flow by an adaptation of the flow aperture in, for example, a damper. This may, e. g., be an adaptation of the shape of the element which closes off the fluid flow aperture in the damper.

A technical solution in the above-mentioned category is described in, amongst others, US patent 5,218,998 and US patent 5,427,146, which both describe a damper consisting of a plate equipped with apertures, and an additional plate placed in a movable relationship with the first plate, where the second plate is also equipped with apertures. In an end position the apertures are displaced relative to one another, thereby preventing complete through-flow of the flow medium. Moreover, the plates can be moved relative to each other, with the result that in a second end position the

apertures in the two said plates are located above one another, thereby providing a flow aperture corresponding to the open section between the apertures in the two plates. In US patent 5,427,146 the apertures in the two plates have the same hexagonal shape and the total through-flow aperture in the damper will be hexagonally shaped and is formed in the intersecting area between the apertures in the two plates. The said publication deals with solutions where the apertures in the two plates have the same shape and size and a number of apertures are provided in the plates. Moreover, in US 5,218,998 there is described a solution related to that which is presented in US 5,427,146. In this case, however, the apertures in the two plates are trapezoidal and placed in an oppositely directed relationship. Furthermore, the apertures have the same shape and size. In figure 8 of the publication a solution is shown where two plates are employed with only one aperture in each plate. The plates, however, are indicated placed in channels where the plates are curved or divided into different angular plate segments. The solution consisting of an aperture in each plate is indicated placed across a channel. This provides a high degree of pressure resistance and unfavourable flow-related conditions which in turn affect the linearity in the damper's adjustment characteristics.

A further related solution is described in US patent 3,223,019 where two mutually movable plates are employed. The fluid flow, however, is directed outwards from a channel and thus it does not matter how the damper is placed relative to the channel. Furthermore, the apertures in the plates are not necessarily similar in shape. The solution has little in common with the present invention since no account is taken of the flow-related conditions inside a channel on each side of the damper while at the same time it seems as if the linearity in the adjustment is only slight and a minor consideration.

On the basis of what has been described as prior art the present invention is concerned with a solution according to the introduction to the independent claim and with special characteristics as indicated in the characterising part of the independent claim. Furthermore, the damper according to the present invention can exist in alternative embodiments as indicated in the dependent claims.

The invention will now be described in relation to the accompanying figures in which:

figure 1 is a section viewed from the side of an embodiment of the present invention where the profile plate and the adjustment plate are placed horizontally in the channel's longitudinal direction and are provided with an aperture.

Figure 2 is a section viewed from above of the embodiment in figure 1.

Figure 3 is a section viewed from the side of an embodiment of the present invention where the profile plate and the adjustment plate are placed horizontally in the channel's longitudinal direction and are provided with a plurality of apertures in longitudinal direction and breadth.

Figure 4 is a section viewed from above of the embodiment in figure 3.

Figure 5 is a section viewed from the side of an embodiment of the present invention where the profile plate and the adjustment plate are placed horizontally in the channel's longitudinal direction and are provided with a plurality of apertures in the longitudinal direction.

Figure 6 is a section viewed from above of the embodiment in figure 5.

Figure 7 is a section viewed from the side of an embodiment of the present invention where the profile plate and the adjustment plate are placed in the channel's longitudinal direction at an angle of less than 90° relative to the vertical plane.

Figure 8 is a section viewed from above of the embodiment in figure 7.

Figure 9 is a translucent isometric view of the embodiment according to figures 7 and 8.

Figure 10 illustrates a design of the aperture (s) in the profile plate which is adapted to linear adjustment characteristics.

Figure 11 illustrates a further design of the aperture (s) in the profile plate which is adapted to linear adjustment characteristics.

In figures 1 and 2 there is illustrated an embodiment of the present invention where the profile plate 4 and the adjustment plate 3 are placed in a mutually movable relationship horizontally in the channel profile's 1 longitudinal direction. At each end of the profile plate 4 the profile plate 4 is connected to the channel's 1 internal surface via a front supporting wall 6 and a rear

supporting wall 7. According to the present invention the adjustment plate 3 is movable in the channel's 1 longitudinal direction relative to the profile plate 4. In figure 1 the profile plate 4 is provided with one triangular aperture with its front apex pointing in the direction of flow 9 for the fluid in the channel 1. In the present embodiment the adjustment plate 3 is provided with an aperture corresponding to the aperture in the profile plate 4. According to the present invention the area of the aperture in the adjustment plate 3 is the same size as or larger than the area of the aperture in the profile plate 4. In one of its extreme positions the adjustment plate 3 is fully retracted, completely blocking the aperture in the profile plate 4. The adjustment plate 3 can then be moved relative to the profile plate 4 with the result that the apertures in the two plates 3,4 form a triangular through-going aperture in the damper. The fluid in the channel 1 then passes under the front supporting wall 6 and up through the aperture which is formed in the horizontally mounted plates 3,4 in the longitudinal direction of the channel 1. The adjustment plate 3 is moved in the channel's 1 longitudinal direction along the rails 5 of a drive device 10 via a transmission 11. The transmission 11 is rotatably mounted on an attachment point 12 on the adjustment plate 3. In figure 1 the drive device 10 is shown mounted on the outside of the channel 1 but can be installed in several different positions, externally or internally in the channel profile 1. Various types of drive devices may also be employed here, such as rotating drive devices and linear drive devices. These may be electrically driven such as a DC motor, a stepper motor or the like, or the drive device 10 may be, for example, hydraulically or pneumatically driven.

For example, a pneumatic or hydraulic linear drive device may be employed on the inside or the outside of the channel for moving the adjustment plate 3.

The embodiment in figure 1 provides an approximately linear adjustment of passing fluid volume relative to the movement of the adjustment plate 1. In the present invention the linearity is substantially determined by the shape of the aperture in the profile plate 4 which in the present invention is based on a triangle but which can be further adapted in order to achieve an approximately linear opening/closing characteristic.

In figures 3 and 4 there is further illustrated an embodiment as a section from the side and a section from above respectively similar to that illustrated in figures 1 and 2. In figure 3 it is shown how, in the same way as in figure 1, the profile plate 4 and the adjustment plate 3 are mounted horizontally in the

channel's 1 longitudinal direction. The two plates 3,4 are movably positioned relative to each other, and at each end in the longitudinal direction the profile plate 4 is connected with the channel's 1 internal surface by a front supporting wall 6 and a rear supporting wall 7. In the present embodiment the walls 6,7 like corresponding walls 6,7 in figure 1, are mounted vertically relative to the channel 1. Taking into account both flow- related conditions and the lowest possible pressure resistance it will be possible to place the walls 6,7 at an angle relative to the vertical plane. In figure 4 the profile plate is illustrated with several triangular apertures. In the breadth of the profile plate 4 there are mounted two triangular apertures placed beside each other. According to the present invention there is further mounted in the longitudinal direction of the plate (and the channel 1) similar "pairs"of triangular apertures and the adjustment plate 3 is provided with three apertures whose area is larger than the apertures in the profile plate 4.

The apertures in the adjustment plate 3 are rectangular with a larger area in the breadth of the plate. In the same way as the embodiment in figures 1 and 2, in one of its end positions the adjustment plate 3 will completely cover the apertures in the profile plate 4 and there is no through-flow through the damper. By means of a drive device 10 and transmission 11 to a point 12 on the adjustment plate 3 the plate 3 can be moved in the longitudinal direction of the channel 1 and thereby in the longitudinal direction of the profile plate 4 along rails 5. When the adjustment plate 3 moves in its longitudinal direction the apertures 8 in the adjustment plate 3 will uncover the apertures in the profile plate 4, thus permitting a through-flow in the damper in the direction of flow 9 as indicated in the figure. It should be noted in figure 4 that the profile plate 4 is provided with four"pairs"of triangular apertures while the adjustment plate 3 is provided with three rectangular apertures. In its front end position the adjustment plate 3 covers the four"pairs"of triangular apertures and during subsequent movement the front edge of the adjustment plate 3 will uncover the front"pair"of triangular apertures in the profile plate 4. As in figure 2 the fluid flows in under the front supporting wall 6 and up through the apertures which are formed in the section between the apertures in the two plates 3 and 4. In the embodiment the flow volume through the damper will be approximately linear with the movement of the adjustment plate 3. Here too the linearity is substantially determined by the shape of the apertures in the profile plate 4.

In figures 5 and 6, as in figures 1 to 4, it is shown how the profile plate 4 and the adjustment plate 3 are mounted horizontally in the channel's 1 longitudinal direction. The two plates 3,4 are movably mounted relative to each other and at each end in the longitudinal direction the profile plate 4 is connected with the channel's 1 internal surface by a front supporting wall 6 and a rear supporting wall 7. In the present embodiment, in the same way as corresponding walls 6,7 in figures 1 and 3, the walls 6,7 are installed vertically relative to the channel 1. In figure 6 the profile plate 4 is illustrated with a plurality of triangular apertures placed after one another in the longitudinal direction of the plate 4 and the channel 1. According to the present invention the adjustment plate 3 is provided in the longitudinal direction with three apertures whose area is larger than the apertures in the profile plate 4. The apertures in the adjustment plate 3 are rectangular with a larger area in the breadth of the plate. In the same way as the embodiment in figures 1 to 4, in its end position the adjustment plate 3 will completely cover the apertures in the profile plate 4 and there is no through-flow through the damper. By means of a drive device 10 and transmission 11 to a point 12 on the adjustment plate 3, the plate 3 can be moved in the longitudinal direction of the channel and thereby the profile plate 4 along rails 5. When the adjustment plate 3 moves in the longitudinal direction the apertures 8 in the adjustment plate 3 will uncover the apertures in the profile plate 4, thus permitting a through-flow in the damper in the direction of flow 9 as indicated in the figure. It should be noted in figure 6 that the profile plate 4 is provided with four triangular apertures while the adjustment plate 3 is provided with three rectangular apertures. In its front end position the adjustment plate 3 covers the four triangular apertures and during subsequent movement the front edge of the adjustment plate 3 will uncover the front triangular aperture in the profile plate 4. As in figures 2 and 4 the fluid flows in under the front supporting wall 6 and up through the apertures which are formed in the section between the apertures in the two plates 3 and 4. In the embodiment the flow volume through the damper will be approximately linear with the movement of the adjustment plate 3. Here too the linearity is substantially determined by the shape of the apertures in the profile plate 4.

In figure 7 and 8 there is illustrated a further embodiment, as a section viewed from the side and a view from above respectively, which in many cases will be better adapted to flow-related conditions and which provides

lower pressure resistance. In figure 7 the profile plate 4 and the adjustment plate 3 are illustrated disposed at an angle a less than 90° relative to the vertical plane. The plates 3 and 4 are still mounted substantially in the channel's 1 longitudinal direction and according to the invention the triangular apertures in the profile plate 4 are disposed with a corner in the direction of flow. The adjustment plate 3 moves along the profile plate 4 in the channel's 1 longitudinal direction. In the same way as the embodiments illustrated in the preceding figures the adjustment plate 3 is driven by a drive device 10 via transmission 11 to a point 12 on the adjustment plate 3. In the present embodiment three triangular apertures are provided in the breadth of the profile plate 4 and in figure 8 there is illustrated an adjustment plate 3 in which the apertures have the same shape and size as the apertures in the profile plate 4.

Furthermore, in figure 9 there is an isometric illustration of an embodiment in accordance with figures 7 and 8. The plates 3 and 4 are mounted in the channel's longitudinal direction at an angle a relative to the vertical plane.

According to the invention the angle a may be up to 90 degrees where the plates 3 and 4 are horizontal. In the embodiment illustrated in figures 7 to 9 moreover, it is immaterial in which direction the adjustment plate 3 is moved in its longitudinal direction.

In the embodiments which are illustrated in the preceding figures 1 to 9 triangular apertures are employed in the profile plate 4 in order to obtain linear adjustment of fluid through-flow relative to the damper's opening.

There are, however, a number of factors which have to be considered in order to obtain good linearity in all parts of the adjustment area. Some of the special problems which may be mentioned here are satisfactory filling at the beginning of the opening and further linear follow-up right up to the end. In order to achieve the best possible linear conditions it has been shown that a triangular aperture with lateral edges 21 which curve concavely inwards in the aperture may be advantageous. This provides an approximately triangular shape with curved lateral edges 21, which is partly illustrated in the above- mentioned publication US 5,218,998, figure 6. In order to achieve satisfactory filling, i. e. ample through-flow of fluid in the first phase of the adjustment, however, it has been shown to be advantageous if the upper corner 20 of the triangle, where the concave surfaces 21 meet, is rounded.

This is illustrated in figure 10 which gives an example of a preferred

embodiment of an aperture in a profile plate 4. The upper curve 20 provides sufficient through-flow in the early phase of the linear adjustment, while the concave lateral surfaces 21 give a linear central part. The end of the adjustment is effected by the transition between the sides 21 and the bottom 22. The corners 23 can also be rounded here but for the sake of linearity the bottom line 22 ought to constitute the greatest breadth in the triangle since this is the maximum opening corresponding to maximum movement of the damper's adjustment plate 3.

In figure 11 a further embodiment is illustrated of the aperture in a profile plate 4. As mentioned above account has been taken of the fact that at an early point in the adjustment sufficient fluid must be admitted in order to achieve a linear lower part of the curve which shows through-flow as a function of opening. This is achieved by the fact that the front part of the opening profile 31, which is not opened until the profile plate 4 and the adjustment plate 3 are moved relative to each other, has a rounded shape which may be flattened in relation to a rounding of a corner in a triangle while at the same time the latter may be more pointed than a semi-circular arc with a large diameter. Moreover, between the front part 31 of the aperture and the rear part 33 there are convexly outwardly curved lateral edges 32 which are terminated at the rear edge 33 of the aperture.

In the above-described embodiments solutions are described according to the present invention where the profile plate 4 and the adjustment plate 3 are movable relative to each other. This does not necessarily mean that one of the plates 3,4 is fixed in the channel profile 1 and the other movably mounted, but can also mean that both plates 3,4 move relative to each other by means of simultaneous movement of both plates 3,4. If one of the plates 3,4 is fixed this may be both the profile plate 4 and the adjustment plate 3.

Moreover, in the event of altered operating conditions it will be possible to replace one or both plates 3,4 in order to change the characteristic of the linearity. This can easily be implemented according to the present invention if the aperture in, e. g. the adjustment plate 3 is of such a size and shape that it can be employed with a plurality of profile plates 4. By replacing the profile plate 4 it will thereby be possible to adapt the damper to altered operating conditions.

Furthermore, it will be possible to employ adjustment plates 3 which are divided and which are moved relative to the profile plate 4 in successive order or another suitable manner. This will enable a segmented linear adjustment to be achieved. If the linearity is good the successive adjustment will provide a greater range of adjustment with finer resolution.

In a preferred embodiment the positioning of the profile plate 4 and the adjustment plate 3 as indicated in figures 7,8 and 9 is combined with apertures in the profile plate 4 as illustrated in either figure 10 or 11. This can be selected on the basis of the existing operative conditions.