Abstract:
The invention relates to a flow monitor for monitoring the flow of flowing media, wherein a paddle projecting into the flow transfers the rotating movement of the paddle onto a display device by means of a magnetic gear comprising a plurality of individual magnets corresponding with each other.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the US national phase of PCT application PCT/EP2009/000649, filed 31 Jan. 2009, published 24 Sep. 2009 as 2009/115162, and claiming the priority of German patent application 102008015158.0 itself filed 20 Mar. 2008, whose entire disclosures are herewith incorporated by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a flowmeter for monitoring fluids in pipes, in particular for monitoring the flow and thus the pump function of cooling systems on electric transformers. 
     BACKGROUND OF THE INVENTION 
     Such flowmeters are known in numerous embodiments. DE 3,317,923 describes such a flowmeter, termed a flow switch, that has a paddle projecting into the fluid flow to be monitored. A pivotal rod carrying the paddle has a free end carrying a permanent magnet that cooperates with a Reed switch. Thus, like numerous other similar flowmeters, this paddle forms in the flow a flow resistance. If the flow level is sufficient, it pivots the paddle in the flow direction, as a rule against the force of a spring. In most cases, this movement is converted into rotation in order to activate a mechanical display or electrical switch. 
     Another flowmeter having a similar construction is known from the publication Qualitrol Technical Data Sheet: Oil Flowmeter Series 092″ [Technisches Datenblatt Qualitrol: Ölströmungsmelder Serie 092], publication date: March 1992. Here as well, a mechanical actuating force is exerted on a flag (i.e. paddle) placed in the flow. 
     However, all currently known flowmeters of the type described above have certain disadvantages: 
     On the one hand, they tend to jam in their final positions for different reasons. This is often due to the fact that the mount is inadequate, the rotatable shaft is twisted, or the actuating force is not sufficient by virtue of the construction of the flowmeter. Moreover, the known flowmeters are sensitive to the turbulence often produced by pumps, such that the display wobbles or the necessary force for moving the display is not sufficient. Occasionally, nonactivation may also be found due to cavitation and turbulent, nonlaminar flow. 
     OBJECT OF THE INVENTION 
     The object of the invention is therefore to provide a flowmeter of the type described above that has a simple structure and is easy to install, but still has a high degree of functional reliability and low mechanical resistance while still providing a high degree of actuating force for the display. 
     SUMMARY OF THE INVENTION 
     This object is attained according to the invention by a flowmeter in which the paddle is connected to a rotatable first shaft whose rotation may be transferred in a contact-free fashion to a second shaft carrying a pointer. The first shaft and the second shaft are perpendicular to one another and a magnetic gear is provided between the first and second shafts with an actuator part on the first shaft and a drive part on the second shaft. 
     The flowmeter according to the invention has a simple structure and comprises only a few components; it is robust and allows for simple installation and adjustment. A “magnetic gear” is used in the invention. High levels of actuation force are generated without mechanical friction on a separate shaft by the motion deflection of the rotation of the paddle. 
     According to a particularly advantageous embodiment of the invention, the paddle has an involute shape. In this manner, a constant actuating force may be attained over the entire rotational angle. 
     According to another advantageous embodiment, the paddle is constructed as a cup-shaped upstream-open flow body, similar to a spoon, which at the same time minimizes the influence of any turbulent flow in the pipe because increased dynamic pressure is able to build up upstream of the paddle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention is described in greater detail below by way of example with reference to the drawings in which: 
         FIG. 1  is schematic cross-section through a flowmeter according to the invention; 
         FIG. 2  is a schematic depiction of a flowmeter without its mounting plate; 
         FIG. 3  is a perspective view of a mounting plate by itself from the rear; 
         FIG. 4  is a perspective view of a flowmeter according to the invention from the front, the display side; 
         FIG. 5  shows a first embodiment of a paddle; 
         FIG. 6  shows a further embodiment of a paddle with a cup-shaped flow body; and 
         FIG. 7  is a schematic partial view of another flowmeter according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     First, the construction shown in  FIG. 1  shall be described. 
     A flowmeter according to the invention intended to monitor the flow in a pipe A is bolted to a flange B of this pipe A provided especially for this purpose. 
     The flowmeter itself comprises a housing  1  and a mounting plate  2  bolted to it. To this end, a flange  3  to which the mounting plate  2  mentioned above is bolted is provided on the housing  1 . A paddle  4  is pivotally mounted on the plate  2 . To this end, the paddle  4  is formed with a bar  5  to which a bracket  6  is attached. This bracket  6  and therefore the paddle  4  are fixed to a rotatable shaft  7 . The shaft  7  is supported on the mounting plate  2  by bearings  8  and  9 . A sector plate  10  having an is circularly arcuate outer edge is attached in turn to the rotatable shaft  7 . Magnets, specifically N magnets  11  alternating with S magnets  12  polarized radially to the mounting plate  2  and thus to the flange  3 , are fitted to the edge of the sector plate  10 . 
     As discussed above, the mounting plate  2  is bolted to the housing  1 . To this end, the housing  1  has the complementary flange  3  described above with a flat imperforate rim  13 . The bolts  14  used for securing the mounting plate  2  are also shown. An additional rotatable shaft  15 , which is rotatable in the housing  1  on bearings  16  and  17 , extends through the housing  1  perpendicular to the plane of the bolted mounting plate  2 . On its side facing away from the mounting flange  2  in its installed state, the shaft  15  carries a magnetic disk  18  on which magnets are also located, specifically N magnets  19  and S magnets  20 . These magnets alternate in the same pattern as the magnets  11  and  12  described above on the edge of the sector plate  10 . They are complementarily arrayed and thus form a magnetic gear operating in a contact-free manner, also described as a “magnetic gear.” In addition, electrical circuitry  21  and/or means for operating electrical switches is provided on the rotatable shaft  15 . On the free end of the rotatable shaft  15 , a pointer  22  is attached that moves along a display scale  23 . 
     In the case of flow in the pipe A, the paddle  4  is deflected against the force of a torque spring  24  acting on the shaft  7 , thus rotating the shaft  7  and the sector plate  10  carried by it with the magnets  11  and  12  mounted on its edge. By transferring the magnetic forces onto the magnetic disk  18 , or more accurately the magnets  19  and  20 , which occurs in a contact-free fashion, the shaft  15  is rotated in the housing  1 . As a result, the electrical circuit  21  is activated and the pointer  22 , which moves over the scale  23 , is moved. 
     In addition, a stop  27  is shown that limits the maximum deflection of the paddle  4 . 
       FIG. 3  shows the mounting plate  2  alone in a different scale, specifically viewed from the side that is bolted onto the flange  3  of the housing  1 . 
       FIG. 4  shows the complete flowmeter from the front side, on which the pointer  22  and scale  23  are located. 
       FIG. 5  shows a paddle  5  alone. Here, a possible shape  25  of the paddle may be seen by means of which a constant flow force is achieved to the greatest degree possible. In addition, an incoming flow ridge  26  may also be seen that induces a high coefficient of resistance that at least reduces the disruptive influence of turbulent flow in the pipe A. 
       FIG. 6  shows an additional advantageous embodiment of a paddle as a cup-shaped flow body  28 . Such an embodiment attains a particularly high level of flow force over the entire rotational angle. 
       FIG. 7  is a schematic perspective section through a flowmeter within the framework of the invention. Here, the cup-shaped flow body  28  discussed in the preceding paragraph is concave upstream and is mounted on the oil flowmeter, i.e. attached by means of its flange B to the pipe to be monitored. The flow body is deflected when oil flows in this pipe. The upstream-open flow body  28  is attached to the rotatable shaft  7  that in turn carries the sector plate  10  discussed above on which alternating N magnets  11  and S magnets  12  are mounted. The magnetic disk  18  mounted on the shaft  15  may also be seen here. The magnets alternating on the magnetic disk  18  in the same array are shown in a partial sectional view. The shaft  7  carrying the sector plate  10 , and the shaft  15  carrying the magnetic disk  18  are perpendicular to each other. In this manner, the cooperating magnets correspond with one another in the manner of a “magnetic gear” so that, if flow is present, the approach flow body  28  is deflected and turns the sector plate  10 . This rotation is transferred in a contact-free manner to the shaft  15  and thus to the pointer  22  that moves across the scale located below it, by means of the “magnetic gear” described above via the magnetic disk  18 . 
     According to the invention, deflection of the paddle  4  or the flow body  28  acting in the same manner is first converted into rotation of the shaft  7  and thus of the sector plate  10 . Only rotation of this shaft leads to rotation of the additional shaft  15  perpendicular thereto. In conjunction with the effect of the “magnetic gear” operating in a contact-free fashion, a gear arrangement results that allows high actuating forces and that is not associated with the danger of jamming at the end position. 
     The prior art discloses only the arrangement of a simple magnet hub by means of which a 1:1 transmission of the rotational movement occurs from a paddle to a display pointer; in contrast, the invention allows a contact-free actual gearing with the option of changing the transmission ratio of this rotational movement as a function of the dimensions of the sector plate  10  and the magnetic disk  18  within broad limits. 
     The flowmeter according to the invention is particularly suitable for monitoring pump function in transformer cooling systems. It may be used in a particularly advantageous fashion in transformers with forced oil circulation, for example, OFAF (oil-forced/air-forced) and ODAF (oil-direct/air-forced) transformers.