Abstract:
A hydrocyclone has a separating part A with a diameter which toward its outlet end for the heavier fraction decreases gradually from a diameter 2 R a , with the radius being subject to the formula: 
     
       R=R.sub.a ·√1-x/1. 
     
     This describes essentially the shape of a parabola, so that the separating part can practically be considered as a paraboloid. Achieved thereby is an optimum separating performance of the hydrocyclone.

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns a hydrocyclone with a reversing flow, for separation of foreign particles from suspensions with a specific mass greater than the mass of the fluid of the suspension. The hydrocyclone has a cylindrical entrance part of large diameter, in which area there is located, centrally, an outlet pipe for the lighter accepts fraction; and has a part having a gradually decreasing diameter which has at its narrowest cross section an outlet for the heavy fraction. Various hydrocyclones are known in the prior art. 
     The problem underlying the invention is to further improve the separating effect of such a cyclone. 
     SUMMARY OF THE INVENTION 
     This problem is inventionally solved by the features of the hydrocyclone of the present invention. The inside diameter of the part (A) having a gradually decreasing diameter is subject to the formula: 
     
         R=R.sub.a ·√1-x/1 
    
     where R represents the inside radius of part A, R a  is the beginning radius of part A adjacent to the cylindrical part, and x is the coordinate beginning at the beginning radius and extending along the central longitudinal axis of the hydrocyclone, where a variation which gradually increases or decreases toward the x-axis, upward or downward is possible, for instance through a sectional, conic design of the wall. l is the theoretical overall length of the parabola obtained with the formula to the intersection with the x-axis, where additionally the condition 1=(10 to 24)R a  exists. The cyclone is truncated at its outlet end for the heavier fraction at a length l k  with a radius R d , in order to form an outlet opening, or nozzle. 
     It has been found that, with a design of the cyclone part where the diameter decreases gradually toward the exit end for the heavy substances, a good separating effect is achieved when fashioning the outside wall of this part according to the said formula. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1, shows basically a cross section of the cyclone; 
     FIG. 2, shows an enlarged section of the discharge end; and 
     FIG. 3, shows another embodiment of the inlet area of the cyclone. 
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The cyclone according to FIG. 1 comprises parts A, B and C. In the entrance area B, it is provided with a tangential inlet 7 and a central withdrawal, or outlet, pipe 5 for the lightweight accepts substances. Contained inbetween is a cylindrical part C with a radius R a . With that same radius also begins the part A featuring the gradually decreasing diameter, with the start of the x-axis being situated here which extends along the central longitudinal axis of the cyclone. The radius R of this partial section is then subject to the formula R=R a  ·√1-X/l. 
     The separating part A ends in the nozzle body 4 by means of nozzle 3 serving as an outlet for a heavy fraction. This nozzle 3 is created by truncating the theoretical overall length l of the cyclone to a length l k . The required nozzle diameter, thus, is obtained by various nozzle parts 4 that can be attached to the body of the hydrocyclone. 
     Preferably above the nozzle part 4, i.e., X&lt;0.95·l k , an approach of the contour of the cyclone to the stated formula is possible through conic sections k 1 , k 2 , where the variation upward or downward from the exact value of R a  according to the above formula should not exceed the maximum deviation of 5-10%, wherein the closer the nozzle 3 the smaller is the permissible variation. The length l z  of the cylindrical intermediate section C should amount maximally to 0.3 times the overall length l k  of the cyclone. The length of l t  of the cylindrical entrance section is equal to 4 to 7 times the inner radius of withdrawal pipe 5. The inside radius of the withdrawal pipe for the lightweight substances should be equal to (0.3 to 0.4)·R a . This condition applies specifically to the initial area of the entrance end of the withdrawal pipe 5. The cylindrical intermediate section C could have an approximately 10% greater (C&#39;) or 10% smaller (C&#34; ) radius than the beginning radius R a  of the lower part A and to the length of which there is applicable a length l z , where l z  =(0 to 0.3)l, or l z  =(0 to 0.31)l k . 
     According to FIG. 3, the lower part of the withdrawal pipe 5&#39; may have a slightly conic like design with a cone angle between 0 degrees and 6 degrees, based on one side. The radius of the entrance part B&#39; according to FIG. 3 is 20 to 30% larger than the beginning radius R a  of the lower part A. 
     Approximately the same diameter is used for the separating space 8 for the lightweight substances, which is provided with an upper baffle plate 9 arranged opposite the discharge opening of the conic withdrawal pipe 5&#39; for the lightweight substances. 
     FIG. 2 additionally illustrates that by &#34;truncating&#34; the overall length of the cyclone, on the nozzle body 4, the outlet diameter of the nozzle body D 1 , D 2 , D 3  with the gradually decreasing value at overall lengths of the cyclone part l k1 , l k2 , and l k3  is obtained. 
     It is understood, naturally, that the outlet end of the hydrocyclone for the heavy fraction empties in a space that is sealed from the air. To that end, a collection container may be provided and the nozzle diameter adapted to the required withdrawal rate by the mentioned &#34;truncation&#34; of the overall length of the cyclone. 
     On the other hand, the withdrawal end for the heavy fraction may also empty in a chamber 12 to which a withdrawal line 14 is connected. A throttle valve 13 may be provided in this withdrawal line enabling a control of the withdrawal rate by variation of the pressure. 
     While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.