Abstract:
A multipath valve for distributing and/or dividing at least one flow of polymer melt during the manufacture and processing thereof, wherein melt flows through all internal chambers of the valve during all conditions of operation. At least one rotary disc is rotatably mounted on an axle bolt between a front plate and a rear plate which are each provided with openings serving as inlets and outlets for the polymer melt. The rotary disc is provided with circular segment-shaped ducts having a width and end radii corresponding to an inner width of the openings, wherein the ducts have center lines which are located on a reference circle extending through the centers of the openings, and wherein the positions of the ducts are adjustable in accordance with a desired flow direction of the polymer melt.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a multipath rotary disc valve for distributing polymer plastics melts of high molecular weight.  
           [0003]    2. Description of the Related Art  
           [0004]    In the manufacture and processing of polymers, for achieving a flexible process it is frequently necessary to selectively distribute melt flows to different processing stages.  
           [0005]    The distribution of melt flows of plastics having higher viscosities, for example, the distribution of polymer melts of high molecular weight, from a principal line to different distributor lines still causes technical problems today. For solving these problems, multipath valves are usually proposed in which the respective flow direction is opened or closed by pistons. For example, U.S. Pat. No. 5,211,845 describes a polymer valve in which the closing pistons are arranged in a V-shaped configuration in order to keep the dead space occurring during the exchange of the flow direction as low as possible. In connection with the alternating flow into different filter chambers, U.S. Pat. No. 5,928,523 proposes a valve construction in which three valve chambers are used which must be emptied and rinsed each time the initial positions are changed.  
           [0006]    EP-0 962 299 A1 describes a multipath plug-type valve in which the drive is located outside of the heating unit.  
           [0007]    These commercially available valves, such as multipath piston valves or plug-type valves, have the disadvantage that the spaces between contact surfaces and the valve chamber itself contains residues of the melt when a flow direction is closed off, wherein these residues are thermally decomposed when remaining for a long period of time at process temperature, so that carbonized decomposed products reach the polymer melt when the flow direction is used once again. In addition, sealing of the valves in piston valves can be effected only through fitted seats which are adjusted during the manufacturing process and by forcing in the plug in the case of plug-type valves. Polymer residues are also deposited in the fitted seats of piston valves, wherein these polymer residues are decomposed and reach the flow of melt when the melt is moved. Plug-type valves have the tendency to be tight to operate because of the contact pressure between surfaces which is difficult to control.  
         SUMMARY OF THE INVENTION  
         [0008]    Therefore, it is the primary object of the present invention to provide a multipath valve which is free of dead space to be used for distributing melt flows in the manufacture or processing primarily of thermoplastic polymers, wherein the valve makes it possible to conduct the melt in a circulation line, directly to the output or through a casting nozzle, or which makes it possible to optionally separate or connect the valve to different melt circulations without producing melt residues.  
           [0009]    To be able to carry out such operations as they are frequently desired in the discontinuous manufacturing processes of polymers, without the usual disadvantages of deposited, thermally decomposed melt residues in the valve chambers or in the fits required necessarily for the mobility of the closing elements, the present invention proposes a multipath valve in which the melt flows through the interior of the valve in all conditions of operation, so that the formation of melt residues is always prevented.  
           [0010]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the descriptive matter in which there are described preferred embodiments of the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0011]    In the drawing:  
         [0012]    [0012]FIG. 1 is an elevational view of a three-way valve according to a first embodiment of the invention with a rotary disc, shown in a position for feeding an outlet;  
         [0013]    [0013]FIG. 2 is a special sectional view of the valve of FIG. 1;  
         [0014]    [0014]FIG. 3 is an elevational view of the valve of FIGS. 1 and 2, shown after switching to a position for feeding the outlet;  
         [0015]    [0015]FIG. 4 is a special sectional view of the valve of FIG. 3;  
         [0016]    [0016]FIG. 5 is an elevational view of a second embodiment of the three-way valve equipped with two parallel rotary discs, shown in an initial position of the rotary discs;  
         [0017]    [0017]FIG. 6 is a special sectional view of the valve of FIG. 5;  
         [0018]    [0018]FIG. 7 is an elevational view of the second embodiment of the valve of FIG. 5, shown with the rotary discs in a different position;  
         [0019]    [0019]FIG. 8 is a special sectional view of the valve of FIG. 7;  
         [0020]    [0020]FIG. 9 is an elevational view of the second embodiment of the three-way valve of FIG. 5, shown with the rotary discs in yet another position;  
         [0021]    [0021]FIG. 10 is a special sectional view of the valve of FIG. 9;  
         [0022]    [0022]FIG. 11 is an elevational view of a third embodiment of the multipath valve according to the present invention provided with two inlets and two outlets and two rotary discs, shown in a first switching position;  
         [0023]    [0023]FIG. 12 is a special sectional view of the valve of FIG. 11;  
         [0024]    [0024]FIG. 13 is an elevational view of the third embodiment of the multipath valve of FIG. 11 shown with the rotary discs in different positions;  
         [0025]    [0025]FIG. 14 is a special sectional view of the valve of FIG. 13;  
         [0026]    [0026]FIG. 15 is an elevational view of the third embodiment of the multipath valve of FIG. 11, shown after another change of the positions of the rotary discs;  
         [0027]    [0027]FIG. 16 is a special sectional view of the valve of FIG. 15;  
         [0028]    [0028]FIG. 17 is an elevational view of a fourth embodiment of the valve with two inlets and two outlets and two rotary discs, shown in the open position; and  
         [0029]    [0029]FIG. 18 is a special sectional view of the valve of FIG. 17.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    [0030]FIGS. 1 through 4 of the drawing show a three-way valve with a rotary disc which in a first position thereof opens the flow path of the melt from an inlet opening to a first outlet opening. After changing the position of the rotary valve, this flow path is closed and the flow path from the inlet opening to a second outlet opening is opened. Valves of this type can be used, for example, for discharging a melt and for granulation; they can be used in connection with exchangeable filters and make it possible to remove samples a desired.  
         [0031]    [0031]FIGS. 1 and 2 show a front plate  1  of a valve housing which is clampingly connected to the rear plate  2  of the housing by means of clamping bolts  3  and nuts  4 . As shown in FIGS. 1 and 2, the rear plate  2  is equipped with an axle bolt  5  which concentrically supports a rotary disc  6  mounted between the front plate and the rear plate. The circumference of the rotary disc  6  is provided with a toothed rim  7  which makes it possible to adjust the rotary disc by means of a pinion of a drive unit, not shown in the drawing, which engages in the toothed rim  7 .  
         [0032]    The front plate  1  is provided with an inlet opening  8  for the polymer melt and the front plate  1  and the rear plate  2  each have an outlet opening, wherein the angle distance between the first outlet opening  9  and the inlet opening  8  is equal to the angle distance between the second outlet opening  10  and the inlet opening  8 .  
         [0033]    The rotary disc  6  contains a melt duct  11  which has the shape of a segment of a circle and whose center line extends along a reference circle  19  which includes the center points of the inlet opening  8  and of the outlet openings  9  and  10 , wherein the length of the melt duct  11  corresponds to the distance between the inlet and outlet openings  8 ,  9  and  10 , and wherein the ends of the melt duct  11  are rounded off with a radius equal to the radius of the inlet and outlet openings  8 ,  9  and  10 .  
         [0034]    For sealing the housing, the inner surfaces of the front plate  1  as well as of the rear plate  2  are carefully ground, hardened and, if necessary, surface-treated, as is the case in the rotary slide  6  which has parallel ground, hardened and, if necessary, surface-treated surfaces. After placing the rotary disc  6  on the axle bolt  5 , the front plate  1  and the rear plate  2  are placed with their inner surfaces on the surfaces of the rotary disc  6  and are braced together by tightening the clamping nuts  4  by means of the clamping bolts  3  in such a way that the melt duct  11  is completely sealed relative to the outside, on the one hand, and the rotatability of the rotary disc  6  is maintained, on the other hand, wherein the force for adjusting the rotary disc  6  is applied by the pinion which was mentioned above but is not illustrated and which engages the toothed rim  7 ; or the forces applied by means of a ratchet and an adjusting lever, or by means of a hydraulic system. The clamping forces for bracing the front plate  1  against the rear plate  2  can be corrected by means of the clamping nuts  4 , wherein the external clamping forces are to be adjusted to the pressure prevailing in the valve in such a way that the pressing force required for the sealing action is always available.  
         [0035]    In dependence on the sequence of cycles of operation of the valve, it might be advantageous to subject the rotary disc  6  after a certain or predetermined time to a timed forward and backward movement in order to prevent any possible deposits of polymer melt on the sealing surfaces.  
         [0036]    The actual switching procedure is carried out as follows: In the position illustrated in FIG. 1, the rotary disc  6  is adjusted in such a way that its melt duct  11  extends from the inlet opening  8  to the outlet opening  9 , so that the polymer passing through the rotary disc is conducted through the first outlet  9 . When the rotary disc  6  is adjusted in the direction of arrow  12 , the rotary disc  6  rotates in a clockwise direction and its rearward end moves away from the outlet opening  9  and moves towards the inlet opening  9 , while its forward end is moved past the inlet opening  8  and reaches the outlet opening  10  of the second outlet, as illustrated in FIGS. 2 and 4 of the drawing. This concludes the switching of the valve; the only space which was filled by polymer melt is now still filled by polymer melt, wherein this melt is not stagnant and aging melt, but is melt which always flows from the inlet opening and through the melt duct  11 , so that the object of the present invention is met, i.e., aging and, thus, decomposed melt residues are avoided.  
         [0037]    The present invention is not limited to simple three-way valves which only act as change-over switches. Thus, the next embodiment is directed to a three-way valve equipped with two rotary discs, wherein this valve includes an inlet opening and two outlet openings, and wherein melt is conducted to the first outlet opening in a first position, melt is fed to the second outlet opening in a second position, and the flow of melt is distributed to both outlet openings in a third position. Such a three-way valve can be used, for example, for dividing a flow of melt, for removing samples, for a targeted controlled discharge of melt, for example, for granulation, for exchange filters or the like.  
         [0038]    This embodiment will now be described in detail with the aid of FIGS. 5 and 6. FIG. 5 shows a view of the three-way valve corresponding to FIG. 1, with a front plate  1  which is braced by means of clamping bolts  3  and clamping nuts  4  against the rear plate  2 , shown in FIG. 6. The rear plate  2  is equipped with an axle bolt  5  which extends through the bores of two rotary discs  13  and  14 . For adjusting the rotary discs  13  and  14 , the discs are surrounded by toothed rims  15  and  16 , wherein spur wheels  17  and  18  engage in these toothed rims for adjusting the rotary discs  13  and  14 , as seen in FIG. 8.  
         [0039]    The valve housing composed of front plate  1  and rear plate  2  is provided with an inlet opening  8  and two outlet openings  9  and  10 . As can be seen especially in the views of FIGS. 5, 7 and  9 , the inlet opening  8  and the outlet openings  9  and  10  are arranged on a common reference circle  19  in such a way that the outlet openings  9  and  10  are located by the same angle away from, but on different sides of, the radius intersecting the inlet opening  8 . The melt ducts  21  and  22  of the rotary discs  13  and  14  have the same width as the diameters of the connecting bores. The melt ducts extend from one connecting bore to the next connecting bore, wherein the semicircles at the end of the melt ducts correspond to the spaces defined by the connecting bores. This makes it possible that the ducts are utilized fully by the respective flow of melt without forming dead spaces.  
         [0040]    As already explained in connection with the first embodiment, the inner surfaces of the front plate  1  and of the rear plate  2  are exactly ground, hardened and, if necessary, further surface-treated. The same is true for the surfaces of the rotary discs  13  and  14  which are ground exactly parallel. After uniformly tightening the clamping nuts  4 , the front plate  1  and the rear plate  2  are braced against the surfaces of the rotary discs  13 ,  14  in such a way that a housing is provided which is sealed even in the case of high internal pressures, while the rotary discs can still be moved.  
         [0041]    The elevational view of FIG. 5 shows the inlet opening  8  of the front plate  1  and the second outlet opening  10  of the front plate  1 . The rear plate  2  is provided with the first outlet opening  9 . The rotary discs  13  and  14  are adjusted in such a way that their ducts  21  and  22  extend parallel to each other and from the inlet opening  8  to the first outlet opening  9 . This provides a connection between the inlet opening  8  and the outlet opening  9  through the ducts  21 ,  22 , wherein the polymer melt fully flows through this connection and the connection contains no dead spaces, so that no residues are possible.  
         [0042]    In order to switch the valve to the second outlet  10 , the two rotary discs  13  and  14  are rotated in the direction of arrow  12 . As a result, the ducts  21  and  22  are moved away from the first outlet opening  9  and now bridge the inlet opening  8  and the second outlet opening  10 . This once again results in a flow of melt without dead spaces which could hold back portions of the melt which could be thermally decomposed. FIG. 8 of the drawing shows the corresponding cross-sectional view which extends once again in the area of the ducts  21  and  22  along the reference circle  19  of the connections. FIG. 8 further shows spur gear wheels  17  and  18  which engage in the toothed rims  15  and  16  for driving the rotary discs  13  and  14 .  
         [0043]    The third position of switching the three-way valve of FIG. 5 is explained in FIGS. 9 and 10. The rotary disc  14  remains in its position already illustrated in FIGS. 5 and 6 and its duct  22  provides a first connection between the inlet opening  8  and the first outlet opening  9 . The rotary disc  13 , on the other hand, is moved in the direction of arrow  23 , so that its duct  21  provides a connection between the inlet opening  8  and the second outlet opening  10 . As a result, the flow of melt is conducted to both outlet openings, so that the flow of melt is divided within the three-way valve from one inlet to two outlets.  
         [0044]    Additional possibilities can be effected in a third embodiment which once again is a multipath valve with two rotary discs. In this case, two inlet openings and two outlet openings are provided, wherein, in a first switching position, the first inlet opening  8  is connected to the first outlet opening  9  and separately the second inlet opening  24  is connected to the second outlet opening  10 , so that two switched melt paths are created. In the second switching position of FIGS. 13 and 14, the second melt inlet  24  is closed, and the first inlet opening  8  is connected to both outlet openings  9  and  10  for dividing the flow of melt. In another switching position of FIGS. 15 and 16, both inlet openings  8  and  20  are connected to the first outlet opening  9  for mixing two flows of melt. Fields of application are, for example, a sequential connection of two otherwise separate circulations of melt, the possibility of intersecting flows of melt, and merging two flows of melt.  
         [0045]    Also in this embodiment, a front plate  1  and a rear plate  2  shown in FIGS. 11 and 12 are tightly braced together against two rotary discs  25 ,  26  in such a way that the rotary discs can still be rotated by means of a drive unit which acts on the toothed rims  27 ,  28  of the discs. As is the case in all other embodiments, there is also the possibility of adjusting the bracing force between the front and rear plates in accordance with a measurement or an indication; however, it is also possible to limit the rotation of the rotary discs by means of stops, so that end points of the movements of the discs are provided.  
         [0046]    As can be seen in the front view of FIG. 11 and the special sectional view of FIG. 12, the front plate  1  is equipped with a first inlet opening  8  and a first outlet opening  10 , while the rear plate  2  has a second inlet opening  24  and a second outlet opening  9 .  
         [0047]    [0047]FIGS. 11 and 12 further show that, in a first position of the multipath valve, the connection openings  8  and  10  of the front plate  1  are connected through the duct  29  of the rotary disc  25 , while simultaneously the duct  30  of the rotary disc  26  connects the two connection openings  9  and  24  of the rear plate  2 . Since the ducts have the same width as the connection openings, the length of the ducts corresponds to the distance between the connection bores, and the end portions of the ducts are adapted to the inside cross-section of the connection bores, no dead spaces are formed and there is no danger that decomposing melt residues are formed.  
         [0048]    [0048]FIGS. 13 and 14 show the same multipath valve after a first switching. The rotary disc  25  has remained in its original position, while the rotary disc  26  has been rotated in a clockwise direction in the direction of arrow  12  by a distance corresponding to the angle between the connection bores. Consequently, the duct  29  connects the inlet opening  8  to the outlet opening  10 ; however, in addition, the duct  30  of the rotary disc  26  forms a connection between the outlet opening  9  and the inlet opening  24 . For switching the valve further, the two rotary discs  25  and  26  are moved relative to the position of FIG. 13 by the distance corresponding to the angle between the connection openings in the direction of arrow  23  and, thus, the first inlet opening  8  as well as the second inlet opening  24  are connected to the outlet opening  9 , i.e., the melt is conducted to both inlet openings and is mixed in the multipath valve according to FIGS. 15 and 16 and is discharged only through a single outlet  9 . Also in this case, the ducts  29  and  30  are always filled with melt flow so that there are no possibilities that melt residues are stored, aged and decomposed.  
         [0049]    [0049]FIGS. 17 and 18 show a valve with inlet openings  8  and  24  and outlet openings  9  and  10 . The valve has rotary discs  25  and  31 , wherein the rotary disc  25  is provided with the duct  29  and the rotary disc  31  is provided with the duct  32 . The duct  29  extends completely through the rotary disc  25 , while the duct  32  only partially penetrates the rotary disc  21  in the form of a blind-end groove. Consequently, it is only possible to effect connections between the inlet  24  and the outlet  9 , on the one hand, and between the inlet  8  and the outlet  10 , on the other hand. Accordingly, the rotary discs  25  and  31  can only be used for opening and closing.  
         [0050]    The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.