Abstract:
A mold (for producing molded blocks with at least one lateral face which has a texture, wherein the mold comprises at least one flexible belt, wherein the flexible belt surrounds at least one mold wall of the mold lower part that delimits the mold cavity in order to act on the material for producing the molded block that is received in the mold cavity, and in order in so doing to impress a texture on at least one of the lateral faces of the molded block, wherein the flexible belt can be moved relative to the mold lower part and wherein the flexible belt is mounted in such a way that it moves around the mold wall when the molded block is ejected from the mold cavity. Here, the mold comprises an active auxiliary device by means of which a rolling resistance of the flexible belt can be varied.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/EP2011/001914 filed Apr. 15, 2011, which designated the United States, and claims the benefit under 35 USC §119(a)-(d) of German Application Nos. 10 2010 015 516.0 filed Apr. 16, 2010 and 10 2010 033 678.5 filed Aug. 6, 2010, the entireties of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a mold for producing molded blocks and a device for producing molded blocks. 
       BACKGROUND OF THE INVENTION 
       [0003]    A mold for producing molded blocks is known from U.S. Pat. No. 7,021,919 B2. This mold for producing molded blocks with at least one lateral face which has a texture comprises a mold cavity which has openings at its opposite ends in order to receive a material for producing a molded block through its upper opening and to discharge through its lower opening a molded block formed in the mold cavity from the material, and furthermore comprises at least one flexible belt, wherein the flexible belt surrounds at least one mold wall of the mold lower part that delimits the mold cavity in order to act on the material for producing the molded block that is received in the mold cavity, and in order in so doing to impress a texture on at least one of the lateral faces of the molded block, wherein the flexible belt can be moved relative to the mold lower part and wherein the flexible belt is mounted in such a way that it moves around the mold wall when the molded block is ejected from the mold cavity. Such a mold or a device which operates with such a mold is intended to be improved in terms of the quality of the imprinted surface portion of the molded blocks produced. 
       SUMMARY OF THE INVENTION 
       [0004]    It is an object of the invention to propose a mold or a device in which the texture on the surface portion of the molded block is not damaged during stripping. 
         [0005]    The present invention makes provision to equip the mold with an active auxiliary device by means of which a rolling resistance of the flexible belt can be varied. As a result, it is possible during the ejection or stripping of the molded block formed in the mold cavity to avoid a relative movement between the molded block and the flexible belt that impairs the texture of the molded block, since, given a reduction in the rolling resistance of the flexible belt, the molded block must transmit by way of its imprinted texture at best small forces on the flexible belt in order to cause the flexible belt to run around the mold wall while the mold lower part is drawn off upwardly from the molded block. The essence of the invention is therefore to avoid shear forces between the texture formed into the molded block and the texture of the flexible belt bearing against it by means of an active auxiliary device which facilitates a rotation or a rolling of the flexible belt around the mold wall after a filling and compaction of the material such that, for stripping, a substantially lower force is sufficient in order to move the flexible belt. By switching between a difficulty of movement of the flexible belt during filling and compaction to an ease of movement of the flexible belt during demolding, it is possible that the belt has optimum properties for each of the three manufacturing steps of filling, compaction and stripping. During filling and compaction, the difficulty of movement of the flexible belt prevents an unwanted displacement of the belt through the material flowing into the mold cavity or through the compaction of the material situated in the mold cavity, it being the case that any displacement of the belt would result in an impairment of the desired structure of the molded block. During stripping, the ease of movement of the belt prevents any tearing or displacement of the texture imprinted on the molded block. While the molded block is ejected from the mold cavity, the active auxiliary device brings about a reduction in the rolling resistance of the flexible belt which the latter puts up to rolling around the mold wall, and consequently it is possible to achieve a reduction in a drive force which must be transmitted from the molded block to the flexible belt during ejection in order to rotate the belt around the mold wall. 
         [0006]    According to the present invention, provision is made to equip the active auxiliary device with a tensioning device by means of which a tension of the flexible belt can be varied, wherein the flexible belt is held in a tensioned position during a filling of the mold cavity and during a compaction of the material in the mold cavity, and wherein the flexible belt is loosened into a relaxed position by the tensioning device during the stripping or ejection from the mold cavity of the molded block formed from the material. By means of a tensioning or relaxing operation which can be implemented in a mechanically simple manner, the force which is required to rotate or roll the flexible belt around the mold wall can be controlled in steps or steplessly by changing the tensioning force. Here, the tensioning device is formed in particular by one or more tensioning elements which are formed in particular as slide pieces or tensioning rollers, wherein the tensioning element or elements tension the flexible belt with at least two tensioning forces of different sizes. 
         [0007]    Furthermore, provision is made according to the invention to equip the active auxiliary device with a drive device by means of which the flexible belt is driven during the stripping or ejection from the mold cavity of the molded block formed from the material, wherein the drive device comprises in particular at least one drive means which is formed in particular as a drive roller. With such a design of the auxiliary device, it is possible to reduce to a minimum the forces which are transmitted between the molded block and the flexible belt during stripping if the belt is driven by the drive device with exactly the speed with which the mold lower part is lifted away from the molded block during stripping, wherein the mold lower part and a portion of the flexible belt that bears against the molded block move in opposite directions. To achieve an effective drive, there is provided in particular a toothing between the flexible belt and the at least one drive means. As a result, unwanted slipping is avoided during driving. 
         [0008]    Furthermore, the invention provides to equip the active auxiliary device with a releasable brake by means of which the flexible belt is blocked during filling and compaction or braked and by means of which the flexible belt is released in its rotation about the mold wall during the stripping or ejection of the molded block formed from the material. As a result, it is possible to allow a behavior of the flexible belt that is optimally tailored to the requirements during the manufacturing steps of filling, compaction and stripping. In such a design variant of the mold, it is provided in particular to guide the flexible belt at opposite ends of the mold wall over smooth-running rollers so as to require low driving forces for the belt in the unbraked state of the belt. 
         [0009]    Furthermore, the invention provides to provide the flexible belt with cavities, wherein the cavities are arranged in particular in regions in which a thickness of the flexible belt lies above an average thickness of the flexible belt and is in particular more than 1.5 times the average thickness of the flexible belt. As a result, the belt obtains over its whole length a uniform flexibility which is independent of its thickness at individual points. This leads to a uniform circulation behavior in which, independently of the respective position of the belt, an approximately uniform drive force is sufficient to rotate the belt. 
         [0010]    The present invention also provides to embed in the flexible belt round cords which run annularly around the mold wall which the belt surrounds, wherein the round cords are embedded in particular over the whole width of the flexible belt and in particular have identical spaces from one another. The round cords make it possible to avoid a constriction of the flexible belt such that the latter has a uniform expansion behavior over its whole width and as a result can imprint its texture on the molded block without distortion in the edge regions. 
         [0011]    According to the present invention, provision is furthermore made to design the flexible belt with a first inner layer and a second outer layer, wherein the outer layer forms the texture and wherein the inner layer forms a sliding belt with a uniform thickness. As a result, it is possible to form the belt optimally from the requirements of uniform sliding or rolling around the mold wall and impressing a distortion-free texture on the molded block. 
         [0012]    According to the invention, the mold comprises a seal which bears against the flexible belt in the region of the upper opening of the mold cavity in order to upwardly seal the mold cavity filled with material together with the pressure piece acting on the material. As a result, optimum sealing of the pressure piece of the punch and the mold lower part is achieved in particular in the region of the flexible belt. 
         [0013]    Furthermore, the invention provides to equip the mold with a strip which, during filling and compaction, seals the lower opening of the mold cavity toward the mold wall which is surrounded by the flexible belt, and forms a bevel on the resulting molded block, wherein the strip is moved out of the mold cavity for stripping the molded block. This makes it possible for an edge of the molded block to be produced that adjoins the belt in the region of the production bed to be formed with a bevel and to avoid the formation of a burr. 
         [0014]    The invention also provides to equip the mold with a pressing device which bears against the flexible belt when the molded block is ejected from the mold cavity. As a result, a smooth running of the flexible belt is achieved and its tension in the load strand is made more uniform during demolding. 
         [0015]    The device according to the present invention for producing molded blocks comprises a block molding machine and a mold with a mold lower part for use in the block molding machine and a mold upper part, wherein the block molding machine comprises a vibrating table on which the mold lower part rests during filling and compaction, wherein the block molding machine comprises a vertically moveable load to which the mold upper part is fastened, wherein the mold lower part can likewise be moved in the vertical direction by the block molding machine. Such a block molding machine having a correspondingly designed mold makes it possible to produce molded blocks having a texture of high quality. 
         [0016]    For the purposes of the present invention, a texture or a textured lateral face is understood to mean a lateral face with elevations and depressions, wherein the elevations and depressions extend with their normals perpendicular to a direction in which the molded block is demolded from the mold lower part. 
     
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
         [0017]    Further details of the invention are described in the drawing with reference to schematically illustrated exemplary embodiments. 
           [0018]      FIG. 1   a  shows a schematic view of a device for producing molded blocks which comprises a block molding machine and a mold; 
           [0019]      FIG. 1   b  shows the mold lower part of the mold in plan view; 
           [0020]      FIG. 1   c  shows a section through the mold lower part shown in  FIG. 1   b;    
           [0021]      FIGS. 2   a - 2   d  show a second exemplary embodiment of an active auxiliary device which comprises a tensioning device; 
           [0022]      FIGS. 3   a - 3   h  show a third exemplary embodiment of an active auxiliary device which comprises a tensioning device; 
           [0023]      FIG. 4  shows an exemplary embodiment of an active auxiliary device which comprises a drive device; 
           [0024]      FIG. 5  shows an exemplary embodiment of an active auxiliary device which comprises a braking device; and 
           [0025]      FIG. 6   a - 6   c  show a mold with a scraping device, a seal and a strip. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]      FIG. 1   a  depicts in a schematic side view a block molding machine  1  in which the mold  2  according to the invention is used, wherein a device  3  according to the invention comprises the block molding machine  1  and the mold  2 . The mold  2  comprises a mold lower part  4  and a mold upper part  5 . The block molding machine  1  comprises a mold bed  6  which substantially consists of a vibrating table  7  and a production board  8 . Furthermore, the block molding machine  1  comprises a load  9  to which the mold upper part  5  is fastened and by means of which the mold upper part  5  can be moved in vertical directions x, x′. The mold lower part  4  can likewise be moved on columns  10  of the block molding machine  1  in the vertical directions x, x′. In order to fill a mold cavity  11  formed in the mold lower part  4  using a filling carriage (not shown), the mold lower part  4  lies on the production board  8  which itself rests on the vibrating table  7 . At opposite ends  12 ,  13  of the mold lower part  4 , the mold cavity  11  has an upper opening  14  and a lower opening  15 . During filling, material  16 , which preferably takes the form of concrete, is filled through the upper opening  14  into the mold cavity ( 11 ) in order then to be compacted by means of vibrating the vibrating table  7  and by means of pressure which is applied by a pressure piece  17  of the mold upper part  5 . To eject a molded block (not shown here) formed from the material  16 , the mold lower part  4  is raised vertically upwardly into the arrow direction x, with the molded block being prevented from making an upward movement in the arrow direction x by the pressure piece  17 . The molded block completely demolded from the mold cavity  11  is then removed from the block molding machine  1  on the production board  8 . The mold lower part  4  and the mold upper part  5  then move back into the position shown in  FIG. 1   a.    
         [0027]      FIG. 1   b  depicts in plan view the mold lower part  4  shown in  FIG. 1   a . It can be seen in this view that one of four mold walls  18  to  21  is enclosed by a flexible belt  22 . According to the invention, it is also provided that a plurality of mold walls are completely or partially enclosed by flexible belts. 
         [0028]    In the sectional view shown in  FIG. 1   c , which shows the mold lower part  4  corresponding to the section line Ic-Ic indicated in  FIG. 1   b , it can be seen how the flexible belt  22  runs around the mold wall  21  as an endless belt or as a loop which can be rotated around the mold wall  21  or can be rolled around the mold wall  21 . This sectional view now depicts the molded block  23  mentioned for the purposes of illustration. Here, the molded block  23  is shown during demolding or stripping, with the molded block  23  being held by the pressure piece  17  on the production board  8  and the mold lower part  4  moving upwardly in the arrow direction x. To facilitate and optimize this stripping process, the mold  2  or the mold lower part  4  or the mold wall  21  comprises an active auxiliary device  24  by means of which it is possible to reduce a rolling resistance which the flexible belt  22  has during a rotation in a counterclockwise direction of rotation w about the mold wall  21 , in order to keep low a drive force F 23  which the molded block  23  has to transmit to the flexible belt  22 , and to make possible a destruction-free ejection or stripping of the molded block  23 . For the purposes of the invention, a molded block  23  stripped in a destruction-free manner is intended to mean a molded block  23  which has on a lateral face  25  a texture  26  which is formed as a negative of a texture  27  of the flexible belt  22 , wherein the pattern impressed during the production is obtained largely nondeformed after stripping, and in particular elevations  28  and depressions  29  of the texture  26 , the normals N 28  and N 29  of which are perpendicular to a direction E of the demolding, are not substantially deformed during the demolding operation. For this purpose, the active auxiliary device  24  comprises a tensioning device  30 . This substantially comprises a pneumatically or hydraulically operated cylinder  31  and a tensioning means  32  which is formed in particular by at least one tensioning roller  33 . For stripping, a tensioning force F 31  with which the cylinder  31  presses the tensioning means  32  in the arrow direction x is then reduced, with the result that the drive force F 23  which the molded block  23  must transmit via its texture  26  to the flexible belt  22  in order to rotate the latter around the mold wall  21  is reduced to such an extent that the still soft texture  26  of the molded block  23  does not experience any visible deformation which impairs the desired appearance of the molded block  23  as a result of the driving of the belt  22  during the stripping operation. In order to compact or fill and compact the mold cavity  11  with material, the flexible belt  22  is then tensioned again by the tensioning device  30  against a deflection means  34 , wherein the deflection means  34  is formed by at least one deflection roller  35 . This ensures that the belt  22  maintains its position during filling and compaction and is not displaced and that the belt runs in the mold cavity  11  without waves or bulges. Consequently, the active auxiliary device  24  makes it possible for the flexible belt  22  to be able to meet the different requirements for the individual manufacturing steps. Namely, the belt  22  is tightly tensioned and can be displaced with difficulty during filling and compaction, and the belt  22  can run around the mold wall  21  with minimum resistance during stripping. 
         [0029]      FIGS. 2   a  to  2   d  show a second exemplary embodiment of an active auxiliary device  24  which comprises a tensioning device  30 . To clearly illustrate the auxiliary device  24 , substantially only one partition wall  21 , which is enclosed by a flexible belt  22 , is shown of a mold lower part  4 . This partition wall  21  is, for example, screwed to the remaining structure  36  of the mold lower part  4 , the structure being indicated here only in  FIGS. 2   a  and  2   c .  FIGS. 2   a  and  2   b  illustrate the partition wall  21  with a completely relaxed flexible belt  22 , with, of course, the belt  22  bulging into a mold cavity  11  only—as shown—when no molded block is present in the mold cavity  11 . In the sectional view through  FIG. 2   a , which is shown in  FIG. 2   b , it can be seen that a tensioning means  32  is designed as a tensioning slide  37 .  FIGS. 2   c  and  2   d  show the flexible belt  22  in a tensioned position in which the tensioning slide  37  tensions the belt  22  against a deflection roller  35  and for this purpose has been moved downwardly in the arrow direction x. In the tensioned position, the belt  22  then runs flat without bulging, apart from its texture  27 , in the region of the mold cavity  11 . 
         [0030]      FIGS. 3   a  to  3   h  show a third exemplary embodiment of an active auxiliary device  24  which comprises a tensioning device  30 . To clearly illustrate the auxiliary device  24 , substantially only a partition wall  21 , which is enclosed in  FIGS. 3   e  and  3   g  by a flexible belt  22 , is shown of a mold lower part  4 .  FIG. 3   a  shows a section through the partition wall  21 , with, for illustrative purposes, a representation of a flexible belt which surrounds the partition wall  21  having initially been dispensed with. As is evident from the side view shown in  FIG. 3   b , the tensioning device  30  comprises three pneumatically operated cylinders  31  which each move a tensioning slide  37 . To the sides of the outer tensioning slides  37  and between the tensioning slides  37 , there are arranged four running rollers  38  on the partition wall  21 . By means of the cylinders  31  the tensioning slides  37  can be lowered from a level I in which they are above the running rollers  38  to a level II in which the tensioning slides  37  are below the running rollers  38 . 
         [0031]      FIGS. 3   c  and  3   d  now show the already-mentioned flexible belt  22  in a perspective single view and in a detail view. The flexible belt  22  has a width B 22  and is tensioned in its tensioned position with a tensioning force F by the active auxiliary device  24 . Provision is made here for the tensioning force F to be located in a region which, depending on the width B 22 , is approximately between the value F=50 N/cm×B 22  and the value F=100 N/cm×B 22 . Consequently, for a flexible belt with a width of 50 cm, tensioning forces between 2,500 N to 5,000 N are obtained. 
         [0032]      FIG. 3   d  shows a section through the belt  22  in a schematic representation. The belt  22  consists of two layers  39  and  40  connected to one another. The inner layer  39  is designed as a sliding belt  41  having a uniform thickness D 39  in order to ensure a smooth and jolt-free running of the flexible belt  22 . The outer layer  40  forms as a relief belt  42  a texture  27  which is transmitted to the molded block. In order to keep the belt  22  uniformly flexible in spite of the differences between its maximum thickness D 22  and its minimum thickness d 22 , the belt  22  has cavities  43  which reduce the wall thickness in certain portions and thus increase the flexibility of the belt  22 . The two layers  39  and  40  of the belt  22  are connected to one another securely against displacement. 
         [0033]    Analogously to the illustrations of  FIGS. 3   a  and  3   b , in  FIGS. 3   e  and  3   f  the tensioning slides  37  are now lowered to the level  22  such that the running rollers  38  project beyond the tensioning slides  37 . As a result, the flexible belt  22  which is shown in  FIG. 3   e  can be rolled over the running rollers  38  in the relaxed position and thus can be rotated or rolled particularly easily around the partition wall  11  in the relaxed position. 
         [0034]    In the tensioned position—as is illustrated again in  FIGS. 3   g  and  3   h —the flexible belt  22  is tensioned by the three tensioning slides  37  and is here lifted off by them from the running rollers  38  such that it is made more difficult for the belt  22  in the tensioned position to run around the partition wall  21  as a result of the increased tension and the increased friction. To strip or eject a molded block, the active auxiliary device  24  is then relaxed such that the flexible belt can run around the partition wall  21  over the running rollers  28  without or with little tension. 
         [0035]      FIG. 4  shows an exemplary embodiment of an active auxiliary device  24  which comprises a drive device  44 . To clearly illustrate the auxiliary device  24 , substantially only a partition wall  21 , which is enclosed by a flexible belt  22 , is shown of a mold lower part  4 . The flexible belt  22  which surrounds the partition wall  21  is pretensioned over two deflection rollers  45  and  46 . The drive device  44  comprises a pneumatically, hydraulically or electrically driven motor  47  which moves a friction wheel or a drive roller  48  which acts on the upper deflection roller  45 . For stripping or ejecting a shaped block (not shown), the belt  22  is driven over the upper deflection roller  45  corresponding to the demolding rate such that the molded block does not have to transmit any drive forces which impair the quality of its texture. The drive device  44  further offers the possibility, given a corresponding design, for example, of a gearing, to block the belt  22  during filling and compaction. 
         [0036]      FIG. 5  shows an exemplary embodiment of an active auxiliary device  24  which comprises a braking device  49 . To clearly illustrate the auxiliary device  24 , substantially only a partition wall  21 , which is enclosed by a flexible belt  22 , is shown of a mold lower part  4 . The flexible belt  22  which surrounds the partition wall  21  is pretensioned over two deflection rollers  45  and  46 . By selecting smooth-running bearings for the deflection rollers  45 ,  46 , only a very small drive force is necessary to be able to rotate the belt  22  around the mold wall  21 . As a result, it is possible, during stripping, to drive the belt  22  by means of the positive connection between the texture of the molded block and the texture of the belt when the braking device  49  is released. Correspondingly, for filling and compaction, the belt  22  is blocked by the braking device  49  in order to avoid an unwanted movement. The braking device  49  comprises a brake shoe  50  which can be moved by means of a cylinder  31  for braking against the upper deflection roller  45 . This is indicated by dashed lines. To release the belt  22 , the brake shoe  50  can be withdrawn from the upper deflection roller. 
         [0037]      FIGS. 6   a  to  6   c  show in various positions a mold  2  with a pressing device  51 , a seal  52  and a strip  53 . The pressing device  51  comprises a lever  54  which bears against a flexible belt  22  of the mold  2  during the stripping operation in order to ensure a uniform running of the flexible belt  22  during demolding. For this purpose, the lever  54  is pivotably attached to a mold upper part  5  of the mold  2  and, during the filling and during the compaction, is situated in a protected position above a pressure plate  17  which compacts material  16  in the mold cavity  11  to form a molded block  23 . As soon as the flexible belt  22  moves upwardly in the arrow direction x past the pressure plate  17  during demolding and comes into an action region of the lever  54 , the lever is pivoted by means of a pneumatic cylinder  55  about a rotary bearing  56  with its contact end  57  against the flexible belt  22  and holds the latter in position during the further rotation by means of pressure. The seal  52  is fastened to a cover plate  58  which is positioned between the pressure piece  17  and the flexible belt  22  during compaction. By means of a pressure p with which the material  16  which is compacted acts on the lip-shaped seal  52 , the latter bears against an irregular texture  27  of the belt  22  and brings about sealing during the compaction operation. Between a production board  8  and the flexible belt  22 , use is made of a strip  53  in a mold cavity  11  of the mold  2 , the strip being positioned prior to a filling of the mold cavity  11 . A bevel is formed on the resulting molded block  23  by means of the strip  53  and consequently the formation of a widening of the molded block  23  in the arrow direction y toward the flexible belt  22  is prevented. 
         [0038]    The invention is not limited to illustrated or described exemplary embodiments. Rather, it comprises developments of the invention within the scope of the claims. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           1  Block molding machine 
           2  Mold 
           3  Device 
           4  Mold lower part 
           5  Mold upper part 
           6  Mold bed 
           7  Vibrating table 
           8  Production board 
           9  Load 
           10  Column 
           11  Mold cavity 
           12 ,  13  End of  4   
           14  Upper opening of  11   
           15  Lower opening of  11   
           16  Material 
           17  Pressure piece 
           18 - 21  Mold walls 
           22  Flexible belt 
           23  Molded block 
           24  Active auxiliary device 
           25  Lateral face 
           26  Texture of  23   
           27  Texture of  22   
           28  Elevations of  26   
           29  Depressions of  26   
           30  Tensioning device 
           31  Cylinder 
           32  Tensioning means 
           33  Tensioning roller 
           34  Deflection means 
           35  Deflection roller 
           36  Structure  3   
           37  Tensioning slide 
           38  Running roller 
           39  Inner layer 
           40  Outer layer 
           41  Sliding belt 
           42  Relief belt 
           43  Cavity 
           44  Drive device 
           45 ,  46  Deflection rollers 
           47  Motor 
           48  Drive roller, friction wheel 
           49  Braking device 
           50  Brake shoe 
           51  Pressing device 
           52  Seal 
           53  Strip 
           54  Lever 
           55  Pneumatic cylinder 
           56  Rotary bearing 
           54  Contact end of  54   
           58  Cover plate  58   
         B 22  Width of  22   
         D 39  Thickness of  39   
         D 22  Maximum thickness of  22   
         d 22  minimum thickness of  22   
         E Direction of demolding 
         F Tensioning force 
         F 23  Drive force of  23  on  22   
         F 31  Tensioning force 
         N 28 , N 29  Normal of  28  or  29   
         p Pressure of  16  on  52   
         x, x′ Vertical directions 
         y Arrow direction 
         I Level of  37   
         II Level of  37