Patent Publication Number: US-11654594-B2

Title: Method and system for demolding a flexible mold of dried wet-cast concrete products

Description:
FIELD 
     The present disclosure concerns concrete molded products manufacturing. More specifically, the present disclosure is concerned with a method and system for demolding a flexible mold of dried wet-cast concrete products. 
     BACKGROUND 
     Precast concrete is a well-known construction product produced by casting concrete in a reusable mold or “form”, which is then cured in a controlled environment. There are mainly two common methods of manufacturing precast concrete products: the dry-cast method and the wet-cast method. Both methods create a simulated natural cut stone look and are used in manufacturing a variety of products such as: paving stones, bricks, veneer bricks, retaining wall bricks, steppingstones, etc. 
     As its name would imply, wet-cast concrete is more liquid. It has a high slump, which gives it the ability to be poured from a mixer or hopper. Also, in wet-cast a rubber mold is used. In contrast, dry-cast concrete is very dry, has zero or near-zero slump, and the forms can be stripped as soon as the concrete has been consolidated. 
     The dry cast manufacturing process typically involves complex machinery. Dry-cast concrete contains only enough water to hydrate the cement. The mix is compressed in a mold with very high pressure and then cured on a rack before being palletized and processed. 
     To manufacture wet-cast products, concrete is poured into a flexible mold and then vibrated to release air bubbles out of the mix. The mold then gets stripped after the concrete has cured. 
     De-molding in wet-cast is usually done by raising the mold, face-down, from a table or conveyor, or by peeling the mold. 
     Automated systems and methods are known for peeling the mold, all including includes gripping an edge of the mold and moving it along an arcuate path away from the mold-receiving table, thereby forcing by gravity the dried concrete products therein to remain onto the table. Such known arcuate paths ranges from small arcs to semi-circle. 
     While such de-molding processes work fine with sufficiently large and heavy products, which simply stays on the table while the mold is removed, it has been found that smaller products get stuck in the mold. 
     This is caused by the concrete creating a vacuum on the mold, resulting in a tight connection between the products and the mold. 
     Another drawback of known automated methods and systems is that the demolding movement along a smooth path has been found to cause uncontrolled ejection or stucking of the products in cases of differently sized products in a same mold or depending on the geometry of the products. 
     It results that current automatic demolding of wet-cast concrete products, especially of relatively small products or of differently sized products in a same mold still requires extra labor and causes some of the products to broke when they uncontrollably fall from the mold. 
     A demolding method and system that is free of the above drawback is therefore desirable. 
     SUMMARY 
     The problem of wet-cast concrete products getting stuck or being uncontrollably ejected from a flexible mold during demolding is solved by moving the flexible mold through a passage, defined by both a mold-receiving surface and a rotatable mold-support distanced therefrom, while moving an edge of the flexible mold along an unsmooth path that includes at least one sharp point. 
     According to an illustrative embodiment, there is provided a method for demolding at least one flexible mold that is at least partially filled with dried wet-cast concrete products and that has a peripheral edge; the method comprising: 
     providing a table and a mold-support member so distanced from the table as to define a passage for the at least one flexible mold therethrough; the mold-support member being rotatable about an axis parallel to the passage to minimize friction in the passage; 
     receiving the at least one flexible mold on the table so that a portion of the peripheral edge extends out of the passage; and 
     moving the at least one flexible mold through the passage while moving the portion of the peripheral edge along an unsmooth path about the mold-support member; the unsmooth path including at least one sharp point. 
     According to another illustrative embodiment, there is provided a system for demolding at least one flexible mold that is at least partially filled with dried wet-cast concrete products and that has a peripheral edge, the system comprising: 
     a table defining a surface for receiving the at least one flexible mold thereon; 
     a mold-support member mounted to the table; the mold-support member being so distanced from the surface as to define a passage for the at least one flexible mold therethrough; the mold-support member being rotatable about an axis parallel to the passage to minimize friction in the passage; and 
     a mold-moving system including i) a mold-prehension mechanism that is adapted for gripping a portion of the peripheral edge of the at least one flexible mold and ii) a guiding system coupled to the mold-prehension mechanism for moving the mold-prehension mechanism along an unsmooth path about the mold-support member; the unsmooth path including at least one sharp point. 
     According to still another illustrative embodiment, there is provided a system for demolding at least one flexible mold that is at least partially filled with dried wet-cast concrete products and that has a peripheral edge, the system comprising: 
     a conveyor defining a surface for receiving the at least one flexible mold thereon; 
     a cylindrical rod mounted to the table; the cylindrical rod being so distanced from the surface as to define a passage for the at least one flexible mold therethrough; the cylindrical rod rotatable about an axis parallel to the passage to minimize friction in the passage; and 
     a mold-moving system including i) a gripping tool that is adapted for gripping a portion of the peripheral edge of the at least one flexible mold and ii) a robot arm for moving the gripping along an unsmooth path about the cylindrical rod; the unsmooth path including at least one sharp point 
     The action of removing the vacuum on a flexible mold having dried wet-cast concrete products therein will be referred to in the description and in the claims as ‘cracking’. 
     Other objects, advantages and features of embodiments of a method and system for demolding a flexible mold of dried wet-cast concrete products will become more apparent upon reading the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the appended drawings: 
         FIGS.  1 A- 1 D  are top perspectives of a system for demolding a flexible mold of dried wet-cast concrete products according to a first illustrative embodiment, further illustrating the operation thereof; 
         FIG.  2    is an isolated top perspective of a conveyor, part of the system from  FIG.  1   ; 
         FIGS.  3 A- 3 D  are side elevations of the system from  FIG.  1   , illustrating from another point of view the operational steps from  FIGS.  1 A- 1 D ; 
         FIG.  4    is an isolated perspective of a flexible mold of dried wet-cast concrete products shown for example in  FIGS.  1 A- 1 D ; 
         FIG.  5    is a graph illustrating the unsmooth path of an edge of the flexible mode during demolding thereof; 
         FIG.  6    is a flowchart of a method for demolding a flexible mold of dried wet-cast concrete products according to a first illustrative embodiment; and 
         FIG.  7    is a top perspective of a conveyor similar to the conveyor of  FIG.  1   , further comprising a sub-system for cracking molds prior to their demolding according to a second illustrative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, similar features in the drawings have been given similar reference numerals, and in order not to weigh down the figures, some elements are not referred to in some figures if they were already identified in a precedent figure. 
     The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one”. Similarly, the word “another” may mean at least a second or more. 
     As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, un-recited elements. 
     A system  10  for demolding a flexible mold  12  of dried wet-cast concrete products  14  according to a first illustrative embodiment will now be described with reference to  FIGS.  1 A- 1 D and  3 A- 3 D . As can be seen for example in  FIG.  1 A , the system  10  is configured to demold two (2) molds  12  at the same time. As can become more apparent upon reading the following description, the system  10  can be adapted to simultaneously receive and demold any number of molds  12 . 
     One of the molds  12 , prior to demolding, and therefore with dried wet-cast products  14  therein, is shown in  FIG.  4   . 
     The mold is made of rubber, polyurethane, or of another flexible material. 
     While the illustrated products are in the form of five (5) identical elongated bricks  14 , the system  10  can be used for demolding a flexible mold including a various number of identical or of differently shaped products. 
     The system  10  is integrated to a conveyor  16  for the molds  12 . 
     Turning now briefly to  FIG.  2   , the conveyor  16  is a pusher bar type conveyor that comprises a table defined by two elongated side plates  18  joined by a series of parallel transversal  20  shafts (only two shown), two pairs of legs  22 , each secured to a respective plate  18  near the longitudinal ends  24  and  26  thereof, and a conveying surface, defined on a first third of the table by a series of parallel longitudinal frame elements  28 - 30  and by a rectangular plate  32  that extends through the remaining surface of the table. 
     The conveyor  16  further comprises a product-conveying mechanism including pusher bars  34  (only two shown) that are mounted to the table for movement along a closed loop path around the table that passes in close proximity to the conveying surface. 
     The product-conveying mechanism includes i) two strands of roller chains  36  (shown schematically in  FIGS.  1 A- 1 D  by dashed lines), each one mounted on a respective plate  18 , on the inner side thereof, in a close loop fashion via a series of pulleys  38 , ii) a drive shaft  40  mounted to both plates  18  therebetween and a iii) motor (not shown) operatively coupled to the drive shaft  40 . Each roller chain  36  is coupled to the drive shaft  40  via a driving pulley  44 . 
     Each of the pusher bars  34  is secured to both strands of roller chains  36  therebetween via mounting brackets  45 . 
     The table, the conveying surface and the product-conveying mechanism are not limited to the illustrated embodiment, and can be adapted, for example, to the configuration of the mold  12 . Since pusher-bar conveyors are believed to be well-known in the art, the conveyor  16  will not be described herein in more detail. 
     According to another embodiment (not shown), the system  10  is integrated to another type of conveyor, such as, without limitations, a belt conveyor. 
     In addition to the table of the conveyor  16 , the system  10  for demolding flexible molds  12  comprises a support member  46 , in the form of a cylindrical rod, mounted to the conveyor  16 , and a mold-moving system  50  in the form of a robot  52  equipped with a pair of gripping tools  54 . 
     The cylindrical rod  46  is mounted to the conveyor  16  for pivotal movements, about the axis  47 , towards and away the conveying surface defined by the plate  32  via a mounting assembly  56 . This allows for an adjustment of the distance of the member  46  to the plate  32  depending on the thickness  58  of the molds  16  or of the pressure of the member  46  thereon. 
     As will be described hereinbelow in more detail, the interspace between the support member  46  and the plate  32  defines a passage  49  for the flexible molds  16  therethrough, the member  46  defining a support for the molds during demolding thereof. The adjustment of the distance between the member  46  and the mold-receiving surface  32  allows using the system  10  for various thickness of molds  16 . 
     Returning briefly to  FIG.  2   , the mounting assembly  56  will now be described in more detail. 
     The mounting assembly  56  includes a cylindrical rod  60 , defining the axis  47 , and that is rotatably mounted to both side plates  18  of the conveyor  16  therebetween via roller bearings  62 . Each of the roller bearings  62  is secured to a respective plate  18  via a mounting plate  64 . The support member  46  is secured to the rod  60 , parallel thereto and for solidary movement therewith, via a couple of spacer arms  66 , each secured to respective longitudinal ends of the rods  46  and  60 . 
     The mounting assembly  56  further includes a couple of gap adjusting mechanisms  68  for adjusting and maintaining the distance between the rod  46  and the surface  32 , depending on the thickness  58  of the molds  12 . 
     Each of the gap adjusting mechanism  68  is secured to a respective side plate  18  and to the rod  46  therebetween and comprises a) a linear cylinder  70  that is secured via its main body  71  to a respective plate  18  via a mounting bracket  72 , and b) a lever arm  74  that is secured to both rods  46  and  70  and pivotably mounted to the shaft  75  of the linear cylinder  70 . 
     As a person skilled in the art will now appreciate, the distance between the rod  46  and the mold-receiving surface  32 , can be adjusted by operating both linear cylinders  70  in unison. 
     According to the illustrated embodiment, the rod  46  is rotatably mounted to the spacer arms  66  so as to minimize friction onto the molds  12  when they exit the conveyor  16  through the interspace between the surface  32  and the rod  46 . 
     Other mounting assembly than the assembly  56  can be provided to mount the rod  46  to the conveyor  26  and more specifically to maintain an operating distance between the rod  46  and the surface  32  so that the rod  46  forces onto the conveying surface  32  the portion of the molds  12  that has not yet exited the conveyor  16  during demolding. 
     According to another embodiment, a mechanical stop (not shown) is provided to limit the movement of the rod  46 , such as on the cylinder  68  to limit its stroke. According to another embodiment (not shown), the rod  46  is mounted to the conveyor  16  so as to be positioned at a predetermined fixed distance from the surface  32 . 
     According to still another embodiment (not shown), the support member  46  take another form than the illustrated rod, such as for example, a series of roller bearings mounted to a shaft or a plate (not shown) at a predetermined distance from the surface  32 . 
     The robot  52  is in the form of a six (6) axes robot, such as, without limitations, those from the R-2000 series by Fanuc. According to another embodiment, the robot  52  has a different number than six operational axes and/or is from another manufacturer or type. 
     The pair of gripping tools  54  are attached to the robot  52  via a tooling mounting assembly  72 . One of the gripping tools  54  will now be described in more detail with reference to  FIGS.  1 A,  1 B and  3 B . 
     Each of the gripping tools  54  comprises a pair of grippers  73 , each comprising a mounting bracket  76  that mounts the gripping tool  54  to the assembly  72 , a fixed jaw member  78  secured to the bracket  76 , and a movable jaw member  80  that is mounted to the bracket  76  for pivotal movement towards and away the fixed jaw member  78 . Each gripping tool  54  further comprises an actuating mechanism  82  between the movable jaw member  80  and the mounting bracket  76  for selectively closing the movable jaw members  80  onto the fixed jaw members  78 . 
     The mounting bracket  76  generally defines a plane. The fixed jaw member  78  is in the form of an L-shaped member and includes a first portion  84  secured to the mounting bracket  76  so as to be parallel thereto, and a second portion  86  that extends from the first portion perpendicularly therefrom and that includes a friction pad  88  thereon. 
     The movable jaw member  80  includes a swivel arm  90  that is pivotably mounted to the mounting bracket  76  via a cylindrical shaft  92 . The shaft  92  is rotatably mounted to the bracket  76 , parallel thereto, via two roller bearings  94 . The swivel arm  90  is fixedly mounted to the shaft  92  at a first longitudinal end thereof. A contact element  96 , provided with a friction pad  98 , is secured to the arm  90  perpendicularly therefrom. 
     The actuating mechanism  82  includes a linear cylinder  100  that is pivotably mounted to the mounting bracket  76  and a lever arm  102  that is secured, at one of its longitudinal end, to the shaft  104  of the linear cylinder  100  for pivotal movement about an axis  105  parallel to the shaft  92 , and to the shaft  92  at its other longitudinal end. 
     In operation of the gripping tool  54 , the linear cylinder  100  is actuated to move in unison the movable jaw members  80  towards or away the corresponding fixed jaw members  78 , thereby allowing to grip or release a mold  12  by one of its edge  106 . 
     While the gripping tools  54  are illustrated as each having a single actuating mechanism  82  and a pair of grippers  73 , a different number of gripping tools and of actuating mechanism may be provided for each gripping tools  54 . Also, the configuration of the grippers and or of the actuating mechanism may be different than illustrated. For example, both jaw members of the gripping tool  54  can be mobile. 
     A system for demolding a flexible mold  12  according to another embodiment (not shown) is equipped with another mold prehension mechanism than a gripping tool, such as, without limitations, vacuum pads, pins or hooks provided for cooperating with holes provided on the mold  12  (not shown), etc. 
     Further characteristics and features of the robots  52  will now be described with reference to the operation of the system  10  and to  FIGS.  1 A- 1 D,  3 A- 3 D and  5   . 
     With reference first to  FIGS.  1 A and  3 A , two flexible molds  12  of dried wet-cast concrete products  14  are moved side by side face down on the conveyors  16  by one of the pusher bar  34  until the front edges  106  of the molds  12  exit the passage  49  defined by the support member  46 . 
     It is to be noted that the position of the molds  12  is indexed by the pusher bars  34 . Depending on the products  14  or on the configuration of the molds  12 , the system  10  can be operated so that the molds  12  are demolded while moving onto the conveyor  16  or while their movements are stopped. 
     According to another embodiment, the position of the molds  12  on the conveyor  16  is alternatively or complementarily indexed using sensors (not shown) or switches (not shown). 
     The pair of gripping tools  54  are then moved by the robot  52  in position to grip the molds  12  by their frontal edge. This position of the gripping tools  54  is shown in  FIGS.  1 A and  3 A . 
     While the molds  12  remain firmly gripped by the gripping tools  54 , the robot arm  52  is controlled such that the frontal edge  106  of each mold  12  is moved along a first arcuate path (see line portion  108  in  FIG.  5   ). This movement has been found to crack the front portion of the molds  12 , thereby easing the separation of the products  14  from the molds  12 . 
     With reference to  FIGS.  1 C and  3 C , the robot arm  52  is then operated so that the gripping tools  54  are pivoted rearward and then moved in a straight angled path upwardly (illustrated by line portion  110  in  FIG.  5   ). This movement causes the lifting of the molds  12  while the products  14  remain on the conveyor surface  32 . 
     As can be seen in  FIG.  5   , the change of path between paths  108  and  110  yields a first broken point  112  in the path  114 . 
     It is to be noted that a further conveyor or another mold-receiving table (not shown) is provided adjacent the conveyor  16  downstream thereof to receive the first-partly-unmolded and then fully unmolded products  14 . 
     With references to  FIGS.  1 D and  3 D , the edges  106  of the molds  12  are then moved by the robot  52  rearwardly along a third path  116 , yielding a second broken points  118  in the overall path  114 , which can then be qualified as being unsmooth since it includes at least one broken point. 
     The demolding process then continues by the molds  12  being moved by the robot arm  52  away from the conveyor  16  and the demolded products  16  being convey away from the system  10  (both not shown). 
     The path  114  of the edges  106  of the molds  12  caused by the robot  52  is adapted to the configurations of the mold  12  and products  16  therein and the robot  52  can be operated so as to yield a different path for the edges  106  than the path  114 . 
     For example, the path is not limited to be parallel the longitudinal direction and can include transversal movements. 
     It is to be noted that the path is the same for each part of the edge of a mold  12 , all parts moving in unison. 
     The method is summarized in  FIG.  6   . 
     It has been found that moving the flexible mold  12  along an unsmooth path that is adapted for the wet-cast concrete products configurations therein yields a more controlled demolding thereof and minimize both stucking of the products within the mold and damage of the products. 
     It is to be noted that connectors, cables, and other secondary or non-mechanical components of the system  10  have been omitted in the figures so as to alleviate the views. 
     It is to be noted that many modifications could be made to the method and system for demolding a flexible mold described hereinabove, for example:
         the robot  52  can be omitted and the gripping tools  54  be mounted to a track assembly (not shown) defining a path that guide there movement and orientation trough an unsmooth path as described hereinabove.       

     According to another embodiment of a method for demolding a flexible mold of wet-cast concrete products, the following step is performed prior to demolding:
         removing a vacuum on the flexible mold  12  by moving at least one portion of the peripheral edge  106  away from another portion of the flexible mold  12  that is adjacent to the at least one portion of the peripheral edge  106 .       

     This can be achieved, for example, by providing the subsystem  120  shown in  FIG.  7   . 
     The subsystem  120  comprises a pair of support members  122  that maintain the molds  12  unto the support plate  32  and a corresponding pair of mold-bending elements  124  (only one shown for each pair) that move both longitudinal edges  106  of the molds  12  away from the plate  32  while the molds  12  are maintained thereon. 
     Two independent pairs of a mold-bending element  124  with a corresponding support member  122  are provided and positioned on the conveyor  16  so as to independently and simultaneously bend both longitudinal edges  106  of the molds  12 . According to another embodiment, a single pair of mold-bending element  124  and support member  122  is provided that cracks the molds  12  by bending their longitudinal edges  106  in consecutive passes therethrough or by bending a single one of the longitudinal edges  106 , depending for example on the configuration and size of the molds  12  and/or of the products  14  therein. 
     The support member  122  is in the form of a cylindrical rod that is mounted to the conveyor  16  thereabove for pivotal movement about pivotal axis  126  via an actuating assembly  128 . The axis  126  is parallel to both the plate  32  and the edges  106  of the molds  12  that are moved face down by the conveyor  16 . 
     The mold bending elements  124  are in the form of blades that are mounted to the conveyor  16  for pivoting movement towards and away a mold-contacting position (shown in  FIG.  7   ). Each of the four blades  124  is registered with a corresponding opening  128  in the plate  32  (only two shown) and has a length comparable, but slightly smaller, thereto so as to be movable in and out thereof. The openings  128  are positioned parallel to the axis  126  and are located so as to be registered with the longitudinal edges  106  of the molds  12 , taking into account the length thereof. 
     As will now become apparent to a person skilled in the art, the actuation of the subsystem  120  causes the simultaneous i) extension of the blades  124  upwardly through the openings  128  and ii) movement of the support members  122  towards the plate  32  so as to maintain the molds  12  thereon in close contact with the plate  32 . It results from such movements that the longitudinal edges  106  of the molds  12  are moved upwardly away from the plate  32 , while portions of the molds  12  that are longitudinally adjacent to the edges  52  are maintained onto the plate  32 . This removes vacuum between the molds  12  and products  14  and therefore the adherence therebetween, thereby facilitating the removal of the products  14  during demolding. 
     The actuation of the subsystem  120  is synchronized with the passage of the molds  12  along the conveyor  16 , the position of the molds  12  being indexed by the pusher bars  34 . Depending on the products  14  or on the configuration of the molds  12 , the system  10  can be operated so that the molds  12  are cracked while moving onto the conveyor  16  or while their movements are stopped. 
     It is to be noted that many modifications could be made to the method and sub-system for cracking a flexible mold described hereinabove, for example:
         the method and system are not limited to cracking molds  12  at their longitudinal side edge; the system can be modified, including the orientation of the blades  124  and openings  128 , so that the molds  12  are cracked alternatively or complementarily at their lateral sides;   the blades  124  can be substituted with a plurality of fingers or plungers (not shown) and the elongated openings  128  can be replaced by a series of holes (not shown) in the plate  32 ;   the support members  122  can take other form or be omitted;   instead of members that pushes the edges  106  of the molds  12  upwardly, the mold-bending mechanism can be configured to move the edges  106  downwardly. For example, the mold-bending mechanism can be in the form of one or more grabbing members (not shown) that pull the edges  106  of the molds  12  downwardly while the edges  106  are positioned above an opening in the conveying surface;   the mold-bending mechanism can be adapted to bend the molds  12  while they are face up on the table;   while the support members  122  are movable between deployed and retracted positions, they can be modified so as to be fixedly mounted to the conveyor  16 .       

     Although a method and system for demolding a flexible mold of dried concrete products have been described hereinabove by way of illustrated embodiments thereof, they can be modified. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that the scope of the claims should not be limited by the preferred embodiment but should be given the broadest interpretation consistent with the description as a whole.