Abstract:
A process and apparatus is provided for automatically and continuously producing a mass of moldings. A continuous molding is manufactured by injecting a solid solution in order of precedence into a plurality of molds circulating in a line along an endless track and by solidifying the injected solution. The solution is preferably vinyl chloride resin or another synthetic resin. After the solution solidifies the mold is automatically removed from the molding. The continuous molding consists of a number of moldings open at the bottoms and connected end to end by a top plate, molded at the same time.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a process and apparatus for continuously manufacturing a molding having a number of spaces closed at the top and open at the bottom. 
     2. Description of the Related Art 
     Conventional processes and apparatus for manufacturing honeycomb moldings which are open at the top include general injection molding processes and apparatus. The operation of processes and apparatus of this type is well known, simple, and follows a set procedure. These processes and apparatus make it possible to manufacture moldings reliably. 
     In some circumstances, there may be a need to manufacture large quantities of moldings relatively inexpensively in a very short period. In other words, the quantity, the delivery deadline, or the costs may take priority over the accuracy of the molding shape and size. In this case, it is difficult to manufacture moldings by the conventional processes and apparatus, and it is, therefore, necessary to consider the use of a mass production system for producing the moldings. 
     By way of example, a molding of the type which needs to be produced relatively cheaply in a very short period of time is a lawn protector. Lawn protectors have been receiving attention for some time. Lawn protectors are laid on a lawn parking lot. Cars can be parked on the protectors so that their tires do not press on the lawn directly. This protects the lawn and does not prevent it from growing. FIG. 2 of the accompanying drawings shows part of a honeycomb molding A, which is a lawn protector. 
     The need to manufacture a mass of such honeycomb moldings at high speed takes priority over the need to improve the accuracy of their shape and size. It is difficult to manufacture such moldings at high speed with the conventional injection molding systems. In order for a process or an apparatus to manufacture honeycomb moldings at high speed, it is necessary to introduce a continuous manufacturing system, which may be an extrusion molding system, in place of a conventional injection system. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a process and an apparatus for automatically and continuously producing a mass of moldings without the disadvantages arising in the establishment of a mass production system using the conventional apparatus of injection molding systems. This is accomplished through a continuous manufacturing system using a solid solution extrusion system having a circulation system with molds. 
     In accordance with an aspect of the invention, a process is provided for manufacturing a continuous molding by injecting a solid solution in order of precedence into a plurality of molds circulating in a line along an endless track, and by solidifying the injected solution. The track includes a forward path and a backward path. The backward path extends substantially horizontally or slopes down under the forward path. The front end of the forward path is positioned just under the front end of the backward path. The rear end of the forward path is positioned just under the rear end of the backward path. The continuous molding consists of a number of moldings connected end to end by a molded top plate. The moldings are open at their bottoms. The process comprises the steps of: 
     injecting the solution into each of the molds moving along the forward path; 
     removing the continuous molding from each of the molds by displacing the mold down, little by little in order of precedence from the molding in close contact with the mold while the injected solution is solidifying; 
     moving from the front end of the forward path down to the front end of the backward path, the mold released from the removing step; 
     returning the mold along the backward path; and 
     lifting the mold from the rear end of the backward path to the rear end of the forward path. 
     By injecting a solid solution from an extrusion type injector into the molds in order of precedence, this process can continuously manufacture a continuous molding consisting of a number of moldings open at the bottoms and connected end to end by a top plate, molded at the same time. As a result, it is possible to realize a mass production system, which can greatly lower the molding production costs. 
     In accordance with another aspect of the invention, an apparatus is provided for manufacturing a continuous molding continuously by injecting a solid solution in order of precedence into a plurality of molds circulating in a line along an endless track, and by solidifying the injected solution. Each of the molds includes a plurality of pins which can protrude up into cavities in the mold. The continuous molding consists of a number of moldings connected end to end by a molded top plate. The moldings are open at the bottoms. The apparatus includes: 
     conveying means for horizontally conveying the molds in close contact and in series along the track; 
     injecting means for injecting the solution into each of the molds moving forward along the track, the injecting means being positioned above the starting point where the conveying means starts conveying the molds; 
     a pressurizer for pressing the upper surface of the injected solution with a predetermined pressure to make the surface continuously flat, the pressurizer being positioned adjacently to and downstream from the injecting means; 
     guide means for guiding the molds gradually down by using the conveying force; 
     removing means for protruding the pins up as the molds are moving down; and 
     circulating means for circulating to the starting point the molds removed from the molding. 
     This apparatus can implement the foregoing process securely. The apparatus includes molds of the same shape. By circulating the molds, the apparatus can make a molding continuously. This makes the molding production costs relatively low. While the guide means is moving each of the molds gradually down, the pins protrude up into the cavities in the mold to remove the molding already cooled and solidified in the mold. This makes the removal secure. 
     It is preferable that each of the molds include guide rollers which can be guided by the guide means in such a manner that, while the mold is moving forward along the guide means and gradually down out of close contact with the molding, the mold is kept horizontal. This enables the locus of the mold moving during the removing step to be limited to the horizontal (direction) by the synthesis of the substantially horizontal movement and vertical movement of the mold. The position of the mold can, therefore, be kept always horizontal, although it tends to tilt. 
     If a mold tilted when the injected solution in it has not completely solidified, the upper surface of the solution might start solidifying while it is not horizontal. This makes the molding bad in shape. If an inclined mold were removed down from the molding, the mold surfaces sliding on the adjacent molds would not be vertical. This prevents the removal from being smooth. It is very easy to solve these problems by keeping the molds individually horizontal while the molds are removed from the molding. 
     It is preferable that the apparatus further include means for urging forward and backward into close contact at least two of the molds moving during a period of a molding step in which the molds move forward while the solution is injected into the molds. 
     When the solution is injected into each of the molds during the period of the molding step, the injection pressure might otherwise separate adjacent molds. This defines gaps between the molds, through which the solution may leak out. By limiting the period during which the solution is injected, and by urging the molds forward and backward into close contact, it is possible to keep the solution from leaking out through the gaps. It is therefore possible to inject the solution safely and securely. 
     It is preferable that the apparatus further include means for urging forward the rear end of the mold having circulated and returned to the starting point, and for urging backward the front end of the mold at the end of the forward mold movement. This urging means brings all the molds in the molding step into close contact. This makes it possible to keep the apparatus operating without preventing the molds from moving down smoothly from the molding, and from returning smoothly to the starting point of the production. 
     Each of the molds may include a formwork, an intermediate plate and a movable plate. The formwork has the cavities corresponding to the molding. The intermediate plate closes the lower side of the formwork and has pin holes. Each of the pins extends through one of the holes in such a manner that the pins can protrude from the holes into the cavities. The pins are embedded in the movable plate in such a manner that they extend toward the intermediate plate. The movable plate can move toward and away from the intermediate plate within a predetermined range. Otherwise, the formwork and the intermediate plate might be integral. In this case, the molds are simple in structure. The movable plate can move toward and away from the intermediate plate within the predetermined range. The pins can protrude into the cavities. It is therefore easy to handle the molds and take the molding off them. 
     Each of the molds may include inner rollers supported on both sides of a front portion thereof and outer rollers supported on both sides of a rear portion thereof. The apparatus may further include inner and outer guide rails for guiding the inner and outer rollers, respectively, to keep the molds horizontal and move the molds forward and gradually down. The apparatus may also include a rail and a holding roller for stopping the movable plate from moving down. One of the rail and the roller is supported by the lower side of the movable plate or along and below the guide rails. The other of the rail and the roller is supported along and below the guide rails or by the lower side of the movable plate. 
     While each of the molds is moved forward with its movable plate stopped from moving down by the cooperation of the holding roller and the rail, the formwork and the intermediate plate move down at the same time along the guide rails. This protrudes the pins gradually into the cavities, taking the molding off the mold. 
     The apparatus may further include: 
     a first lift for moving up and down at the end point of the forward path to move down each of the molds; 
     guide tracks extending in parallel to the forward path horizontally from the point where the first lift has moved the mold down, so that the guide rollers can roll on the guide tracks; 
     a belt conveyor extending along the guide tracks for conveying the molds; and 
     a second lift for lifting each of the molds from the end points of the guide tracks to the starting point of the forward path. 
     The mold conveyed to the end point of the forward path can be moved down by the first lift, then conveyed backward along the horizontal guide tracks by the belt conveyor, and thereafter returned securely to the starting point of the forward path by the second lift. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming 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 drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a schematic side view of an apparatus for manufacturing a molding continuously in accordance with a first embodiment of the invention; 
     FIG. 2 is a perspective view of a honeycomb molding which can be made by the apparatus shown in FIG. 1; 
     FIG.  3 ( a ) is a sectional view taken on the line III—III of FIG. 1; 
     FIG.  3 ( b ) is a sectional view taken on the line I—I of FIG.  3 ( a ); 
     FIG. 4 is a sectional view taken on the line IV—IV of FIG. 1; 
     FIG. 5 is a schematic side view of an apparatus for manufacturing a molding continuously in accordance with a second embodiment of the invention; 
     FIG. 6 is a perspective view of a honeycomb molding which can be made by the apparatus shown in FIG. 5; 
     FIG.  7 ( a ) is a sectional view taken on the line VII—VII of FIG. 5; 
     FIG.  7 ( b ) is a sectional view taken on the line II—II of FIG.  7 ( a ); and 
     FIG. 8 is a sectional view taken on the line VIII—VIII of FIG.  5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 2, a honeycomb molding A is shown. The molding A has a honeycomb array of hexagonal tubes or spaces each defined by side walls A 2 . The spaces are closed at their tops by a ceiling or top plate A 1  and open at their bottoms. 
     Referring now to FIG. 1, an apparatus for continuously manufacturing the honeycomb molding A of FIG. 2 is shown. The apparatus includes an array of molds  1  shaped for the molding A and open at their tops. Each mold  1  may be 200 mm wide between its front and rear ends and 1,000 mm long. Each mold  1  has a pair of racks  1   a  formed on both sides of its bottom. Each mold  1  supports a pair of outer side rollers  1   b  on both sides of its front portion and a pair of inner side rollers  1   c  on both sides of its rear portion. The rollers  1   b  and  1   c  are positioned at the same level. The outer rollers  1   b  are offset axially from the inner rollers  1   c.    
     The molds  1  can be circulated along an endless track  2  with their open sides up by various means in the track. The track  2  consists of a forward path  2   a,  a downward path  2   b,  a backward path  2   c  and an upward path  2   d.  An extrusion type solid solution injector  3  is positioned in an upstream portion of the forward path  2   a.  The injector  3  can extrude and inject a solid solution as the material for a molding A into the mold  1  moving under the injector. The solution is a fluid or otherwise flowable and may be vinyl chloride resin solution or another synthetic resin solution. A pressurizer  4  is positioned immediately downstream from (in front of) the injector  3 . The pressurizer  4  can evenly and downward pressurize the solid solution in each mold  1  before the solution starts solidifying. The pressurizer  4  includes a pressure roller  4   a.    
     A rear booster  5   a  includes a motor  7   a  and a pair of gears  6   a,  which can be driven by the motor  7   a.  A front booster  5   b  includes a motor  7   b  and a pair of gears  6   b,  which can be driven by the motor  7   b.  The gears  6   a  are spaced from the gears  6   b  by a distance nearly equaling the total length of about four molds  1 . The gears  6   a  and  6   b  can mesh with the mold racks  1   a.  The rear motor  7   a  is greater in torque or higher in rotational speed than the front motor  7   b.  The difference in output or conveying speed between the motors  7   a  and  7   b  can apply pressing force which urges toward each other the molds  1  being driven by the boosters  5   a  and  5   b  and the molds between them. 
     The forward path  2   a  includes a pair of outer guide rails  8   b  and a pair of inner guide rails  8   c.  The rails  8   b,  and  8   c  extend in parallel on both sides of the path  2   a,  and can guide the side rollers  1   b  and  1   c,  respectively. While each mold  1  is moving along the forward path  2   a,  its rollers  1   b  and  1   c  are kept at the same level by the rails  8   b  and  8   c,  respectively, so that the mold is kept horizontal. The molds  1  can move down from the forward path  2   a  through the downward path  2   b  to the backward path  2   c, through which they can move backward. The backward path  2   c  takes the form of a tunnel or trunk, and slopes slightly down to its rear. The molds  1  can be moved backward by their own weight through the path  2   c.  It is therefore not necessary to provide a special means of moving the molds  1  backward. This contributes to the saving of power. 
     A cylinder  11  is positioned on the inlet side of the forward path  2   a.  The cylinder  11  can forward push the mold  1  which has moved up through the upward path  2   d  and reached the rear end of the forward path  2   a.  A cylinder  12  is positioned on the outlet side of the forward path  2   a.  The cylinder  12  can backward push the mold  1  at the front end of the forward path  2   a.  The cylinders  11  and  12  can push the molds  1  in the forward path  2   a  in the opposite directions. 
     A cylinder  9  stands under the downward path  2   b,  and can vertically move a table or plate  9   a,  which receives the mold  1  at the front end of the forward path  2   a.  Cylinder  9  can move the mold  1  on the table  9   a  down to the inlet of the backward path  2   c. A cylinder  13  is positioned on the inlet side of the backward path  2   c.  Cylinder  13  can push into the inlet of the backward path  2   c  the mold  1  moved down through the downward path  2   b  by the cylinder  9 . 
     A cylinder  10  stands under the upward path  2   d,  and can vertically move a table or plate  10   a,  which receives the mold  1  at the outlet of the backward path  2   c.  Cylinder  10  can move the mold  1  on the table  10   a  up to the rear end of the forward path  2   a.    
     As shown in FIGS. 3 and 4, each mold  1  includes an array of hexagonal blocks  1 - 1   a,  a front row and a rear row of semi-hexagonal blocks  1 - 1   b,  and a pair of side blocks  1 - 1   c  which support the side rollers  1   b  and  1   c.  The mold  1  also includes an intermediate plate  1 - 2  and a bottom plate  1 - 3 . The blocks  1 - 1   a ,  1 - 1   b  and  1 - 1   c  are bolted to the top of the intermediate plate  1 - 2 ,  2 , and arranged at regular intervals in the form of a honeycomb. The intermediate plate  1 - 2  functions as a guide for releasing or removing the molding. The bottom plate  1 - 3  is positioned under the intermediate plate  1 - 2 , and can move up and down relative to it. 
     Limit bolts  14  are fixed to the intermediate plate  1 - 2  and extend through the bottom plate  1 - 3 . Each bolt  14  has a head  14   a  for limiting the range within which the space W between the plates  1 - 2  and  1 - 3  can be changed. Each bolt  14  is surrounded by a compression coil spring  15 , which is interposed between the plates  1 - 2  and  1 - 3  to urge them away from each other. The intermediate plate  1 - 2  has pin holes  17  formed through it. Each hole  17  is aligned with the space formed among adjacent three of the blocks  1 - 1   a,    1 - 1   b  and  1 - 1   c.  Pins  16  each have a head embedded in the bottom plate  1 - 3 , and each extend through one of the holes  17 . 
     Normally, as shown in FIGS.  3 ( a ) and  4 , the tops of the pins  16  are flush with the top of the intermediate plate  1 - 2 . When the intermediate plate  1 - 2  moves down toward the bottom plate  1 - 3 , the top of each pin  16  protrudes from the associated hole  17  into the space among the associated three of the mold blocks  1 - 1   a,    1 - 1   b, and  1 - 1   c.  The protruding pins  16  hold side walls A 2  of the molding A while the blocks  1 - 1   a,    1 - 1   b  and  1 - 1   c  and the intermediate plate  1 - 2  are moving down. This does not damage the molding A even if the pins  16  push it with great force, because its side walls A 2  are strong. 
     When each mold  1  has moved to a position near the front end of the forward path  2   a  and is positioned quite low, the lower side of its bottom plate  1 - 3  comes into contact with holding rollers  18 . Further downward movement of the mold  1  protrudes the tops of the pins  16  from the intermediate plate  1 - 2 , taking out the molding A. The rollers  18  are supported at the top of the backward path  2   c,  but might be supported in another place. 
     In operation, the molds  1  circulate along the track  2 . The injector  3  injects a solid solution into the mold  1  moving under it. Subsequently, the pressure roller  4   a  evenly pressurizes the solution which has not started solidifying yet in the mold  1 . The pressure of this roller  4   a  is such that the honeycomb moldings formed in the molds  1  are connected by a ceiling A 1  in the form of a belt which is as thin as possible. The pressurizer  4  includes an adjusting wheel for arbitrarily adjusting the thickness of the ceiling A 1 . 
     The boosters  5   a  and  5   b  urge the mold  1  in engagement with the gears  6   a  and the mold  1  in engagement with the gears  6   b  toward each other. This brings these two molds  1  and the molds between them into close contact, preventing the synthetic resin solution from being leaked between the molds by the injection pressure. 
     The pressurized solution in each mold  1  is cooled and solidifies to form part of a molding A. The mold  1  is removed from the molding A. The guide rails  8   b  and  8   c  keep the mold  1  horizontal. The rails  8   b  and  8   c  limit the vertical movement of the blocks  1 - 1   a,    1 - 1   b  and  1 - 1   c  and the intermediate plate  1 - 2  of the mold  1  Therefore, when the mold  1  moves down, the holding rollers  18  hold its bottom plate  1 - 3  against the force of the springs  15 . This narrows the space W between the plates  1 - 1  and  1 - 3 . 
     The mold  1  can be removed down from the molding A by: 
     the bottom plate  1 - 3  being able to move up and down relative to the intermediate plate  1 - 2 ; 
     the springs  15  operating between the intermediate plate  1 - 2  and the bottom plate  1 - 3  when the bottom plate moves up and down; 
     the pins  16  protruding and retracting when the bottom plate  1 - 3  moves up and down; and 
     the holding rollers  18  coming into contact with the bottom plate  1 - 3  near the end of the removing step. 
     The front ends of the guide rails  8   b  and  8   c  are positioned immediately backward from the point where the removing step ends. Where the ends of the rails  8   b  and  8   c  are positioned, the bottom plate  1 - 3  of the mold  1  disengages from the front holding rollers  18 . When the mold  1  approaches the end of the removing step, a signal is generated. In accordance with the signal, the cylinder  9  moves the table  9   a  up. Then, the mold  1  is transferred securely onto the table  9   a,  and moved with it down to the level of the inlet of the backward path  2   c.  Thereafter, the cylinder  13  forces the mold  1  into the inlet of this path  2   c.  Then, the mold  1  is moved backward by its weight through the backward path  2   c.  When the mold  1  reaches the bottom of the upward path  2   d,  it is received securely by the table  10   a.  The mold  1  on the table  10   a  is lifted to the level of the inlet of the forward path  2   a  by the cylinder  10 . 
     As stated above, the cylinder  11  can forward urge the mold  1  at the rear end of the forward path  2   a,  while the cylinder  12  can backward urge the mold  1  at the front end of this path  2   a.  While these two molds  1  and the molds between them are moving along the path  2   a,  the cylinders  11  and  12  bring all these molds into close contact. This can keep the apparatus operating without preventing the smooth movement of the molds  1  entering and leaving the forward path  2   a.    
     The material for the molding A may contain vinyl chloride, polyethylene or another high molecular compound, and be made into solid solution at a temperature between 120 and 70 degrees C. 
     Referring now to FIG. 6, a honeycomb molding A′ is shown. The molding A′ differs from the molding A in that the walls A 2  of its hexagonal spaces each have a U-shaped top recess A 3 . The recesses A 3  of the walls A 2  do not prevent the lawn roots in a lawn parking lot from extending horizontally. 
     Referring now to FIGS. 5,  7   a,    7   b  and  8 , these figures show an apparatus for continuously manufacturing the honeycomb molding A′ of FIG.  6 . The main differences between the this embodiment and the prior embodiment of the invention are discussed below. Otherwise, the embodiments are common in structure and their operations are basically common. 
     The molds  1 ′ of this apparatus are shaped to form the recesses A 3  in the molding A′. Each mold  1 ′ has two pairs of bottom rollers  18 ′ supported by the lower side of its bottom plate  1 - 3 . Each pair of rollers  18 ′ is spaced laterally from the other. Two horizontal rails  19  extend in parallel below the guide rails  8   a  and  8   b,  and are fixed to frames  20 . Each pair of rollers  18 ′ can roll on one of the horizontal rails  19 . The rollers  18 ′ are positioned midway between the front and rear ends of the mold  1 ′ so that the mold can move down smoothly in the downward path  2   b  of the endless track  2  without sliding on adjacent parts when the rollers  18 ′ disengage from the horizontal rails  19 . The bottom plate  1 - 3  is not urged by springs away from the intermediate plate  1 - 2 . 
     The backward path  2   c  of the track  2  includes horizontal guide rails  21  extending in parallel. The side rollers  1   b  and  1   c  of the molds  1 ′ can roll on these rails  21 . A belt conveyor  22  extends below and along the rails  21 , and includes a belt  22   a.  The upper portion of the belt  22   a  can engage with the lateral middle of the lower side of the bottom plate  1 - 3  of each mold  1 ′. The belt  22   a  conveys the mold  1 ′ to the bottom of the upward path  2   d  of the track  2 . 
     Each mold  1 ′ has a pair of bearing rollers  23  supported on both sides of its bottom plate  1 - 3 . As shown in FIG. 5, two inclined guides  24  are fixed at the bottom of the downward path  2   b  and near the inlet of the backward path  2   c.  Each guide  24  has a slope for guiding one of the bearing rollers  23  along it. The guide slopes can force the bottom plate  1 - 3  down from the intermediate plate  1 - 2  in order to space them from each other. This enables the belt conveyor  22  to convey the mold  1 ′ securely. Two other inclined guides  25  are fixed at the top of the upward path  2   d  and near the inlet of the forward path  2   a.  When each mold  1 ′ is lifted by the cylinder  10 , its bottom plate  1 - 3  is moved toward the intermediate plate  1 - 2 . When the lifted mold  1 ′ is moved forward, the guides  25  guide its bearing rollers  23  to space the bottom plate  1 - 3  down from the intermediate plate  1 - 2 . 
     Referring now to FIG. 5, during operation the injector  3  injects a synthetic resin solution into the mold  1 ′ moving under it. The pressure roller  4   a  of the pressurizer  4  subsequently evenly pressurizes the solution which has not started solidifying yet in the mold  1 ′. The honeycomb moldings formed in the molds  1 ′ are connected by a ceiling A 1  in the form of a belt to form a continuous molding A′. 
     The boosters  5   a  and  5   b  urge the mold  1  in engagement with the gears  6   a  and the mold  1  in engagement with the gears  6   b  toward each other. This brings these two molds  1  and the molds between them into close contact, preventing the synthetic resin solution from being leaked between the molds by the injection pressure. While each mold  1 ′ is thus conveyed forward (to the left in FIG.  5 ), the solution in it is solidified by cooling. Subsequently, the mold  1 ′ is removed from the molding A′. 
     As stated above, the horizontal rails  19  extend forward from a point near the middle of the length of the forward path  2   a. While the mold  1 ′ is conveyed along the sloping portions of the guide rails  8   b  and  8   c,  its bottom rollers  18 ′ come into contact with the horizontal rails  19  so that its bottom plate  1 - 3  stops moving down. In the meantime, the mold blocks  1 - 1   a,    1 - 1   b  and  1 - 1   c  and the intermediate plate  1 - 2  of the mold  1 ′ keep moving down. This moves the intermediate plate  1 - 2  toward the bottom plate  1 - 3  to protrude the pins  16  from the intermediate plate. The protruding pins  16  push side walls A 2  of the molding A′ upward to take the molding off the mold  1 ′. In other words, while the molding A′ is moving forward and horizontally without changing its vertical position, the mold  1 ′ is removed down from the molding. 
     After the bottom rollers  18 ′ of the mold  1 ′ leave the horizontal rails  19 , the mold moves down along the downward path  2   b.  While the mold  1 ′ is moving down, it is kept substantially horizontal by the rollers  18 ′. After the side rollers  1   b  and  1   c  of the mold  1 ′ reach the horizontal guide rails  21 , its bearing rollers  23  are guided by the inclined guides  24 . This spaces the bottom plate  1 - 3  of the mold  1 ′ down from the intermediate plate  1 - 2  to bring the bottom plate into engagement with the conveyor belt  22   a.  The belt conveyor  22  conveys the mold  1 ′ along the backward path  2   c.    
     After the mold  1 ′ reaches the upward path  2   d,  it is lifted along this path by the cylinder  10  and returns to the starting point of the forward path  2   a.  When the mold  1 ′ is pushed into the forward path  2   a  by the cylinder  11 , the inclined guides  25  guide the bearing rollers  23  to force the bottom plate  1 - 3  downward from the intermediate plate  1 - 2 . This returns the mold  1 ′ to its original condition. The foregoing operation is repeated with the molds  1 ′ circulated along the track  2  to form a continuous molding A′. 
     The mold blocks  1 - 1   a,    1 - 1   b  and  1 - 1   c  of each mold  1  or  1 ′might be integral with the intermediate plate  1 - 2  of the mold. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.