FR2722132A1 - DEVICE AND METHOD FOR MANUFACTURING SQUARE BLOCKS OF POLYURETHANE FOAM - Google Patents

Abstract

The invention provides a device and a method for making foam blocks, in particular polyurethane blocks using water instead of fluorinated hydrocarbon or other similar hazardous material, which are substantially square, that is to say that is, all surfaces of the block (100) are substantially flat and / or orthogonal. The device generally comprises a mold assembly having a side (14; 18), a top (24) and a bottom defining a mold cavity (22) and means for controlling the rate of expansion of the foam in the cavity. . The method generally comprises the steps of dispensing a given amount of a liquid polyurethane into the open mold cavity, at least partially closing the cavity and expanding the foam at a controlled rate, and removing the foam block. As the rate of foam expansion is controlled, the foam blocks formed are nearly square.

Description

The present invention generally relates to a device and a method for

make foam blocks

  which are substantially square, i.e. flat and orthogo-

  nals, and more particularly a mold assembly comprising

  both a means for controlling the speed of expansion of the foam present in the mold cavity and a method for manufacturing a block of polyurethane foam, by which the speed of expansion of the foam is regulated to give a

  foam block of substantially square shape.

  In the manufacture of polyurethane, in particular semi-rigid polyurethane foams such as those used for head trim and other refinishing parts of automobiles, a liquid polyurethane formula is generally poured into a mold and allowed to settle. expand or rise freely as it passes

  from the liquid state to the semi-rigid state. We generally manufacture

  These types of polyurethane foam by reacting alcohols with two or three reactive hydroxyl groups.

  per molecule, such as diols or polyols, and iso-

  cyanates that have more than one reactive isocyanate group per mo-

  lecule, such as disocyanates or piolyisocyanates. In addition, flexible foams, including semi-rigid foams, are generally manufactured by reacting a polyol with a

  disocyanate, water and an amine and a gold catalyst

  gano-tin in the presence of polymeric charges. While the prior art teaches the use of hydrocarbons

  fluorinated, such as freon, instead of water in the form

  mule above and that such substitution has had some

  very successful in the manufacture of a square block of semi-rigid polyurethane foam, water is currently preferred

  for environmental and safety reasons.

  A typical mold consists of four parts.

  kings and a bottom, with an open top, that is to say without cover. When using this type of mold, the block of foam obtained, or "roll" has a shape similar to that of a baguette having a relatively flat bottom and sides but having a curved or rounded top. The

  length and width of the polyurea foam roll

  thane will be determined by the dimensions of the mold, then

  as its height will be by the density of the poly-

  urethane and its ability to rise when the formula of polyurethane allows it to rise freely. In general, the rounded top portion of the polyurethane foam roll should be removed and the roll squared to form a block with flat and orthogonal surfaces before cutting into blanks or sheets for further processing. Therefore, there is a substantial loss of material, in the range of about 35% to 40% of the total volume of the roll

  original, when it is squared. A major by-

  tie of the loss is due to the removal of the four rear corners

  round at the top of the foam bun.

  We tried to make foam rolls with sides, a top and a bottom substantially

  squares. For example, flat floating tops that enclose

  completely cover the mold cavity and include

  tees located on the upper surface of the mold were used

  for this purpose. However, this approach has had only one success.

  These are modest and often require the use of a fluorinated hydrocarbon in the formulation of liquid polyurethane. When this formulation includes water, as is preferred,

  the corners of the bun, especially at the top

  lower, remain rounded, even with the use of a totally floating top. Similar efforts to solve this problem have been attempted by increasing the initial amount of polyurethane placed in the mold cavity, in order to

  fill the gaps between the foam and the floating top.

  However, with this approach, the upper part of the pe-

  tit bread continues to be somewhat rounded and the density

  resulting from the foam block is greater than the density

sirable about 25.6 kg / m3.

  It would therefore be desirable to have a device and a method for producing a block of polyurethane foam which has all sides substantially flat and / or orthogonal, i.e. square, and in which the formula polyurethane requires no hydrocarbons

  fluorinated but on the contrary includes water.

  To summarize, the present invention relates to a device and a method for manufacturing substantially square foam blocks, in particular blocks of

  polyurethane foam using water instead of a hy-

  fluorinated drocarbon or other similarly dangerous material-

  reux. The device and method of the present invention provide polyurethane foam blocks which are substantially square, i.e. all of the surfaces of the

  block are substantially flat and / or orthogonal. The availability

  generally includes a mold assembly having a

  side wall, top and bottom plate which define-

  feels a cavity and a means for controlling the speed of

  foam expansion in the mold cavity. The method generally includes the steps of distributing a

  given amount of liquid polyurethane in the cavity or-

  green mold, at least partially closing the cavity, and causing the foam to expand at a controlled speed and removing the foam block from the mold cavity. As the mold limits are at least partly defined and the expansion speed is regulated, blocks

  of foam are formed which are substantially square, i.e.

say flat and orthogonal.

  In a preferred embodiment of the present invention, a mold assembly includes a mold having a side wall, a top and a base defining a cavity. A background whose position can be changed is

  placed in the cavity so that the volume of the latter

  may be variable. A hydraulically actuated lifting plate assembly is coupled to the bottom and allows

  vary the volume of the mold cavity so as to

  control the speed of foam expansion during pro-

discontinued molding.

  In another preferred embodiment of the present invention, a mold assembly includes a mold having a side wall, and a bottom defining an open cavity. A floating top having part of its corners

  removed is placed in the mold cavity and closes it

  tial. The foam in the corners of the car

  can rise freely while the floating top controls the expansion of the central part of the foam block

during the molding process.

  In another preferred embodiment of the present invention, a mold assembly includes a mold having a side wall and a bottom defining an open cavity of the mold. A floating top is located in the cavity and closes it. Mold insert elements are placed on the floating top and extend at least partly in the cavity along its interior walls. It results from the presence of the added elements that the foam located at the corners of the perimeter of the cavity is drawn upward to undergo an expansion at the edges of the cavity at almost the same speed as the foam located at

  the central part of the foam block.

  The present invention will be better understood

  during the following description made in conjunction with

  attached drawings in which: Figure 1 is a perspective view of a mold assembly according to the present invention, having four side walls, a removable top which can be fixed to the assembly, a base and a bottom which can be positioned with the whole so as to vary the volume of the

  mold cavity and control foam expansion during

during the molding process;

  Figure 2 is a sectional view of the

  appears to mold of Figure 1, giving further details of a lifting plate assembly coupled to the bottom plate to removably position the bottom inside the mold cavity;

  Figure 3 shows the distribution step.

  tion and mixing of the liquid foam formula in a reduced volume of the mold cavity;

  Figure 4 shows the distribution step.

  tion of the liquid foam in the mold cavity; Figure 5 shows the step of sealing the mold cavity and controlling the expansion of the foam inside by the removable positioning of the bottom in order to vary the volume of the cavity; Figure 6 shows the step of raising the bottom and removing the foam block from the mold assembly; Figure 7 is a perspective view of a

  variant of the present invention which comprises

  carries a mold assembly having four sides, a base and a floating top, in which the corner portions of the floating top are removed to allow the corners of the

  foam block to undergo expansion in an elevation being

  tion while the central portion of the foam block undergoes expansion under the effect of the stress exerted by the floating top; and Figure 8 is a perspective view of a

  variant of the present invention which comprises

  carries a mold assembly having four sides, a base and a floating top with attached mold parts which extend at least partly into the cavity for controlling

  foam expansion during the molding process.

  The present invention provides a device

  and a method of making foam blocks, and thereby

  particularly polyurethane foam blocks which are sensitive

  squarely square. The device generally includes a

  seems to mold having a side, an upper wall and a lower wall defining a cavity and at least one of the walls being movable so as to vary the volume of the mold cavity. The expression "substantially square" is intended to indicate that the surfaces of the block comprising the top, the bottom and the sides are substantially flat

  and / or orthogonal. The polyurethane foam blocks feel

  so squarely square of the present invention require little or no cutting of the foam before any subsequent treatment of the foam block (for example, slicing the foam block to give sheets or

  sketches). The device and method of the present invention

  tion thus reduce the waste previously associated with

  the manufacture of polyurethane foam blocks for em-

  use in automotive applications.

  It is believed that a semi-rigid polyurethane formula produces an internal pressure of the order of 34.3x103 Pa while it expands from

  the liquid state to the finished semi-rigid state. The pressure

  cée is multidirectional and produces significant forces

  friction aunts on the foam at the interface between the expanding block and the surfaces of the walls of the mold cavity because of the large surface area of the sides of a traditional mold assembly. It is further believed that this results in non-uniform expansion of the foam in the cross section of the assembly. So the foam

  located in the center of the mold is able to rise more quickly

  dement because it does not undergo any force of friction. Accordingly, the object of the present invention is to provide a means for controlling the expansion of the foam in the

  cross section of the mold, either by presenting an over-

  additional face to the expanding block by increasing the volume of the mold cavity, either by allowing the foam located in the corners to rise freely while maintaining the foam in the central part of the mold, or

  by providing inserts in the mold which make

  cilitate foam expansion in the corners by reducing

tion of friction.

  As shown in Figure 1, the device of the present invention comprises a mold assembly 10 having four side walls 12, 14, 16 and 18, arranged

  on top of a base 20 so that the side walls

  rales and the base define a cavity 22 of a mold. A top 24 is disposed on the opposite side walls of

  the base 20 to enclose the cavity 22 of the mold. A char-

  horizontal channel 26 connects the side walls 12, 14 and 16 to the base 20 so that these walls are pivotally fixed around their lower edge to the base 20. A vertical hinge 28 pivotally fixes the side wall 18 to the side wall 12 to allow access to the mold cavity 22 from one end of the mold assembly

  10. A fixing flange 30 disposed on the wall 18 oppo-

  placed at the vertical hinge 28 allows this wall to be

  removably attached to a complementary mounting flange

  shutter which is disposed on the side wall 16. The wall 18 also has a transparent viewing window 19 which allows the operator to monitor the interior of the cavity

  of the mold during the molding process. While the di-

  mold dimensions are dictated by the size desired for the foam block to be produced, the present invention

  can be used to make relative foam blocks

  tively large, of the order of 2 meters long, 1.5 meters wide and one meter deep. The technician will readily admit that the present invention can be adapted to produce foam blocks of variable dimensions without

  depart from the scope of the invention.

  In the preferred embodiment, the

  mold mold 10 is made of an aluminum plate that provides adequate strength to hold polyurethane foam during the molding process while

  providing a relatively light molding tool.

  The assembly 10 further comprises a multitude of substantially identical support tie rods 32 which are arranged between the side walls 12, 14 and 16 and the base 20 so as to reinforce it and prevent its walls from curling. The tie rod 32 comprises a rod 34 having an upper end fixed to the side wall 12 at an upper attachment point 36 and a lower end fixed to the base 20 at a lower attachment point 38. The point

  36 and point 38 provide a subject connection

  ment between the rod 34 and the side walls 12, 14, 16 or the base 20. In the present embodiment, the rod 34 has a diameter of approximately 25 mm and is fixed to the side wall 12 at a point located approximately at the 3/4 of the distance between base 20 and top 24 at an angle of approximately 30 with the vertical. While the assembly 10 of the preferred embodiment currently comprises three support rods along each side wall 12, 14 and 16, the technician will notice that the dimensions and the number of necessary rods are determined by the internal loads produced during the molding process. So we can incorporate a number of

  larger or smaller tie rods as required.

  The top 24 includes support beams in the axial direction of its surface to give it a

  additional rigidity. In this embodiment

  tion, the top 24 is made of 20 mm plywood and the support beams 40 are made of a pair of 2.5 cm x 10 cm which is arranged axially on its upper part. The top 24 is removably attached to the assembly 10 by means of strips of material called nylon 42

  which extend on top 24 and engage in bou-

  eyelashes 44 arranged on the base 20. The bands 42 are of the type generally used for attaching loads during their transport, the tension of which can be adjusted and thus provide a means for removably fixing the

  top 24 to set 10 in a quick manner. The techni-

  it will be seen that the present invention can be adapted to provide alternative or additional means for fixing the top 24 to the assembly 10, including the automatic closing systems supplied pneumatically or hydraulically,

  without modifying the field of the present invention.

  Now in connection with Figure 2, the

  device of the present invention further comprises a

  seems to have a movable bottom 46 which is disposed in the cavity 22 of the mold and can be positioned to vary the volume of this cavity. The assembly 46 includes a floor 48 for

  provide a substantially flat surface at the lower end

  of the cavity 22, a secondary chassis 50 disposed at the

  below floor 48 and giving it strength and rigidity

  and a lifting plate assembly 54 which is disposed between the secondary chassis 50 and the base 20. The assembly 54 acts to control the position of the floor 48 inside the cavity 22. The movable bottom assembly 46 features in

  in addition to a sealing box 52 which is arranged on the surface

  upper face of the floor 48 to prevent the polyurea

  thane liquid does not leak from the mold cavity 22 during the molding process as will be described later with

more details.

  In the embodiment having current-

  Preferably, the lifting plate assembly 54

  takes a hydraulically actuated scissor type cylinder which

  uses a hydraulic system 56 comprising a hy-

  hydraulics 58 coupled to a scissor link mechanism 70

  to raise and lower the moving floor assembly 46. The mete

  canism 70 includes an upper rail 72 fixed to the chassis

  condaire 50, a bottom rail 74 disposed on the base 20, a drive rod 76 coupled to the hydraulic cylinder

  58 and pivotally attached to the upper rail 72 and a connecting rod

  follower lens 82 pivotally attached to the bottom rail 74.

  The driving rod 76 is an element having the general form

  rale of a U having a spacer and two arms extending from it. The spacer of the link 76 is fixed to the upper rail 72 at a pivot point 80. The link 76 further comprises a roller 78 disposed at the end of each arm opposite the pivot 80 to be in contact with the base 20 and providing a translational movement of the roller 78 along the lower rail 74. Similarly, the follower rod 82 has the general shape of a U having a spacer fixed to the lower rail 74 to a pivot 86 and a roller 84 disposed at the end of each arm opposite the

  pivot 86 to impart a translational movement to the wheel

  water 84 along the upper rail 72. The link 76 and the

  follower link 82 are also coupled by pivot

  ment to pivot 88 of the scissor link.

  The hydraulic cylinder 58 is coupled to the

  drive rod 76 so that the extension and retraction

  tion of the cylinder cause the translation of the roller 78 along the lower rail 74. The geometry of the scissor link mechanism 70 is such that the translational movement of the link 76 has the effect that the follower link 82 moves along the rail upper 72, resulting in the vertical displacement of the movable bottom assembly 46 in

  response to actuation of the hydraulic cylinder 58. The system

  hydraulic tem 56 further includes a source of pressurized hydraulic fluid, such as a pump 64 shown

  schematically in Figure 1 which provides a volu-

  metric of the hydraulic fluid at an adequate pressure for

  operate the hydraulic system 56. The hy-

  hydraulic 56 also includes a supply line 60

  in fluid to fluidly connect the pump 64 to the cy-

  Hydraulic liner 58. A pressure gauge 66 and a flow control valve 68 provide a means for monitoring and

  selectively control the actuation of the hydrau-

  lique 56, allowing the controlled positioning of the

seems 46.

  The mechanism 70 provides a compact and efficient means for positioning the floor 48 of the cavity 22

  as we wrote earlier. While the mode of realization

  sation currently having the preference describes a set

  54 with lifting plate comprising the mechanism 70 and the system

  hydraulic head 56 for variable positioning of the

  seems 46 with a movable bottom, the technician will notice that other positioning means comprising pneumatic systems or conventional systems with spring damping could be incorporated without departing from the field

of the present invention.

  Now in connection with FIGS. 3 to 6, a method will be described for molding a block substantially

  foam square according to the present invention. As shown

  felt in Figure 3, we rotate the side wall 18 to

  take an open position to facilitate access

  at the cavity 22 of the mold. The moving bottom assembly 46 is

  raised inside the cavity 22 to a first point

  elevation. The sealing box 52 is disposed on the upper surface of the floor 48 and provides a means for preventing leakage of the liquid polyurethane from the cavity 22. The interior surfaces of the side walls 12, 14, 16 and 18 can be treated with a suitable wax or release agent to facilitate removal of the foam block 100 after the molding process. A

  drum 90, which has neither top nor bottom, is generally-

  placed in the center of the box 52 and provides a re-

  product in which the individual components of the liquid polyurethane mixture can be mixed. After having

  placed the sealing box 52 and the drum 90 in the case

  part 22 of the mold, the side wall 18 is placed so

  to close the cavity 22 and the flanges 30, 31 (not shown

  tees) are engaged so as to fix the side wall 18 to the side wall 16. The various reactive components of the polyurethane formula are distributed in the drum 90 and

adequately mixed.

  After the side wall 18 has closed and the polyurethane has been completely mixed in the drum 90, the latter is raised, allowing the liquid polyurethane to

  switch from reduced volume of drum 90 to the sealing box

  density 52, as shown in FIG. 4. In this way, the liquid polyurethane can flow rapidly towards the perimeter of the box 52 and the gravity acts to distribute the liquid polyurethane in a uniform manner. While the present invention contemplates the supply of polyurethane

  liquid in the cavity 22 via the drum 90, other methods

  dice of distribution of liquid polyurethane in the cavity

  of a mold can be incorporated into the present invention.

  tion without departing from its field. For example, a mixing head placed on the end of an aerial mas can be

  used to distribute liquid polyurethane to the ma-

  niere of a coil along the outer perimeter of the

box 52.

  The viscosity of the liquid polyurethane foam can be variable so that a homogeneous liquid mixture is produced which flows easily and distributes itself within the mold cavity. In the present invention, a formula of a liquid having a relatively high viscosity is used. The viscosity for-

  should be lowered with the addition of MDI or other consti-

  similar kills so as to obtain a better homogeneous

  birth or better distribution inside the mold.

  After the distribution of the polyurethane li-

  in the sealing box 52, the top 24 is placed

  and fixed on the side walls 12, 14, 16 and 18 to close

  sea the cavity 22 of the mold, as shown in Figure 5, which prevents movement of the top 24 during expansion

  polyurethane foam. While the poly-

  liquid urethane is subjected to an expansion to take its semi-rigid state, the assembly 46 with a movable bottom is lowered at a speed proportional to the expansion of the foam, hence the control of the speed of expansion of the foam. This is achieved by providing flows from the

  hydraulic fluid in cylinder 58, causing the

  line down the scissor link mechanism 70, from where the assembly 46 is lowered inside the cavity 22. The flow of hydraulic fluid can be monitored and controlled via the pressure gauge 66 and the valve 68 flow control to maintain desired speed of expansion

foam.

  In the practice of the invention having

  so preference, the speed of movement of the whole

  seems 46 with a moving bottom is approximately equal to the vi-

  volumetric expansion of polyurethane foam

  thane in the cavity 22. In one embodiment of the

  present invention, a reasonable speed of movement-

  precise for set 46 can be obtained by maintaining

  nant a constant hydraulic pressure in the cylinder 58 which reacts against the internal forces developed in the cavity 22 by the expansion of the polyurethane foam. In

  variant, a controlled speed of the stroke can be in-

  incorporated in the present invention by calculating a speed

  predicted for volumetric expansion of poly-

  urethane in cavity 22 and programming of the hy-

  56 to provide the appropriate speed of movement

  ment for the assembly 46 with movable bottom. The speed of the volumetric expansion is not necessarily linear with respect to time or with respect to the forces exerted in the mold cavity. As the rate of foam expansion

  the interior of the mold cavity 22 is not necessary-

  linear in function of time or internal forces,

  the technician will easily notice that modes of

  which provide a non-linear control of the vi-

  movement of the assembly 46 can be incorporated

res in the present invention.

  As soon as the movable bottom assembly 46 has

  dyes the end of its downward stroke, the cavity 22 has its final volume. The polyurethane foam located in the cavity 22 can complete its expansion and its passage from the liquid state to the semi-rigid state. The block 100 of polyurethane foam can then harden sufficiently so that it can be removed from the assembly 10 without altering

tion of its final form.

* In FIG. 6, the removal of the block of foam 100 is shown, the assembly 46 with a movable bottom being raised to release the block 100 from the assembly 10. At this stage, the block of foam is substantially released from the side walls. 12, 14, 16 and 18. The flanges 30, 31 (not shown) are released and the side wall 18 moved to assume the open position so as to allow access to the cavity 22 of the mold. The polyurethane foam block is extracted

  of the cavity through the opening created when the pa-

  lateral king 18 is moved around its vertical hinge

  wedge 28, and is removed from the assembly 10.

  In connection now with Figures 7 and 8, an alternative embodiment of the present invention is shown in which the mold assembly 110 incorporates a floating top 124 which can be placed inside the cavity 122 of the mold instead of the whole 46 thoroughly

  mobile described above in the first embodiment

  tion and shown in Figures 1 to 6. The mold assembly 100 comprises side walls 112, 114, 116 and 118 and a base 120. The side walls 112, 114 and 116 are fixed to the base 120 by means of 'a horizontal hinge 126, while the side wall 118 is fixed to the side wall 112 via a vertical hinge 128. A flange 130 is disposed along the edge of the side wall 118 and is engaged in a complementary flange located on the wall lateral 116 so as to securely close the assembly 110, hence the definition of the cavity 122 of the mold. The assembly 110 comprises the floating top 124 which is dimensioned so as to be mounted inside the cavity 122 and can be animated with a vertical translational movement. A spacer

  123 is coupled to the top 124 via a suspension element

  sion, such as a chain 125, so that the spacer 123 can be disposed through the side walls 112 and 116

  to suspend the floating top 124 in the cavity 122.

  Although not illustrated in Figures 7 and 8, a

  suitable support rod can be incorporated in the

  seems 110, as described above, to confer

  adequate mold rigidity during the mold process

  age. In addition, cardboard side walls (not shown

  treated or covered with a suitable material such as an "onion skin" may be arranged in the cavity 122 along the interior surfaces of the walls 112, 114, 116 and 118 and along the base 120 and the above 124 for

  facilitate removal of the foam block 100 upon completion

of the molding process.

  As shown in FIG. 7, the floating top 124 has a part removed or notched in its periphery 132 at each of the corners, hence the formation of an opening 134 between the side walls and the top to allow the foam block 100 to rise freely in

  the corners of the cavity 122 while limiting the speed of ex-

  expansion of the central part of the block 100 with the top 124. In an embodiment given by way of example, the opening situated at each corner is generally of triangular shape and is approximately 180 mm long on each side of the

  mold. The dimensions of the openings are believed to be

  ted by the particular polyurethane formula that is used and more especially by the surface tension produced by the foam as it relaxes. So then

  that these dimensions are typical for a poly-

  given urethane, they are not intended to limit the scope of the invention. Furthermore, the invention as described includes a floating top having removed corner portions, and the technician will readily see that the

  present invention contemplates the use of other notches

  circumference of the floating top periphery to allow

free rise of the foam.

  At the start of the molding process, the top

  floating 124 is removed from the cavity 122 of the mold and from the

  liquid lyurethane is distributed in the cavity as described above. The top 124 is placed in the cavity

  122 and suspended by the spacer 123 via the chain 125.

  While the polyurethane foam relaxes from its liquid state to its being semi-rigid, it comes into contact with the suspended top 124. The additional weight of the

  above 124 acting on the foam block 100 makes it possible to

  send the foam expansion speed to the center of the pe

  tit foam bar while allowing the corner portions to rise freely, resulting in a uniform expansion of the cross section of the foam block 100. After the expansion and hardening of the foam block 100, we opens the side wall 118 and removes the block 100 from the

cavity 122.

  In connection now with FIG. 8, an alternative embodiment of the floating top 124 'further comprises a multitude of attached assemblies 140 arranged at the corners of the top 124' and extending in the cavity 122. In

  the present embodiment, of treated or coated cardboard

  green can be used to make 140 sets.

  However, other suitable materials could be

  used without departing from the scope of the present invention.

  The assembly 140 generally has the shape of a triangular prism

  straight strip and comprises an upper part 142 extending above a corner of the top 124 ′ while being in contact with

  him, a first portion of side wall 144 and a se-

  side wall portion 146 extending downward from the upper portion 142 and into the cavity 122 of the mold. The first and second portions 144, 146 are arranged between the top 124 'and a side wall of

  the mold assembly 110 to provide a mo-

  bile inside the cavity 122 which moves in conjunction with the top 124 '. In an exemplary embodiment, the first and second wall portions are rectangular, having approximately 180 mm x mm, and extending over approximately 180 mm in the

mold cavity.

  The molding process of the foam block is substantially identical to that described in the mode shown in FIG. 7. The assembly 140 with attached elements acts to reduce the frictional forces occurring at the corners of the assembly 110 by providing a surface of movable mold in the corner of the cavity while the top 124 is

  pushed up. While the present invention has been described

  tion as comprising mold inserts which

  are placed in the corners of the mold cavity, the techni-

  this will easily see that the insert could be caused to extend into the cavity along any portion of the periphery of this cavity to facilitate

foam expansion.

  The technician will now appreciate from

  the previous description that the general teachings of

  the present invention which comprises a mold assembly having means for controlling the rate of foam expansion in a mold cavity and a method for molding a block of foam by controlling the rate of foam expansion which is more particularly suitable for the manufacture of

  practically square foam blocks with a formula of

  lyurethane which includes water instead of a hydrocarbon

  fluoride bure. The present invention can be used to form foam blocks having various shapes. By

  example, the previous detailed description was made in

  more specific connection with any cross section. However, the technician will readily see that the present invention can be used to form a block of

  foam having a circular, triangular cross-section

  or other by providing side walls of an appropriate shape. Therefore, while the

  present invention in conjunction with specific examples

  liers, its true domain should not be so limited because other modifications will appear to the technician after

  the study of the drawings, the memorandum and the following claims

bragging rights.

Claims (12)

  1 - Mold assembly (10) of the type in the   which a dosed amount of a mixed foam formula is dispensed into the mold assembly and allowed to relax and   polymerize to form a foam block (100), characteristic   rised in that it comprises: a mold having a side wall (12; 14; 16; 18), a top (24) disposed at the first end of the side wall, and a base (20) disposed at the second end from the side wall opposite the top, the side wall, the base and the top defining a mold cavity (22); and   means for controlling the speed of expansion   at least part of the foam in the cavity so that a substantially constant rate of foam expansion occurs in the cavity for its polymerization.   2 - assembly according to claim 1, ca-   characterized in that the means for controlling the speed of expansion comprises a movable bottom assembly (46) having a bottom plate (48) disposed between the top (24) and the base (20) inside the mold cavity (22); and a positioning means coupled to the bottom plate for positioning it in an adjustable manner inside the cavity of the   mold and vary the volume of the cavity.   3 - assembly according to claim 2, ca-   characterized in that the positioning means comprises: a first link (76) disposed between the base and the base plate and having a first end pivotally connected to the base plate and a second end in contact with the base; a second link (82) disposed between the base and the bottom plate and having a first end pivotally connected to the base and a second end in contact with the bottom plate;   the first and second links being ac-   coupled together to cause their coordinated movement to raise and lower the bottom plate; and drive means coupled to the positioning means for causing coordinated movement of the first and second links.   4 - assembly according to claim 3, ca-   characterized in that the drive means comprises a cy- liner (58) operated by fluid.   - The assembly of claim 2, characterized in that the positioning means sets up the bottom plate (48) in a first position when the formula of the liquid foam is dispensed in the mold cavity, and in that '' it lowers the bottom plate to   a second position at a moving speed   tional to the rate of expansion of the foam formula.   6 - assembly according to claim 2, ca-   characterized in that the mold assembly further comprises a fixing means for removably fixing the plate from above to the side wall.   7 - assembly according to claim 1, ca-   characterized in that the top further comprises:   a floating top (124) having a perimeter edge   phetic (132) and arranged internally and partially closing- the mold cavity (22);   a suspension means (125) in order to   hang the floating top above the base (120) inside   inside the mold cavity (122); and   the control means comprises said edge pe-   ripherical and said side walls having an opening (134) between them to allow the free expansion of the foam.   8 - assembly according to claim 1, ca-   characterized in that the top further comprises:   a floating top (124) having a perimeter edge   spherical (132) and disposed inside the cavity (122) of the mold and completely enclosing it; hanging means (125) for hanging the floating top above the base (120) inside the mold cavity; and the control means comprises an insert element (140) of the mold disposed between a portion of the peripheral edge and a portion of the side wall, the insert element being disposed at least partially inside the mold cavity.   9 - assembly according to claim 8, ca-   characterized in that the side wall forms a corner and   the insert of the mold is arranged in said corner.   - Method for molding a block of foam (100) in a mold assembly (10) having a cavity (22), characterized in that it comprises the steps consisting in: dispensing a metered quantity of a foam formula liquid in the mold cavity; close the mold cavity; controlling the speed of expansion of the foam during its polymerization and its expansion so that a substantially constant speed of expansion of the foam occurs throughout the mold cavity; and remove the foam block from the assembly to   mold after the foam block has been sufficiently poly-   merited to allow manipulation of the block without deformation tion.   11 - Process according to claim 10, ca-   characterized in that the step of controlling the speed of ex-   foam expansion includes adjustable increase in   volume of the mold cavity in proportion to the vi- foam expansion size.   12 - Process according to claim 10, ca-   characterized in that the step of ordering the vi-   foam expansion size includes expanding a first portion of the foam in the free elevated state, and limiting expansion of a second portion of the foam, thereby equalizing of the speed of expansion of   first and second portions of the foam.   13 - Process according to claim 10, ca-   characterized in that the step of controlling the speed of ex-   foam expansion includes providing a surface of   movable wall in the mold cavity.   14 - Process according to claim 10, ca-   characterized in that the step of dispensing a metered amount of a liquid foam formula comprises: providing a mixing container (90) in the mold cavity for mixing the liquid foam formula that it contains; distributing the constituents of the liquid foam in the mixing container and mixing said constituents in the formula of the liquid foam; rapid dispensing of the liquid foam formula from the mixing container for   enter the mold cavity (22).