CA1102066A - Method and apparatus for molding expanded plastic material articles - Google Patents
Method and apparatus for molding expanded plastic material articlesInfo
- Publication number
- CA1102066A CA1102066A CA265,052A CA265052A CA1102066A CA 1102066 A CA1102066 A CA 1102066A CA 265052 A CA265052 A CA 265052A CA 1102066 A CA1102066 A CA 1102066A
- Authority
- CA
- Canada
- Prior art keywords
- mold
- article
- preform
- beads
- cavity
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/36—Feeding the material to be shaped
- B29C44/38—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length
- B29C44/44—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length in solid form
- B29C44/445—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length in solid form in the form of expandable granules, particles or beads
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3415—Heating or cooling
- B29C44/3426—Heating by introducing steam in the mould
Landscapes
- Molding Of Porous Articles (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
According to the invention a method for forming shaped articles from pre-expanded thermoplastic beads, in two cycles, comprises a first cycle which includes the stages of introducing said beads into a mold cavity of a first mold to fill said mold cavity, wherein said first mold comprises two members, a male member and a female member, and wherein said first mold is maintained at a substantially constant elevated temperature throughout said two cycles, injecting steam into said first mold to cause the beads to expand, partially melt, agglomerate and form a shaped cellular preform, disengaging said two members of the first mold whereby said preform is retained by one mold member of said first mold, and a second cycle which includes the stages of transferring said shaped cellular preform at substant-ially ambient pressure, from the first mold to a second mold, by conveying said preform on said first mold member which retains said preform to said second mold, whereby the shaped preform is free to expand under the conditions of the stage of transferring, wherein said second mold is at a second substantially constant temperature throughout said two cycles, wherein said second substantially constant temperature is lower than said substant-ially constant elevated temperature and wherein the cavity of said second mold has the shape of the ultimate shaped article, cooling and compressing said shaped cellular preform in said second mold, and removing the finished article from said second mold. The method and apparatus are expecially adapted for high production rate of any thermoplastic material articles such as shock absorbing pads for packaging.
According to the invention a method for forming shaped articles from pre-expanded thermoplastic beads, in two cycles, comprises a first cycle which includes the stages of introducing said beads into a mold cavity of a first mold to fill said mold cavity, wherein said first mold comprises two members, a male member and a female member, and wherein said first mold is maintained at a substantially constant elevated temperature throughout said two cycles, injecting steam into said first mold to cause the beads to expand, partially melt, agglomerate and form a shaped cellular preform, disengaging said two members of the first mold whereby said preform is retained by one mold member of said first mold, and a second cycle which includes the stages of transferring said shaped cellular preform at substant-ially ambient pressure, from the first mold to a second mold, by conveying said preform on said first mold member which retains said preform to said second mold, whereby the shaped preform is free to expand under the conditions of the stage of transferring, wherein said second mold is at a second substantially constant temperature throughout said two cycles, wherein said second substantially constant temperature is lower than said substant-ially constant elevated temperature and wherein the cavity of said second mold has the shape of the ultimate shaped article, cooling and compressing said shaped cellular preform in said second mold, and removing the finished article from said second mold. The method and apparatus are expecially adapted for high production rate of any thermoplastic material articles such as shock absorbing pads for packaging.
Description
0f~6 BACKGROUND OF 'I`~IE INVENTION
Eield of the in ention The present invention relates to a molding method and apparatus for molding articles of expanded plastic material.
Molding methods for articles of expanded thermoplastic material have been known heretofore and especially methods for manufacturing articles obtained by agglomerating pre-expanded polystyrene beads.
- Presently these methods are commonly used for manu-facturing blocks, supports or shells for packaging food products, machinery or household electrical appliances etc... . They have excellent impact resistance, they are weatherresistant and their cost is relatively low.
Description of the prior art Usually, the known molding techniques include the following steps;
- filling a molding cavity of a mold with pre-expanded polystyrene beads - injecting steam for heating said beads to the softening temperature of the polymer and above the boiling point of the porogeneous fluid which is contained in said beads. Said steam causes, the beads to expand and bring them to a partially molded state causing them to agglomerate into a homogeneous cellular mass.
- cooling the product obtained in a cellular state contained in the mold in order to prevent a second expansion or a distortion of the molded article; and, once the mold is cooled - withdrawing the molded article from the mold, after which the mold can be heated again for the next molding cycle.
This method involves the use of considerable heating system and means for rapidly cooling the mold in order that the two alternate steps, i.e. heating the mold and cooling thereof, - 1 - ~
'~;
do not increase excessively the manufacturing of the article.
l3Owever, since the article is made from an excellent heat insulating material, this method results in a very limited production rate, and reduces drastically the efficiency and the profitability of the molding equipment.
Another disadvantage which effects this method is the consumption of energy. For example, for a medium size article when heating 0.150 kg of thermoplastic material contained in the mold it is also necessary to heat, at each molding cycle, the 150 kg of the mold material itself. It can be realized that this mass ratio of about 1 to 1000 brings in a considerab]e loss of energy which heavily affects the cost of the finished product.
In order to reduce the manufacturing cost it has been proposed to provide molds with multiple molding cavities. This approach is valid for small size articles only and on the other `!
hand the design and the manufacturing of the molds which have to be machined accurately, from a good heat conducting material, such as aluminum, are very expensive.
Also the expenses for unavoidable servicing and maintenance of so complex an equipment have to be taken into - consideration. In order to carry out successive cooling operations, the mold is provided with internal passages which allow the cooling water to circulate. If this water is not treated, calcar deposits thereof will block the injection nozzles and attack the walls of the mold or of its auxiliary equipment. Further, for economical reasons, the factories that are using the known method, use cooling systems which operate in close circuit and consequently ll~ZC~66 include storage containers, tanks for water treatment, water cooling towers and pumping stations which considerably affect the production cost of the molded articles of expanded polystyrerle produced in mass production.
The present invention provides a method and apparatus overcoming the above mentioned disadvantages.
According to the present invention there is provided a method for forming shaped articles from pre-expanded thermo-plastic beads, in two cycles, comprising a first cycle which includes the stages of introducing said beads into a mold cavity of a first mold to fill said mold cavity, wherein said first mold comprises two members, a male member and a female member, and wherein said first mold is maintained at a substantially constant elevated temperature throughout said two cycles, inject-ing steam into said first mold to cause the beads to expand, partially melt, agglomerate and form a shaped cellular preform, disengaging said two members of the first mold whereby said pre-form is retained by one mold member of said first mold, and a second cycle which includes the stages of transferring said shaped cellular preform at substantially ambient pressure, from the first mold to a second mold, by conveying said preform on said first mold member which retains said preform to said second mold, whereby the shaped preform is free to expand under the conditions of the stage of transferring, wherein said second mold is at a second substantially constant temperature throughout said two cycles, wherein said second substantially constant temperature is lower than said substantially constant elevated temperature and wherein the cavity of said second mold has the shape of the ultimate shaped article, cooling and compressing said shaped cellular preform in said second mold, and removing the finished article from said second mold.
The apparatus of the invention includes a first mold comprising male and female members defining a molding cavity having at least approximately the shape and size of the article to be produced; means for maintaining this mold at a constant temperature between 90C and 130C, and preferably about 120C;
an injection device for introducing beads of thermoplastic material into the molding cavity; one or more injection nozzles for injecting steam into the molding cavity; a mechanical or pneumatic device for ejecting the preformed article on one said member from the heated mold; means for transferring said article , on the one member and introducing the article into a second mold comprising a molding cavity having the exact shape and size of the article to be produced, this mold being maintained at a temperature lower than that of the first heated mold; and mechanical or pneumatic means to withdraw the article from said mold.
The method of the invention has many advantages over the prior art since it enables the production time to be reduced, the production cost to be reduced and, considerably simplifies the installation lay-out to increase its efficiency and profitability; in addition, with the method of the present invention, lower density materials can be obtained hence permitting material savings.
According to a preferred embodiment of the present invention, the article formed or premolded inside the heated mold is withdrawn as soon as the first molding step is completed for . - 4 -. ~ ., llC;~6:?66 being transferred in the cold mold. From this very moment, a new article can be injected in the heated mold thus permitting to reduce considerably the total molding cycle time, this time being reduced to about 10 seconds/article, for medium sized items.
The mold being no longer subject to the stresses due to the repeated and substantial temperature variations, can be constructed from any material including metals, synthetic materials or even wood. The construction of the mold is only limited by well known design and techniques of the injection or compression molds. The mold design is simplified in that the passages for circulating cooling water into the mold which are necessary with the conventional methods and apparatuses are eliminated in the apparatus of the invention or are at least of a much simplified structure.
Brief Description of the Drawings The objects and advantages of the present invention will become apparent upon reading the following detailed description of a preferred embodiment and alternatives and upon reference to the drawings in which:
Figure 1 is a schematic view of-an embodiment of the apparatus of the invention, Figures 2 and 3 show details of the transfer mechanism of the apparatus of figure 1, Figure 4 is a sectional view of an embodiment of the heated mold shown in its closed position, Figure 5 is a sectional view of an embodiment of the cold mold shown in its open position, Figure 6 is a sectional view of a second embodiment of the heated mold of the invention, shown in closed position, during molding operation, Figure 7 is a sectional view of the molded article 11~2~66 during its transfer ~rom the heated mold to the cold mold, and Figure 8 is a sectional view of the second embodiment of the cold mold of the invention shown in closed position during the final molding operation.
Detaile_ description of the drawings Referring now to figure l, the apparatus of the invention for manufacturing expanded thermoplastic material acticles includes a frame 1, made from tubes or steel sections supporting a container 2 to store the raw material in the form of expanded polystyrene beads 3, a container 4 for collecting the articles produced, and various units for the transformation of the raw material and for the control of the apparatus.
These various units comprise essentially the male portion 5 and the female portion (not shown) of a heated mold, the male portion 6 and female portion 7 of the cold mold (described in detail with reference to figures 4 and 5) and one member 8 to transfer the article from the heated mold into the cold mold. The male portion 5 of the heated mold is mounted at the lower end of the member 8 which is positioned so that it can slide on a shaft 9 under the action of a piston lO received in a housing ll of prismatic configuration. In addition, the member 8 can pivot in its plan like a pendulum about said shaft 9 between a first position into which the male portion 5 of the heated mold is placed in front of its corresponding female portion and a second position wherein the portion 5 is in front of the portion 7 of the cold mold to effect the transfer of the article and introduce it in mold portion 7. This swinging motion is obtained through a mechanism 12 which is shown in more detail in figures 2 and 3.
The male portion 6 of the cold mold is mounted on the free end of a piston rod 13 which is slidably received into a cylinder 14 to reciprocate horizontally. Also supported by the 1~2~66 frame 1 is a control panel 15 for the control of various elements of the apparatus.
The transfer mechanism will be now described with reference to figures 2 and 3. The mechanism 12 substantially comprises two slides 16, 17 and a plate 18 which can slide vertically in slides 16 and 17 under the action of a piston 19 slidably received into a cylinder 20 and connected to the plate 18 by a rod 21. A curvilinear opening 22 is formed in the plate 18 into which is engaged the end of a pin 23 connected to the housing 11. Once the piston 19 is moved downwards (as shown on figure 3) by a fluid under pressure fed to the cylinder 20, the end of pin 23 is guided in the curvilinear opening acting as a cam and driving the housing 11 together with the pin to a position 11' shown in dotted lines. The housing 11 rigidly fixed to the member 8, the pendulum or swinging motion of the latter is derived from the mechanism 12. The position 11' (as shown in figure 3) of the housing 11 corresponds to the new position 18' of the plate 18 and 23' of the pin end 23.
Figure 4 shows schematically an embodiment of the heated mold which comprises a male portion 41 and a female portion 42 into which is formed a molding cavity 43 to be filled with thermoplastic material. An inlet passage 44 for steam in the male portion 41 is connected to internal passages 45 which themselves terminate into nozzles 46. The purpose of these nozzles is to inject steam into the molding cavity 43 to expand the thermo-plastic beads therein. The female portion 42 is aiso provided with a tapered injection inlet passage 47 for the thermoplastic material with steam exhaust nozzles 48 for the excess steam which are in communication with the outlet steam ports 49, and with a condensed water exhaust port 50.
Figure 5 shows schematically an embodiment of a cold mold including a male portion 51 and a female portion 52 of this mold. Both members are so constructed as the molding cavity has exactly the configuration and size of the article 53 to be produced. The mold portion 52 is equiped with pushing means adapted to eject the finished article out of the cold mold. This means comprises a plate 54 which can be mechanically moved by a rod 55 or pneumatically pushed by a device connected to the port 56.
In operation of the device described above, the male portion 5, 41 of the heated mold is urged against the female portion 42 of said heated mold by means of a piston 10, thus providing a molding cavity having approximately the configuration ; of the article to be produced. This mold is heated by well-known means not represented. Once the heated mold is ready for the injection process the pre-expanded polystyrene beads 3 contained in the storing container are introduced into themolding cavity through an injector. The expansion and agglomeration of the thermoplastic material beads are obtained by means of steam injected into the heated mold through the injection nozzles 46.
As soon as the expansion of the material is completed, the male portion 5,41 of the heated mold integral with the member 8 is moved to the left (as shown on figure 1) by means of the piston 10; the article injected into the molding cavity remains onto this male portion of the heated mold and can freely further expand thus providing stress relieving.
Thereafter, the piston 19 is moved downwards (as seen on figure 3) inside the cylinder 20 moving together with the plate 18 thus moving the end of pin 23 from its initial position shown in figure 2 to its final position 23 shown in dotted lines in figure 3. The motion of pin 23 pivotably moves simultaneously the housing 11 and themember 8 about shaft 9.
In the final position of the member 8, the male portion 5,41 of the heated mold is aligned with the female portion 7,52 of the l~Z~i6 cold mold into which the now completely relaxed molded article will be partially engaged. At that timet:hepiston 19 is moved again upwards causing simultaneously the housing 11 and the element 8 to swing back to their initial positions. For completely inserting the preformed article into the cold mold, a fluid under pressure is injected into the cylinder 14 in order to move the piston 13 to the right (as seen on figure 1). The male portion 6,51 which is rigidly fixed to the free end of the piston rod 13 will forcibly engage the preformed article 53 into the molding cavity of the cold mold which has exactly the configuration and size of the article which is sought to be obtained. Thereafter the piston 13 will move to the left (as seen on figure 1) and the article 53 formed exactly to the size and configuration of the cold mold will be ejected by means of a mechanical action on said push rod 55 or by the pneumatic means to finally be collected in the collecting container 4.
Another embodiment of the apparatus of the present invention will now be described with reference to figures 6,7 and8.
Specifically, in figure 6 is shown the first step of the process for the premolding injection step in the heated mold. The reference numeral 61 shows the female part of the heated mold for preforming the article, reference 62 shows the male portion of the mold. Reference 63 shows the molding cavity, reference 64 shows the injection device through which the pre-expanded material beads are forced into the molding cavity reference 65 shows the injector body, reference 66 shows heating bands and references 67 and 68 are inlet and exhaust passages for steam.
Figure 7 is a section view of the molded article at the time of its transfer from the first heated mold to the second and final cold mold.
Figure 8 shows the second and final molding step into the cold mold. In this figure reference 69 shows the female portion of the cold mold, reference 70 shows the male portion of same, references 71 and 72 show passages for circulation of cooling water, reference 73 shows the molding cavity and reference 74 shows the ejector for the finished article.
While the present invention has been described with reference to two preferred embodiments, many alternatives changes and modifications will appear to those skilled in the art such as particularly:
- as the transfer time of the pre-formed article from the heated mold to the cold mold is not critical per se, it is possible to design a machine having two stations, one station for hot molding positioned at some distance of a second station for cold molding, both stations being connected by the transfer means, - the preformed articles can be molded under vacuum into the cold mold. This technique enables to considerably increase the relative pressure inside the expanded thermoplastic material beads which permits easier production of low density articles.
- both molds can be on the same molding press or on separate presses, -one first preforming heated mold can be provided for several second cooled molds or vice-versa, - the transfer device between molds can be mechanical, pneumatic or of another type, - heat transfer from the heating mold to the thermo-plastic material can be made by any known means such as electrical resistors, steam and heated oil.
Further to the multiple advantages already mentioned, the method of the invention enables to obtain articles having a higher density which are more resilient than similar articles molded with the standard method. These articles are more flexible and less brittle, which gives them an improved ability for acting ll~znf~6 as shock or impact absorbing pads, especially when they are used for packaging.
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,i -- 11 --
Eield of the in ention The present invention relates to a molding method and apparatus for molding articles of expanded plastic material.
Molding methods for articles of expanded thermoplastic material have been known heretofore and especially methods for manufacturing articles obtained by agglomerating pre-expanded polystyrene beads.
- Presently these methods are commonly used for manu-facturing blocks, supports or shells for packaging food products, machinery or household electrical appliances etc... . They have excellent impact resistance, they are weatherresistant and their cost is relatively low.
Description of the prior art Usually, the known molding techniques include the following steps;
- filling a molding cavity of a mold with pre-expanded polystyrene beads - injecting steam for heating said beads to the softening temperature of the polymer and above the boiling point of the porogeneous fluid which is contained in said beads. Said steam causes, the beads to expand and bring them to a partially molded state causing them to agglomerate into a homogeneous cellular mass.
- cooling the product obtained in a cellular state contained in the mold in order to prevent a second expansion or a distortion of the molded article; and, once the mold is cooled - withdrawing the molded article from the mold, after which the mold can be heated again for the next molding cycle.
This method involves the use of considerable heating system and means for rapidly cooling the mold in order that the two alternate steps, i.e. heating the mold and cooling thereof, - 1 - ~
'~;
do not increase excessively the manufacturing of the article.
l3Owever, since the article is made from an excellent heat insulating material, this method results in a very limited production rate, and reduces drastically the efficiency and the profitability of the molding equipment.
Another disadvantage which effects this method is the consumption of energy. For example, for a medium size article when heating 0.150 kg of thermoplastic material contained in the mold it is also necessary to heat, at each molding cycle, the 150 kg of the mold material itself. It can be realized that this mass ratio of about 1 to 1000 brings in a considerab]e loss of energy which heavily affects the cost of the finished product.
In order to reduce the manufacturing cost it has been proposed to provide molds with multiple molding cavities. This approach is valid for small size articles only and on the other `!
hand the design and the manufacturing of the molds which have to be machined accurately, from a good heat conducting material, such as aluminum, are very expensive.
Also the expenses for unavoidable servicing and maintenance of so complex an equipment have to be taken into - consideration. In order to carry out successive cooling operations, the mold is provided with internal passages which allow the cooling water to circulate. If this water is not treated, calcar deposits thereof will block the injection nozzles and attack the walls of the mold or of its auxiliary equipment. Further, for economical reasons, the factories that are using the known method, use cooling systems which operate in close circuit and consequently ll~ZC~66 include storage containers, tanks for water treatment, water cooling towers and pumping stations which considerably affect the production cost of the molded articles of expanded polystyrerle produced in mass production.
The present invention provides a method and apparatus overcoming the above mentioned disadvantages.
According to the present invention there is provided a method for forming shaped articles from pre-expanded thermo-plastic beads, in two cycles, comprising a first cycle which includes the stages of introducing said beads into a mold cavity of a first mold to fill said mold cavity, wherein said first mold comprises two members, a male member and a female member, and wherein said first mold is maintained at a substantially constant elevated temperature throughout said two cycles, inject-ing steam into said first mold to cause the beads to expand, partially melt, agglomerate and form a shaped cellular preform, disengaging said two members of the first mold whereby said pre-form is retained by one mold member of said first mold, and a second cycle which includes the stages of transferring said shaped cellular preform at substantially ambient pressure, from the first mold to a second mold, by conveying said preform on said first mold member which retains said preform to said second mold, whereby the shaped preform is free to expand under the conditions of the stage of transferring, wherein said second mold is at a second substantially constant temperature throughout said two cycles, wherein said second substantially constant temperature is lower than said substantially constant elevated temperature and wherein the cavity of said second mold has the shape of the ultimate shaped article, cooling and compressing said shaped cellular preform in said second mold, and removing the finished article from said second mold.
The apparatus of the invention includes a first mold comprising male and female members defining a molding cavity having at least approximately the shape and size of the article to be produced; means for maintaining this mold at a constant temperature between 90C and 130C, and preferably about 120C;
an injection device for introducing beads of thermoplastic material into the molding cavity; one or more injection nozzles for injecting steam into the molding cavity; a mechanical or pneumatic device for ejecting the preformed article on one said member from the heated mold; means for transferring said article , on the one member and introducing the article into a second mold comprising a molding cavity having the exact shape and size of the article to be produced, this mold being maintained at a temperature lower than that of the first heated mold; and mechanical or pneumatic means to withdraw the article from said mold.
The method of the invention has many advantages over the prior art since it enables the production time to be reduced, the production cost to be reduced and, considerably simplifies the installation lay-out to increase its efficiency and profitability; in addition, with the method of the present invention, lower density materials can be obtained hence permitting material savings.
According to a preferred embodiment of the present invention, the article formed or premolded inside the heated mold is withdrawn as soon as the first molding step is completed for . - 4 -. ~ ., llC;~6:?66 being transferred in the cold mold. From this very moment, a new article can be injected in the heated mold thus permitting to reduce considerably the total molding cycle time, this time being reduced to about 10 seconds/article, for medium sized items.
The mold being no longer subject to the stresses due to the repeated and substantial temperature variations, can be constructed from any material including metals, synthetic materials or even wood. The construction of the mold is only limited by well known design and techniques of the injection or compression molds. The mold design is simplified in that the passages for circulating cooling water into the mold which are necessary with the conventional methods and apparatuses are eliminated in the apparatus of the invention or are at least of a much simplified structure.
Brief Description of the Drawings The objects and advantages of the present invention will become apparent upon reading the following detailed description of a preferred embodiment and alternatives and upon reference to the drawings in which:
Figure 1 is a schematic view of-an embodiment of the apparatus of the invention, Figures 2 and 3 show details of the transfer mechanism of the apparatus of figure 1, Figure 4 is a sectional view of an embodiment of the heated mold shown in its closed position, Figure 5 is a sectional view of an embodiment of the cold mold shown in its open position, Figure 6 is a sectional view of a second embodiment of the heated mold of the invention, shown in closed position, during molding operation, Figure 7 is a sectional view of the molded article 11~2~66 during its transfer ~rom the heated mold to the cold mold, and Figure 8 is a sectional view of the second embodiment of the cold mold of the invention shown in closed position during the final molding operation.
Detaile_ description of the drawings Referring now to figure l, the apparatus of the invention for manufacturing expanded thermoplastic material acticles includes a frame 1, made from tubes or steel sections supporting a container 2 to store the raw material in the form of expanded polystyrene beads 3, a container 4 for collecting the articles produced, and various units for the transformation of the raw material and for the control of the apparatus.
These various units comprise essentially the male portion 5 and the female portion (not shown) of a heated mold, the male portion 6 and female portion 7 of the cold mold (described in detail with reference to figures 4 and 5) and one member 8 to transfer the article from the heated mold into the cold mold. The male portion 5 of the heated mold is mounted at the lower end of the member 8 which is positioned so that it can slide on a shaft 9 under the action of a piston lO received in a housing ll of prismatic configuration. In addition, the member 8 can pivot in its plan like a pendulum about said shaft 9 between a first position into which the male portion 5 of the heated mold is placed in front of its corresponding female portion and a second position wherein the portion 5 is in front of the portion 7 of the cold mold to effect the transfer of the article and introduce it in mold portion 7. This swinging motion is obtained through a mechanism 12 which is shown in more detail in figures 2 and 3.
The male portion 6 of the cold mold is mounted on the free end of a piston rod 13 which is slidably received into a cylinder 14 to reciprocate horizontally. Also supported by the 1~2~66 frame 1 is a control panel 15 for the control of various elements of the apparatus.
The transfer mechanism will be now described with reference to figures 2 and 3. The mechanism 12 substantially comprises two slides 16, 17 and a plate 18 which can slide vertically in slides 16 and 17 under the action of a piston 19 slidably received into a cylinder 20 and connected to the plate 18 by a rod 21. A curvilinear opening 22 is formed in the plate 18 into which is engaged the end of a pin 23 connected to the housing 11. Once the piston 19 is moved downwards (as shown on figure 3) by a fluid under pressure fed to the cylinder 20, the end of pin 23 is guided in the curvilinear opening acting as a cam and driving the housing 11 together with the pin to a position 11' shown in dotted lines. The housing 11 rigidly fixed to the member 8, the pendulum or swinging motion of the latter is derived from the mechanism 12. The position 11' (as shown in figure 3) of the housing 11 corresponds to the new position 18' of the plate 18 and 23' of the pin end 23.
Figure 4 shows schematically an embodiment of the heated mold which comprises a male portion 41 and a female portion 42 into which is formed a molding cavity 43 to be filled with thermoplastic material. An inlet passage 44 for steam in the male portion 41 is connected to internal passages 45 which themselves terminate into nozzles 46. The purpose of these nozzles is to inject steam into the molding cavity 43 to expand the thermo-plastic beads therein. The female portion 42 is aiso provided with a tapered injection inlet passage 47 for the thermoplastic material with steam exhaust nozzles 48 for the excess steam which are in communication with the outlet steam ports 49, and with a condensed water exhaust port 50.
Figure 5 shows schematically an embodiment of a cold mold including a male portion 51 and a female portion 52 of this mold. Both members are so constructed as the molding cavity has exactly the configuration and size of the article 53 to be produced. The mold portion 52 is equiped with pushing means adapted to eject the finished article out of the cold mold. This means comprises a plate 54 which can be mechanically moved by a rod 55 or pneumatically pushed by a device connected to the port 56.
In operation of the device described above, the male portion 5, 41 of the heated mold is urged against the female portion 42 of said heated mold by means of a piston 10, thus providing a molding cavity having approximately the configuration ; of the article to be produced. This mold is heated by well-known means not represented. Once the heated mold is ready for the injection process the pre-expanded polystyrene beads 3 contained in the storing container are introduced into themolding cavity through an injector. The expansion and agglomeration of the thermoplastic material beads are obtained by means of steam injected into the heated mold through the injection nozzles 46.
As soon as the expansion of the material is completed, the male portion 5,41 of the heated mold integral with the member 8 is moved to the left (as shown on figure 1) by means of the piston 10; the article injected into the molding cavity remains onto this male portion of the heated mold and can freely further expand thus providing stress relieving.
Thereafter, the piston 19 is moved downwards (as seen on figure 3) inside the cylinder 20 moving together with the plate 18 thus moving the end of pin 23 from its initial position shown in figure 2 to its final position 23 shown in dotted lines in figure 3. The motion of pin 23 pivotably moves simultaneously the housing 11 and themember 8 about shaft 9.
In the final position of the member 8, the male portion 5,41 of the heated mold is aligned with the female portion 7,52 of the l~Z~i6 cold mold into which the now completely relaxed molded article will be partially engaged. At that timet:hepiston 19 is moved again upwards causing simultaneously the housing 11 and the element 8 to swing back to their initial positions. For completely inserting the preformed article into the cold mold, a fluid under pressure is injected into the cylinder 14 in order to move the piston 13 to the right (as seen on figure 1). The male portion 6,51 which is rigidly fixed to the free end of the piston rod 13 will forcibly engage the preformed article 53 into the molding cavity of the cold mold which has exactly the configuration and size of the article which is sought to be obtained. Thereafter the piston 13 will move to the left (as seen on figure 1) and the article 53 formed exactly to the size and configuration of the cold mold will be ejected by means of a mechanical action on said push rod 55 or by the pneumatic means to finally be collected in the collecting container 4.
Another embodiment of the apparatus of the present invention will now be described with reference to figures 6,7 and8.
Specifically, in figure 6 is shown the first step of the process for the premolding injection step in the heated mold. The reference numeral 61 shows the female part of the heated mold for preforming the article, reference 62 shows the male portion of the mold. Reference 63 shows the molding cavity, reference 64 shows the injection device through which the pre-expanded material beads are forced into the molding cavity reference 65 shows the injector body, reference 66 shows heating bands and references 67 and 68 are inlet and exhaust passages for steam.
Figure 7 is a section view of the molded article at the time of its transfer from the first heated mold to the second and final cold mold.
Figure 8 shows the second and final molding step into the cold mold. In this figure reference 69 shows the female portion of the cold mold, reference 70 shows the male portion of same, references 71 and 72 show passages for circulation of cooling water, reference 73 shows the molding cavity and reference 74 shows the ejector for the finished article.
While the present invention has been described with reference to two preferred embodiments, many alternatives changes and modifications will appear to those skilled in the art such as particularly:
- as the transfer time of the pre-formed article from the heated mold to the cold mold is not critical per se, it is possible to design a machine having two stations, one station for hot molding positioned at some distance of a second station for cold molding, both stations being connected by the transfer means, - the preformed articles can be molded under vacuum into the cold mold. This technique enables to considerably increase the relative pressure inside the expanded thermoplastic material beads which permits easier production of low density articles.
- both molds can be on the same molding press or on separate presses, -one first preforming heated mold can be provided for several second cooled molds or vice-versa, - the transfer device between molds can be mechanical, pneumatic or of another type, - heat transfer from the heating mold to the thermo-plastic material can be made by any known means such as electrical resistors, steam and heated oil.
Further to the multiple advantages already mentioned, the method of the invention enables to obtain articles having a higher density which are more resilient than similar articles molded with the standard method. These articles are more flexible and less brittle, which gives them an improved ability for acting ll~znf~6 as shock or impact absorbing pads, especially when they are used for packaging.
.
,i -- 11 --
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for forming shaped articles from pre-expanded thermoplastic beads, in two cycles, comprising a first cycle which includes the stages of introducing said beads into a mold cavity of a first mold to fill said mold cavity, wherein said first mold comprises two members, a male member and a female member, and wherein said first mold is maintained at a substant-ially constant elevated temperature throughout said two cycles, injecting steam into said first mold to cause the beads to expand, partially melt, agglomerate and form a shaped cellular preform, disengaging said two members of the first mold whereby said preform is retained by one mold member of said first mold, and a second cycle which includes the stages of transferring said shaped cellular preform at substantially ambient pressure, from the first mold to a second mold, by conveying said preform on said first mold member which retains said preform to said second mold, whereby the shaped preform is free to expand under the conditions of the stage of transferring, wherein said second mold is at a second substantially constant temperature throughout said two cycles, wherein said second substantially constant temperature is lower than said substantially constant elevated temperature and wherein the cavity of said second mold has the shape of the ultimate shaped article, cooling and compressing said shaped cellular preform in said second mold, and removing the finished article from said second mold.
2. A method according to claim 1 wherein said heated mold is a first mold comprising a molding cavity having at least the approximate configuration and size of the article to be produced and wherein said cooled mold is a second mold compri-sing a molding cavity having the configuration and size of the article to be produced, said first heated mold being maintained at a temperature between 90°C and 130°C, and said first cooled mold being at a temperature lower than 90°C.
3. A method according to claim 2 wherein said heated mold temperature is 120°C.
4. A method according to claim 2 wherein the molding cavity of said second mold is maintained under partial vacuum during at least part of the time of the final forming step.
5. An apparatus for forming shaped articles from pre-expanded thermoplastic beads, said apparatus comprising a first mold, comprising a male and female member defining a mold-ing cavity having at least approximately the configuration and size of the article to be produced; means for maintaining said mold at a constant temperature between 90°C and 130°C; injection means for introducing beads of thermoplastic material into the molding cavity; one or more injection nozzles for injecting steam into the molding cavity; means for removal of a preformed article out of the heated mold on one member thereof; means for trans-ferring said preformed article on said one member and introducing the preformed article into a second cooled mold comprising a molding cavity having the exact configuration and size of the article to be produced and which is maintained at a temperature lower than that of said heated mold; and, means for ejecting the final article from said cooled mold.
6. An apparatus according to claim 5 wherein said heated mold is adapted to be maintained at a temperature of about 120°C.
7. An apparatus as claimed in claim 5 or 6 in which said one member on which the preformed article is transferred is the male member of the first mold.
8. A process as claimed in claim 1, 2 or 3 in which the member on which the preformed article is transferred is the male member of the first mold.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7601160A FR2338124A1 (en) | 1976-01-16 | 1976-01-16 | Twin tool system for moulding expanded thermoplastics - for improved thermal efficiency and quicker cycles |
| FR7601160 | 1976-01-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1102066A true CA1102066A (en) | 1981-06-02 |
Family
ID=9168043
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA265,052A Expired CA1102066A (en) | 1976-01-16 | 1976-11-05 | Method and apparatus for molding expanded plastic material articles |
Country Status (7)
| Country | Link |
|---|---|
| JP (2) | JPS588335B2 (en) |
| AT (1) | AT366624B (en) |
| CA (1) | CA1102066A (en) |
| ES (1) | ES453117A1 (en) |
| FI (1) | FI763164A (en) |
| FR (1) | FR2338124A1 (en) |
| NZ (1) | NZ182480A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120038081A1 (en) * | 2008-11-05 | 2012-02-16 | Aston Martin Lagonda Limited | Manufacture of a Structural Composites Component |
| US12000329B2 (en) | 2018-12-17 | 2024-06-04 | Aston Martin Lagonda Limited | Assemblies for engines |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5549231A (en) * | 1978-10-03 | 1980-04-09 | Badische Yuka Co Ltd | Manufacturing method for foam resin formed product |
| DE2847557C2 (en) * | 1978-11-02 | 1987-08-20 | Fa. E.A. Heitz, 6718 Grünstadt | Device for the production of molded parts from foam plastic |
| DE2903495C2 (en) * | 1979-01-30 | 1985-02-21 | Joachim Ing.(Grad.) 7712 Blumberg Teubert | Process for the production of molded bodies from foamed plastic, in particular from foamed polystyrene |
| JPS6056106B2 (en) * | 1979-12-03 | 1985-12-09 | 積水化成品工業株式会社 | Foam molding method |
| JPS6056107B2 (en) * | 1979-12-04 | 1985-12-09 | 積水化成品工業株式会社 | Foam molding method |
| JPS6056108B2 (en) * | 1979-12-05 | 1985-12-09 | 積水化成品工業株式会社 | Foam molding equipment |
| JPS5698149A (en) * | 1980-01-07 | 1981-08-07 | Sekisui Plastics Co Ltd | Foam molding and apparatus |
| JPS5653047A (en) * | 1980-04-04 | 1981-05-12 | Badische Yuka Co Ltd | Production of foamed resin molding |
| JPS58183226A (en) * | 1982-04-20 | 1983-10-26 | Kanegafuchi Chem Ind Co Ltd | Method and apparatus for obtaining molding body having different density from each other |
| AT385717B (en) * | 1984-10-24 | 1988-05-10 | Hirsch Kurt Kunststoff | STACKING DEVICE |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3676033A (en) * | 1968-04-30 | 1972-07-11 | Robert B Buonaiuto | Apparatus for making thermoplastic cellular products |
| JPS5112181B2 (en) * | 1971-09-10 | 1976-04-16 |
-
1976
- 1976-01-16 FR FR7601160A patent/FR2338124A1/en active Granted
- 1976-10-09 JP JP51120848A patent/JPS588335B2/en not_active Expired
- 1976-11-01 NZ NZ182480A patent/NZ182480A/en unknown
- 1976-11-04 FI FI763164A patent/FI763164A/fi not_active Application Discontinuation
- 1976-11-05 CA CA265,052A patent/CA1102066A/en not_active Expired
- 1976-11-05 AT AT0822076A patent/AT366624B/en not_active IP Right Cessation
- 1976-11-08 ES ES453117A patent/ES453117A1/en not_active Expired
-
1981
- 1981-10-16 JP JP56165595A patent/JPS5795426A/en active Granted
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120038081A1 (en) * | 2008-11-05 | 2012-02-16 | Aston Martin Lagonda Limited | Manufacture of a Structural Composites Component |
| US9643363B2 (en) * | 2008-11-05 | 2017-05-09 | Aston Martin Lagonda Limited | Manufacture of a structural composites component |
| US12000329B2 (en) | 2018-12-17 | 2024-06-04 | Aston Martin Lagonda Limited | Assemblies for engines |
Also Published As
| Publication number | Publication date |
|---|---|
| AT366624B (en) | 1982-04-26 |
| JPS588335B2 (en) | 1983-02-15 |
| ATA822076A (en) | 1981-09-15 |
| JPS5795426A (en) | 1982-06-14 |
| JPS5290578A (en) | 1977-07-29 |
| FR2338124B1 (en) | 1979-08-10 |
| JPS6149102B2 (en) | 1986-10-28 |
| FR2338124A1 (en) | 1977-08-12 |
| NZ182480A (en) | 1979-10-25 |
| FI763164A (en) | 1977-07-17 |
| ES453117A1 (en) | 1978-01-16 |
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