STABILIZED INJECTION MOLDING WHEN USING A COMMON MOLD PART WITH SEPARATE COMPLEMENTARY MOLD PARTS

Abstract: A process for injection molding a thin-walled, hollow plastic product (88). A first common mold part (10) is combined with a first complementary mold part (12) to assemble a first mold cavity (14). Portions of the first complementary mold part (12) contact portions of the first common mold part (10) to rigidly secure mold parts (10, 12) in a position which impedes movement of the mold parts (10, 12) in relation to each other during injection of a first plastic material (20) into the first mold cavity (14). The first plastic material (20) is shaped such that when it is contained in a second mold cavity (28), which is formed by combining the first common mold part (10) with a second complementary mold part (26), it provides stabilizing regions (68) that rigidly secure the mold parts (10, 26) in a position which impedes movement during injection of a second plastic material (32).

Description: STABILIZED INJECTION MOLDING WHEN USING A COMMON MOLD PART WITH SEPARATE COMPLEMENTARY MOLD PARTS BACKGROUND OF THE INVENTION The present invention generally pertains to injection molding of plas products and is particularly directed to stabilizing the dimensions of mold caviti during the injection steps when using a common mold part and at least t complementary mold parts to assemble separate mold cavities for receivi separate injections of plastic materials to produce a thin-walled, hollow plas product. The use of a common mold part with at least two complementary m parts to provide separate mold cavities for receiving separate injections of plas materials for producing a hollow plastic product is known. In one known prior method of cyclic injection molding a hollow plastic product a first mold cavity defined by a first common mold part and a first complementary mold part; and second mold cavity is defined by the first common mold part and a seco complementary mold part. The method includes the steps of: (a) combining the first common mold part with the first complementa mold part to assemble the first mold cavity; (b) injecting a first plastic material into the first mold cavity; (c) solidifying the injected first plastic material to form a first plas material component; (d) combining the first common mold part with the seco complementary mold part to assemble the second mold cavity with the first plast material component attached to the first common mold part so that when t second mold cavity is assembled the first plastic material component is contain within the second mold cavity; ■ ' (e) injecting a second plastic material into the second mold cavity wh the first plastic material component is contained therein; and (f) solidifying the injected second plastic material so as to form a seco plastic material component that fuses with the first plastic material component produce a hollow plastic product. It also is known to expand upon this method by further using a thi mold cavity defined by a second common mold part and the first complementa mold part, and a fourth mold cavity defined by the second common mold part a the second complementary mold part. The method further includes the steps of: (h) during step (d), combining the second common moid part with t first complementary mold part to assemble the third mold cavity; (i) during step (e), injecting a third plastic material into the third m cavity; (j) during step (f), solidifying the injected third plastic material to form third plastic material component; (k) during step (a), combining the second common mold part with t second complementary mold part to assemble the fourth mold cavity with the th plastic material attached to the second common mold part so that when the fou mold cavity is assembled the third plastic material is contained within the fou mold cavity; (I) during step (b), injecting the fourth plastic material into the fou mold cavity while the solidified third plastic material is contained therein; and (m) during step (c), solidifying the injected fourth plastic material so as form a fourth plastic material component that fuses with the third plastic mate to produce a second said hollow plastic product. This method has been used for producing hollow plastic products hav composite walls of separately injected plastic materials. In performing s method, the first plastic material is injected until it reaches the parting l between the first common mold part and the first complementary mold part; second plastic material is injected until it reaches the parting line between the f common mold part and the second complementary mold part; the third pla material is injected until it reaches the parting line between the second com mold part and the first complementary mold part; and the fourth plastic materia injected until it reaches the parting line between the second common moid and the second complementary moid part. Typically, all four plastic materials are the same. SUMMARY OF THE INVENTION The present invention provides a method and apparatus for injecti molding hollow, thin-walled plastic products, wherein relative movement betw the common mold part and the complementary mold parts is impeded duri injection of the plastic materials. According to the present invention, in the injection molding meth described above, the step of solidifying the injected first plastic material to fo the first plastic material component (step (c)) includes the step of (g) shaping the first plastic material component such that when the fi plastic material component is so contained in the second mold cavity the fi plastic material component provides one or more stabilizing regions that rigi secure the first common mold part in position in relation to the seco complementary mold part in order to impede movement of the first common m part in relation to the second complementary mold part during the injection of t second plastic material into the second mold cavity, to thereby produce a thi walled plastic product having controlled dimensions in that the wall-thickne dimensions of the second mold cavity are stabilized by the stabilizing regions. When the method of the present invention utilizes two common m cavities, such as described above, the step of solidifying the injected third plas material to form the third plastic material component (step 0)) includes the step shaping the third plastic material component such that when the third plas material component is so contained in the fourth mold cavity the solidified th plastic material provides one or more stabilizing regions that rigidly secure t second common mold part in position in relation to the second complement mold part in order to impede movement of the second common mold part relation to the second complementary mold part during the injection of the fou plastic material into the fourth mold cavity, to thereby produce a second thi walled plastic product having controlled dimensions. The method of the present invention may also be used for molding product having a side wall including an approximately longitudinal strip that m be transparent to provide a transparent window in the side wall. This feature particularly advantageous when it is desired to provide a longitudinal window the side wall in order to monitor the level of a substance, such as a fl contained in the plastic product. In one embodiment, the first plastic mate component is shaped to provide at least one stabilizing region that is transverse a parting line between the first common mold part and the first complement mold part, whereby the longitudinal strip is defined by the transverse stabilizi region. A transparent window is provided in the side wall by injecting transparent first plastic material into the first mold cavity. A nontranspar second plastic material is injected into the second mold cavity to provide nontransparent background for .printing in the remainder of the side wall. In alternative embodiment, the first plastic material component is shaped such t when the first plastic material component is contained in the second mold cavi the second moid cavity defines at least one unfilled cavity region that is transver to a parting line between the first common mold part and the seco complementary mold part, whereby the longitudinal strip is defined by the unfill transverse cavity region. In this embodiment, a transparent window is provided the side wall by injecting a transparent second plastic material into the seco mold cavity; and a nontransparent first plastic material is injected into the fir mold cavity to provide a nontransparent background for printing in the remaind of the side wall. In another aspect of the method of the present invention, the step shaping the first plastic material component (step (g)) may further include the st of providing a first complementary mold part that is dimensioned in relation to t first common mold part such that when combined with the first common mol part to assemble the first mold cavity, portions of the first complementary moi part contact portions of the first common mold part to rigidly secure the fir common mold part in position in relation to the first complementary mold part i order to impede movement of the first common mold part in relation to the fir complementary mold part during the injection of the first plastic material into th first mold cavity. The present invention further provides apparatus for performing th method of the present invention and hollow, thin-walled plastic products molde according to the method of the present invention. Additional features of the present invention are described in relation t the description of the preferred embodiments. BRIEF DESCRIPTION OF THE DRAWING Figures 1A and IB are sectional views illustrating a first mold cavi assembled by combining a first common mold part with a first complementa mold part. Figure 1A is a top sectional view taken along lines A-A in Figure I and Figure IB is a side sectional view taken along lines B-B in Figure 1A. Figur 1A and 1B further show the first plastic material injected into the first mold cavit Figures 2A and 2B are sectional views illustrating a second mold cavi assembled by combining the first common mold part of Figures 1A and IB with second complementary mold part. Figure 2A is a top sectional view taken alo lines A-A in Figure 2B; and Figure 2B is a side sectional view taken along lines B in Figure 2A. Figures 2A and 2B further show the first plastic material compone contained in the second moid cavity and the second plastic material injected in the second mold cavity. Figures 3A through 3D illustrate a series of steps in the performance of preferred embodiment of the method of the present invention. Figure 4 illustrates a first plastic material component formed in alternative embodiment of the method of the present invention. Figure 5 is a sectional view illustrating a second mold cavity containi the first plastic material component of Figure 4. Figure 5 also is a sectional vi illustrating a product molded according to such alternative embodiment of t method of the present invention. Figure 6 illustrates a first plastic material component formed in a furth alternative embodiment of the method of the present invention. Figure 7 is a sectional view illustrating a second moid cavity containi the first plastic material component of Figure 6. Figure 5 also provides a sectio view of a product molded according to such further alternative embodiment of t method of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figures 1A and 1B the apparatus of a preferred embodime of the present invention includes a first common mold part 10 and fir complementary mold part 12. The first common mold part 10 is combined wi the first complementary mold part 12 to assemble a first mold cavity 14. The fir complementary mold part 12 is dimensioned in relation to the first common mo part 10 such that when so combined with the first common mold part 10 assemble the first mold cavity 14, portions 16 of the first complementary mo part 12 contact portions 18 of the first common mold part 10 to rigidly secure t first common mold part 10 in position in relation to the first complementary mo part 12 in order to impede movement of the first common mold part 10 in relati to the first complementary mold part 12 during injection of the first plast material 20 into the first mold cavity 14. The first plastic material 20 is inject into the mold cavity 14 through a gate 22 and a runner 24 in the fir complementary mold part 12. The injected first plastic material 20 is solidified to form a first plast material component 20 by cooling the injected first plastic material in the fir mold cavity 14, whereby the first plastic material component 20 is shaped i accordance with the dimensions of the first mold cavity 14. In an alternati embodiment, the first plastic material component may be further shaped followin removal of the first complementary mold part 12. Referring to Figures 2A and 2B the apparatus of a preferred embodime of the present invention includes a second complementary mold part 26. The fir common mold part 10 is combined with the second complementary mold part 2 to assemble a second mold cavity 28 with the first plastic material component 2 attached to the first common mold part 10, so that when the second mold cav 28 is assembled, the first plastic material component 20 is contained within second mold cavity 28. The first plastic material component 20 is shaped such that when the fi plastic material component 20 is so contained in the second mold cavity 28 first plastic material component 20 provides one or more stabilizing regions that rigidly secure the first common mold part 10 in position in relation to second complementary mold part 26 in order to impede movement of the fi common mold part 10 in relation to the second complementary mold part during the insertion of a second plastic material 32 into the second moid cavity The second plastic material 32 is injected into the second mold cavity through a gate 34 and a runner 36 in the second complementary mold part while the first plastic material component 20 is contained in the second m cavity 28. The injected second plastic material 32 is solidified by cooling in second mold cavity 28 so as to form a second plastic material component 32 t fuses with the first plastic material component 20 to produce thin-walled holl plastic product 38 having controlled dimensions. A preferred embodiment of a method of cyclic injection molding hollow, thin-walled plastic products according to the present invention, utiliz two common mold parts and two complementary mold parts to provide four m cavities is described with reference to Figures 3A through 3D. Referring to Figure 3A, a second common mold part 40 is combined the first complementary mold part 12 to assemble a third mold cavity 42; while the same time the first common mold part 10 is combined with the sec complementary mold part 26 to assemble a second mold cavity 28, with the f plastic material component 18 attached to the first common mold part 10, so th when the second mold cavity 28 is assembled, the first plastic material compone 20 is contained within the second mold cavity 28. The formation of the fir plastic material component 20 is discussed above in relation to Figures 1A and I A third plastic material 44, which may be the same as the first plast material 20, is injected into the third mold cavity 42 through the gate 22 and t runner system 24 contained in the first complementary mold part 12; while at t same time, the second plastic material 32 is injected into the second mold cavi 28 through the gate 34 and a runner system 36 contained in the seco complementary mold part 26. The injected third plastic material 44 is solidified by cooling in the thi mold cavity 42 to form a third plastic material component 44; while at the sa time the injected second plastic material 32 is solidified by cooling in the secon mold cavity 28 so as to form the second plastic material component 28 that fus with the first plastic material component 20 to produce the hollow, thin-walle plastic product 38. Referring to Figure 3B, the first common mold part 10 and the secon common mold part 40 are separated from the second complementary mold part 2 and the first complementary mold part 12 respectively; and the molded hollo thin-walled plastic product 38 is ejected from first common mold part 10, whil the third plastic material component 44 is retained on the third third commo mold part 40. The positions of the first common mold part 10 and the secon common mold part 40 are then interchanged from those shown in Figure 3B t those shown in Figure 3C. Referring to Figure 3C, the first common mold part 10 is combined wit the first complementary mold part 12 to assemble the first mold cavity 14; while the same time the second common mold part 40 is combined with the secon complementary mold part 26 to assemble a fourth mold cavity 48, with the fi plastic material component 44 attached to the third common mold part 40, so t when the fourth mold cavity 48 is assembled, the third plastic material compon 44 is contained within the fourth mold cavity 48. The formation of the third pla material component 44 is discussed above in relation to Figure 3A. The first plastic material 20, which may be the same as the third pla material 44, is injected into the first mold cavity 14 through the gate 22 and runner system 24 contained in the first complementary mold part 12; while at same time, a fourth plastic material 50, which may be identical to the sec plastic material 32, is injected into the fourth mold cavity 48 through the gate and a runner system 36 contained in the second complementary mold part 26. The injected first plastic material 20 is solidified by cooling in the f mold cavity 14 to form another first plastic material component 20; while at same time the injected fourth plastic material 50 is solidified by cooling in fourth mold cavity 48 so as to form the second plastic material component 48 t fuses with the third plastic material component 44 to produce a second holl thin-walled plastic product 52. Referring to Figure 3D, the first common mold part 10 and the sec common mold part 40 are separated from the first complementary mold part and the second complementary mold part 26 respectively; and the second mol hollow, thin-walled plastic product 52 is ejected from second common mold 40, while the first plastic material component 20 is retained on the first com mold part 10. The positions of the first common mold part 10 and the sec common mold part 40 are then interchanged from those shown in Figure 3D those shown in Figure 3A, and the cycle is repeated. As described above, the first plastic material component 20 is sha such tha when the first plastic material component 20 is contained in the sec mold cavity 28, the first plastic material component 20 provides one or mor stabilizing regions 30 that rigidly secure the first common mold part 20 in positio in relation to the second complementary mold part 12 in order to imped movement of the first common mold part 10 in relation to the secon complementary mold part 26 during injection of the second plastic material 32 int the second mold cavity 28. Likewise, the third plastic material component 44 is shaped such th when the third plastic material component 44 is contained in the fourth mol cavity 48, the third plastic material component 44 provides one or more stabilizin regions that rigidly secure the second common mold part 40 in position in relatio to the second complementary mold part 26 in order to impede movement of th second common mold part 40 in relation to the second complementary mold par 26 during injection of the fourth plastic material 50 into the fourth mold cavity 48. The method described above with reference to Figures 3A through 3 may be used for producing hollow, thin-walled plastic products having laminate walls of different plastic materials. In performing such method, the first plasti material 20 is injected until it reaches a parting line 54 between the first commo mold part 10 and the first complementary mold part 12 (Figure 3C); and the secon plastic material 32 is injected until it reaches a parting line 56 between the firs common mold part 10 and the second complementary mold part 26 (Figure 3A) Likewise, the third plastic material 44 is injected until it reaches a parting line 5 between the second common mold part 40 and the first complementary moid par (Figure 3A); and the fourth plastic material 50 is injected until it reaches a partin line 60 between the second common mold part 40 and the second complementar mold part 26. Referring to Figures 4 and 5, the method of the present invention als may be used for molding a product 62 having a side wall 64 including at least on approximately longitudinal strip that may be transparent to thereby provide transparent window in the side wall 64. In one embodiment, the first plastic material component 66 is shaped provide at least one stabilizing region 68 that is transverse to a parting line (Figure 3C) between the first common mold part 10 and the first complementa mold part 12, whereby each longitudinal strip is defined by a transverse stabilizi region 68. The stabilizing regions 68 need not extend all the way to the parti line 54. A transparent window is provided in the side wall 64 by injecting transparent first plastic material into the first mold cavity to provide the fi plastic material component 66. A nontransparent second plastic material 72 injected into the second mold cavity 74 to provide a nontransparent backgrou for printing in the remainder of the side wail 64. In an alternative embodiment, the first plastic material component 66 shaped such that when the first plastic material component 66 is contained in t second mold cavity 74, the second mold cavity 74 defines at least one unfill cavity region 72 that is transverse to a parting line 56 (Figure 3A) between the fi common mold part 10 and the second complementary mold part 26, where longitudinal strips may be provided in the unfilled transverse cavity regions The unfilled transverse cavity regions 72 need not extend all the way to t parting line 56. In this embodiment, transparent windows are defined in the si wall 64 by injecting a transparent second plastic material into the second m cavity 74 to fill the transverse cavity regions 72. Prior thereto, a nontranspare first plastic material is injected into the first mold cavity to form the first plas material component 66 and thereby provide a nontransparent background printing in the remainder of the side wall 64. Referring to Figures 6 and 7, in a further preferred embodiment, the fi plastic material component 82 that is shaped as shown in Figure 6 to include plurality of symmetrically disposed stabilizing regions 84, which exten approximately longitudinally over a portion of the side wall 86 of the molde product 88. The first plastic material component 82 is molded in a first mol cavity in accordance with the teaching of applicant's United States Pate Application No. 7,463, filed January 26, 1987 and in accordance of the abov description to the extent that such description is compatible with the teaching Application No. 7,463. After the first plastic material component 82 is formed in first mold cavity, which is assembled by combining a first complementary mol part 12 and a first common mold part 10, the first plastic component 82 is retaine on the first common mold part 10 while the first common mold part 10 i combined with a second complementary mold part 26 to assemble a second mol cavity 90, as shown in Figure 7. Referring to Figure 7, the first plastic material component 82 is shape such that when the first plastic material component 82 is contained in the secon mold cavity 90, the ficst plastic material component 82 provides one or mor stabilizing regions 84 that rigidly secure the first common moid part 10 in positio in relation to the second complementary mold part 26 in order to imped movement of the first common mold part 10 in relation to the secon complementary moid part 26 during injection of the second plastic material 92 int the second mold cavity 90. The injected second plastic material 92 is solidified by cooling in th second mold cavity 90 to form a second plastic material component 92 that fuse with the first plastic material component 82 to produce the hollow, thin-walled plastic product 88. The side wall 86 of the molded product 88 thus includes tw layers of plastic 82, 92. The molded product 88 has controlled dimensions, i generally shaped as shown in Figure 6, and has a lateral cross section as shown i Figure 7. The side wall 86 of the molded product thus includes two layers o plastic 82, 92. ' The stabilizing regions 84 have a wall thickness equal to the thickness the side wall 86 and are transverse to the parting line 56 (Figure 3A) between t first common mold part 10 and the second complementary mold part 26 to there provide longitudinal transparent windows 84 in the side wall 86. The stabilizi regions 84 need not extend all the way to the parting line 56. In a preferr embodiment of this product, the other side-wall layer 90 is nontransparent a extends throughout the majority of the side wall 86. The present invention may be modified from the embodiments illustrat and described above. The common mold parts may be cavity mold parts inste of core mold parts, as illustrated and described herein. In addition, injections plastic material into any given mold cavity may be made through more than o gate. Also, injections of plastic materials may be made into more than two mo cavities simultaneously, whereby the number of moid cavities, included in the mo may be a multiple of the number of separate mold cavities required to produce single product. For example, when using the method described and illustrat herein for producing a product composed of two plastic material componen formed following injection of plastic material into two separate mold cavities, t number of mold cavities included in the mold may be any multiple of two, i.e. 2, 6, etc. The present invention also can be used to mold products including mo than two plastic material components formed following injection of plastic mater into more than two separate mold cavities. In an embodiment requiring thr separate mold cavities, a third complementary mold part is used, and the fus first and second plastic material components are retained on the first comm mold part when the first common mold part is combined with the thi complementary mold part to assemble the third mold cavity, with the fused fi and second mold parts being shaped to stabilize the common mold in relation the third complementary mold part during injection of a third plastic material in the third mold cavity. The core-stabilization techniques described in applicant's U.S. Pate Nos. 4,381,275 and 4,508,676; U.S. Patent No. 3,737,272 to Stegmuller; and Australian Patent Specification 17,577/70 filed by Ryles and published January 1972 may be used to stabilize the common mold part in relation to the fi complementary mold part during the injection of the first plastic material in lieu the technique described above with relation to Figures 1A and 1B. The first and second plastic materials may be either the same material different materials. It sometimes advantageous to use first and second plas materials having different physical characteristics. For example, the prese invention is ideally suited for molding a hollow, thin-walled plastic product which the side wall must provide both a moisture , barrier and a gas (such Oxygen) barrier. To mold such a product, a plastic material having a desirab moisture-barrier characteristic is selected as one of the injected plastic material and a plastic material 'having a desirable gas-barrier characteristic is selected the other injected plastic material.

Claims: CLAIMS 1. A method of cyclic injection molding a thin-walled, hollow, plasti product, utilizing a first mold cavity and a second mold cavity, the first mold cavit being defined by a first common mold part and a first complementary mold par and the second mold cavity being defined by the first common mold part and second complementary mold part, the method comprising the steps of: (a) combining the first common mold part with the first complementar mold part to assemble the first mold cavity; (b) injecting a first plastic material into the first mold cavity; (c) solidifying the injected first plastic material to form a first plasti material component; (d) combining the first common mold part with the secon complementary mold part to assemble the second mold cavity with the first plasti material component attached to the first common mold part so that when th second moid cavity is assembled the first plastic material component is containe within the second mold cavity; (e) injecting a second plastic material into the second mold cavity whil the first plastic material component is contained therein; and (f) solidifying the injected second plastic material so as to form a secon plastic material component that fuses with the first plastic material component t produce a hollow plastic product; wherein step (c) comprises the step of (g) shaping the first plastic material component such that when the fir plastic material component is so contained in the second mold cavity the fir plastic material component provides one or more stabilizing regions that rigid secure the first common mold part in position in relation to the secon complementary mold part in order to impede movement of the first common mol part in relation to the second complementary mold part during step (e), to thereb produce a thin-walled plastic product having controlled dimensions. 2. A method according to claim 1, for producing a said product havin laminated walls, wherein step (b) comprises the step of (h) injecting the first plastic material until it reaches the parting lin between the first common mold part and the first complementary mold part; and wherein step (e) comprises the step of (i) injecting the second plastic material until it reaches the parting lin between the first common mold part and the second complementary mold part. 3. A method according to Claim 1 for molding a product having a sid wall including an approximately longitudinal strip, wherein step (g) comprise shaping the first plastic material component to provide at least one said stabilizin region that is transverse to a parting line between the first common mold part an the first complementary mold part, whereby said longitudinal strip is defined b said transverse stabilizing region. 4. A method according to Claim 3, wherein step (b) comprises injecting a said first plastic material that is transparent, whereby said strip defines a transparent window in the side wall; and wherein step (e) comprises injecting a said second plastic material that nontransparent. 5. A method according to Claim 1 for molding a product having a si wall including an approximately longitudinal strip, wherein step (g) compris shaping the first plastic material component such that when the first plas material component is contained in the second moid cavity, the second m cavity defines at least one unfilled cavity region that is transverse to a parting li between the first common mold part and the second complementary mold p whereby said longitudinal strip is defined by said unfilled transverse cavity regio 6. A method according to Claim 5, wherein step (b) comprises injecting a said first plastic material that nontransparent; and wherein step (e) comprises injecting a said second plastic material that transparent, whereby said strip defines a transparent window in the side wall. 7. A method according to Claim 1, for cyclic injection molding a plural of thin-walled, hollow, plastic products, further utilizing a third moid cavity and fourth mold cavity, the third mold cavity being defined by a second common m part and the first complementary mold part, and the fourth mold cavity bei defined by the second common mold part and the second complementary m part, the method further comprising the steps of: (h) during step (d), combining the second common mold part with t first complementary mold part to assemble the third mold cavity; (i) during step (e), injecting a third plastic material into the third m cavity; (j) during step (f), solidifying the injected third plastic material to form third plastic material component; (k) during step (a), combining the second common moid part with t second complementary mold part to assemble the fourth mold cavity with the thi plastic material attached to the second common mold part so that when the four mold cavity is assembled the third plastic material is contained within the four mold cavity; (I) during step (b), injecting the fourth plastic material into the four mold cavity while the solidified third plastic material is contained therein; and (m) during step (c), solidifying the injected fourth plastic material so as form a fourth plastic material component that fuses with the third plastic materi to produce a second hollow plastic product; wherein step (j) comprises the step of (n) shaping the third plastic material component such that when the thi plastic material component is so contained in the fourth mold cavity the thi plastic material component provides one or more stabilizing regions that rigidl secure the second common mold part in position in relation to the secon complementary mold part in order to impede movement of the second commo mold part in relation to the second complementary mold part during step (I), t thereby produce a second thin-walled plastic product having controlle dimensions. 8. A method according to claim 7, for producing said products havin laminated walls, wherein step (b) comprises the step of (o) injecting the first plastic material until it reaches the parting between the first common mold part and the first complementary mold part; wherein step (e) comprises the step of (p) injecting the second plastic material until it reaches the parting between the first common mold part and the second complementary mold part wherein step (i) comprises the step of (q) injecting the third plastic material until it reaches the parting between the second common mold part and the first complementary mold and wherein step (I) comprises the step of (r) injecting the fourth plastic material until it reaches the parting between the second common mold part and the second complementary mold 9. A method according Claim 7, wherein the first plastic material is same as the third plastic material and the second plastic material is the sam the fourth plastic material. 10. A method according to Claim 1, wherein step (g) further comp providing a said first complementary mold part that is dimensioned in relatio the first common mold part such that when so combined with the first com mold part to assemble the first mold cavity, portions of the first compleme mold part contact portions of the first common mold part to rigidly secure the common mold part in position in relation to the first complementary mold part order to impede movement of the first common mold part in relation to the fi complementary mold part during step (b). 11. A thin-walled, hollow, plastic product molded according to method of Claim 1. 12. A thin-walled, hollow, plastic product molded according to t method of Claim 3. 13. A thin-walled, hollow, plastic product molded according to t method of Claim 5. 14. A thin-walled, hollow, plastic product molded according to t method of Claim 10. 15. Apparatus for cyclic injection molding a thin-walled, hollow, plast product, comprising a first common mold part; a first complementary mold part; means for combining the first complimentary mold part with the fir common mold part to assemble a first mold cavity; means for injecting a first plastic material into the first mold cavity; means for solidifying the injected first plastic material to form a fir plastic material component; a second complementary mold part; means for combining the first common mold part with the seco complementary mold part to assemble a second mold cavity with the first plast material component attached to the first common mold part so that when t second mold cavity is assembled the first plastic material component is contain within the second mold cavity; means for injecting a second plastic material into the second mold cavi while the solidified first plastic material component is contained therein; means for solidifying the injected second plastic material so as to form second plastic material component that fuses with the first plastic materi component to produce a hollow plastic product; and means for shaping the first plastic material component such that wh the solidified first plastic material component is so contained in the second mo cavity the solidified first plastic material component provides one or mo stabilizing regions that rigidly secure the first common mold part in position relation to the second complementary mold part in order to impede movement the first common mold part in relation to the second complementary mold pa during injection of the second plastic material into the second mold cavity, thereby produce a thin-walled plastic product having controlled dimensions. 16. Apparatus according to Claim 15 for molding a product having a side wall including an approximately longitudinal strip, wherein the means for shaping the first plastic material component sha the first plastic material component to provide at least one said stabilizing regi that is transverse to a parting line between the first common mold part and t first complementary mold part, whereby said longitudinal strip is defined by s transverse stabilizing region. 17. Apparatus according to Claim 15 for molding a product having a side wall including an approximately longitudinal strip, wherein the means for shaping the first plastic material component sha the first plastic material component such that when the first plastic mater component is contained in the second mold cavity, the second mold cavity defin at least one unfilled cavity region that is transverse to a parting line between t first common mold part and the second complementary mold part, whereby sa longitudinal strip is defined by said unfilled transverse cavity region. 18. Apparatus according to Claim 15, for cyclic injection molding plurality of thin-walled, hollow, plastic products, further comprising a second common mold part; means for combining the first complimentary mold part with the seco common mold part to assemble a third mold cavity while the seco complementary mold part is combined with the first common mold part assemble the second mold cavity; means for injecting a third plastic material into the third mold cavity; means for solidifying the injected third plastic material to form a thi plastic material component- means for combining the second common mold part with the secon complementary mold part to assemble a fourth mold cavity while the fi complementary mold part is combined with the first common mold part assemble the first mold cavity, while retaining the third plastic material attached the second common mold part so that when the fourth moid cavity is assembl the third plastic material is contained within the fourth mold cavity; means for injecting a fourth plastic material into the fourth mold cav while the solidified third plastic material is contained therein; and means for solidifying the injected fourth plastic material so as to form fourth plastic material component that fuses with the third plastic material produce a second hollow plastic product; wherein -the means for solidifying the injected third plastic mater includes means for shaping the third plastic material component such that wh the third plastic material component is so contained in the fourth mold cavity t solidified third plastic material provides one or more stabilizing regions that rigi secure the second common mold part in position in relation to the fi complementary mold part in order to impede movement of the second comm mold part in relation to the first complementary mold part during injection of t fourth plastic material into the fourth moid cavity, to thereby produce a seco thin-walled plastic product having controlled dimensions. 19. Apparatus according to Claim 15, wherein the first complement mold part is dimensioned in relation to the first common mold part such that wh so combined with the first common mold part to assemble the first mold cavi portions of the first complementary mold part contact portions of the fi common mold part to rigidly secure the first common moid part in position relation to the first complementary nold part in order to impede movement of t first common mold part in relation to the first complementary mold part du injection of the first plastic material into the first mold cavity.

Inventors: SORENSEN JENS OLE, SORENSEN, JENS, OLE
Applicants: PRIMTEC
Application year: 1989
Main classification: F16L9
IPC codes: B29C45, B29L22, F16L11