Source: http://www.google.com/patents/US4467994?ie=ISO-8859-1
Timestamp: 2014-07-13 07:09:52
Document Index: 337026912

Matched Legal Cases: ['Application No. 8', 'art 101', 'art 102', 'art 102', 'art 101', 'art 102', 'art 101', 'art 102', 'art 201', 'art 202', 'art 202', 'art 201', 'art 202', 'art 201', 'art 204', 'art 218', 'art 201', 'art 202']

Patent US4467994 - Core centered mold for hollow stackable plastic products - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsA mold which comprises a number of circumferential throttles, at least partly located on the sides of the cavity and core parts respectively. The throttle distance is significantly shorter than the adjacent wall thickness, the pitch between throttles is such that stacking of the molded product is possible....http://www.google.com/patents/US4467994?utm_source=gb-gplus-sharePatent US4467994 - Core centered mold for hollow stackable plastic productsAdvanced Patent SearchPublication numberUS4467994 APublication typeGrantApplication numberUS 06/424,493Publication dateAug 28, 1984Filing dateSep 27, 1982Priority dateSep 27, 1982Fee statusLapsedPublication number06424493, 424493, US 4467994 A, US 4467994A, US-A-4467994, US4467994 A, US4467994AInventorsJens O. SorensenOriginal AssigneeSorensen Jens OleExport CitationBiBTeX, EndNote, RefManPatent Citations (8), Non-Patent Citations (2), Referenced by (19), Classifications (9), Legal Events (8) External Links: USPTO, USPTO Assignment, EspacenetCore centered mold for hollow stackable plastic productsUS 4467994 AAbstract A mold which comprises a number of circumferential throttles, at least partly located on the sides of the cavity and core parts respectively. The throttle distance is significantly shorter than the adjacent wall thickness, the pitch between throttles is such that stacking of the molded product is possible. The mold may comprise a number of feed channels leading from one throttle to the next throttle. The mold differs among other factors from the prior art by its short throttle distance, by its flow channels, by the throttles being located on the sides of the products, and the number of throttles being more than one. The throttles improve the rigidity of the molded thin-walled hollow product. When the molded product is a hand-held venting cup the throttles prevent buring of the fingers.
I claim: 1. A mold for injection molding of thin-walled, hollow, stackable plastic products, comprising a core part and a cavity part, where the relative reciprocal wall thickness of the molded product may be equalized by centering the core part in the cavity part during injection; the core part and the cavity part each having an axially extending circumferential recess in a circumferential shoulder, each said recess limiting an axially extending annular projection, corresponding such projections located on the sides of the core part and the cavity part respectively in combination defining a core-centering circumferential throttle.
2. A mold according to claim 1, wherein the throttle distance, which is the minimum distance from the annular projection of the core part to the corresponding annular projection of the cavity part, is shorter in the circumferential throttles which are placed nearer to the gate of the mold.
3. A mold according to claim 1, comprising a plurality of circumferential annular projections which are located on the side of the core and cavity parts respectively and which in combination provide a series of spaced self-centering circumferential throttles.
4. A mold according to claim 3, wherein the core part and cavity part in combination define a plurality of spaced feed channels extending between adjacent throttles, wherein the feed channel wall thickness is greater than the average wall thickness of the molded product.
5. A mold according to claim 4, wherein the feed channels uniformly consist of first and second serial parts that respectively radially project in opposite directions.
6. A mold according to claim 3, wherein the plurality of circumferential annular projections are separated by a distance which is approximately equal to two times the stacking height of the molded product.
7. A mold according to claim 6, wherein the core part and cavity part in combination define a plurality of spaced feed channels extending between adjacent throttles, wherein the feed channel wall thickness is greater than the average wall thickness of the molded product.
8. A mold according to claim 7, wherein the feed channels uniformly consist of first and second serial parts that respectively radially project in opposite directions.
FIELD OF INVENTION This invention generally relates to injection molding of hollow stackable plastic products and is particularly directed to centering the core of the mold. The core is the mold part which forms the interior of a concave or hollow molded product.
CROSS REFERENCE TO RELATED APPLICATION The invention is cross referenced to U.S. patent application Ser. No. 230,302, now U.S. Pat. No. 4,381,275, entitled STABILIZED CORE INJECTION MOLDING OF PLASTIC and United Kingdom Patent Application No. 8,221,909 entitled STABILIZED CORE INJECTION MOLDING, both applications which are different are by the inventor of the present application.
DISCUSSION OF PRIOR ART Heretofore, it has been a great problem to center the cores of molds used for injection molding of hollow stackable products of plastic with thin walls such as venting cups, yogurt containers, margarine containers and flower pots. In order to injection mold such products a very large injection pressure is necessary which causes the core part of the mold to move in relation to the cavity part of the mold, resulting in molded products which do not have even wall thickness.
SUMMARY OF THE INVENTION A mold for injection molding of thin-walled, hollow, stackable plastic products, comprising a core part and a cavity part, where the relative reciprocal wall thickness of the molded product may be equalized by centering the core part in the cavity part during injection.
The core part and the cavity part each have an axially extending circumferential recess in a circumferential shoulder. Each such recess limits an axially extending annular projection (ridge). Corresponding such annular projections located on the sides of the core part and the cavity part respectively in combination define a core-centering circumferential throttle. The minimum distance from the ridge of the core part to the corresponding ridge of the cavity part is called the throttle distance, when the core part is centered in the cavity part the throttle distance of the invention is significantly shorter than the adjacent wall thickness. For purposes of stacking the molded hollow products the angle of the pitch between the throttles is larger than arcus tangent of the basic horizontally measured wall thickness between the throttles divided by the stacking height of the molded product. The circumferential ridges on the side of the core and cavity part of the mold shape the circumferential ridges on the hollow stackable molded product, these ridges help to make the hollow product rigid. When the hollow product is, for example, a hand-held venting cup for hot drinks, the circumferential ridges provide a reduced area of contact between cup and fingers, resulting in less heat transfer and prevent possible burning of the fingers. There may conveniently be about ten to twenty circumferential ridges on the molded product, not all of these ridges need to be throttled with a throttle distance which is significantly shorter than the adjacent wall thickness, in one embodiment only every other circumferential ridge is throttled and the throttles which are nearer the apex of the hollow product have shorter throttle distances than the throttles which are closer to the open end of the hollow product.
In order to ease the filling of the cavity for injection molding of the thin-walled hollow product, a number of feed channels may be provided in the core and/or cavity part of the mold leading in a direction from the apex towards the open end of the hollow product. In order to get the best core centering, it is important that the throttle distance, particularly of the throttles near the apex end of the hollow product, is small in relation to the adjacent wall thickness where molten plastic is flowing during the filling. During the filling step, a large proportion of the injected plastic will flow in the above mentioned feed channels, and therefore the throttle distance in relation to the wall thickness of the feed channels is particularly small, thereby greatly improving the core centering process.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A illustrates a sectional view of a prior art mold for injection molding of hollow stackable plastic products.
DESCRIPTION OF THE ILLUSTRATED PRIOR ART FIG. 1A shows a prior art mold comprising a core part 101 and a cavity part 102 for injection molding a thin-walled, hollow, stackable plastic product. The cavity part 102 comprises a circumferential protuberance 103 which projects into a circumferential depression 104 of the apex of the core part 101. The protuberance 103 and the depression 104 in combination provide a circumferential throttle 112 with a throttle distance 105a and 105b which at an average corresponds to the wall thickness of the molded product to be produced. The mold 101, 102 comprises a runner 106 and a gate 107 which connects the runner 106 with the cavity 108. A partly filled product 109 is shown in the cavity 108. Near the open end of the cavity part 102 is a conical flange 110 which centers the core part 101 with the cavity part 102 of the mold when the mold is closed, and before plastic is injected.
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2A shows a mold of a preferred embodiment of the invention. The mold comprises a core part 201 and a cavity part 202 for injection molding a thin-walled, hollow, stackable plastic product. The side of the cavity part 202 comprises several circumferential ridges 203 and the side of the core part 201 comprises an equal number of circumferential ridges 204. Each ridge 203 of the cavity part 202 corresponds to a ridge 204 of the core part 201. Each corresponding pair of circumferential ridges provides a self-centering circumferential throttle 212 for the injection of plastic. The minimum distance from the ridge of the core part 204 to the corresponding ridge of the cavity part is called the throttle distance 205, seen best on FIG. 2B; the throttle distance 205 is significantly shorter than the adjacent wall thickness 213. The mold 201, 202 also comprise a runner 206 and a gate 207 which connects the runner 206 with the cavity 208. Near the open end of the cavity part 218 is a conical flange 210 which centers the core part 201 with the cavity part 202 of the mold, when the mold is closed and before plastic is injected. FIG. 2C shows a molded product of the mold of FIG. 2A, in order to ease the filling of the cavity 208 a number of feed channels 214 are provided in the cavity part of the mold, leading in a direction from the apex towards the open end of the molded product.
The four most important factors that the mold of the invention is successful in relation to the prior art are: (a) that the throttle distance is significantly shorter than the adjacent wall thickness of the molded product, particularly in the circumferential throttles which are nearest to the gate 207; (b) that because of the feed channels 214, the relation of the throttle distance to the adjacent wall thickness is further decreased; (c) the distance from the gate to each circumferential throttle, which is positioned on the side of the core and cavity parts respectively, is greater than in the prior art, making shortcuts to the flow of the molten plastic more difficult; and (d) there are a number of circumferential throttles instead of only one.
FIG. 3 shows a partial sectional view of two thin-walled, hollow, stackable plastic products in their stacked position, molded by a mold of the invention of a slightly modified embodiment than that depicted in FIGS. 2A, 2B and 2C. Shown is an upper product 301 and a lower product 302 separated by the stacking height 308. Shown is also a first circumferential throttle 303 and a second circumferential throttle 304 of the upper product 301. The throttle distance 309 which is the minimum distance from the ridge of the core part to the corresponding ridge of the cavity part, of the production mold of the product, is significantly shorter than the adjacent wall thickness 310. The angle of the pitch 305 from the first throttle 303 to the second throttle 304 is larger than arcus tangent 306 of the basic horizontally measured wall thickness 311 between the throttles 303 and 304 divided by the stacking height 308 of the molded product.
Between the throttles are a number of feed channels 307, 312 leading from throttle to throttle 304, 303, etc. A part of the feed channels 307 project towards the center axis of the molded product 301, 302 and another part of the feed channels 312 projects away from the center axis of the molded product 301, 302. The molded product 301, 302 and therefore also its production mold comprise a number of circumferential ridges which are separated by a distance which is equal to the stacking height 308 of the molded product 301, 302.
FIG. 4 shows a partial sectional view of two thin-walled, hollow, stackable plastic products in their stacked position molded by a mold of the invention of a slightly modified embodiment than that depicted in FIG. 2 or 3. Shown is an upper product 401 and a lower product 402 separated by the stacking height 408. Shown is also a first circumferential throttle 403 and a second circumferential throttle 404 of the upper product 401. The throttle distance 409, which is the minimum distance from the ridge of the core part to the corresponding ridge of the cavity part, of the production mold of the product, is significantly shorter than the adjacent wall thickness 410. The angle of the pitch 405 from the first throttle 403 to the second throttle 404 is larger than arcus tangent 406 of the basic horizontally measured wall thickness 411, between the throttles 403 and 404 divided by the stacking height 408 of the molded product. Between the throttles are a number of feed channels 407, 412 leading from throttle to throttle 404, 403, etc. A part of the feed channels 407 project towards the center axis of the molded product 401, 402 and another part of the feed channels 412 projects away from the center axis of the molded product 401, 402. The molded product 401, 402 and therefore also its production mold comprise a number of circumferential ridges which are separated by a distance which is approximately equal to two times the stacking height 408 of the molded product 401, 402.
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Giastrov, "Spritzgusswerkzeug fur Tablettenrohrchen".* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS4657141 *Jan 16, 1986Apr 14, 1987PrimtecHollow stackable plastic productsUS4789326 *Jan 28, 1987Dec 6, 1988Acebo CompanyStabilized-core injection molding of hollow thin-walled plastic productsUS4844405 *Jan 26, 1987Jul 4, 1989Acebo CompanyInjection molding of thin-walled plastic productsUS4935188 *Oct 26, 1988Jun 19, 1990Acebo CompanyStabilized-core injection molding of hollow thin-walled plastic productsUS4959005 *Feb 23, 1989Sep 25, 1990PrimtecSelf-aligning mold for injection molding of hollow plastic productsUS5008064 *Jun 5, 1989Apr 16, 1991PrimtecInjection-molding dimension-control and clamp-reductionUS5149482 *May 30, 1990Sep 22, 1992PrimtecControlling wall thickness, solidification of initially injected plastic to stabilizer core of moldUS5262112 *Jul 10, 1992Nov 16, 1993PrimtecDimension-control and clamp reduction during injection molding of laminated productsUS5624694 *Mar 18, 1996Apr 29, 1997Republic Tool & Mfg. Corp.Mold for making an internally threaded housingUS6599460Jul 3, 2000Jul 29, 2003Sorensen Research And Develpoment TrustPrevention of void-based-irregularity formation in thin-wall, injection-molded plastic productUS6841104Jan 15, 2002Jan 11, 2005Sorensen Research And Development TrustInjection molding alignment steering utilizing sequential throttles in base-wall-section flow guidesUS7175789Jan 7, 2005Feb 13, 2007Sorensen Research And Development TrustInjection molding utilizing base-wall-section flow guidesUS7402267Feb 12, 2007Jul 22, 2008Sorensen Research And Development TrustInjection molding utilizing base-wall-section flow guidesUS8691140 *Dec 20, 2011Apr 8, 2014Sa Des Eaux Minerales D'evian SaemeProcess for injection molding of thin-walled preformUS20120094043 *Dec 20, 2011Apr 19, 2012Sa Des Eaux Minerales D'evian SaemeBlow Molding DeviceUSRE33608 *Apr 12, 1989Jun 11, 1991PrimtecHollow stackable plastic productsEP1327511A1 *Jan 6, 2003Jul 16, 2003Universal VenturesInjection molding alignment steering utilizing sequential throttles in base-wall-section flow guidesWO1988005376A1 *Jan 18, 1988Jul 28, 1988Acebo CoStabilized-core injection molding of hollow thin-walled plastic productsWO1990009878A1 *Feb 20, 1990Sep 7, 1990Jens Ole SorensenSelf-aligning mold for injection molding of hollow plastic products* Cited by examinerClassifications U.S. Classification249/144, 425/577International ClassificationB65D1/26, B29C45/36Cooperative ClassificationB65D1/26, B29C2045/0051, B29C45/36European ClassificationB65D1/26, B29C45/36Legal EventsDateCodeEventDescriptionNov 5, 1996FPExpired due to failure to pay maintenance feeEffective date: 19960828Aug 25, 1996LAPSLapse for failure to pay maintenance feesApr 2, 1996REMIMaintenance fee reminder mailedMar 15, 1996ASAssignmentOwner name: SORENSEN,JENS OLE, CAYMAN ISLANDSFree format text: CHANGE OF ADDRESS;ASSIGNOR:SORENSEN, JENS OLE;REEL/FRAME:007833/0748Effective date: 19960228Oct 18, 1993ASAssignmentOwner name: PRIMTEC, CALIFORNIAFree format text: ACKNOWLEDGE OF TERMINATION OF LICENSED PATENT RIGHTS.;ASSIGNOR:ACEBO COMPANY;REEL/FRAME:006726/0448Effective date: 19930927Feb 26, 1988FPAYFee paymentYear of fee payment: 4Aug 17, 1987ASAssignmentOwner name: ACEBO COMPANY, 7910 IVANHOE AVE., STE. 203 LA JOLLFree format text: LICENSE;ASSIGNOR:PRIMTEC, A CORP. OF CA;REEL/FRAME:004742/0936Effective date: 19870812Owner name: ACEBO COMPANY,CALIFORNIAFree format text: LICENSE;ASSIGNOR:PRIMTEC, A CORP. OF CA;REEL/FRAME:4742/936Jun 17, 1985ASAssignmentOwner name: PRIMTEC, P.O. BOX 2403, RANCHO SANTA FE, CA 92067Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SORENSEN, JENS OLE;REEL/FRAME:004419/0453Effective date: 19850613Owner name: PRIMTEC, A CORP OF CA,CALIFORNIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SORENSEN, JENS OLE;REEL/FRAME:4419/453Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SORENSEN, JENS OLE;REEL/FRAME:004419/0453RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google