US3738418A - Backdraft rubber skin mold pattern - Google Patents

Backdraft rubber skin mold pattern Download PDF

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Publication number
US3738418A
US3738418A US00166201A US3738418DA US3738418A US 3738418 A US3738418 A US 3738418A US 00166201 A US00166201 A US 00166201A US 3738418D A US3738418D A US 3738418DA US 3738418 A US3738418 A US 3738418A
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US
United States
Prior art keywords
pattern
elastomer
backdraft
sleeve member
skin
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 - Lifetime
Application number
US00166201A
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English (en)
Inventor
G Harris
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Caterpillar Inc
Original Assignee
Caterpillar Tractor Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Caterpillar Tractor Co filed Critical Caterpillar Tractor Co
Application granted granted Critical
Publication of US3738418A publication Critical patent/US3738418A/en
Assigned to CATERPILLAR INC., A CORP. OF DE. reassignment CATERPILLAR INC., A CORP. OF DE. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: CATERPILLAR TRACTOR CO., A CORP. OF CALIF.
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
    • B22C7/005—Adjustable, sectional, expandable or flexible patterns
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S425/00—Plastic article or earthenware shaping or treating: apparatus
    • Y10S425/058—Undercut

Definitions

  • Patterns of the latter type perform satisfactorily when relatively small devices are being cast from the resulting sand mold, such as circular seal rings up to six inches in diameter.
  • these patterns along with the shell patterns referred to above, perform less satisfactorily in larger diameter casting, such as seal rings having diameters of ten inches and larger.
  • problems often develop in the larger sand molds formed with the prior art patterns, due to the increased mold size as the pattern is removed, since the metal surfaces provide no resiliency in the major portion of the mold.
  • the shell patterns are not satisfactory where it is desirable to maintain the ultimate casting in tolerances of i 0.030 inches in order to develop a serviceable casting as the thick rubber shell sections tend to be deformed by the compaction of sand around the pattern and fail to maintain the desired tolerances.
  • considerable machining is normally required on the casting cast from the shell type patterns to bring the final part into the necessary dimensional parameters on large circular devices.
  • backdraft refers to articles having hooked contours, overhanging or underlying sections and the like in the mold cavity, which projections prevent a pattern from being removed from the cured sand core without employing multiple parting planes in the mold or alternatively a deformable or melting pattern. Obviously since multiple parting planes often require subsequent machining of the cast part the elimination of such parting planes is highly desirable.
  • collateral object is to improve the economies in fabricating large one-piece sand molds for large circular castings.
  • a backdraft rubber skinned mold pattern including a circular metal sleeve forming the substantial portion of the mold pattern with the exception of backdraft portion, which metal sleeve is slightly undersize with reference to the size of the desired resulting mold cavity and an elastomer skin bonded to the surfaces of said metal portion, said elastomer skin including integral backdraft portions of the pattern whereby the resulting pattern can be removed from a cured sand mold without damaging the mold due to elastic deformations of the elastomer skin and backdraft portions of the pattern as it is removed.
  • the elastomer skin thickness, with the exception of the backdraft portions may vary from 0.010 to 0.050 inch and is preferably formed of heat resistant silicone rubber compounds since many of the sand molds are heat cured with the pattern therein.
  • FIG. 1 is a broken-away off-set section through a portion of the pattern attached to a sub-base and a mold table and surrounded by sand which is cured to form the mold cavity;
  • FIG. 2 is a cross-section through the rigid metal DESCRIPTION OF A PREFERRED EMBODIMENT
  • the complete pattern P is illustrated in a brokenaway section in FIG. 1 and includes three principal components, which are its sub-base 10, its circular metal sleeve member 11 and its elastomer skin 12 having an integral backdraft portions 13.
  • Centrally located on the bottom 14 of the sleeve member is a circular rib 15 that is received in a cooperating groove 16 in the sub-base, after the shaped elastomer skin has been conformed to the surfaces of the sleeve member.
  • the sub-base has a height equal to the depth of its recess 22 so the peripheral lip of the elastomer skin 12 extends across the joint between the sub-base and the table thereby providing a pattern protrusion from the table which is completely encased, with a seamless elastomer skin.
  • the elastomer skin 12 is bonded to the sleeve member 11 and in order to maintain the desired dimensional tolerances in the final casting obtained from the resulting mold cavity, the thickness of this skin should be in the range of 0.010 to 0.050 inch, with the exception of the small backdraft areas where the thickness is somewhat greater.
  • This thin skin has sufficient elasticity to allow the pattern to be extracted easily from the cured mold cavity while allowing the supporting sleeve member to support the skin in a manner adequate to preserve the desired tolerances; i 0.010 to 0.050 inch, depending on the diameter of the circular casting.
  • the circular or cylindrical sleeve member 11 which supports the thin skin 12 preferably has a slight outward taper in its inner circular wall 30 from its bottom 14 to its top rim 31. Its outer circular wall 32 has an appreciable inward taper from its bottom to the top rim, so the cross section of the sleeve member is somewhat triangular as can be seen in FIG. 2. These tapered surfaces along with the elasticity of the skin 12,. enables the pattern to be extracted easily from the cured sand mold cavity without damaging it.
  • the elastomer skin 12 is preferably formed of a silicon rubber, such as the type commercially available as Dow Corning Rubber No. 52, since it provides excellent heat resistant properties, good flexibility and can be easily bonded to the metal sleeve member 11.
  • the backdraft portion 13 of the pattern is formed completely of the elastomer since it must deform when the pattern is removed from the cured sand mold cavity. Normally this backdraft portion is relatively small in comparison to the complete pattern since a large, unsupported section of elastomer would not have sufficient rigidity to maintain desired dimensional tolerances when the sand is packed around the pattern.
  • top rim 31 of the sleeve member It is supported by the top rim 31 of the sleeve member and preferably tapers to a smaller cross section from the rim to its outer circular flaring periphery. Since the pattern is circular, this structure also tends to prevent the backdraft portion from deforming or distorting as the sand is packed around it.
  • a sand mixture S is packed around it and others attached in the table.
  • the sand mixture is of the curable kind, being either heat or gas cured so it will harden into a mold cavity M around each pattern on the table.
  • FIG. 5 the separation of the pattern from the mold cavity M is illustrated.
  • the elastomer skin on the walls 30 and 32 stretches, being pulled by the portion in the backdraft portion 13, which causes the skin to undergo a reduction in thickness which aids in separating the pattern from the mold cavity as the overall dimensions of the pattern decrease.
  • the backdraft portion elongates, reducing its cross section as it releases from the backdraft area, which allows this portion to also slip free without damaging the mold cavity.
  • the elastomer is bonded to the surfaces of the sleeve this action is limited.
  • the sand has an abrasive action on the elastomer skin and therefore the sleeve member and its skin have a limited service life while the sub-base can be used almost indefinitely. If the skin is not bonded to the sleeve member is separates therefrom when the pattern is removed from the mold cavity and does not readily re-conform to the surfaces of the sleeve member. Thus, tolerances would vary far outside those desired in such a situation.
  • An elastomer skinned pattern for forming circular one-piece molds having a backdraft portion comprismg:
  • a rigid sleeve member having a base portion and wall portions tapering from said base portion;
  • sub-base means attached to its base portion, said sub-base means operable to clamp the edges of the elastomer skin between said sub-base means and said base portion of the rigid sleeve member.
  • backdraft portion consists of a flange shaped portion of elastomer adjacent to the top of the rigid sleeve member.
  • the pattern defined in claim 4 including a mold table having an aperture for receiving the sub-base means whereby the elastomer skin on the base portion of the rigid sleeve member seats on the surface of said mold table whereby all surfaces of the pattern projecting into a cured mold cavity formed therewith will be elastomer coated.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
US00166201A 1971-07-26 1971-07-26 Backdraft rubber skin mold pattern Expired - Lifetime US3738418A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US16620171A 1971-07-26 1971-07-26

Publications (1)

Publication Number Publication Date
US3738418A true US3738418A (en) 1973-06-12

Family

ID=22602229

Family Applications (1)

Application Number Title Priority Date Filing Date
US00166201A Expired - Lifetime US3738418A (en) 1971-07-26 1971-07-26 Backdraft rubber skin mold pattern

Country Status (10)

Country Link
US (1) US3738418A (fr)
JP (1) JPS5821683Y2 (fr)
AU (1) AU468930B2 (fr)
BE (1) BE786750A (fr)
BR (1) BR7205011D0 (fr)
CA (1) CA977932A (fr)
DE (1) DE2236537A1 (fr)
FR (1) FR2147163B1 (fr)
GB (1) GB1362346A (fr)
IT (1) IT961658B (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4124676A (en) * 1976-09-29 1978-11-07 Crane Packing Co. Mechanical bond
EP0168839A2 (fr) * 1984-07-20 1986-01-22 Nippon Petrochemicals Co., Ltd. Composition pour matériel à mouler
US6193492B1 (en) * 1997-04-24 2001-02-27 COMPAGNIE GéNéRALE DES ETABLISSEMENTS MICHELIN - MICHELIN & CIE Element for molding a pattern in a tread
US6279222B1 (en) * 1995-08-03 2001-08-28 Federal-Mogul Technology Limited Manufacture of brake pads
US20070281137A1 (en) * 2006-06-01 2007-12-06 Kuolih Tsai Heat-transfer label assembly and apparatus for applying heat-transfer labels
US20140224957A1 (en) * 2010-03-17 2014-08-14 Mclaren Automotive Limited Single rigid tool part for moulding apparatus

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2940171C2 (de) * 1979-10-04 1984-04-05 Goetze Ag, 5093 Burscheid Modell für die Herstellung von Gießformen
DE3602049A1 (de) * 1986-01-24 1987-07-30 Goetze Ag Modell fuer die herstellung von giessformen
FR2633851B1 (fr) * 1988-07-07 1991-05-17 Mancelle Fonderie Plaque modele pour la realisation de moules destines a la fabrication par fonderie au sable de joints-glaces ou pieces similaires presentant un bourrelet en contre-depouille
GB2322585B (en) * 1995-11-07 1999-09-29 Firth Vickers Centrispinning L Making a metal shape by casting
GB9522741D0 (en) * 1995-11-07 1996-01-10 Firth Vickers Centrispinning L Making a metal shape by casting

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US61641A (en) * 1867-01-29 Improvement in elastic moulds
US2691418A (en) * 1951-06-23 1954-10-12 John A Connolly Combination packing cup and slips
FR1227020A (fr) * 1958-06-11 1960-08-18 Angus George Co Ltd Garniture de joint d'étanchéité
US3090996A (en) * 1959-12-17 1963-05-28 Chicago Rawhide Mfg Co Method and apparatus for forming seals
FR1474063A (fr) * 1966-01-29 1967-03-24 Centrifugation Soc Gen De Joint d'étanchéité pour canalisations
US3378888A (en) * 1965-10-19 1968-04-23 Holley Plastics Company Structure for vacuum forming of thermoplastic material on undercut flexible molds
US3552480A (en) * 1968-07-12 1971-01-05 Caterpillar Tractor Co Pattern for making a sand mold with a back draft

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US61641A (en) * 1867-01-29 Improvement in elastic moulds
US2691418A (en) * 1951-06-23 1954-10-12 John A Connolly Combination packing cup and slips
FR1227020A (fr) * 1958-06-11 1960-08-18 Angus George Co Ltd Garniture de joint d'étanchéité
US3090996A (en) * 1959-12-17 1963-05-28 Chicago Rawhide Mfg Co Method and apparatus for forming seals
US3378888A (en) * 1965-10-19 1968-04-23 Holley Plastics Company Structure for vacuum forming of thermoplastic material on undercut flexible molds
FR1474063A (fr) * 1966-01-29 1967-03-24 Centrifugation Soc Gen De Joint d'étanchéité pour canalisations
US3552480A (en) * 1968-07-12 1971-01-05 Caterpillar Tractor Co Pattern for making a sand mold with a back draft

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4124676A (en) * 1976-09-29 1978-11-07 Crane Packing Co. Mechanical bond
EP0168839A2 (fr) * 1984-07-20 1986-01-22 Nippon Petrochemicals Co., Ltd. Composition pour matériel à mouler
EP0168839A3 (en) * 1984-07-20 1987-01-07 Nippon Petrochemicals Co., Ltd. Modeling material composition
US6279222B1 (en) * 1995-08-03 2001-08-28 Federal-Mogul Technology Limited Manufacture of brake pads
US6193492B1 (en) * 1997-04-24 2001-02-27 COMPAGNIE GéNéRALE DES ETABLISSEMENTS MICHELIN - MICHELIN & CIE Element for molding a pattern in a tread
US20070281137A1 (en) * 2006-06-01 2007-12-06 Kuolih Tsai Heat-transfer label assembly and apparatus for applying heat-transfer labels
US8215943B2 (en) * 2006-06-01 2012-07-10 Avery Dennison Corporation Heat-transfer label assembly and apparatus for applying heat-transfer labels
US20140224957A1 (en) * 2010-03-17 2014-08-14 Mclaren Automotive Limited Single rigid tool part for moulding apparatus

Also Published As

Publication number Publication date
AU4481572A (en) 1974-01-24
GB1362346A (en) 1974-08-07
JPS5821683Y2 (ja) 1983-05-09
DE2236537A1 (de) 1973-02-08
JPS5653514U (fr) 1981-05-11
IT961658B (it) 1973-12-10
AU468930B2 (en) 1976-01-29
BE786750A (fr) 1973-01-26
CA977932A (en) 1975-11-18
BR7205011D0 (pt) 1973-06-12
FR2147163A1 (fr) 1973-03-09
FR2147163B1 (fr) 1977-07-22

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Legal Events

Date Code Title Description
AS Assignment

Owner name: CATERPILLAR INC., A CORP. OF DE.,ILLINOIS

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:CATERPILLAR TRACTOR CO., A CORP. OF CALIF.;REEL/FRAME:004669/0905

Effective date: 19860515

Owner name: CATERPILLAR INC., 100 N.E. ADAMS STREET, PEORIA, I

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:CATERPILLAR TRACTOR CO., A CORP. OF CALIF.;REEL/FRAME:004669/0905

Effective date: 19860515