WO2011073852A1 - Core for moulds for casting - Google Patents

Core for moulds for casting Download PDF

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Publication number
WO2011073852A1
WO2011073852A1 PCT/IB2010/055627 IB2010055627W WO2011073852A1 WO 2011073852 A1 WO2011073852 A1 WO 2011073852A1 IB 2010055627 W IB2010055627 W IB 2010055627W WO 2011073852 A1 WO2011073852 A1 WO 2011073852A1
Authority
WO
WIPO (PCT)
Prior art keywords
core
cavity
protruding portion
product
imprint
Prior art date
Application number
PCT/IB2010/055627
Other languages
French (fr)
Inventor
Marco Guidetti
Original Assignee
Casappa S.P.A.
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 Casappa S.P.A. filed Critical Casappa S.P.A.
Publication of WO2011073852A1 publication Critical patent/WO2011073852A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/10—Cores; Manufacture or installation of cores
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/22—Moulds for peculiarly-shaped castings
    • B22C9/24—Moulds for peculiarly-shaped castings for hollow articles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
    • F01C21/00—Component parts, details or accessories not provided for in groups F01C1/00 - F01C20/00
    • F01C21/10—Outer members for co-operation with rotary pistons; Casings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2/00—Rotary-piston machines or pumps
    • F04C2/08—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C2/12—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C2/14—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2230/00—Manufacture
    • F04C2230/20—Manufacture essentially without removing material
    • F04C2230/21—Manufacture essentially without removing material by casting
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2240/00—Components
    • F04C2240/30—Casings or housings

Definitions

  • the object of the present invention is a core for casting moulds.
  • the present invention relates to a core for casting moulds for the production of gear pumps.
  • gear pumps such as pumps for fluids (generally hydraulic oil) for example, have a containment body having a substantially box-shaped conformation and forming a housing seat for the respective gears.
  • the containment body is generally made by means of casting in suitable moulds inside of which a core forming the internal seat of the containment body is housed.
  • the core is suitably made in accordance with the size and the shape of the cited internal seat of the containment body.
  • a core having a cylindrical conformation is made to predispose the seat adapted to receive the respective gear wheels.
  • the molten material normally consisting of molten cast iron
  • the core is made of sand and it is moulded owing to a chemical binder, capable of conferring mouldability to the core itself.
  • the pour of molten material burns off the chemical binder and the core then tends to crumble.
  • the mould is broken in order to remove the rough body, whereas the internal core can be removed readily, being easily crumbled.
  • a subsequent cleaning step allows for elimination also of the particles of sand left on the rough piece.
  • the body thus obtained undergoes further finishing steps, such as a milling procedure on sharp corners present in the internal wall of the housing seat for the cited gears.
  • machining by milling is particularly complicated to carry out, given the position of the sharp corners inside the seat. Consequently, it proves to be difficult and arduous to insert the milling machine inside the seat of the body to reach the corners to be smoothed.
  • the technical task underlying the present invention is to propose a core for casting moulds that is capable of simplifying the processes for producing the containment body.
  • one object of the present invention is to make available a core for casting moulds that is capable of producing finished containment bodies for hydraulic pumps, that is to say, containment bodies that do not require milling procedures to smooth the sharp corners where mechanical stresses are concentrated.
  • FIG. 1 is a perspective view of a core for casting moulds in accordance with the present invention.
  • FIG. 2 is a perspective view of a product that is obtainable by means of casting in moulds equipped with the core illustrated in figure 1;
  • FIG. 3 is a perspective and longitudinal section view of the product illustrated in figure 2.
  • a core for casting moulds is indicated as a whole by the number 1.
  • the core 1 object of the present invention, is advantageously utilized for the production of mechanical parts constituting gear pumps for fluids.
  • a core 1 for casting moulds adapted for the production of a product 4 that constitutes a gear containment body (commonly referred to as a pump body) , intended to be utilized in the field of pumps for fluids.
  • the core 1 comprises a body 2 preferably having a substantially bilobate conformation and forming an external surface 3.
  • the body 2 is predisposed to be inserted inside a respective mould, which is not illustrated in detail as it is of a known type, in such a manner as to define the internal shape of a product 4 obtained by means of a casting process.
  • the body 2 inserted in the respective mould forms a hollow space inside of which the molten material is poured, such as molten cast iron for example in the case of gear pumps for fluids.
  • the mould forms the external structure 5 of the product 4 (figure 2), whereas the core 1 forms an internal cavity 6 in the product 4 itself (figure 3).
  • the shape of the external surface 3 of the body 2 forms an imprint 7 inside the cavity 6 of the product 4, that is to say the form of the internal surface of the cited cavity 6.
  • the external surface 3 of the body 2 is shaped in accordance with the dimensions and the use of the cited product 4, intended to contain respective gears inside the cavity 6.
  • the external surface 3 of the body 2 is completely rounded and does not have any portions with sharp corners.
  • the protruding portion 8 determines the formation of a groove inside the cavity, having a rounded profile, that is to say without any sharp corners .
  • the cavity 6 is intended to receive the gears of the pump, whereas the groove formed by the protruding portion 8 is intended to be passed through by the fluid.
  • the protruding portion 8 has a substantially toroidal conformation extending around a typically vertical, longitudinal axis of the body 2.
  • the protruding portion 8 has, in cross-section, an arc-shaped conformation of an annulus in order to form the particular arcuate conformation at the undercut 9.
  • the arcuate undercut 9 of the product 4 obtained from the protruding portion 8 substantially extends along a circumferential path inside the cavity 6.
  • the object of the present invention is also a method for the production of a containment body for gears of a gear pump for fluids. Such method comprises the following steps :
  • Said core 1 comprises an external surface 3 forming an imprint of said cavity 6 and having at least one protruding portion 8.
  • the protruding portion 8 has a rounded profile, forms an arcuate undercut in said imprint and is suitably without any sharp corners.
  • the undercut 8 is obtained in an intersecting zone between :
  • the side surface 10 delimits two main lobes 13, 14 of the housing compartment 11.
  • the housing compartment 11 coinciding with/being comprised in said cavity 6.
  • the product 4 does not have to undergo machining by milling for the purpose of smoothing sharp corners, as only arcuate and rounded portions are obtained inside the cavity 6. In other words, no portions are produced with sharp corners that could cause mechanical stresses and cracks with consequent breakage, typically due to fatigue, of the product 4 during its operation.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Developing Agents For Electrophotography (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Macromonomer-Based Addition Polymer (AREA)
  • Rotary Pumps (AREA)
  • Details And Applications Of Rotary Liquid Pumps (AREA)

Abstract

Core for casting moulds, comprising: a body (2) insertable inside a mould to form a cavity (6) for a product (4) obtained by means of casting inside said mould, said body (2) having an external surface (3) forming an imprint (7) of said cavity (6) for the product (4); the external surface (3) has at least one protruding portion (8) having a rounded profile and forming an arcuate undercut (9) in said imprint (7).

Description

CORE FOR MOULDS FOR CASTING
TECHNICAL FIELD AND BACKGROUND ART.
The object of the present invention is a core for casting moulds.
In particular, the present invention relates to a core for casting moulds for the production of gear pumps.
As is known gear pumps, such as pumps for fluids (generally hydraulic oil) for example, have a containment body having a substantially box-shaped conformation and forming a housing seat for the respective gears.
The containment body is generally made by means of casting in suitable moulds inside of which a core forming the internal seat of the containment body is housed.
The core is suitably made in accordance with the size and the shape of the cited internal seat of the containment body. For example, a core having a cylindrical conformation is made to predispose the seat adapted to receive the respective gear wheels.
Once the mould and the respective core have been produced, the molten material, normally consisting of molten cast iron, is poured. In particular, the core is made of sand and it is moulded owing to a chemical binder, capable of conferring mouldability to the core itself. The pour of molten material burns off the chemical binder and the core then tends to crumble.
At the end of the pour, the mould is broken in order to remove the rough body, whereas the internal core can be removed readily, being easily crumbled. A subsequent cleaning step allows for elimination also of the particles of sand left on the rough piece.
Next, the body thus obtained undergoes further finishing steps, such as a milling procedure on sharp corners present in the internal wall of the housing seat for the cited gears.
In fact, stresses that can create cracks are concentrated on the sharp corners obtained inside the housing seat of the body. Consequently, in order to prevent any breakage due to fatigue of the body of the pump, such sharp corners are smoothed by means of milling procedures. Breakage due to fatigue occurs as a result of repeated pumping cycles of the fluid owing to the rotation of the gears positioned in said housing seat .
Such a procedure does, however, cause important inconveniences in the production cycle of the body of the pump .
In fact, machining by milling is particularly complicated to carry out, given the position of the sharp corners inside the seat. Consequently, it proves to be difficult and arduous to insert the milling machine inside the seat of the body to reach the corners to be smoothed.
It should also be considered that the milling procedure following casting, extends the production times for the pump body and thus negatively affects the production times and costs of the finished piece.
In this context, the technical task underlying the present invention is to propose a core for casting moulds that is capable of simplifying the processes for producing the containment body.
DISCLOSURE OF INVENTION.
In particular, one object of the present invention is to make available a core for casting moulds that is capable of producing finished containment bodies for hydraulic pumps, that is to say, containment bodies that do not require milling procedures to smooth the sharp corners where mechanical stresses are concentrated.
The technical task defined and the objects specified are substantially achieved by a core for casting moulds, comprising the technical features set forth in one or more of the accompanying claims.
BRIEF DESCRIPTION OF DRAWINGS.
Further features and advantages of the present invention will become more clear from the indicative description, and thus non-limiting, of a preferred but not exclusive embodiment of a core for casting moulds, as illustrated in the accompanying drawings, in which:
- Figure 1 is a perspective view of a core for casting moulds in accordance with the present invention;
- Figure 2 is a perspective view of a product that is obtainable by means of casting in moulds equipped with the core illustrated in figure 1; and
- Figure 3 is a perspective and longitudinal section view of the product illustrated in figure 2.
BEST MODE FOR CARRYING OUT THE INVENTION.
With reference to the accompanying figures, a core for casting moulds is indicated as a whole by the number 1. In particular, the core 1, object of the present invention, is advantageously utilized for the production of mechanical parts constituting gear pumps for fluids. Hereinafter in this document, by way of example only, reference will be made to a core 1 for casting moulds, adapted for the production of a product 4 that constitutes a gear containment body (commonly referred to as a pump body) , intended to be utilized in the field of pumps for fluids.
With particular reference to figure 1, the core 1 comprises a body 2 preferably having a substantially bilobate conformation and forming an external surface 3. In particular, the body 2 is predisposed to be inserted inside a respective mould, which is not illustrated in detail as it is of a known type, in such a manner as to define the internal shape of a product 4 obtained by means of a casting process.
In greater detail the body 2, inserted in the respective mould, forms a hollow space inside of which the molten material is poured, such as molten cast iron for example in the case of gear pumps for fluids.
In this manner, the mould forms the external structure 5 of the product 4 (figure 2), whereas the core 1 forms an internal cavity 6 in the product 4 itself (figure 3). In this situation, the shape of the external surface 3 of the body 2 forms an imprint 7 inside the cavity 6 of the product 4, that is to say the form of the internal surface of the cited cavity 6.
For this reason, the external surface 3 of the body 2 is shaped in accordance with the dimensions and the use of the cited product 4, intended to contain respective gears inside the cavity 6.
As better illustrated in figure 1, it should be noted that the external surface 3 of the body 2 is completely rounded and does not have any portions with sharp corners. In fact, on the external surface 3 there is at least one protruding portion 8 having a rounded profile to form an arcuate undercut 9 in the imprint 7.
In other words, the protruding portion 8 determines the formation of a groove inside the cavity, having a rounded profile, that is to say without any sharp corners .
The cavity 6 is intended to receive the gears of the pump, whereas the groove formed by the protruding portion 8 is intended to be passed through by the fluid. In particular, the protruding portion 8 has a substantially toroidal conformation extending around a typically vertical, longitudinal axis of the body 2.
Again, the protruding portion 8 has, in cross-section, an arc-shaped conformation of an annulus in order to form the particular arcuate conformation at the undercut 9.
With particular reference to the sectional view in figure 3, it should be noted that the arcuate undercut 9 of the product 4 obtained from the protruding portion 8 substantially extends along a circumferential path inside the cavity 6.
The object of the present invention is also a method for the production of a containment body for gears of a gear pump for fluids. Such method comprises the following steps :
- predisposing a pair of half-moulds that are mutually couplable to form a chamber for accommodating a pour of molten material;
- inserting a core 1 in said chamber to form a cavity 6 in the gear containment body obtained from said pour of molten material. Said core 1 comprises an external surface 3 forming an imprint of said cavity 6 and having at least one protruding portion 8. The protruding portion 8 has a rounded profile, forms an arcuate undercut in said imprint and is suitably without any sharp corners.
The undercut 8 is obtained in an intersecting zone between :
- a side surface 10 that is part of said imprint and that contributes to delimiting a compartment 11 for housing said gears;
- a base 12 that is part of said imprint and that contributes to delimiting the compartment 11 for housing said gears, said base 12 extending transversely to said side surface 10.
The side surface 10 delimits two main lobes 13, 14 of the housing compartment 11. The housing compartment 11 coinciding with/being comprised in said cavity 6.
Advantageously, the product 4 does not have to undergo machining by milling for the purpose of smoothing sharp corners, as only arcuate and rounded portions are obtained inside the cavity 6. In other words, no portions are produced with sharp corners that could cause mechanical stresses and cracks with consequent breakage, typically due to fatigue, of the product 4 during its operation.
The processes of production of the product 4 are thus markedly simplified. Advantageously, therefore, the production times for the pump body are reduced, as are the production times and costs of the finished product.

Claims

1. A core for casting moulds for the production of gear pumps, comprising a body (2) insertable inside a mould to form a cavity (6) for a product (4) obtained by means of casting inside said mould, said body (2) having an external surface (3) forming an imprint (7) of said cavity (6) for the product (4), said product (4) constituting a containment body for the gears and intended to be utilized in the field of pumps for fluids;
characterized in that said external surface (3) has at least one protruding portion (8) having a rounded profile and forming an arcuate undercut (9) in said imprint (7), said protruding portion (8) having no sharp corners.
2. The core according to any one of the preceding claims, characterized in that said protruding portion (8) has a cross section in the shape of an arc of an annulus .
3. The core according to any one of the preceding claims, characterized in that said body (2) has a substantially bilobate conformation, said external surface (3) of the body (2) being completely rounded.
4. The core according to any one of the preceding claims, characterized in that said protruding portion (8) extends around an axis of longitudinal extension of said body (2) to create the undercut (9) around a longitudinal axis of said cavity (6) for the product (2) .
5. The core according to any one of the preceding claims, characterized in that the protruding portion (8) determines the formation of a groove inside the cavity (6), with said groove having a rounded profile without any sharp corners; said cavity being intended to receive the gears of the pump, whereas the groove formed by the protruding portion (8) is intended to be passed through by the fluid.
6. A casting mould for the production of hollow products, comprising at least one pair of half-moulds, mutually couplable to form a chamber for accommodating a pour of molten material, characterized in that it further comprises a core (1) according to one or more of the preceding claims, insertable into said chamber to form a cavity (6) for a product (4) obtained from said pour of molten material, said product (4) constituting a gear containment body intended to be utilized in the field of pumps for fluids.
7. A method for the production of a gear containment body of a gear pump for fluids comprising the following steps: - predisposing a pair of half-moulds, mutually couplable to form a chamber for accommodating a pour of molten material ;
- inserting a core (1) in said chamber to form a cavity (6) in the gear containment body obtained from said pour of molten material, said core (1) comprising an external surface (3) forming an imprint of said cavity (6) and having at least one protruding portion (8), said protruding portion (8) having a rounded profile, forming an arcuate undercut in said imprint and being without any sharp corners.
8. The method according to claim 7, characterized in that said undercut (8) is obtained in an intersecting zone between:
- a side surface (10) that is part of said imprint and that contributes to delimiting a compartment (11) for housing said gears;
- a base (12) that is part of said imprint and that contributes to delimiting the compartment (11) for housing said gears, said base (12) extending transversely to said side surface (10).
9. The method according to claim 8, characterized in that said side surface (10) delimits two main lobes (13, 14) of the housing compartment (11).
PCT/IB2010/055627 2009-12-14 2010-12-07 Core for moulds for casting WO2011073852A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITPR2009A000102A IT1397561B1 (en) 2009-12-14 2009-12-14 SOUL FOR MERGER MOLDS.
ITPR2009A000102 2009-12-14

Publications (1)

Publication Number Publication Date
WO2011073852A1 true WO2011073852A1 (en) 2011-06-23

Family

ID=42101528

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2010/055627 WO2011073852A1 (en) 2009-12-14 2010-12-07 Core for moulds for casting

Country Status (2)

Country Link
IT (1) IT1397561B1 (en)
WO (1) WO2011073852A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100852489B1 (en) * 2007-03-22 2008-08-18 동남정밀 주식회사 Die-casting mold
JP2009057902A (en) * 2007-08-31 2009-03-19 Jtekt Corp Manufacturing method of motor-driven oil pump and pump housing

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1769455A (en) * 1929-08-28 1930-07-01 Doehler Die Casting Co Core for undercut cup-shaped articles
JPH0263642A (en) * 1988-08-30 1990-03-02 Aisin Seiki Co Ltd Manufacture of piston for internal combustion engine
JPH10196553A (en) * 1997-01-10 1998-07-31 Nippon Spindle Mfg Co Ltd Gear pump or hydraulic motor, and manufacture of pump body
AU756027B2 (en) * 1997-10-20 2003-01-02 Chipless Metals Llc. Making precision castings using thixotropic materials
DE10306122B3 (en) * 2003-02-14 2004-11-11 Eisengießerei Baumgarte GmbH Production of a metal cast housing comprises molding a sand core into a piece to be used as a detachable part, and pulling back a slide whilst the detachable part remains in its position in the undercut and removing the sand core
JP2009221900A (en) * 2008-03-14 2009-10-01 Hitachi Ltd Internal combustion engine piston and method for manufacturing the same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100852489B1 (en) * 2007-03-22 2008-08-18 동남정밀 주식회사 Die-casting mold
JP2009057902A (en) * 2007-08-31 2009-03-19 Jtekt Corp Manufacturing method of motor-driven oil pump and pump housing

Also Published As

Publication number Publication date
ITPR20090102A1 (en) 2011-06-15
IT1397561B1 (en) 2013-01-16

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