GB2385552A - Casing structure for electrical material and production method thereof - Google Patents

Casing structure for electrical material and production method thereof Download PDF

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Publication number
GB2385552A
GB2385552A GB0204501A GB0204501A GB2385552A GB 2385552 A GB2385552 A GB 2385552A GB 0204501 A GB0204501 A GB 0204501A GB 0204501 A GB0204501 A GB 0204501A GB 2385552 A GB2385552 A GB 2385552A
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GB
United Kingdom
Prior art keywords
prime
prime material
shell
structure according
injected
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.)
Withdrawn
Application number
GB0204501A
Other versions
GB0204501D0 (en
Inventor
Andrea Percio
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.)
IND LOMBARDA MATERIALE ELECTTR
Original Assignee
IND LOMBARDA MATERIALE ELECTTR
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 IND LOMBARDA MATERIALE ELECTTR filed Critical IND LOMBARDA MATERIALE ELECTTR
Priority to GB0204501A priority Critical patent/GB2385552A/en
Priority to FR0203573A priority patent/FR2837663B3/en
Publication of GB0204501D0 publication Critical patent/GB0204501D0/en
Publication of GB2385552A publication Critical patent/GB2385552A/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K5/00—Casings, cabinets or drawers for electric apparatus
    • H05K5/0004—Casings, cabinets or drawers for electric apparatus comprising several parts forming a closed casing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/16—Making multilayered or multicoloured articles
    • B29C45/1642—Making multilayered or multicoloured articles having a "sandwich" structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/02—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles
    • B29C44/04—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles consisting of at least two parts of chemically or physically different materials, e.g. having different densities
    • B29C44/0407—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles consisting of at least two parts of chemically or physically different materials, e.g. having different densities by regulating the temperature of the mould or parts thereof, e.g. cold mould walls inhibiting foaming of an outer layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/02—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles
    • B29C44/04—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles consisting of at least two parts of chemically or physically different materials, e.g. having different densities
    • B29C44/0461—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles consisting of at least two parts of chemically or physically different materials, e.g. having different densities by having different chemical compositions in different places, e.g. having different concentrations of foaming agent, feeding one composition after the other
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/10—Polymers of propylene
    • B29K2023/12—PP, i.e. polypropylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/04—Condition, form or state of moulded material or of the material to be shaped cellular or porous
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/30—Vehicles, e.g. ships or aircraft, or body parts thereof
    • B29L2031/3055—Cars
    • B29L2031/3061—Number plates

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)

Abstract

A casing structure for an electrical item comprising an outer shell 5 made of prime thermoplastics with good mechanical and aesthetic characteristics and a core 6 encased within the shell 5 made of non-prime thermoplastics having a lower cost than the prime material. The prime material may be polybutene terephthalate and the non-prime material may be polypropylene. Also disclosed is a method for producing a casing structure for electrical material characterised in that it provides the co-injection moulding of a prime thermoplastics material and of a non-prime thermoplastics material, so that the prime material forms a shell 5 of the structure and the non-prime material forms a core 6 of the structure enclosed by the shell 5.

Description

<Desc/Clms Page number 1>
CASING STRUCTURE FOR ELECTRICAL MATERIAL AND PRODUCTION METHOD THEREOF DESCRIPTION The present invention refers to a casing structure for electrical material and to a production method of such a casing structure.
There currently exist on the market installable electrical devices (mainly wallmounted or cabinet installations) such as switches, fuse holders, sockets, pushbutton switches, and transformers that are mounted in various combinations inside casings which, according to current standards, must ensure a certain degree of protection from dust, water and impact.
Said casings have thus far been made both of metallic materials (assembled or diecast) and of moulded plastic materials (thermoplastic or thermosetting). In this latter case, it is easier to obtain the electrical insulation toward the outside of the electrical components contained inside the casing. In the case of thermoplastic materials, the manufacturers normally make these casings by moulding a resin which, for the specific application, provides the best compromise between cost and chemical and mechanical characteristics. For this purpose injection moulding machines (to create solid structures) or rotational or gas coinjection moulding machines (to create internally hollow structures) are used.
In the case of injection moulding there are limits to the thickness of the walls beyond which unacceptable shrinkage cavities and deformations occur. Moreover, the weight and, consequently, the cost of the manufactured article increase proportionally.
In order to provide the manufactured product with sufficient stiffness, therefore, it is necessary to provide suitable reinforcing ribs on the entire inner part of the structures and this considerable complicates their design and the creation of the relative moulds.
Rotational or gas coinjection moulding is convenient only for simple, large-sized structures, where it is possible to leave a hollow area inside the structure. In particular,
<Desc/Clms Page number 2>
rotational moulding is usually applied to moulds with one figure, with the need for further processing of the article to eliminate flashes and burrs. Consequently, the cost of the manufactured item is high.
Furthermore, rotational moulding is limited to the use of few materials such as polyethylene (in powder) and its derivatives.
Furthermore, gas coinjection moulding does not allow simultaneous moulding on moulds with many impressions because of the difficulty in getting the gas to reach the furthermost points of the mould and this results in high costs per product unit.
Furthermore, rotational moulding requires complex moulds that have flow channels for the gas and special machines provided with gas storage and distribution units.
In the case of casing structures for electrical material made by moulding thermosetting materials, good mechanical stiffness characteristics can be obtained (better, for the same thickness, than with thermoplastic materials). However, these structures have the disadvantage of being costly from the point of view of the material and transformation, as well as being difficult to recycle.
The object of the present invention is to eliminate the drawbacks of the aforementioned prior art by providing a casing structure for electrical material that is cheap and easy to make.
Another object of the present invention is to provide such a structure for the casing of electrical material that is compact and has a high degree of stiffness and considerable thickness.
Another object of the present invention is to provide such a structure for the casing of electrical material that is insulating, functional and has good aesthetic characteristics.
These objects are achieved according to the invention with the characteristics listed in casing structure according to claim I and in the method according to claim 9.
<Desc/Clms Page number 3>
Advantageous embodiments of the invention are apparent from the dependent claims.
The casing structure for electrical material according to the invention comprises an outer shell consisting of a prime thermoplastic resin having good mechanical and aesthetic characteristics and a core enclosed internally inside the shell and consisting of a low-cost non-prime thermoplastic resin.
The casing structure for electrical material is preferably made by injection moulding.
In particular, the structure is obtained by means of a single shot in an openable mould, by means of a thermoplastic resin moulding machine of the coinjection type. Initially the molten prime material, which adheres to the walls of the mould for forming the shell, is injected into the mould, and then the non-prime material is injected with a gaseous foaming agent added so that it can expand inside the shell so as to improve the compactness and avoid cavities.
The casing structure for electrical material according to the invention holds various advantages.
First of all, there is a considerable reduction in manufacturing costs compared with prior art structures made of a single material. In fact, for production of a piece a percentage of low-cost, non-prime material ranging between 40-60% can be used.
This allows the possibility of making very thick structures which therefore have good mechanical characteristics without having to provide reinforcing ribs and discharge gates for the shrinkage of the material. This leads to a further simplification in the design of the structure and of the moulds.
Moreover, the addition of a gaseous foaming agent to the non-prime material makes it possible to avoid the shrinkage cavities in the material that occur in structures according to the prior art obtained by injection of a single material.
The characteristics of resistance to chemical agents, hardness and finish of the surfaces are provided exclusively by the material used for the shell.
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Furthermore, the structures made in accordance with the invention contribute to a low environmental pollution thanks to the fact that the finished item can be recycled.
Further characteristics of the invention will be made clearer by the detailed description that follows, referring to a purely exemplary and therefore non-limiting embodiment thereof, illustrated in the appended drawings, in which: Figure 1 is a perspective view illustrating a casing for electrical material according to the invention; Figure 2 is a view of an enlarged detail of the casing of Figure 1, sectioned along the sectional planes indicated by the arrows II-II in Figure 1.
The casing structure for electrical equipment according to the invention will be described with the aid of the figures. The casing consists of basic housing 3 and a cover 4. A socket 1 and an ON/OFF switch 2 are provided on the outer wall of the cover 4. The socket 1 comprises a seat suited to receive a plug. The seat of the socket 1 can be covered by a cap 10 hinged to the outer wall of the cover 1.
The switch 2 is provided with a knob that can be turned by the user.
As shown in Figure 2, the base 3 is formed by an outer shell 5 and a core 6 contained inside the outer shell 5. The outer shell 5 is made of a prime material that gives good physical and aesthetic characteristics. By way of example, a plastic material such as PBTP (Polybutene Terephthalate) or (polyester) can be used as the prime material.
The inner core 6, on the other hand, is made of a non-prime material that has a lower cost than the prime material. By way of example, a low cost PP (polypropylene) can be sued as the non-prime material.
Clearly, the cover 4 also can be made by the same system, that is to say using a prime material as the shell and a non-prime material as the core.
<Desc/Clms Page number 5>
The single piece, such as the base 3 or the cover 4, which is needed for assembly of the casing is made by moulding inside a mould of the openable type provided with an impression with a shape corresponding to the manufactured piece. Using a thermoplastic moulding machine of the coinjection type, the prime material in the molten state and at high temperature is first injected into the mould. This prime material, destined to form the shell 5, is deposited on the outer wall of the mould.
After a few seconds, the non-prime material destined to form the core is injected. The non-prime material is injected at a lower temperature with respect to the prime material and with the addition of a gaseous foaming component.
The prime material of the shell 5 tends to set more rapidly on the outer surface thereof which is in contact with the cold walls of the mould. The inner part of the shell 5, which is warmer than the outer part, on the other hand, is perforated by the non-prime filling material that forms the core 6. In this manner, the prime material that forms the shell 5 is distributed according to a thin and substantially constant thickness indicated by"a"in Figure 2.
Once coinjection of the two materials has been completed, the piece is left in the mould for the time strictly necessary for cooling and then, by opening the mould, the finished piece can be extracted.
Numerous variations and modifications of detail within the reach of a person skilled in the art can be made to the present invention without departing from the scope of the invention as set forth by the appended claims.
In the claims reference numbers have been used purely for illustration/clarification but no scope limitation is intended thereby.

Claims (13)

  1. CLAIMS 1. A casing structure for electrical material comprising an outer shell (5) made of a prime thermoplastic material with good mechanical and aesthetic characteristics and a core (6), enclosed within said shell (5), made of a non-prime thermoplastic material having a lower cost than said prime material.
  2. 2. A structure according to claim 1, characterised in that said prime material consists
    of PBTP (Polybutene Terephthalate) or (polyester).
  3. 3. A structure according to claim I or 2, characterized in that said non-prime material is a low-cost non-prime material.
  4. 4. A structure according to any one of the preceding claims, characterised in that said non-prime material consists of PP (polypropylene).
  5. 5. A structure according to any one of the preceding claims, characterized in that said non-prime material has a gaseous foaming compound added.
  6. 6. A structure according to any one of the preceding claims, characterized in that it is obtained by coinjection moulding.
  7. 7. A structure according to claim 6, characterized in that it is obtained by means of a single shot in an openable mould, using a moulding machine for thermoplastic resins of the coinjection type.
  8. 8. A structure according to claim 6 or 7, characterized in that said prime material is injected at a higher melting temperature with respect to the melting temperature at which said non-prime material is injected.
  9. 9. A method for producing a casing structure for electrical material, characterized in that it provides the coinjection moulding of a prime thermoplastic material and of a non-prime thermoplastic material, so that said prime material forms a shell (5) of the
    <Desc/Clms Page number 7>
    structure and said non-prime material forms a core (6) of the structure enclosed by said shell (5).
  10. 10. A method according to claim 9, characterized in that said coinjection moulding consists of injecting firstly the prime material and then the non-prime material into an openable mould.
  11. 11. A method according to claim 9-or 10, characterized in that said prime material is injected at high temperature and said non-prime material is injected at a temperature lower than the injection temperature of the prime material.
  12. 12. A method according to any one of the claims from 9 to 11, characterized in that in the injection into the mould a gaseous foaming compound is added to said non prime material.
  13. 13. A casingstructLOBaosotdirgtDaryofclamsltD any of the clams 9 to 12 substantially as herein described with r ferEnoe to and as shcM-i in tsh aornparying dtdngs.
GB0204501A 2002-02-26 2002-02-26 Casing structure for electrical material and production method thereof Withdrawn GB2385552A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB0204501A GB2385552A (en) 2002-02-26 2002-02-26 Casing structure for electrical material and production method thereof
FR0203573A FR2837663B3 (en) 2002-02-26 2002-03-22 HOUSING STRUCTURE FOR ELECTRICAL EQUIPMENT AND METHOD FOR THE PRODUCTION THEREOF

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0204501A GB2385552A (en) 2002-02-26 2002-02-26 Casing structure for electrical material and production method thereof
FR0203573A FR2837663B3 (en) 2002-02-26 2002-03-22 HOUSING STRUCTURE FOR ELECTRICAL EQUIPMENT AND METHOD FOR THE PRODUCTION THEREOF

Publications (2)

Publication Number Publication Date
GB0204501D0 GB0204501D0 (en) 2002-04-10
GB2385552A true GB2385552A (en) 2003-08-27

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB0204501A Withdrawn GB2385552A (en) 2002-02-26 2002-02-26 Casing structure for electrical material and production method thereof

Country Status (2)

Country Link
FR (1) FR2837663B3 (en)
GB (1) GB2385552A (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0410708A2 (en) * 1989-07-26 1991-01-30 Polyplastics Co. Ltd. Surface-patterned polybutylene terephthalate resin molded articles and process for preparing such molded articles
US5474723A (en) * 1992-04-17 1995-12-12 Horikoshi; Maki Method of forming a shaped article of resin using cavity enlargement to induce foaming
US5645786A (en) * 1993-12-20 1997-07-08 Nissei Plastic Industrial Co., Ltd. Method of manufacturing a multilayer molding
EP0865894A1 (en) * 1995-11-02 1998-09-23 Honda Giken Kogyo Kabushiki Kaisha Process for producing sandwich-like synthetic resin molded article

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0410708A2 (en) * 1989-07-26 1991-01-30 Polyplastics Co. Ltd. Surface-patterned polybutylene terephthalate resin molded articles and process for preparing such molded articles
US5474723A (en) * 1992-04-17 1995-12-12 Horikoshi; Maki Method of forming a shaped article of resin using cavity enlargement to induce foaming
US5645786A (en) * 1993-12-20 1997-07-08 Nissei Plastic Industrial Co., Ltd. Method of manufacturing a multilayer molding
EP0865894A1 (en) * 1995-11-02 1998-09-23 Honda Giken Kogyo Kabushiki Kaisha Process for producing sandwich-like synthetic resin molded article

Also Published As

Publication number Publication date
GB0204501D0 (en) 2002-04-10
FR2837663A3 (en) 2003-09-26
FR2837663B3 (en) 2004-01-30

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)