PROCESS REDUCING OF MOULD CYCLE TIME

Abstract: A method is disclosed for the reduction of mould cycle time. A deflatable member is positioned flush with the surface of a mould in an opening defined downwardly therein. Prior to flow of a resin or other hardenable liquid within the mould, the deflatable member is deflated so as to define a resin flow channel across selected portions of the mould surface. Prior to hardening of the hardenable liquid within the mould, the deflatable member is inflated so as to become flush with the surface of the mould so as to yield an article of manufacture having a relatively planar surface.

Description: The invention relates to a process for reducing cycle time in the moulding of fibre-reinforced thermoset articles. Various moulding methods are discussed in chapters 4 and 5 of the book entitled, Handbook of Reinforced Plastics , Society of the Plastics Industry, Inc., copyright 1964, published by the Reinhold Publishing Corporation, Library of Congress Catalog Card No. 64-15205. Whenever contact moulding, bag moulding, or similar procedures are being used to fabricate articles of manufacture formed from fiber-reinforced resins, single die moulds will typically be required. To economically produce these articles using any type of mould, the rate of article production must be maximized to allow the quick recovery of the capital costs associated with the purchase of the mould. The mould cycle time must be minimized. In the case of an article that incorporates fibers or filaments within the hardenable liquid, it is desirable to quickly wet these materials. In the case of an article that comprises a fibre reinforcement matrix and it is desirable to have the thermosetting resin composition flood all internal voids and interstices within the matrix quickly such that the curing time of the resin may be kept to a minimum. A process therefore needs to be developed that permits rapid flow of the resin into the mould and which permits rapid wetting of these fibers. The present invention provides a process for moulding a thermoset article of manufacture including the steps of: providing a mould having a surface, said mould surface having at least one opening defined downwardly therein, locating deflatable member means within said opening, said deflatable member means having a fluid chamber containing fluid defined in the interior thereof, said deflatable member means having a moveable wall formed between a portion of said fluid chamber and a moveable wall surface of said deflatable member means located adjacent said mould surface, placing fluid movement means in communication with said fluid chamber, inserting a preshaped member of fibre-reinforcement matrix in the mould, closing the mould, removing fluid from said fluid chamber so as to move said moveable wall inward a selected distance relative to said mould surface, thereby defining a channel to permit flow of thermosetting resin composition through said channel into the mould, adding fluid to said fluid chamber to move said moveable wall surface flush with said mould surface, retaining said thermosetting composition in said mould for a sufficient period to dimensionally stabilize the article of manufacture, opening the mould and removing said article from said mould. These and other features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to Figures 1 and 2. Fig. 1 is a schematic representation in a side view in partial cross section showing the deflatable member positioned within an opening defined downwardly within the mould section. Fig. 2 is a schematic representation in a side view and partial cross section of the same deflatable member now defining a channel for flow of a hardenable liquid beneath the preshaped filament member. In Figs. 1 and 2, 11 and 12 represent the upper and lower parts of a mould, respectively, 13 represents a preshaped member of reinforcement fibre matrix. The mould can be seen to comprise a surface 14 having at least one opening 15 defined downwardly therein. Surface 14 of the mould preferably coincides with the lower surface of the preshaped member of fibre-reinforcement matrix. Opening 15 can be embodied in the form of a longitudinal groove which in the figures is shown in cross-section. More than one groove can be present in the lower mould surface. The mould is referred to in a generic sense wherein it is understood to include structures associated with vacuum bag moulding, pressure bag moulding, autoclave moulding, vacuum injection moulding, cable clave moulding or the like. Deflatable member means 16 are located within the opening 15, which comprise in a preferred embodiment a tube fitting in the groove and having a rectangular cross-section made from rubber or other elastomeric material. A fluid chamber 17 is provided in the interior of member 16. The deflatable member means 16 can be seen to have a moveable wall 18 formed between a portion of the fluid chamber 17 and wall surface 19 which is located adjacent to mould surface 14. Fluid chamber 17 is connected via tube 20 to a pump (not shown) and reservoir (not shown), that are used to supply and remove fluid to and from deflatable member means 16. Fig. 1 shows the fluid chamber 17 in the inflated state, when fluid 22 is supplied, the moveable wall 18 is caused to move upward to a position wherein surface 19 is flush with surface 14 of the mould. Withdrawal of fluid from chamber 17 causes wall 18 to move downward to the deflated position shown in Fig. 2, thus defining a channel 21 through which thermosetting resin can be supplied to the interior of the mould to fill the internal voids of the fibre matrix. Suitable thermosetting resins are selected from polyester resins, phenolic resins, vinyl ester resins, epoxy resins, polyurethane resins, polyisocyanurate resins, urethane resins, and polyamide resins. The fibre matrix can comprise fiberglass cloth, tape, woven roving, or any other collection of fibers, cloth, or material used to reinforce the resin. Preshaping to closely fit the internal volume of the mould can be carried out by any known method, compressing being preferred. The flow of the thermosetting resin beneath certain portions of the filament matrix accelerates supply of resin to the filament matrix thereby allowing shortening the moulding cycle time. Wall 18 may be formed by a co-extrusion technique wherein a material such as nylon may be used to form the outer surface of the wall, to allow the wall to easily part from the finished article. In addition, mould-release agents may be employed. The moulding may comprise at least one thermosetting resin injection port typically located centrally within the lower surface area of the mould. To allow the rapid supply of the resin over a relative large portion of the lower mould surface area the deflatable member means 16 preferably extend radially outward away from that port. It should be well recognized that many other flow patterns may be used to accomplish the same mechanical result. For example, the deflatable member means may comprise a series of linear parallel fluid chambers, evenly spread over the lower surface area of the mould.

Claims: A process for moulding a thermoset article of manufacture including the steps of: providing a mould having a surface, said mould surface having at least one opening defined downwardly therein, locating deflatable member means within said opening, said deflatable member means having a fluid chamber containing fluid defined in the interior thereof, said deflatable member means having a moveable wall formed between a portion of said fluid chamber and a moveable wall surface of said deflatable member means located adjacent said mould surface, placing fluid movement means in communication with said fluid chamber, inserting a preshaped member of fibre-reinforcement matrix in the mould, closing the mould, removing fluid from said fluid chamber so as to move said moveable wall inward a selected distance relative to said mould surface, thereby defining a channel to permit flow of thermosetting resin composition through said channel into the mould, adding fluid to said fluid chamber to move said moveable wall surface flush with said mould surface, retaining said thermosetting composition in said mould for a sufficient period to dimensionally stabilize the article of manufacture, opening the mould, and removing said article from said mould.

Inventors: EPEL, JOSEPH NORMAN
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1988
Main classification: B29C67
IPC codes: B29C70, B29C31, B29K105, B29C33, B29C43, B29K101