CA1196164A - Method of duplicating shapes and finishes - Google Patents
Method of duplicating shapes and finishesInfo
- Publication number
- CA1196164A CA1196164A CA000419549A CA419549A CA1196164A CA 1196164 A CA1196164 A CA 1196164A CA 000419549 A CA000419549 A CA 000419549A CA 419549 A CA419549 A CA 419549A CA 1196164 A CA1196164 A CA 1196164A
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- Prior art keywords
- mold
- sheet
- plastic material
- producing
- separation sheet
- Prior art date
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Abstract
ABSTRACT OF THE DISCLOSURE
A method of duplicating shapes comprises producing a master pattern, producing a sand mold negative of the master pattern, casting a replica of the master pattern from the sand mold, producing a vacuum forming pattern, producing a vacuum formed separation sheet on the vacuum forming pattern, covering surfaces of the replica with the vacuum formed separation sheet, packing a plastic material against the vacuum formed separation sheet in the mold, and causing the plastic mix to harden. The method is useful for the manufacture of an automobile steering wheel.
A method of duplicating shapes comprises producing a master pattern, producing a sand mold negative of the master pattern, casting a replica of the master pattern from the sand mold, producing a vacuum forming pattern, producing a vacuum formed separation sheet on the vacuum forming pattern, covering surfaces of the replica with the vacuum formed separation sheet, packing a plastic material against the vacuum formed separation sheet in the mold, and causing the plastic mix to harden. The method is useful for the manufacture of an automobile steering wheel.
Description
The present invention relates -to methods of repro-ducing complicated shapes and finishes; and more particularly, is useful in the art of filamen-t winding, and the molding of plastic materials generally.
Filamen-t winding of complicated shap.es is carried out by deposi-ting a strand under tension in the cavi-ties of a mold designed to hold the deposi.ted strand in the desired shape. The strand is wrapped around and around the same cavities of the mold until the desired thickness of strand is deposited. Usually the strand is completely wetted ou-t with a binder before it is wound into the cavi-ties of the mold, but the invention is not limited in this respect. As the binder wetted strand is pulled down in-to the mold, excess binder exudes into the spaces between the wrappings of the strand and also into contact with the surEaces of the mold. The binder i.s then caused to harden in the mold to bind the fibers to-gether and hold them in the desired shape. Binders will usually sti.ck to the surface of the moldl and the art has long mi-ti-cJated the mold sticking problem by incorporating mold release agen-ts into the binders. The mold release agents appear to function by rising to -the external surfaces of the binder as it agglomerates, to -thereby coat the surface of the mold.
Another problem which occurs in the filament winding art, is that it is impractical for the mos-t part, to incor-porate fibers crosswise -to the windings for the purpose of binding the windings -together. Separation of the windings therefore is prevented almost entirely by the binder, and its attachment to -the filamen-ts of the strand. For this reason, the strength of the binder may be rnore critical in filament wound parts than in other types of fiber reinforced par-ts.
. ;~
A still fur-ther problem exists in the process of filamen-t winding in that the molds are-usually ro-tated while a "finger" positions the strand in the proper location rela-tive to the mold's cavities. The tension on the binder wetted strand, in conjunction with the ro-ta-tion of the mold, causes excess binder to flow out of the mold cavities over other sur-faces of the mo]d, including its separating and clamping sur~
faces. This excess resin has proved costly -to remove.
Also in the commercial production of fi]ament wound parts, a considerable time period is spent winding the strand in~o the cavities oE the mold. To achieve volume production, therefore, it is necessary to have a large number of such molds, not only for the winding operation, but to support the wound part during the time that the binder is hardening. In the case where the binder is a thermoset-ting resin, the mold with a wound par~ therein is moved to an oven and heated to approxi-ma-te:Ly 350F -to cause the binder to harden. During this time, anothex mold will have been placed in the winding machine and another part formed. The molds are usually made of a cast aluminum, or o-ther me-tal, to wi-thstand the temperature and handling; and the cost of produciny and machining the com~
plicated shapes of -the mold is appreciable.
The present invention provides a method of duplicating shapes which comprises producing a master pa-ttern, producing a sand mold negative of the mas-ter pattern, casting a replica of the master pattern from the sand mold, producing a vacuum form-ing pat-tern from the replica, producing a vacuum formed separa-tion sheet o~ the vacuum forming pa-ttern, coveriny surfaces of the replica with the vacuum formed separation sheet, packing a plastic material against -the vacuum formed separa-tion sheet ~ 3~ ~ ~
in the moldr and causing the plas-tic ma-terial to harden.
The present invention fur-ther provides a me-thod of producing paralle] fiber reinforced ar-tlcles which comprises producing a vacuum formed separa-tion sheet -to fi-t a mold for confining the parallel fibers, fitting the separa-tion sheet over surfaces of the mold, placing binder incorporated parallelly laid fibers over -the surfaces of the separation shee-t and hardening the binder against the separation shee-t.
The present invention still further provides a method of producing a molded part from a plastic ma-terial which re-quires a mold release to prevent -the parts from sticking -to -the mold, which comprises vacuum :Eorming a sheet of mold release agent to conform to the shape of the mold, fitting -the vacuum :Eormed sheet onto molding surfaces of the mold, molding the plastic material agains-t the separation sheet, and hardening -the plastic ma-terial.
Figure 1 is a block diagram indicating s-teps involved :in a preferred embodiment of -the inven-tion for producing and using filament winding molds.
Figure 2 is an exploded view showing a release sheet of the present inven-tion as positioned for ma-ting with a mo].d constructed according to other aspects of the present invention.
Figure 3 is an oblique exploded view of the assembly made as indicated by Figure 2 with cer-tain hold down segmen-ts positioned for installation to comple-te -the filament winding mold.
Figuxe 4 i~s a fragmentary sec-tional view taken ap-pro~imately on the line 4 - 4 of Figure 3.
Figure 5 is a fragmen-tary sectional view taken ap-proximate].y on the line 5 ~ 5 of Figure 3.
.. 3 _ According -to some of the aspects of the pr~sent in-vention, the mold release ayent in the binder can be reduced or eliminated by placing a sheet of mold release agent over the surfaces of the mold. The sheet of release agent may be formed in situ, but this is time consuming, and is preferably made of a sufficiently thick sheet that it can be formed in a separate operation and be placed in -the mold. It has been found that not only is this practical, but that it can be made to provide a smoother finish -to the par-ts made therefrom than is obtained if the parts are made directly on the mold sur-faces. This in turn can be utilized to effect certain economies in the making of molds, provided steps are taken to correc-t for size variations that occur during the process of making the sheet of release agent. Certain broad steps in ~pplicant's process are depicted diagramatically in Figure 1, and some of these steps, are shown more fully in Figures 2 through 5 as they relate to the filament winding of a s-teering wheel for an automotive vehicle.
In -the em~odimen-t of Applicant's process depic-ted in Figure 1, polypropylene is used as the mold release separa-tion sheet, and cast aluminum is used ~or the production molds.
Polypropylene shee-ts after being removed from the vacuum forming mold shrink by 0.020 inch per inch. Cast aluminum, during cooling from the molten casting temperature, shrinks approxi-mately one eighth of an inch per foot. The precise amount of shrinkage of the cast aluminum can be con-trolled -to some degree by the particular alloy used, -the CaStincJ temperature, etc. The polypropylene sheet -tha-t is to be used is 0.025 inch thick, and it has been determined -that it stretches to a -thick-ness of 0.015 inch during vacuum ~orming. With -this in mind, D, ,~ ~
~9~
a master pattern 10 is made of wood, or other easily shaped material, with i-ts filament winding cavities being 0.030 inch wider, and 0.015 inch deeper than the part desired. The overall dimensions of the filament winding cavl-ties are 1/~
inch per foot ]arger than the desired production part, since it turns out that the polypropylene shrinks, or can be made to shrink by this amount.
A vacuum forming mold 12 can be made in any one of a number of differen-t ways. In the process diagrammed in Figure 1, an accurate sand mold 14 is made of the mas-ter pat-tern 10. Vacuum tubes are laid into the cavity of a sand mo:Ld, and the cavity is filled with a me-tal powder - filled plastic which has a very small shrinkage during solidification. ~he vacuum forming mold 12 will only be very slightly smaller than the master pattern 10. Holes are drilled from -the appropriate surfaces of the plastic to the vacuum tubes, and the surfaces are given a high polish. The vacuum forming mold 12 is then utilized to form separation sheets 24.
The master pattern 10 is also used -to make the pro-duction molds. In the process diagrammed, an accura-te sand mold 16 is first made and molten aluminum is cast -therein to produce a cast aluminum pattern 18. A~ter cooling the aluminum pattern 1~ will have shrunk by approxima-tely 1/2 of -the desired amount necessary to match -the shrinkage of polypropylene. The aluminum pattern 18 is checked for surface and size. If ac-ceptable, an accurate sand mold 20 is made from it, and cast aluminum is poured into it - this time under condition~ in-tended to give the remaining necessary shrinkage -to end up with a mold on which a vacuum forming separation sheet will fit. For any large scale production of filament wound parts~
-- 5 ~
``7 a large number of productlon molds 22 are necessary; and i-t is intended that a large number of sand molds 20 will firs-t be made from the cast metal pattern 18, and tha-t the necessary productionmolds 22 will be ob-tained therefrom.
An advan-tage of Applicant's me-thod of moldin~ is that the separation sheeks 24 will retain the high finish of the vacuum forming mold 12. The metal production molds 22, when removed from the sand molds 20, will have surface irregu-larities arising fxom the depressions be-tween sand grains.
It has been found that in filamen-t winding, the separation sheets 24 are not forced down into these surface irregularities and -therefore, no expensive machining or polishing operation need be performed on the production molds 22.
Filament wound parts are made by placing a vacuum formed separation sheet 2~ on a production mold 22 as shown at 26 and installing the necessary filament re-taining plates on the top side edge of the mold's filamen-t retaining cavi-ties.
A strand we-tted out wi-th catalyzed polyester prepolymer, or other sui-table prepolymer, is positioned by a finger opposite -the mold's filament re-taining cavities; and ei-ther the mold is rotated to lay -the strand into the cavlty, or the finger is moved to lay the s-trand into -the cavity. This operation is depicted at 28 and is explained in de-tail in prior art patents so that it need not be explained further here, excep-t as such a process coacts with Applicant's shee-t of mold release
Filamen-t winding of complicated shap.es is carried out by deposi-ting a strand under tension in the cavi-ties of a mold designed to hold the deposi.ted strand in the desired shape. The strand is wrapped around and around the same cavities of the mold until the desired thickness of strand is deposited. Usually the strand is completely wetted ou-t with a binder before it is wound into the cavi-ties of the mold, but the invention is not limited in this respect. As the binder wetted strand is pulled down in-to the mold, excess binder exudes into the spaces between the wrappings of the strand and also into contact with the surEaces of the mold. The binder i.s then caused to harden in the mold to bind the fibers to-gether and hold them in the desired shape. Binders will usually sti.ck to the surface of the moldl and the art has long mi-ti-cJated the mold sticking problem by incorporating mold release agen-ts into the binders. The mold release agents appear to function by rising to -the external surfaces of the binder as it agglomerates, to -thereby coat the surface of the mold.
Another problem which occurs in the filament winding art, is that it is impractical for the mos-t part, to incor-porate fibers crosswise -to the windings for the purpose of binding the windings -together. Separation of the windings therefore is prevented almost entirely by the binder, and its attachment to -the filamen-ts of the strand. For this reason, the strength of the binder may be rnore critical in filament wound parts than in other types of fiber reinforced par-ts.
. ;~
A still fur-ther problem exists in the process of filamen-t winding in that the molds are-usually ro-tated while a "finger" positions the strand in the proper location rela-tive to the mold's cavities. The tension on the binder wetted strand, in conjunction with the ro-ta-tion of the mold, causes excess binder to flow out of the mold cavities over other sur-faces of the mo]d, including its separating and clamping sur~
faces. This excess resin has proved costly -to remove.
Also in the commercial production of fi]ament wound parts, a considerable time period is spent winding the strand in~o the cavities oE the mold. To achieve volume production, therefore, it is necessary to have a large number of such molds, not only for the winding operation, but to support the wound part during the time that the binder is hardening. In the case where the binder is a thermoset-ting resin, the mold with a wound par~ therein is moved to an oven and heated to approxi-ma-te:Ly 350F -to cause the binder to harden. During this time, anothex mold will have been placed in the winding machine and another part formed. The molds are usually made of a cast aluminum, or o-ther me-tal, to wi-thstand the temperature and handling; and the cost of produciny and machining the com~
plicated shapes of -the mold is appreciable.
The present invention provides a method of duplicating shapes which comprises producing a master pa-ttern, producing a sand mold negative of the mas-ter pattern, casting a replica of the master pattern from the sand mold, producing a vacuum form-ing pat-tern from the replica, producing a vacuum formed separa-tion sheet o~ the vacuum forming pa-ttern, coveriny surfaces of the replica with the vacuum formed separation sheet, packing a plastic material against -the vacuum formed separa-tion sheet ~ 3~ ~ ~
in the moldr and causing the plas-tic ma-terial to harden.
The present invention fur-ther provides a me-thod of producing paralle] fiber reinforced ar-tlcles which comprises producing a vacuum formed separa-tion sheet -to fi-t a mold for confining the parallel fibers, fitting the separa-tion sheet over surfaces of the mold, placing binder incorporated parallelly laid fibers over -the surfaces of the separation shee-t and hardening the binder against the separation shee-t.
The present invention still further provides a method of producing a molded part from a plastic ma-terial which re-quires a mold release to prevent -the parts from sticking -to -the mold, which comprises vacuum :Eorming a sheet of mold release agent to conform to the shape of the mold, fitting -the vacuum :Eormed sheet onto molding surfaces of the mold, molding the plastic material agains-t the separation sheet, and hardening -the plastic ma-terial.
Figure 1 is a block diagram indicating s-teps involved :in a preferred embodiment of -the inven-tion for producing and using filament winding molds.
Figure 2 is an exploded view showing a release sheet of the present inven-tion as positioned for ma-ting with a mo].d constructed according to other aspects of the present invention.
Figure 3 is an oblique exploded view of the assembly made as indicated by Figure 2 with cer-tain hold down segmen-ts positioned for installation to comple-te -the filament winding mold.
Figuxe 4 i~s a fragmentary sec-tional view taken ap-pro~imately on the line 4 - 4 of Figure 3.
Figure 5 is a fragmen-tary sectional view taken ap-proximate].y on the line 5 ~ 5 of Figure 3.
.. 3 _ According -to some of the aspects of the pr~sent in-vention, the mold release ayent in the binder can be reduced or eliminated by placing a sheet of mold release agent over the surfaces of the mold. The sheet of release agent may be formed in situ, but this is time consuming, and is preferably made of a sufficiently thick sheet that it can be formed in a separate operation and be placed in -the mold. It has been found that not only is this practical, but that it can be made to provide a smoother finish -to the par-ts made therefrom than is obtained if the parts are made directly on the mold sur-faces. This in turn can be utilized to effect certain economies in the making of molds, provided steps are taken to correc-t for size variations that occur during the process of making the sheet of release agent. Certain broad steps in ~pplicant's process are depicted diagramatically in Figure 1, and some of these steps, are shown more fully in Figures 2 through 5 as they relate to the filament winding of a s-teering wheel for an automotive vehicle.
In -the em~odimen-t of Applicant's process depic-ted in Figure 1, polypropylene is used as the mold release separa-tion sheet, and cast aluminum is used ~or the production molds.
Polypropylene shee-ts after being removed from the vacuum forming mold shrink by 0.020 inch per inch. Cast aluminum, during cooling from the molten casting temperature, shrinks approxi-mately one eighth of an inch per foot. The precise amount of shrinkage of the cast aluminum can be con-trolled -to some degree by the particular alloy used, -the CaStincJ temperature, etc. The polypropylene sheet -tha-t is to be used is 0.025 inch thick, and it has been determined -that it stretches to a -thick-ness of 0.015 inch during vacuum ~orming. With -this in mind, D, ,~ ~
~9~
a master pattern 10 is made of wood, or other easily shaped material, with i-ts filament winding cavities being 0.030 inch wider, and 0.015 inch deeper than the part desired. The overall dimensions of the filament winding cavl-ties are 1/~
inch per foot ]arger than the desired production part, since it turns out that the polypropylene shrinks, or can be made to shrink by this amount.
A vacuum forming mold 12 can be made in any one of a number of differen-t ways. In the process diagrammed in Figure 1, an accurate sand mold 14 is made of the mas-ter pat-tern 10. Vacuum tubes are laid into the cavity of a sand mo:Ld, and the cavity is filled with a me-tal powder - filled plastic which has a very small shrinkage during solidification. ~he vacuum forming mold 12 will only be very slightly smaller than the master pattern 10. Holes are drilled from -the appropriate surfaces of the plastic to the vacuum tubes, and the surfaces are given a high polish. The vacuum forming mold 12 is then utilized to form separation sheets 24.
The master pattern 10 is also used -to make the pro-duction molds. In the process diagrammed, an accura-te sand mold 16 is first made and molten aluminum is cast -therein to produce a cast aluminum pattern 18. A~ter cooling the aluminum pattern 1~ will have shrunk by approxima-tely 1/2 of -the desired amount necessary to match -the shrinkage of polypropylene. The aluminum pattern 18 is checked for surface and size. If ac-ceptable, an accurate sand mold 20 is made from it, and cast aluminum is poured into it - this time under condition~ in-tended to give the remaining necessary shrinkage -to end up with a mold on which a vacuum forming separation sheet will fit. For any large scale production of filament wound parts~
-- 5 ~
``7 a large number of productlon molds 22 are necessary; and i-t is intended that a large number of sand molds 20 will firs-t be made from the cast metal pattern 18, and tha-t the necessary productionmolds 22 will be ob-tained therefrom.
An advan-tage of Applicant's me-thod of moldin~ is that the separation sheeks 24 will retain the high finish of the vacuum forming mold 12. The metal production molds 22, when removed from the sand molds 20, will have surface irregu-larities arising fxom the depressions be-tween sand grains.
It has been found that in filamen-t winding, the separation sheets 24 are not forced down into these surface irregularities and -therefore, no expensive machining or polishing operation need be performed on the production molds 22.
Filament wound parts are made by placing a vacuum formed separation sheet 2~ on a production mold 22 as shown at 26 and installing the necessary filament re-taining plates on the top side edge of the mold's filamen-t retaining cavi-ties.
A strand we-tted out wi-th catalyzed polyester prepolymer, or other sui-table prepolymer, is positioned by a finger opposite -the mold's filament re-taining cavities; and ei-ther the mold is rotated to lay -the strand into the cavlty, or the finger is moved to lay the s-trand into -the cavity. This operation is depicted at 28 and is explained in de-tail in prior art patents so that it need not be explained further here, excep-t as such a process coacts with Applicant's shee-t of mold release
2~. The mold with the filament windings therein is placed in an oven at approxima-tely 350F to harden the binder as depicted at 30; and thereaf-ter, the mold is opened to release the production part~ as deplc-ted at 32.
Referrlng to Figures 2 through 5, -there is shown therein a sheet of mold release and ma-tching mold parts for producing a filarnent wound steering wheel of an automotive vehicle. Figure 2 shows a filament winding mold 22 having an annular rim forming groove 34 opening ou-twardly oE its periphery. Four pairs of vertlcal guides 36, 38, 40 and 42 extend generally radially from a hub supporting pLa-teau 44 to the rim groove 34 to provide respective channels for build-ing the rim supporting arms of -the steering wheel. Six studs 46 project vertically from -the base of the mold just radially inwardly oE the groove 34 for retaining the segmental plates 48, 50, 52 and 54 which provide the top wall of the rim groove 34. Suitable wing nu-ts 56 are -threaded on-to the studs 46 to clamp the segmental cover plates 48 through 54 in place. Be-foxe the segmental cover plates are slipped into position, however, a mold release sheet 24 of vacuum formed polypropylene is slipped down over the studs 46 and ma-ted with the surfaces of the mold 22. Referring to sections 4 and 5, it will be seen that the release sheet 24 is retained by the segmental cover plates 48 through 54, and that it lays down tightly on the surfaces of the mold 22. Also it will be seen that the release sheet 24 has a peripheral resin retaining groove 34 to catch any excess resin that may be thrown ~rom the rim groove 34 during rotation of the mold 22.
The resin retaining groove 58 is made durlny vacuum forming by an appropriate por-tion of the vacuum forming mold 12 which was added to the basic shape produced by -the sand mold 14 from which the vacuum forming mold 12 was made. A
peripheral space 60 exists between the surface of the mold ~2 and the segmental cover pla-tes 48 through 54 to receive resin soaked glass s-trand from a finger, not shown, positioned ~, ' outwardly of the resin re-taining groove 58 as the mold 22 is rotated. Rotation of the mold 2~ stops at appropriate times wlth the finger, not shown, opposite the ~roove between one of the pairs of vertical guides 36 through ~2, following which the finger moves inwardly be-tween the guides to the center.
Upon reaching the center, -the mold 22 rotates again -to wrap the strand around a hub, not shown, following which -the finger moves radially outwardly between ano-ther pair of vertical guides. This operation is continued until -the rim cavity 34 and the arm cavities between the vertical guide plates, shown in sections 4 and 5 are filled with strand. The mold with the resin saturated wound filaments is then moved to an oven held at approximately 350F for twenty minutes to harden the binder into the steering wheel armature 32. The hot mold is opened, and the release sheet with the armature 32 is pulled from the surfaces of the heated mold 22, and is allowed to cool.
While Figure l depic-ts a preerred sequence oE steps which will produce release sheets that mate wi-th a produc-tion mold, other sequences of steps can be utilized. For those ~0 instances where the release sheets shrink at twice the rate of the production molds during cooling, it is possible to build a to-tally independent vacuum fo~ming mold from scratch which is appropriately larger than the master pattern from which the production molds are made. In the case of polypropylene release sheets, the vacuum forming mold could be made lar~er than the desired production part by l/4 inch per foot, while the pattern for the produc-tion molds is only made l/8 inch per foot larger than the desired production part. Instead of laying each ou-t independently of each other, however, a production mold can be cut into a number of pieces, say 16, which are then arranged with spaces in between to give overall dimensions whlch are 1/4 inch per foot larger than the pro~
duction mold. The pieces can be doweled together using powdered metal filled plastic to fill the spaces, and the mold cavlties can then be worked -to the proper dimensions.
In ano-ther embodiment of the invention, the material from which the vacuum sheets are made is compounded or selected to have the same shrinkage as has the material from which the produc-tion mold is made. In this case, only one master pa-ttern need be made, and the production molds can be made from sand molds whose cavities are made by the master pattern itse]f.
While the invention has been described as having special advantages in making filament winding molds, it is not so limited ~ nor is it limited to the use of a single re-lease sheet.
We do no-t wish to be limited to the particular embodi-ments shown or described, and it is our intention hereby to cover all novel adaptations, modifications, and arranyements thereof which come within the practice of those skilled in the art -to which the invention relates and which fall within the purview of the following claims.
Referrlng to Figures 2 through 5, -there is shown therein a sheet of mold release and ma-tching mold parts for producing a filarnent wound steering wheel of an automotive vehicle. Figure 2 shows a filament winding mold 22 having an annular rim forming groove 34 opening ou-twardly oE its periphery. Four pairs of vertlcal guides 36, 38, 40 and 42 extend generally radially from a hub supporting pLa-teau 44 to the rim groove 34 to provide respective channels for build-ing the rim supporting arms of -the steering wheel. Six studs 46 project vertically from -the base of the mold just radially inwardly oE the groove 34 for retaining the segmental plates 48, 50, 52 and 54 which provide the top wall of the rim groove 34. Suitable wing nu-ts 56 are -threaded on-to the studs 46 to clamp the segmental cover plates 48 through 54 in place. Be-foxe the segmental cover plates are slipped into position, however, a mold release sheet 24 of vacuum formed polypropylene is slipped down over the studs 46 and ma-ted with the surfaces of the mold 22. Referring to sections 4 and 5, it will be seen that the release sheet 24 is retained by the segmental cover plates 48 through 54, and that it lays down tightly on the surfaces of the mold 22. Also it will be seen that the release sheet 24 has a peripheral resin retaining groove 34 to catch any excess resin that may be thrown ~rom the rim groove 34 during rotation of the mold 22.
The resin retaining groove 58 is made durlny vacuum forming by an appropriate por-tion of the vacuum forming mold 12 which was added to the basic shape produced by -the sand mold 14 from which the vacuum forming mold 12 was made. A
peripheral space 60 exists between the surface of the mold ~2 and the segmental cover pla-tes 48 through 54 to receive resin soaked glass s-trand from a finger, not shown, positioned ~, ' outwardly of the resin re-taining groove 58 as the mold 22 is rotated. Rotation of the mold 2~ stops at appropriate times wlth the finger, not shown, opposite the ~roove between one of the pairs of vertical guides 36 through ~2, following which the finger moves inwardly be-tween the guides to the center.
Upon reaching the center, -the mold 22 rotates again -to wrap the strand around a hub, not shown, following which -the finger moves radially outwardly between ano-ther pair of vertical guides. This operation is continued until -the rim cavity 34 and the arm cavities between the vertical guide plates, shown in sections 4 and 5 are filled with strand. The mold with the resin saturated wound filaments is then moved to an oven held at approximately 350F for twenty minutes to harden the binder into the steering wheel armature 32. The hot mold is opened, and the release sheet with the armature 32 is pulled from the surfaces of the heated mold 22, and is allowed to cool.
While Figure l depic-ts a preerred sequence oE steps which will produce release sheets that mate wi-th a produc-tion mold, other sequences of steps can be utilized. For those ~0 instances where the release sheets shrink at twice the rate of the production molds during cooling, it is possible to build a to-tally independent vacuum fo~ming mold from scratch which is appropriately larger than the master pattern from which the production molds are made. In the case of polypropylene release sheets, the vacuum forming mold could be made lar~er than the desired production part by l/4 inch per foot, while the pattern for the produc-tion molds is only made l/8 inch per foot larger than the desired production part. Instead of laying each ou-t independently of each other, however, a production mold can be cut into a number of pieces, say 16, which are then arranged with spaces in between to give overall dimensions whlch are 1/4 inch per foot larger than the pro~
duction mold. The pieces can be doweled together using powdered metal filled plastic to fill the spaces, and the mold cavlties can then be worked -to the proper dimensions.
In ano-ther embodiment of the invention, the material from which the vacuum sheets are made is compounded or selected to have the same shrinkage as has the material from which the produc-tion mold is made. In this case, only one master pa-ttern need be made, and the production molds can be made from sand molds whose cavities are made by the master pattern itse]f.
While the invention has been described as having special advantages in making filament winding molds, it is not so limited ~ nor is it limited to the use of a single re-lease sheet.
We do no-t wish to be limited to the particular embodi-ments shown or described, and it is our intention hereby to cover all novel adaptations, modifications, and arranyements thereof which come within the practice of those skilled in the art -to which the invention relates and which fall within the purview of the following claims.
3~
Claims (11)
1. A method of duplicating shapes comprising: pro-ducing a master pattern, producing a sand mold negative of the master pattern, casting a replica of the master pattern from the sand mold, producing a vacuum forming pattern from the replica, producing a vacuum formed separation sheet on the vacuum forming pattern, covering surfaces of the replica with said vacuum formed separation sheet, packing a plastic material against the vacuum formed separation sheet in said mold, and causing said plastic material to harden.
2. The method of claim 1 wherein: said plastic material has a thermosetting binder, and said plastic material is hardened against said vacuum formed sheet when covering the surfaces of said replica.
3. The method of claim 2 wherein said plastic material is a polyester resin containing a fiber reinforcement.
4. The method of claim 3 wherein said fiber rein-forcement comprises long lengths of parallel side by side fibers.
5. The method of claim 2, 3 or 4 wherein said separa-tion sheet is caused to have smoother surfaces than said replica on which it is placed and the hardened plastic mix is caused to take on the smooth surface of said separation sheet.
6. A method of producing parallel fiber reinforced articles comprising: producing a vacuum formed separation sheet to fit a mold for confining the parallel fibers, fitting the separation sheet over surfaces of the mold, placing binder incorporated parallelly laid fibers over the surfaces of the separation sheet and hardening the binder against the separa-tion sheet.
7. The method of claim 6 wherein said parallel fibers are wound in situ over the surfaces of said vacuum formed sepa-ration sheet.
8. The method of claim 6 or 7 wherein said binder is a thermosetting binder.
9. A method of producing a molded part from a plastic material which requires a mold release to prevent the parts from sticking to the mold, comprising: vacuum forming a sheet of mold release agent to conform to the shape of the mold, fitting the vacuum formed sheet onto molding surfaces of the mold, molding the plastic material against the separation sheet, and hardening the plastic material.
10. The method of claim 9 wherein the plastic material contains a thermosetting binder.
11. The method of claim 9 or 10 wherein the separa-tion sheet is caused to have a finish that is smoother than the finish of the molding surface of the mold, and the molded part is caused to have the finish of the separation sheet.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000419549A CA1196164A (en) | 1983-01-17 | 1983-01-17 | Method of duplicating shapes and finishes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000419549A CA1196164A (en) | 1983-01-17 | 1983-01-17 | Method of duplicating shapes and finishes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1196164A true CA1196164A (en) | 1985-11-05 |
Family
ID=4124347
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000419549A Expired CA1196164A (en) | 1983-01-17 | 1983-01-17 | Method of duplicating shapes and finishes |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1196164A (en) |
-
1983
- 1983-01-17 CA CA000419549A patent/CA1196164A/en not_active Expired
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