Abstract: A method for manufacturing laminated skis wherein the molds in which the skis are built are vacuum wrapped with a plastic film prior to the placement of the ski components in the molds. The adhesive-coated ski components are then placed in the vacuum-wrapped molds in proper fashion. The mold-component assembly is then placed in a press when the ski is formed under pressure and heated so as to set the adhesive. The ski is then stripped off of the mold, the plastic wrap adhering to the ski and leaving behind a clean mold. The plastic wrap is then removed from the ski.

Abstract: The invention relates to apparatus and method for forming a sheet molding compound. The sheet molding compound is linearly advanced. A moveable upper surface formed by a belt passing around a series of driven rollers is adapted to contact the upper surface of the sheet molding compound. The belt is held in biased relationship to the sheet molding compound. In one arrangement of the invention, the sheet molding compound is caused to undulate vertically while retained in compression to induce one form of shear effect. In still another embodiment, as the molding compound is passed in vertically undulating fashion between compressing mesh belts, one of the belts is driven at a fixed rate, while the opposite is driven at rates oscillating above and below the fixed rate.

Abstract: A method of building a closed tube-tire includes constructing a green tire carcass (13) on a disintegratable core (17) and curing the tire carcass (13) in a curing mold (10) having two halves (11,12) which are movable between opened and closed positions. The green tire carcass (13) is intentionally constructed undersized so that a space (18) exists between the green tire carcass (13) and the curing mold (10) to prevent the core (17) from being cracked or crushed when the halves are closed around the tire carcass (13).

Abstract: A mold is described including at least one flexible mold member fabricated from thermoplastic polymeric materials. Desirably, the flexible mold member is placed within a circular torque ring and pressure is applied to flex the mold member into a selected toric configuration, a polymerizable mixture is inserted, the mold closed and the mixture is hardened into the desired lens. Lenses so produced, which may be either flexible or rigid, have at least one surface which is toric in configuration.

Abstract: There is provided a mold comprising a male and a female mold member fabricated from thermoplastic polymeric materials which, in very thin sections are flexible under polymerization conditions, but, under said conditions are sufficiently inflexible in thick sections to retain their shape and surface characteristics. Said mold is provided, on either the male or the female member with a thin rim which, during the polymerization process, flexes and permits the mold members to approach each other and compensate for the shrinkage that occurs during polymerization. Said thin rim further forms the edge of the finished lens.

Abstract: A method and apparatus for forming molded ice sculptures includes a selection of molds fabricated of form retaining, flexible, resilient plastic material. Each mold includes holes in the base thereof through which supporting wires are placed. The mold is inverted, base up, within a box slightly larger than the mold, with the wires impinging on the box and supporting the mold. The mold is filled with water and frozen. Thereafter the mold is removed from the box, the wires removed from the mold and the mold stripped from the frozen sculpture.

Abstract: A method of applying a bag to an aerosol type container wherein the product bag is formed of a stretchable material. An upper part of the product bag is first positioned on a tool, after which the product bag is inserted into the can until the upper part becomes seated on the curl which defines a valve cup receiving opening. Then the tool is actuated to effect a radial outward stretching and deformation of the bag upper part with the bag upper part being formed about the curl and thus secured in place relative to the curl. The tool is then removed, the product bag filled with the product, and the customary valve cup positioned.

Abstract: Method for making a tooth positioning and retaining appliance with air holes. The apparatus includes a mold with a cavity having models of the upper and lower teeth arranged so that when an appliance is molded thereby the appliance will have upper and lower archways for receiving upper and lower arches of a person, tooth sockets in the archways arranged in ideal relationship and preselected positions to urge the teeth received thereby into the preselected positions of the sockets. The mold additionally includes air hole or airway forming means extending across the models of the teeth in the mold and being insertable into the mold prior to the molding operation and thereafter removable from the mold with the molded appliance. The air hole forming means is easily separable from the appliance to ultimately define the air holes between the archways and between the labial and lingual sides of the appliance. The method of making the air holes concerns the handling of the mold and the air hole forming means.

Abstract: Using a highly flowable silicone putty which can be combined with catalysts to set, dentures can be repaired and modified by flowing the putty onto the dentures, allowing it to set while in intimate contact therewith, removing the dentures from the set putty for effecting changes, and subsequently reinserting the dentures in the set putty to effect any necessary changes, modifications or repairs. Prior art practices often used dental stone which had to be chipped away from the dentures when effecting repair or modification.

Abstract: A process and apparatus particularly suited for casting ophthalmic lenses from a liquid monomer such as "CR-39". The liquid monomer and a catalyst are metered into a plastic lower mold member. A plastic upper mold member is supported by the upper surface of the liquid and by a suspension arrangement which includes a spacer ring and a plurality of ears extending from the upper mold member. The upper mold member is controllably drawn downwardly as the liquid plastic solidifies. Optical surfaces are obtained without polishing or other finishing.

Abstract: A method of making plastic aspheric lenses by casting a liquid monomer in a container, polymerizing the monomer to form a solid having an aspheric optical surface formed within the container and cutting a second optical surface on the solid lens material with the container supporting the lens material during the cutting and polishing operation.

Abstract: A tennis racket frame is constructed primarily of an elongated hollow tube member having a wall thereof consisting essentially of a plurality of concentric layers of high tensile strength fibers impregnated and bonded together by binder resin, at least two of the layers being helical windings of opposite unidirectional hands, and the head portion of a racket frame having a groove molded therein to receive the loop portions of the strings in recessed relation to the surrounding surface areas of the frame. The frames are made by a method including the use of a special mandrel on which the layers of fiber are wound under controlled conditions providing extra material in the head portion which is formed into the wall of the grooved portion of the head without affecting the overall sectional dimensions of the frame.

Abstract: A method of making plastic toric lenses by casting a liquid monomer in a container having the required toric curve on the bottom of the container, polymerizing the monomer to form a solid having a toric optical surface formed within the container and cutting a second optical surface on the solid lens material with the container supporting the lens material during the cutting and polishing operation.The container or mold used for casting the lens is made by applying pressure to two opposing sides of a heat softened resinous cylinder to change the shape of the cylinder from a circle to an ellipse, and to change the bottom shape of the cylinder from a spherical surface to a toric surface. The cylinder is then allowed to cool before the pressure is removed.

Abstract: A method of fabricating a bonded composite structure, such as a missile fin, includes the step of forming uncured components for the composite structure with appropriate molds. The individual components are placed together to form an unbonded composite of the structure. The unbonded composite is inserted into a female mold of the composite. The female mold is comprised of material having predetermined high thermal expansion properties. The female mold with the unbonded composite inserted therein is enclosed in a rigid container. The container is heated to expand the mold, apply pressure to the composite, and bond the components of the composite together in a single curing cycle.

Abstract: A process for deposition of polycrystalline silicon from the gas phase on ated carrier bodies of carbon, which comprises assembling the carrier bodies from extremely thin flexible graphite foils, heating the bodies to deposition temperature, while contacting them with a gaseous mixture containing a decomposable silicon compound and, if desired, hydrogen, and separating the deposited silicon from the carrier body, after termination of the deposition process, by mechanical means. The polycrystalline silicon can either be deposited in the form of shaped hollow bodies for use as laboratory equipment or in the semiconductor industries, or it may be processed to monocrystalline materials.

Abstract: A bent pipe of reinforced synthetic resin is produced by supporting a flexible and elastic tubular mandrel in a stiff and straight position, forming layers of fiber impregnated with thermo-hardening synthetic resin about the mandrel, releasing the mandrel from the straightly stiffened position, bending the mandrel in the desired curvature, heat hardening the synthetic resin, and then extracting the mandrel from the bent pipe thus formed and hardened.

Abstract: A method of making plastic lenses by casting a liquid monomer in a container having the required optical curve on the bottom of the container, polymerizing the monomer to form a solid having an optical surface formed within the container and cutting a second optical surface on the solid lens material with the container supporting the lens material during the cutting and polishing operation. Removing the lens from the casting container by applying force against the sides of the container to distort the container and stretching the surface to effect the release of the lens.

Abstract: The disclosure is of a method for cast-molding very thin (eggshell type) body members. The thin members are useful, for example, in model making as components of model vehicles such as model airplanes. By the method of the invention a high degree of control of the thickness of the molded members may be obtained and very strong members produced with integrally molded support members.

Abstract: A system for the production of dipped taper candles, including an overhead conveyor system supporting mobile carrier racks for formation of the candles in suspended relation from the rack, and including a wicking station for providing rows of candle wicks in generally tensioned suspended relation from a carrier rack, a dipping station for automatically dipping said wicks on the rack through a predetermined number of dipping cycles, a cutoff station for cutting off the bases including the wick tensioning weights of the candles suspended from the carrier rack, a butt forming station for heat forming the cut butt ends of candles suspended from the carrier rack, and a cut down station for expeditiously cutting down the carrier rack rows of the candles formed on the candle wicks and for collecting the same for further processing. The invention also provides a novel method of producing physically uniform candles in mass production batches.

Abstract: A matrix is used to prepare a mold of an elastomeric material. A polymerizable compound is coated onto a flexible, thin substrate such as Mylar and is placed with compound side in intimate contact with the mold. The compound is cured and is bonded to the substrate. The cured combination is stripped from the mold and is given a metallic coating to improve reflectivity. A clear plastic coating may be applied to protect the metal surface.

Abstract: The present invention relates to a method and apparatus for reinforcing an object or article essentially comprising a hot-shaped shell, and more particularly to reinforcing a hot-shaped thermoplastic resin sheet with a resin/glass fibre laminate.According to the invention there is provided a method for reinforcing an article or object which essentially comprises a hot-shaped shell, comprising supporting a surface of the shell on an elastically deformable pad intimately matable therewith, placing a mould part having a working surface of shape complementary to the other surface of the shell so that a free space is formed between the mould part and the shell, injecting a reinforcing resin into the free space and then demoulding the thus-reinforced shell.

Abstract: A method for manufacturing an object of silicon nitride by isostatic pressing of a preformed body of silicon nitride powder utilizing a pressure medium at a temperature sufficiently high to sinter the silicon nitride. The preformed body is subjected to a degassing operation before isostatic pressing. An inner porous layer of a first material and then an outer porous layer of a second material are applied on the preformed powder body. The inner porous layer is transformable, at a temperature below the sintering temperature for silicon nitride, into a pressure medium impermeable layer. The outer porous layer is also transformable into a pressure medium impermeable layer, but at a temperature which is lower than the temperature when the inner porous layer is converted into its pressure medium impermeable form.

Abstract: An article expanded at the center portion and having the maximum diameter at said portion, for example a ball-shaped flexible tube joint, is produced by using a mold consisting of a main mold having the same inner surface as the outer shape of said article, a cover mold provided with an elastic core having the same outer shape as the inner shape of the above described article and provided with a hollow cavity in the inside of the core, and a bottom mold provided with a projection, which detachably fits in the hollow cavity in the core, the main mold being put between the cover mold and the bottom mold, and a cavity having the same shape as the article to be molded being formed by the cover mold, the elastic core, the main mold and the bottom mold, and by pouring a liquid elastomer into the thus formed cavity and hardening said liquid elastomer.

Abstract: A pair of like mold parts are juxtaposed to form a mold cavity having a relatively large maximum cross-sectional size and an opening of relatively small cross-sectional size. A core is positioned in this cavity and has a body of cross-sectional size greater than that of the mold-cavity opening and having a neck extending out of the cavity through the opening and blocking this opening. A mass of hardenable material is introduced into the cavity around the core and is hardened. Thereafter the core is elastically deformed and withdrawn from inside the hardened mass whereupon the mold parts are displaced apart to demold the hardened mass.

Abstract: A method of forming a tubular container such as a pipe or a tank includes providing a drum rotatable about an axis with an axially split liner in the drum. The drum and the liner are rotated together about the axis, and a time-setting plastic and reinforcing roving are discharged against the inside of the liner. When the plastic has at least partially set, the liner, plastic and roving are removed from the drum. After further plastic setting, if desired, the liner is removed from the plastic and roving for reuse. Preferably the split in the liner is covered with tape before rotation and is removed thereafter.

Abstract: The method involves assembling an uncured belt body having a stable length tensile section adjacent an inwardly disposed mandrel made of a metal having a high coefficient of thermal expansion, heating the mandrel whereby its thermal properties are utilized to maintain the tensile member in tension, also pressurizing the belt body in a direction toward the mandrel thus sandwiching it, and while maintaining the tensile member in tension, curing the belt body from which one or more endless power transmission belts may be formed. The apparatus utilizes the mandrel in a substantially ring or cylindrical shape about which is disposed inwardly pressure supplying means, an annular cavity disposed between the mandrel and pressure means, and means for supplying heat to the mandrel to intitiate its thermal growth during curing of the belting.

Abstract: Molding apparatus for molding articles without a seam or parting line even though the articles may have severe backdraft portions. The apparatus includes a flexible mold of relatively thick and self-supporting wall construction which is deformable by the application of fluid pressure differential to thereby release the finished article from the mold. One modification of the mold also has a thick radially extending flange which forms a seal with a vacuum pot when the mold is simply set in the pot. One modification is directed to a male and female type mold in which the outer female mold is expanded to be withdrawn from the article and the inner mold portion collapses inwardly so as to be withdrawn from the article.

Abstract: The invention is concerned with the problem of holding in place a plurality of bricks, stones, tiles or the like while they are being assembled into a pre-formed panel for subsequent incorporation into a building or like structure. It has been discovered that the elements can be frozen into place on a water-saturated base surface without any detrimental effect on the setting characteristics of the mortar or other adhesive used to bind the elements. The invention also provides apparatus for carrying out the method.

Abstract: A method is disclosed of reshaping a sheet of resiliently deformable material impervious to fluid by conforming it to the cavity of a female mold and casting a flexible plastic foam into contact with said sheet material, whereby said material is integrated with the foam and forms a cover sheet therefor. A perforated elastic diaphragm is interposed, during the reshaping and foam casting process, between the cover sheet and surface of the mold cavity so that the cover sheet is in superimposed direct contact with the diaphragm throughout its area. The two are clamped to the periphery of the mold to form a seal thereat, and a differential pressure is applied across the cover sheet and diaphragm. The sheet is therefore deformed against the walls of the mold simultaneously with the diaphragm and is stretched evenly with the diaphragm in order to produce uniform thickness.

Abstract: Described is a method for bending rigid extruded theromoplastic-resin shapes without significant deformation of the cross-sectional configuration of the shape. The shape is intimately mated between first and second dies cooperatively configured to define the curvature to which the shape is to be bent. The shape, as mated with the dies, is heated by means of a heating fluid sufficiently to cause the thermoplastic material to lose a substantial portion of its tensile strength but insufficiently to cause the thermoplastic material to melt. Heating is continued as the dies are progressively moved into mating engagement with the extrusion over the extent of the shape to be bent. Thereafter, before the dies are moved apart, the bent shape is cooled sufficiently to restore rigidity to the shape.

Abstract: Method of making a cylindrically shaped, partially collapsible, foam mandrel to be used for the manufacture of hollow resin impregnated fiber tubes. The mandrel is made of a substantially rigid foam cylindrical member, an extractable bar, and a means for aiding in collapsing the cylindrical member such as a groove. Both the extraction bar and the means for aiding in collapsing the cylindrical member are disposed in and along the entire length of the cylindrical member such that the longitudinal axis of the bar, the means for collapsing the cylindrical member, and the axis of the cylindrical member preferably lie on the same plane.The method of manufacturing the aforementioned mandrel comprises the steps of first providing a circular mold having upper and lower sections. A groove-forming member is placed in the lower section and the extraction bar is placed on the upper section. Foam forming material is poured into the lower section which is then covered with the upper section.

Abstract: Ultra-high pressure generation by using a new pressure transmitting medium consisting essentially of powder of an inorganic material having high hardness and cleavage.

Abstract: A flexible resilient printing plate adapted for use on a magnetic printing cylinder is formed by mixing a ferrous metal powder within a volume of liquid vinyl plastisol, casting the mixture onto a face layer of at least partially cured vinyl plastisol to form a base layer, and then heating the combined layers to cure the base layer and fuse it to the face layer to form a flexible multiple layer mold sheet. The base layer is shaved to provide the mold sheet with a substantially uniform thickness, and a porous fibrous impression mat is placed in contact with the face layer. The mat and mold sheet are heated and are placed within a diaphragm press with a porous cloth between the mold sheet and the diaphragm. The mold sheet is pressed into the mat to form a printing plate which is allowed to cool during the pressing operation. The mat and plate are magnetically retained on the bed for a shaver, and the base layer of the plate is shaved to produce a precise uniform caliper.

Abstract: In accordance with a preferred embodiment of this invention, a linear stitching design having improved definition, is embossed onto the surface of a hot, formable plastic sheet and then coated in one operation. The improved definition is achieved by employing a restrained elastomeric anvil to support the sheet during the embossing operation. The elastomeric anvil provides a relatively uniform distribution of pressure on the sheet during the embossing step and urges the sheet into intimate contact with the recessed features on the embossing die surface. Once the sheet is formed but before the embossing die and anvil surface are separated, paint is injected through passages in the embossing die onto the surface of the thermoplastic sheet. The paint is injected under sufficient pressure to force the thermoplastic sheet, which is supported by the elastomeric anvil, away from the die surface; this provides the necessary space to allow the paint to flow onto specified areas of the sheet.

Abstract: A method for casting pneumatic tires by pouring a fluidized tire-forming material into a molding cavity defined between the outer peripheral surface of a separable hard core of a mold assembly and the inner peripheral surface of an outer separable hard mold member of the mold assembly. The separable hard core is composed of at least three segments and toroidal in shape. At least one segment of the separable core is retracted in a radial direction and then moved in a direction which does not hinder retractive movement of the remaining segments and subsequently these remaining segments are retracted in the radial direction, whereby the cast tire can easily be removed from the mold assembly.

Abstract: A method for molding elastomeric stock, the method comprising interposing an apertured, heat-resistant, flexible, insulation plate between a heated mold and the discharge portion of an elastomeric stock injection unit such that respective mold cavities provided in the mold are aligned with respective apertures in the insulation plate which intercommunicate the mold cavities with an internal discharge chamber in the injection unit. The mold and injection unit are moved relative to one another such that each presses against the other through the intermediary of the insulation plate, thereby permitting expulsion and transferring of a portion of elastomeric stock from the injection unit into the mold cavities to be cured, an excess portion of elastomeric stock remaining in the injection unit being prevented from undergoing curing by means of the presence of the insulation plate.

Abstract: A tubular tire for bicycle, automobile and the like, having a tubular cross section and comprising a tread portion, side portions and a bottom portion, is manufactured by molding a base tire composed of the side portions and the bottom portion from a fluidizable high polymer material by means of a split mold assembly and then molding the tread portion and hence a tire product from a fluidizable high polymer material by means of a centrifugal molding machine. The split mold assembly comprises a core having an outer peripheral surface coincident with an inner profile of the base tire and separable mold members having an inner peripheral surface coincident with an outer profile of the base tire.

Abstract: Fiber reinforced plastic structural components having curved surface areas are produced in molds utilizing a bleeder cloth comprising a textile-like non-woven polyester fabric characterized by a fiber interlock value of at least 7 and a fiber entanglement completeness of at least 0.5. The utilization of this bleeder cloth allows quicker assembly of the mold components since cutting and forming are not necessary, proper pressure transmittal is ensured, and the air permeability, drape, stretchability, and resin holding capacity of the cloth are ideal. For producing the desired structural components with curved surface areas, at least one layer of resin pre-impregnated partially cured fabric is disposed in cooperation with a first mold section, a release liner is placed on the fabric, and a bleeder cloth according to the invention is placed on the release liner.

Abstract: A flexible mold and process is provided for making pots, and the like, the mold comprising a cylindrical-shaped rubber-like resilient member having an annular-shaped cavity contained therein, and an open top. The construction of the mold is such the pressurized air may be introduced into the cavity to move the outer peripheral portion of the mold radially outwardly to release the part being molded. A nail, or similar article may be inserted into the central part of the mold to protrude through the open top of the mold along the central axis thereof. The nail causes a hole to be formed in the bottom of the article being molded which serves as a water hole when flower pots, for example, are being molded, and which also provides a convenient hole through which the releasing pressurized air may be introduced into the mold cavity.

Abstract: The invention relates to a new method for manufacturing shaped articles from multi-block copolymers of acrylonitrile with acrylamide and/or acrylic acid, using hot pressure molding, preferably in swelled condition.

Abstract: A device for deflecting a continuously supplied thread by means of a curved guide tube. The guide tube is formed of a plurality of contiguously abutting segments which are disposed between the entry and exit openings of a casing. The space between the inner wall of the casing and the outer circumference of the segments is filled with a bonding agent which fixes the segments in the desired spatial curvature for the guide tube when it hardens. Furthermore, a method for producing such device is disclosed which utilizes an expandable mandrel to hold the segments in the desired spatial curvature position prior to being fixed in position by the bonding agent.

Abstract: A pneumatic tire is moulded using a mould core of cured rubber the radial sectional shape of which is the same as the internal radial sectional configuration of the finished tire. The opposite sides of the core are supported by fitting plates while a tread portion of tire is moulded onto the exposed outer periphery of the core. Thereafter the side plates are removed in turn and replaced by sidewall mould halves enabling sidewalls to be moulded against the core in contact with the tread portion.

Abstract: A method of manufacturing of a novel very fine seamless heat resistant synthetic resin tube having a wall thickness of not more than 0.3 mm, by applying a specific heat resistant synthetic resin varnish as defined in the specification on a metal wire and curing said resin varnish to form the synthetic resin layer on the metal wire, drawing the heat resistant synthetic resin coated wire above the yield point of the metal wire and separating the resulting synthetic resin tube from the metal wire.The method of the present invention may produce a composite heat resistant synthetic resin tube in which a plurality of the above-described tubes are made to adhere tightly parallel with each other in the longitudinal direction or a double layer resin tube, one layer of which is a thermally adhesive synthetic resin and the other layer of which is the heat resistant resin.

Abstract: A method of casting liquid compositions in elastomeric molds wherein the casting composition has a reaction temperature below about 235.degree. F comprising:A. introducing an organic solvent soluble polyol, a liquid polyisocyanate and a basic curing catalyst having a pK.sub.b value from between 7 and about 11 into an open elastomeric mold,B. controlling the ratio of polyol to polyisocyanate and the concentration of the curing catalyst and casting the resin such that the cured resin is: substantially free from entrapped air at the mold surface, free from foaming, has a cast time of generally less than about 15 minutes, has a tensile strength of at least about 2500 psi,C. removing the cast resin from the mold shortly after the composition is cast thereby providing unexpected prolonged mold life. The resin undergoes substantially no change in volume from the liquid to the cured state.

Abstract: A method of shaping a bell end on a pipe of thermoplastic material, in which an elastic shaping ring is expanded radially in its operative position during the shaping of the bell end, and removed from the formed bell end by radial contraction. Part of a shaping mandril is moved to create a cavity into which the ring is free to contract.

Abstract: There is disclosed a novel process for using a pressure box assembly associated with a thermoplastic thermoforming assembly. The pressure box assembly is provided with a diaphram formed of a resilient material, such as synthetic rubber and the like, disposed across the entrance into a cavity of the pressure box of the pressure box assembly.The pressure box assembly is associated with thermoforming molding apparatus to cause a heat thermoplastic sheet or web to be drawn about a male mold provided on a male mold assembly during insertion of the male mold into the cavity in a hollow article of more uniform wall thickness.

Abstract: An apparatus for molding articles free of seams and parting lines including a one-piece flexible mold which is deformable and which includes a rigid core member, and a vacuum pot which is used to cause the mold to expand radially outwardly to allow the molded article to be released. The core member may comprise a rigid central mandrel which is rigidly embedded in the bottom wall of the mold and which is hollow and includes ports such that a pressurized catalytic gas may be injected into the mold material to cause a bonding agent to set.

Abstract: Method for making isostress contoured dies by providing a cavity containing multiple vertical supports. A flexible material is tensionally secured across the top of the cavity to contact the supports and pneumatically deformed to assume an isostress contour. A form setting material is deposited and cured against the isostress contoured flexible material. The cured material may then be used directly as a die or as a die-forming master pattern.

Abstract: A commercially feasible method is provided for molding high quality seamless, irregularly shaped articles such as wax candles which are essentially free of surface defects and other molding imperfections by provision of relatively thin-walled, self-sustaining but distensible molds having high heat transfer properties, in conjunction with mold-receiving housing structure including liquid delivery, circulation and removal apparatus for supporting the molds against perceptible distension under the weight of molding material while accelerating solidification of the wax, and for inducing distension of the molds by the technique of removing only a small portion of the cooling liquid without creating significant liquid-free voids in the mold tank. Thus, the method hereof avoids the necessity of complete draining of the mold tank during each molding cycle which in turn speeds the process and renders it more economical.

Abstract: A plug valve whose chamber or bore and whose runs or port passages are fully lined with corrosion-resistant material, most preferably polytetrafluoroethylene, such valve having recesses in its runs, near their intersection with the bore, into which lining material distended by heat and pressure may creep, and with the valve body defining an internally-rounded concave wall or dome at the bottom of the bore. The lining material is formed within the runs so as to be under tension longitudinally between the bore and the outer ends of the runs, and the lining material extends integrally upwardly from the bore and outwardly of the valve body to define a thick collar immediately above the neck of the bore. The valve is manufactured by use of an integral hollow rubber or like forming element comprised of tubular legs, and is placed inside the valve body with one such tubular leg extending through each run and through the bore.