Impregnating a fibrous web with liquid

A method for producing plastic pipe on a rotating pipe mandrel from at least one layer of a fibrous material saturated with liquid resin comprising the steps of:

• (a) preparing a web comprising at least one layer of fibrous material;
• (b) moving the web longitudinally under tension;
• (c) placing the liquid resin on only one surface of the web;
• (d) spreading the placed liquid resin across the width of the web;
• (e) only partially saturating the web with the spread liquid resin by pressuring only a portion of the spread liquid resin into the web by contacting the spread liquid resin with a stationary surface converging with the web in the direction of travel of the web, thereby leaving a layer of residual liquid resin on the one surface of the web;
• (f) leveling such residual liquid resin into a layer of substantially uniform thickness on the surface of the web by maintaining the surface converging with the web spaced apart from the surface of the web;
• (g) pressing such leveled residual liquid resin into the web to completely saturate the web with liquid resin by winding the web around the rotating pipe mandrel;
• and
• (h) solidifying the resin on the pipe mandrel.

A method for producing plastic pipe on a rotating pipe mandrel from at least one layer of fibrous liner material saturated with liquid resin comprising the steps of:

• (a) preparing a web comprising at least one layer of liner material;
• (b) moving the web longitudinally under tension;
• (c) applying liquid resin onto only one surface of the moving web;
• (d) contacting the applied liquid resin with a first stationary surface substantially perpendicular to the surface of the web for spreading the liquid resin across the width of the web;
• (e) contacting the spread liquid resin with a second stationary surface converging with the web in the direction of travel of the web for pressuring a portion of the spread liquid resin into the web while leaving residual liquid resin on the one surface of the web;
• (f) contacting the surface of the web with a plurality of smooth projections of substantially uniform height on the underside of the trailing edge of the second surface to hold the said trailing edge out of contact with the surface of the web and prepare a layer of the residual liquid resin of substantially uniform thickness on the web's surface, wherein the projections are smooth-surfaced and extend in the direction of travel of the web;
• (g) pressing residual liquid resin into the web to completely saturate the web with liquid resin by winding the web onto the rotating pipe mandrel;
• and
• (h) solidying the resin on the pipe mandrel.

An apparatus for impregnating a moving fibrous web with a liquid resin comprising:

• means disposed above the top surface of the fibrous web for applying a liquid resin to only the top surface of the web;
• means for spreading the liquid resin over the top surface of the web, including:
• means forming a stationary surface converging with the web in the direction of travel of the web for pressuring a portion of the liquid resin into the web to only partially saturate the web and leave residual liquid resin on the web;
• and
• means for holding the trailing edge of the converging surface out of contact with the surface of the web for metering the residual liquid resin into a layer of substantially uniform thickness on the top surface, the liquid resin in the residual layer plus liquid resin partially saturating the web being at least sufficient for completely saturating the web;
• and
• means for pressing the layer of residual liquid resin through the web to completely saturate the web with the liquid.

An apparatus for impregnating a moving fibrous web with a liquid resin comprising:

• (a) a first stationary surface transverse to the web for spreading applied liquid over the top surface of the web;
• (b) a second stationary surface converging with the top surface of the web in the direction of travel of the web for pressuring liquid resin into the web;
• and
• (c) a plurality of projections of substantially uniform height positioned between the trailing edge of the second surface and the web for metering liquid resin over the top surface of the web, wherein said projections are attached to the second surface and extend toward the top surface of the web for contacting the top surface of the web and maintaining the trailing edge a selected distance from the web.

An apparatus for manufacturing reinforced plastic pipe comprising a doctor bar assembly for impregnating a moving fibrous lining material with a liquid resin applied to only one surface of the lining material, wherein the doctor bar comprises:

• a first stationary surface substantially perpendicular to the one surface of the lining material for spreading liquid resin applied to the one surface of the lining material, wherein the first surface extends beyond both longitudinal edges of the lining material;
• a second stationary surface at least as wide as the lining material converging with the one surface of the lining material in the direction of travel of the lining material for pressuring spread liquid resin into the one surface of the lining material, wherein the second surface extends beyond both longitudinal edges of lining material;
• and
• a plurality of smooth-surfaced, laterally spaced-apart, elongated projections on the trailing edge of the second surface, wherein the projections extend toward the web and beyond the second surface in a direction substantially parallel to the direction of motion of the web for contacting the one surface of the lining material and maintaining the trailing edge a selected distance from the lining material.