Apparatus And Process For Producing Pultruded FRP Rebar

The invention relates to an apparatus and process apparatus for producing bent multi-sided pultruded fibre reinforced plastic reinforcement bar for concrete (commonly known as FRP rebar).

Pultruded FRP rod is produced by drawing a bundle of fibreglass or other reinforcement rovings through a resin bath to wet the roving with resin, and subsequently heating the wet roving to cure the resin and form a solid product.

Reinforcing bar or rebar used as concrete reinforcing is typically formed from steel rod but may be formed from fibre reinforced bar or rod. Steel rebar may comprise straight lengths or may be bent to multi-sided shapes. Typically reinforcing in a square cross-section concrete beam for example, comprises multiple rebar lengths in the length of the beam, and three or four-sided bent steel rebar elements spaced in the length of the beam to tie the rebar lengths together. These are wire-tied to the rebar lengths to hold them in place before the beam is poured.

An object of the invention is to provide an improved or at least alternative apparatus and/or process apparatus for producing bent multi-sided pultruded composite rebar.

In broad terms in one aspect the invention comprises apparatus for producing bent multi-sided pultruded FRP rebar, which comprises:

• • multiple resin wetting stages to simultaneously resin impregnate multiple bundles of fibre rovings continuously drawn through the resin wetting stages,
  • multiple spiral winding stages each arranged to spiral wind warps around the multiple wet rovings, and
  • a rotating multi-sided former frame or frames for continuously winding thereon the multiple wet rovings and holding the multiple rovings while curing.

In broad terms in another aspect the invention comprises a process for producing bent multi-sided pultruded FRP rebar, which comprises:

• • continuously drawing multiple bundles of fibre rovings through at least one resin wetting stage to resin impregnate the rovings,
  • spiral winding warps around the multiple wet rovings,
  • continuously winding the multiple wet rovings simultaneously onto a rotating multi-sided former frame, and
  • curing the resin in the multiple rovings while on the former frame(s) to form bent multi-sided pultruded FRP product.

In broad terms in another aspect the invention comprises a process for producing bent multi-sided pultruded FRP rebar, which comprises:

• • continuously drawing multiple bundles of fibre rovings through adjacent resin wetting stages to resin impregnate the rovings,
  • spiral winding warps around the multiple wet rovings,
  • continuously winding the multiple wet rovings simultaneously onto a rotating multi-sided former frame, and
  • curing the resin in the multiple rovings while on the former frame(s) to form bent multi-sided pultruded FRP product.

In some embodiments the process comprises cutting the bent multi-sided pultruded FRP bar on the or each former frame into multiple individual bent multi-sided pultruded FRP rebar end products.

In some embodiments the process comprises winding multiple wet rovings onto one or more rotating multi-sided former frame(s) while removing cured product(s) from one or more other former frame or frames.

In broad terms in a further aspect the invention comprises apparatus for producing bent multi-sided pultruded FRP rebar, which comprises multiple resin wetting stages to simultaneously resin pressure impregnate multiple bundles of fibre rovings continuously drawn through the resin wetting stages, and multiple spiral winding stages each arranged to spiral wind a warp around a wet roving exiting one of the resin wetting stages.

In this specification:

• • “bar” or “bar product” includes pultruded FRP material having any of a circular, oval, square, rectangular, or other polygonal cross-section shape i.e. “bar” includes “rod”, and “rebar” “or rebar product” have a similar meaning.

“bent” is used to describe the shape of a non-straight multi-sided pultruded FRP rebar product, having at least one bend creating at least two lengths or sides, and which may have two or three bends between three or four or more sides, and does not refer to or require that the solid rebar product have been bent after manufacture.

• • “multisided” means having two or more sides and includes circular or oval or part-circular or oval or similar.
  • “comprising” means “consisting at least in part of” and when interpreting a statement in this specification and claims that includes “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted similarly.
  • “FRP” means fibre reinforced plastic, most commonly comprising glass fibres, but which may comprise other fibre types such as, basalt, carbon, or aramid fibres for example.

Referring first to FIG. 1, the embodiment of apparatus or machine comprises multiple resin wetting stages 1, multiple spiral winding stages 2, and rotating multi-sided former frames 3 as will be further described. The machine simultaneously produces multiple bent multi-sided pultruded FRP rebar end products 4, suitable for use as reinforcing in place of conventional steel rebar product. An example of one individual rebar end product is shown in FIG. 9. The rebar product is intended for use in reinforcing a concrete beam, as one of multiple bent rebar elements spaced in the length of the beam that ties longitudinally extending rebar lengths together. The pultruded FRP rebar 4 shown is eight-sided with two ends 4a, but may have three or more sides, or two sides connected at one or both ends for example, or may be circular or oval or part-circular or oval or similar. The ends of the rebar may be simple cut ends or may comprise bent hook or other bent end shapes.

FIGS. 2 to 5 show the resin wetting and spiral winding stages of the machine of FIG. 1. In operation the multiple resin wetting stages operate together to continuously and simultaneously resin impregnate multiple bundles of rovings of glass fibre or other suitable fibre such as basalt, carbon, or aramid fibres for example or a mixture thereof, continuously drawn through the machine. The spiral winding stages then operate to spiral wind a warp around each individual wet roving. For simplicity FIGS. 2 to 4 show two adjacent resin wetting winding stages. Each comprises an entry port 5 for a rovings bundle, into an internal cavity 6, and exit port 7. A resin entry port 8 supplies resin into the interior of each cavity 6. Optionally, resin may be supplied under pressure. In use rovings bundles R—see FIG. 3, move at a steady speed through entry ports 5 and exit from port 7. The rovings bundles are drawn through the machine by gripper wheels (not shown) after the spiral winding stages 2 in the machine direction, driven by an electric motor. As the rovings bundles move through the impregnation cavities 6 they are impregnated with resin, so that the rovings bundles are wet with resin when they exit ports 7. The resin and the machine speed are co-ordinated to ensure that the rovings bundles are impregnated with resin through their full cross-sections.

As the wet rovings R exit the impregnation stage a warp is spiral wound around each wet rovings bundle. Each warp may comprise a single strand or a small bundle of multiple strands, of the same material as the fibre rovings, or other suitable material such as Nylon or other synthetic material or cotton or other organic material for example. The spiral warp is wound at a spaced pitch, such that for example if the impregnated rovings bundle has a cross-section dimension in the range 1-3 cm for example, then the warp pitch may also be in the range 1-3 cm. The spiral warp is preferably wound at a tension to slightly compress the rovings bundles beneath the warp along the length of the warp where it contacts the rovings, relative to the rovings segments between warp spirals, which help create a non-smooth exterior surface on the finished solid rebar product and may give it a slightly varying diameter. Referring to FIGS. 2 to 5, a warp bobbin 8 supplies the warp to a rotating winder 9 around each exit port 7. The winders 9 operate simultaneously to spiral wind the warps around the wet rovings bundles as each exits the resin impregnation stage.

FIGS. 6 to 8 show the rotating multi-sided former frames 10 and 11 of the machine of FIG. 1. In the embodiment shown the former frames are carried on an axle/axis 12 through the top of pedestal 13 as shown, and rotate as indicated by arrows F (see FIGS. 1 and 8). In the embodiment shown the frames 10/11 are eight sided, to produce eight-sided rebar components as shown in FIG. 9.

The frames 10/11 at each of eight corners comprise a slotted former 14 (all marked in

FIG. 6) around which the multiple wet rovings after impregnation and warp winding, are wound. In FIGS. 1 and 8 rovings on one frame 11 are indicated at R. The rovings are held on a frame while cured. Motor drive to each frame is individually controlled. While one frame is rotating—frame 11 at the point shown in the figures, receiving the two wet rovings from the two resin wetting stages, which are wound as two continuous adjacent spirals onto the one frame, the other frame rotating—frame 10 at the point shown in the figures, is stationary while cured by heat application onto the rovings previously wound onto that frame, and then while the cured (solid) multisided product is removed from that frame.

The two cured roving turns on that frame 10 (multiple turns for example 6 turns) may be cut into individual (for example 10) multisided products which are then individually removed from the frame 10, or in an alternative embodiment the whole frame may be removed and replaced with another empty frame, and the roving turns cut from that frame while off the machine, into individual products.

While one of the frames on one side of the machine is driven to rotate, and take up wet roving the cured roving on the other side of the machine is being removed. The speed of rotation of the moving frame is co-ordinated with the speed of movement of the roving bundles through the machine.

In the embodiment described above the two resin wetting stages and spiral warp winding stages feed one of the two former frames while the other former frame is stationary during curing and removal but in a higher volume production embodiment three or four or more resin wetting and spiral warp winding stages may feed three or four or more former frames.

The foregoing description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of the invention as defined in the accompanying claims.