Apparatus And Process For Producing Pultruded FRP Rebar

Abstract

Apparatus for producing bent multi-sided pultruded fibre reinforced plastic reinforcement bar for concrete (commonly known as FRP rebar) comprises multiple resin wetting stages to simultaneously resin impregnate multiple bundles of fibreglass rovings continuously drawn through the resin wetting stages, multiple spiral winding stages arranged to spiral wind warps around the multiple wet rovings, and multiple rotating multi-sided former frames for continuously winding thereon the multiple wet rovings and holding the multiple rovings while curing. A related method is also claimed.

Claims

1. 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.

2. A process according to claim 1, wherein the continuously drawing multiple bundles of fibre rovings through at least one resin wetting stage comprises continuously drawing multiple bundles of fibre rovings through multiple adjacent resin wetting stages.

3. A process according to claim 1 comprising 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.

4. A process according to claim 1 comprising 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.

5. A process according to claim 1 comprising pressure impregnating resin into the bundles of fibre rovings at the resin wetting stages.

6. A process according to claim 1 wherein each former frame has at least four sides.

7. Apparatus for producing bent multi-sided pultruded FRP rebar, which comprises: multiple resin wetting stages to simultaneously resin impregnate multiple bundles of fibreglass 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.

8. Apparatus according to claim 7 comprising at least two former frames operable independently enabling a first of the two to rotate to wind on multiple wet rovings while removing cured product(s) from the second former frame and then the second former frame to rotate to wind on multiple wet rovings while removing cured product(s) from the first former frame.

9. Apparatus according to claim 7 wherein each former frame has at least four sides.

10. Apparatus according to claim 7 wherein the resin wetting stages are pressure resin impregnating stages.

11. Apparatus according to claim 7 wherein the resin wetting stages comprise entry ports for rovings bundles, into an internal cavity or cavities, and exit ports, and a resin entry port or ports for supplying resin into the interior of each internal cavity or cavities.

12. Apparatus according to claim 7 comprising gripper wheels after the spiral winding stages in the machine direction for drawing the rovings bundles through the machine.

13. Apparatus for producing bent multi-sided pultruded FRP rebar product, which comprises multiple resin wetting stages to simultaneously resin pressure impregnate multiple bundles of fibreglass 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.

14. Apparatus for producing bent multi-sided pultruded FRP rebar, which comprises: multiple resin wetting stages to simultaneously resin impregnate multiple bundles of fibreglass rovings continuously drawn through the resin wetting stages, multiple spiral winding stages each arranged to spiral wind warps around the multiple wet rovings, and multiple rotating multi-sided former frames for continuously winding thereon the multiple wet rovings and holding the multiple rovings while curing, enabling one or more former frames to rotate to wind on multiple wet rovings while removing cured product(s) from one or more other former frames, and then said one or more former frames to rotate to wind on multiple wet rovings while removing cured product(s) from said one or more other former frames.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0028] The invention is further described with reference to the accompanying figures, by way of example and without intending to be limiting. In the figures:

[0029] FIG. 1 is an overall view of an embodiment of apparatus or machine of the invention,

[0030] FIG. 2 is a perspective view of the underside of the resin wetting and spiral winding stages of the machine of FIG. 1,

[0031] FIG. 3 is a cross-section view of the resin wetting and spiral winding stages,

[0032] FIG. 4 is a perspective view of the top or entry end view of the resin wetting and spiral winding stages,

[0033] FIG. 5 is an underside or exit end view of the resin wetting and spiral winding stages,

[0034] FIG. 6 is an entry side view of rotating former frames of the machine of FIG. 1,

[0035] FIG. 7 is a plan view of the former frames,

[0036] FIG. 8 is a side view of the former frames, and

[0037] FIG. 9 shows an example of a bent multi-sided pultruded FRP rebar product produced by the machine.

DETAILED DESCRIPTION OF EMBODIMENT(S)

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] The frames 10/11 at each of eight corners comprise a slotted former 14 (all marked in

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.