Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/28—Shaping operations therefor
  • B29C70/40—Shaping or impregnating by compression not applied
  • B29C70/50—Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC]
  • B29C70/52—Pultrusion, i.e. forming and compressing by continuously pulling through a die
  • B29C70/525—Component parts, details or accessories; Auxiliary operations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C59/00—Surface shaping of articles, e.g. embossing; Apparatus therefor
  • B29C59/02—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
  • B29C59/04—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing using rollers or endless belts
  • B29C59/043—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing using rollers or endless belts for profiled articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/06—Fibrous reinforcements only
  • B29C70/08—Fibrous reinforcements only comprising combinations of different forms of fibrous reinforcements incorporated in matrix material, forming one or more layers, and with or without non-reinforced layers
  • B29C70/081—Combinations of fibres of continuous or substantial length and short fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/28—Shaping operations therefor
  • B29C70/40—Shaping or impregnating by compression not applied
  • B29C70/50—Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC]
• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
  • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
  • E04C5/07—Reinforcing elements of material other than metal, e.g. of glass, of plastics, or not exclusively made of metal
• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
  • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
  • E04C5/16—Auxiliary parts for reinforcements, e.g. connectors, spacers, stirrups
• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
  • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
  • E04C5/16—Auxiliary parts for reinforcements, e.g. connectors, spacers, stirrups
  • E04C5/162—Connectors or means for connecting parts for reinforcements
  • E04C5/163—Connectors or means for connecting parts for reinforcements the reinforcements running in one single direction
  • E04C5/165—Coaxial connection by means of sleeves

Definitions

• the original Patent 631881 was directed primarily to a means for and a method of forming a rock bolt of fibreglass reinforced plastics material (particularly a polyester formulation), but did not disclose any means for or method of rendering a rock bolt electrically conductive.
• the later specification discloses a method of rendering a rock bolt electrically conductive, and disclosed a method of production of such a rock bolt.
• the method disclosed in that specification indicated the need to supply sufficient pressure to wetted tows to cause flow of resin into contact with bolt thread forming surfaces, and further disclosed applying chopped strand reinforced fluid but settable plastics mix to the wetted tows at the locality of a thread forming surface, before closure of dies.
• the method disclosed forming a bolt with a shank longer than the shank forming surface of the dies by firstly forming a bolt with a shank equal to the length of the shank forming surface, and withdrawing the threaded end outwardly from between the dies so as to form further wetted tows of a bundle between the shank forming cavities of the die and again closing the die to clamp portion of the shank and applying pressure to the wetted tows while the resin sets. Pressure was also indicated to be required to force resin to flow into close contact with thread forming surfaces, and protuberance recesses.
• the pressures exceed 500 psi (3500 kPa) for viscosities up to 2000 centipoise, and 700 psi (5000 kPa) for viscosities above 5000 centipoise, or for densely packed fibres. Efforts have been made by the inventors to get even higher pressures. It is believed that under those pressures the air actually dissolves in the resin, but does not appear to have any deleterious effect on the shear strength of the resin which is relevant to the torsional strength of the product.
• a problem which is encountered if high pressure is used in moulding a fibre reinforced product is that the resin tends to be extruded from the ends of a die through which the product extends. If that extrusion takes place at the upstream end of a hot die, a bulbous knob of set resin will form which needs to be removed, and that operation is not viable for production of continuous uniform length products.
• the main object of this invention is inhibition of extrusion of resin through die ends and preventing a bulbous knob from forming at the entry end of the die
• clamping means comprised in the die, and having a cold surface at the upstream end of the die, the clamping means preferably being separate blocks appended to the die ends, while obviously they can be constituted by portion of the heated die itself at the upstream end, if it is kept water cooled.
• This invention relates to the abovementioned method, and to further enhancements of the production method disclosed in the later specification.
• there is a requirement which is frequently met of producing an elongate product of a length which is within a tolerance specified by a customer and further, quite often there is a requirement for a fibre reinforced plastics product which is suitable for use as a reinforcement bar for reinforcing of concrete.
• withdrawal of a precured product from an open die is only partial, the moulded tail end functioning as a "plug" at the downstream end of the die so as to enable high die pressures to be used.
• the degree of withdrawal can be varied, so that products can be moulded to varying lengths which are greater than the die length and in the case of concrete reinforcing bar, to a tolerance of one pitch of the protuberances on its outer surface.
• the invention can be extended to other products, which are not necessarily of constant cross-sectional shape throughout their lengths. In those instances, wherein part of the product length has a constant cross- section, products can be made to a very small length tolerance.
• tensile strength is the most desirable feature, and the tensile strength is largely a function of the amount of reinforcing fibre which exists in a given cross-sectional area in a product. For that reason, it is an object of this invention to provide improvements whereby the ratio of fibres to resin may be much higher than what has been commercially produced previously, achieved by using the abovementioned higher pressures.
• production of elongate moulded products of settable resin reinforced with fibres comprises the steps of drawing a bundle of fibres through a bath of fluid but settable resin mix and between cavities of die portions of an open die, closing the open die under pressure to form the shape of the required product, applying heat and maintaining pressure to cure the resin and form a product, and clamping the wetted tows between unheated surfaces at the upstream end of the die so as to prevent expulsion of resin from the die cavities.
• the invention can further comprise partly withdrawing the product from the die lengthwise so as to introduce further tows and entrained resin between the cavities of the open die, producing subsequent products successively each by repetition of those steps, and severing the moulded products from one another externally of the die.
• the cured product may be clamped by a spring loaded clamping block where it projects at the downstream end of the die, and the wetted tows adjacent the upstream end of the die clamped between cold surfaces with sufficient force to inhibit resin expulsion from the die.
• the cold surfaces are used at the upstream end so that, notwithstanding restrition against expulsion, if any resin is expelled through the upstream end, that resin is not heated as the resin within the dies is heated, and therefore remains in a fluid state in the tows as they are drawn through the dies to produce a subsequent product.
• the cold clamping surfaces at the upstream end are surfaces of a pair of water cooled metal clamping blocks which come together upon closure of the dies, and are separated from the hot portions of the die ends by means of a heat insulating separator pad. There is no need to water cool the clamping blocks at the downstream end of the dies, since the clamping blocks (which form portions of the die portions) only engage cured material, or in extreme conditions, are themselves sufficiently hot to cure the resin.
• a three part die portion for defining thread forming surfaces, two of the portions separating out laterally when the die is opened and the third portion being lifted away, and the length of the thread forming portion equals the combined lengths of two threads one at each end of a product, the first said product being separated from the second said product and so on by dividing the thread into two equal parts externally of the die.
• the cured resin should not extend into the cavity for the length of the thread when forming a thread, since moulding of uncured resin over cured resin may fail to achieve full adhesion, when a thread forming mix is injected.
• Fig 1 shows the steps of drawing a bundle of fibres through a bath of fluid but settable resin mix
• Fig 2A shows the steps of closing die portions of a die to form a product, with the upstream end of the die closed by a water cooled clamping block and the downstream end of the relevant part of the die closed by the tail end of the previously moulded product;
• Fig 2B is a continuation of Fig 2A and illustrates the severing of previously moulded products externally of the die;
• Fig 3 is a section taken on plane 3-3 of Fig 2A, showing the three part die at the thread forming locality at the downstream end of the die, drawn to a larger scale;
• Fig 4 illustrates the thread formation and the fibre formation at the locality of threads;
• Fig 5 is a view similar to Figs 2A and 2B, but showing rock bolts being formed two at a time with the thread forming portion of the die central between its upstream and downstream ends;
• Fig 6 shows to a larger scale the detail of the cold blocks which are otherwise illustrated in Figs 2A and 5;
• Fig 7 is a fragmentary "exploded" view of the downstream end clamping blocks
• Fig 8 shows a joining of continuously threaded reinforcing bars by means of a tumbuckle nut
• Fig 9 shows a threaded end which could be useful in retaining the ends of a reinforcing bar in concrete
• Fig 10 shows one form of hook arrangement again using a turnbuckle nut, for positioning upper and lower reinforcing bars
• Fig 11 shows an alternative arrangement wherein a length of threaded reinforcing bar terminates at its ends in upper and lower hooks.
• a series of reels 14 carry fibreglass or other fibre strands 15 (carbon, or aramid "Kevlar”) which pass through a bath 16 containing fluid but settable polyester resin 17, and pass over the three curved deflectors 19, 20 and 21 and into nozzle 22 to emerge as a bundle of tows 23.
• fibreglass or other fibre strands 15 carbon, or aramid "Kevlar"
• the bundle of tows 23 passes first through a pair of metal clamping blocks 24 cooled by waterway 26 as shown in Fig 2A, then through a heat insulating separator pad 25 which in this embodiment is of PTFE ('Teflon") to which the resin is non adhesive.
• the bundle 23 is drawn through the then open die portions 27 and 28, the die portions being heated by embedded thermostatically controlled heating elements 29, and being closable by means of hydraulic rams 30 which are arranged to apply a projected area pressure of more than 200 psi (1400 kPa), but in this embodiment, the pressure is in the order of 1000 psi (7 mPa).
• a thread forming formation 31 which, as shown in Fig 3, is constituted by an upper part 32, and two lower parts 33 and 34, and the lower parts are separable laterally to open the die while the upper part moves upwardly.
• the three part die portion is required because of the return surfaces of a thread when moulded. If a fully threaded rod is required, the entire length of the die needs to be three part.
• the circular shape shown in Fig 2 may have parallel sides as shown in the later specification.
• the thread forming portion 31 and its die parts extend for double the length of a required thread 37 (Fig 2B), and an accurately determined amount of thread forming resin is injected by an adjustable injection ram 38.
• an accurately determined amount of thread forming resin is injected by an adjustable injection ram 38.
• the pitch diameter is made greater than the outside diameter of the shank 39 of a reinforcing bar, but the thread mix is of stronger material.
• Use can, for example, be made of chopped fibreglass strand embodied in a high strength resin (in this embodiment, using 20 parts of chopped strand glass fibres to 100 parts of resin).
• the resin used in the shank was a relatively inexpensive resin (eg, an isophthalic resin having only 1 % to 2% elongation).
• the thread resin is a Dow Chemical 'Derakene 411 vinyl ester" having a 4% to 5% elongation.
• Bulked roving is a texturized product which incorporates transverse filaments in addition to axis-oriented filaments, and is produced by PPG Industries Inc., Fiber Glass Products, One PPG Place, Pittsburgh, Pennsylvania, USA.
• the reinforcing bar which is shown to be produced in Figs 2A and 2B is an elongate bar, and the length is determined by the dumber of portions which are moulded in succession within the shank forming part of the die.
• the bundle of tows is drawn through the separated die portions 27 and 28, and the die is closed, the upstream and downstream projecting ends of the tows being clamped to avoid excessive resin expulsion.
• Thread composition is injected to form a thread adjacent the downstream clamping blocks 41 , the clamping blocks 41 enabling high pressure to be used to produce a first moulding, as well as all successive mouldings.
• the die portions are separated and the three part die of Fig 3 is also opened and the cured product is withdrawn from the die portions by the puller 42, until the cured end of shank 39 is located slightly upstream of the thread forming formation 31 , and this then functions as a plug to prevent extrusion of resin from the downstream end.
• Formed protuberances 52 (if any) must register in the die recesses.
• the shank length is then extended by closing the die portions and setting the resin entrained by the tows in the bundle 23 upstream of the set portion of the shank 39, without forming further threads.
• the distance the set portion of shank 39 penetrates the die cavity upstream of the thread forming formation 31 will determine the final length of the reinforcing bar. This is controlled by controlling the distance of the set portion of shank 39.
• the downstream clamping blocks 41 are required to clamp the previously cured tail end of a formerly moulded product to inhibit resin extrusion, and therefore is spring loaded downwardly by Bel I vi He springs 43.
• the third closure occurs when the shank has been withdrawn further by the puller 42, and for the third closure thread forming mix is again injected by the injection ram 38.
• the product is again withdrawn from the dies after the die portions have been separated, and successive products are made in much the same way.
• the thread 37 is separated in halves by the cutting wheel 44 as shown in Fig 2B, leaving the left hand end of shank 39 remaining in the die space, and the process is repeated for successive products.
• the lower die portion 28 has a 'U' shaped cross- section slot, the side walls containing fibres against separation when pressing.
• This in turn enables a larger content of reinforcing fibre, and for example, the Applicant has been successful in producing a bar with glass fibres contributing more than 80% of the weight, and resin less than 20%.
• Such densely packed tows require low viscosity resin, and require high pressure to be imparted to cause resin flow between the fibres, and into die recesses.
• Use of filler is at least reduced, if not eliminated in such instances.
• Results are enhanced if some of the outer tows are of bulked rovings.
• Fig 4 illustrates to a larger scale the thread 37 with its higher elongation, higher strength resin content and its chopped strand fibre surrounding the bundle of tows 23. Since the thread is of larger pitch diameter and since it completely surrounds the bundle of tows 23, which otherwise set to form shank 39, if the composite plastic reinforcing bar is to be prestressed, the thread strength will be at least 45% of the ultimate tensile strength of the shank, since prestressing to 40% of the ultimate tensile stress is recommended.
• Fig 5 differs from the embodiment of Figs 2A, 2B and 3, in that the thread forming formation 46 is located centrally of the die assembly 47, and two rock bolts 48 may be moulded simultaneously, subsequently severed by wheels 44.
• the threads 49 and the shanks 50 are otherwise similar to what is shown in Figs 2A and 2B.
• Use is made of the cold clamping blocks 24 at the upstream end of the die assembly 47, and at the downstream end clamping blocks 41 are spring loaded by Bellville springs 43 as in the first described embodiment.
• the reinforcing bar which is illustrated in Figs 2A and 2B is provided with a plurality of protuberances 52, and these protuberances may be spaced for example 20 mm apart. In that instance, it is necessary for the length to be determined within a 20 mm pitch tolerance, but when the bar is embodied in concrete, protuberances 52 lock the bar for the entire length of the concrete. Thus it is desirable that some prestressing be imparted. Once the concrete has set, the load on the nuts is not excessively increased upon loading of the concrete because of the locking effect of the protuberances 52.
• the thread may be required to support a heavier load, and this can be imparted simply by increasing pitch diameter, increasing bulked roving content or both.
• Fig 6 is a larger scale representation of the upstream clamping blocks 24 and the insulating pad 25, and Figs 2a and 7 in addition show spring 43 at the downstream end, which retains high pressure notwithstanding expansion or contraction of the bundle of tows 23, upon heating and subsequent cooling.
• a turnbuckle on a reinforcing bar for example, of continuous threaded rod
• Fig 8 shows a turnbuckle nut 55 engaging a right hand thread 56 at the right hand side and the left hand thread 57 at the left hand side of respective moulded continuously threaded rods 58.
• a composite thermoset reinforcing bar is used in concrete, it is not feasible to bend the ends, as in the case of steel, and use may be made of the moulded flanged end member 60 which is illustrated in Fig 9, which is provided with retention hooks 61.
• Fig 10 illustrates a turnbuckle sleeve 62 which threadably engages right and left hand threads of respective hooks 63 for engaging upper and lower reinforcing rods 64 and 65.
• Fig 11 illustrates an alternative arrangement wherein a length of continuously threaded reinforcing bar 68 is cut to length and engages female threads in the hooks 69 for the same purpose.
• Tex is the weight of 1 kilometre of fibreglass, eg 4800 tex fibreglass weights 4.8 gms/metre, so that the replacement did not change the quantity of fibreglass in the bolt.
• Torque The bolt was placed in a custom built torque tester, which requires clamping the bolt by the flat sides at one end, the other end which clamped the bolt on the flat sides was free to rotate in ball bearings and incorporated a fixture to which a torque wrench is attached. The bolt was then twisted about the longitudinal axis until failure occurs. Results - A normal bolt with no bulked ravings withstood 50-56 ft/lb torque.
• the bulked roving increase the torque resistance by 3 ft/lbs per 6 strands of 2400 tex placed on the periphery of the bolt where it has the best effect.
• Each of the bolts prior to being subjected to the torque test was subjected to a tensile load where a nut was placed on the threaded section and placed in a universal tensile tester.
• Reinforcing bars and other elongate products can be produced in continuous lengths, with or without threads, and with unidirectional fibres. This can be achieved with short, fixed length dies.

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• Engineering & Computer Science (AREA)
• Architecture (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Moulding By Coating Moulds (AREA)

Priority Applications (3)

Applications Claiming Priority (1)

Publications (1)

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Country Status (3)

Cited By (9)

Citations (7)

• 1994
  • 1994-12-01 AU AU11882/95A patent/AU1188295A/en not_active Abandoned
  • 1994-12-01 WO PCT/AU1994/000749 patent/WO1996016792A1/en active Application Filing
• 1995
  • 1995-01-18 TW TW084100424A patent/TW283120B/zh active

Patent Citations (7)

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