AU639977B2

AU639977B2 - Corrosion resistant pc steel stranded cable and process of and apparatus for producing the same

Info

Publication number: AU639977B2
Application number: AU71205/91A
Authority: AU
Inventors: Takeshi Hasui
Original assignee: Hokkai Koki Co Ltd
Current assignee: Kurosawa Construction Co Ltd
Priority date: 1991-02-19
Filing date: 1991-02-19
Publication date: 1993-08-12
Anticipated expiration: 2011-02-19
Also published as: AU7120591A

Description

2

P

639977 S F Ref: 155313 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: I

I

Name and Address of Applicant: Address for Service: Hokkai Koki Co., Ltd 2-1, Nishi 2-chome Kita 1-jo, Chuo-ku Sapporo Hokkaido

JAPAN

14 Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Corrosion Resistant PC Steel Stranded Cable and Process of and Apparatus for Producing the Same The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3 ABSTRACT OF THE DISCLOSURE A corrosion resistant PC steel stranded cable for a pretensioning method wherein a core wire and a plurality of side wires are protected agai nst corrosion by coating with paint of a synthetic resin material while maintaining the cable in a stabilized stranded condition. The cable comprises a single core wire and a plurality of side wires disposed in a closely contacting relationship with each other and also with the core wire in such a manner as to define a plurality of spiral air gaps between the core wire and the side wires and also define a plurality of spiral recessed grooves between individual adjacent ones of the side wires on the outer side of the side wires. Each of the core wire and the side wires is processed by blueing in advance. Paint of a synthetic resin material is filled in the spiral air gaps, and a coating layer of paint of a synthetic resin material is formed substantially with a uniform thickness on an entire outer periphery of the side wires including the spiral recessed grooves. Also a process of and an apparatus for producing such corrosion resistant PC steel stranded cable are disclosed.

STA/168I 0A 2 BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a corrosion resistant PC steel stranded cable for use with a orestressed concrete structure and also to a process of and an apparatus for producing such corrosion resistant PC steel stranded cable.

I 2. Description of the Prior Art Conventionally, a high strength steel stranded cable is widely used as a PC steel element for applying prestress to concrete of a prestressed concrete structure in a pretensioning method or a posttensioning method.

A corrosion resistant PC steel stranded cable is already disclosed, for example, in Japanese Patent Laid-Open No. 130960/1984 (application No. 2011)/1983). Japanese Patent Publication No. 47609/1978 (applic-'on No. 165821/1971) or Japanese Utility Model Laid-Open i 15 No. 144121/1986 (application No. 26125/1985) which is obtained by applying suitable corrosion resisting processing to a high strength steel td stranded cable.

Referring to FIG. 17, there is shown a corrosion resistant PC steel stranded cable which is disclosed in Japanese Patent Laid-Open No. 130960/1984. The corrosion resistance PC steel stranded cable shown includes a bare PC steel stranded cable 10 composed of a plurality of side wires lOa and a core wire lOb, and a coating layer 11 of paint of a synthetic resin material such as an epoxy resin coated on an entire outer periphery of the bare PC steel stranded cable S" 25 In the corrosion resistant PC steel stranded cable 10F, a plurality of spiral air gaps 12 are defined between the side wires lOa and the core wire lOb and extend along a longitudinal direction of the corrosion resistant PC steel stranded cable 10F while a spiral recessed groove 13 is defined on the outside of and between each adjacent ones of the side wires lOa within the coating layer 11 and extends in the longitudinal direction of the corrosion resistant PC steel stranded cable 10F. In order to fill up such spiral recessed grooves 13 completely, it is paint coating layer 11, and if the synthetic resin paint coating layer 11 is so formed, then the thickness of a plurality of spiral recessed grooves 14 which are formed on an outer face of the synthetic resin paint coating layer 11 and extend in a longitudinal direction of the coating layer 11 will be decreased as much. In other words, the size of the spiral recess.ed grooves 14 is decreased.

STA/1684dI 3 Such corrosion resistant PC steel stranded cable O1F is adopted in a pretensioning method and mparts tensile force applied in advance thereto to concrete due to sticking thereof to the concrete. However, che corrosion resistant PC steel stranded cable lOF is disadvantageous in that such sticking force decreases as the size of the spiral recessed grooves 14 decreases and consequently introduction of prestress thereof into the concrete becomes insufficient.

Further, since the PC steel stranded cable 10OF has the spiral air gaps 12 therein, if the opposite longitudinal end faces are not enclo-ed perfectly, air or water may be admitted into and flow in the air gaps 12 and cause corrosion of the wires lOa and In addition, if the synthetic resin paint coating layer 11 should have a pin hole or should be damaged upon placing of concrete, then air or water may be admitted into the spiral air gaps 12 through the pin hole or damage of the synthetic resin paint coating layer 11 and may cause internal corrosion of the PC steel stranded cable FIG. 18 shows a corrosion resistant PC steel stranded cable disclosed in Japanese Patent Publication No. 47609/1978. Referring to FIG. 18, the corrosion resistance PC steel stranded cable O1G shown includes a bare PC steel stranded cable 10 having a similar construction to that of the bare PC steel stranded cable 10 shown in FIG. 17.

Lubricant 15 of the oil type which serves also as an anticorrosive is applied to a surface of the bare PC steel stranded cable 10, and a coating tube 16 of paint of a synthetic resin material is fitted around e" 25 the bare PC steel stranded cable The corrosion resistant PC steel stranded cable O1G is adopted in a posttensioning method and, after concrete is hardened, the corrosion resistant PC steel stranded cable O1G is strained and fixed to the concrete to provide prestress to the concrete. Nhen such prestress is to 30 be introduced, the sticking force to the concrete need not be called in question, but on the contrary the bare PC steel stranded cable 10 must necessarily be moved in its longitudinal direction with respect to the concrete.

The corrosion resistant PC steel stranded cable O1G is disadvantageous in that the lubricant 15 is deteriorated as time passes or the applied condition of the lubricant 15 likely becomes imperfect.

It is another disadvantage that, if the synthetic resin paint coating STA/1684d "'~sMllrrnra~; El"---aru~: -4tube 16 is damaged by some causes upon placing of concrete or the like, then the corrosion resisting property is deteriorated extremely.

A corrosion resistant PC steel stranded cable which eliminates such drawbacks of the corrosion resistant PC steel stranded cable O1G has been proposed and is shown in FIG. 21. Referring to FIG. 21, the improved corrosion resistant PC steel stranded cable 10J shown is similar in construction to the corrosion resistant PC steel stranded cable 10F shown in FIG. 17 in that an entire outer periphery of a bare PC steel stranded cable 10 is covered with a coating layer 17 of paint of a synthetic resin material such as an epoxy resin and a coating tube 18 of paint of a synthetic resin material is fitted around the synthetic resin paint coating layer 17 on the corrosion resistant PC steel stranded cable by protrusion molding.

However, the improved corrosion resistant PC steel stranded cable 10J is still disadvantageous in that, since a plurality of spiral air gaps 12 are formed between a plurality of side wires lOa and a core wire lOb similarly as in the corrosion resistant PC steel stranded cable of FIG. 17, air or water is likely admitted into the spiral air gaps 12 by way of openings of the longitudinal opposite end faces of the corrosion resistant PC steel stranded cable 10J or a pin hole or a damaged portion of the synthetic resin paint coating layer 17.

Meanwhile, Japanese Utility Model Laid-Open No. 114121/1986 discloses two different corrosion resistant PC steel stranded cables.

So One of the two corrosion resistant PC steel stranded cables is shown in 25 FIG. 19. Referring to FIG. 19, the corrosion resistant PC steel stranded cable 10H shown includes a coated PC steel stranded cable 10' composed of a plurality of side wires lOa and a core wire 10b which are each coated with a coating layer 22 of paint of a synthetic resin material and are stranded with one another. Lubricant 19 is applied to a surface of the coated PC steel stranded cable 10', and a coating tube 20 of paint of a synthetic resin material is fitted around the coated PC steel stranded cable FIG. 20 shows the other corrosion resistant PC steel stranded cable c disclosed in Japanese Utility Model Laid-Open No. 114121/1986. Referring 35 to FIG. 20, the corrosion resistant PC steel stranded cable 101 shown includes a coated PC steel stranded cable 10' of the similar construction t to that of the corrosion resistant PC steel stranded cable 10H, and a coating layer 21 of paint of a synthetic resin material is provided STA/1684dr 17 directly around an outer periphery of the coated PC steel stranded cable without applying lubricant to the coated PC steel stranded cable The corrosion resistant PC steel stranded cables 101- and 10I shown in FIGS. 19 and 20 are superior in corrosion resisting property because the side wires 10a and the core wire l0b are individually covered with the separate synthetic resin paint coating layers 22.

However, to thi s end, suich syntheti c resi n paint coati ng l ayers 22 must naturally be formed in advance on the side wires 10a and the core wire l0b before they are stranded with each other. However, due to presence of the synthetic resin paint coating layers 22, heat treatment necessary to remove residual stress after stranding operation, that is, blueing, cannot be performed.

Blueing is performed such that, after stranding operation of thle bare PC steel stranded cable 10, it is heated to about 400 0 C to remove residual stress after working to stabilize the stranded condition of the bare PC steel stranded cable 10. If such blueing is not performed, thu-n a problem will arise that, each time the bare PC steel stranded cable is Cut inito a segment of a r-equi red length, the strand or twi st of the bare PC steel stranded cable will be loosened or cancelled from a thus cut end portion of the bare PC steel stranded cable.

Even if it is tried to conduct suitable working in or-der to maintain the strand or twist without performing blueing, this is accompanied by extreme difficulty, and besides, upon such working, there is the possibility that the synthetic resin paint coating layer 22 may be Thus, it is a disadvantage that an anticipated corrosion 3 resisting effect cannot be maintained.

4 SUMMARY( OF THE INVENTION It is an object of the present invention to provide a corrosion resistant PC steel stranded cable that ameliorates or substantially overcomes the above-mentioned disadvantages of the prior art.

In order to attain that object, accor-ding to one aspect of the present invention ther-e is provided a corrosion resistant PC steel stranded cable, comprising a single core wire, a plurality of side wires disposed in a closely contacting relationship with each other and also with said core wire in such a manner as to define a plurality of spiral air gaps between said core wire and said side wires and also define a plurality of spiral recessed grooves between individual adjacent ones of STA/1584d r 6said side wires on the outer side of said side wires, each of said core wire and said side wires being processed by blueing in advance so that said side wires individually retain a twisted habit, paint of a synthetic resin material filled in said spiral air gaps, and a coating layer of paint of a synthetic resin material formed substantially with a uniform thickness on an entire outer periphery of said side wires including said spiral recessed grooves.

An outer periphery of the synthetic resin paint coating layer may further be coated with another coating layer of paint of a synthetic resin material formed in a closely contacting relationship thereon in order to improve the corrosion resisting property and the strength of the corrosion resistant PC steel stranded cable.

A fatty substance may be applied to an outer periphery of the synthetic resin paint coating layer and another synthetic resin paint coating layer is fitted around the fatty substance to coat the latter.

The corrosion resistant PC steel stranded cable is suitable for use in a posttensioning method. With the corrosion resistant PC steel stranded cable, the corrosion resisting effect is improved significantly since the additional synthetic resin paint coating layer is fitted around the first-mentioned synthetic resin paint coating layer.

According to another aspect of the present invention, there is provided a corrosion resistant PC steel stranded cable, comprising a core wire, a plurality of side wires, each of said core wire and said side wires being processed by blueing in advance so that said side wires 25 individually retain a twisted habit, and a coating layer of paint of a synthetic resin formed on an entire outer periphery of each of said core wire and said side wires, said side wires being disposed in a closely contacting relationship with each other and also with said core wire by o way of said synthetic resin paint coating layers thereon in such a manner as to define a plurality of spiral air gaps between said synthetic resin paint coating layers on said core wire and said side wires and also to define a plurality of spiral recessed grooves between said synthetic resin paint coating layers on individual adjacent ones of said side wires on the outer side of said side wires.

35 A fatty substance may be applied to outer peripheries of the synthetic resin paint coating layers on the side wires, and a coating tube of paint of a synthetic resin material is fitted around the fatty substance to coat the latter. The corrosion resistant PC steel stranded L A* 1 684d, STA/l64 o 7 -7cable is suitable for use in a posttensioning method. With the corrosion resistant PC steel stranded cable, similarly the corrosion resisting effect is improved significantly.

According to a further aspect of the present invention, there is provided a process of producing a corrosion resistant PC steel strand cable from a bare PC steel stranded cable consisting of a core wire and a plurality of side wires disposed in a closely contacting relationship with each other and also with the core wire, each of the core wire and the side wires being processed by blueing in advance so that said sic'.

wires individually retain a twisted habit, the process comprising the steps of continuously untwisting the bare PC steel stranded cable over a predetermined length within an elastic limit within which the twisted habit of the side wires is maintained thereby to bring the side wires anu the core wire out of the closely contacting relationship, applying paint of a synthetic resin material to the core wire and the side wires of the untwisted portion of the bare PC steel stranded cable to coat the core wire and the side wires individually with coatings of the synthetic resin paint, and twisting the side wires around the core wire of thk untwisted portion of the bare PC steel stranded cable again.

The synthetic resin paint for coating the side wires and the core wire may be filled, at the twisting step, as synthetic resin paint in a plurality of spiral air gaps defined between the core wire and the side 'ires and also be coated as a synthetic resin paint coating layer of a substantially uniform thickness on an entire outer periphery of the stranded cables including a plurality of spiral recessed grooves formed between individual adjacent ones of the stranded cables outside the stranded cables.

Alternatively, the synthetic resin paint for coating the side wires o a and the core wire may be formed, at the twisting step, as synthetic resin paint coating layers individually for the side wires and the core wire so S as to define a plurality of spiral air gaps between the core wire and the side wires and also define a plurality of spiral recessed grooves between individual adjacent ones of the stranded cables outside the stranded cables.

S, 35 Otherwise, the producing process may further comprise the step of coating, after the twisting step, another coating layer of paint of a S^,J 1 synthetic resin material in a closely contacting relationship on an outer periphery of the synthetic resin paint coating layer on the side wires.

STA/1684d h 8- Or else, the producing process may further comprise the steps of applying, after the twisting step, a fatty substance to an outer periphery of the synthetic resin paint coating layer or layers on the side wires and fi ttinrg a coatinrg tube of pai nt of a synthetic res in aro~ id the fatty substance by extrursion molding to coat the fatty Substance with the coating tube.

Accordinrg to a still further aspect of the present invention, there is provided an apparatus an apparatus for producing a corrosion resisting PC steel stranded cable, comprising a supplying device for supplying therefrom a bare PC steel stranded cable which cons ists of a core wire arid a plurality of side wires disposed in a closely contacting rel ationsip with each other and also with the core wire, each of the core wire arid the side wires being processed by blueing in advance so that said side aires inrdividural ly retain a twi sted habitC, an untwi sting device for conti nuoi.''ly untwi stinrg, over a predetermi ned 1lengthi, thle bare PC steel stranded cable supplied from said supplying device within an elastic limit within which the twisted habit of the side wires is mainrtai ned thereby to space the side wi res and the core wire away from each other, a powder paint applying device for applying paint of a synthetic resin material to the thus spaced core wire and side wires of the untwi sted portion of the predetermined length of the bare PC steel stranded cable to coat the core wire and the side wires with the synthetic resin paint to obtain a corrosion resisting PC steel stranded cable, the corrosion resisting PC steel stranded cable automatically 25 restoring the twisted condition of the bare PC steel stranded cable in( wrafebenfeoufrmsipodrpitapyndeie anwhich the side wires contact closely with each other and with the core takeup device for winding the corrosion resistant PC steei stranded cable thereon, said supplying device, said untwisting device, said powder paintal applying device and said takeup device being disposed Successively in 4 this order.

The producing apparatus may further comprise a second powder paint applying device interposed between the first-mentioned powder paint applying device and the takeup device for applying paint of a synthetic resin material to an outer periphery of the synthetic resin paint of thle corrosion resisting PC steel stranded cable 6a ter the corrosion resisting PC steel stranded cable is twisted again.

STA/1684 ^r i i j- -9- Alternatively, the producing apparatus may further comprise a fatty substance applying device for applying a fatty substance to an outer periphery of the corrosion resisting PC steel stranded cable after the corrosion resisting PC steel stranded cable is twisted again, and a protrusion molding machine for fitting a coating tube of paint of a synthetic resin material around an outer periphery of the fatty substance applied to the corrosion resisting PC steel stranded cable so as to coat the corrosion resisting PC steel stranded cable.

Nith the process and apparatus of the present invention, a corrosion resistant PC steel stranded cable according to the present invention can be produced readily with certainty.

The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRANINGS FIG. 1 is a cross sectional view of a corrosion resistant PC steel strand cable to which the present invention is applied; FIG. 2 is a cross sectional view of another corrosion resistant PC steel strand cable to which the present invention is applied; FIG. 3 is a schematic view showing construction of an apparatus for producing a corrosion resistant PC steel strand to which the present invention is applied; FIG. 4 is a sectional view of an untwisting device of the ar-,ratus of FIG. 3; 25 FIGS. 5 and 6 are a front elevational view and a sectional view, respectively, of an untwisting guide plate of the untwisting device of FIG. 4; or a O r a a FIG. 7 is a schematic partial sectional view of a powder paint applying device of the apparatus of FIG. 3; FIG. 8 is a side elevational view showing an end portion of a bare PC steel stranded cable in an untwisted condition; FIG. 9 is a side elevational view showing a retwisted portion at an end portion of a bare PC steel stranded cable which is fitted in the untwisting guide plate of FIGS. 5 and 6 and fixedly connected to a leading wire; FIG. 10 is a cross sectional view of a bare PC steel stranded rc-ble; STA/1684d Ac'r S020047 19/02/91 5845/2 10 FIG. 11 is a cross sectional view of an untwisted portion of the bare PC steel stranded cable of FIG. 10 to which paint of a synthetic resin is applied; FIG. 12 is a cross sectional view of a further corrosion resistant PC steel stranded cable to which the present invention is applied; FIG. 13 is a schematic view showing construction of another apparatus for producing a corrosion resistant PC steel stranded ,uble to which the present invention is applied; FIG. 14 is a cross sectional view of a still further corrosion resistant PC steel stranded cable to which the present Invention is applied; FIG. 15 is a similar view but showing a yet further corrosion resistant PC steel stranded cable to which the present invention is applied; FIG. 16 is a schematic view showing construction of a further apparatus for producing a corrosion resistant PC steel stranded cable to which the present invention is applied; and FIGS. 17 to 21 are cross sectional views individually showing different conventional corrosion resistant PC steel stranded cables.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, there is shown a corrosion resistant PC steel stranded cable to which the present invention is applied. The corrosion resistant PC steel stranded cable 10A shown includes a plurality of, six in FIG. 1, side wires 10a and a single core wire 25 The side wires 10a are disposed in a closely contacting relationship with each other and also with an outer periphery of the core wire 10b. I Paint 23 of a synthetic resin material such as polyethylene or an epoxy resin is filled up in a plurality of spiral gaps 24 defined between c, the core wire 10b and the side wires lOa and extending in a longitudinal direction of the corrosion resistant PC steel stranded cable Meanwhile, a coating layer 25 similarly made of a synthetic resin material such as polyethylene or an epoxy resin is coated on an entire outer periphery, that is, externally exposed faces of the strand wires Sl0a including externally directed spiral recessed grooves 26 which are 35 formed individual mutually adjacent ones of the side wires 10a and extend j *in the longitudinal direction thereof.

i 1 t 16 T STA/1684d I 3 I .e f 1 IKN: 155313 INSTR CODE: 55135 STA/1709d 11 Predetermined blueing is performed for the side wires lOb and the core wire lOb of the corrosion resistant PC steel stranded cable before the synthetic resin paint 23 is filled up in the spiral air gaps 24 and the synthetic resin paint coating layer 25 is formed on the entire outer periphery of the corrosion resistant PC steel stranded cable 1OA including the spiral recessed grooves 26.

Nith the corrosion resistant PC steel stranded cable 10A, since the predetermined blueing is performed as described above, a stabilized stranded condition is maintained.

Further, all of the side wires 1Oa and the core wire lOb are covered over the entire faces thereof with the synthetic resin material, and accordingly, the corrosion resistant PC steel stranded cable 10A has a sufficiently high corrosion resisting property.

In addition, since the spiral recessed grooves 26 of the outer periphery of the corrosion resistant PC steel stranded cable 10A is comparatively great in size and consequently the sticking force thereof to concrete is great, introduction of sufficient prestress to concrete can be achieved.

Referring now to FIG. 2, there is shown another corrosion resistant PC steel stranded cable to which the present invention is applied. The corrosion resistant PC steel stranded cable 10B shown includes a plurality of side wires 1Oa and a single core wire 10b. Each of the side wires 10a and the core wire 10b is coated with an independent coating layer 27 of paint of a synthetic resin material such as polyethylene or 25 an epoxy resin.

The side wires 1Oa are disposed in a closely contacting relationship with each other and also with an outer periphery of the single core wire 10b by way of the individual synthetic resin paint S coating layers 27 thereof.

A plurality of spiral air gaps 28 are formed between the core wire and the side wires 10a, or more accurately, between the synthetic resin paint coating layers 27 on the core wire 10b and the side wires and extend in a longitudinal direction of the corrosion resistant PC steel stranded cable 10B. Meanwhile, a plurality of outwardly directed spiral recessed grooves 29 are formed between individual adjacent ones of the stranded cables lOa, or more accurately, between the synthetic resin STA/1684d 3 synthetic resin formed on an entire outer periphery of each of said core wire and said side wires, said side wires being disposed in a closely contacting relationship with each other and also with said core wire by vway of said synthetic resin paint coating layers thereon, in such a manner S. ./2 12 paint coating layers 27 on individual adjacent ones of the stranded cables 10a and extend in the longitudinal direction of the corrosion resistant PC steel stranded cable Predetermined blueing is performed for the side wires 10a and the core wire 10b of the corrosion resistant PC steel stranded cable before the synthetic resin paint coating layers 27 are formed on them.

The corrosion resistant PC steel stranded cable 10B is different from the corrosion resistant PC steel stranded cable 10A shown in FIG. 1 in that it has the spiral air gaps 28 in the inside thereof and the side wires lOa are not directly contacted with the core wire 10b, that is, the side wires 10a and the core wire 10b are held in a closely contacting relationship with each other by way of the synthetic resin paint coating layers 27 individually coated on the side wires 10a and the core wire However, the corrosion resistant PC steel 24 stranded cable 10B is advantageous, similarly to the corrosion resistant PC steel stranded cable 10A shown in FIG. 1, in that, since predetermined blueing is performed, a stabilized stranded condition is maintained, and since the side wires 10a and the core wire 10b are all coated over the entire outer peripheries thereof with the synthetic resin paint, it exhibits a sufficiently high corrosion resisting property, and besides since the comparatively great spiral recessed grooves 29 are formed on the outer periphery of the corrosion resistant PC steel stranded cable 10B, the sticking force to concrete is great.

It is to be specifically noted that, since the corrosion resistant 25 PC steel stranded cable 10B has the spiral air gaps 28 in the inside thereof, it is superior in flexibility to the corrosion resistant PC steel stranded cable 10A shown in FIG. 1, and accordingly, it is improved in operability as much.

Subsequently, a process of and an apparatus for producing such corrosion resistant PC steel stranded cable O1A or 10B according to the present invention will be described with reference to FIGS. 3 to 11.

Referring first to FIG. 3, there is shown general construction of an apparatus for producing a corrosion resistant PC steel stranded cable.

The apparatus shown includes a supplying device 31 for supporting a S 35 bobbin 32 for rotation thereon and supplying a bare PC steel stranded i :cable 10 from the bobbin 32 thereof. The bare PC steel stranded cable k STA/1684 r 13 is wound in advance around the bobbin 32 and is composed of, as shown in FIG. 10, a single core wire 10b and a plurality of side wires stranded around the core wire The stranded cable producing apparatus further includes a feeding device 33 including a pair of driving endless belts 33a and 33b disposed in a mutually contacting relationship at upper and lower locations so that the bare PC steel stranded cable 10 drawn out from the supplying device 31 may be held therebetween and compulsorily fed into a sticking substance removing device 34.

The sticking substance removing device 34 may be a shot blast wherein very small steel balls or steel pieces or the like are blasted to a surface of the bare PC steel stranded cable 10 to remove sticking foreign substances such as oil from the bare PC steel stranded cable The bare PC steel stranded cable 10 is then fed into a front stage heating device 35 which may be a high frequency induction heating device and heats the bare PC steel stranded cable 10 to a temperature necessary for powder coating at a subsequent stage.

The bare PC steel stranded cable 10 is thereafter fed into an untwisting device 36 by which it is untwisted to separate the side wires 10a and the core wire 10b from one another.

Referring to FIG. 4, the untwisting device 36 includes a rotary tubular body 38 supported for rotation on a base 37 and an untwisting guide plate 39 mounted on the rotary tubular body 38. The untwisting I 2 guide plate 39 is rotated by a motor 41 by way of a chain 25 Referring to FIGS. 5 and 6, the untwisting guide plate 39 includes a core wire guide tube 42 and a chain wheel 44 extending Icircumferentially around the core wire guide tube 42 and connected to the core wire guide tube 42 by way of a plurality of stays or radial elements defining sectoral side wire guide holes 43 between them.

Referring back to FIG. 3, the bare PC steel stranded cable 10 is t- subsequently fed into a powder paint applying device 45. Referring now to FIG. 7, the powder paint applying device 45 includes a spray booth 46 into which an untwisted portion lOc of the bare PC steel stranded cable is introduced, and three spray guns 47 which spray powder paint of a I 35 synthetic resin material in three directions toward the untwisted portion lOc of the bare PC steel stranded cable 10 together with air.

SSTA/1684d STA/1684d'i *K 5845/3 14 Referring back again to FIG. 3, the bare PC steel stranded cable is subsequently fed into a rear stage heading device 48 for which an infrared lamp may be employed, and then into a water or air cooling device 49 in which the bare PC steel stranded cable 10 to which synthetic resin powder paint has been applied is cooled to a normal room temperature.

The bare PC steel stranded cable 10 is then fed into a drawing out device 50 by which it is compulsorily drawn out forwardly. The drawing out device 50 includes a pair of driving endless belts 50a and disposed in a mutually contacting relationship at upper and lower locations for holding therebetween and compulsorily drawing out forwardly the bare PC steel stranded cable 10 with synthetic resin powder paint applied thereto, that is, such a corrosion resistant PC steel stranded cable 10A or 106 as described hereinabove.

The bare PC steel stranded cable 10, that is, the corrosion resistant PC steel stranded cable O1A or 10B for which corrosion resisting processing has been completed, is fed into a takeup device 51 in which a bobbin 52 is driven to rotate so that the bare PC steel stranded cable 10 is wound onto the bobbin 52.

The stranded cable producing apparatus further includes a leading wire takeup device 53 for a preparatory operation.

Description will subsequently be given of a producing process of the present invention which is performed using the stranded cable producing apparatus described above.

First, a leading end of a bare PC steel stranded cable 10 is forwarded from the supplying device 31 and threaded between the endless .t belts 33a and 33b of thile feeding device 33 and then through the sticking substance removing device 34 and the front stage heating device 35 into the untwisting device 36.

The bare PC steel stranded cable 10 is produced in a well known, popular method such that a plurality of side wires lOa are stranded around a single core wire lOb such that a spiral recessed groove 26 is formed between each adjacent ones of the side wires lOa and extends in a I longitudinal direction of the bare PC stranded cable 10 and they are processed by predetermined blueing.

i STA/684d i t Z1 15 Before the bare PC steel stranded cable 10 is fed into the untwisting device 36, a leading end portion thereof is untwisted over a required length L to separate the side wires I0a and core wire 10b at the leading end portion from each other by manual operation, and the thus separated side wires 10a are threaded into the side wire guide holes 43 of the untwisting guide plate 39 while the core wire 10b is threaded into the core wire guide tube 42 of the untwisting guide plate 39.

After then, leading end portions of the side wires 10a at the untwisted portion of the bare PC steel stranded cable 10 are twisted or stranded again around the core wire 1Ob as shown in FIG. 9 by manual operation. Such stranding can be performed readily without much labor because each of the side wires 10a is in a permanently deformed or twisted condition.

Subsequently, a leading wire 54 is securely connected to the thus re-twisted end portion of the bare PC steel stranded cable 10 by suitable means as shown in FIG. 9. The leading wire 54 is threaded through the powder paint applying device 45, rear stage heating device 48, cooling device 59 and drawing out device 50 and wound around the leading wire takeup device 53.

Continuous operation of the producing apparatus will be started in this condition. Then, the bare PC steel stranded cable 10 is continuously supplied from the supplying device 31 into the feeding device 33 and then fed through the various devices described above so that predetermined S. corrosion resistant processing is applied thereto, whereafter it is drawn 25 out by the drawing out device Then, after a portion of the bare PC steel stranded cable 10 to which corrosion resistant processing has been performed completely is drawn out to the outside of the drawn out device 50, a leading end S portion of the bare PC steel stranded cable 10 to which corrosion resistant processing has not been performed completely is cut off and S l removed from the bare PC steel stranded cabtle 10, and a succeeding portion of the bare PC steel stranded cable 10 which is successively drawn out from the drawing out device 50, that is, the corrosion resistant PC steel stranded cable O1A or 10B, is wound onto the bobbin 52 of the takeup device 51.

Subsequently, the corrosion resistant processing step will be described in detail.

S' STA/1684d[ 16 The bare PC steel stranded cable 10 is fed in its axial direction, that is, in its longitudinal direction while it is prevented from rotation around its axis by the feeding device 33 and the drawing out device At the front stage heating device 35, the bare PC steel stranded cable 10 is heated to such a degree that a required temperature is assured to melt synthetic resin powder paint when such synthetic resin powder paint is applied to the bare PC steel stranded cable subsequently by the powder pain applying device The bare PC steel stranded cable 10 in a thus heated condition is subsequently fed into the untwisting device 36. In the untwisting device 36, the untwisting guide plate 39 is rotated in accordance with a strand pitch of the bare PC steel stranded cable 10 in a predetermined direction by the motor 41 so that the bare PC steel stranded cable 10 is untwisted always over a length equal to the length L over which a leading end portion thereof has been untwisted to separate the side wires lOa and core wire lOb thereof from each other upon initial threading thereof as described hereinabove. However, the thus untwisted portion of the bare PC steel stranded cable 10 is automatically twisted or stranded again after it is fed over the length L. The length L is set in advance to a value with which the untwisted condition of the bare PC steel stranded cable is maintained for a required period of time after synthetic resin powder paint which will be described below is sprayed thereto.

The bare PC steel stranded cable 10 in the thus untwisted condition is subsequently fed into the spray booth 46 of the powder paint applying device 45, in which powder paint of a synthetic resin material such as polyethylene or an epoxy resin which is charged with negative charge is sprayed toward the bare PC steel stranded cable 10 from the spray guns 47. The thus sprayed synthetic resin powder paint sticks to surfaces of the side wires lOa and core wire lOb of the bare PC steel stranded cable t 1 10 to which negative charge has been applied at the untwisting device 3E.

The synthetic resin powder paint is then melted by the side wires 10a ar i t Icore wire lOb of the bare PC steel stranded cable 10, thereby forming a synthetic resin paint coating 9 on each of the side wires 10a and core I 35 wire lOb as seen in FIG. 11.

i c STA/1684d 1.

W

17 As the bare PC steel stranded cable 10 is fed, the untwi sted portion 10c thereof is brought into a twi sted or stranded cl-,dition again whil1e the synthetic resin forming the synthetic resin pai nt coating 9 remains in a nmolten condition, that is, before the synthetic resin becomes hardened. Consequently, the synthetic resin of the synthetic resin paint coating 9 is deformed so that it fills up the radial air gaps 24 between the side wires 10a arid the core wire l0b as in the corrosion resistant PC steel stranded cable 10A shown in FIG. 1 while it also makes such a synthetic resin paint coating layer as the synthetic resin paint coating layer 25 shown in FIG. 1 which covers an entire outer periphery of the side wires 10a including the spiral recessed grooves 26 between the side wires After then, the synthetic resini painit co~ti ig layer 25 is heated again in the rear stage heading device 48 to put a surface thereof in good order and is then cooled in the cooling device 49 together with the synthetic resin paint 23 so that it is hardened, thereby obtaining such corrosion resistant PC steel stranded cable 10A as shown in FIG. 1.

The corrosion resisting PC steel strand cable bOA is wound up onto the bobbin 52 of the takeup device 51 by way of the drawing olt device In production of the corrosion resisting PC steel strani udble lOA described above, if the time until the untwisted portion 10c of the bare PC steel stranded cable 10 is brought into a twisted condition again by J feeding of the bare PC steel stranded cable 10 after the synthetic resin paint coatings 9 are formed on the surfaces of the side wires 10a arid the cor-e wire l0b (refer to FIG. 11) is set to a comparatively great value, or if the required length L described above is set to a comparatively great value in advance, then such corrosion resisting PC steel stranded cable 108 as shown in FIG. 2 can be produced by forming the synthetic resin paint coatings 9 as synthetic resin paint coating layers 27 which are independent of each other for the side wires l~a and the core wire l0b as shown in FIG. 2 and then by causing the synthetic resin paint coating layers 27 to be hardened in the cooling device 49.

It is to be noted that the rear stage heating device 48 is not necessarily provided depending upon a type of the synthetic resin powder IL 35 paint.9

C

Zt I C11 STA/1684d includes a coated PC steel stranded cable 10' of the similar construction .to that of the corrosion resistant PC steel stranded cable 10H, and a coating layer 21 of paint of a synthetic resin material is provided STA/1684d, ;i;2 18 Further, while the producing process described above employs a powder coating method based on an electrostatic method wherein positive and negative charges are applied to the bare PC steel strand cable 10 and powder paint, respectively, to cause the powder paint to stick to the bare PC steel strand cable 10 due to electrostatic force, a powder coating method may alternatively be employed which depends upon a fluid dipping method wherein the bare PC steel strand cable 10 is heated in advance and fluid powder paint is baked so as to stick to the bare PC steel strand cable Referring now to FIG. 12, there is shown a further corrosion resistant PC steel stranded cable to which the present invention is applied. The corrosion resistant PC steel stranded cable O1C shown is constructed as a corrosion resistant PC steel stranded cable for the pretensioning and corresponds to a modification to the corrosion resistant PC steel stranded cable !OA described hereinabove with reference to FIG. 1 in that another coating layer 30 of paint of a synthetic resin material such as polyethylene or an epoxy resin is formed in a closely contacting relationship on an outer periphery of the synthetic resin paint coating layer 25 which covers the entire outer periphery of the side wires lOa of the corrosion resistant PC steel stranded cable In order to produce the corrosion resistant PC steel stranded cable such a producing apparatus as shown in FIG. 13 is used. The f, ^producing apparatus shown in FIG. 13 corresponds to a modification to the i 1 25 producing apparatus shown in FIG. 3 in that another powder paint applying device 55 for a secondary coating is provided between the powder paint applying device 45 and the rear stage heating device 48.

Then, the corrosion resistant PC steel stranded cable O1C can be produced by forming, by the powder paint applying device 55, the synthetic resin paint coating layer 30 in a closely contacting relationship on an outer periphery of the synthetic resin paint coating layer 25 which is formed in a similar manner as in production of the corrosion resistant PC steel stranded cable The corrosion resistant PC steel stranded cable 10C produced in this manner is apparently superior in corrosion resisting property, strength and so forth further to the corrosion resistant PC steel 1 stranded cable 10A described hereinabove.

SC t STA/ I684d 1

B

19- FIGS. 14 and 15 show still further corrosion resistant PC steel stranded cables to which the present invention is applied. The corrosion res'stant PC steel stranded cables are constructed for corrosion resistant PC steel stranded cables for the posttensioning.

Referring first to FIG. 14, the corrosion resistant PC steel stranded cable O1D shown corresponds to a modification to the corrosion resistant PC steel stranded cable 10A described hereinabove in that a fatty substance 56 is applied to an outer face of the synthetic resin paint applying layer 25 on the outer periphery of the corrosion resistant PC steel stranded cable 10A and a coating tube 57 of a synthetic resin material is fitted around the fatty substance 56.

Meanwhile, the corrosion resistant PC steel stranded cable shown in FIG. 15 corresponds to a modification to the corrosion resistant PC steel stranded cable 10B shown in FIG. 2 in that a fatty substance 56 is applied to an outer periphery of the synthetic resin paint coating layer 27 which covers the outer periphery of the corrosion resistant PC steel stranded cable 10B, that is, the side wires lOa, and a coating tube 57 of a synthetic resin material is fitted around the fatty substance 56 similarly as in the corrosion resistant PC steel stranded cable In producing the corrosion resistant PC steel stranded cables 1OD and 10E, a producing apparatus shown in FIG. 16 is employed. The I E producing apparatus shown corresponds to a modification to the producing apparatus shown in FIG. 3 in that a fatty substance applying device 58, a protrusion molding machine 59 and a water or air cooling device 60 are "o 25 disposed between the cooling device 49 and the drawing out device WWith the producing apparatus, the corrosion resistant PC steel stranded cable 10D or O1E can be produced such that the fatty substance S 56 is applied, by the fatty substance applying device 58, to the outer periphery of the synthetic resin paint coating layer 25 or 27 formed similarly as in production of the corrosion resistant PC steel stranded *cable O1A or 10B, and after then, the synthetic resin coating tube 57 is protruded to fit around the fatty substance 56 by the protrusion molding i machine 59.

^Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit and scope of the invention as set forth herein.

A: "6 f STA/1684d'

Claims

1. A corrosion resistant PC steel stranded cable, comprising a single core wire, a plurality of side wires disposed in a closely contacting relationship with each other and also with said core wire in such a manner as to define a plurality of spiral air gaps between said core wire and said side wires and also define a plurality of spiral recessed grooves between individual adjacent ones of said side wires on the outer side of said side wires, each of said core wire and said side wires being processed by blueing in advance so that said side wires individually retain a twisted habit, paint of a synthetic resin material filled in said spiral air gaps, and a coating layer of paint of a synthetic resin material formed substantially with a uniform thickness on an entire outer periphery of said side wires including said spiral recessed grooves.

2. A corrosion resistant PC steel stranded cable as claimed in claim 1, wherein an outer periphery of said synthetic resin paint coating layer is further coated with another coating layer of paint of a synthetic resin material formed in a closely contacting relationship thereon.

3. A corrosion resistant PC steel stranded cable as claimed in claim 1, wherein a fatty substance is applied to an outer periphery of said synthetic resin paint coating layer and another synthetic resin paint coating layer is fitted around said fatty substance to coat the latter.

4. A corrosion resistant PC steel stranded cable, comprising core wire, a plurality of side wires, each of said core wire and said side wires being processed by blueing in advance so that said side wires individually retain a twisted habit, and a coating layer of paint of a synthetic resin formed on an entire outer periphery of each of said core wire and said side wires, said side wires being disposed in a closely contacting relationship with each other and also with said core wire by way of said synthetic resin paint coating layers thereon in such a manner as to define a plurality of spira., air gaps between said synthetic resin paint coating layers on said core wire and said side wires and also to define a plurality of spiral recessed grooves between said synthetic resin paint coating layers on individual adjacent ones of said side wires on the outer side of said side wires. STA/1684d N. aL-~: 21 A corrosion resistant PC steel stranded cable as claimed in claim 4, wherein a fatty substance is applied to outer peripheries of said synthetic resin paint coating layers on said side wires after said side wires have been brought back into contact with said core wire, and a coating tube of paint of a synthetic resin material is fitted around said fatty substance to coat the latter.

6. A process of producing a corrosion resistant PC steel strand cable from a bare PC steel stranded cable consisting of a core wire and a plurality of side wires disposed in a closely contacting relationship with each other and also with the core wire, each of the core wire and the side wires being processed by blueing in advance so that said side wires individually retain a twisted habit, the process comprising the steps of continuously untwisting the bare PC steel stranded cable over a predetermined le- within an elastic limit within which the twisted habit of the sidL cs is maintained thereby to bring the side wires and the core wire out of the closely contacting relationship, applying paint of a synthetic resin material to the core wire and the side wires of the untwisted portion of the bare PC steel stranded cable to coat the core paint, and twisting the side wires around the core wire of the untwisted portion of the bare PC steel stranded cable again.

7. A process of producing a corrosion resistant PC i steel strand cable as claimed in claim 6, wherein the synthetic resin paint for coating the side wires and the core wire is filled, at the twisting step, as synthetic resin paint in a plurality of spiral air gaps defined between the core wire and the side wires and also is coated as a J synthetic resin paint coating layer of a substantially uniform thickness on an entire outer periphery of the stranded cables including a plurality of spiral recessed grooves formed between individual adjacent ones of the stranded cables outside the stranded cables.

8. A process of producing a corrosion resistant PC steel striand cable as claimed in claim 6, wherein the synthetic resin paint for coating the side wires and the core wire is formed, at the twisting step, as synthetic resin paint coating layers individually for the side wires and the core wire so as to define a plurality of spiral air gaps between the core wire and the side wires and also define a plurality of spiral recessed grooves between individual adjacent ones of the stranded cables outside the stranded cables. L TA/1684d I: 22

9. A process of producing a corrosion resistant PC steel stranded cable as claimed in claim 7, Further comprising the step of coating, after the twisting step, another coating layer of paint of a synthetic resin material in a ciosely contacting relationship on an outer periphery of the synthetic resin paint coating layer on the side wires. A process of producing a corrosion resistant PC steel stranded cable as claimed in claim 7 or 8, further comprising the steps of applying, after the twisting step, a fatty substance to an outer periphery of the synthetic resin paint coating layer or layers on the side wires and fitting a coating tube of paint of a synthetic resin around the fatty substance by extrusion molding to coat the fatty substance with the coating tube.

11. An apparatus for producing a corrosion resisting PC steel stranded cable, comprising a supplying device for supplying therefrom a bare PC steel stranded cable which consists of a core wire and a plurality of side wires disposed in a closely contacting relationship with each other and also withi the core wire, each of the core wire and the side wires being processed by blueing in advance so that said side wires individually retain a twisted habit, an untwisting device for continuously untwisting, over a predetermined length, the bare PC steel stranded cable supplied from said supplying device within an elastic limit within which the twisted habit of the side wires is maintained thereby to space the side wires and the core wire away from each other, a powder paint applying device for applying paint of a synthetic resin material to the thus spaced core wire and side wires of the untwisted portion of the predetermined length of the bare PC steel stranded caole to coat the core wire and the side wires with the synthetic resin paint to obtain a corrosion resisting PC steel stranded cable, the corrosion resisting PC steel stranded cable automatically restoring the twisted condition of the bare PC steel stranded cable in which the side wires contact closely with each other and with the core wire after being fed out from said powder paint applying device, and a takeup device for winding the corrosion resistant PC steel stranded cable thereon, said supplying device, said untwisting 'evice, said powder paint applying device and said takeup device b;-ing disposed successively in this order. t. tt t r 4t 4 4( 1 44 4 C 4I Cl 4 C C' 684d I^ :1 i 23

12. An apparatus for producing a corrosion resisting PC steel stranded cable as claimed in claim 11, further comprising a second powder paint applying device interposed between said first-mentioned powder paint applying device and said takeup device for applying paint of a synthetic resin material to an outer periphery of the synthetic resin paint of the corrosion resisting PC steel stranded cable after the corrosion resisting PC steel stranded cable is twisted again.

13. An apparatus for producing a corrosion resisting PC steel stranded cable as claimed in claim 11, further comprising a fatty substance applying device for applying a fatty substance to an outer periphery of the corrosion resisting PC steel stranded cable after the corrosion resisting PC steel stranded cable is twisted again, and a protrusion molding machine for fitting a coating tube of paint of a synthetic resin material around an outer periphery of the fatty substance applied to the corrosion resisting PC steel stranded cable so as to coat the corrosion resisting PC steel stranded cable.

14. A corrosion resistant PC steel stranded cable substantially as hereinbefore described with reference to Figures 1 to 16. A process of producing a corrosion resistant PC steel strand cable from a bare PC steel stranded cable substantially as .ereinbefore described with reference to Figures 1 to 16.

16. An apparatus for producing a corrosion resisting PC steel stranded cable substantially as hereinbefore described with reference to Figures 1 to 16. DATED this FOURTH day of MAY 1993 Hokkai Koki Co., Ltd. Patent Attorneys for the Applicant SPRUSON FERGUSON V I yS"TA/1684d