Rope for operating

Abstract: A rope comprising a pluraliry of wires 2, 3, 4 made of a steel wire being twisted together; at least the wires (for instance, the wires 4 in the second layer) which are arranged in such a manner as to be disposed on an outer surface of the rope 1 being made of a plated steel wire (e.g. zinc-aluminum alloy plated steel wire) wherein a corrosion resistance is superior; at least said wires (for instance, the core wire 2 and the wires in the first layer) which are located in a center of the rope not being made of the wire wherein the corrosion resistance is superior, thereby the cost for producing the rope is remarkably reduced without damaging the corrosion resistance and the endurance property.

Description: The present invention relates to a rope for operating (hereinafter referred to as a rope), more particularly to such a rope wherein the corrosion resistance is improved without lowering the durability for bending and a rope wherein the corrosion resistance is remarkably improved, each of which is preferably used for many technical fields such as a window regulator for an automobile. A rope is generally produced by stranding a plurality of wires or by stranding a plularity of ropes (in this case the rope is called a strand). Such rope is sometimes corroded by, for example, water containing salt. In order to prevent the rope from being corroded, the ropes mentioned hereinafter are proposed. (a) Steel wire plated with zinc is drawn to obtain a wire for a rope. A plurality of the wires are stranded each other and plated with tin to obtain a wire rope (JP-U2-25500/1979). (b) Steel wire plated with nickel or nickel alloy is plated with zinc or zinc alloy and is plated with tin or tin alloy on the zinc or the zinc alloy layer. Thus obtained steel wire is drawn and a plurality of the steel wires are twisted each other to obtain a rope (JP-U2-10332/1990 and GB-A-1 017 077). (c) Steel wire plated with zinc-aluminum alloy is drawn and stranded each other to obtain an inner core for a control cable (JP-U1-212616/1990). The above-mentioned ropes and the inner cable for a control cable have an anticorosion property which has been indeed improved as compared with a normal rope plated with zinc. However, with respect to the wire rope described in (a), the wire must be plated before a step for drawing a wire rod and after the step for stranding the wire, and a step for stranding the wire should be required. For that reason, the number of producing steps becomes rather high so that the cost for producing the wire rope is high. With respect to the rope described in (b), three kinds of plating steps are required for producing the rope. Accordingly, producing steps increase remarkably. With respect to the inner cable for the control cable described in (c), each of the wires is plated with zinc-aluminum alloy. Accordingly, cost for producing the inner cable is high. On the other hand, for the purpose of improving the durability on bending fatigue of the rope, generally the diameter of the wire is made to be small in order to decrease the bending stress. Therefore, the tension strength is lowered due to the reduced diameter of the wire. In order to decrease the tension stress, the number of the wires is increased. As rope wherein means for improving the durability on bending fatigue is employed a rope wherein a plurality of side strands are arranged around a core strand having a diameter larger than that of the side strands in such a state that the side strands are closed together is known (JP-U1-64796/1987). Further, the conventional rope has been closed in such a manner that the tightening percentage is approximately in the range of 0 to 2 % in order to prevent the wire from damaging when the strand is twisted. Researching the tightening percentage of the available ropes for operating, the result was found that the tightening percentage of the ropes was in the range of 0 to 2 %. That is to say, each tightening percentage was rather small. Besides, the tightening percentage used in the specification, for instance, with respect to a rope having 19+8x7 construction shown in Fig.7 is obtained as follows: tightening percentage = calculated diameter of the rope - measured diameter of the rope calculated diameter of the rope x 100, wherein the calculated diameter is the sum of the outer diameters of each wire and the measured diameter is a value which is obtained by measuring the diameter of a circumscribed circle of the rope. Furthermore, it has been said that durability on fatigue property is improved when a preforming is performed to the side strands so that the preforming percentage which is obtained by dividing the measured diameter into a wave diamter when the rope is loosed can be approximately in a range of 95 to 100 % (page 185 of "a hand book of a wire rope" (October 15, 1967) edited by the committee for editing a handbook of a wire rope, published by Hakua Shobo). As mentioned above, a rope having a stranded construction of, such as, the conventional rope, wherein a plurality of strands are stranded, is generally closed so that the tightening percentage is in a range of 0 to 2 % and the preforming percentage is in a range of 95 to 100 %. Besides, the tightening percentage can be obtained by the following formula (1) with respect to a rope having 19+8x7 construction as shown in Fig. 7; tightening percentage = {(a+2b 1 +2b 2 )+2(c+2d)}-D (a+2b 1 +2b 2 )+2(c+2d) x 100 wherein is a: outer diameter of the core wire 43 of the core strand, b 1 : outer diameter of the first side wire 44 of the core strand, b 2 outer diameter of the second side wire 45 of the core strand, c: outer diameter of the core wire 47 of side strand, d: outer diameter of the side wire 48 of side strand, D: measured outer diameter of rope 41. Further, with respect to a rope having W(19)+8x7 construction, wherein the core strand is stranded so as to have a Warrington type parallel lay strand as shown in Fig. 8, the tightening percentage is obtained by following formula (2) tightening percentage = {(a+2b 1 +2b 2 )+2(c+2d)}-D (a+2b 1 +2b 2 )+2(c+2d) x 100 wherein is a: outer diameter of the core wire 53 of the core strand, b 1 : outer diameter of the first side wire 54 of core strand, b 2 : outer diameter of the second side wire 56 of core strand, c: outer diameter of the core wire 58 of the side strand, d: outer diameter of the side wire 59 of the side strands, and D: measured outer diameter of the rope 51. On the other hand, the tightening percentage of a rope having 7 x 7 construction as shown in Fig. 9 can be obtained by the following formula (3) tightening percentage = a+2b+2c+4d-D a+2b+2c+4d x 100 wherein is a: outer diameter of the core wire 73 of the core strand, b: outer diameter of the side wired 64 of the core strand, c: outer diameter of the core wire 66 of the side strand, d: outer diameter of the side wire 67 of the side strand, and D: measured outer diameter of the rope 61. Next, the preforming percentage  is obtained by the following formula (4).  = T D x 100 (%) wherein is D: measured outer diameter of a rope as shown in Fig. 16 (A), and T: wave diameter when the rope is loosed as shown in Fig. 16 (B). However, the conventional rope wherein the tightening percentage is small and the preforming percentage is large, that is the rope wherein each strand is not stranded so tightly and the rope which is not closed so tightly is subject to deformation in the radial direction of the rope when the rope is used in such a portion that the rope is bended while the rope is slided, for instance in a guide which cannot rotate. Accordingly, there is such a problem that the durability on bending fatigue is low, since the wire is subjected to secondary bending, i.e. the wire is subjected to local bending due to an external pressure whereby the wire is pressed against the layer of the wires located innerly. The object of the present invention is to provide a rope for operating having at lower production cost the same corrosion resistance as conventional wire ropes, wherein the endurance property against bending fatigue is superior. This object is solved in accordance of the present invention by wire ropes for operating comprising the features of each one of claims 1, 2 or 3. Preferable improvements of this invention are subject matter of claims 4 and/or 5. The present invention provides a rope wherein the endurance property against bending fatigue is superior when the wires are subjected to bending in sliding movement and is remarkably improved, by virtue of specifying the tightening percentage and the preforming percentage. An aspect of the present invention is a rope for operating, comprising a plurality of wires made of steel wire being twisted together, wherein at least the wires which are arranged in such a manner as to be disposed on the outer surface of the rope being made of steel wire wherein the corrosion resistance is superior, and the wires which are located in the center of the rope are not made of wire wherein the corrosion resistance is superior. For instance, when the rope for operating is a spiral rope composed of a single layer or a plurality of layers and each layer is composed of a plurality of wires and the wires are twisted each other, the outermost layer is composed of steel wires wherein the corrosion resistance is superior, or when the rope for operating is a stranded wire wherein a plurality of strands composed of a plurality of wires and the wires are stranded and the strands are closed each other, side strands are composed of the steel wire wherein the corrosion resistance is superior. Besides, as steel wires wherein the corrosion resistance is superior wires are arranged in the outermost layer of the rope which are plated with zinc-aluminum alloy, and other wires may be plated with zinc. The rope for operating having stranded construction may have 7x7 construction wherein the tightening percentage is in the range of 2.5 to 8 %, or may have 19+8x7 construction or (parallel lay strand)+8x7 construction wherein the tightening percentage is in the range of 4 to 11 % and the preforming percentage is in the range of 65 to 90 % as mentioned hereinafter. In the rope of the present invention steel wires wherein the corrosion resistance is superior are arranged in the outermost layer of the rope. As the above-mentioned wire, the wire which is disposed on the surface thereof may be plated with zinc-aluminum alloy. With respect to the layer of zinc-aluminum alloy, the corrosion resistance is far better than that of the conventional layer composed of steel wire plated with zinc. For that reason, the wire of the present invention can be sufficiently used for a long interval. However, cost for plating the wire with the alloy having the corrosion resistance which is superior, such as zinc-aluminum alloy, is high compared with the conventional zinc plating. Accordingly, if all wires composing a rope are plated with the alloy having the corrosion resistance which is superior, the rope is very expensive. If in all the wires of the rope, such a steel wire wherein the corrosion resistance is suprior while the endurance property for bending is inferior is employed, the rope is not preferable to the use which is easily subjected to bending. When the outermost layer of the rope is composed of steel wires plated with the alloy having superior corrosion resistance, the same corrosion resistance property as that of a rope wherein all wires are plated with the alloy having superior corrosion resistance can be obtained. The cost for producing the rope of the present invention is far lower than that of conventional ropes. Further, the steel wires wherein the corrosion resistance is superior while the endurance property for bending is inferior are employed only in the outermost layer of the rope wherein the corrosion resistance is inferior while wires making the endurance property for bending superior are employed in the other layers of the rope. Thereby, a rope wherein the corrosion resistance and the endurance property for bending are superior can be produced. The above-mentioned aluminum is a component which contributes to the superior corrosion resistance in a metal plating layer. As occasion demands, a bit of silicon, magnesium, sodium, Mischmetal or the like may be added. When the weight percentage of the aluminum in the metal plating layer exceeds 10 % by weight, the corrosion resistance is lowered. On the contrary, in the case that the weight percentage is less than 1 %, the corrosion resistance is reduced. For that reason, the weight percentage of the aluminum is preferably in the range of 1 to 10 % by weight, and more preferably in the range of 4 to 5 % by weight. Composition of the metal plating layer is substantially the same as that of plating bath to be used. Accordingly, the composition of the metal plating layer can be adjusted by adjusting the composition of the plating bath. The deposit weight of the metal plating is preferably more than 15 g/m 2 in order to obtain a rope which maintains the corrosion resistance in the state wherein the rope is completed. When the rope is obtained by stranding the wires which are obtained by drawing the plated wire, the deposit weight on the surface of the wire rod should be more than 100 g/m 2 in order to maintain the above-mentioned deposit weight of 15 g/m 2 in the state when the rope is completed. Further, the deposit weight is preferably less than 400 g/m 2 in order that the plated thick wire (or wire rod) can be suitably drawn. In the present invention, the way wherein the wire of the rope is plated with zinc-aluminum alloy is not limited to a specific way. However, for instance, there is a way wherein the steel wire is dipped (or immersed) in the plating bath which is mixed with melted aluminum, and the steel wire is drawn. Besides, the above-mentioned plating bath is used when the steel wire is normally plated with zinc by means of hot dipping. In the above way, when the content of aluminum in the plating bath is 5 % by weight, eutectic point is obtained and homogeneous eutectic structure can be obtained. The wires plated with zinc-aluminum alloy are in the specific location stranded each other as mentioned hereinafter so that the rope can be produced. Thus produced rope has superior corrosion resistance. Accordingly, the rope can be used for a long interval. Besides, as an embodiment of the steel wire having superior corrosion resistance, the steel wire plated with zinc-aluminum alloy is explained as mentioned hereinbefore. However, the steel wire is not limited to the steel wire plated with zinc-aluminum alloy. For instance, steel wires plated with zinc-nickel alloy or stainless steel wires and the like can be employed. The rope of the present invention is more firmly closed than conventional ropes since the tightening percetage of the rope in accordance with the present invention is large. Accordingly, deformation in the radial direction can be prevented from generating so that secondary bending in the wire is not easy to be generated. Further, since the preforming percentage is small, the side strands of the rope which are closed is subjected to the force directed toward the center of the rope. Accordingly, deformation in the radial direction can be prevented from generating and secondary bending of the wire is not easy to be generated. Accordingly, in the rope of the present invention durability on bending in sliding movement is improved. In the drawings Fig. 1 is a cross-sectional view of a rope which is not part of the present invention; Fig. 2 is a cross-sectional view of another rope which is also not part of the present invention; Fig. 3 is a cross-sectional view of an embodiment of the rope of a first aspect in accordance with the present invention; Fig. 4 is a cross-sectional view of another embodiment of the rope of the first aspect in accordance with the present invention; Fig. 5 is a cross-sectional view of yet another embodiment of the rope of the first aspect in accordance with the present invention; Fig. 6 is a cross-sectional view of yet another embodiment of the rope of the first aspect in accordance with the present invention; Fig. 7 is an explanatory drawing illustrating the tightening percentage of the rope and a sectional view of an embodiment of the rope of a second aspect in accordance with the present invention; Fig. 8 is an explanatory drawing illustrating the tightening percentage of the rope and a sectional view of another embodiment of the rope of the second aspect in accordance with the present invention; Fig. 9 is an explanatory drawing illustrating the tightening percentage of the rope and a sectional view of yet another embodiment of the rope of the second aspect in accordance with the present invention; Fig. 10 is an explanatory drawing of an apparatus for measuring the durability on bending fatigue of the rope in which rollers are used; Fig. 11 is an explanatory drawing of a roller used in the apparatus of Fig. 10; Fig. 12 is a partial explanatory drawing of a roller used in the apparatus of Fig. 10; Fig. 13 is an explanatory drawing of an apparatus for measuring the durability on bending fatigue of the rope by using fixed guides when the rope is subjected to bending in a state of sliding motion; Fig. 14 is an explanatory drawing of one of the fixed guides which are used in the apparatus of Fig. 13; Fig. 15 is a partial explanatory drawing of one of the fixed guides which are used in the apparatus of Fig. 14; and Fig. 16 is an explanatory drawing illustrating the preforming percentage of the rope. In the present invention, the rope has for instance a shape in section as shown in Figs. 3 to 9. The present invention is not limited to the above shapes. In Fig. 1 to 6, wires shown in double circle are steel wires having superior corrosion resistance. The rope 1 in Fig. 1 is an example of a spiral rope having a single layer or several layers, and each of which is composed of a plurality of the wires. The rope 1 is obtained by twisting the wires each other. The spiral rope is formed by twisting six wires 3 defining a first layer arranged around a core wire 2, and twisting twelve wires 4 defining a second layer arranged around the first layer. Superior corrosion resistnace steel wires are used as wires 4 of the second layer. The rope 5 shown in Fig. 2 is the same as that of Fig. 1 except that superior corrosion resistant steel wires are used not only as wires 7 of the second layer but also as wires 6 of the first layer. The rope 8 shown in Fig. 3 has a so-called 7x7 construction. That is, a core strand 9 is defined by stranding six side wires 11 arranged around a core wire 10, a side strand 12 is defined by stranding six side wires 14 arranged around a core wire 13, and a stranded rope is obtained by closing the six side strands 12 arragned around the core strand 9. Besides, superior corrosion resistant steel wires are used as side wires 14 of the side strands 12. The rope 15 shown in Fig. 4 is the same as that of Fig. 3 except that superior corrosion resistant steel wires are used as core wire 17 of side strands 16 having an outer layer of wires 18. The rope 19 shown in Fig. 5 has a so-called 19+8x7 construction. That is, a core strand 20 is defined by stranding six first side wires 22 arrranged around a single core wire 21 and stranding twelve second side wires 23 arranged around the six side wires 22, and a side strand 24 is defined by stranding six side wires 26 arranged around a single core wire 25. The rope 19 having a stranded construction is obtained by closing eight pieces of the side strands 24 arranged around the core strand 20. Besides, superior corrosion resistance steel wire is used for the core wire 25 and the side wires 26 of the side strands 24. The rope 27 shown in Fig. 6 has the 19+8x7 construction. However, wires 29, 30, 31 and 32 are stranded in the core strand 28 such that the core strand 28 has a parallel lay construction. In other word, the core strand 28 is stranded in such a way that each wire of the core strand is linearly contacted with the other. The parallel lay strand is a type of stranding wires having different outside diameter in the strand. In accordance with the parallel lay strand, each layer of the rope 27 has the. same pitch for stranding and the same direction of stranding. When the wires are stranded in the above way, each wire 31 of the second layer (the outer layer) is engaged into a groove defined by the adjoining wires 30 of the first layer (inner layer), one wire being substantially in linear contact with another wire without crossing each other. As a result, the strand is firmly stranded and deformation in the radial direction does not happen easily. Internal abrasion in the strand due to a friction between the wires is low and fatigue due to a secondary bending of wires is not generated. Therefor, the rope shown in Fig. 6 has superior properties. The rope 27 shown in Fig. 6 has (parallel lay strand)+8x7 construction. As parallel lay strand, a core strand 28 having a Warrington type strand construction is used. In other words, the rope 27 has a W(19)+8x7 construction. With respect to the Warrington strand, difference between the maximum diameter and the minimum diameter in the wires of the core strand is the smallest in the strands having parallel lay strand construction composed of 19 wires. For that reason. the rope 27 is suitable for strands having small diameter. To be concrete, six pieces of first side wires 30 defining a first layer are arranged around a core wire 29, and the diameter of the first side wires 30 is somewhat smaller than that of the core wire 29. Each of six pieces of third side wires 31 having the same diameter as that of the core wire 29 is arranged in a groove defined by adjoining first side wires 30 and each of six pieces of second side wires 32 is arranged around the first layer in such a way as to be along with the first side wire 30. The diameter of the second side wires 32 is still smaller than that of the first side wires. Further, the above-mentioned side wires are stranded at the same time in such a way that each layer has the same pitch and in the same direction. Thus, the core strand 28 is formed. The diameter of each wire of the core strand 28 is not limited to the diameter mentioned hereinbefore. In short, the diameter of each wire 29, 30, 31 and 32 of the core strand 28 is suitably selected so that the wires can linearly contact each other when each wire is stranded in the same pitch and in the same direction. Further, eight pieces of side strands 33 are obtained by stranding six pieces of side wires 35 around a core wire 34. Superior corrosion resistant steel wire is used for the core wire 34 and the side wires 35 of the side strands 33. Next the rope of the present invention is explained more particularly on the basis of concrete examples. Besides, in the following Example 1 and comparative Examples 1 to 3, the above-mentioned rope having strand construction of 7x7 construction is used. Example 1 A wire rod having an outer diameter of 1.05 mm as a wire for a core strand was obtained by immersing a steel wire (material: JIS G 3506, SWRH 62A) into a plating bath composed of zinc being in the condition wherein the temperature is in the range of 430 to 480°C. The deposit weight in the specific area was 150 g/m 2 . Further, as wire for the side strand a wire rod was obtained by the same way as that of the above-mentioned wire for the core strand except that a plating bath composed of 4 % by weight of aluminum and 96 % by weight of zinc was used. Next, the wire rods were drawn so that the core wire 10 for the core strand having an outer diameter of 0.185 mm, the side wires 11 for the core strand having an outer diameter of 0.185 mm, the core wire 17 for the side strand having an outer diameter of 0.185 mm, and the side wires 18 for the side strand having an outer diameter of 0.175 mm were produced. Besides, the deposit weight was 30 g/m 2 after the wire rods were drawn. Then, the strands were closed in such a manner as shown in Fig. 4 wherein the rope has a 7x7 construction, and the rope of Example 1 having an outer diameter of 1.5 mm was produced. Comparative Example 1 Wire rods were produced in the same way as in Example 1 except that the zinc-aluminum plating bath used in Example 1 was used for the wires for the core strand and the side strands. Further, the wire rods were drawn and stranded each other so that the rope had the 7x7 construction as Comparative Example 1. Comparative Example 2 Wire rods were produced by the same way as in Example 1 except that a conventional zinc plating bath was used for the wires for the core strand and the side strands. Further, the wire rods were drawn and stranded each other so that the rope had the 7x7 construction as Comparative Example 2. Besides, the plating weight was 30 g/m 2 after the wire rods were drawn. Comparative Example 3 A wire rope as disclosed in JP-U2-25500/1979 wherein the outer diameter of the wires is 1.5 mm and the wire rope had the 7x7 construction was bought as Comparative Example 3. The wires of the wire rope had a zinc plating layer and a tin layer. The weight of the plating composed of the zinc plating layer and the tin plating layer was 30 g/m 2 (total weight of both layers). In the produced ropes of Example 1 and Comparative Examples 1 to 3, the time to generate rust was confirmed by "salt spray test" (JIS Z 2371). The results are shown in Table 1. As shown in Table 1, the rope of Example 1 wherein each wire of the core strand is plated with zinc and each wire of the side strands is plated with zinc-aluminum alloy has improved the corrosion resistance remarkably as compared with the rope of Comparative Example 2 wherein all the wires are plated with zinc or the rope of Comparative Example 3 having a zinc plating layer and a tin plating layer. On the other hand, comparing with the rope of Comparative Example 1, the result was that the rope of Example 1 has the same corrosion resistance as that of Comparative Example 1. As mentioned hereinbefore, superior corrosion resistant steel wire is used for only the wires defining the outermost layer. Then, cost for producing the rope is low as compared with the rope wherein the superior corrosion resistant steel wire is used for all the wires. Further, the rope can have the same corrosion resistance as that of the rope wherein the superior corrosion resistant steel wires is used for all the wires. With respect to such a rope having a stranded construction, when the rope has for instance the 7x7 construction, the rope is firmly closed as compared with the conventional rope having 7x7 construction (tightening percentage is in the range of 0 to 2 %) if the rope having 7x7 construction is closed with tightening percentage being in the range of 2.5 to 8 %. A portion of the rope wherein the rope is bended with sliding motion, such as a fixed guide, is not subjected to secondary bending, and endurance property is not reduced. Especially, with respect to the rope having the 19+8x7 construction or (parallel lay strand)+8x7 construction, the rope has advantages as mentioned hereinbefore as compared with a conventional rope having the 19+8x7 construction (the tightening percentage is in the range of 0 to 2 % and the preforming percentage is in the range of 95 to 100 %) when the tightening percentage of the rope having the 19+8x7 construction or (parallel lay strand)+8x7 construction is in the range of 4 to 11 % and the preforming percentage is in the range 65 to 90 % as mentioned hereinafter. Next, a second aspect of the rope of the present invention wherein the rope has the stranded construction and the rope is closed with a specific tightening percentage and a specific preforming percentage is explained with reference to Figs. 7 to 9. However, present invention is not limited to the ropes having such shapes shown in Figs. 7 to 9. Further, the rope is not limited to either the rope using a superior corrosion resistant steel wire or the rope without using a superior corrosion resistant rope. The rope 41 shown in Fig. 7 has a so-called 19+8x7 construction which is the same as that of the rope shown in Fig. 5. That is, a core strand 42 is defined by stranding six first side wires 44 defining a first layer arrranged around a single core wire 4 3 and stranding twelve second side wires 45 defining a second layer arranged around the first layer, and a side strand 46 is defined by stranding six side wires 48 arranged around a single core wire 47. The rope 41 having a stranded construction is obtained by closing eight pieces of the side strands 46 arranged around the core strand 42. Further, the tightening percentage of the rope 41 is in the range of 4 to 11 % and the preforming percentage of the rope 41 is in the range of 65 to 90 %. The reason why the tightening percentage is in the range of 4 to 11 % is that there is such a problem that it is difficult to close the rope when the tightening percentage is more than 11 %, a breakage tends to happen or the surface of the wire is sometimes damaged due to excessive closing when the rope is produced, while if the tightening percentage is less than 4 %, the endurance property is insufficient when the rope is subjected to bending with sliding motion as becomes clear from the example mentioned hereinafter. On the other hand, the reason why the preforming percentage is in the range of 65 to 90 % is that if the preforming percentage is more than 90 %, the closing force in the direction of the center of the rope is not sufficiently applied to the side strand when the rope is used for the portion wherein the rope is bended with sliding along such as a fixed guide so that secondary bending of the wires tends to happen in the rope. Accordingly, the endurance property is lowered as clearly explained in the examples and the comparative examples mentioned hereinafter. On the contrary, with respect to a rope wherein the preforming percentage is not more than 65 %, the side strand becomes loose when the rope is cut. For that reason, the rope cannot be used. Next, a rope 51 shown in Fig. 8 is another example of the rope of the present invention which has the same Warrington type strand as the rope 27 (referring to Fig. 6) of the above-mentioned example. That is, six pieces of first side wires 54 defining a first layer are arranged around a core wire 53, and the diameter of the first side wires 54 is somewhat smaller than that of the core wire 53. Each of six pieces of third side wires 55 having the same diameter as the core wire 53 is arranged in grooves defined by adjoining first side wires 54 and each of six pieces of second side wires 56 is arranged around the first layer in such a way as to be along with the first side wires 54. The diameter of the second side wires 56 is smaller than that of the first side wires 54. Further, the above-mentioned side wires 54, 55, 56 are stranded at the same time in such a way as to be in the same pitch and in the same direction around the core wire 53. Thus, the core strand 52 is formed. Besides, the diameter of each wire is not limitted to the diameter mentioned hereinbefore. In short, the diameter of each wire is suitably selected so that each wire can be linearly contacted each other when each wire is stranded in the same pitch and in the same direction. Further, eight pieces of side strands 57 are obtained by stranding six pieces of side wires 59 around a core wire 58. In the rope 51, the tightening percentage is in the range of 4 to 11 % and the preforming percentage is in the range of 65 to 90 %. Further, yet another example of the rope of the present invention is shown in Fig. 9. In a rope 61, the tightening percentage is in the range of 4 to 11 % and the preforming percentage is in the range of 65 to 90 %. The rope 61 has the same 7x7 construction as the ropes 8 and 15 shown in Figs. 3 and 4, respectively. That is, a core strand 62 is defined by stranding six side wires 64 arranged around a core wire 63, a side strand 65 is defined by stranding six side wires 67 arranged around a core wire 66, and a stranded rope is obtained by closing the six side strands 65 arragned around the core strand 62. Next, the rope of the present invention is explained more particularly on the basis of concrete examples. Example 2 (referring to Fig. 7) A wire rod having an outer diameter of 0.93 mm was obtained by plating steel wire (material: JIS G 3506 SWRH 2A) with zinc. Next, the wire rod was drawn so that the core wire 43 of the core strand having an outer diameter of 0.170 mm, the first side wire 44 of the core strand having an outer diameter of 0.150 mm, the second side wire 45 of the core strand having an outer diameter of 0.150 mm, the core wire 47 of the side strand having an outer diameter of 0.150 mm, and the side wire 48 of the side strand having an outer diameter of 0.140 mm were produced. The wires were stranded in the direction shown in Table 2 so that a rope having the 19+8x7 construction was obtained. The measured outer diameter D of the wire was 1.550 mm as shown in Example 2. The calculated outer diameter of the rope was 1.630 mm. Accordingly, the tightening percentage of the rope was 4. 91 %, and the wave diameter of the side strand was measured after loosing the rope so that the diameter was 1. 25 mm, then the preforming percentage was 80.6 %. A rope having the above-mentioned tightening percentage and preforming percentage cannot be obtained without adjusting pressure, tension, and a degree of preforming which are applied to the rope in the producing step. Example 3 The rope of Example 3 was obtained by the same way as that of Example 2 except for the measured outer diameter and the tightening percentage of the rope, and the wave diameter and the preforming percentage of the strand as shown in Table 2. Example 4 The rope of Example 4 was obtained by the same way as that of Example 2 except for the measured outer diameter and the tightening percentage of the rope, and the wave diameter and the preforming percentage of the strand as shown in Table 2. Example 5 The rope of Example 4 was obtained by the same way as that of Example 2 except for the measured outer diameter and the tightening percentage of the rope, and the wave diameter and the preforming percentage of the strand as shown in Table 2. Example 6 The rope of Example 6 was obtained by the same way as that of Example 2 except that as wire rod of the wires of the side strand, a wire having an outer diameter of 0.93 mm was used wherein steel wire (material: JIS G 3506 SWRH 62A) was plated with zinc-aluminum alloy. The zinc-aluminum plating was performed by hot dipping into a zinc plating bath containing 4 % by weight of aluminum. Example 7 (referring to Fig. 8) A wire rod having an outer diameter of 0.93 mm was obtained by plating steel wire (material: JIS G 3506 SWRH 62A) with zinc. Next, the wire rod was drawn so that the core wire 53 of the core strand having an outer diameter of 0.170 mm, the first side wire 54 of the core strand having an outer diameter of 0.160 mm, the third side wire 55 of the core strand having an outer diameter of 0.170 mm, and the second side wire 56 of the core strand having an outer diameter of 0.130 mm, each of which is the wire defining the core strand 52, were produced. The wire rod having an outer diameter of 0.93 mm was obtained by plating steel wire (material: JIS G 3506 SWRH 62A) with zinc-aluminum alloy. Further, the wire rod was drawn so that the core wire 58 of the side strand having an outer diameter of 0.150 mm and the side wire 59 of the side strand having an outer diameter of 0.140 mm, each of which is the wire defining the side strand 57, were produced. The above-mentioned wires were stranded in the direction as shown in Table 2, and the core strand 52 was formed to be a Warrington type strand, then the core strand 52 and the side strands 57 were closed so that the rope 51 of Example 7 having W(19)+8x7 construction and having the measured diameter D of 1,500 mm was obtained. Comparative Example 4 The rope of Comparative Example 4 was obtained by the same way as that of Example 2 except for the measured outer diameter and the tightening percentage of the rope, and the wave diameter and the preforming percentage of the side strand as shown in Table 2. Comparative Example 5 The rope of Comparative Example 5 was obtained by the same way as that of Example 2 except for the wave diameter and the preforming percentage of the side strand as shown in Table 2. Comparative Example 6 The rope of Comparative Example 6 was obtained by the same way as that of Example 2 except for the wave diameter and the preforming percentage of the side strand as shown in Table 2. The tightening percentage (%) of each rope of Examples 2 to 6 and Comparative Examples 4 to 6 were obtained by the formula (1), and the percentage (%) of the rope of Example 7 was obtained by the formula (2). Further, the preforming percentage (%) of Examples 2 to 7 and Comparative Examples 4 to 6 were obtained by the formula (3). Next, a bending fatigue test by using rollers and a bending fatigue test by using fixed guides were performed to Examples 2 to 7 and Comparative Examples 4 to 6 which were obtained as mentioned hereinbefore. The way of the bending fatigue tests are as follows: As shown in Fig. 10, in the test method using a pair of rollers a rope 41 with an overall length of 1000 mm was provided with a weight 71 of 10 kg at one end. The rope 41 was arranged so as to be turned by 90 degree by a roller 72b and then turned by 180 degree by another roller 72a. The other end of the rope 41 was connected with a piston rod of an air cylinder 73. When the air cylinder 73 reciprocates in the direction of arrow E and arrow F, the roller 72a rotates in the direction of arrow G and arrow H and the roller 72b rotates in the direction of arrow J and arrow K. When the air cylinder 73 first moves in the direction of arrow E, the weight 71 is lifted upwards and abuts against a stopper 74. Thereby, the air cylinder generates a stall force of 35 kgf for 0.5 sec. Thereafter the air cylinder moves in the direction of arrow F. The stroke of the rope was 100 mm and the period was 20 strokes/min. Further, a sufficient amount of an olefinic grease is applied to the roller 72a, 72b in the portions wherein the rope 41 is contacted with. Fig. 11(A) is an elevation and Fig. 11(B) is a cross-section of the rollers 72a and 72b, respectively. The grooved-track diameter L of the rollers 72a, 72b is 30 mm, and the material of the rollers is nylon 6. Fig. 12 is a partially enlarged sectional representation of the rollers 72a and 72b, respectively. The inner radius R1 of the grooved track is 1.0 mm, and the angle  formed with the internal side surfaces of the groove each other is 30 degree. The rope 41 for the test was reciprocated for 20,000 cycles. As shown in Fig. 13, in the test method using a fixed guide the rope 41 with an overall length of 1000 mm was provided with a weight 75 of 10 kg at one end. The rope 41 was arranged so as to be turned by 90 degree by a fixed guide 76b and then turned by 180 degree by another fixed guide 76a. The other end of the rope 41 was connected with a piston rod of an air cylinder 77. When the air cylinder 77 reciprocates in the direction of arrow M and arrow N, the rope 41 slides on the fixed guides in the direction of arrow P and arrow Q. The air cylinder 77 first moves in the direction of arrow M so that the weight 75 is lifted upwards and hits a stopper 78. Thereby, the air cylinder generates a stall force of 35 kgf for 0.5 sec. Thereafter the air cylinder 77 moves in the direction of arrow N. The stroking length of the rope was 100 mm and the reversal speed was 20 cycles per minute. Further, a sufficient amount of an olefinic grease was applied to the fixed guides 76a, 76b in the portions wherein the rope 41 is contacted with. Fig. 14(A) is an elevation and Fig. 14(B) is a cross-section of the fixed guides 76a and 76b, respectively. The core diameter S of the fixed guides 76a, 76b is 30 mm, and the material thereof is nylon 6. Fig. 15 is a partially enlarged sectional representation of the guides 76a and 76b, respectively. The inner radius R2 of the grooved track is 1.0 mm, and the angle γ is 30 degree. The rope 41 for the test was reciprocated for 20000 cycles. Further, the test to confirm the breakage of the wire, was continued until the rope 41 was broken. Then, the number of the cycles at the break was recorded. The results of the bending fatigue test in Examples 2 to 7 and Comparative Examples 4 to 6 are shown in Table 3. bending fatigue test by a pair of rollers bending fatigue test by a pair of fixed guides number of cycles number of broken wires number of cycles number of broken wires number of cycles when the rope was broken Ex. 2 20000 0 20000 0 72000 Ex. 3 20000 0 20000 0 69000 Ex. 4 20000 0 20000 0 132000 Ex. 5 20000 0 20000 0 127000 Ex. 6 20000 0 20000 0 70000 Ex. 7 20000 0 20000 0 186000 Com.Ex.4 20000 0 20000 63 25000 Com.Ex.5 20000 0 20000 18 31000 Com.Ex.6 20000 0 20000 17 31000 According to the test results shown in Table 3, any breakage was not found in Examples 2 to 7 and in Comparative Examples 4 to 6 on the bending fatigue test by a pair rollers at 20000 cycles. However, on the tests by fixed guides, 63 pieces of the wires were broken at 20000 cycles in Comparative Example 4. In Comparative Example 5, 18 pieces of the wires were broken and in Comparative Example 6, 17 pieces of the wire were broken at 20000 cycles. On the contrary, no breakage of a wire was found in Examples 2 to 7 after the bending fatigue test was repeated 20000 cycles. Further, the bending fatigue test was repeated until the rope was broken so that the rope was broken at 25000 cycles in Comparative Example 4 and the rope was broken at 31000 cycles in Comparative Examples 5 and 6. On the contrary, it was found that the durability of Examples 2, 3, and 6 was more than two times as much as that of Comparative Examples 4 to 6, the durability of Examples 4 and 5 was more than four times as much as that of Comparative Examples 4 to 6, and the durability of Example 7 was more than six times as much as that of Comparative Examples 4 to 6. In the bending fatigue test using a pair of rollers, in other words, under the condition of that the wire is subjected to only bending, there is not so great difference in Examples 2 to 7 and Comparative Examples 4 to 6. However, there is a remarkable difference in the durability when the rope is bended while the rope is slided on the guide. Accordingly, the rope wherein the rope is closed such that the tightening percentage is in the range of 4 to 11 %, and the preforming precentage is in the range of 65 to 90 % is superior in the durability. On the other hand, comparing Example 2 with Example 6, even if the wire of the side strand is plated with zinc-aluminum alloy instead of zinc, the durability was improved, i.e. there is no difference in the durability between the wires of the side strand applied to the normal zinc plating and superior corrosion resistant plating. Examples 2 to 7 having 19+8x7 construction or W(19)+8x7 construction have the same characteristic. However, a rope having, for instance, 7x7 construction using large-diameter-wire, or 7x19 construction has the same effect. The rope of the present invention, wherein steel wire having superior corrosion resistance is used for the outermost wires, can be endurable to corrosion for a long time even under the circumstance wherein salt water is added to the wire, for instance. Furthermore, the superior corrosion resistant steel wire should be used only for the outermost wire. For that reason, the cost for producing the wire is lower than that of the wire wherein the superior corrosion resistant steel wire is used for all the wires. Further, even in the case that the superior corrosion resistant steel wires having an usual durability on bending are arranged in the outer layer of the rope, the rope having superior durabiliyy for bending and superior corrosion resistance can be obtained when the steel wires having superior durability for bending are arranged in the inner layer of the rope. In the rope of the present invention, wherein the tightenining percentage is in the range of 4 to 11 % and the preforming percentage is in the range of 65 to 90 %, the fatigue durability on bending is not lowered even if the rope is used in the portion, such as a guide, wherein the rope is bended with sliding thereon. Therefore, for instance, the rope is preferably used for a control cable for a window regulator of automobiles.

Claims: Rope for operating, comprising a plurality of strands made of steel wire being twisted together, at least that wires which are disposed on the outer surface of the rope are steel wires having an improved corrosion resistance which is superior to that of the steel of the wires in the center of the rope, characterized in that the rope has 7 x 7 construction having a tightening percentage in the range of 2.5 to 8 %. Rope for operating, comprising a plurality of strands made of steel wire being twisted together, at least that wires which are disposed on the outer surface of the rope are steel wires having an improved corrosion resistance, which is superior to that of the steel of the wires in the center of the rope, characterized in that the rope has 19 + 8 x 7 construction having a tightening percentage in the range of 4 to 11 % and a preforming percentage in the range of 65 to 90 %. Rope for operating, comprising a plurality of strands made of steel wire being twisted together, at least that wires which are disposed on the outer surface of the rope are steel wires having an improved corrosion resistance which is superior to that of the steel of the wires in the center of the rope, characterized in that the rope has (parallel lay strand) + 8 x 7 construction having a tightening percentage in the range of 4 to 11 % and a preforming percentage in the range of 65 to 90 %. Rope as in one of claims 1 to 3, wherein each of the wires which are defining side strands (16; 24; 33) of the rope is composed of the steel having a superior corrosion resistance. Rope as in one of claims 1 to 4, wherein the wires disposed on the outer surface of the rope are plated with zinc-aluminium alloy and the wires which are not disposed on the outer surface of the rope are plated with zinc. Rope as in claim 5, wherein the weight percentage of aluminium in the zinc-aluminium alloy plating layer is 1 to 10 wt.%. Rope as in claim 6, wherein the weight percentage of aluminium in the zinc-aluminium alloy plating layer is 4 to 5 wt.%.

Inventors: FURUKAWA HIROAKI, NARITA YUKIO, ONIMARU SADAHIRO, FURUKAWA, HIROAKI, NARITA, YUKIO, ONIMARU, SADAHIRO
Applicants: NIPPON CABLE SYSTEM INC, NIPPON CABLE SYSTEM INC.
Application year: 1992
Main classification: D07B1
IPC codes: D07B1