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 plurality of the steel wires are twisted each other to obtain a rope (JP-U2-10332/1990). (c) Steel wire plated with zinc-aluminum alloy is drawn and stranded each other to obtain an inner core for a control cable JP-A-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 many 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 each wire. In order to decrease the tension stress, the number of 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 as disclosed in JP-U1-64796/1987 and as forming the preamble of claim 1. Conventional ropes have been closed in such a manner that the tightening percentage is approximately in the range of 0 to 2 % in order to prevent the wires from damaging when the strand is twisted. Researching the tightening percentage of available ropes for operating, the result was found that each 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 diameter of each wire and the measured diameter is the value which is obtained by measuring the diameter of the 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 strand so that the preforming percentage which is obtained by dividing the measured diameter into a wave diamter when the rope is loosened can be approximately in a range of 95 to 100 % (page 185 of "Hand Book of Wire Ropes" (October 15, 1967) edited by the committee for editing a handbook of wire ropes, published by Hakua Shobo). A mentioned the above, the 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 formular(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 the 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 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 following formula (4).  = T D x 100 (%), wherein is D: the measured outer diameter of a rope as shown in Fig. 16 (A), and T: the wave diameter when the rope is loosened as shown is Fig. 16 (B). However, conventional ropes wherein the tightening percentage is small and the preforming percentage is large, that is ropes 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 invention is to provide an operating rope having remarkably improved endurance properties against bending fatigue when the rope is subjected to bending in sliding movement. Subject matter of the present invention is a rope for operating composed of a plurality of strands, each of which are composed of a plurality of stranded wires; said rope is characterized in that 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 for operating has a stranded construction, for instance a 19+8x7 construction or a (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, hereinbefore. The rope of the present invention is more firmly closed than conventional ropes since the tightening percentage of the rope in accordance with the present invention is large. Accordingly, deformation in 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, the deformation in radial direction can be prevented from generating and the secondary bending of the wire is not easy to be generated. Accordingly, with the rope of the present invention, durability on bending in sliding movement is improved. Fig. 1 is an explanatory drawing illustrating the tightening percentage of the rope and a sectional view of an embodiment of the rope in accordance with the present invention; Fig. 2 is an explanatory drawing illustrating the tightening percentage of the rope and a sectional view of another embodiment of the rope in accordance with the present invention; Fig. 3 is an explanatory drawing illustrating the tightening percentage of the rope and a sectional view of yet another embodiment of the rope in accordance with the present invention; Fig. 4 is an explanatory drawing of an apparatus for measuring the durability on bending fatigue of the rope in which rollers are used; Fig. 5 is an explanatory drawing of the roller used in the apparatus of Fig. 4; Fig. 6 is an explanatory drawing of the roller used in the apparatus of Fig. 4; Fig. 7 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. 8 is an explanatory drawing of the fixed guides which are used in the apparatus of Fig. 7, Fig. 9 is an explanatory drawing of the fixed guides which are used in the apparatus of Fig. 14; and Fig. 10 is an explanatory drawing illustrating the preforming percentage of the rope. The present invention relates to ropes having for instance a shape in section as shown in Figs. 1 to 3. Especially, with respect to ropes having the 19+8x7 construction or the (parallel lay strand)+8x7 construction, the rope has advantages as mentioned hereinbefore as compared with conventional ropes having the 19+8x7 construction (the tightening percentage of which 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 the (parallel lay strand)+8x7 construction is in the range of 4 to 11 % and the percentage is in the range 65 to 90 % as mentioned hereinafter. The rope of the present invention has the stranded construction and is closed with a specific tightening percentage and a specific preforming percentage, as explained with reference to Figs. 1 to 3. The rope 41 shown in Fig. 1 has a so-called 19+8x7 construction, 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 43 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 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 more than 90 %, a 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 a wire tends to happen in the wire. Accordingly, the endurance property is lowered as clearly explained in the example and the comparative example 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. 2 is another example of the rope of the present invention which has the Warrington type strand. 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 that of the core wire 53 is arranged in the groove defined by the 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 wire 56 is still smaller than that: of the first side wire 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. Besides, 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. 3. 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 a 7x7 construction. 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 the concrete examples. Example 1 (referring to Fig. 1) A wire rod having an outer diameter of 0.93 mm was obtained by plating the 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 1, then a rope having 19+8x7 construction was obtained. Besides, the measured outer diameter D of the wire was 1.550 mm as shown in example 1. 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 %. Besides, the 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 2 The rope of example 2 was obtained by the same way as that of example 1 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 1. Example 3 The rope of example 3 was obtained by the same way as that of example 1 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 1. Example 4 The rope of example 4 was obtained by the same way as that of example 1 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 1. Example 5 The rope of example 5 was obtained by the same way as that of example 1 except that as the wire rod of the wire of the side strand, the wire having an outer diameter of 0.93 mm wherein the steel wire (material: JIS G 3506 SWRH 62A) was plated with zinc-aluminum alloy. Besides, the zinc-aluminum plating was performed by hot dipping into the zinc plating bath containing 4 % by weight of aluminum. Example 6 (referring to Fig. 2) 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, 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 1, 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 the example 6 having W(19)+8x7 construction and having the measured diameter D of 1,500 mm was obtained. Comparative Example 1 The rope of comparative example 1 was obtained by the same way as that of example 1 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 1. Comparative Example 2 The rope of comparative example 2 was obtained by the same way as that of example 1 except for the wave diameter and the preforming percentage of the side strand as shown in Table 1. Comparative Example 3 The rope of comparative example 3 was obtained by the same way as that of example 5 except for the wave diameter and the preforming percentage of the side strand as shown in Table 1. Besides, the tightening percentage (%) of each rope of the examples 1 to 5 and the comparative examples 1 to 3 were obtained by the formula (1), and the percentage (%) of the rope of the example 6 was obtained by the formula (2). Further, the preforming percentage (%) of the examples 1 to 6 and the comparative examples 1 to 3 were obtained by the formula (3). Next, the bending fatigue test by using rollers and the bending fatigue test by using a fixed guide were performed to the examples 1 to 6 and comparative examples 1 to 3 which were obtained as mentioned hereinbefore. The way of the bending fatigue tests are as follows: (the test method using a pair of rollers) As shown in Fig. 4, the rope (hereinafter numeral 41 is represented for the rope) in which overall length was 1000 mm was provided with a weight 71 of 10 kg at one end. Then, the rope 41 was arranged so as to be turned by 90 degree by a roller 72b, then turned by 180 degree by another roller 72a. Further, 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. Besides, the air cylinder 73 moves in the direction of arrow E firstly, then the weight 71 is lifted upwardly and abuts against a stopper 74 thereby, the air cylinder generates a stall force of 3 5 kgf for 0.5 sec. Thereafter the air cylinder moves in the direction F. Besides, the stroke of the rope was 100 mm and period was 20 strokes/min. Further, a sufficient amount of an olefinic grease is applied to the roller 72a, 72b in the portion wherein the rope 41 is contacted with. Fig. 5 represents an elevation (Fig. 5 (A)) and a side elevation (Fig. 5 (B)) of the roller 72a, 72b. A grooved-track diameter L of the roller 72a, 72b is 30 mm and material thereof is nylon 6. Fig. 6 is a partially enlarged sectional representation. The inner radius R1 of the grooved track is 1.0 mm, and the angle  formed with internal side surface of the groove each other is 30 degree. The rope 41 for the test was reciprocated for 20, 000 cycles. (test method using a fixed guide) As shown in Fig. 7 the rope 41 in which overall length was 1000 mm was provided with a weight 75 of 10 kg at one end. Then, the rope 41 was arranged so as to be turned by 90 degree by a fixed guide 76b, then turned by 180 degree by another fixed guide 76a. Further, 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 is slided on the fixed guide in the direction of arrow P and arrow Q. Besides, the air cylinder 77 moves in the direction of arrow M firstly, then the weight 75 is lifted upwardly 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 N. Besides, the stroking length of the rope was 100 mm and the reversal speed was 20 cycles per minute. Further, a sufficient amount of a olefinic grease was applied to in the fixed guide 76a, 76b, the portion wherein the rope 41 is contacted with. Fig. 8 represents an elevation (Fig. 8 (A)) and a side elevation (Fig. 8 (B)) of the fixed guide 76a, 76b. The core diameter S of the fixed guide 76a, 76b is 30 mm and the material thereof is nylon 6. Fig. 9 is a partially enlarged sectional representation. inner radius R2 of the grooved track is 1.0 mm, and the gash 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 broke, then the number of the cycles at the break was recorded. The results of the bending fatigue test in example 1 to 6 and comparative examples 1 to 3 are shown in Table 2. bending fatigue test by a pare of rollers bending fatigue test by a fixed guide number of cycles number of broken wires number of cycles number of broken wires number of cycles when the rope was broken Ex. 1 20000 0 20000 0 72000 Ex. 2 20000 0 20000 0 69000 Ex. 3 20000 0 20000 0 132000 Ex. 4 20000 0 20000 0 127000 Ex. 5 20000 0 20000 0 70000 Ex. 6 20000 0 20000 0 186000 Com.Ex.1 20000 0 20000 63 25000 Com.Ex.2 20000 0 20000 18 31000 Com.Ex.3 20000 0 20000 17 31000 According to the test result shown in Table 2 any breakage was not found in the examples 1 to 6 and the comparative examples 1 to 3 on the bending fatigue test by a pair rollers at 20000 cycles. However, on the test by a fixed guide, 63 pieces of the wires were broken at 20000 cycles in the comparative example 1. In the comparative example 2, 18 pieces of the wires were broken and in the comparative example 3, 17 pieces of the wire were broken at 20000 cycles. On the contrary, any breakage of a wire was not found in examples 1 to 6 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 the comparative example 1 and the rope was broken at 31000 cycles in the comparative examples 2 and 3. On the contrary, it was found that the durability of examples 1, 2 and 5 were more than two times as much as that of comprative examples 1 to 3, the durability of examples 3 and 4 were more than four times as much as that of the comparative examples 1 to 3, and the durability of the example 6 was more than six times as much as that of comparative examples 1 to 3. 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 the examples 1 to 6 and the comparative examples 1 to 3. 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 durability. On the other hand, comparing the example 1 with the example 5, 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). Besides, the examples 1 to 6 having 19+8x7 construction or W(19)+8x7 construction have the same characteristic. However, it is natural that a rope having, for instance, 7x7 construction using large-diameter-wire or 7x19 construction has the same effect. 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 the control cable for the window regulator of the automobile.

Claims: Rope for operating, comprising a plurality of strands in closed arrangement, each strand being composed of a plurality of stranded wires, characterized in that, the tightening percentage of the rope is in the range of 4 to 11 % and the preforming percentage of the rope is in the range of 65 to 90 %. Rope of claim 1, wherein the strands are closed to have 19+8x7 construction. Rope of claim 1 or 2, wherein the wires of the core strand of the rope are stranded to have a parallel lay construction. Rope of claim 3, wherein the rope has a (parallel lay strand)+8x7 construction. Rope of one of claims 1 to 4, wherein superior corrosion resistance steel wire is used for the side strands. Rope of one of claim 1 to 4, wherein wire plated with zinc-aluminum alloy is used for the side strands.

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