Pulling system and pulling method

Abstract

A pulling system (101) comprises a main pulling device (P1) and intermediate pulling devices (P2, P3), wherein the main pulling device (P1) comprises: a pulling unit (61) that pulls an optical cable (6); a pull control unit (13) that controls the pulling speed of the optical cable (6); a generating unit (12) that generates a control signal for controlling the speed at which the optical cable (6) is conveyed by the intermediate pulling devices (P2, P3); and a first communication unit (11) that applies the control signal to a tension member (7) disposed along the longitudinal direction of the optical cable (6). The intermediate pulling devices (P2, P3) each comprise: a conveying unit that feeds out the optical cable (6) to an upstream side; a second communication unit (21, 31) that receives a control signal applied to a communication medium; and a conveying control unit (22, 32) that controls the speed at which the optical cable (6) is fed out by the conveying unit, on the basis of the control signal received by the second communication unit (21, 31).

Description

Traction System and Traction Method

[0001] The present disclosure relates to a traction system and a traction method for use when laying cables.

[0002] When laying a cable such as an optical cable into a conduit or the like, a cable traction device is used. When laying a long-distance cable by means of a cable traction device, the frictional force between the cable and the conduit or the like increases, and the tension applied to the cable increases. For this reason, a main traction device is installed at the tip of the cable, and an intermediate traction device is further installed at an intermediate point to equalize the tension applied to the cable.

[0003] The main traction device and each intermediate traction device need to be operated in conjunction with each other. For this reason, the main traction device and each intermediate traction device are connected by a control cable, and a control signal is transmitted from the main traction device to each intermediate traction device to control the traction speed of the cable to be constant, thereby preventing excessive tension from being applied to the cable.

[0004] Japanese Unexamined Patent Publication No. Hei 6-38326

[0005] Depending on the environment where the cable is laid, it may be difficult to arrange the control cable. Therefore, Patent Document 1 discloses a technology that detects the tension applied to a cable and controls each intermediate traction device so as to achieve a feeding speed corresponding to the tension.

[0006] However, with the method of detecting tension, it is difficult to make the feeding speed of each intermediate traction device follow the traction speed of the main traction device with good responsiveness. For this reason, there has been a problem that it is difficult to stably control the tension applied to the cable to be laid.

[0007] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a traction system and a traction method that can lay a cable by equalizing the tension applied to the cable without using a control cable.

[0008] A traction system according to one aspect of the present disclosure is a traction system comprising a main traction device and at least one intermediate traction device, wherein the main traction device comprises a traction unit for traction of a cable, a traction control unit for controlling the traction speed of the cable, a generation unit for generating a control signal for controlling the transport speed of the cable by the intermediate traction device, and a first communication unit for applying the control signal to a communication medium arranged along the longitudinal direction of the cable, and the intermediate traction device comprises a transport unit for sending the cable upstream, a second communication unit for receiving the control signal applied to the communication medium, and a transport control unit for controlling the transport speed of the cable sent out by the transport unit based on the control signal received by the second communication unit.

[0009] A towing method according to one aspect of the present disclosure is a towing method performed by a towing system comprising a main towing device and at least one intermediate towing device, wherein the main towing device tows the cable at a towing speed set by a towing control unit, generates a control signal to control the cable transport speed of the intermediate towing device, applies the control signal to a communication medium arranged along the longitudinal direction of the cable, the intermediate towing device receives the control signal applied to the communication medium, and transports the cable upstream at a transport speed based on the control signal received by the second communication unit.

[0010] According to this disclosure, it becomes possible to lay cables with uniform tension applied to them without using control cables.

[0011] Figure 1 is an explanatory diagram showing the installation of an optical cable using a traction system. Figure 2 is a perspective view showing the configuration of an optical cable. Figure 3 is a block diagram showing the configuration of a traction system according to the first embodiment. Figure 4 is a block diagram showing the configuration of a traction system according to the second and third embodiments. Figure 5 is a graph showing the relationship between the frequency set by the frequency control unit and the transport speed. Figure 6A is an explanatory diagram showing an example of the frequency to be assigned to each of the five intermediate transport devices A to E when five intermediate transport devices A to E are installed. Figure 6B is an explanatory diagram showing an example of the frequency to set the transport speed of the optical cable in each intermediate transport device. Figure 7 is a block diagram showing the configuration of a traction system according to the fourth embodiment. Figure 8 is an explanatory diagram showing the various measurement data detected by the intermediate traction device. Figure 9 is a perspective view showing the configuration of an optical cable according to a modified example. Figure 10 is an explanatory diagram showing the process of attaching metal tape to the outer sheath of a non-inductive optical cable. Figure 11 is an explanatory diagram showing the process of peeling off the metal tape of a non-inductive optical cable laid underground inside a manhole. Figure 12 is a block diagram showing the hardware configuration of this embodiment.

[0012] [Description of the First Embodiment] Hereinafter, embodiments will be described with reference to the drawings. Figure 1 is a schematic diagram illustrating how an optical cable 6 is laid using the traction system 101 according to the first embodiment. The traction system 101 pulls the optical cable 6 and lays it, for example, in a conduit.

[0013] As shown in Figure 1, the traction system 101 includes a main traction device P1 and a plurality of intermediate traction devices P2 and P3 (two in the figure). Although Figure 1 shows two intermediate traction devices P2 and P3, the number of intermediate traction devices may be one or three or more. Furthermore, although this embodiment describes an example of laying an optical cable 6, the cable to be laid is not limited to an optical cable 6, and can also be applied to other cables such as power cables.

[0014] As shown in Figure 1, the main traction device P1 comprises a traction unit 61 and a main control device 1. The main traction device P1 connects a metal traction rope 5 to a traction end 4 installed at the tip of the optical cable 6, and drives the traction unit 61 to pull the traction rope 5.

[0015] The intermediate traction device P2 comprises a pair of transport rollers 51 and 52 (transport section) and a transport control device 2. Each transport roller 51 and 52 is installed at an appropriate location on the optical cable 6 being laid. Each transport roller 51 and 52 grips the optical cable 6 and, under the control of the transport control device 2, drives each transport roller 51 and 52 to transport the optical cable 6 in the traction direction (right side in the figure). Hereafter, the traction direction of the optical cable 6 will be defined as the "upstream side," and the opposite direction (left side in the figure) will be defined as the "downstream side." That is, each transport roller 51 and 52 is installed downstream of the main traction device P1 and functions as a transport section that sends the optical cable 6 to the upstream side.

[0016] Similarly, the intermediate traction device P3 includes a pair of transport rollers 53 and 54 and a transport control device 3. Each transport roller 53 and 54 is installed at an appropriate location on the optical cable 6 being laid. Each transport roller 53 and 54 grips the optical cable 6 and, under the control of the transport control device 3, drives each transport roller 53 and 54 (transport section) to transport the optical cable 6 upstream. That is, each transport roller 53 and 54 is installed downstream of the main traction device P1 and functions as a transport section that sends the optical cable 6 upstream.

[0017] Figure 2 is a perspective view showing the detailed configuration of the optical cable 6. As shown in Figure 2, the optical cable 6 is formed in a long shape with a circular cross-section. The central part of the optical cable 6 is the optical fiber section 9, which is provided with an optical fiber core and cladding. An outer sheath 8 is provided around the optical fiber section 9. Two metal tension members 7 are provided on the outer sheath 8, extending along the longitudinal direction of the optical cable 6.

[0018] The tension members 7 are electrically connected to the tow rope 5 (see Figure 1). Both tension members 7 may be connected to the tow rope 5, or only one of the tension members 7 may be connected to the tow rope. As will be described later, the tow rope 5 and the tension members 7 serve as a communication medium for transmitting electromagnetic waves or radio waves.

[0019] Figure 3 is a block diagram showing the detailed configuration of the main control device 1 and transport control devices 2 and 3 mounted on the traction system 101 shown in Figure 1. As shown in Figure 3, the main control device 1 includes a first communication unit 11, a generation unit 12, and a traction control unit 13.

[0020] The traction control unit 13 controls the drive of the traction unit 61 in response to the operator's input or other control inputs. For example, if the operator inputs a traction speed v1 [m / min], the control unit 13 outputs a control command to the traction unit 61 to traction the traction rope 5 at this traction speed v1.

[0021] The generation unit 12 generates control signals to control the transport speed of the optical cable 6 by each intermediate traction device P2 and P3. For example, if the traction speed of the traction rope 5 by the traction unit 61 is v1, the generation unit 12 generates a control signal to set the transport speed of the optical cable 6 by each transport roller 51 and 52 of the intermediate traction device P2 to speed v1. Similarly, the generation unit 12 generates a control signal to set the transport speed of the optical cable 6 by each transport roller 53 and 54 of the intermediate traction device P3 to speed v1. Depending on the characteristics of the optical cable 6, the surrounding environment, and other conditions, it is also possible to set the transport speed of the optical cable 6 by the intermediate traction devices P2 and P3 to a speed different from speed v1 (for example, a speed slightly slower than speed v1).

[0022] The first communication unit 11 applies the control signal s1 generated by the generation unit 12 to the metal traction rope 5. The control signal s1 may also be applied directly to the tension member 7 located on the optical cable 6. Thus, the traction rope 5 and the tension member 7 act as waveguides, allowing the control signal s1 to be transmitted to the intermediate traction devices P2 and P3 installed downstream. The tension member 7 is an example of a communication medium that transmits and receives electromagnetic waves or radio waves.

[0023] The transport control device 2 includes a second communication unit 21 and a transport control unit 22.

[0024] The second communication unit 21 receives the control signal s1 transmitted from the main control unit 1 via the tension member 7.

[0025] The transport control unit 22 controls the drive of each transport roller 51, 52 based on the control signal s1 received by the second communication unit 21. Therefore, the control commands included in the control signal s1 transmitted from the main control unit 1 control each transport roller 51, 52 to rotate at a desired speed, and consequently the optical cable 6 can be transported upstream at a desired transport speed (for example, speed v1).

[0026] The transport control device 3 includes a second communication unit 31 and a transport control unit 32. The transport control device 3 has the same configuration as the transport control device 2 described above. Therefore, the control commands included in the control signal s1 transmitted from the main control device 1 control each transport roller 53, 54 to a desired rotational speed, and thereby the optical cable 6 can be transported upstream at a desired transport speed (for example, speed v1).

[0027] Next, the operation of the traction system 101 according to the first embodiment, configured as described above, will be explained. The traction control unit 13 of the main control device 1 controls the drive of the traction unit 61 so that the traction speed of the optical cable 6 by the traction rope 5 becomes a desired speed v1. As a result, the traction rope 5 pulls the optical cable 6 at speed v1.

[0028] The generation unit 12 generates control signals s1 for controlling each of the intermediate traction devices P2 and P3 and outputs them to the first communication unit 11. The control signals s1 include a control command to set the transport speed of the optical cable 6 by the intermediate traction devices P2 and P3. The transport speed of the optical cable 6 by the intermediate traction devices P2 and P3 is set to the same speed v1 as the traction speed by the traction unit 61, for example.

[0029] The first communication unit 11 applies the control signal s1 generated by the generation unit 12 to the tension member 7 (communication medium) mounted on the optical cable 6 via the metal traction rope 5.

[0030] The second communication unit 21 of the intermediate traction device P2 receives the control signal s1 transmitted via the tension member 7. Based on the control commands included in this control signal s1, the transport control unit 22 controls the drive of the transport rollers 51 and 52 so that the transport speed of the optical cable 6 becomes speed v1.

[0031] Meanwhile, the second communication unit 31 of the intermediate traction device P3 receives the control signal s1 transmitted via the tension member 7. Based on the control commands included in this control signal s1, the transport control unit 32 controls the drive of the transport rollers 53 and 54 so that the transport speed of the optical cable 6 becomes speed v1.

[0032] Thus, in this embodiment, the traction system 101 comprises a main traction device P1 and at least one intermediate traction device P2, P3, wherein the main traction device P1 comprises a traction unit 61 for traction of the optical cable 6, a traction control unit 13 for controlling the traction speed of the optical cable 6, a generation unit 12 for generating a control signal for controlling the transport speed of the optical cable 6 by the intermediate traction devices P2, P3, and a first communication unit 11 for applying the control signal to a communication medium (e.g., a tension member 7) arranged along the longitudinal direction of the optical cable 6. The intermediate traction devices P2, P3 comprise a transport unit (e.g., transport rollers 51-54) for sending the optical cable 6 upstream, second communication units 21, 31 for receiving the control signal applied to the communication medium, and transport control units 22, 32 for controlling the transport speed of the optical cable 6 based on the control signal received by the second communication units 21, 31.

[0033] In the traction system 101 according to this embodiment, the optical cable 6 is towed by the main traction device P1, and when laying the optical cable 6 over a long distance, the intermediate portion of the optical cable 6 is fed upstream by intermediate traction devices P2 and P3. The transport speed when feeding out the optical cable 6 at the intermediate portion is set in synchronization with the traction speed v1 of the main traction device P1. For example, the transport speed is set to the same speed as the traction speed v1, or slightly slower. That is, each intermediate traction device P2 and P3 can be driven in conjunction with the main traction device P1. Therefore, it becomes possible to lay the optical cable 6 in a conduit or the like by towing it with almost uniform tension without applying excessive tension to the optical cable 6.

[0034] Furthermore, the metal tension member 7 mounted on the optical cable 6 is used as a communication medium to transmit control signals s1 from the main control device 1 to each transport control device 2 and 3. Therefore, there is no need to lay a separate control cable from the optical cable 6 as in conventional systems, making it possible to lay the optical cable 6 with simple operation. Additionally, the optical cable 6 can be laid using the intermediate traction devices P2 and P3 even in locations where laying control cables is difficult, such as public roads.

[0035] In this embodiment, since control cables are not required, the cost of laying the optical cable 6 can be reduced. Furthermore, by increasing the number of intermediate traction devices installed, it becomes possible to lay the optical cable 6 over long distances.

[0036] [Description of the Second Embodiment] Next, a second embodiment will be described. Figure 4 is a block diagram showing the configuration of the towing system 102 according to the second embodiment. As shown in Figure 4, the towing system 102 according to the second embodiment differs from the configuration shown in Figure 3 in that the main control device 1A mounted on the main towing device P1 and the transport control devices 2A and 3A mounted on each of the intermediate towing devices P2 and P3 are configured differently.

[0037] The main control unit 1A differs from the main control unit 1 shown in Figure 3 in that it includes a frequency control unit 14. The transport control units 2A and 3A also differ from the transport control units 2 and 3 shown in Figure 3 in that they include detection units 23 and 33. The other components are the same as those in Figure 2, so the same reference numerals are used and their descriptions are omitted.

[0038] The frequency control unit 14 frequency modulates the control signal generated by the generation unit 12. As shown in the graph in Figure 5 (details will be described later), the frequency control unit 14 has a correspondence table that associates the transport speed [m / min] with the frequency [Hz], and modulates the control signal to be transmitted to each intermediate traction device P2, P3 to the desired frequency based on this correspondence table.

[0039] The detection units 23 and 33 detect the frequency of the control signal s1 received by the second communication units 21 and 31.

[0040] Figure 5 is a graph showing the relationship between the frequency set by the frequency control unit 14 and the transport speed. As shown in Figure 5, in the region where the frequency of the control signal s1 is below the threshold f0, the transport speed is set to 0 [m / sec] (i.e., stopped), and when the frequency exceeds the threshold f0, the transport speed is set to a negative value (i.e., backward), and the transport speed increases linearly as the frequency increases. Furthermore, when the frequency reaches f1, the transport speed changes from a negative value to a positive value (i.e., forward).

[0041] For example, when the frequency control unit 14 sets the transport speed of the optical cable 6 by the intermediate traction devices P2 and P3 to x [m / min], it modulates the control signal to a frequency corresponding to this transport speed.

[0042] The detection units 23 and 33 mounted on each transport control device 2 and 3 detect the frequency of the control signal s1 received by the second communication units 21 and 31 and acquire a command to set the transport speed. Each detection unit 23 and 33 outputs the acquired command to the transport control units 22 and 32. The transport control units 22 and 32 control the driving of the transport rollers 51 and 52 and the transport rollers 53 and 54 so that the transport speed is set. As a result, the optical cable 6 can be transported by the intermediate traction devices P2 and P3 at the desired transport speed, for example, the traction speed v1 of the main traction device P1.

[0043] As described above, in the pulling system 102 according to the second embodiment, the main control device 1 modulates the control signal s1 into a frequency corresponding to the conveyance speed set by each of the intermediate pulling devices P2 and P3, and transmits the modulated control signal s1 to each of the conveyance control devices 2 and 3. Therefore, it is possible to easily set the conveyance speed of the optical cable 6 in each of the intermediate pulling devices P2 and P3.

[0044] In the second embodiment, it is possible to easily switch between forward movement (conveyance to the upstream side) and backward movement (conveyance to the downstream side) of the optical cable 6. Furthermore, in a frequency band equal to or lower than a constant frequency (f0), conveyance by each of the intermediate pulling devices P2 and P3 is stopped, so that malfunctions can be prevented.

[0045] In the second embodiment, the metallic tension member 7 mounted on the optical cable 6 is used as a communication medium, and the control signal s1 is transmitted from the main control device 1 to each of the conveyance control devices 2 and 3. Therefore, as in the first embodiment described above, there is no need to arrange a control cable separate from the optical cable 6, and the optical cable 6 can be laid by a simple operation.

[0046] [Description of Third Embodiment] Next, the third embodiment will be described. A pulling system 103 according to the third embodiment has the same configuration as that of FIG. 4 described above. In contrast to the second embodiment, the function of the frequency control unit 14 is different.

[0047] The frequency control unit 14 individually sets frequencies for transmitting control signals to each of the conveyance control devices 2 and 3, and modulates the control signal s1 with the set frequencies. For example, when the conveyance speed of the optical cable 6 is set to a speed v2 slightly slower than the speed v1 for the conveyance control device 2, and the conveyance speed of the optical cable 6 is set to a speed v3 slightly slower than the speed v2 for the conveyance control device 3, the respective setting command signals are modulated at different frequencies.

[0048] For example, a control command S1 to be transmitted to the conveyance control device 2 is modulated with a first frequency f11, a control command S2 to be transmitted to the conveyance control device 3 is modulated with a second frequency f12, and the control signal s1 is generated by superimposing each of the modulated signals. This control signal s1 is applied to the tension member 7.

[0049] The detection unit 23 of the transport control device 2 extracts a control command S1 with frequency f11 from the control signal s1. The transport control unit 22 controls the driving of the transport rollers 51 and 52 based on the control command S1. As a result, the optical cable 6 can be transported in the intermediate traction device P2 at, for example, a speed v2 (v2 < v1).

[0050] Meanwhile, the detection unit 33 of the transport control device 3 extracts a control command S2 with frequency f12 from the control signal s1. The transport control unit 32 controls the driving of the transport rollers 53 and 54 based on the control command S2. As a result, the optical cable 6 can be transported in the intermediate traction device P3 at, for example, a speed v3 (v3 < v2).

[0051] Figure 6A is an explanatory diagram showing an example of the frequencies to be assigned to each of the five intermediate transport devices A to E when five intermediate transport devices A to E are installed to transport the optical cable 6 in the middle. For example, a bandwidth of 100 Hz may be assigned to intermediate transport device A, a bandwidth of 200 Hz to intermediate transport device B, a bandwidth of 300 Hz to intermediate transport device C, a bandwidth of 400 Hz to intermediate transport device D, and a bandwidth of 500 Hz to intermediate transport device E. By assigning different frequency bandwidths to each of the intermediate transport devices A to E, it becomes possible to set the transport speed individually.

[0052] Figure 6B is an explanatory diagram showing examples of frequencies for setting the transport speed of the optical cable 6 in each intermediate transport device A to E. A transport speed of 0 to 50 m / min is associated with a control signal frequency of 10 to 510 Hz. For example, when the frequency is 110 Hz, the transport speed is set to 10 m / min. Furthermore, control commands can be set such that if there is "no" additional signal, the optical cable 6 is moved forward (transported upstream), when the frequency is 1 kHz, the optical cable 6 is moved backward (transported downstream), when the frequency is 2 kHz, the optical cable 6 is moved forward at a slow speed, when the frequency is 3 kHz, the optical cable 6 is moved backward at a slow speed, and when the frequency is 4 kHz, the optical cable 6 is brought to an emergency stop. For example, a control signal with frequencies 110 Hz and 1 kHz superimposed will be a control signal indicating that the optical cable 6 should be moved backward at a transport speed of 10 m / min. Alternatively, the conditions of both Figure 6A and Figure 6B may be combined and transmitted as a control signal.

[0053] In the traction system 103 according to the third embodiment, the frequency control unit 14 of the main control device 1 generates a control signal s1 by modulating the control command at the frequency set for each transport control device 2, 3, and applies this control signal s1 to the tension member 7. This makes it possible to individually set the transport speed of the optical cable 6 by each transport control device 2, 3. For example, it is possible to set the transport speed v2 by the intermediate traction device P2 to a speed slightly slower than the traction speed v1 by the main traction device P1, and to set the transport speed v3 by the intermediate traction device P3 to a speed slightly slower than the transport speed v2.

[0054] Furthermore, each intermediate traction device P2 and P3 can individually control the forward and backward movement of the optical cable 6. In addition, the metal tension member 7 mounted on the optical cable 6 is used as a communication medium to transmit control signals s1 from the main control device 1 to each transport control device 2 and 3. Therefore, as with the first embodiment described above, there is no need to arrange a separate control cable from the optical cable 6, and the optical cable 6 can be laid with simple operation.

[0055] [Description of the Fourth Embodiment] Next, the fourth embodiment will be described. Figure 7 is a block diagram showing the configuration of the towing system 104 according to the fourth embodiment. As shown in Figure 7, the towing system 104 according to the fourth embodiment differs from the configuration shown in Figure 3 in that the main control device 1B and the transport control devices 2B and 3B are different.

[0056] The main control unit 1B differs from the main control unit 1 shown in Figure 3 in that the first communication unit 11 performs bidirectional communication and the generation unit 12 generates a digitized control signal s2. Specifically, the first communication unit 11 applies the digitized control signal s2 to the tension member 7 and receives the measurement signal s3 transmitted from each transport control unit 2B, 3B via the tension member 7.

[0057] The transport control devices 2B and 3B differ from the transport control devices 2 and 3 shown in Figure 3 in that the second communication units 21 and 31 perform bidirectional communication and that they are equipped with measuring units 26 and 36. The other components are the same as those in Figure 3, so the same reference numerals are used and their configuration descriptions are omitted.

[0058] The first communication unit 11 of the main control device 1B applies the digital control signal s2 generated by the generation unit 12 to the tension member 7 of the optical cable 6. The control signal s2 includes a control command to be transmitted to each transport control device 2B, 3B and a destination. Therefore, a control command can be set and transmitted individually for each transport control device 2B, 3B. The first communication unit 11 receives the measurement signal s3 (details will be described later) transmitted from each transport control device 2B, 3B. Based on the received measurement signal, the first communication unit 11 performs feedback control of the control signal s2 to be transmitted to each transport control device 2B, 3B.

[0059] The second communication units 21 and 31 of the transport control devices 2B and 3B receive the control signal s2 transmitted from the main control device 1B. The second communication units 21 and 31 digitize the measurement data measured by the measurement units 26 and 36 (details will be described later), generate a measurement signal s3, apply it to the tension member 7 of the optical cable 6, and transmit it to the main control device 1B. In other words, the first communication unit 11 of the main control device 1B and the second communication units 21 and 31 of each transport control device 2B and 3B perform bidirectional digital communication via the tension member 7.

[0060] The measurement units 26 and 36 include sensors (not shown) mounted on the intermediate traction devices P2 and P3, and acquire measurement data from each sensor. Specifically, as shown in Figure 8, the measurement units 26 and 36 acquire measurement data of the transport torque q1 of the optical cable 6 by the transport rollers 51 and 52 and the transport rollers 53 and 54, the transport speed q2 of the optical cable 6, and the slack q3 generated in the optical cable 6. The slack q3 can be detected, for example, by a pressure sensor (not shown). Note that the detected values ​​measured by the measurement units 26 and 36 are not limited to these, and other measurement data may be acquired. The measurement units 26 and 36 convert the acquired measurement data into digital signals and output them to the second communication units 21 and 31.

[0061] Next, the operation of the traction system 104 according to the fourth embodiment, configured as described above, will be explained. The traction control unit 13 of the main control device 1B controls the drive of the traction unit 61 so that the traction speed of the optical cable 6 by the traction rope 5 becomes a desired speed v1. As a result, the traction rope 5 pulls the optical cable 6 at speed v1.

[0062] The generation unit 12 digitizes the control signals s2 for controlling each of the intermediate traction devices P2 and P3 and outputs them to the first communication unit 11. The control signals s2 include, for example, a command to set the transport speed of the optical cable 6 by the intermediate traction devices P2 and P3 to the same speed v1 as that of the main traction device P1. Alternatively, it includes a command to set the transport speed of the optical cable 6 by the intermediate traction device P2 to a speed v2 that is slightly slower than the traction speed v1 of the main traction device P1, and the transport speed of the optical cable 6 by the intermediate traction device P3 to a speed v3 that is slightly slower than speed v2.

[0063] The first communication unit 11 applies the control signal s2 generated by the generation unit 12 to the tension member 7 (communication medium) mounted on the optical cable 6.

[0064] The second communication unit 21 of the intermediate traction device P2 receives the control signal s2 transmitted via the tension member 7. Based on the control commands included in this control signal s2, the transport control unit 22 controls the drive of the transport rollers 51 and 52 so that the transport speed of the optical cable 6 becomes the desired speed.

[0065] In the intermediate traction device P2, the measurement unit 26 measures the transport torque q1 by the transport rollers 51 and 52, the transport speed q2, and the slack q3 generated in the optical cable 6, generates a digitized measurement signal s3 from the measurement data, and feeds it back to the main control device 1B. The generation unit 12 of the main control device 1B controls the control signal s2 to be transmitted to the transport control device 2B to be an appropriate signal based on the measurement data contained in the fed-back measurement signal s3.

[0066] Meanwhile, the second communication unit 31 of the intermediate traction device P3 receives the control signal s2 transmitted via the tension member 7. Based on the control commands included in this control signal s2, the transport control unit 32 controls the drive of the transport rollers 53 and 54 so that the transport speed of the optical cable 6 becomes the desired speed.

[0067] In the intermediate traction device P3, the measurement unit 36 ​​measures the transport torque q1, transport speed q2, and slack q3 generated in the optical cable 6 by the transport rollers 53 and 54, generates a digitized measurement signal s3 from the measurement data, and feeds it back to the main control device 1B. The generation unit 12 of the main control device 1B controls the control signal s2 to be transmitted to the transport control device 3B to be an appropriate signal based on the measurement data contained in the fed-back measurement signal s3.

[0068] As described above, in the traction system 104 according to the fourth embodiment, by performing bidirectional communication using digital signals between the main control device 1B and each transport control device 2B, 3B, the measured data of transport torque q1, transport speed q2, and slack q3 measured in each transport control device 2B, 3B are fed back, and the control signal output by the generation unit 12 of the main control device 1B is adjusted. As a result, the transport of the optical cable 6 by each intermediate traction device P2, P3 can be controlled with higher precision, and the tension generated in the optical cable 6 can be stabilized.

[0069] Furthermore, since the metal tension member 7 mounted on the optical cable 6 is used as a communication medium to send and receive control signals s2 and measurement signals s3, there is no need to arrange a separate control cable from the optical cable 6, as in the first embodiment described above, and the optical cable 6 can be laid with extremely simple operation.

[0070] [Explanation of Modified Examples] Next, modified examples of the first to fourth embodiments described above will be explained. In the first to fourth embodiments described above, an example was described in which a metal tension member 7 is arranged on the outer sheath 8 of the optical cable 6. That is, an example was described in which the optical cable 6 is equipped with a metal tension member 7 and this tension member 7 is used as a communication medium for transmitting control signals.

[0071] In a modified example, when using a non-inductive optical cable 6A that does not have a metal tension member, a metal tape 10 is attached to the surface of the outer sheath of the non-inductive optical cable 6A, and this metal tape 10 is used as the communication medium. This will be explained in detail below with reference to Figures 9 to 11.

[0072] Figure 9 is a perspective view showing a non-inductive optical cable 6A with metal tape 10 attached to two locations on its outer sheath 8, along the longitudinal direction of the non-inductive optical cable 6A. The two tension members 7A mounted on the non-inductive optical cable 6A shown in Figure 9 are made of non-metallic strips. By arranging the metal tape 10 along the longitudinal direction of the outer sheath 8 of the non-inductive optical cable 6A, the metal tape 10 is used as a communication medium. That is, by applying a control signal s1 to the metal tape 10, the control signal s1 is transmitted from the main control device 1 to the transport control devices 2 and 3.

[0073] Figure 10 is a schematic diagram illustrating the process of attaching two metal tapes 10 to the outer sheath 8 of a non-inductive optical cable 6A. As shown in Figure 10, the non-inductive optical cable 6A is removed from the cable drum 73 on which it is wound using a pair of pressure rollers 74 and 75. Tape drums 71 and 72, on which insulated metal tapes 10 are wound, are placed between the cable drum 73 and each of the pressure rollers 74 and 75, and the metal tapes 10 are attached to the outer circumference of the non-inductive optical cable 6A. As a result, the non-inductive optical cable 6A shown in Figure 9 can be created.

[0074] Since the metal tape 10 is insulated, even if the metal tape 10 comes into contact with a conduit or the like, short circuits and leakage of control signals can be avoided.

[0075] In other words, in a non-inductive optical cable 6A where the tension member 7A is a non-metallic strip, the control signal s1 cannot be applied to the tension member 7A. In a modified example, an insulated metal tape 10 is attached to the outer sheath 8 of the non-inductive optical cable 6A, and the control signal s1 is applied to this metal tape 10. As a result, even when using the non-inductive optical cable 6A, it becomes possible to transmit the control signal s1 in the same way as when using the optical cable 6 described above. Note that one metal tape 10 may be used. In this case, one end of the metal tape 10 is grounded.

[0076] Furthermore, as shown in Figure 11, when inserting the non-inductive optical cable 6A into a manhole 81 buried from the ground level (GL), after laying the non-inductive optical cable 6A, the metal tape 10 of the non-inductive optical cable 6A inside the manhole 81 can be removed to limit the induced voltage, thereby eliminating the need for induction countermeasures.

[0077] As shown in Figure 12, the main control unit 1 and transport control units 2 and 3 of this embodiment described above can use a general-purpose computer system that includes, for example, a CPU (Central Processing Unit, processor) 901, memory 902, storage 903 (HDD: Hard Disk Drive, SSD: Solid State Drive), communication device 904, input device 905, and output device 906. The memory 902 and storage 903 are storage devices. In this computer system, the functions of the main control unit 1 and transport control units 2 and 3 are realized when the CPU 901 executes a predetermined program loaded onto the memory 902.

[0078] The main control unit 1 and the transport control units 2 and 3 may be implemented on a single computer, or on multiple computers. Furthermore, the main control unit 1 and the transport control units 2 and 3 may be virtual machines implemented on a computer.

[0079] The programs for the main control unit 1 and the transport control units 2 and 3 can be stored on computer-readable recording media such as HDDs, SSDs, USB (Universal Serial Bus) memory, CDs (Compact Discs), and DVDs (Digital Versatile Discs), or they can be distributed via a network. Computer-readable recording media are, for example, non-transitory recording media.

[0080] This disclosure is not limited to the embodiments described above, and numerous modifications are possible within the scope of its essence.

[0081] 1, 1A, 1B Main control device 2, 2A, 2B Conveying control device 3, 3A, 3B Conveying control device 4 Traction end 5 Traction rope 6 Optical cable 6A Non-inductive optical cable 7 Tension member (communication medium) 8 Outer sheath 10 Metal tape 11 First communication unit 12 Generation unit 13 Traction control unit 14 Frequency control unit 21, 31 Second communication unit 22, 32 Conveying control unit 23, 33 Detection unit 26, 36 Measurement unit 51, 52 Conveying roller (conveying unit) 53, 54 Conveying roller (conveying unit) 61 Traction unit 101, 102, 103, 104 Traction system P1 Main traction device P2, P3 Intermediate traction device

Claims

1. A traction system comprising a main traction device and at least one intermediate traction device, wherein the main traction device comprises: a traction unit for traction of a cable; a traction control unit for controlling the traction speed of the cable; a generation unit for generating a control signal for controlling the transport speed of the cable by the intermediate traction device; and a first communication unit for applying the control signal to a communication medium arranged along the longitudinal direction of the cable, and the intermediate traction device comprises: a transport unit for sending the cable upstream; a second communication unit for receiving the control signal applied to the communication medium; and a transport control unit for controlling the cable delivery speed by the transport unit based on the control signal received by the second communication unit.

2. The traction system according to claim 1, wherein a plurality of intermediate traction devices are installed, the control signal includes a control command to be transmitted to each of the intermediate traction devices, the main traction device further comprises a frequency control unit that frequency modulates the control command to be transmitted to each intermediate traction device to a different frequency, and each of the intermediate traction devices further comprises a detection unit that detects a control command of a desired frequency from the control signal received by the second communication unit.

3. The traction system according to claim 1, wherein the intermediate traction device further comprises a measuring unit that measures at least one of the transport torque in the transport unit, the traction speed of the cable, and the slack generated in the cable, the second communication unit transmits the measurement data from the measuring unit to the main traction device, and the traction control unit controls the traction speed of the cable by the traction unit based on the measurement data received by the first communication unit.

4. A traction method performed by a traction system comprising a main traction device and at least one intermediate traction device, wherein the main traction device tractions the cable at a traction speed set by a traction control unit, generates a control signal to control the cable transport speed of the intermediate traction device, applies the control signal to a communication medium arranged along the longitudinal direction of the cable, and the intermediate traction device receives the control signal applied to the communication medium and transports the cable upstream at a transport speed based on the control signal received by the second communication unit.

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