Cable reel control system and method

Abstract

A cable rell apparatus for a work machine 2 has a rotatable reel 6 for carrying a cable 3 and a reel drive 10, that may be an electric or hydraulic motor. A controller 12 is in communication with a re

Description

Field of the Invention The present invention is directed to the field of work machines and in particular to electric work machines which are connected to an electrical cable which provides power and / or data to the work machine. More specifically, the present invention is a reel system and method for handling the aforementioned cable. Background of the Invention With work machines which require electrical and / or data cables a distal end of the cable is attached to a remote location (such as an electrical power source, for example) and a proximal end of the cable is attached to the work machine. The majority of the cable is mounted upon a rotatable reel, which may be located at the remote location or else may be mounted upon the work machine itself. With the remote end of the cable attached to a fixed point the cable will be fed out from the reel as the machine moves over the terrain. With the cable feeding out from the reel it is important that the tension of the cable is kept within a predetermined operational range. If the cable tension is too high then the cable may be damaged as the machine pulls on the cable. If the tension is too low then the cable risks being damaged as it is pulled along the ground, or indeed crushed if another machine passes over the cable on the ground. A known solution to this problem is to provide an automated system which controls rotation of the cable reel and monitors the tension in the cable. With this solution the reel itself is powered, and so the feeding out or reeling in of the cable is controlled by the system rather than the reel being a passive component which simply rotates as the machine moves away from the remote location to which the distal cable end is connected. In these known systems a controller monitors information such as distance, machine speed and vector, and rate of acceleration. With this information the controller can then speed up or slow down the rotation of the powered cable reel to ensure the cable tension remains within an optimal range as the work machine moves across the terrain. These known systems typically employ a slip ring arrangement such that power and data can be transferred across the reel. Summary of the Invention There are several drawbacks with existing automated cable reel systems. Firstly, slips rings which transmit data rather than power alone are expensive. In addition, having to monitor distance, machine speed and vector and rate of acceleration means that the cable tension system can only be mounted upon the machine. Furthermore, if there is any inaccuracy in the readings provided to the controller, or there is a delay in the transmission of those readings, the system may not be able to keep the cable tension in the desired range. The present invention provides an accurate and cost-effective way of monitoring and controlling the tension in a cable reel apparatus when compared with existing solutions. There is also added flexibility in the system, allowing the apparatus itself to be positioned off-machine at a remote location as well as mounted upon the machine itself. According to a first aspect of the present invention there is provided a cable reel apparatus for a work machine. The apparatus comprises a rotatable reel body configured to carry a length of cable, and a reel drive configured to rotate the reel body in clockwise and anti-clockwise directions. A reel speed sensor is configured to measure a rotational speed of the reel body, and a cable tension sensor is configured to when in use measure a tension of a cable carried on the reel body. A controller is in communication with the sensors and the reel drive. The controller is configured to monitor signals from the sensors, and determine if the cable tension is within a predetermined range. If the cable tension is not within the predetermined range the controller calculates a desired reel speed that will bring the cable tension within the predetermined range, and instructs the reel drive to adjust to the desired reel speed. According to a second aspect of the present invention there is provided a work machine comprising a cable reel apparatus according to the first aspect. According to a third aspect of the present invention there is provided a method of controlling a cable reel apparatus comprising a rotatable reel body configured to carry a length of cable, and a reel drive configured to rotate the reel body in clockwise and anti-clockwise directions. The method comprises monitoring signals from (i) a reel speed sensor configured to measure a rotational speed of the reel body, and (ii) a cable tension sensor configured to measure a tension of a cable carried on the reel body. It is determined if the cable tension is within a predetermined range. If the cable tension is not within the predetermined range a desired reel speed that will bring the cable tension within the predetermined range is calculated, and the reel drive is instructed to adjust to the desired reel speed. Brief Description of the Drawings Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a first embodiment of a cable reel apparatus on a work machine; Figure 2 shows a second embodiment of a cable reel apparatus on a work machine; and Figure 3 shows a flow diagram illustrating a method of controlling a cable reel apparatus. Detailed Description of the Drawings A first embodiment of a cable reel apparatus suitable for a work machine is shown in Figure 1. Whilst the apparatus will be described in use on a work machine - in this case an excavator - is should be understood that the apparatus in not limited to this specific application and may be employed on other wheeled or tracked equipment, such as off-highway vehicles for example. As seen in Figure 1 a work machine (excavator), generally designated 2, has a cable reel 4 mounted to the rear portion thereof. The cable reel 4 is configured to store and dispense a length of cable 3. The work machine 2 in this preferred embodiment is electrically-powered and the cable has a distal end 5 which in use will be connected to a fixed base station (not shown), as well as a proximal end 7 which is connectable to the work machine 2. The cable 3 supplies electrical power to the work machine 2. It may also transfer data between the base station and the work machine 2. The cable reel 4 comprises a reel body 6 upon which the cable 3 is carried, and a reel support 8 upon which the reel body 6 is rotatably mounted. The reel support 8 also attaches the cable reel 4 to the work machine 2. The cable reel 4 as shown is attached to a rear portion of the cab, or house, 9 of the work machine 2. However, it may be attached or mounted to other portions of the work machine 2, such as to the underside of the cab 9 or else within or on an undercarriage 11 which supports and drives the cab, for example. The cable reel 4 is also shown having an axis of rotation R which is substantially horizontal, but the cable reel may alternatively be attached or mounted such that its axis of rotation is substantially vertical. The cable reel 4 also has a reel drive 10, which can rotate the reel body 6 in clockwise and anti-clockwise directions to reel in or feed out the cable 3. The reel drive 10 may be an electric drive motor but other drive arrangements may be more suited to particular environments, such as a hydraulic drive arrangement for example. A controller 12 is provided, which may be located on the cable reel 4 but as shown is located on the work machine 2. The controller 12 is in communication with the reel drive 10 such that the cable reel 4 will feed out or reel in the cable 3 depending upon the speed and direction of travel of the work machine 2. The cable reel apparatus further comprises at least one reel speed sensor 14, which is configured to measure the rotational speed of the reel body 6 and hence the speed at which the cable 3 is being reeled in or fed out. Provided upon the cable 3 itself is at least one tension sensor 16, which is configured to measure tension on the cable 3. The tension sensor 16 may be a strain gauge provided at a break in the cable in a known manner. Both the reel speed sensor 14 and tension sensor 16 are in communication with the controller 12 so that it may constantly monitor the reel speed and cable tension. An alternative arrangement of a cable reel apparatus is shown in Figure 2. Components shared with the embodiment shown in Figure 1 are allocated the same reference numbers and may not be described again here. An excavator work machine 2 is connected to a proximal end 7 of a cable 3, which supplies power to the work machine from a fixed base station (not shown) to which a distal end 5 of the cable is connected. A cable reel 4’ configured to store and dispense the cable 3 is provided adjacent the base station. The cable 3 may also transfer data between the base station and the work machine 2. The cable reel 4’ comprises a reel body 6’ upon which the cable 3 is carried, and a reel support 8’ upon which the reel body is rotatably mounted. The reel support 8’ attaches the cable reel 4’ to a foundation or directly to the ground. The cable reel 4’ is shown having an axis of rotation R’ which is substantially horizontal, but the cable reel may alternatively be arranged such that its axis of rotation is substantially vertical. The cable reel 4’ has a reel drive 10, which can rotate the reel body 6’ in clockwise and anti-clockwise directions to reel in or feed out the cable 3. The reel drive 10 may be of the same type as described in respect of the first embodiment. A controller 12 is provided, which may be located on the cable reel 4’ but as shown is located on the work machine 2. The controller 12 is in communication with the reel drive 10 such that the cable reel 4 will feed out or reel in the cable 3 depending upon the speed and direction of travel of the work machine 2. As with the first embodiment the cable reel apparatus further comprises at least one reel speed sensor 14, which is configured to measure the rotational speed of the reel body 6’ and hence the speed at which the cable 3 is being reeled in or fed out. This alternative embodiment may have at least one tension sensor provided on the cable in the same manner as the first embodiment. However, it is preferred that in this embodiment the tension sensor 16’ is in the form of a load cell or similar sensing component provided at the cable reel 4’. The tension sensor 16’ may be provided between the reel support 8’ and reel body 6’ so as to sense loads being placed upon the reel body. Both the reel speed sensor 14 and tension sensor 16 are in communication with the controller 12 so that it may constantly monitor the reel speed and cable tension. Industrial Applicability A method of controlling a cable reel apparatus, including those described above in reference to Figures 1 and 2, is shown in the flow diagram of Figure 3. At a first step 101 the speed of the reel body 6,6’ is measured by the reel speed sensor 14 and this speed is transmitted to the controller 12. The controller 12 has a memory, which may be integral with, or separate from, the controller. The memory may store the speeds measured by the reel speed sensor 14 over a period of time. At a second step 102 the tension of the cable 3 is measured by the tension sensor 16,16’ and this tension reading is also transmitted to the controller 12. Again, the memory may store tension values measured by the tension sensor 16,16’ over a period of time. Stored within the memory is at least one range of optimal tension values for the cable. These values are selected on the basis that the tension of the cable will remain within certain limits outside of which the cable may be damaged or broken. This can obviously occur on the one hand if there is too much tension on the cable. However, if the tension in the cable is too low it can become too loose and potentially drag along the ground, risking damage not only from that contact with the ground but also potentially being inadvertently run over by another vehicle or machine. For this reason a zero value for the tension is not included in the range of tension values. At the third step 103 the controller 12 determines if the cable tension reading from the tension sensor 16,16’ is within the optimal range. If it is determined that the cable tension is within the optimal range then step 104 tells the controller 12 not to change the speed of the reel body 6,6’, and the method reverts to reel speed measurement step 101. However, if it is determined that the tension is no longer within the optimal range step 105 has the controller apply a control algorithm to calculate a reel body speed that will bring the cable tension back in the desired range, whether this be increasing or decreasing the speed of the reel body 6,6’. Step 106 then has the controller 12 send the calculated new reel speed to the reel drive 10, whereupon the reel drive 10 will speed up or slow down the reel body 6,6’ to the required new speed and the tension of the cable will return to within the optimal tension range. The method is then repeated as the reel speed and cable tension are constantly monitored during operation and movement of the work machine 2. Modifications and improvements may be incorporated without departing from the scope of the present invention as defined by the appended claims.

Claims

1. A cable reel apparatus for a work machine, the apparatus comprising: a rotatable reel body configured to carry a length of cable;a reel drive configured to rotate the reel body in clockwise and anticlockwise directions;a reel speed sensor configured to measure a rotational speed of the reel body;a cable tension sensor configured to when in use measure a tension of a cable carried on the reel body; anda controller in communication with the sensors and the reel drive, the controller configured to:monitor signals from the sensors;determine if the cable tension is within a predetermined range; and if the cable tension is not within the predetermined range:calculate a desired reel speed that will bring the cable tension within the predetermined range; andinstruct the reel drive to adjust to the desired reel speed.

2. The cable reel apparatus of claim 1, further comprising a length of cable carried upon the reel body, the cable configured to supply power and / or data to the work machine, and having a first cable end connectable to a fixed base station, and a second cable end connectable to the work machine, wherein the cable tension sensor is provided on the cable.

3. The cable reel apparatus of claim 1, wherein the reel body is rotatably mounted upon a reel support and the cable tension sensor is provided on the reel support.

4. The cable reel apparatus of any preceding claim, wherein the reel drive comprises an electric motor.

5. A work machine comprising a cable reel apparatus according to any preceding claim.

6. A method of controlling a cable reel apparatus comprising a rotatable reel body configured to carry a length of cable, and a reel drive configured to rotate the reel body in clockwise and anti-clockwise directions; the method comprising:monitoring signals from (i) a reel speed sensor configured to measure a rotational speed of the reel body, and (ii) a cable tension sensor configured to measure a tension of a cable carried on the reel body;determining if the cable tension is within a predetermined range; and if the cable tension is not within the predetermined range:calculating a desired reel speed that will bring the cable tension within the predetermined range; andinstructing the reel drive to adjust to the desired reel speed.

7. The method of claim 6, wherein a length of cable is carried upon the reel body, the cable configured to supply power and / or data to the work machine, and having a first cable end connectable to a fixed base station, and a second cable end connectable to the work machine, and wherein the step of monitoring signals from the cable tension sensor comprises monitoring signals from a cable tension sensor which is provided on the cable.

8. The method of claim 6, wherein the reel body is rotatably mounted upon a reel support and the step of monitoring signals from the cable tension sensor comprises monitoring signals from a cable tension sensor which is provided provided on the reel support.

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