AU2011202892B2 - Depth Encoder for Hoist Cable - Google Patents

Abstract

Abstract A tool 11 for measuring length of passing cable 12 is disclosed, which is intended to measure the length of cable deployed in a down hole, shaft or bore in mining applications. The tool 11 has a housing 13 supporting a friction wheel 43 for rotation with the passing cable 12. The friction wheel 43 has a sensor 55 attached to measure increments of rotation of said friction wheel. The housing 13 also supports an idler wheel 61 for rotation about an axis spaced from the axis of rotation of the friction wheel 43 and arranged to press the cable 12 against the friction wheel 43. The idler wheel 61 is carried on a mechanism 63 - 67 moveable from a first position in which the idler wheel 61 is urged toward the friction wheel 43 to press the cable 12 against the friction wheel 43, and a second position in which the idler wheel 61 is spaced away from the friction wheel 43 to allow insertion and removal of the cable 12 from the tool 11. |H FIGURE 1 C s C sGR2 it FIGURE 2

Description

P/00/011 28/5/91 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Name of Applicant: Wireline Engineering Pty Ltd Actual Inventor(s): Jian Huang Jason Roche Address for service is: GoIja Haines & Friend 35 Wickham Street East Perth Western Australia 6004 Attorney Code: IJ Invention Title: Depth Encoder for Hoist Cable The following statement is a full description of this invention, including the best method of performing it known to me: 1 "DEPTH ENCODER FOR HOIST CABLE" Field of the Invention This invention relates to measuring distance and velocity and in particular to a device for measuring the length of cable played out in a hoist application. 5 Background Art The following discussion of the background art is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge as at the priority date of the 10 application. In hoist applications where an object is being lowered, it is important to have an understanding of the length of cable that has been paid out, and therefore the depth that the cable or an object attached to the cable has reached. Other parameters such as the rate of descent or ascent can also be important, depending on what is 15 being measured where the object attached at the end or along the cable is a sensor of some sort. This invention seeks to provide a tool for measuring length of cable paid out from a spool, such as on a hoist. A typical application for the tool of the invention will be measuring the length of cable being lowered down a borehole or downhole in mineral 20 exploration. Throughout the specification unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. 25 Throughout the specification unless the context requires otherwise, the word "include" or variations such as "includes" or "including", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. 2 Disclosure of the Invention In accordance with one aspect of the invention there is provided a tool for measuring the axial length of a cable passing longitudinally therethrough, said tool comprising a housing supporting a friction wheel for rotation about an axis normal to the axial 5 length of the cable, arranged with part of its circumference to contact and roll with the cable as the cable passes along, said friction wheel having a sensor attached thereto to measure increments of rotation of said friction wheel; said housing supporting an idler wheel for rotation about a second axis spaced from said axis; the cable in use being located between said friction wheel and said idler wheel; said idler wheel being 10 carried on a mechanism moveable from a first position in which said idler wheel is urged toward said friction wheel in order to press the cable against said friction wheel, and a second position in which said idler wheel is spaced away from said friction wheel to allow insertion and removal of the cable from said tool; said friction wheel having a friction surface to minimise slippage relative to said cable, in said first 15 position; said tool being characterised by said friction wheel and said idler wheel being the sole moveable components contacting and guiding the cable. The arrangement of the friction wheel and the idler wheel obviates the need to provide fore and aft guiding pulleys for the cable. This results in the tool being compact and light weight. 20 Preferably said idler wheel is provided with means to retain the cable to run along part of the circumference of the friction wheel, when said mechanism is in said first position. The means to retain the cable can be any arrangement to prevent the cable slipping off the friction wheel and may be selected from the idler wheel having a concave circumferential surface that causes the cable to track toward the narrowest 25 radial extent of the idler wheel, or the idler wheel having a flat or concave circumferential surface and the idler wheel having a pair of radially extending flanges along either edge thereof defining a path between the flanges to enclose the cable against the friction wheel when the mechanism is in the first position. Preferably said idler wheel has a concave surface around its circumferential extent to 30 maintain circumferential alignment of the cable. The concave surface has a minimum radius of preferably from 20 mm up to 150 mm, or from about half the diameter of the idler wheel to about three times the diameter of the idler wheel. Preferably the minimum radius is from 40 mm to 100 mm, or from 60 mm to 80 mm. 3 Alternatively said idler wheel has a flat surface around its circumferential extent, extending between opposed radial flanges. The radial flanges define a path within which the cable may run. The flat surface of the idler wheel has a radius of preferably from 20 mm up to 150 5 mm, or from about half the diameter of the idler wheel to about three times the diameter of the idler wheel. Preferably the radius is from 40 mm to 100 mm, or from 60 mm to 80 mm. Preferably the friction wheel is received between said opposed radial flanges and the path width of the idler wheel is commensurate with or slightly wider than the width of 10 the friction wheel, but not sufficiently wider than the width of the friction wheel to avoid the cable slipping between a side wall of the friction wheel and a radial flange of the idler wheel. However, where small diameter cables are in use, it is preferred that the path width of the idler wheel is less than the width of the friction wheel, in order to avoid the cable slipping between a side wall of the friction wheel and a radial 15 flange of the idler wheel. With this arrangement, the flange height must be less that the diameter of the cable. Preferably said housing encloses said friction wheel and said idler wheel and an opening is provided in said housing to allow insertion and removal of said tool from said cable. 20 Preferably said friction wheel is provided with a circumferential surface having enhanced friction properties, to avoid slippage of the cable when in said first position. Preferably said circumferential surface has a tungsten carbide coating. Preferably said idler wheel is urged toward said friction wheel and presses against said friction wheel with a weight of between 5 kg and 15 kg. 25 Brief Description of the Drawings Three preferred embodiments of the invention will now be described with reference to the drawings, in which: Figure 1 is a front plan elevation of a cable measuring tool according to the first embodiment; 30 Figure 2 is a rear plan elevation of the cable measuring tool according to the first embodiment; 4 Figure 3 is a top plan elevation of the cable measuring tool according to the first embodiment; Figure 4 is a bottom plan elevation of the cable measuring tool according to the first embodiment; 5 Figure 5 is a left hand end elevation of the cable measuring tool according to the first embodiment; Figure 6 is a right hand end elevation of the cable measuring tool according to the first embodiment; Figure 7 is a cut away rear plan elevation of the cable measuring tool 10 according to the first embodiment; Figure 8 is another cut away rear plan elevation of the cable measuring tool according to the first embodiment; Figure 9 is a cut away front plan elevation of the cable measuring tool according to the first embodiment; 15 Figure 10 is another cut away front plan elevation of the cable measuring tool according to the first embodiment; Figure 11 is a vertical cross section view from the left, through section A-A (in figure 7), of the cable measuring tool according to the first embodiment; Figure 12 is a vertical cross section view from the left, through section B-B (in 20 figure 7), of the cable measuring tool according to the first embodiment; Figure 13 is an exploded view featuring a cut away front plan elevation of the cable measuring tool according to the first embodiment, and associated mounting componentry for mounting to down hole pipe casing; Figure 14 is a top plan elevation of the cable measuring tool according to the 25 first embodiment and associated mounting componentry for mounting to down hole pipe casing; Figure 15 is a top plan elevation of the associated mounting componentry for mounting to down hole pipe casing, with the cable measuring tool removed; Figure 16 is a cross-section top plan elevation showing part of the cable 30 measuring tool according to the second embodiment; and Figure 17 is a cross-section top plan elevation showing part of the cable measuring tool according to the third embodiment. 5 Best Mode(s) for Carrying Out the Invention Both embodiments are a cable length measuring tool 11 for measuring the length of cable 12 paid out from a hoist, and has particular application in mineral exploration where sensors are lowered by hoist into down-holes, for gathering data relating to the 5 hole that has been drilled. In practice a down-hole will have its upper region where the ground can be friable, encased with a pipe, to maintain the integrity of the drilled hole, and prevent material falling into it. The cable length measuring tool 11 of the embodiments has an intended application where hoists which are normally used to lower equipment into a 10 down hole, do not include associated measuring equipment for making depth measurements. The cable length measuring tool 11 which is illustrated generally in the drawings, has a housing 13 which comprises a front panel 15, a top panel 17, a bottom panel 19, and a rear panel 21 formed of two portions 23 and 25 providing a gap 27 in the rear 15 panel. The top panel 17 has a cut-away recess 29 extending to meet the gap 27, and the bottom panel 19 has a cut-away recess 31 extending to meet the gap 27. The gap 27, cut-away recess 29 and cut-away recess 31 provide access for receiving and locating the cable 12, when the tool 11 is mounted onto a down-hole pipe. The housing 13 is manufactured from 3 mm stainless steel plate, to provide corrosion 20 resistance and structural rigidity. It will be understood that in an alternative embodiment, the housing could be manufactured from 5mm or 6mm thick aluminium plate or angle or channel section. The housing 13 is open at the left hand and right hand ends, as shown in figures 5 and 6, allowing internal componentry of the tool 11 to be visible, although covers 25 could be provided for the ends, if required. Referring to figure 4, the bottom panel 19 is provided with a circular aperture 33 which leads to the interior of a portion of pipe 35 which is welded onto the inside of the bottom panel 19. The circular aperture 33 and portion of pipe 35 provide a mounting point for a post 37 (see figure 13) of mounting equipment 39 to mount the 30 tool 11 onto a down-hole pipe 41, as will be described later. Extending between the front panel 15 and portion 23 of the rear panel 21 is a friction wheel 43 and axle assembly 45, which is machined from a single piece of stainless steel stock. This is best seen in figures 6 and 11. The circumferential extent 47 of 6 the friction wheel 43 is provided with a tungsten carbide coating to provide a gripping surface to prevent slippage of the cable 12, the paid-out length of which is to be measured. The friction wheel 43 has a diameter of 58 mm, and a width of 28 mm. The axle 45 is supported on ball bearing assemblies 49 on a hub assembly 51 5 mounted to portion 23 of the rear panel 21, and a hub assembly 53 mounted to the front panel 15. The axle 45 extends through the hub assembly 53 to rotatably connect with an incremental encoder 55 which is housed within a protective aluminium pipe 57. The hub assemblies 51 and 53 are bolted to the respective portion 23 and front panel 15 by screws 59 which are received in mating threaded 10 holes formed in the portion 23 and front panel 15. Referring to figure 12, an idler wheel (or pressure wheel) 61 is supported on a mechanism having a shaft 63 on a pair of ball bearing assemblies 65. The shaft is secured to the end of a lever 67 which is secured at its other end to a spring loaded post 69 (both the lever 67 and the springloaded post also forming part of the 15 mechanism), which rotatably urges the lever 67 to force the idler wheel 61 towards the friction wheel 43, in a first position of the mechanism. The spring loaded post 69 is mounted to portion 25 of the rear panel 21, and bolted in place. Without cable present between the idler wheel 61 and the friction wheel 43, the idler wheel 61 will contact the friction wheel 43, and a force applied by the idler wheel 61 is equivalent to 20 a weight bearing on the friction wheel 43 of about 8 kg. This equates to a force of about 78 Newtons. With the cable in place, this weight is from 10 kg to 15 kg, (98 N to 147 N) depending on the diameter of the cable. The idler wheel 61 has a concave circumferential surface 71, which assists in aligning the cable 12 when a cable 12 is inserted in the tool 11, and the mechanism is in the first position. The concave 25 circumferential surface has a radius of about 70 mm. Referring to figure 1, the mechanism also includes a rotatably actuable handle 73 which is mounted to the front panel 15. This handle 73 is connected to a square section shaft 75 which is connected to a cam 77. Rotation of the handle 73 causes the cam 77 to interfere with the edge of the lever 67, forcing the lever against the bias 30 force exerted by the spring loaded post 69, and forcing the mechanism from the first position to a second position in which the idler wheel 61 is displaced away from the friction wheel 43, as shown in figures 8 and 10, in which position a cable 12 can be inserted and removed from the tool 11. Figures 2, 3 and 4 show the mechanism in the first position, without a cable located 35 between the idler wheel 61 and the friction wheel 43. When the handle 73 is rotated 7 clockwise to move the mechanism the second position, the idler wheel 61 is moved away from the friction wheel 43, as shown in figures 8 and 10. The tool 11 can then be fitted to the mounting equipment 39. Before discussing this operation, the mounting equipment 39 shown in figure 13 to 15 will be described. 5 The mounting equipment 39 attaches to the down-hole pipe 41 and provides a platform on which the tool 11 is mounted. The mounting equipment 39 has a fixed v shaped jaw 79 to contact one side of the pipe 41, and a moveable v-shaped jaw 81 which slideably mounts on a pair of horizontal rails 83. A threaded shaft 85 with handle (not shown) is received at the back of the moveable v-shaped jaw 81, and 10 with the jaws 79 and 81 being offset below the horizontal rails 83, the jaws 79 and 81 secure to the pipe 41 in much the same manner as a G-clamp can secure objects together. Located above the rails 83 on a post 87 is a horizontal bar 89 which is slideably received in a portion of square section hollow tube 91, with a clamping fastener 93 to 15 set the horizontal position of the horizontal bar 89. The post 37 extends upwardly from the horizontal bar 89, and spaced from the post 37 is a portion 95 of pipe machined along one side to form a C-cross section, with a longitudinal opening wide enough to have a cable 12 pass through. The external diameter of the portion 95 of pipe matches the size and shape of the cut-away recess 31, particularly in alignment 20 with the idler wheel 61 and the friction wheel 43, and so the tool 11 can be located on the mounting equipment 39, in correct alignment by registration of the portion 95 of pipe and the post 37, respectively with the cut-away recess 31 and the circular aperture 33 and portion of pipe 35. With the jaws 79 and 81 securing the mounting equipment 39 to the pipe 41, and the 25 down-hole cable 12 in position extending down the down-hole pipe 41, the horizontal bar 89 is slideably positioned in the portion of square section hollow tube 91 so that the cable 12 passes through the interior of the portion 95 of pipe. The clamping fastener 93 is tightened, to set the horizontal position of the horizontal bar 89. With the mechanism the second position, the idler wheel 61 is moved away from the 30 friction wheel 43, as shown in figures 8 and 10. The tool 11 can then be fitted to the mounting equipment 39, by maneuvering the tool so that the cable 12 passes through the gap 27 in the rear panel 21 and the cut-away recesses 29 and 31. The tool 11 is then lowered with the cut-away recess 31 mating with the portion 95 of pipe and the circular aperture 33 and portion of pipe 35 mating with the post 37. The handle 73 is 35 then turned anticlockwise to move the mechanism into the first position as shown in 8 figures 7 and 9, so that the cable 12 is gripped by the idler wheel 61 and friction wheel 43. When the cable 12 is raised and lowered by the hoist, the friction wheel 43 and idler wheel 61 will rotate. The incremental encoder 55 outputs data to a PLC based processor which can determine in which direction and by how far the cable 12 5 has been moved. Important data provided to the user is distance, which is expected to be accurate to 0.1 m per 100 m or better, and rate of change (velocity), which is an important parameter for making accurate measurements down the hole. The PLC can be set to provide alarms if certain parameters are exceeded, and also to log cable movement for later review and analysis. 10 Referring to figure 16, a part of the cable measuring tool 11 according to the second embodiment is illustrated. For ease of understanding, like parts in the cable measuring tool 11 illustrated in figure 16 have the same numbering as in the cable measuring tool 11 according to the first embodiment. The orientation of the illustration in figure 16 is the same as in figure 3, but being a cross-section, parts like 15 the top panel 17 and handle 73 are not shown. The orientation of the illustration in figure 16 is a cross-section through section C-C in figures 1 and 2. The idler wheel 61 has a flat circumferential surface 97 defining a path for the cable 12 to run along, the path being bound along each opposite edge by a circumferential radially extending flange 99. The flat circumferential surface 97 has a radius of about 70 mm. 20 The flanges 99 assist in aligning the cable 12 with respect to the friction wheel 43 when a cable 12 is inserted in the tool 11, and the mechanism is in the first position, which is as shown in figure 16. The space between the inner surfaces 101 of the flanges 99 is commensurate with or slightly larger than the width of the friction wheel 43, but not so much larger that the cable 12 could slip between, when the mechanism 25 is in the first position. Referring to figure 17, a part of the cable measuring tool 11 according to the third embodiment is illustrated. For ease of understanding, like parts in the cable measuring tool 11 illustrated in figure 17 have the same numbering as in the cable measuring tool 11 according to the first and second embodiments. The orientation of 30 the illustration in figure 17 is the same as in figure 16, and as is the case with figure 16, parts in figure 3 such as the top panel 17 and handle 73 are not shown. The orientation of the illustration in figure 17 is a cross-section through section C-C in figures 1 and 2. As is the case with the second embodiment shown in figure 16, the idler wheel 61 has a flat circumferential surface 97 defining a path for the cable 12 to 35 run along, the path being bound along each opposite edge by a circumferential radially extending flange 99. The flat circumferential surface 97 has a radius of about 9 70 mm. The flanges 99 assist in aligning the cable 12 with respect to the friction wheel 43 when a cable 12 is inserted in the tool 11, and the mechanism is in the first position, which is as shown in figure 16. The space between the inner surfaces 101 of the flanges 99 is less than the width of the friction wheel 43. This arrangement has 5 been adopted in preference to that of the second embodiment, since it was found that with smaller diameter cables 12, there was a tendency with the arrangement of the second embodiment for the cable 12 to slip between the space between the inner surface 101 of a flange 99, and a wall of the friction wheel 43 when the mechanism is in the first position. For this reason the arrangement of the third embodiment is 10 considered to be the most preferred, even over the arrangement of the first embodiment, where cable disengagement problems have been experienced in situations where there was excessive misalignment of the cable leading to large sideways forces which could not be held in check by the concave circumferential surface of the idler wheel of the first embodiment. 15 The cable length measuring tool of the invention provides a simple and light weight solution to measuring the length of a cable paid down a shaft, to measure the length of cable being paid down the shaft. Not only does the invention have application in downholes as described in the embodiment, the invention could also have application in hoists, winders and elevators, and also in cranes used in the construction industry. 20 It will be appreciated in these different applications, changes will need to be made to adapt the housing to co-operate with different equipment. 10

Claims (14)

1. A tool for measuring the axial length of a cable passing longitudinally therethrough, said tool comprising a housing supporting a friction wheel for rotation about an axis normal to the axial length of the cable, arranged with its 5 circumference to contact and roll with the cable as the cable passes along, said friction wheel having a sensor attached thereto to measure increments of rotation of said friction wheel; said housing supporting an idler wheel for rotation about a second axis spaced from said axis; the cable in use being located between said friction wheel and said idler wheel; said idler wheel being carried 10 on a mechanism moveable from a first position in which said idler wheel is urged toward said friction wheel in order to press the cable against said friction wheel, and a second position in which said idler wheel is spaced away from said friction wheel to allow insertion and removal of the cable from said tool; said friction wheel having a friction surface to minimise slippage relative to said 15 cable, in said first position; said tool being characterised by said friction wheel and said idler wheel being the sole moveable components contacting and guiding the cable.

2. A tool as claimed in claim 1 wherein said friction wheel has a flat circumferential surface, and said idler wheel is provided with means to retain the cable to run 20 along part of the circumference of the friction wheel, when said mechanism is in said first position, said means to retain being selected from the idler wheel having a concave circumferential surface that causes the cable to track toward the narrowest radial extent of the idler wheel, or the idler wheel having a flat or concave circumferential surface and the idler wheel having a pair of radially 25 extending flanges along either edge thereof defining a path between the flanges to enclose the cable against the friction wheel when the mechanism is in the first position.

3. A tool as claimed in claim 2 wherein the means to retain the cable is provided by the idler wheel having a concave circumferential surface that causes the 30 cable to track toward the narrowest radial extent of the idler wheel when said mechanism is in said first position.

4. A tool as claimed in claim 2 wherein the means to retain the cable is provided by the idler wheel having a flat circumferential surface and the idler wheel having a pair of radially extending flanges along either edge thereof defining a 11 path between the flanges to enclose the cable against the friction wheel when the mechanism is in the first position.

5. A tool as claimed in claim 2 wherein the means to retain the cable is provided by the idler wheel having a concave circumferential surface and having a pair of 5 radially extending flanges along either edge thereof defining a path between the flanges to enclose the cable against the friction wheel when the mechanism is in the first position.

6. A tool as claimed in claim 3 wherein the concave circumferential surface has a minimum radius of from half the diameter of the idler wheel to three times the 10 diameter of the idler wheel.

7. A tool as claimed in claim 3 wherein the concave circumferential surface has a minimum radius of from 85% of the diameter of the idler wheel to 115% of the diameter of the idler wheel.

8. A tool as claimed in claim 4 wherein said idler wheel has a flat surface around 15 its circumferential extent, extending between opposed radial flanges, the opposed radial flanges define a path therebetween within which the cable may run.

9. A tool as claimed in claim 6 wherein the friction wheel is received between said opposed radial flanges and the path width of the idler wheel is commensurate 20 with or slightly wider than the width of the friction wheel, but not sufficiently wider than the width of the friction wheel to avoid the cable slipping between a side wall of the friction wheel and a radial flange of the idler wheel.

10. A tool as claimed in claim 6 wherein the path width of the idler wheel is less than the width of the friction wheel, in order to avoid the cable slipping between 25 a side wall of the friction wheel and a radial flange of the idler wheel.

11. A tool as claimed in any one of the preceding claims wherein said housing encloses said friction wheel and said idler wheel and an opening is provided in said housing to allow insertion and removal of said tool from said cable.

12. A tool as claimed in any one of the preceding claims wherein said friction wheel 30 is provided with a circumferential surface having enhanced friction properties, to avoid slippage of the cable when in said first position.

13. A tool as claimed in claim 12 wherein said circumferential surface has a tungsten carbide coating. 12

14. A tool as claimed in any one of the preceding claims wherein said idler wheel is urged toward said friction wheel and presses against said friction wheel with a weight of between 5 kg and 15 kg. 13