GB2122712A - Method and apparatus for axially feeding a flexible shaft along a pipe with simultaneous rotation of the shaft - Google Patents

Abstract

A method and apparatus for advancing a flexible shaft along an axis with simultaneous rotation of the shaft about the axis comprises a drum 1 mounted for rotation about its axis and containing the flexible shaft 7, preferably a helically wire wound flexible drive shaft, coiled therein and projecting from the outlet 5. Externally the shaft 7 is engaged by a member 9 which serves to draw the shaft from the drum and to advance it axially as the drum rotates. In the preferred arrangement, using a helical wire wound flexible shaft, the member 9 is a stationary member which engages the helically wound outermost layer of the wire wound shaft which acts as its own worm or continuous screw to draw the shaft from the drum as the drum rotates. The apparatus may be used for a descaling, deburring or grinding the inside of tubes or pipes by advancing a rotary grinding wheel 8 therethrough, or for clearing blocked drains etc. by advancement of an auger along the drain. <IMAGE>

Description

SPECIFICATION Method and apparatus for axially feeding a flexible shaft along a pipe with simultaneous rotation of the shaft This invention relates to a method and apparatus for advancing a flexible shaft along an axis with simultaneous rotation of the shaft about that axis. More particularly, but not exclusively, the invention relates to a method and apparatus for advancing a tool along a pipe or conduit with simultaneous rotation of the tool inside the pipe or conduit by means of a flexible drive shaft.

In many manufacturing and service operations there is a need to advance a tool, e.g. a grinding wheel or auger, along a pipe or conduit with simultaneous rotation of the tool inside the pipe.

For example, in the manufacture of pipes or lengths of welded pipeline it may be desired to advance a grinding wheel along the inside of the pipe or pipeline with simultaneous rotary movement in order to deburr the inside of the pipe or to remove excess weld material projecting into the pipeline at, for example, the junction of two lengths of pipeline that are welded together. In another application, it may be desired to descale boiler tubes, or even central heating conduit systems, by advancing a descaling tool along the boiler tube or central heating pipe with simultaneous rotational movement. Yet another application of this type involves clearing blocked drains by advancing a flexible drain-clearing rod along the drain with a simultaneous rotary motion of the rod, usually, but not necessarily using an auger fitted on the forwqrd end of the rod.Other applications of the method and apparatus of this invention will become apparent to the reader as the description proceeds.

Broadly speaking, the apparatus of this invention comprises a drum mounted for rotation about an axis and containing a length of flexible shafting coiled in the drum about said axis. One end of the shafting is fastened inside the drum, whilst the other, free end of the shafting projects from the drum along said axis of rotation. Means are provided for driving the drum about said axis, and for simultaneously withdrawing the flexible shafting from the drum along said axis as the drum rotates.

A variety of means may be used for withdrawing the shafting from the drum as the drum rotates. In one technique an axially movable clamping member may be used, which is clamped onto the shafting adjacent the drum and then moved in an axial direction away from the drum as the drum rotates, thereby to withdraw the shaft from the drum. In an alternative arrangement, on exiting from the drum the shafting may be fed through a nip formed between a pair of squeeze rolls or wheels one or both of which are positively driven to draw the shafting from the drum as the drum rotates.

In a preferred embodiment, however, the shafting used in this invention is a helically wound flexible drive shafting comprising a plurality of wires, usually in several layers, of alternating lay, helically wound to form a flexible shaft, and use is made of the helical lay of the outermost wire layer as a thread to draw the shafting out of the drum as the drum rotates. To this end a reaction member is mounted in a fixed position externally of the drum, said member frictionally engaging the surface of the shafting as it emerges from the drum so that as the shaft rotates about its axis, as a result of the rotation of the drum, the outer lay of wires forming the flexible shaft engage against the reaction member and act as continuous worm or thread to draw the shafting from the drum by frictional engagement with the reaction member.The reaction member need not, but can be internally threaded, provided that a reaction member is used having a resilient inner surface or surfaces which frictionally engage the helically wound surface layer of the shaft.

In all the embodiments described, the flexible shafting may be retracted into the drum after use simply by reversing the direction of rotation of the drum, and reversing the action of the withdrawing means to feed the shafting back into the drum. In the case of the preferred embodiment, however, simple reversal of the direction of rotation of the drum will act to retract the shaft, since the helically wound surface layer of the wire wound flexible shafting will act as its own continuous thread or worm to feed itself back into the drum, consequent upon the reversal of the direction of rotation.

The method and apparatus of the present invention will be further described with reference to and illustrated by the accompanying drawings, which illustrate, by way of example only, a particular application of the method and apparatus to the cleaning or descaling of boiler tubes. Other applications, some of which have already been mentioned, will be readily apparent to the reader.

In the drawings: Fig. 1 is a diagrammatic section through an apparatus embodying the principles of the present invention; Fig. 2 is an enlarged sectional view of the reaction member used in the embodiment of Fig. 1; Fig. 3 is an enlarged sectional view of an alternative form of reaction member; Fig. 4 is a diagrammatic illustration of the application of the apparatus and principles of this invention to the cleaning or descaling of a boiler tube; and Fig. 5 is a diagrammatic elevation of a modified form of wire wound flexible shaft that may be used in this invention.

Referring to the drawings, the apparatus of this invention comprises a hollow drum 1 mounted on a shaft 2 and rotatable about the axis of the shaft, for example, by a motor 3, see Fig. 4. Various drives may be used, for example a simple V-pulley and belt drive as in Fig. 4; however, the way in which the drum is driven is quite immaterial. Also it is immaterial whether the drum is mounted for rotation about a horizontal axis as in Fig. 1 or a vertical axis as in Fig. 4.

The drum is closed by a generally conical end closure member 4 having a tubular outlet sleeve 5 aligned on the axis of rotation of the drum.

Coiled inside the drum and fixed thereto at one end by means of a clamp 6 is a length of helically wound flexible drive shaft 7 of conventional construction comprising, for example, a plurality of wires helically wound around the axis of the shaft, usually in a plurality of layers, each layer having an opposite lay. The free end of the flexible shaft projects from the drum along the axis of rotation through the sleeve 5. Connected, or connectible to the free end of the drive shaft is a rotary tool 8, the nature of which depends on the purpose to be served. For example, for deburring or descaling the inside of pipes a grinding wheel may be attached, or for deblocking drainage or other tubes an auger may be attached.

Externally of the drum 1 the drive shaft is gripped by a reaction member 9. This may take a variety of forms, two of which are illustrated in detail in Figs. 2 and 3. In the arrangement shown in Figs. 1 and 2, the reaction member comprises two relatively movable jaws 9a, 9b which are biassed towards each other by a biassing means, not shown. The jaws thus resiliently grip the flexible shaft externally of the drum and engage the surface of the shaft between adjacent helically wound wire strands (see Fig. 2). In the embodiment of Fig. 3, the reaction member is in the form of a sleeve 10 having an internal helical groove complementary to and mating with the helically wound wire strands forming the surface layer of the flexible drive shaft.The internal groove or thread in the sleeve 10 may be preformed, or the sleeve may simply be a resiliently deformable member, e.g. of rubber, into which the wire strands of the drive shaft embed themselves to form their own thread. Whatever the construction, the reaction member will be held by suitable fixing means, not shown, to prevent rotation of the reaction member with the shaft.

Although the operation of the apparatus of this invention will be readily apparent from a reading of the description so far, this will now be explained with reference to Fig. 1.

Initially, substantially the whole length of the flexible shaft will be retracted into and coiled inside the drum, with only a short length projecting from the tubular outlet 5 of the drum to be engaged by the non-rotatable reaction member 9. As the drum is driven about its axis, the external strands of the flexible drive shaft act as a continuous worm or thread engaging against the reaction member to draw the shaft out of the drum and to advance the shaft lengthwise with simultaneous rotary motion. The rate of advancement depends, of course, upon the speed of rotation of the drum and the pitch of the helically wound wires which form the outer layer of the flexible drive shaft.Thus, depending on the purpose to be served, the tool 8 can be advanced along a pipe with simultaneous rotary motion to clean or descale the inside of the pipe, to deburr the inside of the pipe or otherwise remove obstructions and blockages. Since the shaft is flexible the tool can be readily advanced around bends in the pipe as well as along straight sections. To retract the shafting and recoil it in the drum, the direction of rotation of the drum is simply reversed.

An application of the method and apparatus of the present invention to the descaling or cleaning of boiler tubes is illustrated in Fig. 4, which also illustrates various modifications which can be practised in accordance with this invention.

Insofar as not already described, the apparatus of Fig. 4 comprises a housing 11, shown in outline, in which are mounted the drum 1 and the motor 3. Leading from the upper part of the housing is a fixed tubular casing 12, terminating in a flange which abuts the ends of the tube 13 to be descaled, for example, one of an array of tubes in a conventional tubular boiler construction 14. The outlet sleeve 5 from the drum 1 is rotationally received within the end of the casing 12 by a bearing 1 5. Adjacent the distal end of the tubular casing 12, or at any convenient position therealong is the reaction member 9, which, for example, can be a threaded sleeve as already described with reference to Fig. 3, and inserted into the casing so as to be non-rotatable therein.

Mounted on the end of the flexible shaft and advanceable thereby along the boiler tube is a rotary descaling tool 8. In a particular feature of this embodiment, the drive shaft 2 of the drum 1 is hollow and is in open communication with the interior of the drum. In this way a vacuum can be applied by an evacuating means, not shown, to extract scale or other debris removed from the boiler tube by the descaling tool 8 via the tubular casing 12. In an alternative arrangement, the casing 12 may be provided with a sideline by means of which the casing can be directly evacuated, rather than through the drum 1.

Various other modifications to the method and apparatus of this invention will be apparent to the reader. One such modification is shown in Fig. 5.

In this modification alternate strands in the outer layer of helically wound wires forming the flexible drive shaft are of a larger diameter than the others.

This provides a clearly defined and enhanced "thread" on the surface of the shaft. In an alternative arrangement every third or fourth strand could be enlarged, rather than every alternate strand.

In yet another modification, the reaction member 9 can be mounted for axial movement along a path parallel to the axis of the shaft, and if desired, can be used to axially puli the shaft from the drum as it rotates, or to return it to the drum after use. In another alternative, the shaft can be drawn axially from the drum by a pair of squeeze rollers or wheels gripping the shaft externally of the drum and one or both of which is positively driven to advance the shaft lengthwise about its axis.

Depending on the diameter and flexibility of the drive shaft, it may be desirable to provide a guide tube extending inwardly into the drum from the outlet 5 and freely rotatable with respect thereto, the guide tube serving to guide the flexible shaft 7 as it is drawn from the drum through the outlet 5.

This reduces the tendency of extremely flexible, small diameter shafts to form kinks as the shaft is withdrawn from the drum with resultant tangling of the shaft inside the drum.

These and other modifications are all to be included within the scope of the following claims.

Claims (11)

1. Apparatus for advancing a flexible shaft along an axis with simultaneous rotation of the shaft about that axis comprising a drum mounted for rotation about said axis, a length of flexible shaft coiled in said drum about said axis, said shaft being fastened in said drum at one end and having a free end projecting from the drum along said axis, means for driving the drum about said axis and means for simultaneously withdrawing the shaft from the drum along said axis as the drum rotates.

2. Apparatus according to claim 1 wherein said flexible shaft is of the type comprising a plurality of wire strands helically wound and arranged in one or more layers about the axis of the shaft.

3. Apparatus according to claim 2, wherein said withdrawing means comprise a reaction member non-rotatably mounted externally of the drum and which engages the plurality of helically wound wires forming the surface layer of the shaft, such wires thus constituting a continuous thread or worm which causes the shaft to advance along said axis as the drum rotates by virtue of the engagement with the nonrotatable reaction member.

4. Apparatus according to claim 3, wherein the reaction member comprises a clamp having spring biassed jaws which resiliently engage the surface of the shaft externally of the drum, and which clamp is held against simultaneous rotation with said shaft.

5. Apparatus according to claim 3, wherein the reaction member comprises a sleeve axially mounted around the shaft externally of the drum and held against rotation with the shaft, said sleeve providing an internal thread cooperatively engaging with the worm or thread constituted by the helically wound wires forming the surface of the shaft.

6. Apparatus according to any one of the preceding claims, comprising a rotary tool detachably mounted on the exposed end of the flexible shaft.

7. A method of advancing a length of flexible shaft along an axis with simultaneous rotation of the shaft about said axis, which comprises continuously withdrawing said shaft axially from a drum mounted for rotation about said axis and containing the said shaft coiled therein, and simultaneously rotating said drum.

8. A method according to claim 7, wherein the flexible drive shaft is of a type comprising a plurality of wire strands helically wound in one or more layers about the axis of the shaft, and wherein the shaft is continuously withdrawn from said drum and advanced along said axis by virtue of engagement of the helically wound wire strands forming the surface layer of the shaft with a reaction membernonrotatably mounted externally of the drum and which cooperatively engages with the continuous worm or thread provided on the surface of the shaft by the wire strands constituting said surface layer.

9. A method according to claim 7 or 8 as applied to the advancement of a rotary tool along the inside of a pipe or tube, said tool being mounted on the forward end of said shaft as it is advanced along the pipe or tube.

10. A method according to claim 9 as applied to the grinding, deburring or descaling of the internal wall of a pipe or tube, and wherein said rotary tool is a grinding wheel or disc.

11. A method according to claim 9, as applied to clearing a blocked pipe or tube, and wherein said rotary tool is an auger.