The present invention relates to apparatus for use in replacing or renewing drain pipes or service ducts, and to a method of renewing or replacing drain pipes or service ducts employing the apparatus.

In urban environments it is usual practice to install services underground in ducts in order not to leave these exposed to the environment and/or to create potential risks of damage and/or pollution from their exposure. Likewise drainage services are installed underground. This practice leads to certain disadvantages when changes are required, for example to the routing of the service ducts and/or due to damage or decay of the materials from which the drain pipes or service ducts are made. In addition, drain pipes may become obstructed due to the build up of solids within the pipe due to natural accretion or the presence of a projecting aggregation point, which may, for example, be tree root growing through a crack or may be an imperfection on the lining of the pipe. Likewise, increases in traffic density in recent years can result in fracture of underground pipes due to the increased loadings which far exceed those envisaged in the past when the drain pipes were installed.

Various different types of materials have been used for drain pipes, including pitch fibre which appear to have a relatively short life, and pipes of these materials installed even only thirty years ago are failing and require reinstatement in some way. Traditional techniques for reinstatement comprise excavation of the line of the pipe for removal of the damaged or broken pipe and replacement with a fresh one. Where drain pipes have been laid under buildings this is, plainly, an extremely troublesome operation, and even in exposed locations the cost of excavation and reinstatement of such drains is very high.

Some techniques for re-lining existing pipes and/or re-shaping pitch fibre pipes which have simply become deformed by the ground pressure, have been devised by the same inventor, and in this respect reference is made to British patents 2351334, 2350630 and 2369172 each of which presents a different solution to the problem of the considerable expense of excavation work.

The present invention seeks to provide an alternative technique by which underground passages and drains may be lined or re-lined for renewal or replacement, regardless of the nature of the material from which the original pipeline was made, and utilising newly devised techniques which simplify and economise on the operation.

According to one aspect of the present invention, therefore, a cutter and/or reamer device for use in renewing or replacing drainage pipes or service ducts is provided. This is adapted to be introduced into the pipe or duct to be renewed or replaced and

advanced forward through it. The cutter and/or reamer is characterised in that there are provided means for applying a transverse force to the pipe or duct through which the device is moving as it is thrust forward through it upon application of a longitudinal thrust force between two relatively movable members whereby to fracture and/or to enlarge the diameter of the pipe or duct in preparation for the introduction of a lining or replacement pipe or duct.

Enlargement without fracture may occur, for example, when the apparatus is applied for re-rounding pitch fibre pipes, that is pipes made from a variety of fibres bound by a mixture of pitch or tar. The fibrous material may well be one which it is undesirable to bring to the surface by trenching and replacement.

La the case of rigid clay pipes the forces applied from within the pipe may be sufficient to fracture it entirely allowing diametral enlargement to take place so that a fresh pipe section can be introduced in its place, leaving the fractured, replaced pipe surrounding the new one, and making use of the cylindrical cavity previously occupied by the old pipe or duct thereby avoiding the necessity for creating a fresh void for its presence.

The means for applying a transverse force preferably comprise elements which are urged radially outwardly from a rest position upon application of a longitudinal thrust force between two axially relatively movable parts of the device. It is preferred that the elements are withdrawn to a collapsed position upon application to the device of a tension force between the said two relatively movable parts in

the opposite directional sense from the thrust force which causes radial outward displacement of the elements.

In a preferred embodiment of the invention the said elements are carried on a holder which is axially displaceable with respect to a main body of the device, the holder and the body comprising the two relatively movable parts referred to above. The main body is preferably adapted to receive a thrust force which causes the device to advance forward in use. Alternatively, or additionally, the said body may be adapted to be advanced forward in use by a traction force applied to it in use by a tension member.

Thus, in use of the device, the operator may have the option of drawing the device through a pipeline utilising a line or chain, or of thrusting the device through the pipeline from behind. Of course in certain circumstances the application of force by both techniques may be appropriate.

In a preferred embodiment of the invention the said elements are elongate arms pivotally mounted to a part of the device, this part preferably comprising the above-mentioned holder.

If the said elongate arms are pivotally mounted at or adjacent one end thereof to the said holder it is advantageous for the lateral forces acting on the arms to be exerted at an intermediate point thereof as will be described in more detail herein below.

The arms may simply be provided with pads or elements for pressing against the inside of a pipeline as the device is thrust through it, which is of particular utility in connection with pitch fibre drains where it is required simply to re-shape them after deformation upon the application of excess loads, but in an alternative configuration the elements may carry cutter members adapted to engage the interior surface of a pipe or service duct in use thereof and to exert a specific cutting action thereon. This is of particular value in connection with clay drains where the cutter members may be cutter wheels adapted in use to roll along and cut into the interior surface of a pipe or service duct as the device is caused to advance along the said pipe or service duct. Li this way the wheels act to score the inner surface of the duct and to provide a fracture line which weakens the wall of the pipe or duct allowing it more easily to be fractured by the subsequent application of force by a radially outer part of the element.

In order to apply the lateral forces to the arm or arms the said body may have a tapered portion and the holder may be positioned in such a way as to be displaceable longitudinally of the body between a first position in which it is spaced from the said tapered portion and a second position in which it is proximal to the tapered portion. Adjacent the tapered portion then may further be a parallel- sided portion such that, after the initial application of a force to cause radial outward movement of the free ends of the arms, the components of the arms which effectively act as cam followers on the tapered portion are locked in the radially outermost position.

For this purpose the said first position of the holder in relation to the body is preferably forward of the second position thereof with respect to the longitudinal direction of advance of the device in use thereof. The second position is, consequently, rearward of the first position.

The said elements may have or carry cam follower portions or members by which they are urged laterally away from the said rest or collapsed position upon application of a longitudinal force tending to advance the device within a pipe or service duct to be replaced or renewed.

Such cam follower members may engage and, in use, move over the said tapered portion of the body.

The said arms may have parts of enlarged surface area at or adjacent their free ends, that is the ends remote from the pivotal connection to the holder, such enlarged parts acting frictionally to engage the inner surface of a pipe or service duct in use of the device as it is advanced through the said pipe or service duct whereby to cause relative longitudinal displacement of the said holder and the said body between the first and second positions of the holder with respect to the body.

The said elements may be located in positions spaced circumferentially around the body and may move radially between the rest or collapsed position and a working position. Preferably, the said elements are elongate arms pivotally connected to

the said holder at respective forward ends thereof, and adjacent arms in the circumferential array are of different lengths to allow the said parts of enlarged surface area to lie alongside one another. In the preferred embodiment of the invention the said parts of enlarged surface area comprise circumferentially extending lateral arms forming a T-shape with the said longitudinal arms. Such T- shape transverse arms effectively act as contact pads.

In the preferred embodiment of the invention the body is adapted to be engaged by a push rod, for which purpose it has push rod engagement means at one end thereof, such push rod engagement means comprising a screw threaded opening in one end thereof by which longitudinal thrust may be applied to the body by a push rod engaged therein. Alternatively, of course, the engagement means may be in the form of some other engagement arrangement, such as a threaded spigot to receive a threaded bore in the end of a push rod, a bayonet coupling or other connector arrangement.

In use of the apparatus the device is urged forwardly through the interior of a pipe by a push rod and, when the full length of the push rod has entered the pipe, a fresh push rod is connected to its end and further thrust applied to the second push rod, and so on building up a chain of push rods within the pipe or service duct being replaced. In order to keep each push rod centrally located within the pipe and avoid development of a catenary each push rod is preferably provided with a centralising guide which conveniently may be located at one end thereof.

The present invention may also be considered to comprehend apparatus for use in renewing or replacing a drainage pipe or service duct, comprising a cutter or reamer device as defined hereinabove, at least one push rod engageable with the device for bi-directional transport thereof, and actuator means engageable with the push rod and operable selectively to apply thereto longitudinal thrust in one of two opposite directional senses.

Preferably such actuator means is a double-acting fluid pressure actuator although other force-application means may be employed, including electromagnetic actuators, and pneumatic actuators (providing they can be made of sufficient capacity).

The actuator means may be carried on a frame adapted to locate it in position within a pit or other excavation in alignment with a drainage pipe or service duct to be replaced or renewed.

Such actuator locating frame may include means for applying pressure to two opposite walls of a pit whereby to secure the frame in position therein. This may be displaceable between a deployed position and a withdrawn position in which latter position it does not obstruct the opening to the pit whereby to allow insertion or removal of one or more push rod.

According to another aspect of the present invention there is provided a method of renewing or replacing drainage pipes or service ducts in which the said pipe or

service duct is enlarged and/or fractured by driving an enlargement tool through its interior, and a replacement pipe or pipe liner is thrust through the interior of the pipe or duct being renewed or replaced, substantially simultaneously with or immediately after enlargement of the diameter of the pipe or duct being renewed or replaced (or fractions thereof).

For this purpose one or more pipe sections to be introduced into the pipe may be located around the push rod closely adjacent the rear of the cutter or reamer tool which may, therefore, have a suitable flange or guide to protect the leading end of the pipe section as it is advanced into the interior of the pipe or duct being renewed or replaced.

The method of the invention may be stated as a method of renewing or replacing underground pipes or service ducts, comprising the steps of; i) locating the line of the pipe or service duct; ii) excavating at least two access pits along the line of the pipe or service duct to expose portions thereof (if it is not possible to gain access via existing access pits or manholes); iii) inserting a combined clearing and reaming tool into an opening at one end of the thus-exposed pipe or service duct; iv) fitting a replacement pipe or duct liner section to the said combined clearing and reaming tool; v) either before or after step iv) engaging a push rod into the said pipe or duct liner section;

vi) engaging one end of the push rod to the said combined clearing and reaming tool; vii) engaging the other end of the push rod to a linear actuator device and extending the actuator to thrust the tool, the pipe or duct liner section and the push rod axially along the pipe or service duct being renewed or replaced; viii) disengaging the linear actuated device and returning it to its original position; ix) engaging a further pipe or duct section into the previously-introduced section and a further push rod to the previously-introduced push rod; x) repeating steps v) to ix) until the required number of pipe sections have been introduced; xi) applying a tension to the push rod attached to the actuator whereby to cause the cutter and reamer tool to collapse radially and allow it to be withdrawn into the first pipe section; xii) successively withdrawing and removing the elements of the push rod string until the cutter and reamer tool is fully withdrawn and removed.

The method of the invention also comprehends a variation in which the steps x), xi) and xii) are replaced by: xa) repeating steps v) to ix) until the cutter and reamer tool becomes accessible from the second said pit, manhole or access opening; xia) disconnecting the cutter and reamer tool from the leading push rod; xiia) successively withdrawing and removing the elements of the push rod string through the said second pit, manhole or access opening.

It is to be noted that in pipes fitted with a so-called 'Buchan' trap or a silt trap or running trap the cutter and reamer tool can be driven through the side of the pipe at the bend, to be followed by a straight length of pipe being introduced.

If a trap in the new pipeline is required this can be installed in the pit or other access opening through which the new pipe sections are being introduced.

Various embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which;

Figure 1 is a perspective general view of the various components of the apparatus of the invention shown in dismantled condition at the rim of an access opening; Figure 2 is a perspective view of a cutter or reamer tool suitable for use with and forming part of and one aspect of the present invention shown in its collapsed condition; and

Figure 3 is a perspective view of the tool of Figure 2, showing it in its extended position;

Referring now to Figure 1, the apparatus of the invention comprises five main components, namely a cutter/reamer tool generally indicated 11, a set of push rods

12 (individually identified with subscript letters), an actuator or ram 13, a locating frame 14 and a pressure source 15.

Dealing with each of these items in turn, the cutter/reamer tool 11 is shown in more detail in Figures 2 and 3, and comprises a main body generally indicated 20 and a holder 21 carrying a set of arms generally indicated 22.

As can be seen clearly in Figures 2 and 3, the body 20 is a fabricated unit comprising a central stem 23 at the leading end of which is a generally cup-shape shroud 24 having a closed bottom at the leading end which is secured to the end of the stem 23 and provided with a generally triangular draw coupling 26 having an aperture 27.

As will be seen from a comparison of Figures 2 and 3, the rearward part of the body 20 (that part on the right hand side of the drawings) tapers outwardly towards the rear from the central stem 23 to a cylindrical terminal portion 29. The tapered portion 28 has a wide rearward end 30 the diameter of which is slightly greater than the cylindrical portion 29.

At the rearward end of the cylindrical portion 29 is a tapered centralising guide the function of which will be described in more detail below.

The set 22 of arms carried on the holder 21 is slidable on the stem 23 between an advanced position as shown in Figure 2 in which the holder 21 is almost entirely housed within the cup-shape shroud 24, and a rearward position in which the holder 21 is close to the narrow leading end of the tapered portion 28.

The holder 21 has a plurality of radial slots 32 each of which pivotally engages the leading end of a respective arm of the set 22, each arm being generally indicated 33. There are six such arms 33 in a circumferential array, alternate arms being relatively long (identified as 33L) or relatively short (identified as 33S). The long arms 33L each have respective transverse generally T-shape engagement portions 34L adjacent their free or tail ends, which are arcuately curved to match the circumferential or peripheral curvature of the shroud 24 and the centralising guide 31. A tail portion 35L of each longer arm has a rearwardly tapering shape with an inwardly inclined terminal surface 36L. The radially inner edge 37L of each long arm 33L slides on the tapering surface 28 of the body as the holder 21 and the mobile assembly 22 as a whole moves between the collapsed or forward position illustrated in Figure 2 and the extended or working position illustrated in Figure 3.

Between each adjacent pair of longer arms 33L is a respective shorter arm 33S. Each shorter arm 33 S is pivotally connected at its leading end to the holder 21 in the same way as the longer arms 33L, but a central portion of the shorter arms 33S is formed as two parallel plates with an elongate slot 38S between them, the slot 38S housing a freely pivoted cutter wheel 39S having a bevelled and hardened cutting edge 4OS.

Like the longer arms 33L the shorter arms 33S have transverse T-shape portions 41S adjacent their trailing ends, and corresponding inclined tail portions 42S

which, like the tail portions 35L of the longer arms 33L have a rearwardly tapering inclined surface 43 S.

A push rod 12 is shown engaged in the centralising guide 31 in Figures 2 and 3.

As will be appreciated, in use of the tool described in relation to Figures 2 and 3, it is intended that this should be placed into the entrance of a pipe to be renewed with the holder 21 moved forwardly into the shroud 24 and the arms 33 located in their collapsed position as illustrated in Figure 2. It is assumed, and would be normal, that the end of the pipe or service duct being replaced is exposed in a pit, excavated for the purpose, or a manhole or recess opening previously provided for example for maintenance or inspection purposes. A push rod 12 is screwed into the end of the body and a pipe section (not shown) to be introduced is placed over the push rod 12. The actuator 13 is then engaged with the end of the push rod 12 which has a guide flange 50 for this purpose, which is engaged by an enlarged mushroom head 51 (see Figure 1) of the actuator 13. For this purpose the actuator 13 is located in the lower part of the pit, manhole or access opening with the frame 14 against the back wall (that is the wall opposite that through which the pipe or service duct is exposed) and a bracing arm 52 (see Figure 1) the length of which is adjustable for the purpose, is placed spanning the open part of the pit, manhole or access opening to brace the actuator 13 in position. Thrust is then exerted by extending the actuator 13 to drive the tool and the new pipe section into the pipe to be renewed. As the arms 33 come into contact with the inner cylindrical wall of the pipe being renewed they are urged rearwardly in relation to the body 20 and, by

virtue of the engagement of the radially inner parts of the arms 33 with the inclined surfaces of the tapered portion 28 the arms are urged radially outwardly turning about the pivotal connection at their leading ends with the holder 21.

This brings the transverse T-shape friction elements 34L and 41 S into contact with the interior surface of the pipe increasing the frictional engagement and further encouraging relative displacement of the movable part of the tool with respect to the body 20 until maximum displacement has been reached as shown in Figure 3. As the tool is advanced into the pipe the cutter wheels 39S score its interior surface and the pressure exerted by the arms and especially the friction elements 34L, 41 S force the fractured pipe radially outwardly to leave a space for the introduction of the new pipe section surrounding the push rod 12.

When the actuator has been fully extended it is disengaged from the trailing end of the push rod 12 by unscrewing and retracted. A new push rod 12 is then attached to it and to the previous push rod, a second pipe section is fitted over it, the actuator re-engaged and again advanced to thrust the assembly comprising the push rod 12 the pipe section and the cutter tool further along the pipe being replaced.

When a sufficient length of pipe has thus been treated tension is applied to the push rod 12 by retracting the actuator 13 without disengaging the actuator arm from the push rod to which it is attached. This causes the entire push rod string to draw the cutter tool rearwardly causing the body portion 20 to be displaced

rearwardly so allowing the shroud 24 to be pulled back over the holder 21. At the same time the arms 33 are forced to move back to their collapsed position. In doing so the tapered sections 35L of the tail ends of the arms 33 and the inclined surfaces 36L, 43 S facilitate introduction of the tool into the leading end of the forwardmost pipe section. The entire tool can then be withdrawn back through the pipe which has just been introduced, until it is extracted from the last-introduced pipe section.

As an alternative, if the tool has been advanced into a next adjacent access pit, it is also possible to remove it from the leading push rod and remove it and the push rod string by withdrawing them through this access pit.