Background of the invention

[0001] The invention relates to a blade suitable for a device suitable for cutting a pipe, for example a liner installed inside a pipe, such as a sewage pipe, and an arrangement comprising said blade, as well as using them to cut a pipe from the inside of the pipe.

[0002] In the prior art solutions, the inner surfaces of sewage pipes have been machined from the inside of the pipe by means of grinding robots, for example. A robot may have a spherical blade attached at the end of an arm, which, as it is rotating, grinds the inner wall of the pipe, and which may be controlled by means of suitable control devices. A grinding cutter is used by a compressed-air motor, for example. Due to the low torque produced by the use of compressed air, the speed of rotation of the grinding cutter may be very high, such as 10 000 - 30 000 rpm. The robot is inserted inside the pipe to the cutting point by means of rigid push rods.

[0003] The problem with the prior art solutions is the slowness add susceptibility to errors of the machining. For example, a wrong control command issued to a robot may damage, in addition to the pipe being machined, also another pipe surrounding the pipe being machined, for example. In addition, a grinding robot is often difficult to drive to the desired spot inside the sewage pipe, possibly through a number of sharp corners. Passing corners is not always successful, so the grinding robot often has to be used from a different end of a pipe than the one where the lining was done, in which case a gully hole on a street may have to be opened and the street closed for traffic for the duration of machining.

Brief description of the invention

[0004] An object of the invention is thus to provide a device and an arrangement in such a manner that the aforementioned problems can be solved. The object of the invention is achieved by an arrangement and a device which are characterised by what is disclosed in the independent claims. The preferred embodiments of the invention are disclosed in the dependent claims.

[0005] The invention is based on the device having a spindle to which flexible protrusions or strips may be attached, which may be clamped against the spindle as the device is taken inside a pipe. When the spindle is rotated by a power drill through a cable, for example, the strips are pressed against the inner wall of the pipe. A blade is attached to the strips, so the blades of a device spinning at a particular spot of the pipe will machine material off the inner wall of the pipe and eventually cut the pipe.

[0006] The benefit of the method and arrangement of the invention is that the device can be pushed even in a curvy pipe for long distances to the desired cutting point and cut the pipe quickly and easily.

Brief description of the drawings

[0007] The invention is now described in closer detail in connection with the preferred embodiments and with reference to the accompanying drawings, in which:

[0008] Figure 1 shows a device according to an embodiment for cutting a pipe from the inside;

[0009] Figure 2 shows a device spindle according to an

embodiment;

[0010] Figure 3 is a cross-sectional view of a device according to an embodiment as seen from the direction of the spindle axis;

[0011] Figures 4a, 4b, and 4c show examples of support profiles according to certain embodiments;

[0012] Figure 5 shows a protrusion according to an embodiment of the invention;

[0013] Figure 6 shows a sliding surface according to ah

embodiment of the invention;

[0014] Figure 7 shows a blade according to an embodiment of the invention;

[0015] Figure 8 shows a protrusion according to an embodiment of the invention; and

[0016] Figures 9a and 9b show examples of adjustable blades according to certain embodiments.

Detailed description of the invention

[0017] Figure 1 shows a device 100 according to an embodiment. Figure 2 shows a spindle 110 of the device according to an embodiment, without protrusions attachable to it. The device comprises a spindle 110 to which a number of protrusions 120 are radially attached. The protrusions advantageously comprise a support profile 122 which is attachable to the spindle 110, and an elastic and/or flexible strip 121 attached to the support profile. The protrusions are preferably arranged on different sides of the spindle, symmetrically relative to its axis of revolution. One of the purposes of the protrusions is to position the spindle by, for example, centering it inside a pipe of a pipe assembly and to keep the longitudinal axis of the spindle 110 parallel to the longitudinal axis of the pipe. The protrusions 120 may be attached to grooves 113, for example, by means of fixing screws. A flexible cable 150 has been fixed to the spindle with fixing means 112, to the other end of which (not shown in the Figure) a device that rotates the machining device may be fixed, such as a motor rotating the machining device at a suitable speed. The fixing means 112 may be, for example, screws, bolts, rivets, or wedges, by means of which the cable 150 is fixed to the spindle 110 with the aid of openings 111. In a preferred embodiment, the rotation speed of the spindle may be, for example, 1 000 - 4 000 rpm.

[0018] In an embodiment, the protrusions 120 comprise rubber or other elastic material, which may be reinforced with Kevlar, fabric, or other textile or another reinforcement that improves the strength of the protrusion against, for example, tearing. In an embodiment, the protrusions are rubber strips that have fabric reinforcement inside. Because the elastically flexible, mutually similar protrusions are in this embodiment located symmetrically on different sides of the spindle, the protrusions together always center the spindle in the middle of the pipe that is being machined with the device.

[0019] The protrusions 120 comprise at least one blade 130 to machine material off the inner surface of the pipe to cut the pipe. When the spindle 110 is rotated, the protrusions 120 bend and the blades 130 in the vicinity of the outer edge of the protrusions hit the inner surface of the pipe. Preferably, there is one blade in each protrusion at essentially the same spot of the protrusion, whereby each blade will machine the same cutting trace inside the pipe, if the spindle is rotated in place in the pipe. In, an embodiment, a protrusion may have a plurality of blades, for example, two or three blades, or some of the protrusions may be bladeless in which case they just balance the device. As to its operating principle, the blade 130 may be cutting, abrasive, grinding, or sawing.

[0020] In an embodiment, a protrusion may comprise one or more sliding surfaces 124. The sliding surface is preferably elevated from the surface of the protrusion strip 121. The friction coefficient between the sliding surface 124 and the inner surface of the pipe is smaller than the friction coefficient between the strip and the inner surface of the pipe. If the protrusion comprises a rubber strip, the friction between the rubber strip and the inner surface of the pile may impede the rotation of the spindle or unnecessarily heat up the pipe and the rubber strip. In such events in particular, it is advantageous to use the sliding surface 124 which slides against the inner surface of the pipe and thus keeps the rubber strip off the inner surface of the pipe. The sliding surface 124 may be formed, for example, with a metal rivet which is fixed through the protrusion or strip and which is advantageously rounded on the side that is arranged to be in contact with the inner surface of the pipe.. Figure 6 shows a sliding surface according to an embodiment and its rivet-like structure by means of which the sliding surface 124 may be fixed to the strip 121. In an embodiment, the sliding surface is implemented with a pin or a bulge fixed to the strip. The sliding surface is preferably of metal, nylon, or Teflon. In an embodiment, the sliding surface is on the surface of the protrusion strip.

[0021] Figure 3 shows a cross section of a device according to an embodiment as seen from the direction of the axis of revolution of the spindle 110. The Figure clearly shows the strips 121 fixed to the spindle 110 with the support profiles 122. Figures 4a, 4b, and 4c show examples of alternative embodiments for the support profile of the grinding means. Figure 5 shows a protrusions 120 according to an embodiment, comprising an elongated support profile 122 and an elastic strip 121 attached to the support profile 122. Two sliding surfaces 124 and a blade 130 are attached to the strip 121. The support profile 121 comprises, in the embodiment show in Figure 4c, an upper portion 122a with a rectangular cross-section and having a slot extending downward from the top surface of the upper portion, and a lower portion 122b with a rectangular cross-section. There is a strip 121 fastened in the slot extending downwards from the upper surface of the upper portion 122a of the support profile 122, preferably with crimp connection by one of its edges. The cross section of the support profile 122 has a height direction hi and a width direction wl The greatest dimension of the cross-section of the lower portion 22b of the support profile 122 is, in the width direction w1 , greater than the corresponding dimension of the upper portion 122a. In this way, the support profile 122 engages with the groove 113 of the spindle 110 against radial and peripheral movement of the spindle 110 when the support profile 122 is pushed into the groove 113 from either of the end surfaces of the spindle 110. In an embodiment, the spindle 110 only has open grooves 113 at one end, whereby the grooves will not extend from end to end of the spindle 110, as shown by Figure 2. The spindle 110 end that has the open grooves 113 uses an end piece 115 which may be fastened by, for example, screws to threaded screw holes 115 at the end of the spindle 110. Advantageously, the threading in the screw holes 115 does not quite extend to the end of the spindle 110, whereby it is easier to place all the screws of the end piece 114 in the threads at the same time.

[0022] Figures 4a, 4b, and 4c show three alternative embodiments for the support profile. In all the embodiments shown in Figures 4a - 4c, the shape of the upper portion 22a of the support profile is a rectangle with a slot for the strip. The slot of Figures 4a and 4b have a toothing in the slot, which prevents the sliding of the strip off the slot after the crimp connection has been performed. In the embodiment shown in Figure 4a, the cross section of the lower portion 122b of the support profile 122 is trapezoidal, in Figure 4b circular, and in Figure 4c rectangular. In the embodiments of Figures 4a, 4b, and 4c, the greatest dimension of the cross-section of the lower portion 122 of the support profile 122 is, in the width direction w1 , greater than the corresponding dimension of the upper portion 122a. The cross-section of the support profile 122 may be anything, but it must have at least one portion the greatest dimension of which is, in the width direction w1 , greater than the corresponding dimension of the upper portion 122a above it, so that the support profile 122 can engage with the corresponding groove 113 in the spindle 110 against radial and peripheral movement of the spi dle 110.

[0023] Figure 5 shows a protrusion 120 according to an embodiment of the invention. The protrusion 120 comprises a support profile 122 and strip 121 , attached by a crimp connection to the slot in the support profile 122. In the strip 121 , two sliding surfaces 124 have been attached near the outmost corners, in relation to the support profile, and a blade 130 to the centre of the side of the opposite strip 121 , in relation to the support profile 122. By changing the specific weight, size, or mass of the strip 121 , the force at which the blade 130 presses against the inner surface of the pipe may be changed. In addition, the rotation speed of the spindle 1 0 affects the magnitude of the force in question. If a strip made of same the material and having a standard thickness is always used, the strip height extending away from the support profile 122 and the strip length in the direction of the support profile 122 allow the mass of the strip to be changed, whereby the blade 130 can be made to bite the inner surface of the pipe either more effectively, if the mass is increased, or more weakly, if the mass is decreased. The height of the strip cannot be increased very much, so that the strip 121 does not extend over the blade 130 in the adjacent strip and prevent the blade from machining the inner surface of the pipe as the device is rotating in the pipe. Instead, the length of the strip 121 may be increased as needed, whereby the flexibility of the strip needs to be taken into account and, if need be, more sliding surfaces added near the edge opposite the support profile 122 of the strip 121 so that the surface of the strip 121 would not hit the inner surface of the pipe being machined as the spindle is rotated and slow down the rotating motion.

[0024] Figure 7 shows a blade 130 according to an embodiment of the invention. The blade according to the invention comprises a cutting head 134 on a bottom plate 132 and a machining surface 135 on the cutting head. The cutting head 134 defines the cutting depth of the blade 130, and by changing the height of the cutting head 134 from the bottom plate 132, the cutting depth may be changed. As to its operating principle, the blade 130 may be cutting, abrasive, grinding, or sawing. The machining surface 135 of the cutting head 134 in the blade 130 may have a serrated, wedge-shaped, or roughened shape.

[0025] In an embodiment, the bottom plate 132 and the cutting head 134 are one and the same piece. In an embodiment, the bottom plate 132 and the cutting head 134 are welded to each other. In an embodiment, the bottom plate 132 has an opening through which the upper part of the cutting head 134 fits and the cutting head 134 has a bottom part which is wider and/or longer than the upper part and which does not fit through the opening in the bottom plate, whereby the bottom part of the cutting head 134 keeps the cutting end against the bottom plate 132 when the blade 130 is attached to the strip. By detaching the blade from the strip the cutting head 134 may be removed from the bottom plate 130 and the cutting head 134 replaced by a new one or one of a different model. The blade 130 may be fastened to the strip 121 by using a baseplate 131 on the other side of the strip, whereby the blade 130 may be fastened to the strip 121 by placing the strip 121 between the blade bottom plate 132 and the baseplate 131 and by joining, by means of openings 133, the baseplate 131 , strip 121 , and bottom plate 132 together by screws, bolts, nuts, or rivets, for example. In an embodiment, the strip 121 is reinforced in such a way that using a base plate 131 is not necessary, in which case the strip can be directly provided with fastening points corresponding to the openings 133 of the bottom plate 132, and the bottom plate 132 can be directly fastened to the strip 121 for instance with screws, bolts and nuts or rivets.

[0026] Figure 8 shows a protrusion 120 according to an embodiment, particularly suitable for grinding a pipe from the inside of the pipe. By using protrusions according to the embodiment in connection with the device, it is easy to use the device to grind off the inner pipe, such as a lining impregnated by resin, in a piping arrangement consisting of two pipes within each other, such as a metal pipe renovated with the lining technology. The protrusion 120 comprises a support profile 122 and strip 121 , attached by a crimp connection to the slot in the support profile 122. Four blades 130 are arranged in the strip 121 in a line on the opposite edge of the strip 121 in relation to the support profile 122. In an embodiment, from one to ten blades 130 are arranged, advantageously two, three, four, five or six blades, in one strip 121. In an embodiment, a plurality of cutting heads 134 are arranged in one bottom plate 132 of the blade 30, such as two, three, four or five cutting heads. In an embodiment, the protrusions 120 attachable to one spindle 110, such as four protrusions, each have the blades 130 or the cutting heads 134 of the blades arranged at slightly different positions in the strip 121. Advantageously, the blades 130 are arranged in the protrusions 120 in such a manner that as the spindle 10 is rotating the cutting heads 134 of the blade cover as large an area of the inner surface of the machined pipe as possible.

[0027] Figures 9a and 9b show examples of blades 130 according to some embodiments, which feature an adjustable cutting depth. The blade according to the embodiment of Figure 9a comprises a cutting head 134 on the bottom plate 132 and a machining surface 135 in the cutting head. The cutting head 134 defines the cutting depth of the blade 130, and by changing the height of the cutting head 134 from the bottom plate 132 the cutting depth may be changed. The height of the cutting head 134 from the bottom plate may be changed by moving the support 137 along a groove 136 arranged in the bottom plate. The support may be fixed in place by, for example, a screw arranged on the bottom surface of the bottom plate, this screw tightening the support 137 in place in the groove 136. One end of the cutting head is functionally, for example, hingedly, attached to the bottom plate and the other end or the cutting head is arranged to be movable. As to its operating principle, the blade 130 may be cutting, abrasive, grinding, or sawing. The machining surface 135 of the cutting head 134 in the blade 130 may have a serrated, wedge-shaped, or roughened shape.

[0028] The blade according to the embodiment of Figure 9b comprises a cutting head 134 on the bottom plate 132 and a machining surface 135 in the cutting head. The cutting head 134 defines the cutting depth of the blade 130, and by changing the height of the cutting head 134 from the bottom plate 132 the cutting depth may be changed. One end of the cutting head is functionally, for example, hingedly, attached to the bottom plate and the other end or the cutting head is arranged to be movable. The height of the cutting head 134 from the bottom plate may be changed by turning a threaded controller 138 arranged in the bottom plate 132, whereby the controller either pushes the cutting head 134 end, arranged to be movable, away from the bottom plate or, when turned the other way, allows the cutting head 134 end, arranged to be movable, to lower closer to the bottom plate. The controller 138 may be, for example, a screw or a bolt arranged in the bottom plate 132 in such a manner that the screw head or bolt head may be reached from the top of the bottom plate, where the cutting head is, or from below the bottom plate, which is against the strip 121 when the blade is fixed to the strip. As to its operating principle, the blade 130 may be cutting, abrasive, grinding, or sawing. The machining surface 135 of the cutting head 134 in the blade 130 may have a serrated, wedge-shaped, or roughened shape.

[0029] It is obvious to a person skilled in the art that as technology advances the basic idea of the invention may be implemented in many different ways. The invention and its embodiments are thus not restricted to the examples described above but may vary within the scope of the claims.