CN1005324B - Method for longitudinal cutting of tubular fibre products and device therefor - Google Patents

Abstract

The present invention relates to cutting tubular fibrous products. More specifically, it is suitable for cutting a stepped slit along the longitudinal direction on such a pipe wall. According to this method, two slightly staggered quasi-radial slits are cut on the shell wall, and an additional slit is cut in a direction substantially perpendicular to the radial cutting plane. The invention also includes a device for producing said incisions, comprising a cutting tool consisting of two blades (2, 3) and an auxiliary blade (17).

Description

Method for longitudinal cutting of tubular fibrous articles and device therefor

The present invention relates to a method and apparatus for cutting tubular fibrous articles, and more particularly for longitudinal cutting of the walls of such articles along stepped parting planes.

The invention is particularly suitable for cutting insulating tube shells, i.e. hollow cylindrical tube shells made of fibres and coated with a polymeric binder.

Such a tube shell based on mineral fibres such as glass fibres can be used for heat insulation of pipes. The pipe shell is cut longitudinally, unfolded and then enclosed on a pipeline, and then the pipe shell is closed. However, the cartridge thus mounted leaves a gap between the edges of its cutout, which may cause heat loss. Such heat loss is more likely to occur if the cut plane is radial.

Therefore, efforts have been made to make the slit into a stepped surface as much as possible so that both side edges of the slit overlap each other when the heat-insulating pipe case is closed, thereby reducing the possibility of forming a thermal bridge and suppressing heat loss.

There is a known method for making a stepped cut through the tube wall in the longitudinal direction in a mineral fiber based insulation tube.

According to this method, two substantially radially parallel cuts are made from the inner and outer wall surfaces of the envelope, respectively, to a certain depth. Neither of these cuts through the shell wall, but each has an inner edge or termination terminating within the shell wall. In order to penetrate the slit in the wall of the envelope, a shearing force is applied to the envelope in the immediate vicinity of the two parallel slits, which shearing force acts on the material between the two slits, thus tearing the material apart.

However, this method does have some drawbacks, in particular the unsatisfactory condition of the tearing sites on the envelope. The part of the tube wall on the tube shell is compressed when two parallel incisions are cut, and then is suddenly stretched, and the stress is easy to separate the fiber structure, so that the incision shape is irregular. The actual manufacturing process of the cartridge is to apply the adhesive to the web of fibers and to wind the web impregnated with the adhesive onto a heated mandrel. The wound roll is placed in a polymerization oven to polymerize the binder. The structure obtained in this way has a certain cohesion and is not easy to break.

The object of the present invention is to provide a method for making stepped cuts in cylindrical fibre products, in particular insulating tube shells based on mineral fibres and coated with a polymeric binder, so as to reduce the likelihood of thermal bridges forming on the insulating layer, and furthermore, such cuts are entirely regular in shape and do not cause alterations in the fibre structure.

For this purpose, the invention proposes a method for making stepped longitudinal cuts in which two cuts are made simultaneously in the radial direction from the inner and outer surfaces of the wall of the envelope, offset by a small distance from each other and parallel to each other, and an auxiliary cut is made in the wall thickness of the envelope in the tangential direction or in the direction perpendicular to the radial cuts, in order to connect the inner edges of the two radial cuts.

In one aspect, the present invention relates to a method of forming a slit which requires relative movement between the cartridge and a cutting tool consisting of two primary blades and an auxiliary blade for cutting the cartridge wall. The two main blades are offset from each other by a small distance and are arranged in two planes which are substantially parallel to each other, one blade cuts the outer wall of the envelope and the other blade cuts the inner wall of the envelope, the cuts being all radial, the auxiliary blades being arranged in a plane which is substantially perpendicular to the plane of the main blades so as to cut a cut which is substantially perpendicular to the radial cuts.

The relative position of the auxiliary blade and the cartridge is adjusted so that the blade remains within the range of the cartridge wall thickness throughout the cutting length, thereby ensuring that the auxiliary or tangential cuts are always within the cartridge wall.

The invention is further characterized in that the method generates a compressive stress on the shell wall acting on both the inner wall and the outer wall, the resultant of which reaches a maximum value over a width approximately corresponding to the distance between the planes of the two main blades in the middle of the shell wall, and at the same time, a stress in the opposite direction is also applied to the shell wall as a result of the auxiliary blades pushing the fiber layer outwards. Therefore, when the cutting operation is completed, that is, when the inner edges of the two parallel cuts are connected with the tangential cuts, a through cut is formed on the tube shell wall, the middle area of the tube shell wall reaches a certain stress balance, so that the risk of damage to the tube shell wall is reduced.

Furthermore, in addition to the very advantageous mechanical effects described above, the provision of auxiliary blades is also advantageous in order to keep the relative position between the cartridge being cut and the tool used constant.

In fact, in the current cutting methods, such as the method of cutting straight slits, the relative movement between the cartridge and the knife is obtained by fixing the knife so that the cartridge moves longitudinally. Such conditions facilitate continuous operation and during the processing of the insulated shell tube, the shell tube may be formed with a binder impregnated fibrous web followed by cutting.

However, during such operations, there is often an abnormal relative movement between the plane of the blade and the axis of the cartridge passing longitudinally through the blade, which may occur in two ways, one lateral movement and the other in which the position of the blade within the wall thickness of the cartridge changes, thus making the cut irregular, with the result that the slit obtained over the whole length of the cartridge is not rectilinear.

An auxiliary member is provided for simultaneously applying a force in a direction perpendicular to the longitudinal direction of the relative movement of the blade and the cartridge to guide the relative movement between the cartridge being cut and the cutting tool consisting of the blade so that the cartridge and the tool each remain in the desired position, thereby advantageously avoiding the above-mentioned drawbacks. The stabilizing effect of this auxiliary member on the relative position of the cartridge and the knife may be either in the horizontal plane or in the vertical plane.

According to a further advantageous embodiment of the invention, the force balance can be achieved to a greater extent than is limited to the region in the middle of the envelope wall. According to this embodiment, instead of two, four radial blades are used for cutting in addition to the tangential knife, so that the desired stepped slit is obtained and the fibrous structure is subjected to less stress.

More specifically, at a location within the shell wall thickness, two additional cutters are employed, one directed toward the shell outer wall to meet the cut made from the outer wall and the other directed into the tube to meet the cut made from the inner wall.

The manufacturing method of the cutter can ensure the pace of cutting operation. As previously mentioned, the tangential cuts are made by the auxiliary blades which are mounted in a plane perpendicular to the two main blades. In order to obtain the turning of the radial cut required from the cut in the tangential direction, the auxiliary blade is provided with two fins, an upper fin in the plane of the blade cutting the cartridge from the outer wall surface and a lower fin in the plane of the blade cutting the cartridge from the inner wall surface.

An advantage of this embodiment of the invention is that a satisfactory stress balance can be achieved on the cut envelope wall with respect to the plane of the half wall thickness.

The invention also relates to a method for cutting tubular fibre products, i.e. insulating tube shells which are based on mineral fibres and are coated with a polymeric binder, according to which a symmetrical wall surface of the tube wall is cut in the direction of the longitudinal axis of the tube shell, and a rectilinear cut is made, the cut-in depth of which is only a part of the wall thickness of the tube shell.

The invention also relates to a device for carrying out the method, which comprises a set of tools consisting of two main blades and an auxiliary blade. The two main blades are arranged in two substantially parallel planes offset from each other by a distance, the root of the upper blade is fixed to the upper edge of the lower blade, and the back portion of each blade is fixed to the blade holder. The auxiliary blade is arranged on the extension of the connecting section of the two main blades. The blade holder of the lower blade can also be provided with a blade for cutting a part of the wall surface on the other side of the cylindrical hollow tube shell.

Further features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings 1 to 7. Figures 1 to 7 show a specific example of a device for cutting a cartridge according to the method of the invention. In these figures:

Fig. 1 is a schematic front view showing the position of the cutting device within the cartridge;

FIG. 2 is a front view of a tool designed according to this invention;

Figure 3 shows the shape of the cut seen axially from the cartridge;

FIG. 4 is an enlarged view of the auxiliary tangential blade shown in FIG. 1;

FIG. 5 is a view in the direction D of FIG. 4;

FIG. 6 is a partial view in the direction C of FIG. 2;

fig. 7 is a cross-sectional view taken along line A-A of fig. 2.

Fig. 1 is helpful in understanding how the cutting method of the present invention is performed. The actual tool 1 shown comprises two blades 3 and 3, the blade 2 being fixed to a blade holder 4, not shown, which is connected to a blade holder, the blade 3 being mounted on a blade holder 5. In this embodiment, the knife is fixed and the relative movement between the tube housing 6 and the knife is obtained by means of a mechanism, not shown, which moves the cut tube housing 6 along its longitudinal axis 7 in the direction indicated by the arrow F. The two blades 2 and 3 are separated by a connecting surface P. The blade and blade support are movable in a vertical plane by a suitable mechanism, not shown, to adjust the position of the cutter according to the wall thickness and position of the cartridge to be cut.

The tube shell 6 has a wall thickness e and is cut at two locations on its wall, namely locations 8 and 9. The connection plane P is preferably located at a position corresponding to half the thickness of the tube wall 8, i.e. about 1/2e, so that the tangential blades can be aligned with the middle of the tube wall. As can be seen from the drawing, on the blade holder 5, behind the blade 2, a blade 10 is added for making a rectilinear cut 21 (fig. 3) of a certain depth in the tube wall 9.

The method proposed by the present invention is mainly concerned with the cutting of the pipe wall 8, so that the emphasis described herein is placed on the tool consisting of the blades 2 and 3. Blades 2 and 3, and blade 10 each include blade edge portions 11, 12 and 13 with beveled edges 14, 15, 16.

Fig. 2 shows the body of the tool 1. The figure again shows the blade 2 and the blade 3, their edge portions 11 and 12 being separated by a connecting plane P. The auxiliary blade 17 is fixed to the connection plane P and will be referred to hereinafter as a projecting blade, which blade, as is evident from fig. 4 and 5, comprises a flat portion 18, the edge portion 19 of which is adapted to cut a tangential slit 20. On both sides of the flat portion 18 there is a fin 22 and 23, one of which, fin 22, is arranged above the plane of the projection and the other fin 23 is arranged below this plane. As can be seen from fig. 4 and 5, the fins are triangular in shape. The two fins each have a cutting portion 24 and 25, the edge 26 and 27 of each portion being wedge-shaped so as to be able to wedge into the material being cut quickly. It is the presence of these fins that simultaneously draws out the cutting action of the blades 2 and 3 from the outer and inner surfaces of the envelope wall 8, respectively, so that radial cuts 28 and 29 are made outwards from half the wall thickness e of the envelope 8, i.e. at the tangential cuts 20.

The ideal shape of the tool should be that the structure on both sides of the connecting plane P of the blade 2 and the blade 3 is completely symmetrical with respect to this plane. The advantage of this design is that the stress balance on the internal structure of the fiber can be optimized at the moment of cutting. The angle subtended by the edge 14 of the blade 2 and the front edge 26 of the fin 22 is equal to the angle between the front edge 27 of the fin 23 and the edge 15 of the blade 3, the edges 14 and 27 are parallel, and the edges 15 and 26 are parallel. Thanks to these means, it is ensured that the force balance is achieved at every point in the wall thickness direction of the envelope, proceeding from the tangential slit 20, on both sides of the connection plane P.

The angle between the edge 14 of the blade 2 and the edge 15 of the blade 3 is advantageously between 30 and 50 degrees, preferably around 40 degrees. The angle between the edge 14 of the blade 2 and the edge 26 of the fin 22, the edge 15 of the blade 3 and the edge 27 of the fin 23, respectively, is between 15 degrees and 25 degrees, preferably about 20 degrees, with respect to the connecting plane P. The size of the cutter used will vary depending on the wall thickness of the cartridge to be cut and the inner diameter of the cartridge. The size of the cartridge that can be cut using the device of the present invention is in the range of about 20 mm to 150 mm in wall thickness and about 50 mm to 350 mm in inside diameter. The other parts of the device do not need to be changed, and only the cutter is detached from the blade frame and replaced by another cutter.

Claims (11)

1. A method for making a longitudinal stepped slit in the wall of a tubular fibre product, for example an insulating sleeve made of mineral fibres, in which polymeric binder is distributed, the method comprising partly cutting the wall (8) of the product, on the one hand from the inside and on the other hand from the outside, radially so as to create two substantially parallel slits (29,28) which are slightly offset from each other, each slit forming an inner edge in the thickness of the wall, characterized in that, while two radial slits are being made, a third slit (20) is made in the wall of the product, which third slit is substantially perpendicular to the radial cutting plane, so that the inner edges of the radial slits meet the third slit.

2. The method of claim 1 wherein two additional radial cuts are made from the interior of the shell wall simultaneously with the cuts, one of which extends outwardly of the shell wall and meets the cut made from the outer wall surface and the other extends inwardly of the inner wall surface of the shell and meets the cut made from the inner wall surface.

3. A method according to claim 1 or 2, wherein the third cut is equidistant from the inner and outer surfaces of the wall of the article.

4. An apparatus for carrying out the method of any one of claims 1 to 3, the apparatus comprising

(A) A cutting tool comprising two blades (2, 3) with cutting edges (11, 12) arranged in two substantially parallel planes offset from each other by a distance, adapted to partly cut a wall of a tubular fibrous product, on the one hand from the inside and on the other hand from the outside, so as to create two substantially radially parallel cuts (29,28) in the wall,

(B) Means for providing relative movement between the article and the cutting tool,

The invention is characterized in that the two blades (2, 3) are separated by a connecting plane (P) which is placed in the thickness of the wall to be cut, wherein it further comprises an auxiliary blade or projecting blade (17) which is placed in the extension of the connecting plane (P) and in a plane substantially perpendicular to the plane of the blades (2, 3) so as to create a third cut substantially perpendicular to the two cuts (29,28).

5. The apparatus according to claim 4, characterized in that the respective cutting edge portions (11, 12, 18) of the blades (2,3,17) each have a wedge-shaped cutting edge (14, 15, 19).

6. The device according to claim 4 or 5, characterized in that two fins (22, 23) are added to the projecting blade (17), one fin (22) being located above the plane of the projecting blade (17) and the other fin (23) being located below the plane of the projecting blade (17).

7. The apparatus according to claim 6, wherein the fins (22, 23) have a triangular profile and each have a cutting portion (24, 25) starting from a wedge-shaped cutting edge (26, 27).

8. The apparatus as claimed in claim 6, characterized in that the angle formed by the cutting edge (14) of the blade (2) and the cutting edge (26) of the fin (22) is equal to the angle formed by the cutting edge (15) of the blade (3) and the cutting edge (27) of the fin (23).

9. The apparatus of claim 8 wherein said included angle is about 20 degrees.

10. The device according to any one of claims 4, 5, 7, 8, 9, characterized in that the angle between the cutting edge (14) of the blade (2) and the cutting edge (15) of the blade (3) is about 40 degrees.

11. The device as claimed in claim 6, characterized in that the angle between the cutting edge (14) of the blade (2) and the cutting edge (15) of the blade (3) is approximately 40 degrees.

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