CH638417A5 - METHOD AND DEVICE FOR CUTTING TUBULAR PARTS. - Google Patents

Description

The present invention relates to the cutting of tubular parts made of rigid materials such as metals, plastics, asbestos-cement, and in particular, but not exclusively, to the cutting of cast iron pipes.

There are known cutting-off machines using at least one disc wheel. These machines have the drawback of being noisy and polluting. In addition, they do not make it possible to obtain a given profile, with a chamfer and / or rounded, on the edge of the cut pipes.

There are also known cutting-off machines using at least one shear blade. These shear-working machines are not suitable for cutting cast iron pipes if a clean cut is required. They also do not make it possible to obtain a chamfered and / or rounded profile on the sectioned edge.

We therefore posed the problem of realizing a method and a device for cutting tubular parts, in particular cast iron, which are rapid, relatively silent, non-polluting, which are capable of making a clean cut without causing deformation, rupture or chipping of the tubular parts and which make it possible to directly obtain a rounded and / or an end chamfer.

To this end, the invention relates to a method of cutting a tubular part driven in rotation about its axis and kept fixed in translation, characterized in that the section to be cut is simultaneously attacked by means of at least a cutting tool having a cutting edge which is contained in an axial plane of the tubular part and whose profile corresponds to the desired configuration for the cut end of this part.

In a particularly advantageous embodiment of this method, the tools are approached from the axis at a rapid speed until they come into contact with the part, then at a slow speed during the penetration of the cutting edges into the wall of this part, and, when the cut is finished, the tools are returned to their starting position at a rapid speed. During cutting, the angle of attack of the tools is varied and the slow speed is progressively reduced, which surprisingly improves the behavior of the tools and the quality of the cut.

The invention also relates to a device for implementing this method. This device, mounted on a machine comprising means for clamping and driving in rotation a tubular end to be cut and means for axially holding the workpiece, is characterized in that it comprises several cutting tools symmetrically distributed around of the axis of rotation and each having a cutting edge which is contained in a plane passing through this axis and whose profile corresponds to the desired configuration for the sectioned end of the part, and a single drive shaft with two directions of rotation connected to each tool by an articulated system transforming the circular movement into an almost rectilinear alternating movement.

In a preferred embodiment, each tool is mounted at the end of an arm of a two-arm oscillating lever, the other arm of this lever being connected to a connecting rod / crank system driven by the motor shaft. Such an articulated system makes it possible to obtain in a very simple manner both a modulation of the speed of movement of the cutting tools from a constant speed of drive in rotation of the shaft, in particular during cutting, and a slight variation in the cutting angle during the penetration of each tool into the wall of the part to be cut.

In addition, each cutting tool advantageously comprises a cutting edge profile corresponding to that to be obtained on the cut end edge, which makes it possible, in a single machining and in a single pass, to cut and profile the end of a tubular part. In particular, the cutting edge of each tool may include a portion of the groove connected to a portion of chamfering by a rounded portion.

Thus, the device of the invention, while being of a simple design, makes it possible to cut and profile the pipes as quickly as possible, in a relatively silent manner and by eliminating the usual chatter phenomena in cutting, while ensuring a excellent appearance of the cut-off part and a long tool life.

The characteristics and advantages will appear during the description which follows.

In the accompanying drawings, given solely by way of example:

fig. 1 is a schematic side elevation view of a cutting-off machine provided with a device according to the invention;

fig. 2 is an end view of this machine taken while looking along line 2-2 of FIG. 1;

fig. 3 is a schematic side view, with partial section, of a part of the machine of FIG. 1, on a larger scale, illus5

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trating the means for driving in rotation and for cutting off a tubular part;

fig. 4 is a partial schematic view corresponding to FIG. 2, on a larger scale than this, illustrating the cutting device;

fig. 5 is an operating diagram of the actuation mechanism of the cutting device;

fig. 6 illustrates the variation curves of the strokes and speeds of the cutting tools as a function of the angle of rotation traversed by the rotary drive shaft;

fig. 7 shows a detail of the actuation mechanism of the cutting device;

fig. 8 is a partial plan view of a cutting tool and of the wall of the tubular part, illustrating different positions of the profiled cutting edge of the tool and the sectioning profile obtained on the tubular part.

According to the embodiment shown in the drawings, the invention relates to a device 1 for cutting and profiling or finishing (making a chamfer and a rounding) of the end with plain male end 2 of a cast iron pipe 3 with socket 4. It would also apply to the cutting of tubes of any material;

steel, aluminum, plastic, asbestos-cement, etc., whatever the diameter of these tubes.

The device 1 is part of a cutting-off machine which comprises at least one support post 5 and a hollow pin body 6 crossed by the pipe 3 along an axis X-X of horizontal rotation which coincides with the axis of the pipe 3.

On the support post 5 are mounted two idle rollers 7 opposite, symmetrical with respect to the axis X-X and axes parallel to this axis X-X. The rollers 7 are intended to support the barrel of the pipe 3 in the vicinity of the socket 4. There are also provided means, known per se and not shown, for bringing a pipe 3 onto the rollers 7 and for introducing of this pipe through the body 6 of the spindle to a position suitable for being cut, and also for removing the pipe after cutting and profiling its plain end 2.

The hollow spindle 8 proper is mounted inside the body 6 by means of bearings 9 (fig. 3). Pin 8,

of axis X-X, carries at one end a coaxial toothed wheel 10, for the rotational drive of the spindle by the output pinion 11 of a motor 12, and it internally carries means for clamping the pipe 3.

These clamping means essentially comprise a reaction ring 13 axially fixed and integral in rotation with the spindle 8, a compression ring 14 movable axially under the effect of an annular hydraulic cylinder 15 with single effect, and an annular jaw made of elastomer 16 disposed between the rings 13 and 14. When the jack 15 is supplied, the jaw 16, compressed axially, inflates radially towards the axis XX and makes the pipe 3 integral with the spindle 8. When the jack 15 is put when discharged, the jaw 16 returns elastically to its rest configuration, in which its internal diameter is greater than the external diameter of the pipe 3.

This device for clamping and driving the pipe 3 in rotation is interchangeable as a function of the different diameters of pipes to be driven and cut. To cut a pipe of a different diameter but located all the same within the dimensional limits of the spindle 8, it suffices to change the rings 13 and 14 and the elastic jaw 16.

The cutting device 1 is carried by the spindle body 6. It comprises a pair of cutting tools 17 and two articulated drive mechanisms 18.

The cutting tools 17 are, in this example, two in number, diametrically opposite with respect to the axis XX and symmetrically placed in an approach and recoil direction located in the horizontal plane P containing the axis of rotation XX and normal to this one. Each tool 17 forms a block having a planar cutting edge 19 (FIG. 8) with profile ABCD, the oblique portion AB forming a chamfer, the curved portion, at B, forming a rounded shape and the straight portion CD, parallel to the axis XX, used to bleed, that is to say to dig a groove until the tubular wall is traversed right through and cut.

The cutting edges 19 of the two tools 17 are contained in the same diametral plane passing through the axis XX and exactly opposite one another, that is to say that each point A, B, C or D of a tool 17 finds its counterpart of the other tool 17 on a line perpendicular to the axis XX. In this example, this diametrical plane is the horizontal plane P. The active side of one of the tools 17 (on the left in FIGS. 2 and 4) is released upwards, that of the other tool 17 downwards.

Each tool 17 is fixed to the upper end of a tool-carrying arm, 20 on one side of the axis X-X and 21 on the other side of this axis. The arms 20 and 21 are contained in two neighboring vertical planes perpendicular to the axis X-X (fig. 1 and 3). In end view (fig. 2 and 4), these arms are vertical or approximately; they are each articulated on an axis 22 carried by the spindle body 6, at an intermediate point of their length, and, at their lower end, each of them is articulated on one end 23 of a connecting rod 24. Each connecting rod is articulated, at its other end, on an eccentric 25. There are thus two eccentrics 25, with the same eccentricity R, keyed onto a single shaft 26 of rotational drive whose axis YY is parallel to the axis XX. The shaft 26 is carried by the spindle body 6, which it passes through, and is driven in rotation over only a fraction of a turn (fig. 5) by a geared motor group 27 provided with means for reversing the direction of rotation and gear change (not shown). More precisely, the gearmotor group 27 has two constant speeds, one fast Vi and the other slow V2, and means for switching from one to the other.

The two eccentrics 25 are circular and arranged symmetrically with respect to the axis Y-Y and have respectively the centers of points E and F located on a cross section of the shaft 26 at a distance R from the center O of this section. The value R of their eccentricity is less (or possibly at most equal) to the radius of the shaft 26. The points E and F are respectively associated with the arms 20 and 21 and are diametrically opposed on a circle of theoretical eccentricity G, of center O and radius R, drawn in phantom in fig. 7.

The articulations of the ends of the connecting rods 24 are effected with the interposition of crowns of needles or balls 24a.

The articulated system 24-25 is, from the kinematic point of view, the perfect equivalent of a connecting rod / crank system with crank arm OE or OF illustrated with strong exaggeration of the radius R in FIGS. 4 and 5, while, in practice, the eccentrics 25 have a very small eccentricity.

Each tool 17 has a lateral positioning lug 28 which, in the working position of the tool, is parallel to the axis X-X. The tool 17 takes place in a groove 29 of the tool-carrying arm 20 or 21 which is oriented parallel to the work plane of each tool 17, therefore horizontally and orthogonally to the axis of rotation XX of the pipe 3. The groove 29 is provided with notches 30 regularly spaced and dimensioned to receive the lug 28 of the tool 17. Thus, the latter is, according to the notch 30 chosen, more or less close to the axis of rotation XX. The notch 30 is chosen according to the diameter of the tubular part to be cut. In the position thus determined by the notch 30 chosen, the tool 17 is clamped in the groove 29 by a conventional device 31 with wedge or clamp and screw.

Of known type, this device, not shown for the purpose of simplification and clarity of the description, comprises a photoelectric cell for locating the position of the end edge of the part 3 to be cut off, a programmable electronic counter or preselection of the desired cutting length, a connection between the photocell and the counter and a connection between the counter and a drive in translation with diabolos of the pipe 3 parallel to its axis of rotation XX. When the end edge of the part 3 has reached the position corresponding to the desired cutting length, the counter stops the drive device in translation. The pipe 3 is then immobilized and clamped in the spindle 8 by means of the clamping device 13 to 16.

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Either to cut the plain end of a pipe 3. This pipe 3 is placed on the machine through the spindle 8 as indicated above, its end close to the socket 4 being placed on the rollers 7 and its barrel being clamped in the vicinity of the plain end 2, in the spindle 8, by the jaw 16. The tools 17 are in their position furthest from the axis XX, which corresponds to position El5 F! points E and F in fig. 5 and 6, point E, located slightly to the right of the top point of circle G.

The geared motor group 12 is started, and the pipe 3 starts to rotate around the axis X-X, driven by the spindle 8 and the jaw 16, in the direction f of FIGS. 2 and 4. The gearmotor group 27 is started at speed Vj in the direction corresponding to the rotation of the shaft 26 in the direction g of FIGS. 2, 4, 5 and 7.

The rotation of the shaft 26 in the direction g is effected over only a fraction of a turn and makes eccentrics 25 travel through the centers E and F of the symmetrical arcs E] s E2, F], F2 on the circle of eccentricity G of radius R (figs. 4 and 5). The heads of the connecting rods 24 oscillate around their centers E, F, which move; this results in a sinusoidal movement of the joints 23 of the connecting rods 24 along an arc centered on the axes 22, which is transmitted with gear reduction to the tools 17. Because of its large radius, the circular movement of the joints 23 is almost rectilinear, and the same is true for tools 17.

The geared motor group is controlled by a device for counting the arcuate path on the circle G of the centers E and F of the eccentrics 25 and of the heads of the connecting rods 24. This counting device triggers the passage of the fast speed Vt (approach of the tools 17 ) at slow speed V2 (parting off) and vice versa (rapid retraction of the tools 17 after parting off), as well as the stopping of the geared motor group 27 and the reversal of the direction of rotation.

When the centers E and F have reached the positions E2 and F2 corresponding to the arrival of the tools 17 in contact with the pipe 3, the counting device controls the passage of the gearmotor group 27 at low speed V2 without reversing the direction of rotation.

Consequently, the tools 17 pass in slow advance or working advance and remain there during the trajectory E2, E3, F2 F3 of the centers E and F of the rod ends (fig. 5).

The tools 17 (fig. 8) start by making a CD length bleed in the wall of the pipe, then, as the wall is bled, the CBA profile with rounding in B also penetrates into the current wall cutting, so that when the cutting edge 19 has passed right through the wall to reach the final position shown in solid lines after passing through the intermediate positions shown in broken lines, the cut end of the pipe 3 follows the profile CBA of the cutting edge 19. Consequently, the pipe is simultaneously cut and profiled at its end following, in this example, a rounding and a chamfer.

When each tool 17 has traveled a predetermined distance greater than the wall thickness of the pipe 3, and consequently after the cut piece 3a of the pipe has fallen, the counting device, returned to zero, stops the gearmotor group 27, reverses the direction of rotation, and again triggers the speed change from V2 to Vj (fast speed). The points E and F travel respectively on the paths E3E1 and F3F, (fig. 5). The ends 23, and therefore also the tools 17 as shown in FIG. 4, travel reversing trajectories at high speed.

The counting device stops the gearmotor group 27 when each tool 17 has returned to its starting position, that is to say is moved away from the wall of the pipe by a preset distance. This immobilizes the shaft 26 and the tools 17.

After parting off, the jack 15 of the spindle 8 is released, which causes the jaw 16 to loosen, which expands axially. The pipe 3 sectioned to the desired length is then removed axially from the spindle 8 and evacuated by the known means not shown mentioned above.

The arms 20 and 21 being articulated around the axes 22, as each tool 17 penetrates, they tilt at an angle x (fig. 4). The tools 17, linked to these arms, tilt at the same angle x.

The initial cutting angle, at the start of the work advance, therefore decreased by x at the end of the cut. This reduction in angle during the penetration of each tool 17 has proved favorable for better holding of the tools 17 and for the quality of the cut.

We will refer to fig. 5 and 6. Fig. 5 illustrates the trajectories of points E and F and of the connecting rod feet 23, and FIG. 6 represents in the form of a graph both the trajectory e and the speed v of the connecting rod feet 23 as a function of the angle of rotation traversed, for example by point F. This trajectory and this speed have a sinusoidal shape obtained at from the two constant values V! and V2 of the speed of rotation of the motor shaft 26. Due to the transmission of the movement by the levers 20 and 21, it can be considered that the curves of FIG. 6 represent the shape of the movement (space and speed) of the cutting tools 17.

The useful parts of the trajectory curve and of the velocity curves corresponding to the speeds V have been shown in reinforced lines. and V2 of rotation of the motor shaft 26. In this domain, the curve corresponding to Vt is located above the curve corresponding to V2.

We see on this diagram of fig. 6 that, on the course F ^, the rapid approach speed, which is modulated by the kinematics connecting rod 24 / eccentric 25, decreases slightly after passing through a maximum. At the end of rapid approach, when the counting device triggers the speed change to cause the shaft 26 to shift to slow speed V2, the speed curve marks a corresponding fall ab by passing from the curve corresponding to Vj to that corresponding to V2.

During the working advance of each tool 17, which is done at low speed V2 of the gearmotor group 27, the speed curve clearly expresses the progressive deceleration obtained by the modulation of the speed of the shaft 26 between the points F2 and F3. This modulation is carried out only by the kinematics of the connecting rods 24 and the eccentrics 25 without using an expensive and complex device for electronic variation of the speed of the geared motor group 27.

At the end of the cut, the reversal of the direction of rotation and the speed change of the shaft 26 are reflected on the speed diagram by a jump cd from the lower curve corresponding to V2 to the upper curve corresponding to Vj. The kinematics of the eccentrics 25 and of the connecting rods 24 first increases this speed of recoil then slows down the increase in this speed, which reaches its maximum at the end of recoil of the tools 17 when they have almost returned to the starting point Els Fx .

Within certain limits, the same cutting device (that is to say the same spindle 8, the same connecting rod system 24 / eccentric 25, the same tools 17 and the same articulated system 20-21) can receive parts from different diameters. For this purpose, the spindle 8 remaining the same, the only parts to be changed when changing the diameter are the rings 13 and 14 and the annular elastic jaw 16. For the cutting tools 17, it suffices to change their position by loosening the device 31, by placing the pin 28 in another notch 30 of the arm 20 or 21, which is closer to the axis XX if the diameter of the part to be cut is smaller and more distant if this diameter is more large, and tighten the device 31.

Thanks to the profiling-cutting device of the invention, that is to say thanks to the combination of the connecting rod / crank system (eccentrics 25 and connecting rods 24) and of the articulated transmission system with arms 20-21, and thanks to the use of cutting tools 17, excellent cutting results are obtained (speed, absence of chattering, silence, very reduced wear of tools 17). These advantages are linked, on the one hand, to the elimination of all rectilinear guidance of the cutting tools and, on the other hand, to the progressive reduction in the speed of advance of each tool 17 and to the slight modification of the cutting angle as the tools penetrate the material, this angle variation facilitating the removal of shavings. This result is obtained while respecting a principle of simplicity of design.

Another advantage results from the use of two diametrically opposed tools 17 which make it possible to cancel any radial reaction

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on the sectioned pipe 3: the two radial forces are balanced, and there is no reaction on the device for driving the pipe in rotation.

One could use only one tool 17, one arm 20 or 21, one connecting rod 24 and one eccentric 25. But the cutting time 5 would be twice as long as in the case of the two tools cutting, and we would lose the advantage of balancing the radial cutting forces on the pipe. In addition, a rigid jaw clamping system should be used in place of the elastic annular jaw 16 because of the risk of eccentricity. 10

On the other hand, there may be around the section of the pipe to cut more cutting tools 17, for example three tools at 120 ° from one another, or four tools arranged in two diametrically opposite pairs, which makes it possible to cut even faster. For this, one or two additional eccentrics such as 25 and one or two additional connecting rods 24 connected to one or two additional arms such as the arms 20 and 21 are each wedged on the drive shaft 26 each carrying a tool 17 and articulated on a shaft. fixed as 22 judiciously disposed on the spindle body 6.

It is also possible to replace each of the tools 17 with a double tool with two cutting edges suitably offset in the circumferential direction, which involves a total of four cutting edges for the embodiment with two cutting tools.

Of course, what has been described for cutting a cast iron pipe is applicable to that of a tube or other tubular part made of another rigid material such as steel, a rigid plastic, asbestos-cement. , etc.

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Claims (10)

638,417 1. Method for cutting a tubular part driven in rotation about its axis and kept fixed in translation, characterized in that the section to be cut is simultaneously attacked by means of at least one cutting tool having a cutting edge which is contained in an axial plane of the tubular part and whose profile corresponds to the desired configuration for the sectioned end of this part. 2. Method according to claim 1, characterized in that the tool or tools are approached from the axis at a rapid speed until they come into contact with the part, then at a slow speed during the penetration of the cutting edges into the wall of this part, and, when the cutting is finished, the tool or tools are brought back to their starting position at high speed. 2 3. Method according to claim 2, characterized in that the slow speed is progressively reduced during cutting. 4. Method according to one of claims 1 to 3, characterized in that the angle of attack of at least one tool is varied during cutting. 5. Cutting device for implementing the method according to one of claims 1 to 4, mounted on a machine comprising clamping means and driving in rotation of a tubular end to be cut and axial holding means of the part, characterized in that it comprises several cutting tools (17) symmetrically distributed around the axis of rotation (XX) and each having a cutting edge (19) which is contained in a plane passing through this axis and whose profile corresponds to the desired configuration for the cut end of the part (3), and a single motor shaft (26) with two directions of rotation connected to each tool (17) by an articulated system (25-24-20 ) transforming the circular movement into an almost rectilinear alternating movement. 6. Device according to claim 5, characterized in that the reciprocating movement is sinusoidal. 7. Device according to claim 6, characterized in that each tool (17) is mounted at the end of an arm of an oscillating lever (20,21) with two arms, the other arm of this lever being connected to a connecting rod / crank system (24-25) driven by the motor shaft (26). 8. Device according to claim 7, characterized in that the connecting rod / crank system (24-25) comprises an eccentric (25) wedged on the motor shaft (26) and a connecting rod (24) articulated at one end on this eccentric and at the other end on the second arm of the swing lever (20,21). 9. Device according to one of claims 5 to 8, characterized in that the motor shaft (26) has two rotational speeds and can be driven, in one direction, at fast speed then at slow speed and, in the other direction, at fast speed. 10. Device according to one of claims 5 to 9, characterized in that the cutting edge (19) of each tool (17) comprises a grooving part (CD) connected to a chamfering part (AB) by a part rounded.