Eccentric Cutting Drive Having a Variable Stroke

Abstract

A pipe cutting machine, which includes a hole-type movable cutting die (6b), which is driven by a drive lever (7), by means of which circular movements with a continuously variable stroke (h) can be performed, an eccentrically shaped crank pin bearing (26) in an outer shaft (18), in which a crank pin (11), which is arranged eccentrically on a crank pin drive (23), is movably supported in relation to the outer shaft (18), the crank pin (11) being in operative connection with the drive lever (7).

Claims

1. Cutting device comprises a hole-type movable cutting die (6b), which is driven by a drive lever (7), by means of which circular movements with a continuously variable stroke (h) can be performed, an eccentrically shaped crank pin bearing (26) in an outer shaft (18), in which a crank pin (11), which is arranged eccentrically on a crank pin drive (23), is movably supported in relation to the outer shaft (18), the crank pin (11) being in operative connection with the drive lever (7).

2. Cutting device according to claim 1, characterised in that a centre line (M3) of the crank pin drive (23) and a centre line (M2) of the outer shaft (18) and a centre line (M2) of the inner shaft (14) are arranged in pairs parallel to one another.

3. Cutting device according to claim 1, characterised in that the crank pin drive (23) has an internal toothing (24) which meshes with an external toothing (22) of an inner shaft (14).

4. Cutting device according to claim 1, characterised in that the inner shaft (14) is passed through a tubular section of the outer shaft (18).

5. Cutting device according to claim 1, characterised in that the centre line (M3) of the crank pin drive (23) and the centre line (M2) of the outer shaft (18) are arranged eccentrically relative to one another in any possible relative position of the crank pin drive (23) and the outer shaft (18).

6. Cutting device according to claim 1, characterised in that a crank pin (11) of the crank pin drive (23) and the centre line (M2) of the outer shaft (18) lie on one another in a zero stroke position.

7. Cutting device according to claim 1, characterised in that the inner shaft (14) is driven by a first servomotor (12) and the outer shaft (18) is driven by a second servomotor (13).

8. Cutting device according to claim 1, characterised in that a variable-stroke circular movement of the crank pin (11) can be set by a speed differential of the first and second servomotors (12, 13).

9. Cutting device according to claim 1, characterised by a cutting mandrel (3a, 3b) which can be introduced into the pipe (2) with a section (3a) which is stationary relative to the cutting device (1) and a section (3b) which is movable relative thereto.

10. Method for cutting off a profiled section from a longitudinal profiled section (2), wherein: a cutting die (6a, 6b) of a cutting device (1) is set to a zero stroke position, a longitudinal profiled section (2) is placed in a cutting die (6a, 6b), an inner shaft (14) and an outer shaft (18) are operated at the same rotational speed, a speed differential of the inner shaft (14) and of the outer shaft (18) is set and as a result a position of the crank pin (23) is rotated radially outwards out of a centre line (M2) of the inner shaft (14), the crank pin (23) drives the cutting die (6a, 6b) by means of a drive lever (7) to an outwardly rotated movement which cuts off the longitudinal profiled section (2) from the long profiled section (2a) in an outwardly rotated movement.

11. Method according to claim 10, characterised in that the speed differential is firmly set and as a result the stroke (h) changes continuously and the crank pin (23) describes a spiral movement which drives the drivable cutting die (6b) to a spiral movement which cuts off a longitudinal profiled section (2a) from the long profile section (2a) in a spiral movement.

Description

[0036] The invention is described with reference to an embodiment in ten figures. In the drawings:

[0037] FIG. 1 shows a sectional view of the functional principle a cutting device according to the invention of a pipe cutting machine in a zero stroke position,

[0038] FIG. 2 shows a sectional view according to FIG. 1 in a maximum stroke position,

[0039] FIG. 3 shows an exploded view of the cutting device,

[0040] FIG. 4 shows an outer shaft in a front view,

[0041] FIG. 5 shows the outer shaft in a side view,

[0042] FIG. 6 shows a crank pin drive in a front view,

[0043] FIG. 7 shows the crank pin drive in a side view,

[0044] FIG. 8 shows the cutting device of the pipe cutting machine according to the invention in a perspective view,

[0045] FIG. 9 shows the cutting device with the cover removed,

[0046] FIG. 10 shows a sectional view of the cutting device in FIG. 8 along the line VIII-VIII.

[0047] The functional principle illustrated in FIG. 1 shows the mode of operation of a cutting device 1 according to the invention of a pipe cutting machine. The pipe 2 to be cut is shown in the lower region. A two-part cutting mandrel 3a, 3b, which has a somewhat smaller external diameter than an internal diameter of the pipe 2 to be cut, is introduced into the pipe 2, so that the cutting mandrel 3a, 3b can be pushed to and fro without jamming in the pipe 2. The cutting mandrel 3a, 3b has a stationary part 3a and a movable part 3b, during the cutting off of a pipe section 2a from the pipe 2 the stationary part 3a remains in a fixed position relative to the housing and to the entire support structure of the pipe cutting machine, whilst the movable part 3b is movable relative to the stationary part 3a and is spaced apart from the stationary part 3a with a peripheral gap width of approximately b=0.1 mm, whilst the movable part 3b is supported approximately centrally on the stationary part along a cutting mandrel central axis M1. The support is not shown in detail here. Aligned with the gap 4 of the cutting mandrel 3a, 3b is a gap, which is preferably the same width, between a stationary cutting die 6a and a drivable cutting die 6b. The pipe piece 2a is cut off from the pipe 2 by an increasingly large helical circling movement of the drivable cutting matrix 6b relative to the stationary cutting die 6a. The cutting mandrel 3a, 3b counteracts a distortion of a pipe wall of the pipe 2, the cutting mandrel 3a, 3b, in particular the movable part 3b of the cutting mandrel 3a, 3b, transmits the forces radially through the pipe section 2a to be cut and onto the opposing pipe wall.

[0048] The drivable cutting die 6b is designed as a circular hole which has a sharp hole edge and is arranged on a drive lever 7. The drive lever 7 is supported in a pivot bearing 8 with a vertical guide, an axial guide 9 for the drive lever 7 is provided at a small distance from the cutting die 6a, 6b and prevents pivoting out of the drive lever 7 in the pushing direction V of the pipe 2.

[0049] The drive lever 7 is driven by means of a crank pin 11 for the helical movement according to the invention.

[0050] In this case the helical movement is generated by two superimposed movements which are generated respectively by a servomotor 12, 13. Each of the two servomotors 12, 13 runs at a rotational speed of 5000-6000 r.p.m.

[0051] A first servomotor 12 drives an inner shaft 14 by means of a gear transmission, and for this purpose a first drive gear 16 is provided at one end of the inner shaft 14 and interacts with a first pinion 15 which is driven by the first servomotor 12. The inner shaft 14 is supported in two inner bearings 17a, 17b, the inner bearings 17a, 17b being provided internally in an outer shaft 18.

[0052] The outer shaft 18 in turn is driven by the second servomotor 13 by means of a transmission comprising a second drive gear 19 and a second pinion 21. At the other end of the inner shaft 14 a gear 22 of an inner shaft 14 for a crank pin drive 23 is provided. The gear 22 having an external toothing on the inner shaft 14 meshes with an internal toothing 24 on the crank pin drive 23. The outer shaft 18 widens abruptly towards the drive lever 7. On the widened section it has a crank pin bearing 26 for the crank pin drive 23, but for outer periphery 27 is arranged eccentrically relative to the outer shaft 18. The eccentricity is illustrated by the different wall thickness of the outer shaft 18 in the section of the crank pin bearing 26. The crank pin bearing 26 is likewise provided with the eccentricity relative to the outer periphery. The external toothing of the inner shaft 14 meshes with the internal toothing 24 of the crank pin drive 23 at the point at which the wall thickness of the outer shaft in the widened section is greatest, this being the case in FIG. 1 at the bottom.

[0053] A centre line M2, which runs centrally through the inner shaft 14 and the gear 22 of the inner shaft 14 is a line of rotational symmetry of the inner shaft 14 and of the gear 22 of the inner shaft 14. However, the crank pin bearing 26 of the outer shaft 18 is arranged eccentrically relative to the centre line M2 of the inner shaft 14. The centre line M2 of the inner shaft 14 coincides with a centre line M2 of the outer shaft 18. Furthermore, the crank pin drive 23, which is depicted here as a bowl or lid, is provided with the crank pin 11, wherein the crank pin 11 in turn is arranged eccentrically relative to a centre line M3 of the crank pin drive 23. In this case the eccentricity of the crank pin drive 23 corresponds to the eccentricity of the outer shaft 18, so that in a corresponding position, as illustrated in FIG. 1, the eccentricities e cancel each other out and the crank pin 11 is arranged on the centre line M2 of the inner shaft 14. When the first and the second servomotor 12, 13 run at an identical rotational speed, the outer shaft 18 and the inner shaft 14 rotate without relative movement, so that the relative position which is illustrated in FIG. 1 is also maintained in the event of rotary movement, that is to say the crank pin 11 is always arranged on the centre line M2 of the system, that is to say the centre line M2 of the inner shaft 14, and performs a rotary movement with the rotational speed of the servomotors 12, 13.

[0054] A stroke h of the cutting device 1 is zero in the state according to FIG. 1; that is to say, in particular, that the drivable cutting die 6b does not perform any movement. In this position the pipe 2 can be introduced into the cutting die 6a, 6b.

[0055] FIG. 2 shows a position of the cutting arrangement with a maximum stroke h. The state according to FIG. 2 is reached by the outer shaft 18 being stationary or running at a low rotational speed and the inner shaft 14 being driven or running at a higher rotational speed than the outer shaft 18; the crank pin drive 23 rotates in the crank pin bearing 26 due to the different rotational speed of the outer shaft 18 and the inner shaft 14. The speed differential leads to a continuous variation of the angular position between the first and second servomotor 12, 13. The stroke performs a sinusoidal movement. After a half revolution or a 180 rotation of the crank pin drive, the crank pin 11 reaches the position according to FIG. 2. The crank pin 11 rotates around the centre line M3 of the crank pin drive 23, which is arranged offset relative to the centre line M2 of the inner shaft 14 and is arranged parallel thereto.

[0056] In particular, by setting a speed differential of the crank pin drive 23 relative to the outer shaft 18 a continuous variation of the stroke h of the crank pin 11, i.e. the distance of the crank pin 11 from the centre line M2 of the system, i.e. the centre line M2 of the inner shaft 14, can be set. In FIG. 2 the maximum stroke h is set, and the eccentricity of the crank pin drive 23 and the eccentricity of the outer shaft 18 must correspond, so that a zero stroke position according to FIG. 1 can be set. When a specific stroke h is reached, the speed differential, that is to say the angular position differential, is kept at the set value. The stroke h then remains constant at the set value. Depending upon the magnitude of the speed differential, the frequency of the sinusoidal movement of the stroke h changes.

[0057] In the maximum stroke position according to FIG. 2, the drivable cutting die 6b has a position which is shifted relative to the stationary cutting die 6a, so that the pipe section 2a is cut off from the pipe 2 or is cut into. If the maximum stroke is to be maintained, the rotational speed of both servomotors 12, 13 is set to be the same.

[0058] In the maximum stroke position illustrated in FIG. 2, with subsequent synchronisation of the rotational speeds of the first and second servomotor 12, 13, the crank pin 11 is driven to perform a purely rotational movement around the centre line M3 of the crank pin drive 23, which leads to a circular movement of the drivable cutting die 6b. The stroke of the crank pin 11 from the centre line M2 of the inner shaft 14 is continuously adjustable. By the setting of a speed differential between the outer and inner shafts 18, 14, first of all a continuous distancing of the crank pin 11 from the centre line M2 of the inner shaft 14 can be achieved, and then an approach of the crank pin 11 to the centre line M2 of the inner shaft 14 can be achieved. In the event of a high differential speed, the stroke h changes quickly, and in the event of a low differential speed the stroke h changes slowly. However, the stroke h always changes in the event of a speed differential, which leads to an angular position differential of the two servomotors 12, 13. This preferably presupposes that the speeds of the servomotors 12, 13 translate in the same way into the speeds of the inner and outer shaft 14, 18. The variation of the stroke h is superimposed by the existing rotational movement of the crank pin 11 on the basis of the speed differential of the inner and outer shaft 14, 18, so that overall a helical movement of the crank pin 11 illustrated in FIG. 2 and thus a helical movement of the movable cutting die 6b is caused, which leads to a cut which places an increasing rotational load on the pipe wall.

[0059] FIG. 3 shows a construction of the cutting device 1 of the pipe cutting machine in an exploded view, and in this case the references used in FIGS. 1 and 2 also appear in FIG. 3 with the same significance.

[0060] However, the crank pin bearing 26 of the outer shaft 18 is formed eccentrically relative to the centre line M2 of the inner shaft 14. This is difficult to see in FIG. 3, but FIGS. 4 and 5 show the eccentricity of this arrangement, which is e=3 mm. In this case the eccentricity relates to the relative position of a circular inner bore, which is, however, concentric with the crank pin bearing 26, relative to the circular outer periphery 27 of the outer shaft 18. FIG. 5 shows the outer shaft 18 in a side view, wherein the eccentricity cannot be recognised.

[0061] The outer shaft 18 is driven by means of the second drive gear 19 which is driven by the second pinion 21 on the second servomotor 13. The inner shaft 14, which is supported in the two inner bearings 17a, 17b internally in the outer shaft 18, is passed through the outer shaft 18; the first drive gear 16 is arranged adjacent to the second drive gear 19; this is illustrated in FIG. 1 and the first servomotor 12 drives the first drive gear 16 of the inner shaft 14 with the first pinion 15. The inner shaft 14 is connected, in a fixed position and non-rotatably, to the gear 22 with external toothing on the inner shaft 14, the gear meshing with the internal toothing 24 of the crank pin drive 23. The crank pin drive 23 is shown without a crank pin 11, but it has a central opening 11 in which a pin 7 arranged fixedly on the drive lever 7 engages rotatably. The pivot bearing 8 is illustrated in the upper region of FIG. 3 and the axial guide 9 for the drive lever 7 is illustrated in the lower region.

[0062] The crank pin drive 23 in turn can be seen in FIGS. 6 and 7. In this case it can be seen in FIG. 6 that the outer periphery of the crank pin drive 23 in FIG. 6, which rests in a fixed position in the crank pin bearing 26 of the outer shaft 18 according to FIGS. 4 and 5, is formed eccentrically with respect to the centre point of the circular central opening 11, which corresponds in its function to the crank pin 11. In other words, a rotary movement of the central opening 11 leads to an eccentric movement or a circular movement around the centre point of the outer periphery of the crank pin drive 23. The opening 11 is non-rotatably connected to the internal toothing 24 according to FIG. 7, in which the gear 22 according to FIG. 3 engages.

[0063] The mode of operation corresponds to the mode of operation illustrated in FIGS. 1 and 2.

[0064] The cutting device 1 of FIG. 3 is illustrated in the assembled arrangement in FIGS. 8, 9 and 10.

[0065] FIG. 8 shows the cutting device 1 with a housing 80, the drive lever 7 is arranged movably with respect to the cutting device 1, and at the bottom the pipe 2 is illustrated, which is already inserted through the stationary and the drivable cutting dies 6a, 6b, and the cutting mandrel 3a, 3b is inserted in the pipe 2.

[0066] FIG. 9 shows the cutting device 1 with the housing 80 removed, and in this case it can be seen that the first and the second servomotor 12, 13 with their pinions 15, 21 engage in output gear wheels 16, 19 of the inner and outer shaft 14, 18 and drive them.

[0067] FIG. 10 shows the cutting device 1 in a lateral sectional view, and the components illustrated in FIGS. 1, 2 and 3 with their functions are accordingly illustrated in FIG. 10. Reference is made the description relating to FIGS. 1, 2 and 3 with regard to the mode of operation. FIG. 10 shows the drivable cutting die 6b having a stroke h, a pipe section 2a is already cut off from the pipe 2, and the drivable cutting die 6b is brought into a zero stroke position for a subsequent cut. In the zero stroke position both servomotors 12, 13 rotate with the same rotational speed. Then a speed differential is set, so that the angular position of the two servomotors 12, 13 relative to one another changes. A predetermined speed differential can be set, which is maintained. The stroke h varies on the basis of the speed differential and the cutting dies 6a, 6b cut off a section from the pipe 2. The pipe 2 is then advanced some way in the pushing direction V, so that the cut-off pipe section 2a falls off and the subsequent cutting operation can be carried out.

LIST OF REFERENCES

[0068] 1 cutting device [0069] 2 pipe [0070] 2a pipe section [0071] 3a stationary cutting mandrel [0072] 3b movable cutting mandrel [0073] 4 gap [0074] 6a stationary cutting mandrel [0075] 6b drivable cutting mandrel [0076] 7 drive lever [0077] 7 pin [0078] 8 pivot bearing [0079] 9 axial guide [0080] 11 crank pin [0081] 11 central opening [0082] 12 servomotor [0083] 13 servomotor [0084] 14 inner shaft [0085] 15 first pinion [0086] 16 first drive gear [0087] 17a inner bearing [0088] 17b inner bearing [0089] 18 outer shaft [0090] 19 second drive gear [0091] 21 second pinion [0092] 22 gear with external toothing [0093] 23 crank pin drive [0094] 24 internal toothing [0095] 26 crank pin bearing [0096] 27 outer periphery [0097] 80 housing [0098] eccentricity [0099] h stroke [0100] M1 cutting mandrel central axis [0101] M2 centre line of the inner shaft and the outer shaft [0102] M3 centre line of the crank pin drive [0103] V pushing direction