WO1993013901A1 - An implement for cutting thin-walled pipes of sheet metal, including a rotary cutter head - Google Patents

Abstract

For avoiding problems connected with shortening of stainless sheet metal pipes by cross-out-sawing, rotary cutting machines have already been proposed, by which a number of cutting wheels are forced against and moved along an annular area of the pipe. Such a cutting, however, takes relatively long time and requires much skill. According to the invention a similar principle is used, but with automatic and mutually independent dosing of cutting pressure and force or speed of rotation, respectively, whereby a cross-cutting can be effected rapidly and without special skill. The implement comprises an outer carrier ring (2) provided with clamp jaws (4) for centered holding of a pipe and with a concentrically rotating ring body (24) driven by a motor (28). The ring body (24) has holders (30) for inwardly projecting, spring loaded cutting wheels (34), and actuator means (42, 38) for pivoting the holders (30) for resiliently forcing the cutting wheels against the pipe. By a fast, motor driven rotation of the ring body (24) the cutting wheels will operate at their predetermined and relatively high, resilient pressure against the pipe, whereby a cross-cutting of a desired quality can be effected at a very short time.

Description

AN IMPLBYENT FOR CUTTING THIN-WALLED PIPES OF SHEET METAL, INCLUDING A ROTARY CUITER HEAD.

The present invention relates to an implement for cross-cutting thin-walled pipes, primarily metal pipes made of stainless sheet material. Such stainless plate pipes are used extensively, particularly in drainage systems, and there is a pronounced need, based on the use of standard pipe lengths, for carrying out craftsmanlike adaptations on the mounting sites, particularly simple shortenings or cross-cuttings of the pipes, optionally, in a less simple manner, with an associated constriction working of a cut pipe end, such that this end can be introduced into a sealing socket at the end of a following pipe length. Usually, the cross-cutting is effected By^""sawing and a subsequent filing of the raw-cut pipe edge, but these operations are not quite easy to carry out, as at least the sawing of the thin-walled pipes can be problematic.

There are known some special cross-cutting implements, based on the use of cutter wheels, which, by means of a chain surrounding the pipe, can be forced against the outside of the pipe and turned around the pipe, such that by tightening the chain it is achievable that the cutter wheels both cut through the pipe wall and deform the pipe end into a slight constriction. These implements, however, are rather difficult to operate, and they require a high experience of the operator in order to ensure that a cross-cutting can be effected at a reasonable time without the pipe being damaged by local deformations. In connection with the invention it has been recognized and established that based on the said cutter wheels it is in fact possible to design an effective special implement, which is easy to use and is pre-optimized to be able to effect a cross-cutting at very short time without requiring any special operator experience.

Especially from the litterature various more

SUBSTITUTESHEET developed pipe cutters are known, but they do not apply to thin-walled sheet pipes. Thus, from US-A-3,839,791 it is known to mount about an iron pipe a closable implement comprising a rotatable carrier ring for a holder provided with a cutting tool, which, by a hand or motor driven rotation of the carrier ring, is gradually clamped against the outside of the pipe so as to produce a cross-cutting groove by shaving. Such a technique would be fully useless for cutting thin-walled sheet pipes.

According to DE-OS-22 06 934, it is also known to use a rotary holder for a number of cutting wheels, which, by means of an axially displaceable, conical feed unit can be urged radially inwardly against the pipe, while the pipe is centered by a corresponding inward urging of three radial clamping feet on a rigid pipe portion of the implement. A motor on this rigid portion is operable to rotate the tool head, and by manual activation of the feed unit the pipe may then be cross-cut by the rotating cutting wheels. This, however, has no bearing on thin-walled sheet pipes, but statably only on 'pipe or rod members^*', i.e. at the most on conventional, relatively thin-walled pipes. A test of this implement on a sheet pipe would show that the implement is useless, already because the pipe will be deformed by the pressure from the clamping feet, when subjected to a sufficient clamping force, and besides, the problem as to experienced skill with respect to the dosing of fhe feed pressure still remains.

A further implement which would be correspondingly useless for thin sheet pipes is disclosed in DE-AS-19 19 525.

The implement according to the invention is characterized by the combination of features stated in the characterizing clause of claim 1. After many experiments it has been found decisive that for cutting thin-sheet pipes relative high values for both the speed and the feed pressure of the cutting wheels should be used. This is not so important in connection with the known implements for cutting thin-walled pipes, except for a general desire of effecting the cutting rapidly. It has been found that the thin-sheet pipes give rise to the problem that a cutting speed, which is too slow, will imply a tough working, by which frictional heat will be developed in the pipe material to such an extent that the material changes character and becomes still more difficult to cut by the cutting wheels.

Correspondingly it is required to use a relatively high feed pressure on the cutting wheels in order to complete the cutting before the temperature rises substantially. With the implement of the invention a correct feed pressure can be ensured by the action of the spring means of the tool holders, such that the operator shall not at all worry about producing any correct pressure. With the use of the high cutting velocity and the high feed pressure it is possible to achieve a relatively very fast cross-cutting, e.g. at only some 5-30 seconds.

With the use of the relatively high cutting pressure it is important that the pipe member be well supported all the way round immediately next to the cutting area, as it would otherwise easily be deformed into a non-circular shape, by which the cutting might be ineffective.

An implement according to the invention may be designed as a heavy duty bench apparatus, but it can also be designed as a light, mobile unit, e.g. for mounting in a vice.

In the following the invention is described in more detail with reference to the drawing, in which

Fig. 1 is a perspective view of an implement according to the invention, Fig. 2 is a perspective view of an insert part for use therein,

Fig. 3 is a plan view of the implement, Fig. 4 is a similar view, seen from the other side, Fig. 5 is a fractional view of Fig. 4, and Fig. 6 is a sectional view of the central area of the implement.

The implement shown comprises an annular housing 2 having a central opening, in which there is located a pair of opposed, substantially half-cylindrical clamp jaws 4, which, through outer rib portions 6, are pivotably secured to the housing by means of lower shaft pins 8. At the top the clamp jaws are mutually connected by means of a lever system 10 including a handle member 12, by means of which the upper ends of the clamp jaws can be drawn together for the clamping of a pipe to be cross-cut. The housing 2 may be rigidly held by a chassis, or it may have a lower flange 14 for fixture in a vice.

For adaptation to pipes of different diameters the implement may comprise different insert units, preferably designed as shown in Fig. 2. The unit shown is a plastic cylinder 16, which is axially split at 18 and shaped with an annular row of outer, axially extending throughpassages 20, from each of which a flat slit 22 extends inwardly to the inner side of the cylinder. This unit can be inserted between the clamp jaws and be deformed for closing or almost closing the split 18 when the clamp jaws are forced together, such that a safe fixation of a correspondingly narrower pipe in the implement can be achieved.

In Fig. 3 the cylinder unit 16 is shown in its inserted position, and it is indicated by an arrow that the handle 12 can be swung out for forcing the clamp jaws together.

Fig..4 shows the opposite side of the implement, where only an outermost annular portion of the housing is visible. Inside this portion is mounted a rotatable disc 24 having a central opening 26, the diameter of which is only slightly larger than the inner diameter of the closed clamp jaws 4. In a manner not shown, the disc carries a toothing on its rear side or on an associated hub portion, such that it can be rotated by means of a motor 28.

The disc 24 serves as a carrier for three cutting wheel holders 30, which are pivotally mounted on respective shaft bolts 32 and each carrying an inwardly exposed cutting wheel 34. Outermost, these holders are in hole-and-pin connection 36 with a rotatable actuator ring 38 that is mounted in a concentric groove in the disc 24, such that a limited rotation of this ring body relative to the disc 24 will cause the holders 30 to pivot about their respective shaft bolts 32. Thus, when the ring 38 is rotated clockwise the holders will be pivoted in such a manner that the cutting wheels 34 are moved inwardly towards the center of the holding opening of the implement.

For effecting a relative rotation of the ring 38 there is provided a handle 42, which is pivotally mounted on a shaft pin 40 on the disc 24 and, by means of an eccentric 44, cooperates with a recess in a plate member 46 rigidly associated with the ring 38. When the handle 42 is swung inwardly, towards the right, the ring 38 will hereby be rotated clockwise and thus cause the holders 30 to be swung in the same direction, inwardly, the handle being swung inwardly so far that it can be parked in an active position inside the periphery of the disc 24. The disc and therewith the handle may then be rotated without the handle meeting obstructions or cause any damage to the close surroundings.

By the inward pivoting of the holders 30 the cutting wheels 34 are brought from an outer passive position, outside the periphery of the pipe holding opening of the implement, i.e. a position in which the cutting wheels will not obstruct a completely free introduction of the pipe to be cut, to a position in which the cutting wheels are located so far inside that periphery as required for the wheels to cut through the pipe wall during the following operational phase.

The cutting wheels 34 are connected with the holders 30 in such a manner that relative to the holders they may yield resiliently outwardly, namely in being mounted in carrier elements 46, which, by spring means not shown, are urged inwardly relative to the controlably shiftable base portions of the holders 30. Thus, upon a pipe being mounted and clamped in the implement a tightening actuation of the handle 42 will cause the cutting wheels 34 to be moved into engagement with the outside of the pipe and thereafter to be biased thereagainst with an increasing pressure. The system is so adapted that a considerable pressure between the cutting wheels and the pipe is built up, yet without the pipe wall being deformed thereby.

Thereafter the motor 28 is started for rotating the disc with its associated cutting wheels. Hereby these wheels will work the pipe without shaving and very quickly effect a cross-cutting of the pipe wall, the wheels being currently fed by means of the said spring force.

The said pivoting of the wheel holders 30 is illustrated in Fig. 5, where the holder is shown by dot-and-dash lines in its swung-out position, while it it shoen in full lines in an operative position during or after cutting through the pipe wall.

During their rotation the cutting wheels 34 will exert a considerable pressure against the pipe wall, and as shown in Fig. 6 this will or may result in the end of the shortened pipe 50 being slightly chamfered as shown at 52, this being highly desirable in case the pipe end hould afterwards be insertion connected with a corresponding pipe socket having a built-in sealing ring.

Obviously, the holders 30 cannot assume the same initial and final positions regardless of the pipe diameter, and with the use of more or less thick-walled inserts 16, or no such insert, respectively, the holders should, therefore, be suitably adjustable. By way of example, this is achievable by the disc 24 having alternative possibilities for the pivotal fastening of of the holders 30, or alternave possibilities for the starting position of the ring 38 relative the feeding mechanism 42,44, such that the implement, if desired, is easy to adjust for cutting pipes of different diameters.

For the invention it has been found quite important and not only generally desirable that the cross-cutting is effected rather rapidly, i.e. with the use of a high pressure between the cutting wheels and the pipe and a relatively high moving velocity of the cutting wheels, inasfar as an attempted cutting with a low cutting pressure and/or a low velocity will easily give rise to a heat development in the cutting area, such heat having a hardening effect on the pipe material and thus making a throughcutting difficult altogether.

It will be a possibility that the cutting wheels, with the use of suitable control means, are actuated subsequent to the motor being started, such that they will initiate the cutting with a flying start. Hereby it will be avoided that these wheels are forced against the pipe while they stand still, and there is reason to believe that this will make the cutting wheels more durable.

Compared to e.g. thread cutting, rotating tools, the rotational speed should be considerably higher, e.g. of the magnitude 150 rpm. If it is desired to make use of approximately the same cutting velocity for pipes of different diameters, e.g. in the interval 50-160 mm, the speed of rotation should be adjustable, but it has been found that middle sized pipes, 110 mm, can be effectively worked within a speed interval of 100-200 rpm, and a suitable standard speed, therefore, may be 150 revolutions per minute.

For the achievement of a rapid cross-cutting and a suitable chamfering of 1-2 mm, the cutting wheels should exert a reasonably high feeding pressure, e.g 1000-13000 N for a 50 mm pipe, rising to 1200-1500 N for a 160 mm pipe. It has been found possible to cut a 160 mm pipe with a wall thickness of 1.25 mm in 8-10 seconds.

Claims

C L A I M S :

1. An implement for cross-cutting of pipes, particularly thin-walled sheet pipes of stainless metal, and of the type including an annular carrier member having means for centered fixation of a pipe to be cut and rotatably carrying a tool holder ring provided with cutting tools mounted in tool holders, which, during rotation of the holder ring, are feedable radially inwardly for cutting the pipe, the carrier member having a motor for rotating the tool holder ring, characterized by the combination of - the annular carrier member being provided with clamp jaw means that are tightenable to and arrestable in a position, in which the pipe, either directly or with the use of intermediate annular inserts, is clamped with face-to-face contact substantially all the way round.

- the cutting tools being cutting wheels, preferably arranged in a rotation symmetrical manner and in a number of 2-5,

- the tool holders being spring loaded inwardly, from an outer, arrestable and releasable, passive position to an inner final position corresponding to the cross-cutting being concluded, with sufficient spring effect to carry out the full feeding movement of the tools,

- the motor and the drive system of the tool holder ring being adapted for rotation of this ring with more than 50 revolutions per minute, preferably in the range of 100-200 rpm, and

- the spring force acting on the cutting wheels being at least 500 N and preferably in the range of 1000-2000 N. 2. An implement according to claim 1, in which the tool holder ring is rotated at approximately 150 rpm.

2. An implement according to claim 1, in which the means for arresting and releasing of the cutting wheels include an actuator ring, which is concentrically rotatably arranged in the carrier ring member and is rotatable by means of an actuator handle, this actuator ring further being coupled to each of the cutting wheels or each of the cutting wheel holders, respectively, such that these are concurrently shiftable by means of the actuator ring.

4. An implement according to claim 1 and further comprising one or more lining insert members suited to be clamped between the clamping jaw means for centered clamping of pipes of reduced diameters.

5. An implement according to claim 4, in which the tool holders with associated spring means are arranged in such a shiftable manner that they are mountable for active cooperation with pipes of two or more different diameters.