GB2120591A

GB2120591A - Mechanism for parting-off continuously advancing pipe

Info

Publication number: GB2120591A
Application number: GB08313999A
Authority: GB
Inventors: Rolf Gurr
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-05-22
Filing date: 1983-05-20
Publication date: 1983-12-07
Also published as: GB8313999D0; DE3219358C2; GB2120591B; DE3219358A1

Abstract

A mechanism for parting-off pipe 1, preferably of plastics material and advancing continuously from an extruder, comprises tools which effect the cutting-off and also the chamfering and advance with the pipe. The tools are carried by a rotor 19 driven from a motor 20 so as to be carried around the pipe, the rotor being mounted on a carriage 7 which can be secured to the moving pipe by a clamp 11, 14 and is guided along guides 15, 17 on the frame. The tools are operated so that a first tool cuts a groove in the pipe and a second tool then effects a parting-off of the pipe. <IMAGE>

Description

SPECIFICATION Mechanism for parting-off continuously advancing pipe The invention refers to a mechanism for parting-off pipe, preferably of plastics material, and advancing continuously from an extruder, by tools which effect the cutting-off and also the chamfering of it and advance with the pipe in a carriage and are moved round the pipe.

In the case of the production of plastics pipe by extruders, it has proved to be essential to work continuously at the same feed, in order to keep constant within close tolerances the dimensions of the pipe produced. For the storage and transport of the extruded pipe, it is necessary to divide it up into sections. In doing this, it is, in general, desirable that at least one of the two end faces of such a section of pipe be chamfered. The use of ordinary flying shears or parting saws is forbidden in the interest of the preservation of the predetermined cross-section of the pipe, as well as smooth faces of chamfer and separation. Rotary mechanisms constructed in accordance with the species are, therefore, widely used, in which a tool, which effects both the cutting-off and also the chamfering, gets carried round the region of separation of the advancing pipe.But, it has been found that the quality of end faces and chamfers created in that way leaves much to be desired and turns out partly although slightly wavy.

The invention, therefore, results from the problem of creating a mechanism of the species designated which, with relatively low mechanical effort and consumption of time, delivers smooth end faces lying normal to the axis of the pipe and smooth coaxial chamfered faces like the convex surface of a cone.

According to the present invention, a mechanism for parting-off an end portion of a pipe moving continuously in the direction of its length comprises a carriage movable along a track extending in the direction of movement of the pipe, means for driving the carriage along the track at the same speed as the movement of the pipe, a rotor surrounding the pipe and rotatably mounted on the carriage, means for rotating the rotor, a chamfering tool and a parting tool carried by the rotor and each movable radially towards and away from the longitudinal axis of the pipe, and means for moving the chamfering tool inwards to form a peripheral groove in the pipe and thereafter to move the parting tool inwards into the groove to part the pipe.

It is hereby achieved that the chamfering tool which, shortly before the finishing of the chamfered face is bringing about a relatively wide area of cut, is being engaged against the still unseparated pipe which, in the region of the chamfer which is to be produced, has indeed already been necked down but not yet essentially reduced in its rigidity. The still undivided pipe, therefore, proves itself rigid and, in practice, does not become deformed by the cutting forces, so that smooth running of the chamfering tool is achieved. Only after withdrawal of the latter, and with a relatively short length of the cutting edge and thereby low forces applied radially, does the pipe get completely parted.The execution of the severing in accordance with the invention, therefore, causes only slight elastic deformations of the pipe which is to be severed and, because of the accordingly definite guidance of the tool, clean faces of separation.

The engaging of the tools is brought about controllably in the desired sense, because the rotor has a sliding collar which surrounds it and can be shifted axially by a pressure ring and which, during its advance, actuates the means of engagement. In this case, it has proved useful to couple the sliding collar via a link to a two-armed setting-lever which, by means of a swivelling cam prestressed against a stop, feeds a radially guided toolholder towards the pipe and, after a predetermined length of stroke, slides off its setting-face so that the toolholder can be returned into its normal position by a tension spring associated with it and the swivelling cam, swinging back during the return of the settinglever, is able to pass by the stopface.A like relatively simple mechanical solution for the preservation of the predetermined speeds follows for the cutting-off tool by the sliding collar being equipped with a slotted lever, the operative slot in which, embracing a stopface of the toolholder, approaches the parting-tool to the pipe during the activity of the chamfering tool and, after the withdrawal of the chamfering tool, pushes the cutting-off tool through the wall of the pipe which is to be cut-off. The application of these measures allows the sequence control of the feed of the tools in one operational movement and through a single driving mechanism effecting the feed of both tools.

It has proved extraordinarily conducive to a clean chamfered face to advance the chamfering tool slower with increasing depth of engagement and, after completion of the stroke provided for, to withdraw it quickly. The formation of a clean face is, moreover, secured by facilitation of the removal of the chips, which is obtained by at least the chamfering tool being advanced intermittently within the range at the end of its stroke. This can be achieved by the thrust cylinder, which effects the feed, being acted upon intermittently at least within the range at the end of the advance of the chamfering tool. The cutting conditions, and thereby the cut faces formed, can be further improved by damping cylinders being associated with the tools and the sliding collar.In the case of the coupling on to the sliding collar, it has proved useful to couple the damping cylinder via an elongated hole in a slotted link so that the damping becomes effective at any time only after the stroke has made some progress. A clean guidance of the pipe and of the separated section is achieved by the carriage equipped with a travelling drive being able to be connected to the pipe at both ends by means of coupling cheeks.

For the chamfering tool, lathe tools and also milling cutters have stood the test, and the parting-off may be performed by a parting-off tool but, fur suitable materials and wall thicknesses of the pipe, a roller knife may be used.

In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which:~ Figure 1 is a side elevation of a mechanism for parting sections of pipe, and Figure 2 is a section through the rotor shown as a detail with the front plate, sliding bush and the tools.

In Figure 1, a plastics pipe, shown cut away at both ends, has just been extruded from an extruder (not shown) and is advancing at constant speed in the direction of the arrow. The pipe is guided through a frame 4, formed of struts 2 and crossbars 3. The frame is equipped with tracks 5, upon which a carriage 7 is guided by means of rollers 6. The carriage is provided with a drive mechanism, in the form of a piston-cylinder 8, which is hinged at one end by means of a support bracket on to the carriage 7, and its piston rod is connected to an extension arm 9 from the frame 4.

At its right-hand side, the carriage 7 is provided with two parallel plates 10 which are connected together by parts of spars 1 5, 16 and 1 7, as well as a cheek holder 11. In the cheek holder 11, a cheek insert 12 may be inserted, which forms a lower fixed clamping plate adapted to the outer diameter of the pipe 1. The plates 10 are, moreover, bridged across by two brackets in which a clamping cylinder 13 is suspended which enables a main cheek 14 to be engaged against the cheek insert 12.

At the left-hand end of the carriage 7, two further plates 18 are shown which are likewise connected by the spars 1 5, 1 6 and 17, and which are provided with the bearings of a rotor 19, which is supported to rotate in the bearings, and which is driven via V-belts 21 from a motor 20 arranged on the top of the carriage. At its free right-hand end, the rotor 19, as shown also in Figure 2, is closed off by a front plate 22 and it is surrounded by a sliding collar 23 upon which a pressure ring 24 is supported in a bearing. Trunnions on the ring 24 are embraced by a fork lever 25. The pivot of the fork lever is supported on the spars 16 and two lever arms extend upward in a fork and embrace the sliding collar 24 as well as a further lever arm leading downwards. The latter is connected via a link and a bell crank 26 to the piston of a hydraulic thrust cylinder 27.Connected in parallel with this linkage, there is a damping cylinder 28 which engages in the elongated hole 29 in a slotted link connected to the bell crank 26.

A second clamping mechanism is connected to one of the plates 18; a clamping cylinder 30 advances a chuck 31 in the direction towards the pipe 1 which is to be clamped and which is gripped from below by a cheek insert 12.

As shown in particular in Figure 2, the front disc 22, revolving with the rotor 19, is equipped with two guide brackets 32 in which a toolholder 33 is guided to be able to shift radially. A chamfering tool 35 is shown in the extreme upper position in which its chuck 34 serves as the stop at the bottom end of the guide brackets 32. The toolholder is prestressed into this extreme position by a tension spring 36 which is effective between the top end of the guide brackets 32 and the chuck 34 and in parallel with which a damping cylinder 37 is arranged for damping movement.

The sliding collar 23 is connected by means of a link 38, having an adjustable turnbuckle, to one arm of a setting-lever 39 formed as a two-armed bell crank. A pair of arms of the crank project towards the right like a fork and are equipped with a hinged swivelling cam 40 which is prestressed by a torque spring 41. In the position as illustrated, in abutment anticlockwise, the swivelling cams 40 overlap rollers 43 provided on a pin 42 on the toolholder. The chuck 34 of the toolholder 33 is equipped against twisting with a straight face which slides along a protection 44, and the tool itself exhibits a free end opened like a fork through which engages the pin 42. At the end, shown as the bottom in Figure 2, the front disc 22 is equipped likewise with two guide brackets 45 which hold a toolholder 46 for cutting-off tool 47 to be able to shift radially.This, too, is traversed by a pin 48 which exhibits rollers 49 at both ends, and the chuck 54 of the toolholder 46, holding the cutting-off tool 47, rests with a flat face against a protection 50. The sliding collar 23 in the region of this toolholder is connected to a curved slotted lever 51 which passes through the front disc 22, the free end of which is bifurcated and embraces the toolholder 46 on opposite sides. In this way, the rollers 49 engage, respectively, in operative slots 52 in the two lever arms of the slotted lever 51. Also, there is arranged between the chuck 54 and one of the guide brackets 45 a damping cylinder 53.

In operation, the carriage 7 is shifted by means of the travelling cylinder 8 towards the right along the track 5 on the frame 4, that is, in the opposite direction to the pipe 1 which is being fed in the direction of the arrow. The pipe 1 passes between the cheek inserts 12, through the plane of separation 55, through the rotor, and beneath the chuck 31.

When the pipe has advanced by a predetermined length beyond the plane of separation 55 arranged in front of the front disc 22, the clamping cylinders 13 and 30 are activated and the pipe 1 is thereby clamped firmly on opposite sides of the plane of separation 55. In doing this, the chuck associated with the clamping cylinder 13 is actuated with relatively high contact pressure and the chuck is adapted to the outer diameter of the pipe 1 by cheek inserts laid in the cheek holder 11 and the main cheek 14.But, in the case of the chuck 31, only fairly small force is applied and an adaptation to the outer diameter of the pipe is indeed performed in the lower cheek by a cheek insert 12, but the chuck 31 rests upon only a relatively narrow section of the surface, being adapted to the largest diameter of pipe which is to be handled and, because of the relatively small area of the piston of the clamping cylinder 30, is also acted upon with a smaller force than the main cheek 14. The carriage 7 is now connected to the pipe and is, therefore, advanced with the latter, and, by appropriate loading of the travelling cylinder 8 with compressed air, the pipe is almost completely relieved of the longitudinal forces which normally arise.

Whilst the carriage 7 now runs forward along its track 5, the pneumatically operated thrust cylinder 27 is actuated. The first part of the range of its stroke runs undamped but, after traversing the elongated hole 29, the damping cylinder 28 becomes effective and brings about a constant speed of advance. During the course of the stroke of the thrust cylinder 27, the fork-lever 25 is pivoted anticlockwise; in doing this, it draws the pressure ring 24 towards the left and with it the sliding collar 23. As shown in Figure 2, the sliding collar, via the link 38, carries along with it the setting-lever 39 which pivots the swivelling cam 40 against the roller 43 and thereby, during the running of the rotor 19 and the front disc 22 connected to it, forces the toolholder 33 inwards against the force of the tension spring 36.In this way, the chamfering tool 35 is forced against the pipe and starts first of all to turn a chamfer in the form of a groove at the point of separation which is to be produced. The adjustment is, in this case, carried out in such a way that, upon reaching the predetermined chamfer, the swivelling cam 40 passes by the roller 43 and thereby releases the toolholder which, both under the action of the centrifugal forces and also the tension spring 36, slides back into its normal position shown in the drawing, until its chuck 34 rests against the bottom of the guide brackets 32. The movements arising in this way are damped by a damping cylinder 37 acting in parallel with the tension spring 36.Through the mechanical drive described, the feed is effected first of all relatively rapdily and then, with increasing approach to the chamfer which is to be produced, it is effected more slowly until, after finishing, a rapid return begins. It has proved useful to act upon the thrust cylinder 27 intermittently by, for example, a valve arranged in the supply to it so that the feed, at least in the range of finishing the chamfer, is effected intermittently; by this means, the removal of the chips is favoured and, at the same time, correct, smooth and strictly conical groove is achieved.

Upon further insertion of the piston of the thrust cylinder 27, and thereby withdrawal of the sliding collar 23 from the front plate 22, the swivelling cam is swung further away from engagement with the roller 43. Already during the operation of the chamfering tool 35, the slotted lever 51 was also being shifted towards the left by the sliding collar 23 to which it is connected. In doing this, the rollers 49 on the toolholder 46, engaging through the operative slots 52 in the slotted lever 51, were being shifted towards the axis of rotation of the mechanism without the cutting-off tool 47 becoming effective. During further advance, the curve of the slotted lever 42 now steepens and the cutting-off tool passes into the groove and cuts through the wall of the pipe 1 so that severance of the wall of the pipe is effected.Here too, the operation may be carried out, if necessary, with an intermittent feed in order to achieve better removal of the plastics chips. The risk of the tool running-off through oscillation of the ends of the pipe no longer exists, since the area of attack of the cutting-off tool is essentially smaller than that of the side chamfering tool.

After completion of the severing, the thrust cylinder 27 is acted upon in the opposite direction and the cutting-off tool 47 is withdrawn radially outwards by the slotted lever 52. At the same time, the setting-lever 39 is swung back into its normal position. In doing this, the swivelling cam 40 folds down so that it arrives back in the normal position illustrated in the drawing effortlessly and without exerting on the toolholder 33 any significant forces. In parallel with this, the pistons of the clamping cylinders 13 and 30 are withdrawn so that the chucks open and the pipe, as well as the severed section of pipe, are released. The latter may be removed from the mechanism and, at the same time, the drive 8 withdraws the carriage 7 back towards the right into its starting position. Thus, cyclic working is achieved without affecting the speed of extrusion of the pipe 1.

The mechanism is capable of a number of variants. Thus, for example, the compressed air cylinders may be replaced by hydraulic cylinders.

But, in this case, a pressure storage would advantageously be associated with the travelling cylinder ain order to enable adaptation to the speed of advance of the pipe 1 without longitudinal forces loading the pipe.

A direct, for example, hydraulic drive of the toolholders is also possible, but a relatively costly sequence control would be necessary in order first of all to act upon the chamfering tool at a speed which decreases with increasing stroke and to advance the cutting-off tool only after withdrawal of the chamfering tool, and also the feeding of pressure medium to the rotating front plate would cause difficulties. It has, however, proved advantageous, where the wall thickness and the material of the pipe which is to be severed allow it, to use roller knives instead of a cutting-off tool.

These may, in case of need, be provided with a quick-change mounting so that the replacement of roller knives which are worn and damaged may be effected in a very short time and practically without stoppage. Instead of the tool, an appropriately designed mounting is then employed which is equipped with an oblique slot for receiving the spindle of the knife roller. Fixing may be effected by pressure screws introduced against the spindle in the end position, and the spindle may be secured against axial shifting by its being introduced by grooves into the slots adapted to the diameter of groove. Again, the suspension of the carriage in the frame may be effected in a manner which is reliable and capable of heavy loading by means of ball guides. In all of these cases, a mechanism is created which works reliably and can be produced with relatively small outlay and which allows within short cycle times both clean separating cuts and also accurate chamfering.

Claims

1. A mechanism for parting-off an end portion of a pipe moving continuously in the direction of its length comprising a carriage movable along a track extending in the direction of movement of the pipe, means for driving the carriage along the track at the same speed as the movement of the pipe, a rotor surrounding the pipe and rotatably mounted on the carriage, means for rotating the rotor, a chamfering tool and a parting tool carried by the rotor and each movable radially towards and away from the longitudinal axis of the pipe, and means for moving the chamfering tool inwards to form a peripheral groove in the pipe and thereafter to move the parting tool inwards into the groove to part the pipe.

2. A mechanism as claimed in claim 1, in which means are provided for releasably connecting the pipe to the carriage at two positions on opposite sides of the position at which parting takes place.

3. A mechanism as claimed in claim 1 or 2, in which the rotor has a sliding collar which can be shifted axially by a pressure ring and which, during its advance, actuates the means for moving the chamfering tool and the parting tool.

4. A mechanism as claimed in claim 3, in which the sliding collar is coupled to a lever which acts against the chamfering tool by way of a hinged swivelling cam arranged such that movement of the sliding collar causes the chamfering tool to be moved inwards into engagement with the pipe, and further movement of the collar causes the connection by way of the swivelling cam to be broken, to allow the chamfering tool to be rapidly withdrawn away from the pipe by the action of a spring.

5. A mechanism as claimed in claim 3 or 4, in which the sliding collar is provided with a slotted lever which receives part of a holder for the parting tool and which is arranged such that, after the operation of the chamfering tool, further movement of the sliding collar causes the parting tool to be moved inwardly to part the pipe.

6. A mechanism as claimed in any preceding claim, in which the chamfering tool is moved inwardly towards the pipe with a decreasing speed as the depth of engagement of the chamfering tool with the pipe increases and, after completion of the chamfering operation, the tool is rapidly withdrawn.

7. A mechanism as claimed in claim 6, in which the chamfering tool is advanced intermittently as it engages with the pipe.

8. A mechanism as claimed in claim 7, wherein a thrust cylinder is employed to bring about movement of the sliding collar and the thrust cylinder is acted upon intermittently at least over that part of its range which brings about the advance of the chamfering tool.

9. A mechanism as claimed in any preceding claim in which each of the tools has a damping cylinder associated therewith.

10. A mechanism as claimed in any one of the claims 2 to 9, in which the sliding collar has a damping cylinder associated therewith.

11. A mechanism as claimed in claim 10, in which the damping cylinder is coupled to the sliding collar by means including an elongated hole in a slotted link so that the damping cylinder is only operative for part of the range of movement of the sliding collar.

12. A mechanism as claimed in claim 2, in which fluid operated devices serve to couple the carriage to the pipe.

13. A mechanism for parting-off an end portion of a pipe moving continuously in the direction of its length substantially as hereinbefore described with reference to the accompanying drawings.