GB2024690A - Method and apparatus for perforating tubes - Google Patents

Abstract

A method for the punching of holes in a wall of a tube is disclosed in which holes lying substantially opposite each other on the tube are punched using an apertured mandrel 34, 34 positioned inside the hollow body, the punching strokes to produce the opposite punched holes are directed into the interior of the rod-shaped hollow bodies in counter directions, and the mandrel is shaped to shed waste pieces produced by the punching strokes. Apparatus for carrying out this method is disclosed in which drive of the punch press takes place by way of a doubly operating hydromechanical toggle lever system and the tool supports are moved in a counter-directional manner with the punches 44 of the punching tools acting upon the mandrel 34, 35 disposed inside the tubes to be punched, retaining rods of the mandrel being mounted in a displaceable manner on a stationary bearing block. <IMAGE>

Description

SPECIFICATION Method and apparatus for the continuous punching of holes in rod-shaped hollow bodies The invention relates to a method and apparatus for the continuous punching of holes in the wall of rod-shaped hollow bodies of any cross-section, in which the punched holes essentially lying opposite each other on the rod-shaped hollow body are punched in one operation by using a matrix positioned inside the hollow body.

Rod-shaped hollow bodies made of the most varying metals with systemised punched holes are required in great quantities, whereby the holes disposed along an axis-parallel surface line can be alike or unlike and in part can be very narrowly spaced. In this connection it is a question of producing clean holes and the fact that narrow distance tolerances and total tolerances can be adhered to.

A punching apparatus is known for punching relatively short hollow bodies, in which the punching takes place in one single downstroke by means of the punches arranged in longitudinal axis in a spaced manner. The inner core consists of two parts which can be displaced towards each other on an oblique plane in such a manner that the inner core fills up the interior of the tube in the punching direction (German Offenlegungsschrift 2231 517).

Apart from a high expenditure of tools and machinery, this apparatus is limited in the case of double punching only to the processing of short tubes, which must be punched individually one after the other. In addition to this the distances between holes are not available.

A device is known for punching thin-walled, highly precise hollow bodies (French Patent Specification 1 380 849), which is based in practical terms on a "nibbling" of the desired contours of the holes. This takes place by means of a punch, which corresponds to the dimensions of the smallest occurring hole and carries out approximately 1000 strokes/min. A method of this kind is suitable for round, relatively short, seamless precision tubes, which are produced with a plurality of individual holes in small series.

In the German Offenlegungsschrift 20 24620 an apparatus and method is described for punching perforations on tubes of all lengths and shapes, in which the matrix, arranged inside the hollow body and movable within certain limits, is centered and secured in position by means of a guide of the same hole dimension preceding the punches in such a manner that punch and matrix are exactly aligned in terms of axis. Apart from the increased expenditure of tools, the inevitable distance tolerances in the tool are added to a total tolerance corresponding to the number of strokes per workpiece. In addition the distance between the first hole and the beginning of the tube must always be smaller than the distance between the guide and the first punch.

According to the German Offenlegungsschrift 26 32713 the tube to be punched is pushed over a two-part, wedge-shaped matrix inside the hollow body and firstly is moved into an end position by means of a clamping apparatus and the essentially automatic punch operating sequence subsequently takes place. In this the feed of the tube is effected by a feeler which plots the distances of the holes by way of a tooth-like ruler. The matrix is then pressed against the inner wall of the tube by way of a further controlling action, is adjusted by way of collecting pins to the axis of the punch and the workpiece is pushed simultaneously against fixed stops. Only then does the punching take place, and afterthe punches have returned and all the obstructions cleared, the next working stroke can begin.However only one row of holes can be punched with this punching apparatus on one single tube in a continual procedure.

The Austrian Patent Specification 280 739 describes an apparatus for punching long tubes, i.e.

more than 3 m long, in which several tubes can be worked upon simultaneously next to each other in one operational procedure. To this purpose the tubes, fixed to the punch axis by way of retaining rods, are pushed over a matrix which is in one piece.

The matrix is pressed against a lateral inner wall by mechanical, pneumatic or hydraulic means. By means of the power press, the punches, which are guided in the matrix, can also punch at the same time the wall lying opposite the inlet side of the punch. With this the result is that an exact alignment between the inner wall of the tube and the punch is not achieved by pressing the matrix onto the inner wall of the tube. The paths of the punch when passing through the total cross-section are very long and impair the accuracy. A considerable punching ridge forms on the outlet side of the punch. Furthermore there is the danger that the contours of the holes may bulge in the area of the inlet side of the punch because of the requisite gap between matrix and inner wall of the tube.

The object of the invention is to produce a method and apparatus with which double punches can be undertaken reliably with the lowest financial expenditure and in a clean execution in terms of quality, in the case of commercially conventional rod-shaped hollow bodies which are of any cross-section, made of the greatest variety of metals and are very long.

The invention is distinguished by the fact that the punching action of the opposite punched holes take place in the counter direction to the inside of the rod-shaped hollow body and the pieces produced with the punching action inside the rod-shaped hollow bodies are removed.

Good hole images in terms of quality and narrowly tolerated distances of the holes are the result of an operating mode such as this. The precision of the punched holes is also guaranteed in the case of large rod-shaped hollow bodies with relatively thick walls.

The exact and safe operating mode is independent from the size of the workpiece in the case of double punched holes. A quick operating sequence is made possible without impairing thereby the faultless punching procedure. Furthermore hole images can be produced at the same time which have different hole contours and dimensions on their opposite walls and can even be displaced within certain limits in their centre axis.

The counter-directional punching actions can be carried out at the same time on several rod-shaped hollow bodies. Advantageously the working plane of the punching tools in the vertical direction is provided for when the workpieces are positioned next to each other in the horizontal plane. However it is also possible to arrange the working plane of the punching tools in the horizontal plane with the workpieces positioned one above the other in a vertical direction.

Preferably a hydro-mechanical toggle lever system effects the transferrence of force onto the punches working in a counter-directional manner.

The flux of force takes place thereby by way of a hydraulic cylinder, the piston rod of which is connected to the center bearing of a toggle lever and by way of toggle lever fish plates which in turn are hinged to tool supports either directly or by way of connecting links. Inevitable differences in strength between the upper and lower tool supports can be eliminated by means of one or several pressurebalance cylinders which are integrated into the hydraulic system and co-operate with the main hydraulic cylinder. By means of this cinematic chain the press-support as well as the guides and bearings of the moved elements are not in the least stressed by the punching forces.The tool supports, which are moved in a vertical manner and receive the punch supporting plates, can be guided in four columns, so that an exact accuracy of the guide is guaranteed even in the case of asymmetrical strain of the tool.

If very great tool forces are transmitted, as for example are necessary when several thick-walled tubes are being punched simultaneously, it is recommended to provide a two-fold toggle lever system.

Here the tool supports are each hinged in two points.

A double support such as this between hinge and tool support essentially increases the guiding accuracy and stability of the punching device.

A double operating hydromechanical toggle lever system of this kind developed for the implementation of double punches has many advantages. The hydraulic cyclinder is applied during the working stroke in such a way that the punches touch the work pieces gently first of all. Only after that does the necessary punching pressure build up quickly and the cutting procedure begins. The self-centerising of the tools takes place in this stage. With the ending of the cutting procedure the operating piston is already working against an elastic cushion, which serves to slow down the cutting stroke. After this the elastic cushion builds up again quickly with the supply of pressure media and effects the return stroke of the tool supports.

The punching stroke of both tool supports according to the invention is very small and in the main constant. However it can easily be varied subject to the dimensions of the workpiece and thicknesses of material by limiting the path of the operating piston.

Generally it is set at two to four- times the thickness of the material to be punched. The hydraulic pressure and the dimensions of the cylinder can be relatively small in consideration of the essentially greater piston path in comparison with the plunger stroke because of the counter-directional operating principle and the low punching strokes. Extraordinarily favourable cinematic conditions result for the construction of the entire hydraulic system and also of the mechanical pressing parts and as a result of this low capital costs also.

While the distance of the lower tool support to the pressing table remains generally constant, or is only altered within narrow limits, this is adjustable to the upper tool support conforming to the cross-sections shapes to be punched.

According to a further feature of the invention it is provided for that the centre pieces which result with the punching are removed immediately the punched holes have been made by the punching tools. The ejection of the centre pieces preferably takes place in the area of the dead-centre position of the punching tools during the working stroke. The matrix provided inside the hollow body is used for the ejection procedure of the waste pieces. The matrix according to the invention is constructed of several parts for this purpose in the manner that it consists of outer parts and an inner part which are disposed in a wedge-shaped manner to each other and are connected by means of a guide. In this connection the inner part of the multi-sectional matrix takes over the ejection of the waste pieces. The multi-sectional matrix facilitates the raising of the tubes in the disengaged position.In the stretched position the walls of the hollow body are mutually supported so that bulging in the area of the hole contours is excluded. The inner part of the matrix is moved abruptly in axial direction of the hollow body in the releasing procedure in such a manner that the waste pieces are flung out of the matrix.

The two outer parts of the matrix can be fixed to the head of a tubular retaining rod so that they can only move slightly at right angles to the longitudinal axis. The other head of this retaining rod which is smaller in relation to the matrix may be fixed to the outermost fixed point of the entire device, e.g. to a bearing block. Atelescopic inner rod may be disposed inside the outer retaining rod, to the head end of which the inner part of the matrix is securely fixed.

This inner rod can be moved for the clamping procedure in longitudinal direction by way of pneumatic, hydraulic or mechanical clamping elements mounted on the outer bearing block. The sudden releasing procedure can be aided by elastic means, e.g. sets of springs.

The punching tool for the simultaneous punching of several workpieces arranged next to each other can consist of punch supporting plates fixed to the moved toot supports, the three-part matrices arranged on the retaining rods and also of punch guide plates and of lateral workpiece guides constructed if necessary in each case of a rigid and an elastic part, these being arranged together on the pressing table.

A combination of essential advantages is achieved by the combined operation of the described mechanism of the apparatus. The opposite walls of the rod-shaped hollow cylinder can be punched simultaneously and with a very clean cut by means of the punching tools working in a counter-directional manner. The slight lengths of the strokes cause a very high number of strokes and correspond to great punching velocity. The hydro-mechanical toggle lever system effects the self-centering of the matrix by the gentle cutting of the walls and leads to a complete release of the pressing body from the punching forces and also to excellent conditions of measurement by way of a favourable cinematic course of forces.Formation of a ridge and dropping in the outer area of the hole contours is prevented by the counter-directionally operating punches in con junction with the formation of the matrix according to the invention. The formation of the matrix allows a longer punching time. The waste pieces are sure to be ejected. Furthermore the total arrangement allows the simultaneous punching of several, very long hollow bodies of any cross-section with rela tively great cross-sectional tolerances.

The invention is explained as follows in conjunc tion with the exemplary embodiment represented in the drawing.

Figure 1 shows schematically the complete arrangement of the invention in front elevation.

Figure 2 shows the arrangement schematically in top view.

Figure 3 shows the hydro-mechanical toggle lever system in schematic representation in front eleva tion.

Figure 4 shows the system of Figure 3 in side view.

Figure 5 shows a tube punched on two sides in perspective representation.

Figure 6 shows schematically a multi-sectional matrix according to the invention for punching a rod-shaped hollow body in conjunction with the punching tools.

Figure 7 shows a section corresponding to the line VII-VII of Figure 6.

Figure 8 shows a section corresponding to the line VIII-VIII of Figure 6.

Figure 9 shows a section corresponding to the line IX-IX of Figure 6.

Figure 10 shows a structure of the supporting arrangement for the inner and outer rods of the matrices in top view and schematically.

The apparatus for the continuous punching of holes in a wall of rod-shaped hollow bodies 1, e.g.

square tubes, many-sided tubes, round tubes and similar, has a power press 2, a feed sliding carriage 3 driven by a mandrel 13 with clamping apparatus 4 for the workpiece, a bench 5 with a bearing block 6 at the end of this, adjustable workpiece holders 7, a hydraulic control unit 8, an outlet roller bed 9 and a control desk 10 with control mechanism (not shown).

The tubular workpieces 1 are pushed over an inner matrix 11,which is fixed to retaining rods 12. After the workpieces have been clamped by the pneuma tic, hydraulic or mechanical clamping device 4, the feed slide carriage 3 is pushed into a starting position by the mandrel drive 13 or similar, this position corresponding to the distance of the first punched hole to the head ends of the hollow bodies 1.

The power press 2 has a hydro-mechanical toggle lever system which is arranged preferably in the lower part of the press housing. In the toggle lever system (Figure 3 and 4) a hydraulic cylinder 15 is provided in which an operating piston 32 may be moved to an fro, to which a piston rod 14 is connected. The piston rod 14 of the hydraulic cylinder 15 is guided in a bearing and if necessary in a second bearing 17, which are arranged in the press body 18. The two pairs of toggle levers 19 and 20 are hinged to the piston rod 14 by way of a crosstraverse 21 in the point of rotation 22. The upper toggle lever fish plates 23 are flanged directly or by way of an adjusting element to the lower tool support 24.In comparison the lower toggle lever fish plates 25 act upon the upper tool support 30 by way of a plate 26 and an upper plate 28 connected to this by way of guide rods 27 and also an adjusting device 29.

The upper and lower tool supports are guided in the four columns 31 which are securely connected to the press body 18 and in which in turn the guide rods 27 slide. The distance of the two tool supports to each other can be varied by way of the adjusting device 29 in accordance with the dimensions of the work pieces to be punched when the stroke remains the same.

In the case of the working stroke corresponding to the horizontal direction of the arrow, the operating piston 32 is applied in such a manner that the punches fixed to the tool supports 24 and 30 by way of supporting plates touch gently on the workpieces and effect a self-centering of the matrices 11 by a slow cutting action.

When the punching procedure is ending, an elastic-hydraulic cushion 33 achieves a slowingdown of the cutting stroke, this cushion effecting the return motion of the punch by additional supply of pressure agent when the dead-centre position is reached.

In order to balance out inevitable differences in cutting power between the upper and lower tool supports, integrated pressure-balance cylinders 63 are to be provided in the hydraulic system of the power press, which are arranged advantageously between the lower tool support 24 and the pressing table 64.

In Figure 5 a rectangular hollow body is represented in perspective as example of workpieces to be punched with a great height in relation to the width and a complicated double punching on two walls lying opposite each other.

The matrix 11 represented in detail in Figures 6 to 9 serves to punch a rod-shaped hollow body. The matrix consists of two outer parts 34 and an inner part 35, whereby these parts are disposed towards each other in a wedge-shaped manner. According to section IX-IX the separating line has a dove-tail guide 36 in the area of the head. In this way the three parts are guided in an exactly aligned manner. The two outer parts 34 are connected by way of tightlyfitting screws 37, spacers 38 and a flange 39 to the outer retaining rods 12.

The flange 39 has slits 40, so that the two outer parts 34 can move vertically to the longitudinal axis during the clamping and the releasing procedure.

Compared with this, the inner matrix part 35 is rigidly connected to an inner retaining rod 42 by way of a screw connection 41. The inner retaining rod 42 slides telescopically in the tubular outer retaining rod 12 and can be safeguarded against buckling by means of the spacers 43 arranged in a spaced manner.

During the clamping procedure the inner matrix part 35 is moved in the direction of the longitudinal axis. In this way the two outer matrix parts 34 are forced apart and position themselves firmly against the inner wall of the hollow body 1. In this way bulging during the punching action is excluded.

The punching tools 44 penetrating the rod-shaped hollow body and formed as punches firstly effect a self-centering of the matrix 11 in the horizontal plane with the cutting of the wall of the hollow body. The waste punched pieces 45 occurring after the wall has been cut through can either detach themselves directly from the upper punch or remain adhered to this. If they fall off the wedge 46 on the inner matrix part 35 prevents them from being able to enter into the lower matrix, from possibly jamming and thereby from hindering the ejection in the longitudinal direction. Corresponding stripping edges 47 are provided inside the openings of the matrix in order to facilitate the shedding of the punched pieces 45 from the punches 44.The waste-punched pieces 45 from the lower matrix part and if applicable also from the upper one - in as far as they do not fall free are flung out of the matrix by the abruptly occurring releasing procedure by means of the ejection edges 48.

The edges 49 on the output side of the matrix in the area lying opposite the edges 48 are rounded in order to facilitate this procedure and to ensure the efficient removal of the pieces. Furthermore a further edge 50 prevents the punched pieces from falling back into the lower matrix opening.

In addition the releasing procedure and with this the ejection of the pieces is effected by way of the control in such a manner that it takes place if possible when the final position of the punch is reached. In order to be certain to exclude the punching operation from being hindered by the pieces, a covering spring 65 is provided in addition to the wedge 46 and has dimensions such that the punched holes next to the matrix and within the lower punch-guide plate are always covered.

In order to keep the lower matrix opening in particular free also from punch friction, fine chips and similar and to further facilitate the ejection of the pieces, a compressed airflow can be directed onto the lower matrix 44 during the releasing procedure.

To this purpose an air-cushion is situated inside the tubular outer retaining rod 12. During the releasing procedure an air flow is supplied to the lower matrix by means of the guiding edge 51 by way of an annularT-slot 52, and inner bore 53 of the retaining rod 42 and a channel 54 and is blocked again by way of the guiding edge 51.

The inner and outer matrix retaining rods are fastened to a bearing block 6 which is disposed on the outermost end of the bench 5. Figure 10 shows a section out of this bearing block.

The outer matrix retaining rods 12 have a fine thread 12a on their head end by means of which the exact alignment of the outer matrix parts 34 to the axis of the punch takes place by way of nuts 55 and counter nuts 56. The inner matrix retaining rods 42 are fixed in a movable manner on the crosstransverse 57. Springs 59 are provided between this cross-tranverse and the heads 58 of the matrix rods 42 which effect a balance of the tension in respect of tool and workpiece tolerances. The clamping procedure can take place by means of a pneumatic, hydraulic or electrical clamping arrangement (not shown) by way of a bolt 60.

During the clamping procedure an elastic buffer, e.g. a set of cup springs 61 is stressed at the same time. In the relaxation this elastic buffer, supported by the springs 59 and if necessary by the clamping arrangement, works in the return movement on the cross-traverse 57, which in turn releases the abrupt longitudinal movement of he inner matrix part 35 by way of attachments 62 for the ejection of the punch pieces.

The operational sequence of the punching apparatus takes place as follows: After the rod-shaped hollow bodies 1 are pushed onto the matrices 11 and are fixed to the feed sliding carriage 3 and the latter is in its starting position, the automatic operation begins. First of all the feed sliding carriage 3 moves into punching position.

With the beginning of the punching operation the stressing of the matrix takes place at the same time as the self-centering. The upper punches are to precede slightly the lower ones in the punching and return strokes. In this way it is guaranteed that the workpieces are always lying securely on their base and do not jump. When the dead-centre position of the lower punches is reached, the matrices are released and the waste-punch pieces are thrown abruptly out of the matrix preferably from the middle part. After this the return stroke of the punches to the starting position takes place and the next working stroke begins.

Feeding of the workpieces in the respective punching position can take place automatically with known means also with the most varied hole distances within a systemised punching of holes in a virtually tolerance-free manner if necessary by way of an additional programme control.

Claims (26)

1. A method for the continuous punching of holes in a wall of rod-shaped hollow bodies, in which punched holes lying substantially opposite each other on the rod-shaped hollow body are punched by using a matrix positioned inside the hollow body, and in which the punching actions to produce the opposite punched holes take place in the counter direction to the interior of the rod-shaped hollow bodies and the wast pieces produced with the punching action are removed by the matrix inside the rod-shaped hollow bodies.

2. Method according to Claim 1, wherein the counter-directional punching actions can be carried out simultaneously on several rod-shaped hollow bodies.

3. Method according to Claim 1 or 2, wherein the working plane of the punching tools in the vertical direction is provided for when the work pieces are positioned next to each other in the horizontal plane.

4. Method according to Claim 1 or 2, wherein the working plane of the punching tools in the horizontal plane is provided for when the work pieces are positioned one above the other in a vertical direction.

5. Method according to any one of Claims 1 to 4, wherein the ejection of the waste punched pieces takes place in the area of the dead-centre position of the punching tools during the working stroke.

6. Method according to any one of Claims 1 to 5, wherein the punching tools of the one side precede the punching tools of the other side during the working stroke and return stroke.

7. Method according to any one of Claims 1 to 6, wherein the working stroke of the punching rools is controlled so that the latter cut the walls of the work piece gently and a quick working stroke only takes place after that.

8. Method according to any one of Claims 1 to 7, wherein the stroke of the punching tool is approximately two to four times the wall thickness of the hollow bodies to be punched and is maintained constant in the main.

9. Apparatus for the continuous punching of holes in a wall of rod-shaped hollow bodies of any cross-section, in which the punched holes essentially lying opposite each other on the rod-shaped hollow body are punched by using a matrix positioned inside the hollow body, and in which the drive of the punch pressure takes place by way of a doubly operating hydromechanical toggle lever system and the tool supports are moved in a counter-directional manner with the punches of the punching tools acting upon a multipart matrix, the retaining rods of which are mounted in a displacable manner on a stationary bearing block.

10. Apparatus according to Claim 9, wherein the hydro-mechanical toggle lever system consists of a hydraulic cylinder, an operating piston, one or more pressure balance cylinders, one hinged to the point of rotation and a piston rod guided in at least one bearing and toggle lever fish plates, which are connected in a jointed manner on the one side if necessary by way of an adjusting element to the lower tool support and on the other side with a plate.

11. Apparatus according to Claims 9 and 10, wherein the drive takes place by way of more than one pair of toggle levers.

12. Apparatus according to Claims 9 to 11, wherein the lower tool support and the upper tool support are guided in columns which are securely connected to the press body.

13. Apparatus according to Claims 9 to 12, wherein the upper tool support is connected by way of an adjusting device to å plate and this is connected to the additional plate by way of sup ported guide rods sliding in the columns, the lower toggle lever fish plates engaging on the additional plate.

14. Apparatus according to Claims 9 to 13, wherein the drive of the feed sliding carriage takes place at the same time by way of the hydraulic control unit.

15. Apparatus according to Claim 9, wherein the matrix consists of the outer parts and an inner part which are disposed towards each other in a wedgeshaped manner and are connected by means of a guide.

16. Apparatus according to Claims 9 and 15, wherein the inner part has a part of wedge-shaped or nose-like shape covering the lower aperture of the matrix and is furnished with impact edges which expel the waste-punched pieces.d

17. Apparatus according to Claims 9, 15 and 16, wherein the outer parts of the matrix are disposed in slits of a connecting flange sliding vertically to the longitudinal axis.

18. Apparatus according to Claim 9 and Claims 15 to 17, wherein a rod engaging on the matrix is guided in a telescopic manner in the outer tubular pull rod, if necessary by way of additional spacers arranged in a spaced manner.

19. Apparatus according to Claim 9 and Claims 15 to 18, wherein the matrix rod is fixed to a movable cross-traverse of the bearing block by way of equalizer springs.

20. Apparatus according to Claim 9 and Claims 15 to 19, wherein an elastic buffer, e.g. in the form of a set of cup springs is provided between the cross-traverse.

21. Apparatus according to Claims 9 and 15 to 20, wherein the cross-traverse is connected to a pneumatic, hydraulic or electrical clamping arrangement by way of a bolt.

22. Apparatus according to Claims 9 and 15, wherein an air current is active, preferably on the lower matrix opening, during the releasing procedure of the inner part of the matrix.

23. Apparatus according to Claims 9 and 22, wherein an air cushion is stored inside the tubular retaining rod and the air current becomes effective by way of a guiding edge.

24. Apparatus according to one of the Claims 9 or 10, wherein an elastic hydraulic cushion in the hydraulic cylinder of the power press serves to slow down the cutting stroke when the punching procedure is ending.

25. A method for the continuous punching of holes in a wall of rod-shaped hollow bodies, substantially as hereinbefore described with reference to the accompanying drawings.

26. Apparatus for the continuous punching of holes in a wall of rod-shaped hollow bodies, substantially as hereinbefore described with reference to the accompanying drawings.