This invention relates to apparatus for punching holes in elongate sections, and more particularly to self-contained punching apparatus for punching holes in semi-finished and finished hollow sections. BACKGROUND

Existing systems for punching holes in elongate hollow sections, which may be welded and seamless pipes, tubes, hollow sections and extrusions whether of open, closed, flat or folded form commonly comprise a combination of proprietary machines for each of the processes involved, typically punch or press machines and specially designed feed tables, tools and die holders. Such equipment is extremely expensive.

The die holder and arbor arrangement used inside the hollow section to prevent collapsing of the section wall during the punching step is mechanically guided from outside the hollow section by utilising a dowel pin locating in a previously punched hole and aligning the arbor.

Such a method only permits the punching of holes having predetermined fixed centres, it being necessary to completely change the punch and die equipment if holes of alternative sizes and centres are required. DISCLOSURE OF THE INVENTION

It would be desirable to be able to provide a self-contained apparatus which enabled the punching in an elongate hollow

section, whether of open or closed configuration, of single or multiple patterns of geometric or multi-faceted apertures at infinitely variable distances along, and at infinitely variable positions around, the section.

According to the present invention there is provided apparatus for punching holes in an elongate hollow section, the apparatus comprising an elongate arbor over which is located the section to be punched, a die head at or adjacent the end of the arbor and within the hollow section, at least one punch for co¬ operative alignment with the die head, and guide means for the hollow section to locate said section relative to the arbor and die head, the guide means being so arranged as to permit selective axial and rotational movement of the section relative to the or each punch and die head whereby holes can be punched in substantially any region of the section.

Preferably the guide means comprise rollers positioned above and below and to each side of the section, the locations of said rollers being adjustable to accommodate sections of varying sizes .

In one embodiment of the invention, the rollers and the section guided thereby are rotatable as an assembly relative to the or each punch to enable punching of holes at any peripheral point around the section.

The apparatus may comprise at least one pair of diametrically opposed punches, and may further comprise a plurality of punches disposed along the length of the arbor, for

example at least one further pair of diametrically opposed punches.

The die head may incorporate means therein for co-operation with the internal surface of the hollow section to achieve centralisation of the die head within the hollow section, which means may be, for example, fluid-operated or mechanically operated.

Operation of the centralisation means may be computer- controlled, and may utilise a laser beam incident upon the arbor to determine the location thereof and to adjust it accordingly.

The laser beam may be incident upon one or more sensors located at or adjacent the arbor, or may be reflected or redirected to one or more sensors located remotely of the arbor, which sensors actuate the computer control of the position of the die head.

The centralising means may comprise one or more fluid- actuated assemblies mounted in the die head to extend radially thereof and reacting between the die head and the internal wall of the hollow section to move the die head relative to the hollow section to a central position therein.

In an alternative arrangement the centralising means comprises a fluid-actuated piston-cylinder assembly extending longitudinally of the die head and co-operating with an elastically-deformable member extending substantially diametrically of the arbor, extension of the piston of the assembly causing symmetrical deformation of said member into

engagement with the internal wall of the hollow section to move the die head relative to the hollow section to a central position therein.

The apparatus may include drive means for feeding the hollow section longitudinally over the arbor towards the punching position, and location means for determining the longitudinal punching position.

The longitudinal punching position may be determined by abutment of the end of the section with a mechanical stop.

Alternatively the drive means may be under said computer control, the longitudinal punching position being determined by appropriate computer programming.

Apparatus of the invention enables hollow section to be advanced into a processing area therein either by hand or by an automatic feed magazine system and positioned longitudinally either mechanically or automatically, the rollers serving to locate the section accurately and centrally over the arbor/die head in the punch area.

In the case of relatively short lengths of hollow section, the stiffness of the arbor is sufficient to maintain accurate alignment of the die and punch arrangement .

With longer lengths of hollow section, deflection of the arbor may occur as its length increases, the weight of the arbor and die head and the friction between the die head and the hollow section causing the die head to be deflected from a central position within the hollow section.

The aforementioned centralising means can then be actuated to relocate the die head centrally of the hollow section for accurate punching thereof. Further intermediate support of the arbor may be provided by pneumatically operated air pads mounted along the arbor as well as at the die head to provide cushions to 'float' the arbor and to reduce frictional drag between contacting surfaces.

The apparatus may be arranged for the punch or punches to move in a vertical or a horizontal plane, or any planes therebetween, and to punch single or multiple holes diametrically opposite one another. The die head is provided with inserts coinciding with the punch layout.

For progressively longer hollow sections, the machine frame and arbor can be extended to accommodate the section in question, while, as mentioned above, a series of punching stations can be provided along the length of the section. Intermediate punching may be provided by moveable carriages that adjust along the length of the extension casing or fabrication.

The punched holes may be produced by single or multiple arrays on any single surface of the hollow section, or may be produced by simultaneous punchings on diametrically opposite faces of the hollow section as single or multiple through holes of guaranteed accuracy.

Diametrically opposed holes may be the same or different, and may be very closely spaced both along the length of the section and circumferentially around the section. Close

tolerances between the punch and the die set provide for clean holes.

The sections to be punched may be of metal or of a plastics material and may be of any cross-sectional shape.

The shape and size of the die head at or adjacent the free end of the arbor is chosen to correspond with the internal profile of the hollow section being processed, with the clearance between the internal wall of the section and the die head being calculated to ensure that, on punching, deformation of the hollow section remains within the elastic limits of the material.

The physical size of the die head may be capable of being increased and decreased to suit the internal configuration of the hollow section during the punching operation so that a clearance is maintained at the end of each punch cycle, and the hollow section is fully supported during the punching operation.

In the case of relatively short lengths of hollow section, the apparatus, as detailed above, utilises a fully 'floating' arbor system in which the arbor and die head are maintained out of contact with the internal wall of the section with minimum allowable clearance between the die inserts and said wall.

This arrangement may be used to punch holes about 1 metre from the free end of the section, and, if loaded by hand, would provide a significant reduction in capital cost over conventional hydraulic press and retro-fit systems currently available, while an integrated path to upgrade the system to full automation can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Figs. 1, 2 and 3 are side view, front view and plan view respectively, all in partial fragmentary view and section, of apparatus according to the invention;

Fig. 4 is a view of a die head of apparatus according to the invention showing first centralising means for the die head,

Figs 4a and 4b are sections on the lines A-A and B-B respectively of Fig. 4,

Fig. 5 is a view of a die head of apparatus according to the invention showing second centralising means for the die head, and

Fig. 6 is a section on line A-A of Fig. 5. DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, there is illustrated a machine for punching holes in an elongate hollow section 2, typically of circular or rectangular section, which is fed to the apparatus by an associated feed mechanism (not shown) .

The apparatus includes an elongate arbor 4 which is rigidly and accurately secured to the machine to extend horizontally from one end thereof to a central processing region within the machine .

A die head 6 is secured to the free end of the arbor 4 within said processing region, the die head 6 carrying one or more inserts 8 which may be fixed or adjustable relative to the die head 6.

The arbor 4 extends within an outer distance tube 10 compressed between the die head 6 and a support alignment bush 12

for the arbor 4 .

The alignment bush 12 is mounted on the machine in such a manner as to permit accurate positioning of the longitudinal central axis of the arbor 4 and therefore of the die head 6 within the processing region of the machine .

The length of the arbor 4 may be increased by adding suitable extension pieces thereto as well as appropriate support members therefore. Such an arrangement is particularly advantageous where, for example, hollow sections such as 2 require holes to be punched in each end and possibly the centre, and such holes can then be punched in one operation by providing one or more intermediate punch stations which may be movable along the extended arbor.

The die head 6 is shaped to conform with the internal profile of the hollow section 2 such that said die head 6 is closely spaced from the internal walls of the section 2 with the section 2 located thereover.

The machine includes guide means for accurately positioning the hollow section 2 over the arbor 4 and die head 6 to ensure said close spacing between the die head 6 and the section 2. The illustrated guide means comprise a first pair of roller sets 14, 16 one to each side of the hollow section 2, and a second pair of roller sets 18, 20 above and below the hollow section 2.

The positions of these roller sets 14 to 20 is adjustable, and they are located in gripping engagement with the outside surface of the section 2 whereby said section 2 is correctly

positioned relative to the arbor 4/die head 6 therein.

Each roller of the sets 14 to 20 is preferably of solid steel with a bonded rubber coating, the roller set 20 supporting the weight of the section 2, while the adjustability of the sets 14, 16 to the sides of the section 2 enables variable lateral positioning of the section 2 relative to the punch mechanism to provide for punched holes offset to the edge of rectangular sections 2.

All sets of rollers 14 to 20 may be used to automate the feed and advance of the hollow section 2 and to sequence the section 2 to various longitudinal locations.

A stop 22 adjustably mounted on bars 24 secured to the machine frame provides for longitudinal location of the section 2. There may be several such stops located along the length of the machine, and each stop may be provided with mechanical or electrical means of retraction to allow the section 2 to be moved into subsequent processing positions.

The machine includes pairs of diametrically opposed punch tools 26 each hydraulically operated by means of power from an integrated control system 28 within the machine base frame.

The number and shapes of the punch tools 26 can be chosen to suit particular requirements and may be adjustably positioned within the machine.

In order to accommodate hollow sections of various sizes, the tools 26 and their associated hydraulic cylinders can be moved towards and away from the processing region of the machine.

The entire arrangement of punch tools 26, associated hydraulic cylinders and the guide roller sets 14 to 20 may be mounted in a rotatable body to provide for punching holes at any circumferential position around the hollow section 2. The use of a stepper motor control and a toothed belt gear reduction ensures great accuracy is achieved.

On punching a hole in a section 2 accurately located about an arbor 4 the die head 6 of which is centrally positioned within the section 2, the forces of the punch tools 26 are initially directed against the rubber coatings of the set 20 which are elastic and deflect, support then being transferred to bearing blocks positioned to coincide with the allowable deflection of the section 2. These blocks are mounted above and below the hollow section and provide a method of stripping the punched material from the punched hole.

This method is similarly used for the counter punching of holes where two horizontally opposed punch tools provide for the formation of through holes in opposite walls of the hollow section 2.

Further, the punch tools 26 are designed with a shoulder an appropriate distance from the end of the punch tool to engage the hollow section on completion of the punching operation and supporting the hollow section to prevent over deflection of the combined arbor and hollow section.

The die head 6 is designed to accept varying shapes and sizes of die inserts 8, the positions of which are adjustable

within certain limits to coincide with the associated punch tool. Similarly, as mentioned above, the tools can be chosen to provide a variety of shapes, offsets and hole arrays, the machine of the invention accounting for all basic hole arrangements. Thus the capital costs of specialised tooling are reduced.

As mentioned above, the stiffness of a relatively short arbor 4 is sufficient to maintain it centrally of the section 2 whereby the die head 6 and inserts 8 thereon are accurately positioned relative to the punch tool 26 to provide for accurate punching of the section 2.

In the case of longer arbors 4, it is necessary to provide centralising means for the die head 6 to counteract the bending of the arbor 4 that occurs as a result of the weight thereof and the weight of the die head 6 and which causes de-centralisation of the die head 6.

Referring to Figs. 4, 4a and 4b, there is shown a first centralising arrangement. The die head 6 incorporates a hydraulic piston-cylinder assembly 30 extending longitudinally and centrally thereof, the free end of the piston comprising a conical head 32. A deformable elastic spring 34 extends diametrically of the die head 6, the spring being of generally U- shape with the legs of the U terminating in diametrically-opposed lobes 36, 38. On extension of the piston of the assembly 30, the head 32 is driven between the lobes 36, 38 to deform the spring 34 and to urge the lobes 36, 38 radially outwardly into engagement with opposed regions of the internal wall of the

section 2. The symmetrical nature of the spring 34 is such as to centralise the die head 6 within the section 2.

Referring to Figs. 5 and 6, there is shown an alternative centralising arrangement. The die head 6 has a pair of opposed pneumatic actuators 40, 42 each extending radially of the die head the pistons of which can be extended to engage opposed side regions of the internal wall of the section to centralise the die head 6 within the section 2. Shoulder stops at the end of the piston strokes prevent over-travel, while it is preferred that replaceable wear pads of varying shapes are fixed to the adjustable tips of the pistons to allow for variations in wall thickness of the section 2, and for offset punching of rectangular sections. The wear pads are sacrificial to the system and may be employed about the die head 6 and the arbor 4 to prevent wear.

The second centralising arrangement of Figs. 5 and 6 is somewhat more accurate than that of Figs. 4,4a and 4b, and the arrangement used is determined to a certain extent by the degree of accuracy required of the position of the hole to punched.

It is preferred that all movements associated with the machine are computer controlled to ensure extreme accuracy of the locations of the punched holes. In particular, actuation of the various die head centralising means, which are crucial to alignment of the punch tool 26 and the die head inserts 8 with relatively long arbors 4 , may be achieved by a laser device supplying information to a computerised control mechanism.

More particularly, a mirror or similar reflecting device is mounted on the free end of the die head 6, and a laser beam is incident thereon. The beam is reflected to one or more remote sensors to provide an indication of the precise location of the die head 6, the computer being programmed to interpret the information provided to the sensors and to actuate the centralising means accordingly.

Alternatively the sensors may be located on the arbor/die head, and the laser beam may be directly incident thereon, or may be redirected to associate sensors, for example by way of fibre optics .

The elastic properties of the materials of the hollow sections to be processed can be used to advantage. All deformations are reversible and path-independent in the elastic range of the material - when a piece of material is stretched elastically, not only does it get longer, but it also gets thinner. This is taken to advantage by incorporating a degree of deformation of the material prior to shearing at the punch tool.

The operating face of each punch tool 26 may taper to a central conical point of sufficient size and angle to deform the waste piece of material punched from the section 2 into the orifice of the die insert, thereby providing a self-centralising effect which further ensures close alignment of the punch tool and die.

Drawing the ductile material of the section into the die produces an annular area of plastic and elastic deformation the

advantages of which are two fold: a) the waste piece of material is inhibited from adhering to the punch tool tip by residual elastic forces. b) the partial reduction of section about the annular shear plane improves the quality of the punched hole by eliminating the ridge formed from the outlet side of the punch. Thus reworking of the aperture close to the ends of the hollow section is eliminated.

This results in improved productivity, particularly as regards machined apertures, compared with conventional punch tools .

The hydraulic system for actuating the punch tools 26 incorporates a method of control whereby the tool is advanced up to contact with the surface of the section 2 under the direct pressure and motive power and speed of the associated hydraulic pump.

The approach of the tool to the section is steady and not abrupt - an increase in back pressure as the conical point of the tool deforms the hollow section is sensed.

Accumulated pressure is released into the hydraulic cylinder of the tool to cause the tool to shear through the wall of the section with a snap action.

Accumulated pressure is also used to retract the cylinder back to its rest position ready for the next cycle. During the dwell period between consecutive punches, the accumulator contained within the hydraulic system is recharged.

Thus there is provided a self-contained system which combines all the equipment necessary to punch holes in hollow sections at any desired centre, distance and pattern along the section and which is preferably under computer control .

The system is designed to guide the arbor arrangement from inside the section, either mechanical or electromechanical means being used to position the arbor/die head into alignment with the punch tool.

The punch tool holding arrangement is adjustable to locate the punch tools at any position over the section surface for alignment of the tool and die set.

Alternatively or additionally, means may be provided for rotating the hollow section about its central longitudinal axis and relative to the punch tools.

The system can be mass produced at relatively low cost compared with current machines.

Clearly the precise construction and operation of the machine can depart from those described and illustrated without departing from the scope of the invention. For example, the roller sets 14 to 20 may be replaced by metal guide blocks.