GB1603653A

GB1603653A - Production of formed metal objects

Info

Publication number: GB1603653A
Application number: GB2966977A
Authority: GB
Original assignee: Alcan Aluminum Ltd; SIMEC Lochaber Hydropower 2 Ltd
Current assignee: Rio Tinto Alcan Inc; SIMEC Lochaber Hydropower 2 Ltd
Priority date: 1977-07-14
Filing date: 1977-07-14
Publication date: 1981-11-25
Also published as: FR2397243B3; BE868998A; FR2397243A1

Description

(54) IMPROVEMENTS IN THE PRODUCTION OF FORMED METAL OBJECTS (71) We, ALCAN ALUMINIUM (U.K.) LIMITED a British Company, of 30 Berkeley Square London W.1., do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to the production of formed metal objects and has a particularly useful but not exclusive application in the production of objects by localised deformation of an aluminium extruded section.

It is well known, for example, to produce putlogs for use in tubular scaffolding by flattening one end of a short length of extruded aluminium tube. Such components normally require the use of an alloy which is quenched and subsequently artificially aged in order to develop its required mechanical properties. In producing such components it is the normal practice to quench the extruded section shortly after leaving the die and to form the end or ends in a subsequent forming operation performed after the extrusion has been cut into individual lengths.

It is found that there is a danger of hair-line cracks in the sharp bend at the side margin of the flattened areas when the forming operation is carried out in the cold after the lapse of several hours. In one production operation employing a well known aluminium magnesium silicide alloy it was found that there was an undesirably high tendency for the occurrence of such cracks if the formation of the end or ends was delayed by more than about 6 hours. This requirement that the end be formed within a limited time period can lead to production difficulties.

Where the forming operation is delayed it is necessary to reheat the end of the tube before forming. This leads to considerable increase in the cost of performing the forming operation and may moreover lead to some loss in mechanical properties in the region of the tube adjacent to the flattened end or ends.

In order to overcome the abovementioned difficulties in the production of objects, which require a subsequent forming operation to be applied to an extruded light metal section of an alloy which requires a subsequent quench in order to develop desired mechanical properties, the present invention contemplates applying a forming step at a location close to the die where the temperature of the metal is still within 1500C of its melting point and where in consequence it can still be deformed by a relatively small force.

Accordingly in one aspect the invention provides a method of carrying out a forming operation on an extruded light metal section comprising moving a forming means from an inoperative position out of contact with the section into an operative position in which the forming means engages the external surface of the section at a location adjacent the extrusion die on emergence of the section from the die and while the metal is still hot in a manner to make a predetermined change in the cross-sectional shape of the section as extruded from the die.

The invention also provides the combination with an extrusion press for extruding a light metal section of an apparatus comprising forming means capable selectively of being moved into engagement with the external surface of the section at a location adjacent the extrusion die of the press where the extrusion is still hot thereby to make a predetermined change in the crosssectional shape of the section as extruded from the die, and of being moved out of engagement with the section.

The contemplated deformation of, for example, an extruded aluminium alloy tube may be performed by a simple apparatus supported on the table of the extrusion press and comprising a fixed lower jaw and a vertically movable upper jaw operated by a hydraulic or pneumatic cylinder. In most instances it is preferred that this simple deforming apparatus shall be mounted on the table so as to move longitudinally with the extrusion during the forming operation, with reverse travel to its starting position when the jaws release the extrusion. In most cases the forming apparatus is preferably drawn forward by its engagement with the extrusion. The forward movement may be employed to develop pneumatic or hydraulic potential energy for returning it to its start position.

In alternative arrangements the forward movement of the forming apparatus may be separately powered by a pneumatic, hydraulic, electrical or mechanical drive so as to move it forward essentially in synchronism with the extrusion. That type of arrangement is to be preferred when the deformation of the extrusion is performed by an impact-type forming tool and there is only a very short dwell time during which the jaws grip the extrusion.

In some instances it may be unnecessary for the deformation apparatus to move.

Thus in some instances it is only necessary to perform one deformation operation on the extrusion and in those circumstances the deformation operation may be applied at the conclusion of the extrusion operation, when the extruded section is at rest. In the manufacture of tubular scaffolding for example a single length of extruded tube may be flattened at a selected position near its tail end. The length of extrusion formed from a single billet is then cut into a number of lengths of tube and two putlogs are produced by cutting across the middle of the single flattened portion.

It is also possible to contemplate an operation in which the ram of the extrusion press is halted during the performance of each forming operation. This would not be a wholly desirable system owing to the possibility of die marks being left on the extruded section each time the extrusion operation was halted.

Another simple application of the technique of the invention is to the manufacture of cable ends for overhead transmission conductors. The cable end consists of a short length of tube, which is adapted to be crimped onto the end of the conductor cable, and a flattened end portion, which is adapted to be drilled to receive a securing bolt. These components do not present any particular cracking problem, since they are produced from non-heat-treatable electrical conductor grade aluminium. However it is more convenient to perform the flattening operation at multiple positions along the length of a single extrusion as it emerges from the die, the extrusion thus deformed being cut into lengths, alternate cuts being through the flattened and unflattened portions of the extrusion respectively.For this type of product it is clearly more convenient to perform the deformation operation with an apparatus which moves forwardly with the extrusion during the forming operation.

According to a further development of this application of the invention the deformation apparatus may be employed to provide a two-step operation on the tubular extrusion. In the first step a flattened portion of the extruded section may be formed and in the second step one or more holes e.g. two longitudinally spaced holes, may be punched through the flattened portion.

One such form of apparatus according to the invention for performance of a series of flattening operations on a single hollow extruded section is hereinafter described with reference to the accompanying drawings wherein: Figure 1 is an end view (in the direction of extrusion travel) of the hydraulic forming apparatus and Figure 2 is a side view of the deforming apparatus carriage and associated parts.

Figure 3 illustrates a flattening operation on a tubular extruded section.

Referring firstly to Figure 2 a conventional extrusion press includes a die head 1, through which a section 2 is extruded and is led to a guide 3, beyond which is located a puller device (not shown), which grips the leading end of the extruded section and draws it out along the table 4 of the press. In accordance with the present invention a forming apparatus 5 of the type illustrated in Figure 1 may be located in a fixed position between the die head 1 and the guide 3 or more preferably is arranged so as to move longitudinally on the table 4 while it is performing a forming operation on the extruded section 2, as illustred in Figure 2.

The forming apparatus 5 is of very simple construction and as shown in Figure 1 comprises a pair of parallel jaw support plates 6, interconnected by a horizontal lower jaw support 7 and a cylinder mounting plate 8. A fixed lower jaw 9 is bolted to the support 7.

To coact with the lower jaw 9 a movable upper jaw 10 is supported by the ram of a hydraulic cylinder 11 secured in the mount mg plate 8. The jaw 10 is provided with a tail 12, which slides on plurality of posts 14, supported on a transverse member 15. A compression spring 16 is arranged around each post 14 and is compressed during downward movement of the jaw 10 on admission of fluid under pressure to cylinder 11. The springs 16 raise the jaw 10 when the cylinder is depressurised. In some instances it may be deisrable to provide a means for ejecting fluid from cylinder 11 to speed up the return movement of the jaw 10 to its start position.

In Figure 2 the forming apparatus 5 is mounted on a trolley 20, provided with a spring bumper 21, which in the start position is compressed against the die head or associated fixed part of the press.

The trolley 20, which runs on the press table 4, is moved into position against the die head by a pusher arm 22 which is slidable in a way formed in the table 4. In Figure 2 the arm 22 is shown in its fully retracted position. The arm 22 is connected to a cable 23 which extends between anchorage points 24 and 25. The cable 23 is driven in the forward direction (movement of arm 22 towards the die head) by a pneumatic cylinder unit 26 to move the carriage 20 to the position shown in Figure 2. On release of air pressure from cylinder 26 the arm 22 is driven back to the position shown in Figure 2 by a pulley-supported counterweight 27 acting on cable 23. The trolley 20 is connected to a cable 28, which is anchored at 29 and is acted on by a pulley-supported counterweight 30.

At the start of an operation the trolley 20 is at rest at the position shown in Figure 2 and is held in this position by the arm 22 to maintain the bumper spring 21 in a compressed condition. So soon as a forming operation is initiated the ram of the double acting air cylinder commences to return from its extended position towards the position shown in Figure 2. This allows the arm 22 to move and thus permits the spring bumper 21 and counterweight 30 to accelerate the trolley 20, supporting the forming apparatus 5, before it is gripped by the descending upper jaw 10, so the trolley is already moving (but not necessarily at the same speed) when the moving extruded section 2 is gripped between the jaws 7 and 10.In performing a flattening operation on the quite soft, hot extruded section 2 the hydraulic pressure in the cylinder 11 will commence to rise rapidly when the resistance to movement of the bottom jaw increases when the tubular section is fully flattened. The hydraulic circuit of the cylinder 11 is provided with an overload device which is effective to switch off the supply of hydraulic fluid to cylinder 11. The springs 16 immediately cause the jaws 7 and 10 to separate and trolley movement ceases. The operation of the hydraulic overload switch reverses the supply of air to the pneumatic cylinder 26 and this drives the arm 22 to return the trolley 20 and forming device 5 to its start position.

At the moment of release extrusion 2 begins to move longitudinally relative to the jaws 7 and 10. To minimise interference between the jaws and the extrusion the jaws are provided with rounded end surfaces 31 and 32 as indicated in Figure 3.

WHAT WE CLAIM IS: 1. A method of carrying out a forming operation on an extruded light metal section comprising moving a forming means from an inoperative position out of contact with the section into an operative position in which the forming means engages the external surface of the section at a location adjacent the extrusion die on emergence of the section from the die and while the metal is still hot in a manner to make a predetermined change in the cross-sectional shape of the section as extruded from the die.

2. A method as claimed in claim 1, wherein the forming means moves with the section as extrusion proceeds.

3. A method as claimed in claim 1, wherein the forming operation is carried out at the conclusion of the extrusion operation, the forming means being fixed relative to the extrusion die.

4. A method as claimed in claim 1 or claim 2, wherein the section is a tube and the forming operation comprises flattening a part of the length of the tube.

5. A method as claimed in claim 4, wherein the forming operation further comprises punching one or more holes through the flattened part of the tube.

6. A method as claimed in any one of claims 1 to 5, wherein the forming means carries out a forming operation at spaced intervals lengthwise of the section.

7. The combination with an extrusion press for extruding a light metal section of an apparatus comprising forming means capable selectively of being moved into engagement with the external surface of the section at a location adjacent the extrusion die of the press where the extrusion is still hot thereby to make a predetermined change in the cross-sectional shape of the section as extruded from the die, and of being moved out of engagement with the section.

8. The combination claimed in claim 7 wherein the forming means of the said apparatus is mounted for guided movement lengthwise of a section extruded through the die.

9. The combination claimed in claim 8, wherein the forming means is adapted to grip the extruded section releasably and to be moved by the section as extrusion proceeds, and wherein the apparatus comprises a device which accumulates potential energy from such movement of the forming means and which operates to return the forming means to its starting position when the section is released from the forming means.

10. The combination claimed in claim 8, wherein the apparatus comprises means for

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. it may be deisrable to provide a means for ejecting fluid from cylinder 11 to speed up the return movement of the jaw 10 to its start position. In Figure 2 the forming apparatus 5 is mounted on a trolley 20, provided with a spring bumper 21, which in the start position is compressed against the die head or associated fixed part of the press. The trolley 20, which runs on the press table 4, is moved into position against the die head by a pusher arm 22 which is slidable in a way formed in the table 4. In Figure 2 the arm 22 is shown in its fully retracted position. The arm 22 is connected to a cable 23 which extends between anchorage points 24 and 25. The cable 23 is driven in the forward direction (movement of arm 22 towards the die head) by a pneumatic cylinder unit 26 to move the carriage 20 to the position shown in Figure 2. On release of air pressure from cylinder 26 the arm 22 is driven back to the position shown in Figure 2 by a pulley-supported counterweight 27 acting on cable 23. The trolley 20 is connected to a cable 28, which is anchored at 29 and is acted on by a pulley-supported counterweight 30. At the start of an operation the trolley 20 is at rest at the position shown in Figure 2 and is held in this position by the arm 22 to maintain the bumper spring 21 in a compressed condition. So soon as a forming operation is initiated the ram of the double acting air cylinder commences to return from its extended position towards the position shown in Figure 2. This allows the arm 22 to move and thus permits the spring bumper 21 and counterweight 30 to accelerate the trolley 20, supporting the forming apparatus 5, before it is gripped by the descending upper jaw 10, so the trolley is already moving (but not necessarily at the same speed) when the moving extruded section 2 is gripped between the jaws 7 and 10.In performing a flattening operation on the quite soft, hot extruded section 2 the hydraulic pressure in the cylinder 11 will commence to rise rapidly when the resistance to movement of the bottom jaw increases when the tubular section is fully flattened. The hydraulic circuit of the cylinder 11 is provided with an overload device which is effective to switch off the supply of hydraulic fluid to cylinder 11. The springs 16 immediately cause the jaws 7 and 10 to separate and trolley movement ceases. The operation of the hydraulic overload switch reverses the supply of air to the pneumatic cylinder 26 and this drives the arm 22 to return the trolley 20 and forming device 5 to its start position. At the moment of release extrusion 2 begins to move longitudinally relative to the jaws 7 and 10. To minimise interference between the jaws and the extrusion the jaws are provided with rounded end surfaces 31 and 32 as indicated in Figure 3. WHAT WE CLAIM IS:

1. A method of carrying out a forming operation on an extruded light metal section comprising moving a forming means from an inoperative position out of contact with the section into an operative position in which the forming means engages the external surface of the section at a location adjacent the extrusion die on emergence of the section from the die and while the metal is still hot in a manner to make a predetermined change in the cross-sectional shape of the section as extruded from the die.

carrying out a forming operation by impact which means is powered by a drive indepen dently of the section to move substantially in synchronism with the section during the forming operation thereon.

11. The combination claimed in claim 8, wherein the forming means is mounted on a trolley for guided movement lengthwise of the extrusion and wherein the apparatus comprises releasable means for moving the trolley in a direction opposite to the direc tion of extrusion into engagement with a spring so as to load the spring, whereby when the releasable means is released the spring accelerates the trolley in the direction of extrusion.

12. The combination claimed in claim 11, wherein acceleration of the trolley in the direction of extrusion is assisted by a weight attached to a vertical run of a cord or other flexible tie which extends upward from the weight, round a guide and has its other end connected to the trolley.

13. A method of carrying out a forming operation on an extruded light metal section substantially as hereinbefore described.

14. The combination with an extrusion press for extruding a light metal section of an apparatus substantially as hereinbefore described with reference to and as illus trated in the accompanying drawings.