WO1994015735A1

WO1994015735A1 - Improvements in rotary forging

Info

Publication number: WO1994015735A1
Application number: PCT/GB1994/000043
Authority: WO
Inventors: Mufti Mohmed Ashraf; Sean Francis Tedstone; Steven Marshall
Original assignee: Penny & Giles Blackwood Ltd.
Priority date: 1993-01-13
Filing date: 1994-01-11
Publication date: 1994-07-21
Also published as: GB9300529D0

Abstract

A rotary forging machine for the rotary forging of elongate workpieces, has a first platen (28) fixed against rotary movement and a second platen (40) rotatable relative to the first platen (28). The first and second platens (28 and 40) have mutually cooperating opposed working surfaces (30, 76) between which a rotary forging operation is effected in use. At least one of the platens (28, 40) is displaceable along a displacement axis towards the other platen. A precession drive precesses the second platen (40) so that its axis of rotation (50) is precessed at an acute angle about the displacement axis. Rolls (80) feed an elongate workpiece (W) in stepwise fashion between the working surfaces (30, 76) from an inlet side (36) to an outlet side (38) of the machine. The first platen (28) has a guide groove (34) in its working surface (30) extending inwardly of the latter from an edge of such working surface (30) at the inlet side (36) of the machine. The guide groove (34) has a depth over a portion of its length adjacent the inlet side (36) of the machine which is greater than the corresponding dimension of the workpiece (W). The rolls (80) are synchronised with the precession drive means so that the rolls (80) present a fresh portion of the elongate workpiece (W) to a working zone of the machine when the precession drive has precessed the second platen (40) so that it is no longer performing a rotary forging operation on the workpiece (W) in the working zone.

Description

IMPROVEMENTS IN ROTARY FORGING

This invention relates to improvements in rotary forging and is more particularly concerned with a machine for the rotary forging of elongate workpieces and particularly, but not exclusively, workpieces of continuous length eg wire.

Rotary forging machines have been known for very many years for the forging of shaped workpieces (e.g., sintered bodies or green compacts) for the purpose of improving densification, wherein the workpiece is introduced between upper and lower platens. The upper and lower platens are moved about respective axes which are mutually inclined so that, at any instant during the forging operation, only part of the workpiece is being subjected to a forging operation. At the end of the rotary forging operation the whole of the workpiece has been forged and it is then removed from the machine.

Rotary forging machines have been known since the early 1900's, see for example GB-A-1205171. A more recent design of rotary forging machine has been disclosed in GB 2041268. As far as we are aware, there are no designs of rotary forging machine which are capable of performing rotary forging operations automatically on elongate workpieces such as wires.

It is an object of the present invention to provide a rotary forging machine which is capable of performing a rotary forging operation automatically on an elongate workpiece. According to the present invention, there is provided a rotary forging machine for the rotary forging of elongate workpieces, comprising: a first platen fixed against rotary movement; a second platen which is rotatable relative to the first platen about an axis, the first and second platens having mutually cooperating opposed working surfaces between which a rotary forging operation is effected in use; displacing means for displacing at least one of the platens along a displacement axis towards the other platen; precession drive means for precessing the second platen so that its axis of rotation is precessed at an acute angle about the displacement axis; feeding means for feeding an elongate workpiece in stepwise fashion between said working surfaces from an inlet side of the machine to an outlet side of the machine, said first platen having a guide groove in its working surface extending inwardly of the latter from an edge of such working surface which is disposed at the inlet side of the machine, said guide groove having a depth over a portion of its length adjacent the inlet side of the machine which is greater than the corresponding dimension of the workpiece; and means for synchronising the feeding means with the precession drive means so that, in use, the feeding means is arranged to present a fresh portion of the elongate workpiece to a working zone of the machine when the precession drive means has precessed the second platen so that it is no longer performing a rotary forging operation on the workpiece in the working zone.

Most preferably, the guide groove extends into the working region of the machine and the depth of said groove in said working zone progressively decreases over at least a portion of its length. The groove may extend substantially completely from the inlet side to the outlet side of the machine and may have a substantially constant depth and width over an end region thereof at said outlet side of the machine.

Conveniently, the first platen has a working surface which is substantially planar and the second platen has a working surface which is conical with a cone angle equal to 180 - α, where α is the angle of precession of the second platen.

In one embodiment, the guide groove extends diametrically relative to the displacement axis. In another embodiment, one or more guide grooves are provided which extend non-diametrical ly e.g., tangentially relative to the displacement axis.

In accordance with conventional rotary forging techniques, the displacement axis and the axis of rotation of the second platen mutually intersect in the working surface of the second platen.

Preferably also, the second platen is freely rotatable about its axis of rotation.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:-

Fig. 1 is an axial section through a rotary forging machine according to the present invention,

Fig. 2 is cross-section showing a detail of the machine of Fig. 1 ,

Fig. 3(i) is a schematic view illustrating the mutual arrangement of first and second platens of the machine in a wire feeding condition, Fig. 3(ii) is a schematic illustration showing the mutual arrangement of the platens of the machine in a rotary forging position,

Fig. 4(i) is a plan view of one of the platens of the machine of Fig. 1 ,

Fig. 4(ii) is a plan view similar to Fig. 4(i) of an alternative embodiment, and

Fig. 5 is a schematic view of a roll drive and synchronizing arrangement, and

Referring now to Fig. 1 of the drawings, the rotary forging machine has a machine frame 10 comprising a bed 12, four vertical columns 14 (only two are illustrated) fixed to the bed 12 and extending vertically upwardly therefrom, and an upper crosshead 16 in which the vertical columns 14 are secured. The columns 14 are equi-spaced around the central vertical axis of the machine. A slide 18 has four sleeves 20 which are slidably mounted on the respective columns 14. The slide 18 is therefore fixed against rotation relative to the machine frame 10 but is displaceable vertically relative thereto. The machine further comprises a horizontally disposed rotary screw 22 carrying a pair of oppositely threaded captive nuts 24. Each nut 24 is pivotally connected to the lower end of a respective link 26 whose upper end is pivotally connected to the slide 18 through the intermediary of a belleville washer 27 (a spring plate capable of withstanding high loads). Thus, it will be appreciated that rotation of the screw 22 results in displacement of the slide 18 vertically upwardly or downwardly depending upon the direction of rotation of the screw 22.

The slide 18 carries a first platen 28 having a planar upper working surface 30. Thus, the first platen 28 is displaceable upon rotation of the screw 22 along a vertical displacement axis indicated by dotted line 32 in Fig. 1 , but is fixed against rotation relative to the machine frame 10. This axis 32 coincides with the central axis of the machine.

Referring now to Fig. 4(i), the upper working surface 30 of the first platen 28 has a guide groove 34 therein which extends diametrically across the first platen 28 so as to intersect the displacement axis 32. The guide groove 34 extends perpendicularly to the plane of the axial section of Fig. 1 from an inlet side 36 of the machine to an outlet side 38 thereof. The depth of the guide groove 34 decreases progressively from the inlet side 36 to a location which is about 7/8ths across the diameter of the first platen 28 from the inlet side 36. The inclination of the guide groove 34 and the depth thereof are chosen such that its depth at the centre of the first platen 28 (i.e., at the displacement axis 32) is marginally greater than the diameter of wire W to be forged. Therefore, it will be appreciated that, when the wire W is fed into the rotary forging machine along the base of the guide groove 34, it will only project above the planar upper working surface 30 of the first platen 28 over a region thereof which is disposed on the opposite side of the displacement axis 32 to the inlet side 36. Thus, the effective working region of the machine is constituted by the region towards the outlet side 38 of the machine.

As can be seen from Fig. 4(i), the width of the guide groove 34 is substantially constant over the whole of the length thereof which is disposed between the inlet side 36 and the displacement axis 32, such width being marginally greater than the diameter of the wire W. Between the displacement axis 32 and the outlet side 38 of the machine, the width of the groove 34 progressively increases up to the location which is 7/8ths across the diameter of the platen 28 and is then constant up to the outlet side 38. Over the last 1/7th of the diameter, the depth of the groove 34 is virtually zero.

The embodiment of Fig. 4(ii) will be described later.

Referring now to Fig. 1 , the rotary forging machine further comprises a second platen 40 mounted on a sleeve 42 rotatably mounted through upper and lower bearings 44 and 46 on a shaft 48 arranged on axis 50 which is disposed at an angle α relative to the displacement axis 32 and which is pivotable about a horizontal axis at a point 51 at which the axes 32 and 50 intersect. The second platen 40 is freely rotatable about axis 50.

The shaft 48 is arranged to be driven by a precession drive which is indicated generally by arrow 52 and which includes a vertical drive shaft 54 mounted in upper and lower bearings 56 and 58 carried by the crosshead 16. The vertical drive shaft 54 is rotatable about a vertical axis which is coincident with the displacement axis 32. The lower end of the vertical drive shaft 54 is of rectangular shape (as will be apparent from Fig. 2), and has a face 54a which is concavely curved over an arc centred on intersection point 51 and which has a slot 54b therein extending diametrically relative to the axis of rotation of the shaft 54. The slot 54b has a concavely curved base 54c which is parallel to the lower end face 54a. Upper end region 48a of the shaft 48 is a close sliding fit within the slot 54b. The end region 48a has a convexly curved end face 48b which mates with the base 54c of the ^"slot 54b. The shaft 48 also includes a pair of convexly curved shoulders 48c which mate with respective portions of the lower end face 54a on opposite sides of the slot 54b. The end region 48a has an internally screw- threaded hole 48d extending therethrough diametrically with respect to the axis 50 and longitudinally with respect to the slot 54b.

A screw-threaded rod 62 is engaged in the hole 48d and passes with clearance through respective holes in a pair of U-shaped locating members 64 which embrace the shaft 54 at opposite ends of the slot 54. Inner and outer tapered shims 66a and 66b and a nut 68 are engaged with each end region of the rod 62 outwardly of each locating member 64 serve to lock the rod 62 at the desired angle relative to the longitudinal axis of drive shaft 54. The shims 66a and 66b of each pair are relatively rotatable and can be appropriately set to take up the misalignment between the nut 68 and the associated collar 64 caused by the angular offset of the axis of the rod 62.

As a result of the above described arrangement, rotation of the shaft 54 causes precession of shaft 48 and thereby of the rotary axis 50 of the second platen 40 at angle, α about the displacement axis 32.

The axes 32 and 50 mutually intersect at point 51 which is at the centre of working surface 76 of the platen 40. The working surface 76 is of downwardly tapering conical shape with a cone angle equal to 180 - α. The horizontal pivot axis 51 intersects the apex of the conical working surface 76. In this embodiment, α is 5°, but can be adjusted before a rotary forging operation by replacing the platen 40 with one having the desired cone angle, and re-setting the angle α by loosening at least one of the nuts 68, rotating rod 62 within the hole 48d to adjust the angle to the appropriate value and then tightening the nuts 68. Referring now to Fig. 5, the rotary forging machine further comprises workpiece-moving means in the form of a pair of haul-off rolls 80 which act on the rotary forged wire emerging from the outlet side 38 of the machine. The rolls 80 are driven by a stepping motor 82 under the control of a control unit 84 to which an angular position sensor 8 is connected. The angular position sensor 86 is disposed adjacent the drive shaft 54 which itself is driven by motor 90.

In operation, the rolls 80 are controlled so that they operate to advance the wire W in stepwise fashion between the working surfaces 30 and 76 of the platens 28 and 40 in synchronism with precession of the platen 40 about displacement axis 32. In the condition illustrated in Fig. 3(i), it will be appreciated that the platen 40 is in a position in which it is not in contact with the wire W since that region of the working surface 76 which is in contact with the working surface 30 overlies the relatively deep region of the groove 34 at the inlet side 36 of the machine. It is at this stage that the stepping motor 82 advances the wire W a short distance. In this embodiment, such distance corresponds to approximately 25% of the radius of the platen 28. The drive to the rolls 80 is then stopped and a rotary forging operation is performed on the freshly exposed portion of the wire W as the platen 40 continues its precession to the position illustrated in Fig. 3(ii). At the same time, a further rotary forging operation is performed upon those regions of the wire W which have already been rotary forged at least once in previous passes but which have not yet left the outlet side 38 of the machine. In this way, the wire W which is originally of circular cross section is rotary forged into a very thin ribbon with an advantageous longitudinal crystal or particle orientation in the case where the wire being forged contains crystals or particles. The above-described procedure is repeated to perform further rotary forging operations progressively on the wire W as it advances through the machine.

During movement of the platen 40 relative to the platen 28, the latter is held in position without rotation of the screw 22. The belleville washer

27 imparts a small degree of resilience in the direction of axis 32 but is sufficiently stiff to permit useful work to be performed on the wire W during each forging pass. The compression of the washer 27 can be altered by appropriate adjustment of the screw 22. Thus, the forging pressure may remain substantially constant up to a pre-set value. Alternatively, the screw 22 may be adjusted automatically during a rotary forging operation so as to vary the forging pressure for the purpose of optimising the properties of the wire being forged.

In the embodiment of Fig. 4(ii), the upper working surface 30 of the first platen 28 has a pair of guide grooves 34 therein. The guide grooves 34, in this embodiment, are mutually parallel and extend across the platen

28 from the inlet side 36 to the outlet side 38 in a direction which is substantially tangential with respect to axis 32. With such an arrangement, it will be appreciated that, as the second platen 40 precesses about the axis 32, the wires in the grooves 34 are contacted in turn during each forging pass. Furthermore, since the direction of extent of each wire is at an angle to the line of rolling contact between the platens 28 and 40, the whole of the exposed length of wire is progressively forged during each pass rather than being substantially simultaneously forged as in the case of the embodiment of Fig. 4(i).

Claims

1. A rotary forging machine for the rotary forging of elongate workpieces, comprising: a first platen (28) fixed against rotary movement; a second platen (40) which is rotatable relative to the first platen (28) about an axis (50), the first and second platens (28 and 40) having mutually cooperating opposed working surfaces (30 and 76) between which a rotary forging operation is effected in use; displacing means (18, 22, 24, 26) for displacing at least one of the platens (28, 40) along a displacement axis (32) towards the other platen; precession drive means (52) for precessing the second platen (40) so that its axis of rotation (50) is precessed at an acute angle (α) about the displacement axis(32); feeding means (80, 82) for feeding an elongate workpiece (W) in stepwise fashion between said working surfaces (30, 76) from an inlet side (36) of the machine to an outlet side (38) of the machine, said first platen (28) having a guide groove (34) in its working surface (30) extending inwardly of the latter from an edge of such working surface

(30) which is disposed at the inlet side (36) of the machine, said guide groove (34) having a depth over a portion of its length adjacent the inlet side (36) of the machine which is greater than the corresponding dimension of the workpiece (W); and means (84, 86) for synchronising the feeding means (80, 82) with the precession drive means (52) so that, in use, the feeding means (80, 82) is arranged to present a fresh portion of the elongate workpiece (W) to a working zone of the machine when the precession drive means (52) has precessed the second platen (40) so that it is no longer performing a rotary forging operation on the workpiece (W) in the working zone.

2. A rotary forging machine as claimed in claim 1 , wherein the guide groove (34) extends into the working region of the machine and the depth of said groove (34) in said working zone progressively decreases over at least a portion of its length.

3. A rotary forging machine as claimed in claim 1 or 2, wherein the groove (34) extends substantially completely from the inlet side (36) to the outlet side (38) of the machine.

4. A rotary forging machine as claimed in claim 1 , 2 or 3, wherein the groove (34) has a substantially constant depth and width over an end region thereof at said outlet side (38) of the machine.

5. A rotary forging machine as claimed in any preceding claim , wherein the first platen (28) has a working surface (30) which is substantially planar and the second platen (40) has a working surface (76) which is conical with a cone angle equal to 180 - α, where α is the angle of precession of the second platen (40).

6. A rotary forging machine as claimed in any preceding claim, wherein the guide groove (34) extends diametrically relative to the displacement axis (32).

7. A rotary forging machine as claimed in any one of claims 1 to 5, wherein one or more guide grooves (34) are provided which extend non-diametrical ly relative to the displacement axis (32).

8. A rotary forging machine as claimed in any preceding claim, wherein the second platen (40) is freely rotatable about its axis of rotation (50).

9. A method of rotary forging an elongate workpiece using a forging machine as claimed in any preceding claim, comprising the steps of (a) causing the feeding means (80, 82) to feed an elongate workpiece (W) in stepwise fashion between said working surfaces (30, 76) from the inlet side (36) of the machine to the outlet side (38) of the machine; and (b) using the means (84, 86) for synchronising the feeding means (80, 82) with the precession drive means (52) so that the feeding means (80, 82) presents a fresh portion of the elongate workpiece (W) to the working zone of the machine when the precession drive means (52) has precessed the second platen (40) so that it is no longer performing a rotary forging operation on the workpiece (W) in the working zone.