GB2030819A - Improvements in or relating to oscillatory forming equipment - Google Patents

Abstract

The resonator and vibrator of an oscillatory material-forming apparatus, for instance a vibratory metal-drawing machine, are assembled tightly together in compression by a clamp which bears inwardly upon them. In apparatus comprising a radial resonator (10) with vibrator units (13) mounted upon it at diametrically-opposite points, the clamp (16) may bear upon these two units to urge them diametrically towards each other. The invention also includes an arrangement of supports to hold the resonator steady against drawing loads, the contact between the resonator and these supports being of small area to minimise dissipation of vibratory energy, and allowing some freedom of movement in a planar parallel to that of the radial vibrations so as to be able to accommodate small misalignments. <IMAGE>

Description

SPECIFICATION Improvements in or relating to oscillatory forming equipment This invention relates to the forming of materials by oscillatory techniques and in particular to the design of high intensity resonators, such as are used in the application of ultrasonic or other high-frequency energy to plastic deformation techniques.

Such techniques mainly use three modes of vibration, viz. radial, torsional and longitudinal, either singly or in combination, and the essential elements of the equipment are a transducer to generate the vibrations and a resonator to vibrate in response to them and transmit the vibrations to work through a die or other forming device that may be held by the resonator or be part of it. The connection between the transducer and the resonator usually includes a horn or other concentrating device to help maximise the transmission of the vibrations from the one to the other. A conventional assembly of these elements comprising transducer 1, matching horn 2 and resonator 3 is shown diagrammatically in Fig.

1; such a geometry could be expected to set up some form of radial vibration in resonator 3, and these vibrations would then be imparted to a die when located in the central cavity 4.

Very positive joints must be achieved between the elements of such an assembly. In practice this requires that both surfaces of a pair of adjoining elements must be geometrically flat and smooth. During operation, a compressive stress must be maintained across the interface and this must be high enough to prevent separation of the surfaces when oscillatory forces are transmitted across them to and from the load. The conventional means of coupling the elements of such an assembly, as Fig. 1 illustrates, is a screwed stud 5 located in a clearance running through the middle of the assembled parts. Such means of connection have been found to have two serious disadvantages.First, such axial connection results in a pressure differential across the interfaces of adjacent elements, leaving the periphery of the interface under a lower stess than the central region closest to the cavity containing the stud. Second, changing of the resonator requires the stud to be unscrewed and then reconnected and carefully tightened, which tends to be a laborious process.

According to the present invention the resonator and vibrator of an oscillatory materialforming apparatus are held in assembly in use by clamping means bearing upon the assembly from opposite ends and lying exterior to the assembled parts. The clamping force may be hydraulic, and the clamp may include resilient means which bias the clamp to open, thus releasing the components, when the hydraulic force is relaxed. The resilient means may be incorporated in rods or other guidance members which also serve to maintain proper alignment of the clamp and/or the assembled parts.

The invention applies particularly to a clamp for holding together an assembly of a radial resonator and a pair of units each comprising a transducer and a connecting horn, the two units making contact with the resonator at diametrically-opposite points. The clamp may comprise a frame to surround the assembly, and two opposite sides of the frame may be adapted to co-operate with the two horn/ transducer units to bear against them and urge them towards each other, thus putting the entire oscillatory assembly into compression.

Where the assembly is to hold a die through which material is to be drawn while the resonator and die are in radial vibration, the means for holding the resonator and die steady against the drawing loads may comprise at least three substantially spherical stop members mounted on the frame of the apparatus, symmetrically spaced around the drawing axis and so that the dbwnstream face of the resonator and/or die bears against them when under drawing load. There may also be a resiliently-loaded mechanism to bear against the vibratable parts of the apparatus so as to lift the resonator and/or die clear of the stops when drawing is not taking place.

The apparatus will now be described, by way of example, with reference to the further accompanying drawings in which: Figure 2 is a diagrammatic elevation of apparatus according to the invention, and Figure 3 is a more detailed section through another apparatus, taken in a plane radial relative to the drawing axis. The Figure shows half of the apparatus, from one periphery to the axis; the other half, from the axis to the opposite periphery, is symmetrical.

Fig. 2 shows a radial resonator 10 having a central cavity 11 to receive a radial die (not shown). Flats 1 2 are formed on the outer rim of resonator 10 at diametrically-opposite points, to receive the flat noses of vibratory horns 1 3. The divergent outer ends 1 4 of these horns are adapted to contain or be attached to vibratory transducers, and transverse flanges 1 5 are fixed to the horns.

According to the invention resonator 10 and horns 1 3 are assembled together, with tight and even contact across the interfaces of flats 1 2 and the noses of the horns, by a frame 1 6 external to the parts concerned. The frame comprises parallel side members 1 7 joined by end members 1 8. Hydraulic rams 19, powered from a common source 20, are mounted opposite each other, one on each of side members 17. The pistons 21 of these rams, which are hollow to give clearance to the ends 1 4 of the horns, bear against flanges 1 5 to urge the assembly together when source 20 is operating.Pistons 21 are also joined by linkages comprising a rod 22 and spring 23, the spring acting to urge pistons 21 apart, thus releasing the resonator from the horns, whenever source 20 is shut off.

Also, when positioned as shown in Fig. 2, rods 22 may act as guides to hold resonator 10 in position so that its centre 24 lies on the intended transverse axis 25 of the horn/resonator assembly.

In typical apparatus where the resonator is to carry a die of d" II diameter, and is vibrated by two diametrically-opposed horns each 2 inches in diameter, it is likely that a minimum value of about 4 tonf will be required to ensure that contact is maintained at the horn/die interface during use. With the kind of frame and hydraulic equipment shown in Fig. 2, it has been found that sufficient hydraulic pressure can be generated by a simple hand-operated pump, and the clamping pressure maintained for several hours using a close tolerance "holding" valve. While there are clear advantages in generating the necessary forces hydraulically, it will also be apparent that other methods of generating the compressive clamping force might be suitable in certain cases, for example mechanical methods using for instance a cam or external screw.

In the more detailed view of an apparatus according to the invention, shown in Fig. 3, parts corresponding to any shown in Fig. 2 are indicated by the same reference numerals.

The apparatus shown in Fig. 3 is intended for the horizontal drawing of bar, rod or like stock, and the horizontal axis of drawing (which passes through point 24 shown in Fig.

2) is indicated by numeral 30. Resonator 10 is of stepped section, and the die (not shown) fits within the reduced-depth central cavity 11. As in Fig. 2, the flat nose of horn 13 butts against a flat face 1 2 formed on the outer circumference of resonator 1 0. In place of the diagrammatic rams 1 9 and flanges 1 5 shown in Fig. 2 an annular flange 31, projecting from the outer surface of horn 1 3 at a region 32 of vibratory node, is fastened by bolts 33 to a corresponding flange 34 of an annular unit 35 which includes an annular cylinder 36 in which slides an annular piston 37.Fluid within cylinder 36 is driven by pump 20, and piston 37 on its outward stroke bears against side member 1 7 of frame 16 to urge the noses of horns 1 3 against flats 12, thus creating the positive contact between these parts that is necessary for the efficient transmission of vibrations from the transducers to resonator 10. When a vibratory drawing operation ends, and it is desired to disassemble the resonator from the horns, pump 20 is turned off and the rod-and-spring linkages 22/23 (shown in Fig. 2, but not in Fig. 3) ease the pistons 37 back into their cylinders 36.

The most massive member of frame 1 6 is a plate or wall 39 against which resonator 10 is urged into contact while drawing is taking place. Wall 39 is formed with a central cavity 40 to allow clearance for the drawn product, and the contact between wall 39 and resonator 10 during use is made through a plurality of stop members in the form of balls 41 mounted in recesses 42 in the upstream face 43 of wall 39, and equispaced around drawing axis 30. The distance by which each ball 41 lies proud of face 43 can be varied by adjustment of screws 44. Balls 41 make contact with downstream face 45 of resonator 10 and the nature of the contact has two advantages in particular.First, rolling is possible between balls 41 and face 45, thus allowing resonator 10 readily to make very slight transverse movements during operation, in response for instance to transient misalignments. Second, the small total area of contact between resonator 10 and balls 41 minimises the dissipation of vibratory energy from the transducers to wall 39 during operation. However if such contact were to be maintained and the transducers were to continue vibrating once the drawing load had ceased, the transmission of energy across the then lightlyloaded interface between balls 41 and face 45 could be harmful, resulting in severe heating and possible damage to both components.

For this reason at least three support members 50, equispaced around axis 30 are mounted in wall 39. Each member 50 comprises a compression spring 51 surrounding a column 52. Springs 51 bear upon the face 53 of a flange 54 to which annular units 35 are attached. Springs 51 yield to the drawing force, allowing faces 45 to meet balls 41, but when the drawing force is relaxed springs 51 lift flange 54 so that the resonator, with its attached horns and transducers, lies clear of balls 41 as shown in Fig. 3. In addition to providing location axes for springs 51, columns 52 also pass with slight clearance through holes 55 in flange 54, thus providing general radial location for resonator 10 and attached parts.

Claims (8)

1. Oscillatory material-forming apparatus comprising a resonator and a vibrator held in assembly in use by clamping means bearing upon them from opposite ends and lying exterior to them.

2. Apparatus according to Claim 1 in which the clamping means are hydraulically operated.

3. Apparatus according to Claim 1 ir.

which the clamping means include resilient means which bias the clamping means to open, thus releasing the resonator and vibrator, when the force of the clamping means is relaxed.

4. Apparatus according to Claim 1 in which the resonator is a radial resonator and in which the vibrator comprises a pair of units each including a transducer and a connecting horn, the two units making contact with the resonator at diametrically-opposite points.

5. Apparatus according to Claim 4 in which the clamping means comprise a frame to surround the assembly of resonator and vibrator, and in which each of two opposite sides of the frame is adapted to co-operate with one of the units so as to bear against it and urge the two units diametrically towards each other, thus putting the assembly into compression.

6. Apparatus according to Claim 4 in which the resonator is adapted to hold a die through which material may be drawn while the resonator and die are in radial vibration, and including means to hold the resonator and die steady against drawing loads, these means comprising at least three substantially spherical stop members mounted on the frame of the apparatus, symmetrically spaced around the drawing axis and so that the downstream face of the resonator and/or die bears against them when under drawing load in a manner that permits relative rotation.

7. Apparatus according to Claim 6 including a resiliently-loaded mechanism to bear against the vibratable parts of the apparatus so as to lift the resonator and/or die clear of the stop members when drawing is not taking place.

8. Apparatus according to Claim 1, substantially as described with reference to the accompanying drawings.