GB2059536A

GB2059536A - Ultrasonic Cleaning

Info

Publication number: GB2059536A
Application number: GB8022491A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-07-16
Filing date: 1980-07-09
Publication date: 1981-04-23
Also published as: FR2461551A1; IT8085583A0; IT1141875B; DE3026510A1

Abstract

In a method and apparatus for the cleaning of machined workpieces, for example the removal of drill shavings and burrs which remain attached, the workpiece, e.g. tube 8, is clamped between two clamping elements 9, 10 in free air, and ultrasonic vibrations from emitter 11 are applied to the assembly. In a preferred arrangement, one of the clamping elements 9 is secured in resilient manner 9a on a machine structure, and the other clamping element 10 is connected by a vibration source 11 to an actuator, such as a fluid-operable ram 12, 13, mounted on the machine structure. An alternative arrangement is also described. <IMAGE>

Description

SPECIFICATION Ultrasound Cleaning Method and Apparatus This invention relates to the cleaning and deburring of workpieces by the use of vibration at ultrasonic frequency.

It is known to use ultrasound in industrial technology to permit, amongst other applications, very complete cleaning of tooled workpieces, and the unblocking of very fine tubes by clearing of detritus. Hitherto this has been obtained by immersion of the workpiece in a liquid serving as a wave-conducting intermediary between the workpiece and an emitter of ultrasound vibrations, the bulk of the liquid ensuring a certain degree of thermal equilibrium by absorbing heat generated in the workpiece.

Known installations for such cleaning in a liquid medium have the inconvenience of being heavy and bulky, and consequently of necessitating a relatively high power of vibration, which in turn calls for an ultrasound emitter which has a high output power and is consequently costly. Furthermore, it is necessary to carry out rinsing and drying of the workpieces after treatment.

It is the object of the invention to provide a method and apparatus, for the treatment of a workpiece with ultrasound, which eliminates the use of liquid as a transmitting medium.

According to the present invention a method of removing unwanted material, such as shavings and burrs, from a machined workpiece comprises the steps of clamping the workpiece, in air, between a first clamping element and a second clamping element, and applying ultrasonic vibrations to one of said clamping elements to cause the assembly of clamping elements and workpiece to vibrate at ultrasonic frequency. The workpiece is held in free air, without the use of any intermediary liquid medium.

Further according to the invention, apparatus for use in carrying out this method comprises a machine structure, a first clamping element mounted on said machine structure, a second clamping element carried by the machine structure for movement towards and away from the first clamping element, and a source of ultrasonic vibrations coupled to one of said clamping elements. The other of the clamping elements advantageously receives the vibrations both through the machine structure and through the workpiece, and preferably the mass of the other clamping element is selected such that it may enter into resonance with the one clamping element, for greater efficiency of operation and a minimum of resilient constraint for the workpiece in its movement.

In the method of the invention, the action of the ultrasonic vibrations on the workpiece is much more intense than occurs with a liquid medium, as a result of which the period of treatment can be made relatively very short, particularly as the workpiece treated in free air may tend to heat up rapidly. However, even a short period of such treatment is sufficient to break the connection between shavings, burrs and the like and the main body of the workpiece, so that substantially instantaneous cleaning is obtained.

With workpieces machined in very ductile metals, e.g. non-ferrous, the removal of shavings and burrs is commonly relatively slow with the conventional liquid-medium vibration methods, but the method and apparatus of the invention eliminates them rapidly, even at the interior of a tube.

The method and embodiments of the apparatus of the invention are hereinafter particularly described with reference to the figures of the accompanying drawings, wherein: Figs. 1 and 2 are sections showing a metal plate respectively during drilling of a hole, and after withdrawal of the drill; Figs. 3 and 4 are sections showing a metal plate respectively during punching of a hole, and after withdrawal of the punch.

Fig. 5 is a side elevation of a workpiece held in a first position between two clamping elements of the apparatus; Fig. 6 is a side elevation of the workpiece held in a second position between two clamping elements of the apparatus; Fig. 7 is a side elevation to show a manner of holding a workpiece of irregular shape between the clamping elements; Fig. 8 is a schematic perspective elevation of a first embodiment of apparatus; Fig 9 is a schematic plan view, with parts shown in section, of portions of a second embodiment of apparatus used in the production of the workpiece of Figs. 5, 6 and 8; Fig. 10 is a schematic side elevation, with parts shown in section, of the second embodiment of apparatus.

Fig. 1 shows a plate 1 of ductile metal in which a drill bit 2 makes a hole. The rotation of the drill bit causes the formation, on the upper side of the plate, of helicoidal shavings such as 3, and at the point of emergence of the drill bit small burrs such as 4. These shavings or burrs do not necessarily fall off, of their own accord, at the termination of the drilling operation, and tend to be retained on the workpiece by a minuscule stalk of fissured and embrittled metal, as seen in Fig. 2.

Fig. 3 shows an operation of punching of a plate 5. This type of operation does not entirely eliminate the material which occupied the position of the hole, but causes some of it to be driven downwardly under the action of the punch 6, some of the metal being carried along with the punch, due to the tearing of the metal, defects in the homogeneity of the metal, and imperfections of the surface, the effect becoming greater as the punching pressures used become higher. This dragging of the metal also causes burrs such as 7 where the punch emerges, as seen in Fig. 4.

It is possible to clean the metal plate, of Figs. 2 and 4, of shavings and burrs by subjecting the plate to ultrasonic vibration which ruptures the connections coupling the shavings and burrs to the workpiece.

In Figs. 5, 6 and 8 there is shown, by way of example, a workpiece in the form of a partially curved tube 8 intended to serve as a sprinkler element in a domestic garden sprinkler. The holes 8', serving for passage of water, are obtained by punching or drilling them all at the same time after curving of the tube. This drilling or punching results in shavings and burrs at each hole.

In Fig. 5 the tube 8 is placed lengthwise between two clamping plates 9 and 10. The plate 9 is fixed to the structure (not shown) of the machine, but its connection with the structure is through a resiliently deformable element so that it is not absolutely rigid and it can oscillate in resonance at the frequency of the ultrasound emitter. The other plate 10 is fast with a rod 1 Oa submitted to magnetostriction resulting from the operation of the emitter and thus transmits the ultrasonic vibrations to the tube 8. The vibration causes the shavings and burrs to take up a pendular movement which breaks their connection, and they become detached and fall onto the plate 9.

Fig. 6 shows the tube 8 placed flat between the plates 9 and 10, and the operation and result are otherwise identical.

Fig. 7 shows the treatment of a workpiece 14 of unusual shape, which is clamped between auxiliary wedge elements 1 5 and 16.

In this particular case of a sprinkler tube, the elimination of burrs even at the interior of the tube permits the avoidance of any risk of stopping up of the sprinkler holes when the water supply is commenced in use.

Fig. 8 shows, by way of example, a machine comprising at its lower part, the two plates 9 and 10 of Figs. 5, 6 and 7. The upper movable plate 10 is fast with the output rod 1 Oa of an ultrasonic emitter 1 1 mounted by a shaft 1 a on a piston 12 movable in a cylinder 13 of a pneumatic ram mounted by struts 13a on a frame structure 1 3b of the machine. Upon application of fluid under pressure at an inlet 1 3c, the emitter 1 1 and plate 10 are moved in the direction of arrow F to urge the plate 10 against the workpieces 8, whereupon the emitter 11 is put into operation for a short period. The emitter is then lifted again, by pressure introduced at 1 3d, and the workpiece is removed.The lower plate 9 is mounted, by a resilient pad 9a, on the structure of the machine so as to be able to vibrate.

Referring to Figs. 9 and 10, the modified apparatus is used for the cleaning and de-burring of a workpiece again in the form of a perforated arched aluminium tube 8a. To form the tube 8a with its arched central portion, a straight piece of tube is placed with its ends engaged on two coaxial mandrels 17, 18 which are respectively movable axially in the direction of the arrows "A" and "B", by any convenient shifting means such as a hydraulic or pneumatic ram mounted on the machine frame and carrying the mandrel. This movement permits engagement and disengagement axially with the tube. Then a male die 19, with curved die face 20, is moved horizontally by a ram 19a towards and beyond the axis X-X of the tube on the mandrels to form the curved portion of the tube as seen in Fig. 9 against a female die D.Thereafter, a multiple punching or drilling assembly D2 is moved in horizontally in the direction of the arrow G by a ram D' to form small openings in the curved tube, along the various axes C,C,C The die 19 and the punching or drilling means D2 are then withdrawn, leaving the curved perforated tube on the mandrels 17, 18. A hydraulic or pneumatic ram 21 having a cylinder 22 mounted on a frame structure S of the machine is then operated to cause its piston 23 to lower and drive down a rod 24 carrying a pusher block 25 which abuts against one end of the tube 8a and clamps it against the mandrel 17 to avoid unwanted audio frequency vibration occurring between the tube and mandrel 17.At the other end of the tube 8a, a similar ram 26 is operated to cause its piston 27, with its rod 28 carrying an ultrasound generator 29, to move downwardly until the axiallyvibratable output rod 30 of the generator abuts against the tube 8a and clamps it against the mandrel 18. The mandrel 18 is resiliently mounted on the structure S. Ultrasound is then applied for a very short period, e.g. of the order of one second. In a practical example, the frequency of vibration is within the range 16,000 to 20,000 Hz., applied for example by a machine supplied by Branson and operating at a rate of 400 watts.

The pressure applied by the plates, the amplitude of oscillation, the mass of the workpiece, and the position thereon of the zones to be de-burred are factors which need to be taken into consideration empirically for each specific application.

The machine is particularly advantageous in a production line in which the workpiece to be dealt with is always the same, by reason of the rapidity of the operation which permits the immediate production of clean workpieces.

Claims

1. A method of removing unwanted material, such as shavings and burrs, from a machined workpiece comprising the steps of: (i) clamping the workpiece, in air, between a first clamping element and a second clamping element, (ii) applying ultrasonic vibrations to one of said clamping elements to cause the assembly of clamping elements and workpiece to vibrate at ultrasonic frequency.

2. Apparatus for the treatment of a machined workpiece, for the removal therefrom of unwanted material such as shavings and burrs, comprising: (a) a machine structure (b) a first clamping element mounted on said machine structure (c) a second clamping element carried by said machine structure for movement towards and away from the first clamping element, and (d) a source of ultrasonic vibrations coupled to one of said clamping elements.

3. Apparatus, as claimed in claim 2, wherein said first clamping element is resiliently mounted on said machine structure, and wherein said second clamping element is connected by said vibration source to a movable actuating means mounted on the machine structure.

4. Apparatus, as claimed in claim 3, wherein said actuating means is a fluid-operable ram.

5. The method, as claimed in claim 1, substantially as described herein with reference to the accompanying drawings.

6. Apparatus substantially as described herein with reference to Figs. 5-8, or Figs. 9 and 10, of the accompanying drawings.

7. Workpieces treated in accordance with the method claimed in either of claims 1 and 5.