GB2325874A

GB2325874A - Ultrasonic cutting device

Info

Publication number: GB2325874A
Application number: GB9711537A
Authority: GB
Inventors: Francis Frederick Hamil Rawson
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-06-05
Filing date: 1997-06-05
Publication date: 1998-12-09
Anticipated expiration: 2017-06-05
Also published as: GB2325874B; GB9711537D0

Abstract

An ultrasonic cutting device 12 comprises a plurality of disc or annular shaped cutting elements 16 joined together at circumferential points 18 to form an elongate, planar device having a mid-line M. Each cutting element has an inner radius R1 and an outer radius R2 terminating in a circumferential cutting edge 22. One end of the cutting device is provided with a drive face 20 which is connected to a source 14 of ultrasonic vibrations.

Description

Title: Ultrasonic Cutting Device Description of Invention This invention relates to improvements in cutting devices, in particular to cutting devices which are operative at high (ultrasonic) frequencies.

Ultrasonic cutting devices using blades which are substantially rectangular with various openings cut in them are well known, the blades being known as guillotine blades. However, such blades suffer from significant disadvantages as they can support a large number of ultrasonic modes. This makes it difficult to predict which mode or modes will be established when the device is used and therefore how it will actually operate.

It is an object of the invention to provide an alternative form of ultrasonic cutting device which does not suffer from the above described disadvantage to the same extent.

According to a first aspect of the present invention there is provided a cutting device comprising a generally planar cutting member comprising: (a) a plurality of generally annular portions joined together at circumferential points to form a mid-line of the cutting member; (b) a driving face at one end of the cutting member on the mid line to be attached to a source of ultrasonic vibrations, and (c) a cutting edge extending circumferentially of each annular portion of the cutting member on one side of the mid-line.

The invention provides the advantage that the cutting member can support fewer ultrasonic modes than prior art cutting members.

Preferably the cutting member further comprises a second driving face at the other end of the cutting member on the mid-line to be attached to a second source of ultrasonic vibrations.

The or each driving face may be substantially perpendicular to and centred on the mid-line of the cutting member, but may extend and any convenient angle thereto.

The cutting edge may subtend an angle on each annular portion of between 450 and 160 .

The cutting edge on each annular portion may be V-shape in crosssection. Alternatively, on each annular portion two parallel cutting edges may be provided by machining a V-shape or U-shape groove into the circumference.

Preferably each annular portion has an inner radius R1 and an outer radius R2 and the values of the inner radius Rl and the outer radius R2 are in approximate accordance with the equation K(R, + R2) = 2N. The approximation is preferably to within plus/minus 5%.

According to a second aspect of the present invention there is provided a cutting mechanism comprising a cutting device according to the first aspect of the invention and an ultrasonic device attached to one or both drive surfaces on the ends of the cutting member.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which: FIGURE 1 illustrates a cutting device according to the invention; FIGURE 2 is a cross section of the cutting device of Figure 1 along line A-A; FIGURE 3 is a cross-section of an alternative cutting device according to the invention, and FIGURE 4 illustrates an alternative form of cutting device according to the invention.

Referring to Figure 1, a cutting mechanism 10 comprises a cutting device 12 in the form of a cutting member, and a source of ultrasonic vibrations 14 of well known kind.

The cutting member 12, which is generally planar, comprises a plurality, in this example three, of annular portions 16, joined together at circumferential points 18 to form a mid-line M of the cutting member.

Each annular portion 16 has an inner radius R1 and an outer radius R2, as best illustrated in Figure 2. Preferably the values of the inner radius Rl and the outer radius R2 are in approximate accordance with the equation: K(R, + R2) = 2N.

Where K is the wave number and N is an integer. The approximation is preferably to within plus/minus 5%.

Where the cutting member 12 is formed from an alloy of aluminium with 4% copper, appropriate dimensions are R1 = 50mm and R2 = 150mm, with the ultrasonic source 14 operating at a frequency of 18.2kHz.

A drive face 20 is provided at one end of the cutting member 12, the drive face 20 being substantially perpendicular to and centred on the mid-line M.

The drive face 20 may be a flat planar surface or slightly curved. The source of ultrasonic vibrations 14 is attached to the drive face 20.

The cutting member 12 further comprises a cutting edge 22 which extends circumferentially of each annular portion 16 to one side of the mid-line M, in this example below the mid-line M. The cutting edge 22 may extend along the entire circumferences of the annular portions 16 on the one side of the midline M, such that it is continuous. Alternatively, the cutting edge 22 may only extend around part of the circumference of each annular portion 16 to the one side of the mid-line M, such that it is not continuous.

Each annular portion 16 may be tapered inwardly in cross-section towards the circumference as shown in Figure 2. The form of the taper may however be different, for example as shown in Figure 3. The cutting edge 22 is provided by appropriate finishing of the circumference. This may take the form of for example a coating or heat treatment, to harden the cutting edge, or any number of well known techniques.

In the alternative the circumference may be V-shape or U-shape in cross-section to provide two parallel cutting edges (not shown). These may be treated appropriately as described above.

Referring now to Figure 4, an alternative form of cutting mechanism 30 is illustrated, with parts common with the mechanism 10 being like referenced.

The cutting member 12 is substantially the same as that in the mechanism 10, however, it comprises a second drive face 20 at the other end of the member 12 to the first drive face. A second source of ultrasonic vibrations 14 is attached to the second drive face. The two sources of ultrasonic vibrations 14 are driven in...., which may be accomplished by a single generator, operating from one input face, or from two generators, connected to spaced input faces of the mechanism.

Where two generators are used, preferably the generators are powered from a single supply, to ensure operation thereof in synchronism.

It is to be appreciated that whilst in the embodiment illustrated in Figure 4, the two forces are applied to the mechanism in opposite directions on the same longitudinal axis, this is not necessary, and the input on one or both of the outermost annular portions 16 may be displaced from said axis, eg by 90 , as is shown in dotted lines in Figure 4.

Alternatively, a single driver may be applied to a central one of the annular cutting members, which may if desired be welded together with their centres lying in an arc.

It has been found that by the use of the invention, vibrations produced by the generator are transmitted to the cutting members, the vibrations emanating primarily at the periphery of the cutting member, said vibrations being generally radially inwardly and outwardly, in a pulsating manner, and lying generally within a plane containing the annular cutting member.

Additionally however it has been determined that by the appropriate positioning of the drive member in connection with the cutting discs, harmonic vibrations may be produced by an interference process which may appear as vibrations of the cutting edge in a direction extending at right angles to the plane containing the cutting member.

The features disclosed in the foregoing description, the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a classer group of substances or compositions, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A cutting device comprising a generally planar cutting member comprising: (a) a plurality of generally annular portions joined together at circumferential points to form a mid-line of the cutting member; (b) a driving face at one end of the cutting member on the mid line to be attached to a source of ultrasonic vibrations, and (c) a cutting edge extending circumferentially of each annular portion of the cutting member on one side of the mid-line.

2. A cutting device according to claim 1 wherein the cutting member further comprises a second driving face at the other end of the cutting member on the mid-line to be attached to a second source of ultrasonic vibrations.

3. A cutting device according to claim 1 or 2 wherein the or each driving face is substantially perpendicular to and centred on the mid-line of the cutting member.

4. A cutting device according to any one of the preceding claims wherein the cutting edge subtends an angle on each annular portion of between 45 and 160 .

5. A cutting device according to any one of the preceding claims wherein the cutting edge on each annular portion is concave or convex.

6. A cutting device according to any one of claims 1 to 5 wherein on each annular portion two parallel cutting edges are provided by machining a V-shape or U-shape groove into the cutting edges.

7. A cutting device according to any one of the preceding claims wherein each annular portion has an inner radius Rl and an outer radius R2 and the values of the inner radius R1 and the outer radius R2 are in approximate accordance with the equation K(Rl + R2) = 2N.

8. A cutting device according to claim 7 wherein the approximation is to within plus/minus 5%.

9. A cutting mechanism comprising a cutting device according to any one of the preceding claims and an ultrasonic device attached to one or both drive surfaces on the ends of the cutting member.

10. A cutting device according to any one of the preceding claims wherein the frequency of vibrations of the source lies in the range 15 KHz to 200 KHz.

11. A cutting device substantially as herein before described with reference to the accompanying drawings.

12. Any novel feature or novel combination of features as herein defined and/or shown in the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. A cutting device comprising a generally planar cutting member comprising: (a) a plurality of generally annular portions joined together at circumferential regions, affording a mid-line of the cutting member; (b) a driving face at one end of the cutting member to be attached to a source of ultrasonic vibrations; and (c) a cutting edge extending circumferentially of each annular portion of the cutting member on one side of the mid-line.

2. A cutting device according to claim 1 wherein the cutting member comprises a second driving face at the other end of the cutting member to be attached to a second source of ultrasonic vibrations.

3. A cutting device according to one of claims 1 and 2 wherein the or each driving face is substantially perpendicular to and centred on the mid-line of the cutting member.

4. A cutting device according to one of claims 1 and 2 wherein each driving face extends at an angle to the mid-line.

5. A cutting device according to any one of the preceding claims wherein the cutting edge subtends an angle on each annular portion of between 45" and 1600.

6. A cutting device according to any one of the preceding claims wherein the cutting edge on each annular portion is V-shape in cross-section.

7. A cutting device according to any one of claims 1 to 5 wherein on each annular portion two parallel cutting edges are provided.

8. A cutting device according to any one of the preceding claims wherein each annular portion has an inner radius R1 and an outer radius R2 and the values of the inner radius and the outer radius are in approximate accordance with the equation K(R1 + R2) = 2N, wherein K is the wave number and N is an integer.

9. A cutting device according to claim 8 wherein said approximation is accurate to within +/- 5%.

10. A cutting mechanism comprising a cutting device according to any one of the preceding claims and an ultrasonic device attached to one or both drive surfaces on the ends of the cutting member.

11. A cutting device constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.