AU2023202476B1

AU2023202476B1 - Apparatus for testing blade sharpness

Info

Publication number: AU2023202476B1
Application number: AU2023202476A
Authority: AU
Inventors: Peter Dowd
Original assignee: Anago Ltd
Current assignee: Anago Ltd
Priority date: 2023-04-24
Filing date: 2023-04-24
Publication date: 2023-07-06
Anticipated expiration: 2043-04-24

Abstract

It is known to test the sharpness of a blade as it makes a cut through a medium by measuring the amount of force needed to make the cut for each portion of the blade along its length. A problem is that known devices presuppose that the blade's cutting edge extends in a straight line, and this can mean that determinations are inaccurate when the blade is curved. An apparatus for testing blade sharpness comprises: means adapted to determine curvature profile of a curved cutting blade; drive means adapted to cause the blade to progressively cut through a test medium and, as the cutting occurs, to adjust the angle of the blade with respect to the medium commensurate with the blade's curvature; means adapted to determine the amount of force used to cause the blade to cut through the medium for each of multiple portions of the blade; means adapted to determine the sharpness of the multiple portions based on the force determinations; and means to report blade sharpness for each of the multiple portions.

Description

TITLE

Apparatus for testing blade sharpness.

FIELD OF INVENTION

A preferred form of the invention relates to a device for testing the sharpness of a blade.

BACKGROUND

It is known to test the sharpness of a blade as it makes a cut through a medium. This is done by measuring the amount of force needed to make the cut for each portion of the blade along its length. A problem is that known devices presuppose that the blade's cutting edge extends in a straight line, and this can mean that blade sharpness determinations are inaccurate when the blade is curved (eg arced). It is accordingly an object of a preferred embodiment of the invention to go at least some way towards addressing this problem. However, it should be understood that the object of the invention per se is not so specific and is simply to provide the public with a useful choice.

DEFINITIONS

The term "comprises" or "has", if and when used in this document in relation to one or more features, should not be seen as excluding the option of there being additional unmentioned features. The same applies to derivative terms such as "comprising" and "having".

Orientational terms used in relation to the apparatus the subject of the invention, such as those conveying upwards or downwards positions or movement, apply to the normal in use disposition of the apparatus.

SUMMARY OF THE INVENTION

According to a first aspect, the invention is an apparatus for testing blade sharpness comprising: * means adapted to determine curvature profile of a curved cutting blade having a cutting edge; • drive means adapted to cause the blade to progressively cut through a test medium and, as the cutting occurs, to adjust the angle of the blade with respect to the medium commensurate with the blade's curvature;

" means adapted to determine the amount of force used to cause the blade to cut through the medium for each of multiple portions of the blade; and * means adapted to determine the sharpness of the multiple portions based on the force determinations; and • means to report blade sharpness for each of the multiple portions.

Optionally the test medium comprises a strip.

Optionally the drive means causes angular adjustment of the blade with respect to the strip such that each portion of the cutting edge is substantially at right angles to the face of the strip as that portion cuts the strip.

Optionally the drive means comprises an X-axis drive, a Y-axis drive, and a rotational-axis drive and these are arranged to cause adjustment of the position and angle of the blade.

Optionally the X-axis drive and the Y-axis drive control the position, and linear movement, of the blade with a degree of precision of±0.1mm.

Optionally the amount of force used to cause the blade to cut through the strip is determined for approximately each 0.5mm of the length of the cutting edge.

Optionally the amount of force used to cause the blade to cut through the strip is determined for approximately each 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm and/or 5mm of the length of the cutting edge.

Optionally the drive means are adapted to move the blade at a speed of approximately 50mm per second.

Optionally the plane of the blade is centred ±5mm on, and substantially at right angles with respect to, the face of the strip.

Optionally the means adapted to determine the curvature of the cutting edge of the blade comprises a blade scanner.

Optionally the strip is adapted to be rolled onto a feeder spool and arranged to pass through a sensor and onto a receiver spool.

Optionally the strip is tension adjusted by tightening or loosening the feeder spool with respect to the receiver spool.

Optionally the amount of force used to cause the blade to cut through the medium is determined as the blade is moved through the medium from tip to heel, and subsequently moved through the medium from heel to tip.

Optionally the amount of force used to cause the blade to cut through the medium is determined as the blade is moved through the medium from heel to tip, and subsequently moved through the medium from tip to heel.

According to a further aspect, the invention is an apparatus for testing blade sharpness comprising: 0 a blade scanner adapted to determine curvature profile of a curved cutting blade having a cutting edge; • an X-axis drive and a Y-axis drive adapted to control the position, and linear movement, of a clamp adapted to hold the blade; • a rotational-axis drive adapted to control the angle, and angular movement, of the blade with respect to a mesh strip; * the X-axis drive, Y-axis drive, and rotational-axis drive adapted to cause the blade to progressively cut through the strip and, as the cutting occurs, to adjust the angle of the blade with respect to the strip commensurate with the blade's curvature; * a force sensor adapted to determine the amount of force used to cause the blade to cut through the strip for each of multiple portions of the blade, wherein measurements along the length of the blade are made where each portion measured is a minimum of approximately 0.5mm; * means adapted to determine the sharpness of the multiple portions based on the force determinations; and • means to report blade sharpness for each of the multiple portions.

DRAWINGS

Some preferred embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, of which

Figure 1 is a perspective view of a blade testing device;

Figure 2 shows a selection of knives that are suitable for testing with the device;

Figure 3 shows a further selection of blade types that are suitable for testing with the device;

Figure 4 illustrates a profile scanner forming part of the device when scanning a knife blade;

Figure 5 is a side view of a strip of test medium illustrating the movement sequence of the blade as it approaches and passes through the medium;

Figure 6 is a side view of the test medium illustrating an alternative movement sequence of the knife as it approaches and passes through the medium;

Figure 7 is a side view of the medium with a tip of the knife about to pass through the medium; and

Figure 8 is a screen display graphically illustrating the results of a blade sharpness test using the device.

DETAILED DESCRIPTION

Referring to Figure 1, the device 1 comprises an X-axis drive 2, a Y-axis drive 3, and a rotational-axis drive 4. Secured to the rotational-axis drive 4 is a knife clamp 5. The clamp 5 preferably comprises a rigid holder for firmly grasping the handle of a knife 6 so that its curved blade 7 cantilevers away from the clamp 5.

The device 1 also comprises a blade scanner 8 for scanning the blade to profile its curvature. As part of this, the scanner 8 generates electronic data representative of the curvature.

The device 1 also comprises a force sensor 9 (eg a transducer) for measuring the force required for the blade 7 to cut a test medium. In this example the test medium is a mesh strip 10. The strip 10 is preferably a plastic-coated fabric comprising interwoven strands. Each strand comprises a polyester core coated with PVC. The strip 10 is preferably 20mm wide and 25m long. The strip 10 preferably has the following further characteristics:

Thickness Weight Strip width Mesh hole size Roll length (m) 2 (mm) (g/m ) (mm) (height &

width) (mm)

0.73 ±0.03 420 ±20 20.0 ±0.2 1.5 ±0.1 (H) 25 ±0.2 0.6 ±0.1 (W)

The strip 10 is preferably stored within a temperature range of 5-40° C and, when used for testing blade sharpness, is run within a temperature range of 10-30° C.

As shown in Figure 1, the strip 10 is rolled onto a feeder spool 11 and is arranged to pass through the sensor 9 and onto a receiver spool 12.

The drives 2, 3, 4, scanner 8, and sensor 9 are controlled by computer software routines (algorithms) to obtain, send, analyse, and display information related to sharpness of the blade 7.

To ensure the apparatus performs with accuracy and consistency, calibration is required. The force sensor 9 is calibrated at two points: zero load and 2kg load. The zero load setting is the measure applicable when the strip 10 is hanging limp from the sensor 9 without any tension on it. The 2kg load setting is measured by hanging a calibrated 2kg weight (± 0.01 kg) from the sensor under gravity.

The force sensor 9 is also calibrated before use for the speed of the blade 7 as it progressively moves/cuts through the strip 10. The calibration is done at 50 (± 0.5) mm/second and the average of ten test runs is taken.

The X-axis drive 2 and the Y-axis drive 3 control the position, and linear movement, of the blade 7 on an X (horizontal) axis and on a Y (vertical) axis respectively. The rotational-axis drive 4 controls the angle, and angular movement, of the blade 7 with respect to the strip 10 when in use. More particularly, the rotational axis drive 4 causes the blade 7 to pivot towards and away from the strip 10. Preferably, the X-axis drive 2 and the Y-axis drive 3 control the position, and linear movement, of the clamp 5 and blade 7 with a degree of precision of ±0.1mm each.

The speed of the drives 2, 3 is calibrated by measuring the time required to move the clamp 5 a distance of 100mm along each respective axis. The drives 2, 3, 4 cause the angle of the blade 7 with respect to the strip 10 to be progressively adjusting commensurate with the curvature of the blade 7 at each portion as it cuts the strip 10 respectively.

When in use, the device 1 drives the blade 7 forward and downwards through the strip 10 so that substantially the full length of the blade 7 makes a linear cut down and through the strip 10. The blade 7 is then pulled back through a further section of the strip 10 as it moves further downwards to cause a similar, but reverse direction, linear extension of the cut down and through the strip 10. To facilitate this the handle end of the knife 6 is secured in the clamp 5, and the knife 6 is positioned so that the plane of its blade 7 is centred (±5mm) on, and at right angles with respect to, the face of the strip 10.

A variety of blades each having a different curvature profile are able to be tested by the device 1. These include blades intended to be resharpened by a user when they become blunt, as well as blades that are not intended to be resharpened. Some examples of suitable blade profiles are shown in Figure 2.

Some typical blade types suitable for testing are shown in cross-section in Figure 3, known as a V-edge blade 13, a compound bevel blade 14, an alternative compound bevel blade 15, a convex edge blade 16, a hollow edge blade 17, and a chisel edge blade 18. The same test is applied to all types of knives. Some powered machine blades can be tested using modified clamping mechanisms.

Referring to Figure 4, once the knife 6 is secured in the clamp 5, the profile of the blade 7, for example the profile of the cutting edge of the blade 7, is scanned by the scanner 8. The aim of the test is to determine the performance of the blade 7 in terms of the varying force required to cut through the strip 10 for multiple parts of the blade 7, including where the blade 7 curves, during cutting strokes. The scanner 8 provides curvature profile information representing the varying curvature of the blade 7 being tested, so that the device 1 generates the appropriate motion sequences of the drives 2, 3, 4 to accurately move the blade 7 to measure its performance.

After scanning, the strip 10 is tension adjusted by tightening or loosening the feeder spool 11 with respect to the receiver spool 12. The strip 10 is preferably tensioned to a standard preload of 20 newtons (N), with a preferred degree of variation of +2N and -1N.

Referring to Figure 5, using the information provided by the scanner 8, the drives 2, 3, 4 move the clamp 5 so that the blade 7 cuts through the strip 10 at approximately 50 mm/s so that the portion of the cutting edge in contact with the strip 10 at any one time is at a consistent angle of attack.

For example, the plane of the blade 7 remains vertical (eg remains in or parallel to the X-Y plane), but the angle of the blade 7 in the X-Y plane is adjusted (tilted) as shown in Figure 5 in real time, commensurate with the curvature of the blade 7. This is done so that the portion of the blade's cutting edge in contact with the strip 10 at any one time is always substantially at right angles to the face of the strip 10.

In some embodiments the portion of the cutting edge in contact with the strip 10 may not be exactly at right angles to the face of the strip 10, but preferably it is no more than (±2)off.

The force required to cut each strand of the strip 10 along each portion of the blade 7 is measured by the transducer 9. This force is referred to as 'Cutting Force - Forward' (CFF). This is the force required to cut through the test medium at a given measurement point along the profile of the blade 7 as the blade 7 is moved through the strip 10 from tip to heel of the blade 7. The maximum CFF is preferably 800 grams (g).

Referring to Figure 6, the knife 6 is then removed from the strip 10. The strip 10 is moved clockwise on to the recipient roll 12 exposing a fresh section of strip 10 from the feeder roll 11. The strip 10 is then tension adjusted again, as described above. The blade 7 is forced through the strip 10 about 2mm below the first cut and up to the heel of the blade 7 and the handle of the knife 6. The drives 2, 3, 4 move the clamp 5 so that the blade 7 cuts through the strip 10 at a consistent 90 (±2°)angle of attack as described above, but this time from the heel of the blade 7 to the tip of the blade 7.

The force required to cut through the strip 10 (eg through each horizontal strand thereof) along each portion of the blade 7 is measured by the transducer 9. This force is referred to as 'Cutting Force - Reverse' (CFR). It is the force required to cut through the test medium at a given measurement point along the profile of the blade 7 as it is moved through the strip 10 from heel to tip. The maximum CFR is preferably 800g.

Alternatively, the amount of force used to cause the blade 7 to cut through the medium/strip 10 is determined as the blade 7 is first moved through the medium/strip 10 from heel to tip, and subsequently moved through the medium/strip 10 from tip to heel.

In an alternative embodiment of the invention as illustrated in Figure 7, the device 1 may be used to measure the force required for the tip of the blade 7 only to puncture the strip 10, preferably when the portion of the cutting edge immediately behind the tip is at 900 (±2°) as above.

The amount of force used to cause the blade 7 to cut through the strip 10 is determined for each of multiple portions of the blade 7. For optimal recording of results, it is preferred that measurements along the length of the blade 7 are made for approximately each 0.5mm stretch of the blade's cutting edge, and differences in cutting force of 0.05N are detected. Alternatively, measurements along the length of the blade 7 are made where each portion measured is a minimum of approximately 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm and/or 5mm stretch of the cutting edge.

After the knife 6 is tested, the used portion of strip 10 is rolled clockwise onto the receiver roll 12 exposing a fresh section of strip 10 from the feeder roll 11, ready for the next test with a different knife.

The test force information from the transducer is sent to a suitable processor, for example computer hardware (which may be considered part of the device), and is collated. The measurements of force required by the blade 7 to cut through the strip 10 are preferably represented in tables, for example as follows:

Tip to Heel of Blade (example only)

Distance from Tip (mm) Force (N) 0.5 20.0 1.0 22.1 1.5 22.3 2.0 22.0 2.5 23.5

Maximum force 23.5

Heel to Tip of Blade (example only)

Distance from Heel (mm) Force (N) 0.5 24.7 1.0 24.5 1.5 24.4 2.0 24.6

2.5 24.3

Maximum force 24.7

Plotting the measurement results is optional when calculating the cutting performance of the blade 7. However, a performance curve for tests may represented as shown in Figure 8, where the X axis shows the distance from the tip of the blade in mm, and the Y axis shows the force in Newtons (N) required to cut the strip. 'CFF-Max' represents the maximum 'Cutting Force - Forward' (CFF).

If the results show that the sharpness of the blade 7 is below the preferred level then the knife 6 can be sharpened.

In preferred forms of the invention, movement of the knife by the drives is controlled by software routines which match the angle of attack of the blade with the scanned profile of the blade.

While some forms of the invention have been described by way of example, it should be appreciated that modifications and improvements can be made without departing from the scope of the following claims.

In terms of disclosure, this document envisages and hereby posits any feature mentioned herein in combination with itself or any other feature or features mentioned herein, even if the combination is not claimed.

Claims

1. An apparatus for testing blade sharpness comprising: " means adapted to determine curvature profile of a curved cutting blade having a cutting edge; * drive means adapted to cause the blade to progressively cut through a test medium and, as the cutting occurs, to adjust the angle of the blade with respect to the medium commensurate with the blade's curvature; * means adapted to determine the amount of force used to cause the blade to cut through the medium for each of multiple portions of the blade; " means adapted to determine the sharpness of the multiple portions based on the force determinations; and " means to report blade sharpness for each of the multiple portions.

2. An apparatus according to claim 1, wherein the test medium comprises a strip.

3. An apparatus according to claim 2, wherein the drive means causes angular adjustment of the blade with respect to the strip such that each portion of the cutting edge is substantially at right angles to the face of the strip as that portion cuts the strip.

4. An apparatus according to claim 1, 2 or 3, wherein the drive means comprises an X-axis drive, a Y-axis drive, and a rotational-axis drive and these are arranged to cause adjustment of the position and angle of the blade.

5. An apparatus according to claim 4, wherein the X-axis drive and the Y-axis drive control the position, and linear movement, of the blade with a degree of precision of±0.1mm.

6. An apparatus according to any one of claims 2-5, wherein the amount of force used to cause the blade to cut through the strip is determined for approximately each 0.5mm of the length of the cutting edge.

7. An apparatus according to any one of claims 2-5, wherein the amount of force used to cause the blade to cut through the strip is determined for approximately each 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm and/or 5mm of the length of the cutting edge.

8. An apparatus according to any one of the preceding claims, wherein the drive means is adapted to move the blade at a speed of approximately 50mm per second.

9. An apparatus according to any one of claim 2 (or any one of claims 3-8 when read on at least claim 2), wherein the plane of the blade is centred ±5mm on, and is substantially at right angles with respect to, the face of the strip.

10. An apparatus according to any one of the preceding claims, wherein the means adapted to determine the curvature of the cutting edge of the blade comprises a blade scanner.

11. An apparatus according to claim 2 (or any one of claims 3-10 when read on at least claim 2), wherein the strip is adapted to be rolled onto a feeder spool and arranged to pass through a sensor and onto a receiver spool.

12. An apparatus according to claim 11, wherein the strip is tension adjusted by tightening or loosening the feeder spool with respect to the receiver spool.

13. An apparatus according to any one of the preceding claims, wherein the amount of force used to cause the blade to cut through the medium is determined as the blade is moved through the medium from tip to heel, and subsequently moved through the medium from heel to tip.

14. An apparatus according to any one of claims 1-12, wherein the amount of force used to cause the blade to cut through the medium is determined as the blade is moved through the medium from heel to tip, and subsequently moved through the medium from tip to heel.

15. An apparatus for testing blade sharpness comprising: • a blade scanner adapted to determine curvature profile of a curved cutting blade having a cutting edge; * an X-axis drive and a Y-axis drive adapted to control the position, and linear movement, of a clamp adapted to hold the blade; • a rotational-axis drive adapted to control the angle, and angular movement, of the blade with respect to a mesh strip; 0 the X-axis drive, Y-axis drive, and rotational-axis drive adapted to cause the blade to progressively cut through the strip and, as the cutting occurs, to adjust the angle of the blade with respect to the strip commensurate with the blade's curvature;

* a force sensor adapted to determine the amount of force used to cause the blade to cut through the strip for each of multiple portions of the blade, wherein measurements along the length of the blade are made where each portion measured is a minimum of approximately 0.5mm; • means adapted to determine the sharpness of the multiple portions based on the force determinations; and " means to report blade sharpness for each of the multiple portions.