Knife

Abstract

A knife blade with a back, and a cutting edge with a shoulder, characterised in that the knife blade has a blade profile perpendicular to the blade edge that, starting at the shoulder and moving towards the back, has the following thickness, as ground prior to any polishing or subsequent steps, at the position indicated: at the shoulder a thickness of AA; at about 1/16 from the shoulder a thickness of BB; and at about from the shoulder a thickness of CC; where AA is about 16 to 23 thousandths of an inch (0.41 mm to 0.58 mm); BB is AA plus about 3 thousandths of an inch (0.076 mm); and CC is BB plus about 2 thousandths of an inch. (0.051 mm).

Claims

1. A stainless steel knife blade with a back, and a cutting edge with a shoulder, characterised in that the knife blade has a blade profile perpendicular to the blade edge that, starting at the shoulder and moving towards the back, has the following thickness, as ground prior to any polishing or subsequent steps, at the position indicated: at the shoulder a thickness of AA; at about 1/16 from the shoulder a thickness of BB; and at about from the shoulder a thickness of CC; where AA is about 16 to 23 thousandths of an inch (0.41 mm to 0.58mm); BB is AA plus about 3 thousandths of an inch (0.076 mm); and CC is BB plus about 2 thousandths of an inch (0.051 mm).

2. The knife blade as claimed in claim 1 characterised in that the blade thickness at about from the shoulder is DD; where DD is CC plus about 4 thousandths of an inch (0.102 mm).

3. The knife blade as claimed in claim 2 characterised in that the blade thickness at about from the shoulder is EE; where EE is CC plus about 9 to 20 thousandths of an inch.

4. The knife blade as claimed in claim 3 characterised in that the blade thickness at about from the shoulder is FF; where FF is EE plus about 8 thousandths of an inch or greater.

5. The knife blade as claimed in claim 3 characterised in that the blade is polished after being ground, in this case the polishing reduces the as ground thickness, independently at each specified point, by between about 0 and 1 thousandths of an inch.

6. The knife blade as claimed in claim 2 characterised in that the blade is polished after being ground, in this case the polishing reduces the as ground thickness, independently at each specified point, by between about 0 and 1 thousandths of an inch.

7. The knife blade as claimed in claim 1 characterised in that the blade thickness at about from the shoulder is EE; where EE is CC plus about 9 to 20 thousandths of an inch.

8. The knife blade as claimed in claim 7 characterised in that the blade thickness at about from the shoulder is FF; where FF is EE plus about 8 thousandths of an inch or greater.

9. The knife blade as claimed in claim 8 characterised in that BB=20 thousandths of an inch; CC=22 thousandths of an inch; DD=26 thousandths of an inch; EE=41 thousandths of an inch; and FF=56 thousandths of an inch, where the measurements given are all within about 0.5 thousandths of an inch of the value given.

10. The knife blade as claimed in claim 9 characterised in that the blade is polished after being ground, in this case the polishing reduces the as ground thickness, independently at each specified point, by between about 0 and 1 thousandths of an inch.

11. The knife blade as claimed in claim 7 characterised in that the blade is polished after being ground, in this case the polishing reduces the as ground thickness, independently at each specified point, by between about 0 and 1 thousandths of an inch.

12. The knife blade as claimed in claim 1 characterised in that that the blade thickness at about from the shoulder is FF; where FF is greater than about 50 thousandths of an inch.

13. The knife blade as claimed in claim 1 characterised in that the shoulder thickness is about 17 thousandths of an inch.

14. The knife blade as claimed in claim 1 characterised in that the blade is polished after being ground, in this case the polishing reduces the as ground thickness, independently at each specified point, by between about 0 and 1 thousandths of an inch.

15. A knife including the knife blade as claimed in claim 1.

16. The knife as claimed in claim 15 characterised in that the knife is a boning knife with a rake of between 29 mm and 35mm.

17. The knife as claimed in claim 16 characterised in that the rake is 32mm.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) For clarity the prior art is shown in the following accompanying drawings, in which:

(2) FIG. 1 shows a cross sectional view of a carbon steel knife blade;

(3) FIG. 2 shows a cross sectional view of a stainless steel knife blade;

(4) FIG. 3 shows a cross sectional view of a hollow ground knife blade, as manufactured;

(5) FIG. 4 shows a cross sectional view of a knife blade with the profile described in U.S. Pat. No. 4,495,698, i.e. a concave grind.

(6) By way of example only, a preferred embodiment of the present invention is described in detail below with reference to the accompanying drawings, in which:

(7) FIG. 5 shows a side view of a knife with the blade profile of the invention;

(8) FIG. 6 shows a cross sectional view through X-X;

(9) FIG. 7 shows a cross sectional view of the blade lying against a surface.

BEST MODE FOR CARRYING OUT THE INVENTION

(10) Referring to FIG. 5 a knife (1) including a blade (2) and a handle (3) is shown. The blade (2) includes a cutting edge (4), a shoulder (6), tip (7) and back (8), where the tip (7) is the section of the blade (2) at the end of the blade (2) furtherest from the handle (3).

(11) The cutting edge (4) is the section of blade (2) that actually cuts the material being processed, the thickest part of the cutting edge (4) is the shoulder (6). The thinnest section of the cutting edge (4) forms a peripheral edge of the blade (2). The back (8) is the peripheral edge of the blade (2) opposite the cutting edge (4) that, if the blade has a point (9), meets the cutting edge (4) at the point (9). The point (9) forms the extreme exposed end of the blade (2) when present.

(12) The cutting edge (4) in cross section is an isosceles triangle with the base formed by the shoulders (6) and the thinnest section forming the vertex. The angle of the cutting edge (4) is dependent on the material used for the blade (2).

(13) Now the back (8) is sometimes referred to as the spine, however, the spine is not always a peripheral edge of the blade (2), so the term back (8) will be used herein. The spine is simply the path formed by the thickest section (across the width of the blade (2) running from handle (3) to tip (7). For succinctness we will use the standard shortened form of thousandths of an inch, thou, for thickness measurements (where 1 thousandths of an inch is 0.0254 mm).

(14) Referring to FIG. 6 a cross sectional view through the knife (5) along the line X-X is shown, this cross section is approximately 1 inch (25 mm) along the blade (2) from the handle (3) and is the desired blade (2) profile. This desired blade (2) profile continues along the length of the blade (2) following the line of the cutting edge (4). The blade (2) profile smoothly transitions to the profile at the intersection between the handle (3) and the blade (2) at that point. As the blade (2) profile extends from the shoulder (6) away from the cutting edge (4), all the way to the point (9), the blade (2) profile at the tip (7) extends along the back (8) towards the handle (3) from the point (8). This reduces the thickness of the blade (2) at the tip (7) and increases the flexibility of the tip (7).

(15) The thickness of the blade (2), as ground, at the shoulder (6) along the line A-A is 16 to 23 thou (0.41 to 0.58 mm), 1/16 (about 1.6 mm) away from the shoulder (6) in the direction of the back (8), along the line B-B, the thickness of the blade (2) is 19 to 26 thou (0.48 to 0.66 mm) and at (about 3.2 mm) away from the shoulder (6) in the direction of the back (8), along the line C-C, the thickness of the blade (2) is 21 to 28 thou (0.53 to 71 mm). At (about 6.4 mm) away from the shoulder (6) in the direction of the back (8), along line D-D, the thickness of the blade (2) is 25 to 32 thou (0.64 to 0.81 mm), at (about 9.5 mm) away from the shoulder (6) in the direction of the back (8), along the line E-E, the thickness of the blade (2) is 41 to 48 thou (1.04 to 1.22 mm) and at (about 12.7 mm) away from the shoulder (6) in the direction of the back (8), along the line F-F, the thickness of the blade (2) is greater than 55 thou (1.27 mm). The thickness of the blade (2) at the back (8) depends upon the width of the blade (2) at that point, if the width of the blade (2) is less than then the thickness will match the blade (2) profile described, if greater than this it is likely to lie between 40 thou (1.02 mm) and 80 thou (2.04 mm). The blade (2) profile smoothly transitions between these thicknesses, across and along the blade (2). Please note that all figures given are +/1 thou, except for FF which is dependent on the material used as it is a transition point through to the blank thickness.

(16) Please note that though ranges of figures are given for the blade (2) profile the thickness at any given cross section follows the following pattern, using the cross section lines A-A to F-F; A-A is 16 to 23 thou; B-B is A-A+3 thou; C-C is A-A+5 thou (B-B+2 thou); D-D is A-A+9 thou (C-C+4 thou); E-E is A-A+25 thou (D-D+16 thou); F-F is greater than about 55+/10 thou.

(17) Giving the following table, Table 1, of as ground profiles, noting that even though whole thousandths of an inch are given this does not exclude fractional figures:

(18) TABLE-US-00001 TABLE 1 Shoulder 1/16 from 1/8 from 1/4 from 3/8 from 1/2 from or shoulder shoulder shoulder shoulder shoulder section or section or section or section or section or section A-A B-B C-C D-D E-E F-F 16 19 21 25 41 >50 17 20 22 26 42 >50 18 21 23 27 43 >50 19 22 24 28 44 >50 20 23 25 29 45 >50 21 24 26 30 46 >50 22 25 27 31 47 >55 23 26 28 32 48 >55 All thicknesses are in thousandths of an inch and +/ 1 thou.

(19) It should be noted that all of the thicknesses given are as ground, this is prior to any polishing or later processing/finishing steps. This means that a finished blade (2) may well be thinner than the thicknesses given here. The following table, Table 2, provides as ground and finished thicknesses (though they are only a guide at best and variation is expected). The blade (2) profile may well vary due to variations across the blade (2) during the glazing and/or polishing

(20) TABLE-US-00002 TABLE 2 Shoulder Shoulder Shoulder thickness thickness thickness (section A-A) (section A-A) (section A-A) after Type of knife as ground after polish glaze and polish 6 curved boning 18 17 to 18 14 to 16 19 18 to 19 16 to 18 21 20 to 21 18 to 20 23 22 to 23 20 to 21 5 curved boning 17 15 to 16 12 to 14 19 18 14 to 15 21 20 to 21 17 to 18 23 22 20 to 21 All measurements in thousandths of an inch, and +/ 1 thou.

(21) Because the blade (2) profile follows the cutting edge (4) to the tip (7) and extends from the point (9) to the handle (3) down the back (8) of the blade (2), a user can shape the tip (7) to their preference yet still retain cutting performance. Of course there are limits to how much the tip (7) can be modified as the blade (2) profile only extends so far along the back (8).

(22) Referring to FIG. 7 the blade (2) is shown in cross section resting against a flat surface (10), in this position the shoulder (6) of the blade (2) and the back (8) of the blade (2) are the only points touching the flat surface (10). The shoulder (6) or cutting edge (4) will always be one of the contact points, the back (8) may not always be. Because these points are the only ones touching the surface this may produce less drag on the blade (2) in use.

(23) It should also be noted that the blade (2) profile given is material dependant and, though preferred for the grades of stainless steels presently used. If a different material is used then the blade (2) profile may commence from a thinner shoulder (6), the rest of the dimensions similarly reduced.

(24) It should be noted that this profile eliminates the narrowing behind the shoulder (6) found in hollow ground blades (2), which is a weak point.

(25) For boning out carcasses the knife (1) is held the same as for stabbing downwards, sometimes called a dagger grip for around 80% of the time. For many knives (1) the rake is effectively 0 whereas it has been found that a rake of 32 mm+/10% is, for boning knives, desirable. For clarity the rake is the height of the point (9) above the handle (3), providing the point (9) is the part of the tip (7) that gives the maximum height. To put this another way, it is the offset between a line drawn along the handle (3) and a parallel line drawn through the point (9) of the blade (2).

(26) In other embodiments the knife (1) may include the blade (2) profile but not the preferred rake, for example for vegetable or other knives.

(27) Results

(28) Surprisingly a knife (1) with this blade (2) profile, with an as ground shoulder (6) thickness of 17 thou, has been found to need little maintenance, a light steel seems to return the edge quickly when necessary. Even a nick in the cutting edge (4) that would normally have required setting a new cutting edge (4) was able to be removed by a steel. Given the glazed and polished thickness of this knife (1) it is a surprising result, as previously knives (1) with blades (2) this thin have had durability issues. From trials the cutting edge (4) is retained longer than normal knives (1) and so a steel is used less, in fact for one trial only a steel was used for the first 10 months.

(29) From one trial, still ongoing, it would appear that the blade (2) profile when used on a boning knife extends the life by at least a factor of 3. Now some of this may be due to the user of the knife (1) but in the same length of time most users would have worn out 3 knives. This trial has now run for an extended period and it was 10 months before the knife needed the first stoning, and even this was minor. The knife after stoning returned to looking as new and is still in use.

(30) From brief trials using a boning knife with the blade (2) profile described increased the yield by between 1% and 4% (though this needs to be confirmed by more robust measurement). This is a significant gain as it is achieved with less effort than currently required. A full scale yield trial needs to be undertaken to confirm this, but as the knife profile is thinner than currently used knives there is less effort thus less meat being levered around.

(31) The reduction in the force required to use the knife is as yet unknown but one trial with a boning knife required noticeably less effort to use.

(32) Thicknesses E-E and F-F are less critical than the others and it is believed that an embodiment with the following profile may also work: A-A is 16 to 23 thou B-B is A-A+3 thou; C-C is A-A+5 thou (B-B+2 thou); D-D is A-A+9 thou (C-C+4 thou); E-E is A-A+14 thou (D-D+5 thou); F-F is A-A+22 thou (E-E+8 thou).

(33) The above profile has not yet been confirmed as practical, though E-E and F-F are the only changes from the preferred embodiment as they are believed to be less critical.

(34) The results of a further trial carried out on mutton and lamb, found that there was around 9% less cutting force and 3% less peak effort required to achieve the same results as a normal hollow ground knife. A 9% reduction in cutting force is a significant reduction. It should be noted that although the users in the trial were skilled meat processing workers they had not been specifically trained in the use of the knife ground with the inventive profile. One user was shown how to use the knife and immediately his figures improved still further, however these figures were discounted from the study results as they could be seen as skewing the results.

(35) This 9% reduction in required cutting force, and extended time between sharpening, will result in less fatigue and potentially a lower incidence of musculoskeletal disorders in users of knives with this profile. It has been shown that fatigue can affect the quality so less wastage is expected.

(36) A fish trial has found that even with a group of users with less than optimum sharpening techniques the life of a knife with this blade profile is at least three times that of knives used for similar purposes. This was whilst requiring less force even when blunt. It is believed that trained operators will extend the life of the knives still further.

ITEM LIST

(37) 1 knife 2 blade 3 handle 4 cutting edge 5 . 6 shoulder 7 tip 8 back 9 point 10 flat surface.