WO2007020462A1

WO2007020462A1 - Saw blade

Info

Publication number: WO2007020462A1
Application number: PCT/GB2006/003104
Authority: WO
Inventors: Paul Staite
Original assignee: Paul Staite
Priority date: 2005-08-18
Filing date: 2006-08-18
Publication date: 2007-02-22
Also published as: GB0516973D0; GB2429185A

Abstract

A saw blade (1) comprising a leading cutting side (2) and a trailing side (3) , in which the trailing side comprises a first rear corner and a second rear corner, in which a first cutting profile (6) is formed on the first rear corner, and a second cutting profile is formed on the second rear corner, and in which the first cutting profile and the second cutting profile are parallel with one another along at least a part of their length.

Description

Saw blade

This invention relates to a saw blade, for use particularly, but not exclusively as a jigsaw blade.

Jigsaws are commonly used to make non-linear and intricately shaped cuts in material. In order to achieve such cuts the blades used have a short depth and a fine width, so they can be manoeuvred through the material without jamming. As a result of their small dimensions jigsaw blades have a certain resilience along their length.

However, jigsaw blades suffer from a particular problem known as "run off'. When a curve is cut into a material the resilient blade bends outwards towards its free end, and as a result the radius of the top of the cut is smaller than that at the bottom. This is mainly caused by a frictional binding between the inside flank and outside trailing edge of the blade as it is driven through the material. As the blade is turned these two parts become wedged against the material and cause the blade to bend outwards. When a jigsaw is used the user manipulates it through the subject material, but the torque induced when this is done is not transmitted evenly down through the cut. The upper run of the blade accurately reflect the user's intentions, but due to both flex in the blade and the confinement of the unsupported extremity of the tool bit in the subject material, the blade binds as described above, and "run off' occurs.

Jigsaw blades are mounted to a motor at their top end and are driven in a reciprocal action. It is common to provide some kind of guide means at a mid point on the blade, which has a number of purposes. The guide means helps to prevent the blade from bending back when it is forced into the material to be cut. In addition, jigsaw blades are sometimes used at an angle to vertical, and the angle can be set by adjusting the position of the guide means back and forth. This is referred to as the pendulum action. One known type of guide means comprises a guide roller applied to the trailing side of the blade. These guide rollers comprise a free rotating drum with a circumferential trough around their centre, in which is situated the trailing side of the blade. The drum is either fixed in position or resiliently forced against the trailing side of the blade to ensure contact. As the blade rises and falls the drum rolls back and forth, and as the blade is driven through the material the drum prevents it bending back. The position of the drum can be changed in order to set a preferred cutting angle of the blade.

The present invention is intended to overcome some of the above problems.

Therefore, according to a first aspect of the present invention, a saw blade comprises a leading cutting side and a trailing side, in which the trailing side comprises a first rear corner and a second rear corner, in which a first cutting profile is formed on the first rear corner, and a second cutting profile is formed on the second rear comer, and in which the first cutting profile and the second cutting profile are parallel with one another along at least a part of their length.

The above arrangement alleviates the frictional binding which leads to "runoff". The first or second cutting profile, whichever is on the outside of a curve being cut, actually cuts into the material if it is forced against it, which helps to prevent the blade from becoming jammed and bending outwards towards the bottom of its run.

As discussed above, the most common type of guide means used with automated saw blades comprises a rotating drum provided with a circumferential trough in which the saw blade is situated. In order to allow the saw blade of the invention to work with such an arrangement the first and second cutting profiles must not cut the material of the drum. There are two ways this can be achieved. In a first embodiment of the invention the first cutting profile and the second cutting profile can comprise cutting teeth which do not extend rearwardly beyond a surface of the trailing side. In addition, the first cutting profile and the second cutting profile can comprise cutting teeth which do not extend laterally beyond a surface of a right side and a surface of a left side respectively of the saw blade.

In addition, there must be a portion of the trailing side against which the drum can act, and therefore a bearing surface can be formed between the cutting profiles.

With this arrangement the trailing side of the saw blade can be mounted in the trough of a rotating drum, with the first and second cutting profiles running therethrough, without the drum being cut

However, there is a possibility that in use the saw blade can twist or move sufficiently for the cutting profiles to damage a drum. In addition, in order to provide for a functionally effective bearing surface between the first and second cutting profiles, the saw blade must be relatively wide.

Therefore, in an alternative construction the first and second cutting profiles can be formed on a first part of the rear corners, and a bearing surface can be formed above these parts. This bearing surface can be mountable in a rotatable drum as described above, and as there are no cutting profiles in that area no damage can be done to the drum in use.

This construction is possible without compromising the cutting ability of the first and second cutting profiles, because the part of a saw blade against which known rotating drums act does not generally travel far enough below the drum to pass into the subject material being cut. In addition, this embodiment saves on having to manufacture the cutting profiles along the whole length of the saw blade, and reduces the negative impact upon structural rigidity caused by removing material from the saw blade to form cutting profiles. It also allows for the saw blade to be narrower if desired as there is no need to provide for a functional bearing surface between the first and second cutting profiles.

Whichever of the above constructions is used, it is always preferable to have a flat or concave surface extending between the first and second cutting profiles, whether this surface works as a bearing surface or not.

This is because such a surface improves the structural integrity of the saw blade along its length. A flat surface along the whole length of the saw blade provides it with structural stiffness. If the first and second cutting profiles contacted one another, and no flat surface were provided between them, the saw blade would be weak in comparison and would flex more in use.

In addition, having the first and second cutting profiles separated apart like this improves the working of the saw blade. The saw blade works best if the cutting performed by the first and second cutting profiles is limited to the areas around the rear comers, and as referred to above does not extend beyond the surfaces of the trailing side or the first and second sides. This is because with this construction the first and second cutting profiles do not dig unnecessarily into the subject material being cut. If they cut too deeply into the subject material, or cut into the material when it is not necessary because there is no frictional binding, then there is a danger that the frictional forces created will cause the saw blade to jam. With the limited extent of the cutting profiles described above they only cut into the subject material if the saw blade begins to bind, which happens in a tight curve or if the saw blade flexes, as described above. The leading cutting side of the saw blade can comprise a leading cutting profile, which can cut in a first axial direction of the saw blade, while the first cutting profile and the second cutting profile can cut in a second axial direction of the saw blade. This construction balances the frictional forces applied to the saw blade in use, and in fact makes the saw blade quieter and smoother to use because a friction can be applied to the blade in both the downward and upward parts of the reciprocal action. This prevents juddering,

In order to provide further strength to the saw blade the leading cutting profile can be formed on a first part of the leading cutting side, and a shoulder portion can be formed above the leading cutting profile. The shoulder portion can simply be a portion of the leading cutting side in which no cutting profile is formed.

It will be appreciated that the first and second cutting profiles can be any shapes which can cut into a subject material. These shapes can be determined by the type of material which is to be cut by the blade, for example soft wood, hard wood, or sheet metal. The various cutting profiles envisaged can be any of the known types.

It will be further appreciated that the cutting profiles could be arranged at any angle on the corners of the trailing side. However, in a preferred construction the first cutting profile and the second cutting profile can be formed at substantially 45 degrees to the trailing side.

In one version of the invention the cutting profiles can each comprise a toothed portion formed on the rear corner, and a side scraping portion formed on the adjacent side. The toothed portion can be adapted to cut into the subject material to provide the functionality of the invention as described above, while the side scraping portions can be provided in order to provide a smoother finish. If the cutting profiles comprise just teeth, then rough vertical striations can be left in the cut material. The side scraping can add a smooth tool action to the cut. Therefore, the toothed portions can comprise a row of teeth, and the scraping portions can comprise scalloped cut-away portions formed between the teeth, which extend onto the corresponding first side or second side. Upper edges of the scalloped cut-away portions can be formed into scraping blades. Thus, the saw blade of the invention can perform a side planing action which ensures that any surfaces cut by the teeth of the toothed portions are smoothed off.

These scalloped cut-away portions also allow for cut material to be diverted away from the teeth and the material being cut, and prevent it clogging the action.

The saw blade can be provided with a tapering section which tapers towards the trailing side, such that the first rear corner and the second rear corner are closer together than portions of the first side and the second side before the tapering section. This construction allows the trailing side of the saw blade to travel through the material being cut more easily, and plane more accurately in tight cuts.

Preferably the saw blade is a jigsaw blade, however the invention could be used with any saw blade which is used to cut curved or intricate shapes through a material.

The invention also includes an actual sawing machine provided with a jigsaw blade as described above.

Therefore, according to a second aspect of the present invention a jigsaw is provided with a saw blade as described above.

The invention can be performed in various ways but three embodiments will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a side view of a saw blade according to the first aspect of the present invention;

Figure 2 is a rear view of the saw blade as shown in Figure 1;

Figure 3 is a rear perspective view of the saw blade as shown in Figure 1;

Figure 4 is a part perspective view of a jigsaw according to the second aspect of the present invention;

Figure 5 is a side view of a second saw blade according to the first aspect of the present invention;

Figure 6 is a rear view of the saw blade as shown in Figure 5;

Figure 7 is a rear perspective view of the saw blade as shown in Figure 5; and

Figure 8 is a part rear perspective view of the saw blade as shown in Figure 5.

As shown in Figure I₁ a saw blade, in the form of jigsaw blade 1, comprises a leading cutting side 2 and a trailing side 3, in which the trailing side 3 comprises a first rear corner 4 and a second rear comer 5, in which a first cutting profile 6 is formed on the first rear corner 4, and a second cutting profile 7 is formed on the second rear corner 5, and in which the first cutting profile 6 and the second cutting profile 7 are parallel with one another along at least a part of their length.

Between the two cutting profiles 6 and 7, is a flat bearing surface 8, and as is clear from Figures 1 and 2, the first cutting profile 6 and the second cutting profile 7 comprise cutting teeth 9 which do not extend rearwardly beyond the surface of the trailing side 3, and which do not extend laterally beyond the surface of a first 10 and a second 11 side respectively of the blade 1. The cutting profiles 6 and 7 are formed at 45 degrees to the trailing side 3.

In other respects the jigsaw blade 1 is like a known jigsaw blade, and it has a leading cutting profile 12 formed in the leading cutting side 2, and it has a mounting section 13, adapted to fit into a jigsaw machine. The jigsaw blade 1 is made from metal and has a short depth A-A and a narrow width B-B, so it can be used to cut curved or intricate shapes in a subject material.

In use the blade 1 is mounted in a jigsaw machine, which could be a handheld or a free standing machine, and is moved up and down in a reciprocal action by the machine. The blade 1 is then driven into a subject material to be cut, either by running a hand held machine over the material, or forcing the material against the blade 1 in a free standing machine.

When the blade 1 is driven through a curved path (or when the material is moved through a curved path about the blade 1) the blade 1 suffers less frictional binding between whichever side 10 or 11 is on the inside of the curve and whichever rear comer 4 or 5 is on the outside of the curve, than a conventional blade. The first 6 or second 7 cutting profile, whichever is on the outside of the curve being cut, cuts into the material if it is forced against it, which helps to prevent the blade 1 from becoming jammed in the material and bending outwards.

The invention also includes a jigsaw provided with a blade as described above, and part of such an arrangement is shown in Figure 4.

In Figure 4 a jigsaw blade 40 is mounted into a jigsaw machine, only a guide means 41 of which is visible. The jigsaw machine is of a known construction and is therefore not further described here. The jigsaw blade 40 is of identical construction to jigsaw blade 1 as shown in Figures 1 to 3. In particular it has a trailing side 42 with a first cutting profile 43 formed on a first rear comer 44, a second cutting profile 45 formed on a second rear corner 46, and a flat bearing surface 47 formed between the cutting profiles 43 and 45. The teeth 48 of the cutting profiles 43 and 45 do not extend beyond the surface of the trailing side 42, and do not extend beyond the surface of a first (not visible) and second 49 side respectively of the saw blade 1.

The guide means 41 comprises a roller means 50 comprising a rotating drum 51 provided with a circumferential trough 52. The drum 51 is mounted on two arms 53 and 54, which can be moved back and forth in a pendulum action in order to support the blade 40 at a preferred angle.

The trailing side 42 of the blade 40 is disposed in the trough 52, and is thereby held in position by the guide means. The trough 52 is deeper than the depth- wise extent of the first and second cutting profiles 43 and 45 on the blade 1, such that parts of the first (not visible) and second 49 sides of the blade 1 contact the walls of the trough 52. The bearing surface 47 is in contact with the base of the trough 52.

It will be appreciated that the first cutting profile 43 and the second cutting profile 45 do not cut into the rotating drum 51 because they do not extend beyond the planes of the trailing side 42, the right (not visible) and the left 49 side.

Thus, the jigsaw blade of the invention can be used with known guide means without causing damage.

Figures 5 to 8 show an alternative construction of a saw blade which works in essentially the same manner to cut subject material as saw blade 1 described above, however there are a number of further features.

As shown in Figures 5 to 7 saw blade 60 comprising a leading cutting side 61 and a trailing side 62. The trailing side 62 comprises a first rear corner 63 and a second rear corner 64, and a first cutting profile 65 is formed on the first rear corner 63, and a second cutting profile 66 is formed on the second rear corner 64. The first cutting profile 65 and the second cutting profile 66 are parallel with one another along at least a part of their length.

As is clear from Figures 5 to 7 the first 65 and second 66 cutting profiles are formed on first parts 67 and 68 respectively of the rear comers 63 and 64, and a bearing surface 69 is formed above these parts 67 and 68. (This bearing surface 69 is mountable in a rotating drum like that shown in Figure 4, and as no cutting profiles are formed in that area no damage can be done to the drum if the saw blade 60 twists or bends against it in use.)

This construction does not compromise the cutting ability of the first and second cutting profiles 65 and 66, because only the part of the saw blade 60 along which the first and second cutting profiles 65 and 66 are formed actually passes through the subject material in use. The part above this, where the bearing surface 69 is formed, does not travel far enough below a rotating drum to pass into the subject material being cut

In addition, this arrangement saves on having to manufacture the cutting profiles 65 and 66 along the whole length of the saw blade 60, and reduces the negative impact upon structural rigidity caused by removing material from the saw blade 60 to form cutting profiles.

It also allows for the saw blade 60 to be constructed narrowly if desired, as there is no need to provide for a functional bearing surface between the first and second cutting profiles 65 and 66, and as a result its width C-C is shorter than the width B-B of saw blade 1 described above.

Nevertheless, a flat surface 70 extends between the first and second cutting profiles 65 and 66. This arrangement improves the structural integrity of the saw blade 60 along its length because it provides structural stiffness. If the first and second cutting profiles 65 and 66 contacted one another, and no flat surface 70 were provided between them, the saw blade 60 would be weak in comparison and would flex more in use.

In addition, having the first and second cutting profiles 65 and 66 constructed to such a limited extent, and thereby separated apart like this, improves the functionality of the saw blade 60.

The saw blade 60 works well because the cutting performed by the first and second cutting profiles 65 and 66 is restricted to the areas around the rear corners 63 and 64 and does not extend beyond the surface of the trailing side 62 or the surfaces of first and second sides 80 and 78. The cutting profiles 65 and 66 do not dig unnecessarily into the subject material being cut, and only do so if the saw blade 60 begins to bind, which happens in a tight curve or if the saw blade flexes, as described above. If the cutting profiles 65 and 66 cut too deeply into the subject material, or cut into the material when it is not necessary because there is no frictional binding, then there would be a danger that the frictional forces created would cause the saw blade 60 to jam.

Another difference between saw blade 1 described above and saw blade 60 is that the leading cutting profile 71 faces upwards and the first and second cutting profiles 65 and 66 face downwards. This balances the frictional forces applied to the saw blade 60 in use, and in fact makes the saw blade 60 quieter and smoother because a friction can be applied to the blade in both the downward and upward parts of the reciprocal action.

A further feature of saw blade 60 is that leading cutting profile 71 is formed on a first part 72 of the leading cutting side 61, and a shoulder portion 73 is formed above this. The shoulder portion 73 is simply a portion of the leading cutting side 61 on which no cutting profile is formed, and as such it is structurally strong, and helps to improve the general rigidity of the saw blade 60. The first and second cutting profiles 65 and 66 on saw blade 60 are constructed differently to those on saw blade 1. As shown in Figure 8, the first and second cutting profiles 65 and 66 each comprise a toothed portion 74 and 75 respectively, formed on the rear corner 63 and 64 respectively. These toothed portions 74 and 75 provide the same function as the first and second cutting profiles 6 and 7 on saw blade 1 described above, although the teeth 76 are spaced further apart. The toothed portions 74 and 75 are formed at 45 degrees to the trailing side 62.

In addition, the first and second cutting portions 65 and 66 also comprise side scraping portions on the adjacent side. Only side scraping portion 77 is visible in Figure 8, and it is formed on the second side 78. (A opposite side scraping portion 79 on the first side 80 is visible in Figure 5.) The scraping portions 77 and 79 comprise scalloped cut-away portions 81 formed between the teeth 76, which extend onto the corresponding first side 80 or second side 78. Upper edges 82 of the scalloped cutaway portions 81 are formed into scraping blades 83.

The toothed portions 74 and 75 cut into the subject material to provide the functionality of the invention as described above, while the side scraping portions 77 and 79 are provided in order to provide a smoother finish. If the first and second cutting profiles 65 and 66 comprised just teeth, then rough vertical striations can be left in the cut material. The side scraping portions 77 and 79 smooth these out. They also allow for cut material to be diverted away from the teeth 76 and the material being cut, which prevents any clogging.

Finally, the saw blade 60 is provided with a tapering section 84 which tapers towards the trailing side 62, such that the first rear corner 63 and the second rear comer 64 where the first and second cutting profiles 65 and 66 are formed are closer together than portions of the first side 80 and the second side 78 before the tapering section. This construction allows the trailing side 61 of the saw blade 60 to travel through the material being cut more easily. The above described embodiments can be altered without departing from the scope of the invention. In particular, in one alternative embodiment (not shown) a saw blade according to the invention is formed as an ordinary saw blade for a hand- driven saw with a handle at one, or either end. In another alternative embodiment (not shown) a saw blade according to the invention is formed as a hack-saw blade.

The above described embodiments suffer from one drawback, which is that the cut made by the blade can be widened if the first or second cutting profiles cut into the material on the outside of the curve. The tighter the curve the wider the cut may be. In order to manage this problem the first and second cutting profiles can be arranged at deeper or shallower angles than 45 degrees as shown above. Therefore, in other alternative embodiments (not shown) the first and second rear cutting profiles are formed at other angles than 45 degrees, and are formed at angles ranging from 1 degrees to 89 degrees to the trailing side.

Thus a saw blade is provided which greatly reduces the occurrence of "runoff". A saw blade is also provided which operates more smoothly than known constructions due to the balancing of frictional forces applied in use. Due to the smoother running and alleviation of frictional binding the saw blade of the invention also operates at a lower temperature than known constructions, which prevents damage to the blade and burning of the material.

Claims

1. A saw blade comprising a leading cutting side and a trailing side, in which the trailing side comprises a first rear comer and a second rear corner, in which a first cutting profile is formed on the first rear corner, and a second cutting profile is formed on the second rear corner, and in which the first cutting profile and the second cutting profile are parallel with one another along at least a part of their length.

2. A saw blade as claimed in Claim 1 in which the first cutting profile and the second cutting profile comprise cutting teeth which do not extend rearwardly beyond a surface of the trailing side.

3. A saw blade as claimed in Claim 2 in which the first cutting profile and the second cutting profile comprise cutting teeth which do not extend laterally beyond a surface of a right side and a surface of a left side respectively of the saw blade.

4. A saw blade as claimed in any of Claims 1 to 3 in which the trailing side is flat or concave, and in which the trailing side extends between the first cutting profile and the second cutting profile.

5. A saw blade as claimed in Claim 4 in which a portion of the trailing side comprises a bearing surface.

6. A saw blade as claimed in Claim 5 in which said bearing surface is formed between the first cutting profile and the second cutting profile.

7. ^' A saw blade as claimed in Claim 5 in which the first cutting profile and the second cutting profile are formed on a first part of the first rear corner and a first part of the second rear corner respectively, and in which the bearing surface comprises a portion of the trailing side above the first cutting profile and the second cutting profile.

8. A saw blade as claimed in any of the preceding Claims in which the leading cutting side comprises a leading cutting profile, in which the leading cutting profile cuts in a first axial direction of the saw blade, and in which the first cutting profile and the second cutting profile cut in a second axial direction of the saw blade.

9. A saw blade as claimed in any of the preceding Claims in which the leading cutting profile is formed on a first part of the leading cutting side, and in which a shoulder portion is formed above the leading cutting profile.

10. A saw blade as claimed in any of the preceding Claims in which the first cutting profile and the second cutting profile are formed at substantially 45 degrees to the trailing side.

11. A saw blade as claimed in any of the preceding Claim in which the first cutting profile and the second cutting profile each comprise a toothed portion which is formed on the first rear comer and the second rear corner respectively, and a side scraping portion formed on the first side and the second side respectively.

12. A saw blade as claimed in Claim 11 in which the toothed portions comprise a row of teeth, in which the scraping portions comprise scalloped cut-away portions formed between the teeth, which scalloped cut-away portions extend onto the corresponding first side or second side, and in which upper edges of the scalloped cut-away portions are formed into scraping blades.

13. A saw blade as claimed in any of the preceding Claims in which the saw blade is provided with a tapering section which tapers towards the trailing side, such that the first rear corner and the second rear corner are closer together than portions of the first side and the second side before the tapering section.

14. A jigsaw provided with a saw blade according to any of Claims 1 to 12.