GB2578516A - Saw Blade - Google Patents

Abstract

A saw blade 5 having a support 9 and saw teeth 11, the teeth being arranged along the length of the support and extending from its lower edge to form a cutting edge 13, wherein the support has a first thickness and the cutting edge has a second thickness, the second being greater than the first. The blade may be formed from sheet material. The support and teeth may be a monolithic structure and the support may be machined to reduce its thickness from the second thickness to the first. The second thickness may be at least 10% greater than the first. The blade may be for a hand saw, particularly a bow saw (101; Fig 1). The purpose is to minimise/eliminate pinching. Also disclosed is a method of mitigating pinching of a saw blade comprising: starting cutting a workpiece 15 using a cutting edge on the lower edge of a support that has a first thickness and continuing the cutting to form a cut having a second thickness, the second being greater than the first, such that the interference of the support on the sides of the cut is reduced.

Description

SAW BLADE

Field of the Invention

The present invention concerns saw blades. More particularly, but not exclusively, this invention concerns saw blades for hand-held saws such as bow saws, and methods for preventing pinching during sawing.

Background of the Invention

Saw blades are well known and can take a number of forms. There are numerous designs of saw blade. The different designs are often associated with optimising their suitability for a particular use. For example a back saw tends to have fine teeth and a short but deep blade suitable for fine woodwork. In contrast a bow saw blade may have larger teeth with a larger pitch, and tends to be a long, but shallow blade suitable for sawing through large pieces of fresh wood, such as logs or tree branches.

A problem encountered when sawing wood, and especially when sawing wood for logs, is the tendency for the saw blade to become pinched. This occurs when the wood above the saw blade flexes inwards and closes the cut onto the blade. When the blade becomes pinched, it becomes very difficult to move the saw blade along the cut and it tends to be necessary to remove the blade and start a fresh cut. In some circumstances, the blade may even become damaged.

Development to date, especially in the context of bow saw blades, has been in the context of improving the shape and/or layout of cutti ng teeth. F or example, a different tooth shape or layout may be provided depending on whether the blade is for green wood or seasoned wood. Such features tend to improve the efficiency of the cut, but tend not to prevent, or address, pinching.

The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved saw blade.

Summary of the Invention

According to a first aspect of the invention, there is provided a saw blade comprising a support structure and a multiplicity of saw teeth. The saw teeth are arranged along the length of the support structure and extend from the lower edge thereof to form a cutting edge. The support structure has a first thickness and the -2 -cutting edge has a second thickness, the second thickness being greater than the first thickness Conventional saw blades tend to be formed of sheet material having a uniform thickness. The cut therefore tends to be essentially identical in thickness to the support material. In contrast, the present invention recognises that by providing a support structure having thickness that is less than the thickness of the cutting edge, pinching can be reduced.

The support structure may be a sheet material having a thickness equal to the first thickness.

The thickness of the cutting edge may be determined in a number of ways.

For example, the teeth may be orientated, or shaped, such that the cutting edge has a greater thickness than the support structure. In preferred embodiments of the invention, the saw teeth are formed from sheet material having a thickness equal to the second thickness. Such an arrangement has been found to be an effective way of ensuring the relatively large thickness of the cutting edge, whilst maintaining a simple arrangement of saw teeth.

The support structure and the saw teeth may be a monolithic structure. The thickness of the support structure may have been machined to reduce its thickness from the second thickness to the first thickness. The monolithic structure may be sheet 20 metal.

The second thickness is sufficiently greater than the first thickness to reduce pinching. For example, the second thickness may be sufficiently greater than the first thickness that the support structure substantially avoids contact with the sides of the cut during sawing. The second thickness may be 5%, and more preferably at least 10%, greater than the first thickness.

Aspects of the present invention have been found to be especially beneficial in the context of hand saws because pinching tends to be particularly problematic in this context (due to the limited manual actuation power, and the more variable nature of a manual cutting action). The blade may be for a hand saw. The blade is preferably for a bow saw blade. Aspects of the present invention have been found to be especially beneficial in the context of bow saws as these tend to be used in situations in which pinching can occur (e.g. sawing logs, and potentially involving deep cuts for large diameter logs). -3 -

According to another aspect of the invention, there is provided a bow saw comprising the saw blade of the first aspect of the invention.

According to another aspect of the invention, there is provided a method of mitigating pinching of a saw blade. The method comprises the steps of: (a) Starting a cutting motion, preferably on a piece of wood, using a cutting edge on the lower edge of a support structure that has a first thickness; (b) continuing the cutting motion to forming a cut having a second thickness, the second thickness being greater than the first thickness such that the interference of the support structure on the sides of the cut is reduced.

It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

Description of the Drawings

An embodiment of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: Figure 1 shows a perspective view of an example bow saw of the prior art Figure 2a shows a close up of part of the saw blade in Figure 1; Figure 2b is a sectional view through A-A in Figures 1 and 2a; Figure 3a shows a close up of part of the saw blade according to first embodiment of the invention; Figure 3b is a sectional view through A-A in Figure 3a; Figure 4 is a schematic view showing the saw blade of Figures 3a and 3b cutting through a log; and Figures 5a and 5b are sectional views through saw blades according to second and third embodiments of the invention respectively.

Detailed Description

Figure 1 shows an example of a known bow saw 101. The bow saw comprises a curved frame 103 and a saw blade 105 extending between the ends of the frame. A tensioning handle 107 is provided to tension the blade in the frame. -4 -

Figure 2a shows a close up of part of the saw blade in F igure 1, and Figure 2b is a sectional view through A-A in Figures 1 and 2a. The saw blade 105 is formed from a single piece of sheet metal and comprises a generally elongate support structure 109 extending along the length of the blade 105. A series of saw teeth 111 are spaced along the support structure and extend downwardly from the lower edge of the support structure (the lower edge being illustrated in Figure 2a by the large-dashed I i ne).

The saw teeth have bevel led edges. The bevelled edges to the teeth are not shown in the schematic drawing of Figure 2a, but are partially illustrated in Figure 2b by the tapered sides of the saw tooth, converging toward the root. The saw teeth 111 form a cutting edge 113 on the lower edge of the support structure 109. The cutting edge 113 is generally demarked using the dashed line in Figure 2b, and extends the full depth and width of the teeth 111.

Such features are well known per se and need not be described further.

Figure 3a shows a close up of part of the saw blade in a first embodiment of the invention, and Figure 3b is a sectional view through A-A in Figure 3a. The saw blades is a monolithic su-ucture formed from a single piece of sheet metal and comprises a generally elongate support structure 9 extending along the length of the blade 5. The blade is used in a bow saw (not shown). A series of saw teeth 11 are spaced along the support structure 9 and extend downwardly from the lower edge of the support structure (the lower edge being illustrated in Figure 3a by the feint line). The above-mentioned features mirror those of the known blade 105 in Figures 1 to 2b. However, in contrast to the known blade 105, the support structure 9 of the blade 5 of the first embodiment is thinner (i.e. has a smaller thickness) than the thickness of the saw teeth 11. As a result, the cutting edge 13 has a greater thickness than the thickness of the support structure 9.

Figure 4 is a schematic view of the saw blades being used when cutting a log 15. The cut above the blade 5, is wider than the support structure 9. If the log 15 is urged to rotate inwardly (indicated by the grey arrow in Figure 4), the support structure is less prone to contacting the sides of the cut and therefore less prone to pinching.

In the first embodiment the reduced width of the support structure is created by machining the surface of the support structure to remove material during manufacture of the blade 5. Figure 5a shows a second embodiment where the -5 -thickness difference is instead achieved by forming the teeth 11 'froma thicker sheet material and attaching the teeth 11 "tothe lower edge of the support structure 9-using a fixing means, such as a weld. Figure 5b shows a further alternative embodiment in which the sheet material is of uniform thickness, but the cutting edge 13-is wider than the support structure 9-by virtue of the alternately outwardly angled teeth 11 -.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. For example, the saw teeth and the support structure may, in principle, be separate structures that are joined, by any means, during manufacture of the blade.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claim for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments. -6 -