WO2000007763A1

WO2000007763A1 - Saw blade comprising groups of teeth with varying widths or heights

Info

Publication number: WO2000007763A1
Application number: PCT/GB1999/002557
Authority: WO
Inventors: John Dexter
Original assignee: Skellingthorpe Saw Services Ltd
Priority date: 1998-08-05
Filing date: 1999-08-04
Publication date: 2000-02-17
Also published as: AU5184399A; GB9816916D0; GB2340068A; GB9918223D0

Abstract

A cutter tool (1) such as a saw blade and a method of preparing same for operational use in which the cutting edges (6E, 7E, 8E, ...), of the tool/blade effectively form successive groups of cutting edges, each group including a predetermined number of cutting edges, and in which the kerf widths and/or heights of such successive teeth within a group vary according to a predetermined pattern of width variation.

Description

CUTTER TOOLS

This invention relates to cutter tools and more particularly to cutter tools intended for the sawing of materials .

In general, many types and forms of cutter tools coramonmly called saw blades are known for the purposes of sawing of materials such as wood, metals, plastics.

In relation to the sawing of wood, saw blades may be regarded as falling into several major groups a first group including manually used saws, a second group comprising linear saws mounted for reciprocation in a suitable saw blade reciprocation machine, a third group including band s'aws which comprise an endless metal bands, provided with cutting teeth along one edge, the band saw when in use being supported by carefully spaced apart drive wheels which impart the requisite sawing speeds to the blade teeth and which maintain the blade under a suitable operational tension, and finally a group comprising circular saws, which as the name implies comprises a circular plate of metal carrying around its periphery a plurality of cutting teeth and having a central bore whereby the saw can be mounted upon a driving shaft or arbour.

In present day practice, particularly in relation to band saws and cirucular saws it is a usual practice for the individual teeth of a saw blade to be provided with hard material tips which actually provide the cutting edges of the teeth of the saw. Each tip when mounted to a host saw blade nests into a notch or recess provided in the tooth to which it is to be mounted. It is useful to bear in mind that until the advent of the hard material tip, the teeth formed in the saw body itself provided the actual cutting edges for the saw. In the absence of tips the teeth needed to be individually angularly set that is deformed relative to the plane of the blade body to enable a material cutting action by the blade. Such teeth setting was a tedious time consuming operation requiring in practice considerable operater skills particularly during resharpening operations on the

1 0 saw blade.

It is conventional to regard a tip as a block of hard material. For example, comprising a material known under the trade name Stellite or a tungsten carbide and like materials. Such tips present six surfaces including two

-₎ g major faces namely a so-called front face, which as its name implies constitutes the leading face of the tip when the saw is in use, this face being invariably inclined rearwardly downwardly, in relation to the direction of advance of the blade when in use, at an angle commonly

20 called the hook or rake angle, and a so-called top face whose leading edge meets with the uppermost edge of the front face. This top face inclines rearwardly downwardly at an angle commonly known as the top face ort back angle.

The edge formed by the meeting of the front and top faces

25 forms the actual cutting edge of the tip. The cutting length of such cutting edge defines kerf width of the blade, this kerf width being the width of a slot cut in a workpiece by the blade.

The remaining working faces of the tip are the two side

30 faces which usually incline towards each other in the direction from front to rear of the tip and additionally from top to bottom of the tip. In practice, the rear and bottom faces of the tips are essentially involved in the securing of the tip into its accommodating notch or recess.

The shape and form of these hard material tips in relation to the direction of advance of the saw blade into a material to be cut are a matter of extreme importance in that the operational efficiency of a saw blade resides in the angular relationships between the front face, the top and side faces. In fact, it is well understood that the operational efficiency of the saw is essentially totally dependent upon the precise shaping and form of the cutting tips in relation to the plane of the body of the saw, i.e., the endless band in the case of the band saw, and the side faces of the body of a circular saw.

I is known from practical usage of saw blades that the nature of such angular relationships plays an important part in the operational efficiency of a saw blade and its longevity of useful active working life particularly in terms of the extent of blade usage between or before the need to recondition the teeth/tips of the saw.

In is an object of the present invention to provide a saw blade construction and a method of producing such construction which enhances the useful life and performance of a saw blade.

Broadly, according to a first aspect of the present invention there is provided a method of preparing a cutter tool such as a saw blade for operational use in which the teeth of the tool/blade are regarded as forming successive groups, each of a predetermined number of successive teeth, and in which the kerf widths of successive teeth within a said group vary. Preferably, the variation of the kerf width is according to a regular pattern of width variation.

In accordance with a further aspect of the invention there is provided a method of preparing a cutter tool for operational use in which the teeth of the tool are notationally divided into successive groups each including a predetermined number of teeth, and in which the kerf widths of the teeth within a group successively vary from a minimum width to a maximum width and from said maximum width towards said minimum width.

Preferably, the variation of the kerf width within a group increases and descreases in two stages that are similar to each other.

In accordance with a further aspect of the invention there is provided a cutter tool such as a saw blade in which the cutting edges of the tool/blade effectively form successive groups of cutting edges, each group including a predetermined number of edges, and in which the kerf widths of such successive teeth within a group vary according to a predetermied pattern of width variation.

Preferably, the cutting edge widths vary from a minimum width to a maximum width and from said maximum width to said minimum width.

For a better understanding of the invention and to show how to carry the same into effect reference will now be made to the accompanying drawings in which :-

Figure 1 very schematically illustrates in side view a small section of a known constructio of a band saw body and associated teeth and tips; Figure 2 is a plan view of Figure 1;

Figure 3 is a plan view of a small section/segment of a saw blade corresponding to that shown in Figure 1 but incorporating the concepts of the present invention; and

Figure 4, very schematically illustates a variation of the form of cutting edges of a cutter tool such as a saw blade .

Referring now to Figure 1 , a band saw blade 1 includes a main body 2 having a rectilinear bottom (as shown in the Figures) edge 3. A series of teeth 4 (only six being shown in the Figures 1 to 3) is formed in the body by cutting out shaped recesses 5 in the main body.

The regions of the recesses 5 immediately adjacent to the associated front faces of the tips are commonly referred to as the gullets of the teeth.

Each tooth is notched at the leading part thereof and a hard material tip is secured in each such notch. In the Figures these tips are identified as 6,7,8,8,10, and 11.

The teeth have, as is shown in the Figure 1, a forward inclination from left to right.

In the Figures 1 to 3 the front faces of successive tips are identified as faces 6A , 7A , 8A , 9A , 10A and 11A; the rear faces are identified as faces 6B , 7B , 8B , 9B , 10B and 11B; the top facrs as faces 6C, 7C , 8C , 9C, 10C and 11C; whilst the side faces are identified as faces 6D , 7D , 8D , 9D , 10D and 11D. The cutting edges of the tips are defined by the meeting of the top and frnt faces and these cutting edges are identified as edges 6E , 7E , 8E , 9E , 10E and HE. In the Figures 1 to 3 these cutting edges are shown to be prependicular to the plane of the blade main body. In practice, it is possible for these cutting edges to be angled relative to the plane of the main body. In addition, since the cutting edges are presumed to be, in Figures 1 to 3, equidistant from the bottom edge 3 of the blade body the cutting edges lie in a common plane transverse to the plane of the blade body and parallel to the bottom edge 3. In the case of a circular saw the cutting edges would lie on a circle concentric with the axis of rotation of the blade body.

It will be understood from the forgoing that the blade represented by Figures 1 and 2 is a blade in which the cutting kerf widths of the tips of the blade are of a constant width.

Referring now to Figure 3, this Figure is a plan view of a section of a band saw blade of generally similar construction to that shown in Figures 1 and 2.

However, in accordance with an aspect of the invention the invention the teeth of the blade are considered to divided into successive groups each including a predetermined number of successive teeth, and the kerf widths of successive teeth within a group are successively different from tip to tip. This variation is in accordance with a predetermined pattern of variation.

In particular, during the manufacture of the saw blade, at the stages at which the cutting tips are machined to obtain the requisite relative angular and dimensional relationships between the several faces of the tips falling within a group of successive teeth, the tips are machined in such manner that the kerf widths of tips within such groups successively vary from a minimum width to a maximum width and from said maximum width to said minimum width.

In a particular series of dimensional variation in accordance with a particular cutting pattern within a group if the first tip of group has the minimum kerf width of 0.65 millimetres, the kerf width of the next adjacent tip was 0.73 millimetres, the kerf width of the next following tip was 0.80 millimetres, the kerf width of the next following tip was 0.73 millimetres, whilst the kerf width of the next folowing tip was 0.65 milimetres. This being followed by the next tip of the following group anrad thus having a width of 0,73 millimetres. This sequence was repeated in the adjacent groups of tips, wherein in each case the first tip of the second group was regarded as being the last tip of the immediately preceding group and so on throughout the total number of teeth on the blade .

It will be appreciated that other specific dimensional relationships between successive groups may be used provided that a regular pattern of increase and decrease of the kerf widths within a group is maintained.

Furthermore, the number of tips incorporated within a group can be other than that discussed in relation to Figure 3, thus for example a group could involve six, seven or more tips etc. of successive tips. What ever the number of tips in a group the height variation would effectively be in step with the kerf width variation. That is the highest cutting edge would be assocated with the maximum kerf width and so on. It has been found that a saw blade whose tips had been machined in accordance with the proposals of the invention had a longer operational life as compared with a saw of the same dimensions and made of the same materials and whose teeth were ground to the same angular relationships and dimensions other than the varying kerf width dimension .

It was also found that it was possible to run the blade, in terms of cutting speeds at higher speeds than those for satisfactory operational performance of the previously known grinding profiles for the tips.

As a further consequence of the grinding method proposed by the present Application it has been found that the improvements in operational efficiency enabled reduction of input power to achieve the same cutting proficiency.

Figure 4 very schematically illustrates a segment of a band saw blade in which the heights of the tips vary.

In the Figure for convenience of illustration the actual tips have not been shown. In the Figure, also to demonstrate the use of a different muraber of tips within a group Figure 4 illustrates the provision of seven tips to a group.

In the Figure 4 the tips have been numbered in a manner similar to the tips of Figures 1 to 3.

The parameters for the variation in the cutting edge heights can be set out as follows:-

Tooth pitch 20mm - 60mra (regular pitch or variable pitch, the pitch being the separation between adjacent cutting edges) .

Tooth height 5mm to 25mm. (this being the height between the cutting edge and the base of the tooth gullet).

Hook angle ranging between 0 degrees to 45 degrees positive .

Back angle ranging between 9 degrees to 25 degrees positive

The number of teeth included in a group or segment 2 teeth to 20 teeth.

Height difference between highest and lowest tooth in a segment Omm to 10mm.

Height difference between one tooth and the next Omm to a maximum of 2 mm.

Claims

1. A method of preparing a cutter tool such as a saw blade for operational use in which the tips of the tool/blade are regarded as forming successive groups, each of a predetermined number of successive tips, and in which the kerf widths of successive tips cutting edges within a said group vary.

2. A method as claim in claim 1, and wherein the kerf widths of the tips within a group successively vary from a minimum width to a maximum width and from said maximum width to said minimum width.

3. A method as claimed in claim 1 or 2, and in which the variation of the kerf width is according to a regular pattern of width variation.

4. A method as claimed in Claim 1 or 3, and wherein the variation of the kerf width within a group increases and descreases in two stages that are similar to each other.

5. A method as claimed in any one of claims 1 to 6, and in which the heights of the tip cutting adges vary from one tooth to the next.

6. A method as claimed in claim 5, wherein the variation in the cutting heights is according to the following relationships with a tool having a tooth pitch of 20mm - 60mm (regular pitch or variable pitch) tooth height between 5mm to 25mm, a back angle ranging between 9 degrees to 25 degrees positive, the number of tips included in a group or segment ranging from 2 teeth to 20 teeth, height difference between highest and lowest tips in a segment ranging from Omm to 10mm, and the height difference between one tip and the next ranging between Omm to a maximum of 2 mm.

7. A cutter tool such as a saw blade in which the cutting edges of the tool/blade effectively form successive groups of cutting edges, each group including a predetermined number of edges, and in which the kerf widths of such successive tips within a group vary according to a predetermied pattern of width variation.

8 A cutter tool claimed in claim 7, and in which the kerf widths of the tips within a group successively vary from a minimum width to a maximum width and from said maximum width to said minimum width.

9. A cutter tool as claimed in claim 8, and wherein the variation of the kerf width within a group increases and decreases in two stages that are similar to each other.

10. A cutter tool in which the heights of the cutting edges vary from one tooth to the next.

11. A cutter tool as claimed in any one of claims 7,8 or 9, and in which the heights of the cutting edges vary from one tooth to the next.

12. A cutter tool as claimed in claim 10 or 11, wherein the variation in the cutting heights is according to the following relationships with a tool having a tooth pitch 20mm - 60mm (regular pitch or variable pitch), tooth height 5mm to 25mm, back angle ranging between 9 degrees to 25 degrees positive, the number of tips forming a group being from 2 tips to 20 tips, height difference between highest and lowest tips in a group being from Omm to lOmra, and height difference between one tip and the next being fromOmm to a maximum of 2 mm.