GB2559599A

GB2559599A - Improvement to saw blades

Info

Publication number: GB2559599A
Application number: GB1702278.1A
Authority: GB
Inventors: Robin Maxey David; Timothy Maxey Simon
Original assignee: Ernest Bennett & Co Darlington Ltd
Current assignee: Ernest Bennett & Co Darlington Ltd
Priority date: 2017-02-10
Filing date: 2017-02-10
Publication date: 2018-08-15
Anticipated expiration: 2037-02-10
Also published as: GB201702278D0; GB2559599B

Abstract

A saw blade 100 with a body 102 having a back edge 108, a front edge 114 and parallel sides between the edges. There are a plurality of teeth 130, 132 on the front edge 114 with a gullet region 116 between each tooth and the adjacent tooth. The gullet region is angled such that the front edge is non-perpendicular between the two parallel sides (Fig 5A-C). The angled surface may be between 5 to 85 degrees relative to one of the sides and there may be a pair of opposed angled surfaces (124, Fig 5A) with a flat surface (122, Fig 5A), perpendicular to the sides, between them. The teeth may be arranged in pairs such that a leading tooth 130 extends further from the back edge 108 than the trailing tooth 132 in any pair. The back surface 112 of the leading tooth may be angled in the same way as the gullet region or it may be flat; extending perpendicularly between the two sides. The invention serves to reduce the risk of failure during use and extend the service life of a blade.

Description

(71) Applicant(s):

Ernest Bennett & Company (Darlington) Limited (Incorporated in the United Kingdom)

Aviation Way, Durham Tees Valley Airport, DARLINGTON, Durham, DL2 1NA, United Kingdom (72) Inventor(s):

David Robin Maxey Simon Timothy Maxey

(51) INT CL: B23D 61/12 (2006.01)
(56) Documents Cited:
GB 2360964 A	GB 1231097 A
GB 1214259 A	GB 0546114 A
EP 0982093 A1	EP 0725701 A1
WO 1989/011937 A1 US 1354439 A JPH01210267	DE 000558907 C

(58) Field of Search:

INT CL B23D, B27B

Other: EPODOC, TXTE, TXTCN, TXTKR, TXPJPEA, TXTJPEB, WPI (74) Agent and/or Address for Service:

Tandem Patents Limited

Grange Farm, Wetherby Road, Little Ribston,

Wetherby, Yorkshire, LS22 4EP, United Kingdom (54) Title of the Invention: Improvement to saw blades Abstract Title: Saw blade with angled gullet surface (57) A saw blade 100 with a body 102 having a back edge 108, a front edge 114 and parallel sides between the edges. There are a plurality of teeth 130, 132 on the front edge 114 with a gullet region 116 between each tooth and the adjacent tooth. The gullet region is angled such that the front edge is non-perpendicular between the two parallel sides (Fig 5A-C). The angled surface may be between 5 to 85 degrees relative to one of the sides and there may be a pair of opposed angled surfaces (124, Fig 5A) with a flat surface (122, Fig 5A), perpendicular to the sides, between them. The teeth may be arranged in pairs such that a leading tooth 130 extends further from the back edge 108 than the trailing tooth 132 in any pair. The back surface 112 of the leading tooth may be angled in the same way as the gullet region or it may be flat; extending perpendicularly between the two sides. The invention serves to reduce the risk of failure during use and extend the service life of a blade.

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3/3

Improvements to Saw Blades

The present invention relates to saw blades and in particular, but not exclusively, the present invention relates to improvements to bandsaw blades to at least reduce the risk of failure during use and in turn extend the service life of a bandsaw blade.

A bandsaw uses a long sharp blade consisting of a continuous band of toothed metal stretched between two or more wheels to cut material. They are used principally in woodworking, metalworking, and lumbering, but may cut a variety of materials.

There are several factors that may affect band saw blade life and cause blade failure. These include weld breakage, blade tension, speed and feed rate, break-in procedure, tooth pitch, chip brush and the qualities of the material being cut. One of the key factors to be considered is the tension of the blade. Inaccurate setting of bandsaw blade tension can lead to body breakage, cracks on gullets and/or cracks is on the back edge of the blade. Gullet cracking as a result of excessive tensile strain in the blade can be caused by a number of variables typically relating to the machine set up and not the blade itself. For example, the band may not be running straight, the blade guides may be too tight, the blade tension may be too high, the feed rate of the material being cut may be too heavy, the speed rate may be too fast, the feed pressure may be too high, the running time may be too long, the coolant flow may be too low, the coolant mix may be incorrect/compromised, the blade guide arms may be misaligned, the guide wheel/s may be damaged, the guide wheel bearings may be worn, and/or the guide-to-wheel alignment may be out. These are all known causes of gullet cracking. However, they are all variables and are prone to change during use of the saw and lifetime of the blade. They are dependent on correct user set-up, monitoring and adjustment over time which are inconsistent and are all subject to human error. In an attempt to prolong the life of a saw blade, and in particular to reduce cracking, the shape of each gullet extending between adjacent teeth of the blade is regularly maintained by manual sharpening and grinding of the saw blade. However, this is particularly labour intensive and it is impossible for even a skilled saw filer to be consistent across all gullets and blades. Furthermore, a conventional saw blade requires regular maintenance which results in costly downtime of the saw.

Improvements to saw blades, in particular bandsaw blades, are therefore required to at least mitigate one or more of the abovementioned problems.

According to a first aspect of the present invention there is provided a saw blade comprising:

a body portion having a back edge region, a front edge region and substantially parallel sides extending therebetween; and a plurality of spaced apart cutting teeth located along the front edge region and defining a gullet region of the body portion between each adjacent pairs of said teeth;

wherein the front edge region of the gullet region comprises at least one angled surface extending non-perpendicularly between the substantially parallel sides of the body portion.

is Optionally, the at least one angled surface of the gullet region defines an angle from around 5 degrees to around 85 degrees relative to a respective one of the parallel sides of the body portion.

Optionally, the angle is from around 20 degrees to around 80 degrees.

Optionally, the at least one angled surface comprises a pair of opposed and angled chamfered surfaces each located on a respective side of a substantially flat and perpendicularly oriented front edge surface.

Optionally, the at least one angled surface extends at least partially along a length of the front edge region of the gullet region.

Optionally, the at least one angled surface extends at least partially along one side of the front edge region and at least partially along the other side of the front end region.

Optionally, the at least one angled surface extends fully along one or both sides of the front edge region of the gullet region.

Optionally, the at least one angled surface extends at least partially along a back surface of at least one of said teeth.

Optionally, at least each leading tooth of each adjacent pair of said teeth comprises the at least one angled surface at least partially along the back surface thereof.

Optionally, the at least one angled surface extends from a tip of each leading tooth to a face surface of a trailing tooth of the respective adjacent pair of teeth.

Optionally, a tip of each trailing tooth is spaced a greater distance from the back edge region of the body portion than the tip of the leading tooth in each respective pair of adjacent teeth.

Optionally, the back surface of each trailing tooth is substantially flat and extends substantially perpendicularly with respect to the substantially parallel sides of the body portion.

Optionally, the saw blade is a bandsaw blade.

According to a second aspect of the present invention there is provided a saw comprising a saw blade according to the first aspect of the present invention.

According to a third aspect of the present invention there is provided a method of manufacturing a saw blade, comprising the steps of:

providing a gullet region between adjacent teeth of a saw blade; and providing at least one angled surface to a front edge region of the gullet region, wherein the at least one angled surface extends non-perpendicularly between substantially parallel sides of a body portion of the saw blade.

Optionally, the at least one angled surface of the gullet region defines an angle from around 5 degrees to around 85 degrees relative to a respective one of the parallel sides of the body portion.

Optionally, at least each leading tooth of each adjacent pair of said teeth comprises the at least one angled surface at least partially along a back surface thereof.

Optionally, a tip of each trailing tooth is spaced a greater distance from a back edge region of the body portion than the tip of the leading tooth in each respective pair of adjacent teeth.

Optionally, the method further comprises forming the at least one angled surface at least partially along the gullet region in a longitudinal direction with respect to the saw blade.

According to a fourth aspect of the present invention there is provided a method of manufacturing a saw blade, comprising the steps of:

providing a gullet region between adjacent teeth of a saw blade; and machining an upper surface of the gullet region in a substantially longitudinal direction with respect to the saw blade.

Description of the Drawings

Certain embodiments of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 illustrates a side view of a section of a bandsaw blade in accordance with certain embodiments of the present invention;

Figure 2 illustrates section H-H of the saw blade of Figure 1;

Figure 3 illustrates section F of the saw blade of Figure 1;

Figure 4 illustrates an isometric view of the saw blade of Figure 1; and

Figures 5a to 5c illustrate different cross sections of the gullet region according to certain embodiments of the present invention.

Detailed Description io

As illustrated in Figure 1, a wide bandsaw blade 100 according to certain embodiments of the present invention includes a body portion 102 and a number of spaced apart cutting teeth 104 fixed to the body portion by welding or other suitable joining technique. The body portion 102 is typically made from sheet metal, such as a high carbon or alloyed spring steel or the like, and the teeth 104 are typically made from a high speed grade steel (HSS) wire, or the like, which has been welded to the body portion before the tooth profiles have been formed therein. Other suitable materials that may be attached to the tooth to form a tip are the existing parent material by swaging, hard metal tungsten carbide, or any superalloy cobalt bearing rod. This construction is generally known as a bi-metal bandsaw blade but it is also known to make the blade out of a single metal, wherein the teeth are optionally hardened by tempering or the like, and which is typically used for light duty applications, such as cutting soft timber.

The body portion 102 typically has a thickness of around 0.5mm to around 1 mm depending on its intended application. The width of the blade is defined by the distance between the tip 106 of each tooth and the back edge 108 of the body portion 102. The width of a bandsaw blade is typically between around 3mm and around 400mm depending on its intended application, e.g. a wide bandsaw blade is typically 50-400mm wide. The width of the illustrated blade is around 125 mm. The blade pitch is defined as the distance between the tips of adjacent teeth (as referenced ‘p’ in Figure 4) or the number of teeth per inch (or per 25mm). A saw blade may have a constant tooth pitch wherein the teeth are spaced equally or it may have a variable tooth pitch wherein the distance between adjacent teeth varies along the length of the blade, typically in groups of teeth. The blade pitch is typically between around 0.75 to around 32 teeth per inch. The distance between adjacent teeth of the illustrated embodiment, which has a constant tooth pitch, is around 45 mm. Each tooth 104 has a face surface 110 and a back surface 112. The tooth face surface 110 defines a rake angle a with respect to the vertical (as illustrated in Figure 3, i.e. perpendicular to a longitudinal axis of the blade) of around 25 degrees, but which can typically between around 0 to around 35 degrees depending on the application of the blade. The tooth back surface 112 defines a clearance angle β with respect to the horizontal (as illustrated in Figure 3, i.e. with respect to a io longitudinal axis of the blade) of around 12 degrees, but which can typically between around 5 degrees to around 25 degrees depending on the application of the blade.

The front edge 114 of the blade 100 defines a wave-like profile and includes a curved section 116 between adjacent teeth 130,132 known as the gullet or gullet region. Each gullet region 116 includes a leading substantially convex region 118 and a trailing substantially concave region 120. The gullet depth is defined as the distance between the tip of a respective tooth 104 and the lowest point in the ‘trough’ of the concave region 120 of the gullet 116. The gullet depth of the illustrated embodiment is around 15 mm but can typically be between around 10 mm to around

35 mm depending on the application of the blade. The radius of the concave region is around 5-50 cm, aptly around 10-20cm, and the radius of the convex region is around 5-50 cm, and aptly around 20-45 cm. The concave and/or convex regions may each be a single radius or may comprise two or more different radii. For example, as illustrated in Figure 3, the gullet region 116 includes (from right to left in the Figure) a two-part concave region 120 having radii of 13,5 mm and 19,27 mm and a two-part convex region 118 having radii of 45,3 mm and 22,9 mm. A curved gullet region, aptly having relatively large radii, further reduces the risk of stress concentrations and in turn cracks forming in use. Relatively low tooth heights are preferred whilst considering the area and volume of the gullet region to remove the timber removed by each individual tooth.

As best illustrated in Figures 4 and 5, the surface of the front edge 114 of the gullet region 116 is not substantially planar, i.e. it is not a single substantially flat surface extending perpendicularly between the parallel sides of the body portion 102. In contrast, as illustrated in Figure 5a, the gullet region 116 according to certain embodiments of the present invention is substantially chamfered to include a substantially flat front edge surface 122 extending between a pair of opposed and angled chamfer surfaces 124 wherein each chamfered surface defines a non5 perpendicular angle relative to a respective one of the parallel sides of the body portion 102.

Alternatively, as illustrated in Figure 5b, the gullet region 116 may have a single angled chamfer surface 126 extending between the parallel sides of the body portion io 102. Further alternatively, as illustrated in Figure 5c, the gullet region 116 may have a substantially curved convex surface 128 extending between the parallel sides of the body portion 102.

Although the entire length of the gullet region 116 of the saw blade 100 as illustrated in Figures 4 and 5a has a double chamfer to define a three-sided front edge 114 to the gullet region, the front edge 114 of the gullet region 116 may only partially include at least one angled surface, such as a single chamfer (Figure 5b) or other form of edge region, such as described above, along its length. For example, the concave region 120 may at least partially include at least one angled surface and/or the convex region 118 may at least partially include at least one angled surface. The angled surfaces of the convex and concave portions may be spaced apart or connected, they may be on the same or opposed sides of the gullet region 116, and they may define different angles Ω with respect to an axis perpendicular to the longitudinal axis of the blade (as illustrated in Figure 4). Aptly, the angle Ω is between around 5 degrees to around 85 degrees, and aptly between around 20 degrees to around 80 degrees. For example, each of the flat front edge surface 122 and the angled chamfer surfaces 124 of the gullet profile may have the same width (or length as viewed in Figure 5a) and the angle Ω may be around 45 degrees for both chamfer surfaces 124. Although not essential, a relatively shallow chamfer angle and a smooth finish to the gullet surface is aptly preferred.

The at least one angled surface 124,126,128 of the front edge 114 at least partially along a region of the gullet region 116 helps to reduce the loading and stresses induced on that part of the blade during use. The tensile stresses at the front edge

114 of the blade 100 in use are relatively high compared to the stresses experienced through the body portion 102 and the back edge 108 of the blade. Reducing the stresses in the front edge, particularly in the gullet region 116, reduces the risk of cracking and ensures the blade lasts longer and requires less maintenance, replacement and costly downtime of the saw.

As shown best in Figure 4, the at least one angled surface may extend at least partially along the back surface 112 of a tooth 130, and aptly at least partially along the back surface of every other tooth in the series of teeth. In the illustrated io embodiment, the three surfaces 122, 124 of the gullet 116 extend entirely along the length of every other leading tooth 130 of each pair of teeth 130, 132 to define a three-sided tooth tip 106 having the same edge profile as the gullet region 116. This provides each leading tooth 130 with a larger cutting edge, albeit a narrower top edge surface 122, compared to a conventional saw blade which allows each leading tooth 130 to prepare a first and relatively rough cut in a material, e.g. timber, with reduced loading and stresses being subjected to that tooth. The trailing tooth 132 in each pair of adjacent teeth 130,132 has a substantially flat single back surface 112 which finishes off the cut whilst also experiencing reduced loading and stresses in view of the ‘pilot’ cut performed by the leading tooth 130. Reduced loading and stresses on the teeth 130,132 ensures the saw blade lasts longer in service, requires less maintenance and downtime for the saw, and uses less energy during the cutting process. The at least one angled surface may also extend at least partially along the length of each trailing tooth 132, however in the illustrated embodiment (as best shown in Figure 4) the bevelled gullet region extends up to but not including the back surface 112 of each trailing tooth 132. Teeth having the at least one angled surface, e.g. a three-sided bevel profile, extending along the back surface and at the tip thereof, may improve the surface finish of the material being cut. According to an alternative embodiment of the present invention, the back surface 112 of each leading tooth 130 of each adjacent pair of teeth 130,132 may have at least one angled surface oriented in a first direction whilst the back surface of each trailing tooth 132 may have at least one angled surface oriented in a direction opposite to first direction such that the angled back surface of each tooth in a series of teeth alternates in direction along the blade. An advantage of this tooth arrangement is to even the wear pattern over the arrangement of teeth rather than loading each tooth with the same stress which in turn extends the service life of the saw blade and saw itself, reduces heat and noise, requires less power, and thus saves energy.

As also illustrated in Figure 4, the front edge surface 124 of the bevelled and convex gullet region 116 is continuous with the back surface 112 of the respective trailing tooth 132 so as to eliminate any shoulder between the tooth and the gullet region which may undesirably have a notch effect and in turn create a stress concentration and risk of fatigue and eventually cracking at the root of the tooth 132. The same may be applied at the interface between the face surface 110 of each tooth 130,132 io and the concave gullet region 116. Whilst the root of each tooth at the weld interface extends laterally outwardly to form a relatively small shoulder region, this interface is substantially curved to again reduce the undesirable effects of stress concentrations forming around this area in use. Such a curved interface also helps to spread the load being passed through each tooth and into the body portion 102 during use.

Furthermore, the tip of each trailing tooth 132 may be slightly higher (as viewed from the side in Figure 3) than the tip of its adjacent leading tooth 130. This may be achieved by decreasing the rake angle a and/or increasing the clearance angle β of each trailing tooth 132 and/or locating the tip 106 of each trailing tooth 132 a greater distance from the back edge 108 of the blade 100 than the tips of the leading teeth 130. The height difference between adjacent leading and trailing teeth 130,132 is about around 0-5mm, and aptly around 0.3 mm. This height difference contributes to the, or has a similar, finishing effect of the trailing ‘finishing’ teeth 132 as described above.

The gullet surface of a conventional bandsaw blade is typically formed by grinding which imparts grinding lines across the gullet front edge 114, i.e. in a direction perpendicular to the longitudinal axis of the blade 100. This lateral grinding lines have the undesirable effect of tiny notches along the length of the gullet region 116 and thus encourage cracking during use. In accordance with certain embodiments of the present invention, the at least one angled surface 124,126,128 is formed at least partially along the gullet region 116 by machining, grinding, filing, or the like, in the longitudinal direction to remove or at least smooth out the undesirable lateral grinding lines and thus further reduce the risk of cracking during use, and in turn ensure the blade lasts longer and requires less maintenance, replacement and costly downtime of the saw.

Certain embodiments of the present invention therefore provide an improved saw blade, particularly a wide or narrow bandsaw blade, which is less prone to cracking, particularly in the gullet region thereof, and thus has a longer service life than conventional saw blades, uses less energy (heat, sound, electrical) in use, requires less maintenance and replacement, and in turn results in less costly downtime of the saw itself.

Furthermore, when conventionally grinding a band saw blade the grinding wheel is perpendicular to the length of the saw blade and the grinding wheel therefore makes scratch marks across the line of the grinding surface. Dependent on the nature of the wheel (course/fine, hard/soft etc.) and the type of conditions the process is carried out, such as with or without coolant or cam or CNC machinery, these scratches form the preliminary stages of a minute crack so that when the saw blade is used and is placed under stress and load these small scratches begin to open up and under certain circumstances form deeper cracks. Additionally, the grinding wheel creates heat and pulls particles of steel across the surface whilst still adhering to the parent material, and on exit of the ground area the contact and grinding motion then creates a burr on the edge of the steel surface. This burr is ragged and generally can be harder than the surrounding area due to being heated by the grinding process. As it is ragged and hard it is less pliable than the parent material and more prone to cracking. By machining the surface of the tooth in the gullet region in a longitudinal direction of the blade, in accordance with certain embodiments of the present invention, and optionally using a less severe stock removal and finer particulate of grinding wheel, the incidence of cracking can be reduced. Furthermore, if the square edges of the blade with the burr attached are then treated by the same process, this time at an angle in accordance with certain embodiments of the present invention, cracking in use due to grinding effects is substantially eliminated.

Claims

1. A saw blade comprising:

2. The saw blade as claimed in claim 1, wherein the at least one angled surface of the gullet region defines an angle from around 5 degrees to around 85 degrees relative to a respective one of the parallel sides of the body portion.

3. The saw blade as claimed in claim 2, wherein the angle is from around 20 degrees to around 80 degrees.

4. The saw blade as claimed in any preceding claim, wherein the at least one angled surface comprises a pair of opposed and angled chamfered surfaces each located on a respective side of a substantially flat and perpendicularly oriented front edge surface.

5. The saw blade as claimed in any preceding claim, wherein the at least one angled surface extends at least partially along a length of the front edge region of the gullet region.

6. The saw blade as claimed in claim 5, wherein the at least one angled surface extends at least partially along one side of the front edge region and at least partially along the other side of the front end region.

7. The saw blade as claimed in claim 5 or 6, wherein the at least one angled surface extends fully along one or both sides of the front edge region of the gullet region.

8. The saw blade as claimed in any of claims 5 to 7, wherein the at least one angled surface extends at least partially along a back surface of at least one of said teeth.

9. The saw blade as claimed in claim 8, wherein at least each leading tooth of each adjacent pair of said teeth comprises the at least one angled surface at least partially along the back surface thereof.

10. The saw blade as claimed in claim 9, wherein the at least one angled surface extends from a tip of each leading tooth to a face surface of a trailing tooth of the respective adjacent pair of teeth.

11. The saw blade as claimed in claim 10, wherein a tip of each trailing tooth is spaced a greater distance from the back edge region of the body portion than the tip of the leading tooth in each respective pair of adjacent teeth.

12. The saw blade as claimed in any of claims 9 to 11, wherein the back surface of each trailing tooth is substantially flat and extends substantially perpendicularly with respect to the substantially parallel sides of the body portion.

13. The saw blade as claimed in any preceding claim, wherein the saw blade is a bandsaw blade.

14. A saw comprising a saw blade as claimed in any preceding claim.

15. A method of manufacturing a saw blade, comprising the steps of:

16. The method as claimed in claim 15, wherein the at least one angled surface of the gullet region defines an angle from around 5 degrees to around 85 degrees relative to a respective one of the parallel sides of the body portion.

17. The method as claimed in claim 15 or 16, wherein the at least one angled surface comprises a pair of opposed and angled chamfered surfaces each located on a respective side of a substantially flat and perpendicularly oriented front edge surface.

18. The method as claimed in any of claims 15 to 17, wherein at least each leading tooth of each adjacent pair of said teeth comprises the at least one angled surface at least partially along a back surface thereof.

io

19. The method as claimed in claim 18, wherein the at least one angled surface extends from a tip of each leading tooth to a face surface of a trailing tooth of the respective adjacent pair of teeth.

20. The method as claimed in claim 18 or 19, wherein a tip of each trailing tooth is is spaced a greater distance from a back edge region of the body portion than the tip of the leading tooth in each respective pair of adjacent teeth.

21. The method as claimed in any of claims 15 to 20, further comprising forming the at least one angled surface at least partially along the gullet region in a

20 substantially longitudinal direction with respect to the saw blade.

22. A method of manufacturing a saw blade, comprising the steps of:

providing a gullet region between adjacent teeth of a saw blade; and machining an upper surface of the gullet region in a substantially

25 longitudinal direction with respect to the saw blade.

Intellectual

Property

Office

Application No: GB1702278.1 Examiner: Mr Alex Gillam