WO2024141962A1

WO2024141962A1 - Band saw blade for wood and a band saw blade manufacturing method

Info

Publication number: WO2024141962A1
Application number: PCT/IB2023/063305
Authority: WO
Inventors: Jan KLEPUSZEWSKI; Mateusz KLEPUSZEWSKI
Original assignee: Klepuszewska Grazyna
Current assignee: Klepuszewska Grazyna
Priority date: 2022-12-29
Filing date: 2023-12-28
Publication date: 2024-07-04
Anticipated expiration: 2025-06-29
Also published as: PL443323A1; EP4642583A1

Abstract

The present invention relates to a band saw blade for sawing of wood with longitudinal feed, comprising a body (1) with a tooth profile (2) shaped along the longitudinal edge, including straight teeth, left-set teeth, and right-set teeth, wherein the teeth are arranged in a grouping sequence consisting of six teeth with a configuration: the first straight tooth (S1), the first right-set tooth (R1), the first left-set tooth (L1), the second straight tooth (S2), the second left-set tooth (L2), and the second right-set tooth (R2).

Description

Band saw blade for wood and a band saw blade manufacturing method

The present invention relates to a band saw blade for wood and a method of manufacturing of the band saw blade, used as a cutting tool in band saws for sawing wood with longitudinal feed.

Monolithic band cutting tools with grouped teeth for sawing wood with longitudinal feed usually have the following teeth sequence: a) straight tooth, left-set tooth (when looking at the rake surface), right-set tooth, b) straight tooth, right-set tooth, left-set tooth.

Conventionally, one of the specified grouping sequences is repeated along the entire length of the band saw. In such solutions, there is a lack of a set sequence for the direction of setting for successive groups of teeth.

Band-type cutting tools for wood with grouped teeth, equipped with straight and set teeth without a defined sequence for the setting direction of successive groups of teeth, exhibit low durability due to a tendency for transverse vibrations during operation. Additionally, during operation, the initial setting value decreases due to the relaxation of stresses generated by the bending of the teeth during the setting operation. Therefore, it is necessary to set the teeth again before subsequent sharpening. Loss of the required setting value requires stopping the machine and replacing the saw.

In the technical field, there are known non-uniform band-type cutting tools for sawing wood with longitudinal feed, equipped with inserts made of Cr-Co-W superalloy or sintered carbide. The inserts are affixed to the tool body through methods such as welding, brazing, or hardfacing. Inserts constitute the working part, where the main cutting edge, as well as the side and back edges, are formed through grinding using known grinders for band-type tools. A non-uniform bandtype cutting tool for metal can have all main cutting edges, side edges, and back edges in a portion of the blade's width formed from high-speed steel, while the remaining part of the blade is made from low-alloy tool steel. Both parts of the blade are connected by welding. The weld connecting these two parts is parallel to the line on which the main cutting edges lie.

Band-type cutting tools for wood with blades made of Cr-Co-W superalloy or sintered carbide tend to accidentally chip edges during operation. The chipping is caused by transverse vibrations during operation due to the low transverse rigidity of the tool and the non-uniformity of the material being cut (mainly due to knots). Random chipping of the edges destabilizes the operation of band-type cutting tools for wood, compromising the quality of cutting and reducing the duration of effective operation.

The use of high-speed steel for the production of band-type cutting tools for wood is a favorable solution due to the greater ductility of this material compared to Cr- Co-W superalloy and sintered carbide. The solution used for metal cutting tools in the form of a band is characterized by excessive consumption of expensive highspeed steel. Additionally, for this case, achieving the required blade stereometry for cutting wood must differ from that used for cutting metals, presenting a significant technological challenge.

Furthermore, there are band-type tools with swaged teeth for sawing wood with longitudinal feed, typically made of low-alloy tool steel, 75Ni8, hardened and tempered to a hardness of 44 - 46HRC. The working part of these saws is formed using a traditional technology comprising three fundamental steps. In the first step, there is cold swaging (plastic deformation) of the cutting surface. The second step involves swaging of the side surfaces. The third stage is the formation of the teeth through grinding. Band-type tools with swaged teeth for sawing wood with longitudinal feed, manufactured using traditional technology, exhibit unsatisfactory durability. To increase the durability of the cutting edges, it is necessary to conduct an additional step in the form of surface induction hardening using high-frequency current. The resulted zone swaged in traditional technology is narrow and sufficient for a few (three to four) sharpenings. Any subsequent swaging must be preceded by grinding the remnants of the previous swaging. The total number of swaging cycles is determined by the allowable width of the blade or its fatigue or thermal wear.

The Polish patent PL215272B1 relates to a method of manufacturing a band saw and a band saw with extended durability. The mentioned method involves subjecting the preliminary material in the form of a steel strip to heat treatment using induction heating, followed by cold mechanical processing, including tooth setting and sharpening. After the tooth setting operation, the surfaces of the teeth and gullets of the band saw undergo surface treatment by shot peening, especially with ball-cast iron shot. Shot peening is carried out in the toothed zone to round the side edges of the teeth with a radius R2 ranging from 0.02 to 0.15 of the blade thickness and to round the edges of the gullets with a radius R1 ranging from 0.02 to 0.15 of the blade thickness, and subsequently, the shot peening process is carried out in the body zone of the band saw. The band saw, in turn, has teeth with edges of the gullets rounded on both sides, especially with straight- sharpened teeth, and rounded side edges of the teeth with a radius R2, the value of which is highest in the middle of the height of each tooth and ranges from 0.02 to 0.15 of the blade thickness. The rounding of the side edges transitions at the base of the tooth into the rounding of the gullet edges, and the surface layer of the gullet material and the surface layer of the tooth material, including the side surface, rake surface, and flank surface, has a depth from 0.02 to 0.1 of the blade thickness and increased hardness, preferably in the range of 5% to 20% relative to the body, while maintaining the body hardness from 40 to 64 HRC. From the description of the utility model application No. W.123817, a band saw blade for wood is known, designed for cutting both hard and soft wood using band saws, in the form of a metal strip, having on one longitudinal edge shaped a tooth profile with alternately positioned left-set teeth and right-set teeth. In the band saw according to W.123817, between successive pairs of left-set and right-set teeth, there is a tooth on which an insert is placed to increase its cutting edge.

In the European patent application EP3444060A1, a saw blade and a method of cutting a workpiece, especially a band saw blade for structural elements made of metal or its alloy, are disclosed. The band saw blade has cutting edges formed in a certain number of teeth. In one embodiment, a sequence of grouping the teeth of the band saw is presented, which includes 13 teeth defined in three subgroups containing 5 teeth, 3 teeth, and 5 teeth. The groups are distinguished by directional sets with different setting values (larger and smaller). Importantly, the disclosed sequence of blade grouping in the cited application aims to increase the durability of the saw.

The technical problem faced in the present invention is to provide a band saw blade for sawing wood with longitudinal feed that exhibits reduced edge dulling intensity and diminished tendency for transverse vibrations during operation, aiming to enhance durability and extend the effective operational time of the band saw. Additionally, it is desirable for the band saw blade to have good stability in contact between the saw and the guide, as well as a reduced tendency for chipping of the tooth edges, improving cutting quality and prolonging effective operational time. Another technical problem faced in the present invention is to provide a method of manufacturing a band saw blade that ensures the teeth's setting value does not decrease during operation, eliminating the need for periodic adjustments. It is also desirable for the manufacturing method to reduce the consumption of expensive materials, especially high-speed steel, thereby impacting the economic aspects of the manufacturing process. Furthermore, it is desirable for a method of manufacturing the band saw blade to allow for achieving a cutting tool with an increased number of possible sharpenings, elimination of unfavorable stresses and microcracks in the swaged zone, as well as an increase in the hardness and durability of the cutting edges.

In one aspect, the present invention provides a band saw blade for sawing wood with longitudinal feed, comprising a body with a tooth profile formed along the longitudinal edge, including straight teeth, left-set teeth, and right-set teeth, characterized in that the teeth arrangement is shaped in a grouping sequence comprising six teeth with the configuration: the first straight tooth, the first rightset tooth, the first left-set tooth, the second straight tooth, the second left-set tooth, the second right-set tooth.

Preferably, at least one tooth in the group has an oblique sharpening of a rake surface.

Preferably, an angle a of the oblique sharpening of the rake surface is within the range of 0.5 arcminutes to 5 degrees.

Preferably, a leading corner preceding the rake surface of the tooth lies on the side facing a band saw guide, while a trailing corner following the rake surface of the tooth lies on the opposite side in relation to the band saw guide.

Preferably, all teeth in each group of teeth have inserts placed in sockets.

Preferably, the insert is made of high-speed steel.

Preferably, at least one straight tooth in each group has a swaged tip.

In another aspect, the present invention provides a method of manufacturing a band saw blade for wood, comprising the following steps: a) providing initial material in the form of a steel strip, b) calibrating the steel strip to the desired width and cutting teeth to obtain a body that has a tooth profile formed along the longitudinal edge, c) setting the teeth designed for setting to obtain a tooth profile comprising leftset teeth and right-set teeth, characterized in that in step c) the teeth are set in a grouping sequence comprising six teeth with the configuration: the first straight tooth, the first right-set tooth, the first left-set tooth, the second straight tooth, the second left-set tooth, the second right-set tooth.

Preferably, after step c), at least one tooth in the group of teeth is sharpened to obtain an oblique sharpening of a rake surface of the tooth.

Preferably, in step b), in the positions where all teeth of each group of teeth occur, sockets are cut, and then inserts are placed in them through welding or brazing.

Preferably, after placing the inserts in the sockets, a two-stage heat treatment of the band saw blade is carried out, involving hardening and tempering of the body to a low hardness of 38HRC to 51HRC, followed by hardening and tempering of the inserts to a high hardness above 55HRC.

Preferably, in step b), in the position of at least one straight tooth of each group of teeth, the tip of the straight tooth is swaged.

Preferably, after swaging the tips of straight teeth, a two-stage heat treatment of the band saw blade is carried out, involving hardening and tempering of the body to a low hardness of 38HRC to 51HRC, followed by hardening and tempering of the tooth tips to a high hardness above 55HRC.

The band saw blade for wood according to the present invention, thanks to the use of set teeth with the following grouping sequence and orientation relative to the band saw guide: first straight tooth, first right-set tooth, first left-set tooth, second straight tooth, second left-set tooth, second right-set tooth, repeated along the entire length of the longitudinal edge of the body, on which the teeth are located, ensures alignment of all cutting edge corners, resulting in reduced intensity of cutting edge dulling. As a result, the effective operational time of the cutting tool in the form of the band saw blade is extended. Importantly, setting the teeth before the two-stage heat treatment operation reduces the adverse phenomenon of decreasing tooth setting value during the operation of the band saw blade, eliminating the need for adjustments. Furthermore, the oblique sharpening applied to the rake surface of the tooth, along with the leading edge preceding the rake surface lying on the side of the band saw guide and the trailing edge following the rake surface lying on the opposite side in relation to the band saw guide, ensures stability in the contact of the band saw blade with the saw guide and additionally reduces the intensity of cutting edge dulling, directly translating into an extension of the effective operational time of the band saw blade according to the present invention.

Moreover, in the band saw blade according to the present invention, thanks to the use of inserts, especially those made of high-speed steel, it is possible to carry out more precise sharpening while maintaining limited material consumption, even up to 90% less compared to a solution where high-speed steel is welded throughout the length of the blade with the same thickness as the blade. Importantly, inserts made of high-speed steel exhibit a reduced tendency to chip at the corners, which positively affects the reliability and durability of the resulting cutting tool.

Additionally, it is worth mentioning that shaping the swaged teeth of the band saw blade before the heat treatment process allows for the formation of a wider working part, increasing the achievable number of sharpenings. Furthermore, during the heat treatment process, unfavorable stresses remaining from the swaging process are eliminated. As a result, the swaged area formed is free from microcracks and exhibits greater hardness. This directly contributes to increased durability of the cutting edges after each sharpening. Additionally, the broader working part of the swaging allows for an increased number of sharpenings until the total permissible working time of the band saw blade is reached in terms of fatigue resistance.

Moreover, the conducted two-stage heat treatment of the cutting tool, where initially the hardening and tempering of the band saw blade body to low hardness of 38HRC - 51HRC is provided to achieve the highest fatigue strength, followed by the hardening and tempering of inserts or swaged areas to high hardness above 55HRC, contributes to the extension of the effective operational time of the cutting tool according to the present invention.

The solution according to the present invention has been presented in the following embodiments and is illustrated in the drawing, where Fig. 1 shows a view from the back side (Pp) of a section of a band saw blade according to the first embodiment, Fig. 2 shows a view of the rake surface from Fig. 1, Fig. 3 shows a side view of a section of a band saw blade from Fig. 1, Fig. 4 shows a view from the back side (Pp) of a section of a band saw blade according to the second embodiment, Fig. 5 shows a view of the rake surface from Fig. 4, Fig. 6 shows a view from the back side (Pp) of a segment of a band saw blade according to the third embodiment, Fig. 7 shows a view of the rake surface from Fig. 6, Fig. 8 shows a side view of a segment of a band saw blade from Fig. 6, Fig. 9 shows a view from the back side (Pp) of a segment of a band saw blade according to the fourth embodiment, Fig. 10 shows a view of the rake surface from Fig. 9, and Fig. 11 shows a side view of a segment of a band saw blade from Fig. 9.

Example 1

An embodiment of a band saw blade according to the present invention is depicted in the view from the back side (Pp) in Fig. 1 and in a view of the rake surface 4 in Fig. 2, and in the side view in Fig. 3. As shown in the figures, the band saw blade designed for sawing wood with longitudinal feed, comprises a body 1, along the longitudinal edge of which a tooth profile 2 is shaped, including straight teeth, left-set teeth, and right-set teeth. According to the present invention, the tooth profile 2 of the band saw blade is configured in a grouping sequence comprising six teeth with the following configuration: first straight tooth SI, first right-set tooth Rl, first left-set tooth LI, second straight tooth S2, second left-set tooth L2, and second right-set tooth R2. The mentioned grouping sequence is repeated along the entire length of the longitudinal edge of the band saw blade.

In this embodiment, the body 1 of the band saw blade is made of spring steel.

Without limiting the scope of the present invention, in this embodiment, the teeth forming the tooth profile 2 have a hardness above 55 HRC, while the body 1 of the band saw blade has a hardness ranging from 38 HRC to 51 HRC. The width of the body 1 of the band saw blade is, for example, 35 mm, the thickness of the body 1 is, for example, 1.1 mm, and the teeth forming the tooth profile 2 are spaced with a pitch of, for example, 22 mm.

The band saw blade presented in this embodiment has been manufactured using a method in which, in the first step, initial material in the form of a steel strip has been provided, and subsequently, the steel strip underwent a calibration process to achieve the desired width for the specific application, and the step of cutting the tooth profile has been carried out. After this step, the steel strip has the desired width, and the body 1 can be distinguished, with the tooth profile 2 shaped along its longitudinal edge. In the next step of the manufacturing method for the band saw blade according to the present invention, the setting of the teeth has been performed to obtain the tooth profile 2, including left-set teeth and right-set teeth, wherein the setting of the teeth is carried out to achieve a sequence of grouping comprising six teeth with the configuration: first straight tooth SI, first right-set tooth Rl, first left-set tooth LI, second straight tooth S2, second left-set tooth L2, second right-set tooth R2. Importantly, the setting of the teeth is performed when the material of the band saw blade has not yet undergone heat treatment. Only after the setting step, the heat treatment of the band saw blade is conducted to give it the final hardness, followed by the final sharpening of the tooth profile 2. Heat treatment usually involves hardening and tempering to achieve the desired hardness.

All steps of the manufacturing method of the band saw blade according to the present invention are carried out using techniques and technical means known and commonly used in the art, thus for the sake of clarity in this disclosure, they will not be described in detail. A person skilled in the art will be aware of the techniques and technical means used in the method according to the invention and will select suitable equipment and process parameters through routine engineering and adaptive work.

Example 2

The second embodiment of the band saw blade for wood according to the present invention is illustrated in Fig. 4 and 5. The construction of the band saw blade according to the second embodiment of the invention is substantially similar to the construction of the band saw blade according to the first embodiment of the invention, therefore, to maintain clarity in this disclosure, the description of similar structural elements has been omitted.

Unlike the first embodiment, the band saw blade according to the second embodiment includes at least one tooth SI, Rl, LI, S2, L2, R2 from each group with an oblique sharpening 3 of the rake surface 4 of the tooth. In some embodiments, it is possible to perform oblique sharpening 3 on the rake surface 4 of all teeth SI, Rl, LI, S2, L2, R2 in each group. The angle a of the oblique sharpening 3 of the rake surface 4 of the tooth ranges from 0.5 arcminutes to 5 degrees. The oblique sharpening 3 of the rake surface of the tooth or teeth is onesided. The leading corner 5 of the rake surface 4 of the tooth is located on the side of the band saw guide 10, while the trailing corner 6 of the rake surface 4 of the tooth is on the opposite side relative to the band saw guide 10. To obtain the band saw blade according to this embodiment of the invention, the method of manufacturing the band saw blade in the sharpening step involves giving selected teeth from each group an oblique sharpening 3 of the rake surface 4 of the tooth.

Example 3

The third embodiment of the band saw blade for wood according to the present invention is illustrated in Figs. 6, 7, and 8. The construction of the band saw blade according to the third embodiment of the invention is substantially similar to the construction of the band saw blade according to the first embodiment of the invention, therefore, to maintain clarity in this disclosure, the description of similar structural elements has been omitted.

In contrast to the first embodiment, the band saw blade according to the third embodiment of the invention includes all teeth SI, Rl, LI, S2, L2, R2 in each group of teeth that have inserts 7 placed in the sockets 8. The inserts 7 are made of a material different from the rest of the band saw blade, in particular, the inserts 7 may be made of high-speed steel or another material with high wear resistance. The inserts are placed in the sockets 8 of the body 1 of the band saw blade, made of spring steel. This allows for the reduction of consumption of high-quality materials such as high-speed steel.

The band saw blade presented in this embodiment is manufactured using the method outlined in the first embodiment, with the difference that, during the calibration of the steel strip to the width and cutting of the tooth profile, in the positions of all teeth SI, Rl, LI, S2, L2, R2 of both groups of teeth, sockets 8 are cut, and then inserts 7 are placed in them, which are attached to the sockets 8 by welding or brazing. The inserts 7 are placed and attached in the sockets 8 in a material that has not undergone heat treatment, while after the permanent attachment of the inserts 7 in the sockets 8, a two-stage heat treatment of the band saw blade is carried out, involving hardening and tempering of the body 1 to low hardness, and then hardening and tempering of the inserts ? to high hardness. The hardening and tempering technique and process parameters for this step will be known to those skilled in the art, who will apply appropriate technical means and process parameters to achieve the desired parameters through routine adaptive actions.

In the context of this patent description, the term 'low hardness' refers to the range from 38 HRC to 51 HRC, while the term 'high hardness' denotes values above 55 HRC.

Example 4

The fourth embodiment of the band saw blade for wood according to the present invention is illustrated in Figs. 9-11. The construction of the band saw blade according to the fourth embodiment of the invention is substantially similar to the construction of the band saw blade according to the first embodiment of the invention, therefore, to maintain clarity in this disclosure, the description of similar structural elements has been omitted.

In contrast to the first embodiment, the band saw blade according to the fourth embodiment includes at least one straight tooth SI or S2 in each group of teeth SI, Rl, LI, S2, L2, R2, which has a swaged tip 9 on the tooth. In some embodiments of the invention, the swaged tip 9 may be located on both straight teeth SI and S2 of each group of teeth SI, Rl, LI, S2, L2, R2, while in others, the swaged tip 9 may be located on only one of the straight teeth SI or S2 in each group of teeth SI, Rl, LI, S2, L2, R2.

The band saw blade according to the fourth embodiment is manufactured using the method described in the first embodiment, with the difference that after the calibration of the steel strip to the width and cutting of the tooth profile, in the positions of the straight teeth SI and S2 of each group of teeth SI, Rl, LI, S2, L2, R2, the tip of one straight tooth SI or S2 is swaged, or both tips of the straight teeth SI and S2 are swaged. Swaging is performed on material that has not undergone heat treatment, and after creating the swaging 9, a two-stage heat treatment of the band saw blade is carried out by hardening and tempering the body 1 to low hardness, followed by hardening and tempering the tooth tips to high hardness. The hardening and tempering technique and process parameters for this step will be known to those skilled in the art, who will apply appropriate technical means and process parameters as part of routine and adaptive engineering activities to achieve the desired parameters.

List of references:

1 - band saw blade body,

2 - band saw blade tooth profile,

3 - tooth oblique sharpening,

4 - tooth rake surface,

5 - leading corner of the tooth's rake surface,

6 - trailing corner of the tooth's rake surface,

7 - insert,

8 - insert socket,

9 - tooth tip swaging,

10 - guide, a - angle of the oblique sharpening,

SI - first straight tooth,

R1 - first right-set tooth, LI - first left-set tooth,

S2 - second straight tooth,

L2 - second left-set tooth,

R2 - second right-set tooth

Claims

1. A band saw blade for sawing wood with longitudinal feed, comprising a body (1) with a tooth profile (2) formed along its longitudinal edge, including straight teeth, left-set teeth, and right-set teeth, characterized in that the teeth are shaped in a grouping sequence comprising six teeth in the configuration: the first straight tooth (SI), the first right-set tooth (Rl), the first left-set tooth (LI), the second straight tooth (S2), the second leftset tooth (L2), and the second right-set tooth (R2).

2. The band saw blade according to claim 1, characterized in that at least one tooth of the group (SI, Rl, LI, S2, L2, R2) has an oblique sharpening (3) of a rake surface (4) of the tooth.

3. The band saw blade according to claim 2, characterized in that an angle a of the oblique sharpening (3) of the rake surface (4) of the tooth is in the range from 0.5 arcminutes to 5 degrees.

4. The band saw blade according to claim 2, characterized in that a leading corner (5) of the rake surface (4) of the tooth is located on the side of a band saw guide (10), and a trailing corner (6) of the rake surface (4) of the tooth is located on the opposite side in relation to the band saw guide (10).

5. The band saw blade according to any one of claims 1 to 4, characterized in that all teeth (SI, Rl, LI, S2, L2, R2) of each group of teeth have inserts (7) placed in sockets (8).

6. The band saw blade according to claim 5, characterized in that the insert (7) is made of high-speed steel.

7. The band saw blade according to any one of claims 1 to 4, characterized in that at least one straight tooth (SI, S2) of each group of teeth (SI, Rl, LI, S2, L2, R2) has a swaged tip (9).

8. A method of manufacturing a band saw blade for sawing wood with longitudinal feed, comprising the steps of: a) providing raw material in the form of a steel strip, b) calibrating the steel strip to the desired width and cutting teeth to obtain a body (1) which has, on its longitudinal edge, formed a tooth profile (2), c) setting the teeth intended for setting, to obtain a tooth profile (2) comprising: straight teeth, left-set teeth, and right-set teeth, characterized in that, in step c) the teeth are set in a grouping sequence comprising six teeth in a configuration: the first straight tooth (SI), the first right-set tooth (Rl), the first left-set tooth (LI), the second straight tooth (S2), the second leftset tooth (L2), the second right-set tooth (R2).

9. The method of manufacturing a band saw blade according to claim 8, characterized in that after step c), at least one tooth from each group (SI, Rl, LI, S2, L2, R2) is sharpened to obtain an oblique sharpening (3) of a rake surface (4) of the tooth.

10. The method of manufacturing a band saw blade according to claim 9, characterized in that an angle a of the oblique sharpening (3) of the rake surface (4) of the tooth is in the range of 0.5 arcminutes to 5 degrees.

11. The method of manufacturing a band saw blade according to any one of claims 8 to 10, characterized in that in step b), in positions where all teeth of each group of teeth (SI, Rl, LI, S2, L2, R2) occur, sockets (8) are cut, and then inserts (7) are placed in them and attached to the socket (8) by welding or brazing.

12. The method of manufacturing a band saw blade according to claim 11, characterized in that after placing and attaching inserts (7) in the sockets (8), a two-stage heat treatment of the band saw blade is carried out, including hardening and tempering the body (1) to low hardness, and then hardening and tempering of the inserts (7) to high hardness.

13. The method of manufacturing a band saw blade according to any one of claims 8 to 10, characterized in that in step b), in the position of at least one straight tooth (SI, S2) of each group of teeth (SI, Rl, LI, S2, L2, R2), the tip of the straight tooth (SI, S2) is swaged.

14. The method of manufacturing a band saw blade according to claim 13, characterized in that after swaging (9) the tips of the straight teeth (SI, S2), a two-stage heat treatment of the band saw blade is carried out by hardening and tempering the body (1) to low hardness, followed by hardening and tempering the tips of the teeth (SI, Rl, LI, S2, L2, R2) to high hardness.