CA1084813A - Circular saw blade - Google Patents
Circular saw bladeInfo
- Publication number
- CA1084813A CA1084813A CA304,443A CA304443A CA1084813A CA 1084813 A CA1084813 A CA 1084813A CA 304443 A CA304443 A CA 304443A CA 1084813 A CA1084813 A CA 1084813A
- Authority
- CA
- Canada
- Prior art keywords
- blade
- strips
- peripheral part
- circular saw
- sawing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Sawing (AREA)
Abstract
ABSTRACT
A series of apertures are formed in a blade of a circular saw which define a plurality of strips interconnecting the toothed annular periph-eral part and the inside part of the blade. The strips are dimensioned so as not to hinder the expansion of the peripheral part and the width of the peripheral part is so great that its own weight can bring about the required tension due to the centrifugal force when the blade ro-tates.
A series of apertures are formed in a blade of a circular saw which define a plurality of strips interconnecting the toothed annular periph-eral part and the inside part of the blade. The strips are dimensioned so as not to hinder the expansion of the peripheral part and the width of the peripheral part is so great that its own weight can bring about the required tension due to the centrifugal force when the blade ro-tates.
Description
. ~hlstrom Osa~eyhtio, ~!ooolllarkku Finland iO84813 !:
CIRCULAR SAW BL~DE
BACKGROUND OF THE INVENTION
~. Field of the invention The present inven-tion relates to a circular saw blade consisting of a toothed annular peripheral part and an inside part and strips con-necting these to each other.
CIRCULAR SAW BL~DE
BACKGROUND OF THE INVENTION
~. Field of the invention The present inven-tion relates to a circular saw blade consisting of a toothed annular peripheral part and an inside part and strips con-necting these to each other.
2. Prior art .
Gang sa~s, circular saws or band saws can be used for sawing timber.
As the operation of a gang saw is cyclic the continuosly operating circular and band saws have because of high yield requirements become more popular. Both these saw types have, however, some disadvantages.
When a circular saw blade is rotating, it is subjected to centrifu~al forces. A state of tension, which can be defined in form of radial and tangential stresses, arises in the blade. The radial stress is the more detrimental of these stress direction as it makes the natural vibration frequency of the-blade approach the drive speed of the saw. A vibration of too high an amplitude makes the sides of the blade touch the timber in the sawing slot whereby friction heats anc deforms the blade and it sticks. The lateral vibration of the blade is usually restricted by a guiding element located at the front edge close to the timber. There can be guiding elements also elsewhere by the blade. Moreover, the blade must be stretched near the hub by hammering so that the radial stress by rotation of the blade can be substantial]y diminished and excess vibration of the blade avoided.
For the same purpose the blade can be hydraulically tensioned by an expanding hub. ~he decrease of the radial stress by these mea~s ~':-848~3 increases the tarlgential stress of the blade especially a-t the outer periphery which aids the blade to withstand better an increase oi temperature of its outer periphery and improves the sawing accuracy.
These measures give a satisfactory result with reasonable b~ade thic~-nesses presupposed that the peripheral speed of the blade is not too high, i.e. ma~. 45...60 m/s. Very high peripheral speeds make the hammering difficult and its results so inaccurate that they do not meet practical requirements. Highe:r peripheral speed would, however, be preferable as they would make higher feed speeds and higher yield possible.
The detrimental effect of the rise of temperature during sawing can be decreased by providing the circular blade with apertures close to its toothed periphery as presented in the US-patent 3.87~.763 so that several narrow strips are formed which connect the allnular peripheral part of the blade to its inside part. As the peripheral part is very narrow no tensioning forces substantially increasing its stiffness are creased by the centrifugal force when the blade rotates. Therefore the peripheral part must be constructed thick. This causes great sawing losses. As the body of the blade is large it is due to frictional heat subjected to deformation and vibration which are transmitted to the peripheral part.
SU~ RY OF THE INVENTION
It is an object of the invention to provide a circular saw blade for-sawing with high feed speeds, great sawing accuracy and small material losses.
It is a characteristic feature of the invention that the strips con-necting the inside part and the peripheral part do not essentially hinder the peripheral part from expanding and that the width of the peripheral part is so great that due to the radial acceleration its own weight can give the required tension when the blade rotates. For this purpose the width of the peripheral part must be 10...30 ~0, preferably 15...25 %
of the diameter of the blade and the lenght of the flexible part of the strips at least 10 /o of the diameter of the blade. When the blade ro-tates the tangential stress of the peripheral part is approximately three times greater than the strcss in the same area in a conventional circular saw blade. The max. radial stress, on the other hand, is only about 10 /o of t}-e corresponding s-tress in a conventional circular saw . ` ~ 10~3~81~ ~
blade. No vibr~tion problems arise and the peripheral spee~ can b~
increased accord-ing to the strength of the material The tension oI`
the peripheral part with a blade thickness of about 3 mm is already a-t a peripheral speed o~ appr. 100 m/s the same as in a band saw but the static stress is only one third of the s-tress in a band saw. If one spot of peripheral par-t is heated by friction the width of the periph-eral part does not hinder the elastic expansion of this spot in radial direction. Tangential expansion only causes an increase of the dia-meter o~ the peripheral part. During sawing the peripheral part of the blademustbe guided la-terally by guides which determine the opera-tion position of the blade. The centrifugal ~orce stretchesthe blade in the tangential direction and keeps the tension const~nt. The blade is made out of a circular saw blade by perforating its inside part so .
as to form strips which do not hinder expansion or stretching of the peripheral part but are capable of iransrnitting to i-t the rotating force !
and withstanding the feeding force. The aperture zone can not essen-tially guide the peripheral part of the blade laterally. Thus the potential vibrations of the inside part are no' transmitted to the peripheral part.
A sawing machine provided with a circular saw blade according to the invention has e.g. the~following advantages compared to a conventional circular saw:
;
- peripheral speed can be increased, - no hammering is required, - blade can be thinner, - noice level of sawing is decreased due to elimination of vibration, - sawing accuracy is better, - surface quality is be~ter.
Advantages cvmpared to a band saw:
- greater peripheral speed and sawing effect, - no dynamic bending stresses, - blade can be made thicker, thus also the static strength is better, - sawing accuracy is better, - teeth made of hard metal can be used, - due to hard metal teeth and sawing direction the qu~li-ty of the surfac is better, - cheaper sawing machine construction, -- cheapsr bllldes apd rl~:intena ce of bladss.
., 1C)~4813 DESCRIPTION OF THE DRAWINGS
The invention is described below in more detail with reference to the enclosed drawings in which:
Fig. 1 shows a schematic side view of a sawing machine provided with a circular saw blade according to the invention, Fig. 2 shows an apparatus according to Fi.g 1 in the direction of the arrow A, Fig. 3 shows an alternative embodiment of a circular saw blade according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In Figs. 1 and 2 the numeral 1 refers to a timber to be sawn which is fed by the feed roll pairs 2, 3 and 4, 5 of the sawing machine. The sawing machine has a circular saw blade 6 consisting of an annular toothed peripheral part 7 and an inside part ~ which are connected to each other by strips 9 made of the same blade blank. The strips form an angle wlth the radius of the blade so as not to hinder the expansion and stretching of the annular peripheral part. The inside part of the saw blade is connected to the driaw shaft 10 of the sawing machine by known methods. Guiding elements 11 guide the blade laterally.
In another embodiment of the saw blade 6 shown in Fig. 3 the annular toothed peripheral part 7 and the inside part 8 are connected to each other by generally tangential strips 9.
The representation of Figure 3 include reference symbols relating to the basic geometry of the blade according to the ~084813 invention. Thus, the letter a designates the width of the peripheral part of portion 7, i.e. the distance between the outer periphery of the blade and an outside circle 10 coincident with ends of equi-distantly spaced, generally tangential slot portions 11. Each of the generally tangential slot portions 11 merges with an inwardly directed slot portion 12, the inside ends of the slot portion 12 being coincident with an inside circle 13. Thus, the width of the annular region between the circles 10 and 13 is an area which can also be referred to as "an intermediate annular portion". It comprises a number of equi-distantly spaced slots, each comprised of a slot portion 11 and a slot portion 12.
Each slot portion 11 extends along a respective slot portion 12 of an adjacent slot to define therebetween an elongated rib or strip 9. Each strip 9 of Figure 3 has a length b and extends along an axis e, which is coincident, at forward or leading end of the strip 9, with leading end point c, and -at rear or trailing end of the strip 9 - with trailing end d.
It is apparent from the representation of the axis e in Figure 3, that each rib extends along a line which is generally tangential. ~owever, the strip 9 is at a location slightly shifted along the axis e against the sense of rotation of the blade, whereby the forward or leading end of the strip 9, represented by the point c is closer to the center 14 of rotation of the blade, than the trailing end, represented by the point d, as shown by the triangle c - 14 - d in Figure 3.
It is also apparent from Figure 3, that the size of area of 1![)~34~3 all ribs 9 combined is smaller than the size of the recessed area of the slots 11, 12 combined. In other words~ the surface area of each strip 9, as viewed in Figure 3, is smaller than the area of any one of said recesses 11, 12 as viewed in Figure
Gang sa~s, circular saws or band saws can be used for sawing timber.
As the operation of a gang saw is cyclic the continuosly operating circular and band saws have because of high yield requirements become more popular. Both these saw types have, however, some disadvantages.
When a circular saw blade is rotating, it is subjected to centrifu~al forces. A state of tension, which can be defined in form of radial and tangential stresses, arises in the blade. The radial stress is the more detrimental of these stress direction as it makes the natural vibration frequency of the-blade approach the drive speed of the saw. A vibration of too high an amplitude makes the sides of the blade touch the timber in the sawing slot whereby friction heats anc deforms the blade and it sticks. The lateral vibration of the blade is usually restricted by a guiding element located at the front edge close to the timber. There can be guiding elements also elsewhere by the blade. Moreover, the blade must be stretched near the hub by hammering so that the radial stress by rotation of the blade can be substantial]y diminished and excess vibration of the blade avoided.
For the same purpose the blade can be hydraulically tensioned by an expanding hub. ~he decrease of the radial stress by these mea~s ~':-848~3 increases the tarlgential stress of the blade especially a-t the outer periphery which aids the blade to withstand better an increase oi temperature of its outer periphery and improves the sawing accuracy.
These measures give a satisfactory result with reasonable b~ade thic~-nesses presupposed that the peripheral speed of the blade is not too high, i.e. ma~. 45...60 m/s. Very high peripheral speeds make the hammering difficult and its results so inaccurate that they do not meet practical requirements. Highe:r peripheral speed would, however, be preferable as they would make higher feed speeds and higher yield possible.
The detrimental effect of the rise of temperature during sawing can be decreased by providing the circular blade with apertures close to its toothed periphery as presented in the US-patent 3.87~.763 so that several narrow strips are formed which connect the allnular peripheral part of the blade to its inside part. As the peripheral part is very narrow no tensioning forces substantially increasing its stiffness are creased by the centrifugal force when the blade rotates. Therefore the peripheral part must be constructed thick. This causes great sawing losses. As the body of the blade is large it is due to frictional heat subjected to deformation and vibration which are transmitted to the peripheral part.
SU~ RY OF THE INVENTION
It is an object of the invention to provide a circular saw blade for-sawing with high feed speeds, great sawing accuracy and small material losses.
It is a characteristic feature of the invention that the strips con-necting the inside part and the peripheral part do not essentially hinder the peripheral part from expanding and that the width of the peripheral part is so great that due to the radial acceleration its own weight can give the required tension when the blade rotates. For this purpose the width of the peripheral part must be 10...30 ~0, preferably 15...25 %
of the diameter of the blade and the lenght of the flexible part of the strips at least 10 /o of the diameter of the blade. When the blade ro-tates the tangential stress of the peripheral part is approximately three times greater than the strcss in the same area in a conventional circular saw blade. The max. radial stress, on the other hand, is only about 10 /o of t}-e corresponding s-tress in a conventional circular saw . ` ~ 10~3~81~ ~
blade. No vibr~tion problems arise and the peripheral spee~ can b~
increased accord-ing to the strength of the material The tension oI`
the peripheral part with a blade thickness of about 3 mm is already a-t a peripheral speed o~ appr. 100 m/s the same as in a band saw but the static stress is only one third of the s-tress in a band saw. If one spot of peripheral par-t is heated by friction the width of the periph-eral part does not hinder the elastic expansion of this spot in radial direction. Tangential expansion only causes an increase of the dia-meter o~ the peripheral part. During sawing the peripheral part of the blademustbe guided la-terally by guides which determine the opera-tion position of the blade. The centrifugal ~orce stretchesthe blade in the tangential direction and keeps the tension const~nt. The blade is made out of a circular saw blade by perforating its inside part so .
as to form strips which do not hinder expansion or stretching of the peripheral part but are capable of iransrnitting to i-t the rotating force !
and withstanding the feeding force. The aperture zone can not essen-tially guide the peripheral part of the blade laterally. Thus the potential vibrations of the inside part are no' transmitted to the peripheral part.
A sawing machine provided with a circular saw blade according to the invention has e.g. the~following advantages compared to a conventional circular saw:
;
- peripheral speed can be increased, - no hammering is required, - blade can be thinner, - noice level of sawing is decreased due to elimination of vibration, - sawing accuracy is better, - surface quality is be~ter.
Advantages cvmpared to a band saw:
- greater peripheral speed and sawing effect, - no dynamic bending stresses, - blade can be made thicker, thus also the static strength is better, - sawing accuracy is better, - teeth made of hard metal can be used, - due to hard metal teeth and sawing direction the qu~li-ty of the surfac is better, - cheaper sawing machine construction, -- cheapsr bllldes apd rl~:intena ce of bladss.
., 1C)~4813 DESCRIPTION OF THE DRAWINGS
The invention is described below in more detail with reference to the enclosed drawings in which:
Fig. 1 shows a schematic side view of a sawing machine provided with a circular saw blade according to the invention, Fig. 2 shows an apparatus according to Fi.g 1 in the direction of the arrow A, Fig. 3 shows an alternative embodiment of a circular saw blade according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In Figs. 1 and 2 the numeral 1 refers to a timber to be sawn which is fed by the feed roll pairs 2, 3 and 4, 5 of the sawing machine. The sawing machine has a circular saw blade 6 consisting of an annular toothed peripheral part 7 and an inside part ~ which are connected to each other by strips 9 made of the same blade blank. The strips form an angle wlth the radius of the blade so as not to hinder the expansion and stretching of the annular peripheral part. The inside part of the saw blade is connected to the driaw shaft 10 of the sawing machine by known methods. Guiding elements 11 guide the blade laterally.
In another embodiment of the saw blade 6 shown in Fig. 3 the annular toothed peripheral part 7 and the inside part 8 are connected to each other by generally tangential strips 9.
The representation of Figure 3 include reference symbols relating to the basic geometry of the blade according to the ~084813 invention. Thus, the letter a designates the width of the peripheral part of portion 7, i.e. the distance between the outer periphery of the blade and an outside circle 10 coincident with ends of equi-distantly spaced, generally tangential slot portions 11. Each of the generally tangential slot portions 11 merges with an inwardly directed slot portion 12, the inside ends of the slot portion 12 being coincident with an inside circle 13. Thus, the width of the annular region between the circles 10 and 13 is an area which can also be referred to as "an intermediate annular portion". It comprises a number of equi-distantly spaced slots, each comprised of a slot portion 11 and a slot portion 12.
Each slot portion 11 extends along a respective slot portion 12 of an adjacent slot to define therebetween an elongated rib or strip 9. Each strip 9 of Figure 3 has a length b and extends along an axis e, which is coincident, at forward or leading end of the strip 9, with leading end point c, and -at rear or trailing end of the strip 9 - with trailing end d.
It is apparent from the representation of the axis e in Figure 3, that each rib extends along a line which is generally tangential. ~owever, the strip 9 is at a location slightly shifted along the axis e against the sense of rotation of the blade, whereby the forward or leading end of the strip 9, represented by the point c is closer to the center 14 of rotation of the blade, than the trailing end, represented by the point d, as shown by the triangle c - 14 - d in Figure 3.
It is also apparent from Figure 3, that the size of area of 1![)~34~3 all ribs 9 combined is smaller than the size of the recessed area of the slots 11, 12 combined. In other words~ the surface area of each strip 9, as viewed in Figure 3, is smaller than the area of any one of said recesses 11, 12 as viewed in Figure
3.
Finally, it will be readily apparent that the above general geometrical relationship as described wi~h reference to Figure 3 also applies to the embodiment of Figure 1. Therefore, the respective portions,namely the periphal part and the strips are referred to with the same reference numerals 7 and 8, respectively.
EXAMPLE
The stresses at different temperatures in a circular saw blade according to Fig. 3 were determined mathematically. The number of revolutions was 1800 r/min. Blade dimensions outer diameter1000 mm thickness 2,8 mm width a or peripheral part 190 mm length b of flexible part of the strips220 mm width of the strips50 mm ....
,~. , ~, .
.~;, l 10~348~3 .
It was proved that due to stiffness of the strips the tension of the peripheral part at an even temperature is only 2,6%
lower and when the peripheral part is 100C hotter than the inside part, 13,5% lower than the tension of a freely rotating annular blade. The tensioning force of the periphery is more than 2000 kg which gives it a greater stiffness in the lateral direction than is possible to achieve in an equally thick circular blade. The peripheral part is kept in the sawing direction by its own tension and by guides located at its sides outside the sawing area. The inside part increases the lateral stiffness of the connection only to a minimal extent.
Ihose skilled in the art will readily appreciate further embodiments differing from the preferred arrangements as described above but still falling within the scope of the present invention as recited in the accompanying claims.
Finally, it will be readily apparent that the above general geometrical relationship as described wi~h reference to Figure 3 also applies to the embodiment of Figure 1. Therefore, the respective portions,namely the periphal part and the strips are referred to with the same reference numerals 7 and 8, respectively.
EXAMPLE
The stresses at different temperatures in a circular saw blade according to Fig. 3 were determined mathematically. The number of revolutions was 1800 r/min. Blade dimensions outer diameter1000 mm thickness 2,8 mm width a or peripheral part 190 mm length b of flexible part of the strips220 mm width of the strips50 mm ....
,~. , ~, .
.~;, l 10~348~3 .
It was proved that due to stiffness of the strips the tension of the peripheral part at an even temperature is only 2,6%
lower and when the peripheral part is 100C hotter than the inside part, 13,5% lower than the tension of a freely rotating annular blade. The tensioning force of the periphery is more than 2000 kg which gives it a greater stiffness in the lateral direction than is possible to achieve in an equally thick circular blade. The peripheral part is kept in the sawing direction by its own tension and by guides located at its sides outside the sawing area. The inside part increases the lateral stiffness of the connection only to a minimal extent.
Ihose skilled in the art will readily appreciate further embodiments differing from the preferred arrangements as described above but still falling within the scope of the present invention as recited in the accompanying claims.
Claims
1. A circular saw blade comprising a toothed annular peripheral portion, an interior portion and an annular intermediate portion, said intermediate portion being formed by a plurality of alternating, equidistantly spaced elongate strips and recesses between each pair of adjacent strips, each strip having a leading end portion and a trailing end portion wherein:
(a) the width of said peripheral portion is 10-30%
of the diameter of the blade;
(b) the length of each of said strips is at least 10% of the diameter of the blade;
(c) the distance between each leading end portion and the center of rotation of said blade is less than the distance of teh respective trailing end portion and said center of said rotation; and (d) the surface area of each strip as viewed in the direction of the axis of rotation of the blade is smaller than the area of any one of said recesses as viewed in the said direction;
(e) the strips are disposed at an angle relative to generally radial direction;
whereby flexibility of the blade is provided which allows expansion and stretching of the annular peripheral portion during the operation of the blade.
(a) the width of said peripheral portion is 10-30%
of the diameter of the blade;
(b) the length of each of said strips is at least 10% of the diameter of the blade;
(c) the distance between each leading end portion and the center of rotation of said blade is less than the distance of teh respective trailing end portion and said center of said rotation; and (d) the surface area of each strip as viewed in the direction of the axis of rotation of the blade is smaller than the area of any one of said recesses as viewed in the said direction;
(e) the strips are disposed at an angle relative to generally radial direction;
whereby flexibility of the blade is provided which allows expansion and stretching of the annular peripheral portion during the operation of the blade.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA304,443A CA1084813A (en) | 1978-05-30 | 1978-05-30 | Circular saw blade |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA304,443A CA1084813A (en) | 1978-05-30 | 1978-05-30 | Circular saw blade |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084813A true CA1084813A (en) | 1980-09-02 |
Family
ID=4111584
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA304,443A Expired CA1084813A (en) | 1978-05-30 | 1978-05-30 | Circular saw blade |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1084813A (en) |
-
1978
- 1978-05-30 CA CA304,443A patent/CA1084813A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |