CA2040049A1

CA2040049A1 - Band-saw blade

Info

Publication number: CA2040049A1
Application number: CA 2040049
Authority: CA
Inventors: Hans-Peter Leitinger
Original assignee: Individual
Current assignee: LEITINGER HANS PETER
Priority date: 1990-04-11
Filing date: 1991-04-09
Publication date: 1991-10-12
Also published as: FI911740A0; FI90213C; EP0453436A3; FI911740A; HU911135D0; HUT62224A; PL289812A1; EP0453436A2; FI90213B

Abstract

ABSTRACT OF THE DISCLOSURE

A strip-saw blade formed as a strip of metal extending along a blade plane has a front edge portion formed with a row of forwardly directed teeth and a rear edge portion. Measured perpendicular to the blade plane the rear edge portion is sub-stantially thicker than the front edge portion. In addition the blade is symmetrical to the blade plane and the blade is formed between the toothed front edge portion and the rear edge portion with a transition region having oppositely outwardly directed flank surfaces lying inward of respective planes tangenting the respective rear and front edge portions. These transition regions can have a height equal to three times the tooth height.
In fact the transition regions can be hollow ground so that they do not contact the workpiece at all.

Description

BAND-SA~ BLADE

SPECIEICA~ION

Field of the Invention The present invention relates to a strip-type-~saw blade, for instance for use on a band saw. More particularly this invention concerns a blade for such a saw, a method using such a saw, and a method of making band-saw blade.

Backqround o~ the Invention A standard band-saw blade is an endless or annular strip of metal having one edge formed with a row of teeth. This blade i8 spanned between two wheels that are rotated at high speed. A workpi~ce, typically a piece of wood, is advanced throuyh one o~ the straight blade stretche~ defined between and tangent to the two wheels so that a straight cut i5 formed in the workpiece. To this end of course the teeth project from the blade against the direction the workpiece is moved in and the workpiece is moved parallel to the plane of the stretch o~ the blade section cutting it, which is also parallel to the rotation axis of the blade drive wheels. Such a saw is normally used in a milling operation to cut planks or boards ~rom timbers.

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The main advantage o~ ~uch a saw is that the cut 1~
perfectly ~traightO In addition very thick timbsr can b~ cut readily with very uniform re~ults as compared, for example, to a cut by a circular saw where the angle of attack of the teeth on the workpiece varies as the distance to the blade rotation axis changes.
As with most saws, the main disadvantage i~ ~hat a portion of the workpiece is lost to sawdust and chips. The amount lo~t i5 determined by the thickness of the blade perpen-dicular to the cut or kerf it makes. The cut width is estab-lished by the width o~ the toothed part of the blade, which i~
typically som~what wider than the backing part of the ~lade due to alternate of~setting of the teeth to prevent the blade ~ro~
binding in the cut.
Thus the primary way to reduce waste is to make the blade as thin as possible. The cost of manu~acturing such a t~in blade is quite high as it must be delicat~ly machined and sharp-ened and must be made o~ very costly materials. In addition a very skinny blade is typically ~airly weak and is guickly worn out, and it is unable to dissipate the large amounts of heat gen~rated when cutting, so i6 subject to premature ~ailure.
Finally, such a very thin blade tends to vibrate and, khere~ore, produce an irregular cut.

Obiec~ o~ the Inventio~

It is there~ore an object o~ the present invention to provide an improved strip-type blade for a band saw or the like.
Another object is the provision o~ such an improved blade for a band saw which overeomes the above-given disadvan-tages, that i5 which produce~ a very narrow ker~. -A further object is to provide an improved method o~making such an improved blade.
Yet another object is to provide an improved method of cutting planks from a timber using such a blade.

Su~mary of the Invention According to this invention a strip-saw blade formed as a strip of metal extending along a blade plane has a ~ront edge portlon ~ormed with a row of forwardly directed teeth and a rear edge portion having measured perpendicular to the blade plane a rear edge portion that i5 substantially thicker than the front edge portion. With this arrangement it is kherefore possible to form a ker~ only l.Omm wide, while the rear edye portion of the blade is still 1.8mm w.ide. According to the invention the teeth lie wholly between planes flanking the blade plane at the front edge portion and spaced apart by a distance equal to substantial ly less than the thickness of the blade at the rear edge portion measured perpendicular to the blade plane. This distinguishes over a prior-art system where the teeth are bent out to altsrnate sides to form a kerf wider than the nominal blade width.
In accordance with a ~ur~her ~e~ture of the inventlon the blade i8 sy~metrical to the blade plane. In addition the blade i5 formed between the toothed front edge portion and the rear edge portion with a transition region having oppositely outwardly directed flank surfaces lying inward of respective planes tangenting the respective rear and front edge portions.
This transition region can have a height equal to three time~ the tooth height. In fact the tran~ition regions can be hollow ground so that they do not contact the workpiece at all.
Furthermore according ko the invention the front edge portion has flank~ that are parallel to each other and to the blade plane and the ~lanks of the transition region extend at an angle to the blade plane. In addition the teeth can be at least partially covered with stellite. More particularly the blade can have a steel core having V-section teeth provided with a stellite covering. The stellite coating is itselP wet-ground into the desired shape o~ the finished teeth. By means of spherical grinding it i5 possible to reduce the strip blank from which the blade is made from a skarting thickness of 1.8mm to l.Omm by taking off 0.4mm on each side of the tooth region. According to the invention the teeth project in the plane a predetermined distance equal to between three and six times the thickness at the front edge portion and the thickness at the front edge region is about l.Omm.

134~3 Such a blade according to the invention i~ u~ed wit~ a splitting wedge provided adjacent the blade and having an outer surface aligned with a plane tangenting the ~ront and rear edge regions of a respective side of the blade. This wedge keeps the workpiece virtually completely out of contact with the blade.
The blade according to the invention is used by contin-uously displacing it longitudinally without substantiall~ moving the blade plane while simultaneously displacing the workpiece back against the blade in a direction generally parallel to the blade plane so that the teeth cut the workpiece and ~orm a ~er~
therein. The workpiece i~ spread transverse to the blade plane downstream in the blade displacement direction of the front region of the blade to spread the kerf a~ the rear edge portion of the blade. It is possible to use the blade in a mill opera-tion by providing two such blades extending at an acute angle toeach other and displacing the workpiece against ~oth of them to separate r~spective portions from opposite sides of the work-piece. This in ef~ect strips a board ofP each side of the workpiece, balancing forces perfectly ~o the workpiece remains on center since the blade planes symmetrically flank and form identical acute angles with the direction of displacement of the workpiece. In such an operation according to this invention the blade is an endless band-saw blade and is advanced at a speed of between 40m/sec and lOOm/sec and is spanned over wheels of a diameter o~ about 2000mm. Wedges are normally employed as described above to ensure that the planks being cut off move away 782~

~rom the respe~tiv~ ~lade Furth~mor~ with thi arrange~ent lt is advantageou~ if the teeth pro~ect to one side only o~ the blade, that i~ toward the center of the workpiece.
The blade according to thi~ invention is made by forming teeth along a front edge of a metallic strip having a back edge and reducing the width of the front edye 80 that it i~
substantially less than that of th2 back edge. The wid~h can be reduced by rolling or by grinding. These teeth are provided with a covering oP a wear-resistant hard metal. Furthermore it is possible for the width to be reduoed by machining down only one side of the blade at the teeth, in which case the other side of the blade is built up at the teeth with a wear-resistant hard metal, while o~ course maintaining the toothed edge of the blade thinner than the rear portion thereof.

Brief Description o~ the Drawinq The above and other ob~ects, features, and advantages will become more readily apparent ~rom the followiny, re~erence being made to the accompanying drawing in which:
Fig. 1 is a large-scale cross section through the blade accordiny to this invention with one tooth shown in side view;
Fig~ 2 is a section through a blade assembly according to this invention while cutting a workpiece;
Fig. 3 is a section like Fig. 1 but showing how the blade o~ this invention is made;

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Fiq. 4 iB a vie~ like Fig. 2 but showing how succe~sive planks are cut fr~m a timber acco~ding to ~his inventlon;
Fig. 5 is a large-scale view like Fig. 4 but show~ng another system according to the invention; and Fig~. 6 and 7 are cross-sectional and side view~ o~ the blade o~ the system o~ Fig. 5.

Speci~ic Description As seen in Fig. 1 a strip-type blade according to this invention which may be used in a reciprocating saw or band saw has a front-end region 2 formed with teeth 11, an intermediate transition region 3, and a smooth rear-end region 4. The front region 2 is o~ a relatively small thickness t and the rear region 4 of a 6ubstantially greater thickness T, while the transition region flares outward symmetrically relative to a center plan2 P
to join the two regions at a ~ront edge 10 of the rear region 4.
In the illustrated e~bodiment the thickness T equals 1.8mm, the thickness t equals l.Omm and the blade 1 has a front to back dimension of 180m~.
Planes 5 and 6 tangent to the front edges of the front portion 2 and to the respective edges 10 lie outward of the flanlcs of the intermediate region 3. Thus a workpiece 9 can be cut by the blade 1 so that it is subdivided into two piece~ 7 and 8 that are pushed apart with inner surfaces o~ the boards 7 and 8 lying on planes P' forming continuations o~ the planes 5 and 6.

7821 M~

2~

The Xerf fonmed in the workpiece 9 will ~h~refore ~ave a wldth equal to the thickna~6 t, but ths blade it~el~ will hav~ a strength determined by its much thicker rear portion 4. In practice as ~een in Fig. 2 it i8 standard to provide splitter wedges 12 and 13 that lie on the planes P' to ensure proper spreading of the ker. In an exemplary arrangement the tooth extension is about 4mm to 6mm, much le~ than the 14mm that i~
customary, the wheel diameter is 1800mm to 2000mm, and the blade speed is 4Om/6ec to lOOm/sec.
Such a blade 1 is made as seen in Fi~. 3 by rolling and/or hollow grinding a rectangular-section blank 1' so that it has regions 2', 3', and 4' generally corresponding to the regions 2, 3, and 4, re3pectively, but with thQ ~ront edge region 2' formed with tapered flanks 14 and 15 and then ~tamping out the teeth 11. Thus each tooth 11 can be fitted with a cap 16 of ~tellite, a nonferrous alloy of chromium, cobalt, and tungsten, to increase tha teeth' 3 wear resistance.
Fig. 4 ~hows how a timber 20 can be engaged by two such blades 21 and 22 associated with respective wedges 30 (only one shown) to cut planks 23 and 24 from them, and then the thinner timber 20' can be engaged by two more such blade~ 25 and 26 to cut two more planks 27 and 28 from them. The view of the blade~
21, 22, 25, and 26 in this figure is tipped through 90 for clarity of view. In thi~ arrangement the kerf can be l.Omm wide in~tead of the 2.0mm width that i5 normal, ~or half the wa~te.

7821 ~ ~4~

Figs. 5, 6, and 7 ~how how a blade 2~ can be u~ed ~hose toothed front ed~e region 31 i8 bent to one side RO that a ~ingle plank 32 can be cut from ~he timber 200 The plane ~ dein~ by the outer ~lank o~ th~ portio~ 31 is aligned with ths correspond-ing side of the wedge 30 and lies at a very ~mall angle to thedirection D of displacement of the workpiece 20.
In this embodiment ths blade 1 has a overall w~th of 150mm and the tooth height is 15mm. Each tooth 33 is tipped with respect to the plane of the rear portion 35 of the blade. An inclined tooth flank 35 extends not to the base of the tooth 33, but only about two-thirds of the tooth height h1. The opposite flank 36 of each tooth 33 extends past the tooth base by a distance h2 which i8 more than the tooth height.
As seen in Fig. 6 such a blade i5 made ~rom a rectan-gular-section blank of strip steel as illustrated at dashed line 37. One side o~ this blank is provided with a wear-resistant stellite coating 38 to ~orm the ~urface forming the flanks 35.
The opposikQ ~ace i~ ground down to form the Planks 36. Thus the teeth are not Pormed by bending, but by grinding so that the metal of the blade is nok fatigued at all. It is also possible to hollow grind the blade as shown at 39.

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Claims

1. In a strip-saw blade formed as a strip of metal extending along a blade plane and having a front edge portion formed with a row of forwardly directed teeth and a rear edge portion, the improvement wherein measured perpendicular to the blade plane the rear edge portion is substantially thicker than the front edge portion.

2. The improved saw blade defined in claim 1 wherein the teeth lie wholly between planes flanking the blade plane at the front edge portion and spaced apart by a distance equal to substantially less than the thickness of the blade at the rear edge portion measured perpendicular to the blade plane.

3. The improved saw blade defined in claim 1 wherein the blade is symmetrical to the blade plane.

4, The improved saw blade defined in claim 3 wherein the blade is formed between the toothed front edge portion and the rear edge portion with a transition region having oppositely outwardly directed flank surfaces lying inward of respective planes tangenting the respective rear and front edge portions.

5. The improved saw blade defined in claim 4 wherein the front edge portion has flanks that are parallel to each other and to the blade plane and the flanks of the transition region extend at an angle to the blade plane.

6. The improved saw blade defined in claim 1 wherein the teeth are at least partially covered with stellite.

7. The improved saw blade defined in claim 6 wherein the blade comprises a steel core having V-section teeth provided with a stellite covering.

8. The improved saw blade defined in claim 1 wherein the teeth project in the plane a predetermined distance equal to between three and six times the thickness at the front edge portion and the thickness at the front edge region is about 1.0mm.

9. The improved saw blade defined in claim 1, further comprising a splitting wedge provided adjacent the blade and having an outer surface aligned with a plane tangenting the front and rear edge regions of a respective side of the blade.

10. A method of cutting a workpiece with a saw blade formed as a longitudinally elongated strip of metal extending along a longitudinal blade plane and having a front edge portion formed with a row of forwardly directed teeth and a rear edge portion, the rear edge being substantially thicker than the front edge portion measured perpendicular to the blade plane, the method comprising the steps of:
continuously displacing the blade longitudinally without substantially moving the blade plane;
displacing the workpiece back against the blade in a direction generally parallel to the blade plane so that the teeth cut away the workpiece and form a kerf therein;

spreading the workpiece transverse to the blade plane downstream in the blade displacement direction of the front region of the blade to spread the kerf at the rear edge portion of the blade.

11. The method defined in claim 10 wherein two such blades extending at an acute angle to each other are employed and the workpiece is displaced against both of them to separate respective portions from opposite sides of the workpiece.

12. The method defined in claim 10, wherein the blade is an endless band-saw blade and is advanced at a speed of between 40m/sec and 100m/sec and is spanned over wheels of a diameter of about 2000mm.

13. A method of making a strip-type saw blade, the method comprising:
forming teeth along a front edge of a metallic strip having a back edge; and reducing the width of the front edge so that it is substantially less than that of the back edge.

14. The method defined in claim 13 wherein the front-edge width is reduced by rolling.

15. The method defined in claim 13 wherein the front-edge width is reduced by grinding.

16. The method defined in claim 13, further comprising the step of providing the teeth with a covering of a wear-resis-tant hard metal.

17. The method defined in claim 13 wherein the width is reduced by machining down only one side of the blade at the teeth, the method further comprising the step of building up the other side of the blade at the teeth with a wear-resistant hard metal.