CA1226788A - Saw blade construction - Google Patents
Saw blade constructionInfo
- Publication number
- CA1226788A CA1226788A CA000453981A CA453981A CA1226788A CA 1226788 A CA1226788 A CA 1226788A CA 000453981 A CA000453981 A CA 000453981A CA 453981 A CA453981 A CA 453981A CA 1226788 A CA1226788 A CA 1226788A
- Authority
- CA
- Canada
- Prior art keywords
- band saw
- edge
- wheels
- saw
- band
- 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
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
- B23D61/00—Tools for sawing machines or sawing devices; Clamping devices for these tools
- B23D61/12—Straight saw blades; Strap saw blades
- B23D61/126—Straight saw blades; Strap saw blades having cutting teeth along both edges
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
- B23D61/00—Tools for sawing machines or sawing devices; Clamping devices for these tools
- B23D61/12—Straight saw blades; Strap saw blades
- B23D61/123—Details of saw blade body
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Sawing (AREA)
- Processing Of Stones Or Stones Resemblance Materials (AREA)
Abstract
SAW BLADE CONSTRUCTION
ABSTRACT OF THE DISCLOSURE
An improved saw particularly of the bandsaw or sash gangsaw variety having at least one cutting edge and a central portion of minimal thickness, the decrease in thickness from a cutting edge or a remote edge to its center either being linear or arcuate.
ABSTRACT OF THE DISCLOSURE
An improved saw particularly of the bandsaw or sash gangsaw variety having at least one cutting edge and a central portion of minimal thickness, the decrease in thickness from a cutting edge or a remote edge to its center either being linear or arcuate.
Description
SAW BLADE CONSrrRUCTION
BACKGROUND OF THE INVENTION
The following relates generally to saw blade configurations and more particularly a construction of a band saw or a sash type gang saw.
The optimum design for a saw such as a band saw or a sash gang saw would be one which has minimal thickness for the band which supports the cutting teeth so that friction and associated heat caused by the band rubbing against the material to be cut is held to a minimum. It is well known that the generation of friction and its associated heat if excessive can ruin the temper of the cutting portion which thereby accelerates the dulling of the cutting edge and the associated life of the band.
The treatment of cutting implements in general so as to temper same and provide requisite flexibility without an associated loss of sharpness at the cutting edge has been an art, the methods for which have been handed down from generation to generation as trade secrets. While band saws have been in existence for perhaps a century as we know them today, with few modifications to the basic structure having occurred during that interval, the supporting machinery associated with the band saw has improved remarkably within the last decade or so particularly with respect to automatic feeding of the work stock and the manipulation of the work stock so as to effect a plurality of cuts as is desired to provide a finished product With this associated automation, and for that matter with manual feeding, worst case scenarios are generally relied upon in determining feed rates and the like so that dulling of the cutting blade by excessive heat and friction with an associated loss in band saw Do sharpness can be avoided or manmade.
In known band saw manufacture design, one of the most important criteria in use is the proper tensioning of the band so that there is minimum flex along the leading cutting edge of the handsaw. To this end, handsaw fabrication techniques (and for that matter, sash gang saws) require that the linear length of the leading edge or cutting portion of the handsaw be of lesser magnitude than the edge remote therefrom so that the non cutting or trailing edge has a substantially convex contour, commonly referred to as a crown. In this manner, when the handsaw is appropriately tensioned between the rollers which support and drive the band saw, the leading cutting edge is the area that receives the initial tension and is therefore most taut. The leading edge most closely approximates a straight line when properly tensioned in an ideal case and to attain this driving blade flexor, one support roller is operatively connected to weights so gravity keeps the blade taut but displaced in the presence of wood consistency variation, such as snots.
A further ideal in addition having the leading or cutting edge define a straight line is to have the band itself be of a thickness approaching zero for two reasons. Firstly there would be an associated reduction of the steel used in fabricating the saw which provides with it a concomitant advantage in weight reduction. Obviously, the lighter the handsaw the greater the speed associated with the handsaw in its operation and a minimal amount of surface area is provided exposed adjacent the wood for heat build-up. Secondly, a handsaw which approximates zero thickness will result in less wood removal required in cutting (in the form of sawdust) which can provide a substantial increase in the amount of usable board feet from every cut and can translate into substantial savings in a large volume sawmill.
i Saving loath ox an inch on every cut would translate to a savings of $800,000 to' a company the magnitude of Weyerhauser or Georgia Pacific on an annual basis. By way of perspective, the blade according to the instant application saves eight or nine thousandths of an inch on every cut.
Timber conservation is a critical concern today since virgin forests in the United States are vanishing. The price of finished or sawn lumber has increased by 1.7% each year since 1900 while the cost of live trees while standing has increased 3.5~ each year. Moreover with vanishing virgin forests, the diameter of harvested trees is substantially less than it was even thirty years ago which manifests itself in a long felt but heretofore unsatisfied need in scaling up the efficiency in wood processing resulting in the instant invention.
A rule of thumb in the lumber industry is that a reduced loss of ~010 inches per saw cut equals a savings of fifty cents to one dollar per thousand board feet of lumber produced. The amount of wood saved by its not being reduced to sawdust by merely reducing the size of the kern by merely .031 inches would result in an increase in lumber yield of from one to three per cent with no associated increase in log costs. In many large mills, this would equate to an additional profit of about $280,000 annually.
Thus, thinness of the saw blade can have a profound impact on the profitability of a sawmill and the instant invention provides a substantive decrease in the amount of metal used in forming the saw blade and therefore a concomitant decrease in the amount of wood wasted as sawdust.
The following patents reflect the state of the art of which applicant is aware in so far as these patents appear to be germane to the patent process:
345,565 ~imonds jug. 3, 1886 1,736,444 Mullen Dec. 30, 1930 4,160;39~ ~ertini Jul. 10,- 979 The very old patent to Simonds teaches the use of a handsaw which, at the time the Simonds invention was made, referenced to a narrow saw (column 1 line I which was used to cut a curve within a minimum distance and therefore more closely corresponds to a coping saw both of which was hand manipulated and wound really not pertain to handsaws as they are used in sawmills. Any similarities therefore between Almonds and the instant application would appear to- be merely coincidental.
Similarly, the patent to Mullen teaches the use of a process for treating mill handsaws in which grinding is a known technique for removing high spots in the manufacture of the saw blade, and Figure 1 shows an exaggerated section of the saw wherein the central strip appears thinner than the two edges.
More particularly, ~uehlen shows in Figure 1 an exaggerated section ox a band saw, the central strip appearing thinner and longer than the edges which take the pull of the saw in use. There is not intended in his patent to be a measurable difference in the thickness and the illustration is an effort to show the effect of his process which is really not a manufacturing process but is a process of maintenance, subsequent to the manufacturing process, to be done on the sawmill premises.
the nexus of the Mullen patent is to remove internal stresses of the metal fibers which are unequal in magnitude one relative to the other so that they will all be under the same tensioning by reverse bending and stretching (page 2 lines ~-13). Firstly, it is problematical whether or not the steel at the time of the invention of Mullen required this type of stress relieving, and secondly, it is respectfully stipulated that the stress relieving treatment dictated by Mullen, using today's soft steel, would cause the very distortion which would approximate long use to characteristics or chronic abuse (page l lines 9-13, page 2 lines l-3). It is a specific object of the instant invention to reduce the amount of stretching, pulling, bending, etc. to retain as much of the natural elasticity of the steel so as to extend the useful life and flexibility of the saw in its intended work environment.
The patent to Burton appears to diverge even further from the subject matter of the instant application in that the end of the handsaw thereof does not have parallel edges and nothing to indicate that there is a variation in thickness thrilling.
The instant application is distinguished over the known prior art in that it provides either hollow formed blades or taper formed blades so as to eliminate either partially or totally the crown and thus the concomitant tension gradient of currently available band and sash gang saw blades. By having the dimension of the handsaw or sash gang saw be reconfigured as to be defined hereinafter, the appropriate tensioning of the band is programmed into the band itself when disposed upon band rollers, and virtually none of the elasticity of the steel by roller tensioning is lost and thereby the life of the steel would be extended due to the diminishment of peruse flexor. By having the major body portion of the saw band formed with a hollow taper, a concomitant decrease in the amount of clearance between adjacent teeth points can be manifested so that substantially less material will be removed in the cutting process Less cutting pressure would follow as a consequence, as would faster feed rates. The geometry of the saw according to the instant application when disposed upon the band support rollers would exhibit an improved geometrical strength by its preformed nature to thereby resist buckling resulting in greater cut accuracy.
When the accuracy improves, the yield from the raw material to improves considerably. Also, when less clearance is needed, a narrower chip is removed from the cut so that the sawdust holding gullets of the teeth can be utilized to better advantage by removing the same amount of chip size but converting from a wider chip to a longer chip for an increased rate of feed than that which is now possible. The gullets would thus be able to carry out more of the sawdust without spilling it from the sides of the saw while in the cut, thus further reducing friction and heat which has the most profound impact on saw life longevity. Since sawdust is removed along the cut, less power is required to move along at the same cut rate, and the teeth associated with the instant application tend to deflect less since the cut is narrower than the prior art. the differences in magnitude delineated hereinabove are incorporated herein again for purposes of contrast.
OBJECTS AND 5t)MMl~RY OF' EYE INVEN~lON
, - accordingly, this invention has an objective the provision of a new and novel band or sash gang type saw exhibiting characteristics of greater economies of scale and improved life along with faster feed rate.
A further object of this invention contemplates providing a device as characterized above which when installed in its cutting environment is so configured that the tension is formed as a gradient having the greatest amount of tension on the cutting edge of the blade which therefore defines a linear cutting edge.
A further Deject of this invention contemplates providing a device as characterized above which has substantially or partially eliminated the need for pre-tensioning and providing a crown and replacing same with a contour of the cutting blade which naturally causes the blade to assume its most beneficial profile when installed on a Andes cutting machine. In this manner, needless fatigue imposed by pre-tensioning has been minimized and difficulties in manufacturing processes acquitted with forming a crown will have been obviated. When suitably supported on pressure rollers to fix the blade in its cutting environment, the natural pattern of stresses are exhibited in the improved saw according to the instant application.
A further object of this invention contemplates providing a device as characterized above which is of minimal thickness thereby saving on metal associated with the blade and provides a kern of minimal width allowing a concomitant saving in material removed in the sawing process.
A further object of this invention contemplates providing a device as characterized above wherein the offset of adjacent teeth are substantially less than the prior art and the associated pullets work more efficiently in reducing heat, friction and removal of wood chips.
.
A further object of this invention contemplates providing a device as characterized above to extend the "flex life" (reduction of fatigue failure) of the steel associated with the saw without removing as much or any of the elasticity of the steel when roll tensioning.
A further object of this invention contemplates providing a device as characterized above to reduce the amount of saw distortion during its actual cutting use whereby higher speeds and lower friction and therefore extended life are possible.
- In one form of the invention, a saw having cutting teeth on opposed extremities when taken in section includes a central area of minimal thickness and a gradual increase in thickness from the center to the sectional extremities whereby the only area of the saw coming in contact with the medium-to be cut is actually the teeth. In addition, when suitably tensioned, the saw exhibits a natural tendency for the working edge to exhibit zones of greatest tautness in a natural manner so that minimal stressing of the blade is required to achieve attachment of the band to its machine, thereby reducing the amount of built in stress. By having the cutting teeth be the area of the saw blade which is expanded first, tension at that area is followed by a normal compression at an area most likely to receive the compression i.e., the center of the blade which can accommodate I
01 this additional compression not only by its diminished I dimension, but also by its contouring so that stress build up is 03 minimized and the lines of stress associated with the blade are 04 balanced, reducing the likelihood of bulging, buckling or 05 warping when given the opportunity due to excessive heat build 06 up -for example.
08 In another form of the invention, a blade having 09 a single cutting edge on one extremity when taken in section has a complementary edge formed and dimensioned to have If substantially the same thickness as the cutting edge immediately 12 inward from the offset tooth portion, and the taper is 13 geometrically offset relative to a central line so that 14 successive sharpening causes the central diminished area of the blade to migrate slowly toward the cutting edge of the saw.
16 Thus, the central concavity in the saw is caused to move as a 17 function of time as the saw is sharpened and allows for 18 migration of the thinnest portion of the blade from a side 19 opposite the center line adjacent the non-cutting edge to ultimately a side adjacent the cutting edge.
22 In general, the present invention is provided for 23 use in an industrial band mill, wherein a driven band saw is 24 mounted on a plurality wheels, each of which is substantially flat and has a front edge, and at least one of which may 26 constitute a driving wheel. The band saw has inner and outer 27 sides and further has a pair of edges, at least one of which has 28 cutting teeth formed thereon, wherein the edge with the cutting 29 teeth overhangs the respective front edges of the wheels, and wherein apparatus is provided for moving the wheels in a 31 direction substantially away from one another. The invention is 32 an improvement wherein the band saw is substantially free of _ g Jo 01 preceptors in its manufacture prior to use, the band saw being 02 concavely formed on a-t least its inner side and substantially 03 from edge to edge thereof wherein -the band saw has a 04 cross-sectional thickness which is substantially non-uniform 05 throughout and which decreases substantially uniformly edge to 06 edge towards -the approximate center of the band saw, such that 07 there is a reduced mass at the center of the band saw between 08 the edges thereof. A non-uniform radial gap is provided between 09 the band saw and each of wheels when the band saw is first lo mounted on the wheels, and when the wheels are moved away from 11 one another, the band saw will be stretched and the inner 12 surface of the band saw will become substantially flush against 13 the respective wheels in the operative position of the band saw 14 on the band mill, thereby eliminating the necessity of stressing the band saw by roll tensioning or the like during -the 16 manufacture thereof; and whereby the reduction of mass replaces 17 the expansion otherwise required by roll tensioning.
- PA -I
BRIEF DESCRIPTION OF TIE DRAWINGS
Figure 1 is a top plan view of a saw formed in accordance with the instant invention. While a band saw is depicted, it should be apparent that a sash type gang saw could be included also.
Figure 2 is a sectional view taken along lines 2-2 of Figure 1.
Figure pa is an alternative embodiment utilizing only one edge of the band as its cutting edge, whereas Figure 2 uses both edges as a cutting edge.
Figure 3 is illustrative of the true prior art currently in use.
BRIEF DESCRIPTION OF THE PREFERRED Embodiment Referring to the drawings now, wherein like reference numerals refer to like parts throughout the various drawing figures, reference numeral 10 is directed to a band saw in accordance with the instant invention.
,.
As shown in Figure 2, the saw blade in section according to the instant invention includes at opposed edges thereof cutting teeth 11 equidistant from the geometrical center of the blade, the geometrical center 10c having a thickness substantially less than its thickness immediately adjacent the teeth, shown as 10d. The rate of change of curvature from the area of the blade at 11 to its center may define a linear taper or an arcuate taper, since the net effect of decreased clearance will have been arrived at thereby. It is believed however that the hollow arcuate taper provides tension distribution characteristics which have benefits to be exemplified hereinafter.
In any event, the saw blade is disposed upon a roller R at a roller abutting surface 10b adapted to be placed in registry against an outer periphery of the roller R as shown in Figure 1 and 2. The topmost portion aye of the blade 10 is remote therefrom. When the roller is appropriately tensioned by outward displacement of the roller in the direction of the arrow F, the roller moves upward as shown in the drawing figure. More particularly, the zone of lessened thickness at the center 10c provides a saw blade having sufficient force distribution and flexibility which when unpensioned, the saw blade does not lie flat on the roller R but defines a substantially triangular void 10d (in section). However, when tensioned by moving the roller I, in the direction of the arrow F, the void is removed from the center the void lo is then superposed above the blade reflecting a zone of different forces dissipation compared to that which is experienced along the face of the saw blade where it contacts the rollers.
.
The steel between the cutting edges 11 is made progressively thinner to the center when man~ractured at the steel mill, and this can cause the edges to be made tighter on the wheel, and thus the inner surface lob of the saw is in contact with the roller and the outer surface lo is of "V"
shaped configuration when the saw blade contacts the roller.
Thus, the Sow blade is allowed to deform so that tension is applied adjacent the cutting teeth which causes the edge of the blade to in tension while the center of the blade lo is in compression. However the force vectors on the top surface lo are contained by the V contour to overcome prior art buckling tendencies.
That is to say when the roller is initially allowed to contact the saw blade, an air space lo exists between the engaging face of the roller and the bottom face lob of the saw blade. As the roller is expanded in the direction of the arrow F, the saw blade is properly tensioned when the saw blade deforms to such an extent that the air space lo approaches zero clearance or is in tangential physical proximity to the roller.
In prior art devices, a saw blade having constant thickness long its entire length initially contacts the roller along the entire length thereof and subsequent tightening of the roller by expansion in the direction of the arrow F causes the prior art blade to bow at the center by bending the edges downward so that ;
air space can then exists along the center point of both the Jo to 3 I
blade-and the roller. Clearly, having this space exist allows for the blade to flex. and distort not only along its edges when encountering material having varying thickness such as knots in the wood, but also assures a continuous flexing pattern along the area adjacent the roller at its center area, contributing significantly to heat build-up and the fatigue of the blade material. Additionally, the prior art saw blade is only supported at extremities of the roller in the prior art cases.
For crown bands, the bowing tendency is shifted from the center towards the edge of greater length.
Figure pa teaches the use of a second form of the invention in which a single edge is provided with cutting teeth 21, the edge remote therefrom devoid of a cutting surface. More particularly, the area of least thickness 20c of the blade shown in Figure pa is of fret from geometrical center so that it is closer to the edge 22 devoid of teeth to accommodate the gradual shortening of the overall width of the blade due to sharpening.
That is to say, as its material is removed form the blade cutting surface 21, the center 20c moves to the left as shown in to drawing Figure pa and therefor,migrates towards the geometrical center of the blade - Similar to the phenomena of Figure 2, the blade of Figure pa will exhibit the same type of forces when disposed upon the associated roller. More particularly, when contacting the inner face 20b of the blade an air gap is included only prior to tensioning by the roller. However, the saw may be of sufficient flexibility that it lays on the roller in tangential contact with the roller along its entire length when it first comes in contact, the area of tangency being from edge to edge on the roller. However, due to the disparate nature of the thickness of the blade, as the roller is tensioned, the air gap 20d eliminated and superimposed on the top blade curvature. By way of comparison with a flay rolled uniform thickness double cut band saw, when such a handsaw is initially contacted by the roller, the flexible nature of the blade causes the edges of the blade to sag down beyond the edges of the roller and a slight bow is provided at the center. As tightening begins, the edge where the roller contacts the saw blade is the area of greatest forces build-up, the free ends of the blade exhibiting compressive bowing forces extending towards the blade, i.e. the surface adjacent the roller experiencing forces toward the center of the blade. At the center of the blade a tendency to exhibit compression and bowing at the center is manifested since the free edges of the blade provide initial downward and inward bending moments. In the instant application, the tapered length allows the combination of the compressive stress and bending moment with far less built in compressive forces because the top surface loan aye dissipate and redirect the force vectors.
.
In the case of a saw blade with a bulletin crown, the effects are even more profound since the area of the blade adjacent the cutting edge has à lesser diameter and therefore the tendency of the blade along the center portion to buckle or bow is even greater.
axing thus described the preferred embodiment of the invention it should be understood that numerous structural modification and adaptations may be resorted to without departing from the spirit of the invention.
BACKGROUND OF THE INVENTION
The following relates generally to saw blade configurations and more particularly a construction of a band saw or a sash type gang saw.
The optimum design for a saw such as a band saw or a sash gang saw would be one which has minimal thickness for the band which supports the cutting teeth so that friction and associated heat caused by the band rubbing against the material to be cut is held to a minimum. It is well known that the generation of friction and its associated heat if excessive can ruin the temper of the cutting portion which thereby accelerates the dulling of the cutting edge and the associated life of the band.
The treatment of cutting implements in general so as to temper same and provide requisite flexibility without an associated loss of sharpness at the cutting edge has been an art, the methods for which have been handed down from generation to generation as trade secrets. While band saws have been in existence for perhaps a century as we know them today, with few modifications to the basic structure having occurred during that interval, the supporting machinery associated with the band saw has improved remarkably within the last decade or so particularly with respect to automatic feeding of the work stock and the manipulation of the work stock so as to effect a plurality of cuts as is desired to provide a finished product With this associated automation, and for that matter with manual feeding, worst case scenarios are generally relied upon in determining feed rates and the like so that dulling of the cutting blade by excessive heat and friction with an associated loss in band saw Do sharpness can be avoided or manmade.
In known band saw manufacture design, one of the most important criteria in use is the proper tensioning of the band so that there is minimum flex along the leading cutting edge of the handsaw. To this end, handsaw fabrication techniques (and for that matter, sash gang saws) require that the linear length of the leading edge or cutting portion of the handsaw be of lesser magnitude than the edge remote therefrom so that the non cutting or trailing edge has a substantially convex contour, commonly referred to as a crown. In this manner, when the handsaw is appropriately tensioned between the rollers which support and drive the band saw, the leading cutting edge is the area that receives the initial tension and is therefore most taut. The leading edge most closely approximates a straight line when properly tensioned in an ideal case and to attain this driving blade flexor, one support roller is operatively connected to weights so gravity keeps the blade taut but displaced in the presence of wood consistency variation, such as snots.
A further ideal in addition having the leading or cutting edge define a straight line is to have the band itself be of a thickness approaching zero for two reasons. Firstly there would be an associated reduction of the steel used in fabricating the saw which provides with it a concomitant advantage in weight reduction. Obviously, the lighter the handsaw the greater the speed associated with the handsaw in its operation and a minimal amount of surface area is provided exposed adjacent the wood for heat build-up. Secondly, a handsaw which approximates zero thickness will result in less wood removal required in cutting (in the form of sawdust) which can provide a substantial increase in the amount of usable board feet from every cut and can translate into substantial savings in a large volume sawmill.
i Saving loath ox an inch on every cut would translate to a savings of $800,000 to' a company the magnitude of Weyerhauser or Georgia Pacific on an annual basis. By way of perspective, the blade according to the instant application saves eight or nine thousandths of an inch on every cut.
Timber conservation is a critical concern today since virgin forests in the United States are vanishing. The price of finished or sawn lumber has increased by 1.7% each year since 1900 while the cost of live trees while standing has increased 3.5~ each year. Moreover with vanishing virgin forests, the diameter of harvested trees is substantially less than it was even thirty years ago which manifests itself in a long felt but heretofore unsatisfied need in scaling up the efficiency in wood processing resulting in the instant invention.
A rule of thumb in the lumber industry is that a reduced loss of ~010 inches per saw cut equals a savings of fifty cents to one dollar per thousand board feet of lumber produced. The amount of wood saved by its not being reduced to sawdust by merely reducing the size of the kern by merely .031 inches would result in an increase in lumber yield of from one to three per cent with no associated increase in log costs. In many large mills, this would equate to an additional profit of about $280,000 annually.
Thus, thinness of the saw blade can have a profound impact on the profitability of a sawmill and the instant invention provides a substantive decrease in the amount of metal used in forming the saw blade and therefore a concomitant decrease in the amount of wood wasted as sawdust.
The following patents reflect the state of the art of which applicant is aware in so far as these patents appear to be germane to the patent process:
345,565 ~imonds jug. 3, 1886 1,736,444 Mullen Dec. 30, 1930 4,160;39~ ~ertini Jul. 10,- 979 The very old patent to Simonds teaches the use of a handsaw which, at the time the Simonds invention was made, referenced to a narrow saw (column 1 line I which was used to cut a curve within a minimum distance and therefore more closely corresponds to a coping saw both of which was hand manipulated and wound really not pertain to handsaws as they are used in sawmills. Any similarities therefore between Almonds and the instant application would appear to- be merely coincidental.
Similarly, the patent to Mullen teaches the use of a process for treating mill handsaws in which grinding is a known technique for removing high spots in the manufacture of the saw blade, and Figure 1 shows an exaggerated section of the saw wherein the central strip appears thinner than the two edges.
More particularly, ~uehlen shows in Figure 1 an exaggerated section ox a band saw, the central strip appearing thinner and longer than the edges which take the pull of the saw in use. There is not intended in his patent to be a measurable difference in the thickness and the illustration is an effort to show the effect of his process which is really not a manufacturing process but is a process of maintenance, subsequent to the manufacturing process, to be done on the sawmill premises.
the nexus of the Mullen patent is to remove internal stresses of the metal fibers which are unequal in magnitude one relative to the other so that they will all be under the same tensioning by reverse bending and stretching (page 2 lines ~-13). Firstly, it is problematical whether or not the steel at the time of the invention of Mullen required this type of stress relieving, and secondly, it is respectfully stipulated that the stress relieving treatment dictated by Mullen, using today's soft steel, would cause the very distortion which would approximate long use to characteristics or chronic abuse (page l lines 9-13, page 2 lines l-3). It is a specific object of the instant invention to reduce the amount of stretching, pulling, bending, etc. to retain as much of the natural elasticity of the steel so as to extend the useful life and flexibility of the saw in its intended work environment.
The patent to Burton appears to diverge even further from the subject matter of the instant application in that the end of the handsaw thereof does not have parallel edges and nothing to indicate that there is a variation in thickness thrilling.
The instant application is distinguished over the known prior art in that it provides either hollow formed blades or taper formed blades so as to eliminate either partially or totally the crown and thus the concomitant tension gradient of currently available band and sash gang saw blades. By having the dimension of the handsaw or sash gang saw be reconfigured as to be defined hereinafter, the appropriate tensioning of the band is programmed into the band itself when disposed upon band rollers, and virtually none of the elasticity of the steel by roller tensioning is lost and thereby the life of the steel would be extended due to the diminishment of peruse flexor. By having the major body portion of the saw band formed with a hollow taper, a concomitant decrease in the amount of clearance between adjacent teeth points can be manifested so that substantially less material will be removed in the cutting process Less cutting pressure would follow as a consequence, as would faster feed rates. The geometry of the saw according to the instant application when disposed upon the band support rollers would exhibit an improved geometrical strength by its preformed nature to thereby resist buckling resulting in greater cut accuracy.
When the accuracy improves, the yield from the raw material to improves considerably. Also, when less clearance is needed, a narrower chip is removed from the cut so that the sawdust holding gullets of the teeth can be utilized to better advantage by removing the same amount of chip size but converting from a wider chip to a longer chip for an increased rate of feed than that which is now possible. The gullets would thus be able to carry out more of the sawdust without spilling it from the sides of the saw while in the cut, thus further reducing friction and heat which has the most profound impact on saw life longevity. Since sawdust is removed along the cut, less power is required to move along at the same cut rate, and the teeth associated with the instant application tend to deflect less since the cut is narrower than the prior art. the differences in magnitude delineated hereinabove are incorporated herein again for purposes of contrast.
OBJECTS AND 5t)MMl~RY OF' EYE INVEN~lON
, - accordingly, this invention has an objective the provision of a new and novel band or sash gang type saw exhibiting characteristics of greater economies of scale and improved life along with faster feed rate.
A further object of this invention contemplates providing a device as characterized above which when installed in its cutting environment is so configured that the tension is formed as a gradient having the greatest amount of tension on the cutting edge of the blade which therefore defines a linear cutting edge.
A further Deject of this invention contemplates providing a device as characterized above which has substantially or partially eliminated the need for pre-tensioning and providing a crown and replacing same with a contour of the cutting blade which naturally causes the blade to assume its most beneficial profile when installed on a Andes cutting machine. In this manner, needless fatigue imposed by pre-tensioning has been minimized and difficulties in manufacturing processes acquitted with forming a crown will have been obviated. When suitably supported on pressure rollers to fix the blade in its cutting environment, the natural pattern of stresses are exhibited in the improved saw according to the instant application.
A further object of this invention contemplates providing a device as characterized above which is of minimal thickness thereby saving on metal associated with the blade and provides a kern of minimal width allowing a concomitant saving in material removed in the sawing process.
A further object of this invention contemplates providing a device as characterized above wherein the offset of adjacent teeth are substantially less than the prior art and the associated pullets work more efficiently in reducing heat, friction and removal of wood chips.
.
A further object of this invention contemplates providing a device as characterized above to extend the "flex life" (reduction of fatigue failure) of the steel associated with the saw without removing as much or any of the elasticity of the steel when roll tensioning.
A further object of this invention contemplates providing a device as characterized above to reduce the amount of saw distortion during its actual cutting use whereby higher speeds and lower friction and therefore extended life are possible.
- In one form of the invention, a saw having cutting teeth on opposed extremities when taken in section includes a central area of minimal thickness and a gradual increase in thickness from the center to the sectional extremities whereby the only area of the saw coming in contact with the medium-to be cut is actually the teeth. In addition, when suitably tensioned, the saw exhibits a natural tendency for the working edge to exhibit zones of greatest tautness in a natural manner so that minimal stressing of the blade is required to achieve attachment of the band to its machine, thereby reducing the amount of built in stress. By having the cutting teeth be the area of the saw blade which is expanded first, tension at that area is followed by a normal compression at an area most likely to receive the compression i.e., the center of the blade which can accommodate I
01 this additional compression not only by its diminished I dimension, but also by its contouring so that stress build up is 03 minimized and the lines of stress associated with the blade are 04 balanced, reducing the likelihood of bulging, buckling or 05 warping when given the opportunity due to excessive heat build 06 up -for example.
08 In another form of the invention, a blade having 09 a single cutting edge on one extremity when taken in section has a complementary edge formed and dimensioned to have If substantially the same thickness as the cutting edge immediately 12 inward from the offset tooth portion, and the taper is 13 geometrically offset relative to a central line so that 14 successive sharpening causes the central diminished area of the blade to migrate slowly toward the cutting edge of the saw.
16 Thus, the central concavity in the saw is caused to move as a 17 function of time as the saw is sharpened and allows for 18 migration of the thinnest portion of the blade from a side 19 opposite the center line adjacent the non-cutting edge to ultimately a side adjacent the cutting edge.
22 In general, the present invention is provided for 23 use in an industrial band mill, wherein a driven band saw is 24 mounted on a plurality wheels, each of which is substantially flat and has a front edge, and at least one of which may 26 constitute a driving wheel. The band saw has inner and outer 27 sides and further has a pair of edges, at least one of which has 28 cutting teeth formed thereon, wherein the edge with the cutting 29 teeth overhangs the respective front edges of the wheels, and wherein apparatus is provided for moving the wheels in a 31 direction substantially away from one another. The invention is 32 an improvement wherein the band saw is substantially free of _ g Jo 01 preceptors in its manufacture prior to use, the band saw being 02 concavely formed on a-t least its inner side and substantially 03 from edge to edge thereof wherein -the band saw has a 04 cross-sectional thickness which is substantially non-uniform 05 throughout and which decreases substantially uniformly edge to 06 edge towards -the approximate center of the band saw, such that 07 there is a reduced mass at the center of the band saw between 08 the edges thereof. A non-uniform radial gap is provided between 09 the band saw and each of wheels when the band saw is first lo mounted on the wheels, and when the wheels are moved away from 11 one another, the band saw will be stretched and the inner 12 surface of the band saw will become substantially flush against 13 the respective wheels in the operative position of the band saw 14 on the band mill, thereby eliminating the necessity of stressing the band saw by roll tensioning or the like during -the 16 manufacture thereof; and whereby the reduction of mass replaces 17 the expansion otherwise required by roll tensioning.
- PA -I
BRIEF DESCRIPTION OF TIE DRAWINGS
Figure 1 is a top plan view of a saw formed in accordance with the instant invention. While a band saw is depicted, it should be apparent that a sash type gang saw could be included also.
Figure 2 is a sectional view taken along lines 2-2 of Figure 1.
Figure pa is an alternative embodiment utilizing only one edge of the band as its cutting edge, whereas Figure 2 uses both edges as a cutting edge.
Figure 3 is illustrative of the true prior art currently in use.
BRIEF DESCRIPTION OF THE PREFERRED Embodiment Referring to the drawings now, wherein like reference numerals refer to like parts throughout the various drawing figures, reference numeral 10 is directed to a band saw in accordance with the instant invention.
,.
As shown in Figure 2, the saw blade in section according to the instant invention includes at opposed edges thereof cutting teeth 11 equidistant from the geometrical center of the blade, the geometrical center 10c having a thickness substantially less than its thickness immediately adjacent the teeth, shown as 10d. The rate of change of curvature from the area of the blade at 11 to its center may define a linear taper or an arcuate taper, since the net effect of decreased clearance will have been arrived at thereby. It is believed however that the hollow arcuate taper provides tension distribution characteristics which have benefits to be exemplified hereinafter.
In any event, the saw blade is disposed upon a roller R at a roller abutting surface 10b adapted to be placed in registry against an outer periphery of the roller R as shown in Figure 1 and 2. The topmost portion aye of the blade 10 is remote therefrom. When the roller is appropriately tensioned by outward displacement of the roller in the direction of the arrow F, the roller moves upward as shown in the drawing figure. More particularly, the zone of lessened thickness at the center 10c provides a saw blade having sufficient force distribution and flexibility which when unpensioned, the saw blade does not lie flat on the roller R but defines a substantially triangular void 10d (in section). However, when tensioned by moving the roller I, in the direction of the arrow F, the void is removed from the center the void lo is then superposed above the blade reflecting a zone of different forces dissipation compared to that which is experienced along the face of the saw blade where it contacts the rollers.
.
The steel between the cutting edges 11 is made progressively thinner to the center when man~ractured at the steel mill, and this can cause the edges to be made tighter on the wheel, and thus the inner surface lob of the saw is in contact with the roller and the outer surface lo is of "V"
shaped configuration when the saw blade contacts the roller.
Thus, the Sow blade is allowed to deform so that tension is applied adjacent the cutting teeth which causes the edge of the blade to in tension while the center of the blade lo is in compression. However the force vectors on the top surface lo are contained by the V contour to overcome prior art buckling tendencies.
That is to say when the roller is initially allowed to contact the saw blade, an air space lo exists between the engaging face of the roller and the bottom face lob of the saw blade. As the roller is expanded in the direction of the arrow F, the saw blade is properly tensioned when the saw blade deforms to such an extent that the air space lo approaches zero clearance or is in tangential physical proximity to the roller.
In prior art devices, a saw blade having constant thickness long its entire length initially contacts the roller along the entire length thereof and subsequent tightening of the roller by expansion in the direction of the arrow F causes the prior art blade to bow at the center by bending the edges downward so that ;
air space can then exists along the center point of both the Jo to 3 I
blade-and the roller. Clearly, having this space exist allows for the blade to flex. and distort not only along its edges when encountering material having varying thickness such as knots in the wood, but also assures a continuous flexing pattern along the area adjacent the roller at its center area, contributing significantly to heat build-up and the fatigue of the blade material. Additionally, the prior art saw blade is only supported at extremities of the roller in the prior art cases.
For crown bands, the bowing tendency is shifted from the center towards the edge of greater length.
Figure pa teaches the use of a second form of the invention in which a single edge is provided with cutting teeth 21, the edge remote therefrom devoid of a cutting surface. More particularly, the area of least thickness 20c of the blade shown in Figure pa is of fret from geometrical center so that it is closer to the edge 22 devoid of teeth to accommodate the gradual shortening of the overall width of the blade due to sharpening.
That is to say, as its material is removed form the blade cutting surface 21, the center 20c moves to the left as shown in to drawing Figure pa and therefor,migrates towards the geometrical center of the blade - Similar to the phenomena of Figure 2, the blade of Figure pa will exhibit the same type of forces when disposed upon the associated roller. More particularly, when contacting the inner face 20b of the blade an air gap is included only prior to tensioning by the roller. However, the saw may be of sufficient flexibility that it lays on the roller in tangential contact with the roller along its entire length when it first comes in contact, the area of tangency being from edge to edge on the roller. However, due to the disparate nature of the thickness of the blade, as the roller is tensioned, the air gap 20d eliminated and superimposed on the top blade curvature. By way of comparison with a flay rolled uniform thickness double cut band saw, when such a handsaw is initially contacted by the roller, the flexible nature of the blade causes the edges of the blade to sag down beyond the edges of the roller and a slight bow is provided at the center. As tightening begins, the edge where the roller contacts the saw blade is the area of greatest forces build-up, the free ends of the blade exhibiting compressive bowing forces extending towards the blade, i.e. the surface adjacent the roller experiencing forces toward the center of the blade. At the center of the blade a tendency to exhibit compression and bowing at the center is manifested since the free edges of the blade provide initial downward and inward bending moments. In the instant application, the tapered length allows the combination of the compressive stress and bending moment with far less built in compressive forces because the top surface loan aye dissipate and redirect the force vectors.
.
In the case of a saw blade with a bulletin crown, the effects are even more profound since the area of the blade adjacent the cutting edge has à lesser diameter and therefore the tendency of the blade along the center portion to buckle or bow is even greater.
axing thus described the preferred embodiment of the invention it should be understood that numerous structural modification and adaptations may be resorted to without departing from the spirit of the invention.
Claims (6)
1. In an industrial band mill, wherein a driven band saw is mounted on a plurality of wheels, each of which is substantially flat and has a front edge, and at least one of which may consititute a driving wheel, wherein the band saw has inner and outer sides and further has a pair of edges, at least one of which has cutting teeth formed thereon, wherein the edge with the cutting teeth overhangs the respective front edges of the wheels, and wherein means are provided for moving the wheels in a direction substantially away from one another, the improvement wherein the band saw is substantially free of pre-stress in its manufacture prior to use, the band saw being concavely formed on at least its inner side and substantially from edge to edge thereof, wherein the band saw has a cross-sectional thickness which is substantially non-uniform throughout and which decreases substantially uniformly from edge to edge towards the approximate center of the band saw, such that there is reduced mass at the center of the band saw between the edges thereof, wherein a non uniform radial gap exists between the band saw and each of the wheels when the band saw is first mounted on the wheels, and wherein when the wheels are moved away from one another, the band saw will be stretched and the inner surface of the band saw will become substantially flush against the respective wheels in the operative position of the band saw on the band mill, thereby eliminating the necessity for stressing the band saw by roll tensioning or the like during the manufacture thereof; and whereby the reduction of mass replaces the expansion otherwise required by roll tensioning.
2. The improvement of claim 1, wherein the band saw is concavely formed on both sides and from edge to edge thereof.
3. The improvement of claim 1, wherein each of the wheels has an annular surface which is substantially flat when viewed in side elevation, wherein each of the wheels has a front edge and a rear edge, wherein each of the edges of the band saw has cutting teeth formed thereon, and wherein the edges of the band saw overhang the front and rear edges of the wheels, respectively.
4. The improvement of claim 1, wherein the cutting teeth are swaged set.
5. In an industrial band mill, wherein a driven band saw is mounted on a pair of wheels, each of which is substantially flat and has a front edge, and one of which constitutes a driving wheel, wherein the band saw has inner and outer sides and further has a pair of edges, at least one of which has cutting teeth formed thereon, and wherein means are provided for moving the wheels apart to strain up the band saw, the improvement wherein said one edge of the band saw having cutting teeth thereon being adapted to overhang the respective front edges of the wheels, wherein the band saw is substantially free of pre-stress in its manufacture prior to use, the band saw being concavely formed on both sides thereof and substantially from edge to edge thereof, the band saw further having a cross-sectional thickness which substantially is non-uniform throughout and which decreases substantially uniformly from edge to edge towards the approximate center of the band saw, such that there is reduced mass at the center of the band saw between the edges thereof, whereby a non-uniform radial gap exists between the band saw and each of the wheels when the band saw is first mounted on the wheels; wherein when the wheels are moved away from one another, the band saw will be stretched and the inner surface of the band saw will become substantially flush against the respective wheels, thereby eliminating the necessity for stressing the band saw by roll tensioning or the like during the manufacture thereof; whereby the reduction of mass replaces the expansion otherwise required by roll tensioning, and wherein the cutting teeth of the band saw are swaged set.
6. The improvement of claim 1, wherein only one edge of the band saw has cutting teeth formed thereon, and wherein the thinnest part of the band saw is offset from its geometric center.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US53529683A | 1983-09-23 | 1983-09-23 | |
| US535,296 | 1983-09-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1226788A true CA1226788A (en) | 1987-09-15 |
Family
ID=24133600
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000453981A Expired CA1226788A (en) | 1983-09-23 | 1984-05-10 | Saw blade construction |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0156815A1 (en) |
| CA (1) | CA1226788A (en) |
| WO (1) | WO1985001239A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE513996C2 (en) * | 1997-10-17 | 2000-12-11 | Kapman Ab | pruning |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE611898C (en) * | 1935-04-08 | Karl Thoelen | Unshaped metal saw blade for long and band saws with conically reinforced squabble edges | |
| US2734533A (en) * | 1956-02-14 | roberts | ||
| US341989A (en) * | 1886-05-18 | Elias c | ||
| US378203A (en) * | 1888-02-21 | Louis lohmaf | ||
| US2795255A (en) * | 1954-05-03 | 1957-06-11 | Hansen John | Bread-slicing blade of endless band type |
| FR1126700A (en) * | 1955-06-23 | 1956-11-28 | Advanced band saw blades |
-
1984
- 1984-05-10 CA CA000453981A patent/CA1226788A/en not_active Expired
- 1984-07-09 WO PCT/US1984/001075 patent/WO1985001239A1/en unknown
- 1984-07-09 EP EP19840902966 patent/EP0156815A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| WO1985001239A1 (en) | 1985-03-28 |
| EP0156815A1 (en) | 1985-10-09 |
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