SAW BLADE CONSTRUCTION

Abstract: An improved saw particularly of the bandsaw (10) or sash gangsaw variety having at least one cutting edge (11, 21) and a central portion (10c, 20c) of minimal thickness, the decrease in thickness from a cutting edge (11, 21) or a remote edge (22) to its center either being linear or arcuate.

Description: Saw blade convtnuction ύao<gM>und of ike invention Ike fo-llowing, /leΛ i ό genenaXly io ΔUW blade. confLgwiationά and paflitcuJaj y a coπάituction o a band ΔOW OΛ. a Δa t ty e- gan ΔOW . Ike optimum design fon. a ΔOJW uck a* a. band ΔOUW O/L a Δaudx. gang. ΔOLW uouid be one ukijck hat minimal ikichned4 fon. ike band klck Δupponid ike cuiiing ieeik ΔO ikai fzLciion and aΔΔodaied keai cause by. ike band /tubbing, against ike maienia. ' L io be cui IΔ keid io a minimum . Oi Λ weLL known ikai ike generation of fni iion and it c όΔOciaied keai if ex eΔόis e can iin ike tempen of ike cutting poniion uklck tkeΛeby ac elen ieΔ ike due ing of ike cutting, edqe and ike OΔΔOciaied I e treatment of cuiiing i ptementό in genen J- ΔO OΔ to te pen. m and provide. nexfμiΔiie flexibility wiikoui an OΔΔO dated -IOAA of Λ aΛp eΛβά at ike cuiiing edge ha been an ani , ike mei odό fo i uklck have been handed down from generation io generation OΔ trade ■aecA&bi . kirle band aw have been in existence fo i perhaps a. century OΔ we know tkem today , wiik few modifications io ike bamic. Δinuctune having occuΛΛed during, kai inier at , ike -iupponiing, σzckinery CLόΔOciaied wiik ike band ΔOJW h s impnoved remarkably, ωiikin ike -last decade on. 40 pa tiJJZulajiAy wiik reaped io automatic feeding, of ike uonk yάiock and ike manipulation of ike uo/ik stock 40 as io effect a plurality of cwtό a iΔ desired io provide, a finisked p/ioduci . irJiik ikis CLόΔOciaied automation , and for ikai matier wiik manual, feeding , worst case scenarios are. generally relied upon in determining, feed nates and ike -like ΔO ikai dulling, of ike cuiiing bia.de. by c iv keai and fniciion wiik an asΔOciaied loss in band saw sk ψneΔΔ can be avoided on. minimised . On knoun band saw manufacture design , one of ike oΔt important c/ ie iia in use Ls ike proper tenόioning of ike band Δ ikai ike ie is minimum flex. along ike -leading cuiiing, edge of ike bandόaw . To ikLi end , bandόaw fab J ritior echnijciμeΛ (and for ikai matter , sask gang Δaum ) require ikai ike linear lengik of ike leading, edjge 0/1 cutting, portion of ike bandaaw be of -lesser magnitude than ike edge. njemoie ikerefnom ΔO thai ike noncuiiing, or trailing, edge has a substantially convex contour , commonly referred io as a crown . On ikis manner , uken ike bandsaw is appropriately, iensioned between ike rollers ukick support and drive ike band saw , ike leading, cuiiing edge. Is ike area thai receives ike initial tension and LΛ ikerefore m Δt iaui . Ike leading edge, most closely approximates a sinaigki line uken properly iensioned in an ideal case and io attain this driving, blade flexure. , one Δuppori roller. is openaiively connected io weights so gravity keeps ike blade iaui but displaced in ike presence of wood consistenc variation , Δuck OΔ knots . A furtker ideal in addition having, ike leading, or cuiiing edge de.fine a Δtnaighi line is io have ike band itself be of a ikickness approacking. geno for two reasons . Firstly , there would be an associated reduction of ike Δieel used in fabricating, ike saw ukick provides wiik it a concomitant advantage in weight reduction . Obviously , ike lighter ike bandsaw ike greater ike speed asΔOciated wiik tke bandsaw in its operation and a minimal amount of surface area id pnovided exposed adiacent ike wood for keai build-up . Secondly , a bandsaw ukick approximates g πo ikickness will result in less wood removal reauired in cutting, (in tke fonm of Δawdusi ) ukick can provide a ΔubΔi ntiat increase in ike amount x>f usable, board feet from every cut and can translate into ΔubΔianiiai savings in large, volume sau ili. . Saving 2 1000 ik of an inck on every cut would translate to a savings of $800,000 io a company ike magnitude, of ϊJejyerkaeuse L or Qeorgia Pacific on an annual basis . By way of perspective , ike blade according, io ike instant application- saves eight or nine thousandths of an inch on every cut . limber conservation is a c/dLtLcaJ- concern today Δince virgin forests in ike United States are. vanisking, . Ike price of finisked or sain lumber has increased by /. % eack year since IJOO ukile ike cost of live ire&s ukile standing, has increased 5 5 % ∞-ck year . flbreover. , wiik vanisking, virgin foreΔts the diameter of harveΔied trees is Δubsi niially lesΔ than it was even thirty years ago ukick manifests itself in a long felt but kereio ore unsatisfied need in sc ing, up ike efficiency in wood processing, resulting, in ike instant invention . A rale of thumb in ike lumber industry is thai a reduced loss of , 0/0 inckes per saw cut equals a Δuvings of fifty cents io one dollar per thousand board fe.pt of lumber produced . Ike amount of wood saved by its not being reduced io sawdust by merely reducing ike si^e of ike kerf by merely . OJI inckeΔ would result in an increase in lumber yield of from one io three per. cent wiik no associated increase in log, costs . On many lamge mills , ikis would eψaie io an additional pnofii of about ~2βQ,000 annually . Thus tkinness of tke saw blade can .have a pno found impact on tke pnofiiability of a saumili and tke instant invention pnavideΔ a substantive decrease in ike amount of metal used in fonming ike saw blade, and ikerefor a concomiiani decrease in ike amount of wood wasted as Δawdust . I he following, patents reflect ike state of tke art of ukick applicant is aware, in so far as ikese patents appear, io be gjenmane io ike patent process >' 5 > 5>5 Simonds August J , 1886 l, 7&>, Wi i'ke/Uen Dec . Jp , 19 O 4, lt>0, J/7 Beriini J 'υ l . 10 , 1979 I he very old patent io Simonds teaches ike use of a bandsaw ukick , at the time tke Siπvnds invention UOΔ made , referenced io a narrow ΔOW ( column I line I ) ukick was used io cut a curve within a minimum distance and ikerefor more closely corresponds io a coping, saw boik of ukick was hand manipulated and uould really not pertain io bandsauis as ikey are used in sau ilis . /iny similarities ikerefor between Simonds and ike instant application would appear to be merely coincidental . Similarly , ike patent io i .eklen teackes ike use of a pnocess for treating, mill bandsauis in ukick grinding is a known technique for removing high spots in ike manufacture of tke saw blade , and Figure. I shows an exaggerated section of ike saw ukerein ike central strip appears thinner ikon tke two edgjes . I'bre particularly , t ueklen how in Figure I an exaggerated section of band saw , ike central strip appearing, thinner and longer ikon tke dgjes ukick take tke pull of ike saw in use . Ikere is not intended in his patent io be a measurable difference in ike ikickness and tke iilasiraiion is an effort to show ike effect of kis pnocess ukick is really not a manufacturing, process but is a pnocess of *«D OrøGINAi _ oι maintenance , subsequent io tke manufacturing pnocess , io be done on tke saumili premises . I e nexus of ike ι> eklen patent is to remove internal stresses of ike metal fibers ukick are unequal in magnitude, one relative io ike oilier so thai ikey will aXl be under ike s me tensioning, by reverse bending, and Δireicking, (page. 2 lines 4-/J • /-irsily , it is problematical ukeiker or not ike sie&l at ike time, of ike invention of I' len required this type of stress relieving, , and secondly , it is respectfully stipulated ikai ike stress relieving, treatment dictated by ru ' eklen , using, today's soft steel , would cause ike very distortion ukick would approximate long, use characteristics or chronic abuse (page I lines -1 J } , poge 2 lines l-J J. 0t is ike Δpecific object of the instant invention io reduce ike amount of stretching , pulling, , bending, , etc . to retain as muck of ike naiunal elasticity of ike steel so as io extend ike useful, life and flexibility of ike saw in its intended wonk environment . The patent io Beriini appears io diverge even furiker from ike subject matter of ike instant application in ikai ike bandsaw thereof does not have parallel- exlges and. nothing, to indicate ikai there is a variation in tkickness therealong, . Ike instant application is distinguished over tke known prior art in that it pnovide either hollow formed blades or taper formed blades so as io eliminate either partially or totally ike croun and £τus the concomiiani tension gnadieni of currently available band and sask gang, saw blades • By having, the dimension of the banxisaw or Δask gang be pre-configured as io be defined hereinafter , ike appropriate tensioning. of ike band is pnogramned into ike band itself uken disposed upon ike band nøllens , and virtually none of ike elasticity of the steel by roller tensioning, is lost and thereby the life of the Δleel would be extended due io the diminishment of preuse flexure . By having ike major body portion of the saw band formed with a hallow taper > a concomiiani decrease in ike amount of clearance between adjacent ieeik points can be manifested ΔO ikai substantially less material will, be removed in ike cuiiing. pnocess . Less cutting, pnessure would follow as a consequence , as would faster feed rates . the geometry of the ΔOW according, io the instant application uken disposed upo ike band support rollers would exkibit an impnoved geometrical strength ' by its SUD-'L.: " : , . _. ' _ -_ _._ϊ!≥£T ,' O prefonmed nature io thereby resist buckling resulting, in greater cut accuracy . iken ike accuracy impnoves , ike yield from tke raw material impnoves considerably . Also , uken less clearance is needed , a narrower, ckip is removed from ike cut ΔO ikai ike sawdust holding gullets of tke teeik can be utilised io better advantage by removing, ike Δome amount of ckip si%e but converting from a wider ckip io a longer ckip for an increased rate of feed than ikai ukick is now possible . Ike gu lets would thus be able io carry out more of the sawdust without spilling it from ike sides of ike saw ukile in ike cut , thus further reducing, friction and heat ukick has ike most profound impact on saw life longevity . Since sawdust is removed along the cut , less power is required io move alon at ike same cut rate , and tke teeth associated with tke instant application tend io defied less since the cut is narrower than the prior art . I he differences in magnitude delineated kereinabove are inconponaied hereinagain for purposes of contrast . _ - * -•_•- / O ■«»-■_ «— --~: V . - -v . . -- -— ■ tyy, S 0bj.ecis and summary of ike invention Accordingly , this invention has an objective ike provision of a new and novel band or Δask gang type saw exkibiting, 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 ckanac eri^ed above ukick uken installed in its cutting, environment is so configured that the tension is firmed as a gradient having, ike greatest amount of tension on ike cutting, edge of the blade ukick ikerefor defines a linear cutting, edg . A further object of this invention contemplates providing, a device as chajiacieniged above ukick has substantially or partially eliminated the need fi pre-iensioning, and providing, a croun and replacing, Δanve wiik a contour of ike cutting, blade ukick naturally causes the blade io assume its oΔt beneficial pnofile uken insialied on a bandsaw cutting, ackine . On this manner , needless fatigue imposed by pre-iensionin has been minimised and difficulties in manufacturing, processes associated with firming a croun will have been obviated . i ien suitably supported on pressure rollers io fix ike blade in its cutting, environment , ike natural pattern of stresses are exkibited in ike improved saw according, io ike instant application . A further, object of this invention contemplates pnoviding, a device as characterised above ukick is of minimal thickness tkereby saving, on metal associated wiik the blade and provides a kerf ofjninimal widtk allowin a concomiiani Δaving, in material removed in ike Δawing. process . A furtker object of this invention contemplates providing, a device as characterised above ukerein ike offset of adjacent teeik are ΔubΔianii My less ikon ike prior ant and the associated g lieis uonk more efficiently in reducing, keai f friction and removal of wood ckips . A funiher object of this invention contemplates providing, a device characterised above io extend the "flex life ft (reduction of fatigue failure ) of ike steel associated with ike saw without removing as muck or any of the elasticity of ike steel uken roll, tensioning. . •f ""** ' -1- A furtker object of ikis invention contemplates providing, a device as ar t sed above to reduce the amount of saw distortion during ixs actual cuiiing use uhereby higher speeds and lower, fniciion and therefor extended life are possible . On one fonm of ike invention , a ΔOW having, cutting teeik on opposed extremities uken taken in section includes a central area of minimal thickness and a gnadual increase in thickness from the center io tke sectional extremities uhereby tke only area of tke saw co ing, in contact wiik ike medium io be cut is actually ike teeth . On addition , υhen suitably tensioned , ike saw exhibits a natural tendency for ike working edge io exkibii go es of greatest iauiness in a natural manner so thai minimal stressing, of. the blade is required io ackieve aiiackmeni of the blade to its machine , tkereby reducing i e amount of built in stress . By having the cutting, teeth be the area of ike saw blade ukick is expanded first , tension at that area is pillowed by a nonmal * compression at an area most likely to receive the conyiression i . e . , tke center of ike blade ukick can accomodaie this additional compression not only by its diminished dimension, but also by its contouring so thai stress buildup is minimised and the lines of stress associated with tke blade are balanced , reducing ike likelihood of bulging , buckling, or u rping ukengiven ike opportunity due to excessive keatbuild up for example . On another, fonm of ike invention , a blade having a single cuttin edge on one extremity uken taken in. section kas a complementary edge fonjne and dimensioned io have substantially ike same thickness as ike cutting edge inuediaiely inward from the o fset iootk poniion , and tke taper is geonveinically offset relative io a central line so that successive sharpening, causes the central duninisked area of tke blade to nignaie slowly toward the cuiiing edge of ike saw . I has ilie ceninal concaviiy in tke saw is caused io move as a function of time as ike saw is sharpened and allow for mignaiion of ike ikinnest poniion of tke blade from a side opposite ike center line adjacent tke non-cutting edge to ultimately a side adjacent tke cutting edge . Ihese and other objects will be made manifest uken considering tke following detailed specification uken taken in conjunction uiik tke appended drawing figures . RAO. ORIGINAL ( Q MPi IΛ. VYlfU Brief description of the drawings higure I is a top plan view o a ΔOW fon ed in accondance with ike instant invention . ikite a band saw is depicted , it should be apparent that a Δash gang, saw could be included also . higure 2 is a sectional view taken along, lines 2-2 of higure I . Figure 2a is an alternative embodiment utilising, only one edge of the band as its cutting, edge , uhereas higure 2 uses both edges as a cuiiing, edge . higure is itlusinative of ike true prior art currently, in use . Bnief description of .tke preferred embodiment deferring io tke drawings now , wherein like reference numerals refer io like parts throughout tke various drawing, figures , reference numeral IO is directed io a band saw in accordance wiik ike insiani invention . ,4s skoun in Figure 2 , the saw blade in section according io tke insiani invention includes at opposed edges iheieof cutting teeik II equidistant from the geometrical center of the blade , the geometrical ceniei 10 c having a tiτickness subsiantially less than its thickness immediaiedy adjacent the teeik , Δhoun as IO d . I he rate of change of curvature from the area of tke blade at 11 io its center may define a linear taper or an arcuate taper , since the net effect of decreased clearance will have been arrived at thereby . Ot is believed however thai ike hollow arcuate taper provides tension distribution characteristics ukick have benefits io be exemplified kereinafier . On any event , ike saw blade is disposed upon a roller. R at a no Hen abating surface 10 b adapted io be placed in registry against an outer periphery of ike rolle R as shown in higure I and 2 . I he topmost portion 10a of ike blade 10 is remote t/ierefrom . ike roller, is appropriately iensioned by outward displacement of ike roller, in tke direction of ike arrow F , ike noller moves upward as s oun in tke drawing figure . I'bne particularly , tke gone of lessened tkickness at ike center 10c pnovides a saw blade having, sufficient force distribution and flexibility ukick uken uniensioned , tke blade does not lie flat on tke noller R but defines a subsiantially triangular void lOe ( in section), however , uken iensioned by moving tke noller in the direction of i e arrow h , ike void is removed from ike center. , tke void lOe is then superposed above the blade reflecting, a £> . of different forces dissipation compared io ikai ukick is experienced along ike face of ike s w blade ukere it contacts ike rollers . I he steel between the cutting edges 11 is made pnogressiveXy thinner, to ike center uken manufactured at ike steel mill , and ikis can cause ike edg.es to be made tighter on ike ukeel , and thus the inner surface 10b of tke ΔOW is in contact wiik the roller a d the outer. su%face 10a is of "V" Δ aped configuration uken ike saw blade contacts O V IP SUBSTITUTE SHEET ike roller . I has , ike ΔOJW blade is allowed io defonm ΔO ikai tension is applied adjacent the cuttin teeik ukick causes the edge of ike blade io be in tension ukile ike center, of ike blade 10c is in compression . However the force vectors on the top surface 10a are contained by the V contour io overcome prior art buckling, tendencies • Thai is to say , uken the roller is initially allowed io contact the saw blade , an air. space lOe exists between ike engaging, face of the roller and tke bottom face 10b of tke saw blade . ,\s the roller is expanded in ike direction of the arrow h , ike saw blade is pnopenly iensioned uken ike saw blade deforms io Δuck an extent thai ike air. space lOe approaches ζeno clearance or is in tangential- physical proximity io tke roller . On prior art devices , a saw blade having, constant thickness along, its entire length initially contacts ike roller, along, the entire length ikereof and ΔubΔequeni tightening, of the roller, by expansion in ike direjction of the arrow F causes ike prior ant blade io bow at the center by bending, ike edges Sunward so i ! ιai air space can tken exists along, ike center point of boik ike blade and ike roller . Qleanly, having, this Δpace exist allows for the blade io flex and distort not only along, its edges uken encountering, material, having, varying i'liehness Δuch as knots in ike wood , but also assures a continuous pattern along, ike area adjacent tie noller at its center area _• contributing, significantly io heat build-up and the fatigue of ike bladematerial . Additionally , the prior art saw blade is only Δupporied at extremities of ike roller in ike prior art cases . For crown bands , tke bowing, tendency is skif ed from ike cente towards the zdge of greater length . Figure 2a teackes the use of a second firm of the invention in ukick a single edge is pnovided with cutting, teeth 21 , ike edge remote ikere iom devoid of a cutting, surface . t'ϋre particularly , ike area of least thickness 2Dc of the blade Δhoun in Figure 2a is offset from geometrical center ΔO thai it is closer io the edge 22 devoid of teeth io accommodate the gradual shorteniny of ike overall width of the blade due to Δharpening, . I hat is io Δay , as its material is removed from the blade, cutting surface 21 , ike center 2Dc moves io ike left as skoun in ike drawing Figure 2a. and ikerefor migrates towards the geometrical cenien. of tke blade . Similar io ike phenomena o Figure 2 , tke blade o Figure 2a <*"»* will exkibii ike same type of forces uken disposed upon ike associated roller . ibne particularly , uken contacting, ike inner face 20b of tke blade an air gap is included only prior io tensioning by the noller . However , ike saw may be of Δufficieni flexibility that it lays on the roller in tangential contact wiik ike roller along its entire length uken it first comes in contact , tke area of tangency being from edge io edge on the noller . lowever , due io ike disparate nature o th ikichness of the blade , as tke roller, is iensioned , ike air gap 2De eliminated and superimposed on tke top blade curvature . By way of comparison wiik a flat nolled uniform thickness double cut band saw , uken such a bandsaw is initially contacted by ike n ller. , tke flexible nature of the blade causes ike edges of tke blade io sag Sun beyond ike edges of the noller and a slight bow is pnovided at ike center . s Hy'iiening begins , ike edge uhere tke noller contacts ike saw blade, is tke area of greatest forces build-up , tke fr.ee ends of tke blade exkibiiing compressive bowing forces extendin towards tie blade , i . e . ike surface adjacent the nolle ad j acent the noller experiencing, forces toward ike center of tke blade . .it the center, of ike blade a tendency to exkibii compression and bowing, at the center is manifested since the free edges of ike blade pnovide initial Sunward and inward bending moments . On the instant application , ike tapered lengik allows ike combination of ike compressive stress and bending moment with far less built in coηoressive fonces because ike top surface 10a , 20a dissi,xι,te and redirect the force vectors . On the case of a saw blad wiik a built-in crown , tke effects are even more pn found since ike area of tke blade adjacent tke cutting edψe has a lesser diameter, and ikerefor ike tendency of tke blade along, tke center poniion to buckle or bow is even greater . . laving, thus described the preferred embodiment of the invention , it should be understood thai nunvero s structural modifications and adaptations may be resorted to without departing from ike spirit O j . tke invention . OΛΠ OWGtNAl SUBST i t ■r UTb * s> HEET

Claims: ikai is claimed is : 1 . An improvement is saws , particularly band and Δask gang saws comprising, in combination : at least one cutting, edge formed on a strip of elongate material , and a j p of decreased thickness extending, from the one said cutting, edge io a center of a blad . 2 . (he device of claim I ukerein a rate of change of ike ihickness is arcuate . 3 . I he device of claim I ukerein the rate of change is linear. . . Ike device of claim 2 including a Δecond cuiiing edge remote from the first cutting, edge . 5 • I he device of claim J including a second cutting, edge remote from ike first cutting edge . 6 . The device of claim 2 ukerein ike thinnest area of tke blade is o fset from the geometrical center . 7 • Tke device of claim ukerein the ikinnesi area of tke blade is offset from the center .

Inventors: WILSON HARRY, WILSON, HARRY
Applicants: WILSON HARRY, WILSON, HARRY
Application year: 1984
Main classification: B26D1
IPC codes: B23D61