US2361068A - Archery bow - Google Patents

Description

Oct. 24, 1944. E. soLLlD ARCHERY BOW Filed April 8, 1945 Flg ER ll( SoLLxD INVENToR.

Patented Oct. 24, 1944 UNITED STATESy PATENT OFFICE f ARCHERY Bow i Erik Sollid, Denver, Colo. Application April s, 194s, serial No. 482,348

7 Claims.

This invention relates to improvements in archery bows.

Bows for archery are, as a rule, constructed almost entirely from some tough, straight grained wood, such as yew or hickory, and are carefully shaped. The backs of the bows are formed from the white wood which is the toughest, While the convex orbelly sides are formed from the heart Wood which is the least exible, but the most resilient. The bows are nearly always formed with a handgrip which is quite rigid, and from which the limbs extend in opposite directions forming cantilever beams. The backs become quite convex when the` bows are bent in shooting and tend to fail due to the breaking of the fibers and eventually splitting. And this is true even when the greatest care is taken to have the surface of the back exactly follow the grain.

It is evident that if bows could be so constructed' that the wood would all be under compressive strain whiley the tensional strains would rbe resisted by a metal member secured to the back there would be little tendency for the fibers to break or split.

It is also well understood that the lighter the limbs are, other things being equal, the better the bows, heavy limbs have a corresponding amount of inertia and momentum, both of which are objectionable.

It is an object of this invention to produce a bow that will have a greatly increased driving power per unit weight.

Another object is to produce a bow of such construction that the greater portionv of the wood will be under compression when the bow is bent.

A further object is to produce a backing that can be applied to bows either during the manufacture or any time thereafter, and which can also be used in connection with other articles of manufacture.

I am aware that patents have been granted for bows having backs provided with some tough material, such as animal skin, sinew, bark, and silk fibers, which, no doubt, wereimportant advances. All of the materials mentioned are quite extensible and their moduli of elasticity are quite small and as a result they are not very eiective in moving the neutral axis towards the backs of the limbs;

If the backing material has a large modulus of elasticity compared to the wood `to which itis attached, it causes the neutral axis to move toward the rear of the limbs and increases the areas under com-pression. If the backing were formed from material having a modulus of innity, then all of the wood would be under compressive strains.

This invention, broadly expressed, consists in a bow having a backing of steel whose modulus of elastictiy is about 30,000,000 pounds per square inch compared to about 1,500,000 pounds per square inch for yew or hickory, or some alloy having a similarly high modulus. With a backing having such a high modulus of elasticity compared to the wood, the latter is put almost entirely under compression. In any event the neu? tral axis moves so close to the back that the tensional strains in the wooden portion of the bow become negligible.

A still further object of the invention is to produce a metallic tension or compression bow backing member having its surface treated or processed in such a way that it will form a close bond with a suitable adhesive such as glue or other cement suitable for the purpose.

'The above and any other object or objects that imay appear as this description proceeds are attained by means of a construction and an arrangement of parts that will now be described in detail and for this purpose reference will be had to the accompanying drawing in which theinvention has been illustrated, and in which:

Figure 1 is a side elevation of a bow constructed in accordance with this invention;

Figure 2 is a front plan view of the bow;

Figure 3 is a section taken on line 3--3 Figures 1 and 2;

Figure 4 is a `view, partly in sections showing a metal backing in place on the bow, and illustrates a modified form of the invention;

Figure 5 is another cross section showing a fur ther modification;

Figure 6 shows a short length of a bow in reary surface plan view, parts being broken away to better disclose the construction;

Figure '7 is a view similar to that shown in Figure 6 and shows a modification;

Figure 8 is a section taken on linev 8--8 Figure 7 similar to that shown in Figure 3, and shows the bow provided with a backing like that shown `in Figures "I and 9;

Figure 9 is a section through the backing'assembly shown in Figure 7, and shows the parts to. a somewhat enlarged scale;

Figure 10 is a part section through the backing assembly, taken on line lU-I l) Figure 6;

Figure 11 is a side elevation of a bow limb con?A in a manner similar to that shown in` structed Figure 5:

Figure 12 is a section taken on line I2-I2 Figure 11, and

Figure 13 is a stress-diagram.

In the drawing reference numeral I 5 designates the bow proper, which may be made of yew, hickory or any other suitable wood or of some plastic material, and I6 designates the backing which will be described hereinafter in detail. The hand grip has been designated by numeral I1 and the string by I8. The ends are provided with I9 for forming an suitable notches or shouldersv attachment with the bow string.

means or by etching with a suitablechemical.Y

The reason for roughening the surface is -to ef,-

fect a better bond between the backing and the wood of the bow. If an adhesive is found that makes a satisfactory bond with the smooth metal surface the roughening may be omitted. In addi-v tionzto .having its Vsurface roughenedithe vmetal strip Ina-vv be provided Vwith severalzholes 2|, Which may rbelled` withV the adhesive, o-r `fiber plugsfmay be ,inserted in theholes. :The ber having 'the .propertyjiof for-ming a Vstrong bond withthe adhesive. The holes may -haveinclined Walls A,if desired. Instead of steel some` other suitable metal havingthenecessary modulus: of elasticity may-:be employed; An'y'ofthe alloy steels :are fsuitable, and'such other alloys es berryllium'-eopper. i y f' Mlfhen :the bow. isbent the backing `issubjected to ,a high .degree ,of tension, .and vthere naturally results a shear stress between lthe wood and the metal that must `be resisted by the adhesive. Since -the metalbacking has such a highmodulus of elastici-ty it iis evident that it is not'intended to stretch to anyappreciable extent, but to -resist tensional orcestending to stretch it, wherefore the Woodportion |15 will 'be compressed. Reference will Yherein,after be'rmade to Fig. 13, Where the 'stressessvilLbe explained more fully.

Although theebacking shown in Fig. 4 `is 4the simplest-,lit is rather-.diiiicult to obtain the-nocessari-ly-lstrong andreliable bondand for this reason it is desirable vto enclose the metal strip in an envelope, or zover-ing',V comprising Amaterial Y .that

. :a strong bond with; the adhesive.

In Fig. 7, a sectionihas :been shown, 'to v an enlarged `Sfalef'll :Whichzazmetal strip'Z- is-laid on a strip 22 of thin ber, strong paper, Wovenfabric, Weed veneer erpIastic. Strip :2.2 is wider than the metalstrip and "the .flatter is covered with a layer 23, of similar material vto fstrip v22. The three pieces being securedftofeach other by glue or some other adliesiW-i.`

It -will beobserved that since the layers 2 2and 23 are Awidertliartcthe fmetal strip and the latter is :positioned .centrally-thereof lthe edges are in contact `with eachv other thus forming an envelope.

-When a vbacking like that illustrated in Figs.

'7, 8 and 9 is glued .to Ithe .back of a bow, .a .good

bond :will be ,had because bothsuriaces are `well adapted to coact fwith y'glue `or ,other adhesive. When .a back liketthat 'llSt described is glued .to the back oia 'bow the shear stresses will be resisted by the adhesive on both sides of the metal strip 2li and also-bythe adhesive between thebow and strip 22. With this construction, failure due n to the separation of .thepartsisavoided Itis ,well known .that .cold ,drawn wiresuch as piano wire .has ,a .greater tensileY strength. per unit area thanrolledmeta-l and besides this itis somewhatgnore exibie.. `A layer of wiremay be y substituted for.stripllqintheembodiment shown infiss.. I,..8,a,nd9.. i

Faures. ,5. 6 and .1.0 fabaking employing la levensfase-Wires Alias been illustrated. in .the

drawing the wires, `have been shown .of considelf: The parts being subjected to pressure of sufficient intensity to cause the iibrous material to conform to the shape of the wires as shown most -olearlygin Fig. l0.` It is contemplated to employ for the layers 25 and 26 thin strips of wood cut .parallel with the fibers. Thesestrips are steamed orsoitened by urea or other means, and subjected to 'pressure during the gluing operations whereupon :the wood Will shape. itself Ito conformto the surface of the wires. It will be observed that the wiresV are spaced sucientlyto allow the `wood snriaces-to ,come into contactalong lines 21'.

Whenfa-.backing likethat shown in Figs. 6 and ll'Ogis used, good bonds are assured as glue cooperatesvery well'with wood. The'suriaces ofthe wires may be roughenedy asabove explained.

InA some instancesit may be desirable to provide the bow limbs l5 with holes .28 and to'provide the inner surfacewith a backing strip for resist.- ing compression. Suchv a construction is indi` cated -where a cheap soft wood is employed -or where 1the -loow is made of aplastic material like thatindicated by 15a in ',Fig. il.

In i3 the stress line '29 shows that when the be dy.l5is subjected to bending forces P,re sisted by an opposing lforce W the ,tension will Abe resisted almost entirelyby the backing-strip and the entire `bcdygol the wood portion will be subjected to compression. The neutral axis N will be positioned .either between the bow and the backing vorso `close to the back of the `wood t5, that the tensional stresses in the wood are negligible.`

*Insteadqoff using only a single layer of wires thezbacking may have two lor'rnore layers as shown at .liiin Fig:- 12. This will cause the neutral axis to move further towards the back than if oni-viene strip is used.

Wheneverthe word glue is employed it Yis used in its broad sense as an adhesive and isi-ntended fto ycover all suitable adhesives.

The wordfplastic is used in its present sense as referring to fa- -synthetic product such as synthetic urea formaldehyde andv any other suitable .plasticsnow available or to -be hereafter discovered.y v a When a construction like that shown in Figs. 5 and l1 is employed the body may be oi rany suitable material and wood yhaving cross grains kand knot. holes can be used. Steel is believed to .be highly suitable for this purpose and has there,- fore been .psed .as an example and the modulus .of elasticity has .been given for comparison. ,Any metal. bai/ine .aliishermodulus .of elasticity than thepody ,embodies` tlieinvention .but-fthe best results are obtained whenthe metal lis similar .to

steel. ,in thisrespet. f

what claim covering of brous material for the tension member, adhesively secured thereto and to the body.

2. An archery bow having a wood body and a continuous steel tension member extending the entire length thereof, said tension member comprising a steel element embedded in andadhesively secured to a covering of brous material, the tension member extending substantially the entire length of the bow and adhesively secured to the back thereof throughout; its entire length.

3. An archery bow having a wood body and a continuous metal tension member extending substantially the entire length of the bow and adhesively secured thereto throughout its entire length, the metal having a modulus of elasticity of approximately twenty times that of the wood, and a covering of brous material for the tension member, adhesively secured thereto and to the bow.

entire length thereof, adhesively secured to the' back of the body along its entire length, and a covering of shear transmitting material adhesively secured thereto and tothe body.

ERIK SOLLID.

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