US2542940A - Spring manufacture - Google Patents

Description

Feb. 20, 1951 w. F. PIOCH ET AL SPRING MANUFACTURE Filed July 19, 1946 Patented Feb. 20, 1951 Michz, a2 corp 'ration of Delaware; i M Application 1946,-S eri@l 10. 684332 8 Gl'a'imsr- This invention relates to the formihg'endheattreatment of "leaf springs ofthegeneraltype used in the constructibn of. automobiles; and, moreparticularl'v, to a'method and" device thereforinwhich high-frequency electrically induced cur= 5 rent is. used as the 'heatingmea'ns; aridi thefdrm ingwandheat treatmentis effected inla continu ousprocessr t I V Heretbfore thenfbrmingt of leaf" SpriIIgSTtOWh'e presc'ribedl curvature" and their heat trea'tment haebeen antexpensive and difficult manufactur ing operation. The character of the "steer used H and. the thickness .of 'the st'ock required the use" of considerable force in form ingl the" leaves, to the desiredtaceuracy aridit"was difiibult. to provide subsequent "heantreatment without deviation from? the J curvature so estah= lished. It has, therefbre; bfeen) the'fpracticetb" form these sprih'g5 'ihiti'a11y and" restrain" them in heavyi'ipresses while undergoing quenchifig to 20 obtain the desired;metallurgical": characteristics; thus: preventingjwarpage or change the"estt;b'='- lished curvature. Thiyrequired equipmeht'o'f" considerable."complex'ity and i't'L"Wa.'ST 'ditfficult to establieh arflexib'le manufcturihg routihewr'one which. might beixcarried'out at minimumof? time with elemehts as' they- WGYE'L-Of'sfith size; and weight. iMbreover'; thes'prihg Was 'sub ject ilto surfacerdeteriorationi *durih'g thef'hetntirig' and; quenching: steps: because "offthe necessary" sfowhes's, of "the process and it was" extremel'yfdif' ficult to. obtaih the desiredmetaillur'gicai char e tristics and atithe. same" time maintain thepre frred' spring "form; A further 'e'ontributing dif ficulty 'Wasthat" the springs we're'fofteri' not or" unifbrmicunvaturev or ofunifdrm .thickness'fsince the ends are.frequentlyfeathered or departed in othr1ways from a true circular curve. The Object of this ihvention is"'t'0 devise a, method fer ;'the'" formihg, and-*heattreatinent 40 of Iea'f' springs in "which the operation may be conducted automatically and ma continuous step? A further object; of the ihvention" is" to devise i a leafesprihg'fbrming' andheat treatihg;apparatusr and method"orop'eratiom thereof emplbyifig" rs"*45 the heat sourcee; high-frequencyalternatihgi electrical current. Still another object of this" inventionuie'to devise an integrated method ldy means of" which the spring stoclc'may progress automatically. and ate; uniform rate through 8P5!) heating, bending; reheating? and"quenchihgop=- erati'on forming-thecompleted sprin'gwitha mini mum of surface" deterioration and with themaintenance of'the; prescribed degree offlfihensionaJ accuracy. Still another-objector thisfin 55 through the feathered portion 22.

As the stock 23 emerges from the initial coil, it is engaged by the initial bending mechanism l which constitutes a driven roller 25 and a fulcrum roller 26 which is mounted on the fixed axis 21. An arm 28 is also pivoted on the fixed axis 21 and carries a pilot roller 29 normally urged into contact withthe driven roller 25 by a spring 30 secured to the housing l0. A limit switch 32 is associated with an extension 33 of the arm 28 and is so arranged as to be responsive to the thickness of stock passing between the driven roller 25 and the pilot roller 29. The upper fixed axis 34 supports the L-shaped upper arm 35 which carries the bending roller 36 and a cam follower 31 mounted on the long leg of the L. The follower 31 engages the primary cam 39 rotatable on the axis 40 and carrying a secondary cam 42 which is associated with the secondary follower 43 cooperating with the secondary limit switch. 44. The purpose ofthis apparatus is to permit control of the bending imparted to the spring with due regard to variation in thickness, because of the feathered ends 22 referred to above. It will be apparent that by change of the relative position of the fulcrum roller 26 and the bending roller 35 in conjunction with the driving roller 25, the degree of curvature imparted to the stock traveling between the rollers may be varied. Otherwise, when the thickness of stock varies, as-it does here'at the feathered ends, the curvature would change accordingly, if the rollers were fixed and it is the purpose of this apparatus to make due allowance with regard to such changes of stock thickness and also to provide different degrees of curvature at diiferent points in the spring should this be desired.

As shown in the drawing, the cooperating rollers are arranged to impart a desired uniform curvature to the midpart or constant thickness extent of the spring leaf, and the cam follower 31 is on the minimum circular extent 38 of the primary: cam 33. It will be apparent that as the primary cam 39 rotates past 90?" from the position shown in the drawing, the effective radius of the cam 39 increases in the linear sections 4!, and the cam follower 31 will be moved, displaced in a counterclockwise direction with reference'to the axis 34, while the bending roller 36 will be' projected in the same direction increasing the relative curvature of the curved line determined U by the working faces of the rollers 25, 26, and 36, and tending to increase the relative curvature of stock operated upon by these rollers, thus allowing for the relative variation in stock thickness The maximum circular extent 45 of the cam'39 corresponds to the alignment of the bending rollers when no ing on the cam outline. The effective sequence of rotation of the primary cam 39 is governed by the secondary cam 42 and its follower 43 and the secondary limit switch 44 which may be adjusted to compensate for the various lengths of springs or feathered ends to be handled and the degree of corrective or excess curvature required. The cam 39, as shown, is somewhat exaggerated for the purpose of this showing, but the actual design to obtain the desired bending roller displacement and length of dwell between blanks or during operation on uniform sections is a simple matter of mechanical design.

Thus, as the stock initially enters the bending mechanism, its forward speed is so synchronized that when its forward end reaches the bending roller 36, the position of that roller is such as to accommodate minimum thickness of the stock,

, length of the feather 22 and progressively changstock is passing through them. The operation of the cam 39 is governed bythe limit switch 32 and as the initial edge of the stock enters between the driven roller 25 and the pilot roller 29 forcing themapart, the limit switch is activated and begins to revolve the cam 39 from the position 180 from that shown in which the cam follower 31 is on the maximum circular extent 45 to one in which one of the linear sections 4| of the cam 39 engages the follower 3? and progressively decreases the obliquity of the bending roll 36, as the feathered end 22 of the spring blank passes beneath it. The relative position of the working rolls'thus changes automatically to compensate for decreased thickness due to the feathered end,

' and thereby imparts a uniform curvature to the ing the position of the bearing roller 36 as the obliquity of the cam 39 decreases so that the follower 31 enters on the minimum circular extent 38 as the full thickness of the stock comes to the 1 roller 36. The same operation, butin reverse, is

effected when 'the rear feathered end is reached.

The secondary limit switch 44 co-operating with J the secondary cam effects themaintenance of the j proper time relationship required of the cam 39 commensurate with the length of thespring and featheredend the distance between successive pieces of stock, being interlocked appropriately with the primary limit switch 32.

The bent stock then passes through a secondary heating coil I6 adjusted to raise its temperature above the critical point of the' steel, as may be required to obtain the desired metallurgical'characteristics. It is then subjected toa final, bending:

step in the mechanism H which, in construction,

is substantially the same as that of the initial bending mechanism described above, to correct the spring shape after the secondary heating and to hold it in prescribed curvature as the quenching operation progresses. It will be' apparent that provision must be made here, as well, for the variation in stock thickness due to the feathered ends and the stock must be rigidly held when the.

quench is applied if'the desired curvature is to be'" obtained. The final bending mechanism ll will not be described in detail, nor is it so hown, since it is substantially the same as theinitial bending mechanism [5. It may suffice to say that it has as corresponding parts, the driven roller'4l, pilot roller 48, bending roller 49, arm 50, primary limit switch 52, L-shaped arm 53 and fulcrum roller 54. The cam follower 55 is shown above the asso-' ciated cam mechanism and secondary limit switch corresponding to that described in detail under the primary bending mechanism is omitted from this showing, although it will be under-' 1 stood that it is of substantially the same construction.

5,8: and 51; from which a number ofv individual: quenchtpipes 5.8 lead to. the proximity of: the; spring blank. and are a so; directed as to. providea uniform distribution, of the quenching fluid-i, The. headers: 56; and iii are supplied. withthe coolant. fluid from thepump 5.9 Whichwithdraws it'from:

thebath I-2 through, the separation chamber 6.0;.

cdil is'given apartial quench beiorfebeing bentto- A the finished curvature whichis often of consid erable value'ininsuring that the desired curvature is, in;fact, obtained.

. the stock leaves the secondary bending'manosedrollers fii, certain of whichsuch asdli are driven, and; the whole array is fiifred in. a; prescnbedrelative curvature s ,that the spring while passmg through them is, continuously restrained in the conformation desired. The quenchcoolant centinuously ejected on the stock during this stage so that it is cooled belowthe criticalpoint withthespeedliecess y to obtain thexdesired metallurgical characteristics; The relative c urva ture of the array may be by suitable adjustment of" the axes of the various rollers through any conventional means so that springs.

o'frvarious radii. may. be: treated; It willbe noted that no special provision is made here to allow for the variation of stock thickness accounted for by the feathered end, since these-dieing quite prime function of the rollers cr. is to prevent gross Warpage in the main body of the spring until the quench is completed. The springs are of course restrained by rollers Ed until cooled sufiiciently to preclude any substantial warpage. The rollers 64 are, preferably, somewhat narrower than the stock and appropriately staggered, transversely, to allow access of coolant to the spring.

As the stock leaves the quenching apparatus 18, it is projected through the delivery rollers 65, at least one of which is driven as at tit, and enters the bath l2 where it is directed so that it falls on the delivery conveyor having the receiving flight G6 and return flight fill. These are preferably inclined to the plane of the drawing and carry the cooled spring up and out of the bath for delivery. Further details of this construction are not deemed necessary for the purpose of this application, since the conveyor design is conventional.

It will thus be seen that provision is made for automatic heating, bending, quenching and holding during the quench period as well as such further cooling as may be required to obtain a spring leaf of precise dimension and the metallurgical characteristics required. This is all done automatically and with a minimum of attention or care. Proper allowance is made for variations in thickness of the stock and it is possible to provide for different curvatures by suitable arrangement of these bending control means. The advantage of such an arrangement is believed to be manifest.

We realize that certain changes may be made in the apparatus and method of operation thereof as described above and it is the intention to cover in the following claims such of these changes as are reasonably within the scope thereof.

, thinare speedily cooled and stabilized and the 6. Theainventionclaimedis: I ,1. Inlaniapparatus forv forming and-,heat-treats inga steelspringgleafi. a linear. arraygcomprising...

a high frequency electrical heating coil, a bendr.

ing means, a. restraining; means, a. quenching means to direct. coolant past, said restrainingr means andito thespring leaf; and meanstotrauel;

said spring.leaf1longitudinallytiimugh Saidarray: 2.. In an apparatusforsthe forming and; heat:

treating a. steel. spring: leaf, .alinear: array, coma prising. a. high frequency... electrical heating coil):

a bending means,. a. secondaryhighp. frequency;

electrical, heating.-.coil,. secondary; end

means, a restraining: means; arquenching; means:

to direct: coolant pastsaid restraining means; and;

to the spring'leaf andimeansto .trave1;said spring; leaf longitudinally through. saidarray at a; Sub?" stantially:uniformspeedl, 3; In: an. apparatus: for ptheiforming, and-heats treating a steel spring. leaf a .linearxarran. com-r prising, a high-frequency electricalheatingcoil, a -bending means,,.airestrainingmeansg. aqufi ing means, means to. direct coolant past said; re straining .means and. to the: springrleaf means, to; travel said spring. leaflongitudinally through said army at: a substantially uniform; speed; and": meansito vary the degree of curvaturelimparted: to said leaf by said bendingmeans in relatiornto;

the-thickness of saidileaf;

4: In an. apparatus: for the continuous forming; and 'heat-treating of a SteeIJspringgleaf; alinea-r" array; comprising; ahhi'ghsfrequency electrical, heating coil, a, bending -.means,. bending, means being automatically variable to impart a uniform circular curvature to said stock as it passes therebetween despite variations in the thickness of said stock, a secondary heating means effective to raise said stock as it travels therethrough above the critical temperature of said steel, an initial quenching means effecting said heated stock, a secondary bending means effective to bend said stock to said prescribed curvature at the said initial quench, a restraining means comprising a series of oppositely arranged rollers having their axes fixed to establish said prescribed circular curvature and progressively engaging said stock as it emerges from said second bending mechanism, quenching means to direct coolant past said restraining means to said stock as it passes therethrough, and means to travel said spring leaf longitudinally through said array at a substantially uniform speed.

5. In an apparatus for forming and heat-treating a steel spring leaf, a linear array, comprising, a high-frequency electrical heating coil, a bending means comprising alternate rollers mounted on opposite sides of said leaf and axially displaced to impart circular curvature to the leaf passing therebetween, a restraining means andto the spring leaf, a quenching means to direct coolant to said restraining means, and means to travel said spring leaf longitudinally through said array at substantially uniform speed.

6. In an apparatus for forming and heat-treating a steel spring leaf, a linear array, comprising, a high-frequency electrical heating coil, a bending means comprising alternate rollers on opposite sides of said leaf axially displaced to impart circular curvature to said leaf as it passes therebetween, means to vary automatically said axial alignment of said rollers with respect to the thickness of said leaf to impart a substantially uniform circular curvature thereto, a restraining means, a quenching means to direct coolant to through said'array at a substantially uniform speed. a

7. In an apparatus for forming and heat-treat-I ing a steel spring leaf, a linear array, comprising, a high-frequency electrical heating coil, a bending means comprising alternate rollers on opposite sides of said leaf axially. so arranged as. to impart a circular curvature to the leaf passing therethrough a secondary heating means, a secondary bending means, a series of opposed rollers adapted to engage said leaf as it emerges from said second bending means and having their respective axes arranged in a predetermined circuular curvature, quenching means directing coolant past said restraining means and to the spring leaf to quench said leaf as it passes therethrough, and means to travel said spring leaf longitudinally through said array at a substan-j tially uniform speed.

8. In an apparatus for forming and heat-treating a steel spring leaf, a linear array, comprising, a high-frequency electrical heating coil, a bending means engaging said spring as it emerges from said coil, a secondary heating means engaging said leaf asit emerges from said bending means and adapted to heat said leaf above the critical temperature, an initial quenching means partially quenching said leaf as it emerges from said secondary heating means a secondary bending means engaging said leaf as it emerges from said initial quench and bending it to finished curvature, a series of op ositely arranged rollers" having their respective axes following said cir-.

cular curvature and adapted to engage said leaf therebetween as it emerges from said secondary bending means, a final quenching means to direct coolant past said restraining means and. to the spring leaf while said leaf is passing therethrough, and means to travel said spring leaf continuously through said array.

' i WILLIAM F. PIOCH.

GEORGE PASCOE.

, REFERENCES CITED 7 The following references are of record intlie file of this patent:

UNITED STATES PATENTS Number Name Date 7 67,788 Mills Aug. 13, 1867 134,264 Ferson Dec. 24, 1872' 357,228 Pocock Feb. 8, 1887' 390,206 Cofiin Oct. 2, 1888 661,459 Stifel et a1 Nov. 6, 1900 1,061,721 Beaumont et a1. May 13, 1913 1,362,708 Lang Dec. 21, 1920 1,381,014 DOrville June '7, 1921 1,489,894 Monteith et al Apr. 8, 1924 1,500,571 Brandenburg July 8, 1924 2,445,150 Mueller Dec. 21, 1948 FOREIGN PATENTS Number Country Date 258,633 Great Britain Sept. 21, 1926

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