US1920652A - Method of heating, hardening, and tempering of hollow steel propeller blades - Google Patents

Description

Aug. 1, 1933. J. H. Mmes` METHOD OF HEATING',l HARDENING', AND TEMPERING OF HOLLOW STEEL=PROPELLER BLADES Filed April `5. 1932 aux L L L' wwzamj '@Anoxym ,Y

Patented Aug. 1, 1933 I I1,920,652.` 'METHOD or HEATING, HARDEN'ING,

Ann

"TEMPERING A 0F -HoLLow STEEL" Pno- PELLER BLADES .Y

f James H. McKee, Pittsburgh, Pa-assignor to Pittsburgh Screw and Bolt Corporation, a Cor f y A A,porationfof Pennsylvania y l Application April 5,1932.y Serial 1710.116032 59' v n *4 enum.;l (ci. lss-zn IThis invention relates to aeronautical pro-v pellers, and more particularly-to improvements;Y in the' method of hardening l and tempering de. V

' jig 14,may be of any lsuitable construction I pretachable hollow steel propeller blades.r

`One f object of this invention ris to provide a method for producing straight propeller blades Vhaving the desired hardness and temper.

Another Aobject of this invention is'to provide. a`

novel method for' tempering and hardening hol- 0 low steel propeller blades whereby practical y straight blades can be produced.v 'v I a methdfor hardening and tempering propeller blades in which the blades are so held during the quenching and coolingl operations thatwarping` thereof is prevented.

These and other objects which Will'be made ap parent to those skilled in this particular-art are accomplished by means off" this invention, the steps of vwhichy are described i'ntheffollowing specification and illustratedin theaccompanying drawing, wherein:

Figure 1 is-a view. in vertical section of a heat-l ing furnace illustrating therst step in myl pIOCeSS;

Fig. 2 is a view in end elevation` illustrating thelheld. during apparatus in which, the blade is quenching and air cooling;` Y. 1

rig. a is a view msildeleievaun or nie made holding apparatus; f f i. I

Fig. 4 is avviewin vertical, sectionfof adraw' heating furnace; 'f

Fig. 5 is an enlarged partial view section .of

the'blade holding apparatus;

elevation of the Fig.A 6 is -an enlarged view in side base of the blade holding apparatus;V

Fig. '7 is a sectional view taken on llneVIlI-VII of Fig. 6;

Fig. 8 is a sectional view talreiizon line VIIIofFlg.6; y Fig. 9 is a sectional view on' linek of Fig. d; and l y Fig. 10 is a sectional view take'lron'line 1p1-,X

ofFig.6.

In carrying out my porting the blades during these operations. After the ring 1l has been secured tothe blade. 10, ltjis suspended from a spider 12 and lowered into a vertical heating furnace 13 of any suitable type 5 such as an electric furnace, where it is heated or raised to a temperature or about 1650 to 17oo F.

temperature it is removedfiom thefurnace 13 and placed in a-straightening jig 14. vWhile the l15er `to use a Jig such as isdescribed in my co- -pending application Serial No. v603,258, filed 'April 5, 1932, which comprises a base member 14a lhaving a perforated portionvshaped to conform ln contour to one face of a propeller blade and j onwhich the heated blade is placed. The blade J .is held on the member 14a `by a series of yokes A further object of `this invention is to provide 14b extending transversely of the plate 14a and which are adapted to be moved into engagement with the edges of theblade to securely clamp it against Vthe member14a. The `yokes 14h are movedinto and out of engagement with .the edges ofthe blade-by air `motors 14c mounted on a frame 14d supporting the;base member 14a. The air motors are connected to the yokes 14bby pis- 'ton rods 14e. The.- air motors are supplied with air from a suitable sourcevof supply through -pipes 14f. After'the bladehas-been heated it is -in .the air jig 141it is hardened` by submerging in a vtank 15 containing oil or other suitable quenchingliquid.v r f In order that the air jig A.14 may be readily lowered into the tank 15,1when the blade has been *clamped thereinythe Jig-14 is'supported on a bar 16 whichis joumaled in trunnions 17 slidably l mounted on uprights 18A `which extend down- `wardlyintothe uid inthe tank 15. As shown in Figure 3, the-air :jig .14,is so mounted on the vbar 1,6v that lthe portion thereof adapted to receive the shank of the bladeis over the tank 15and the center of mass of the jig is substantially over thebarl. 'l I' p In order to prevent thevweightof the Jig 14 from moving thebar downwardly on the uprights 18, the b ar 16`ls'also lpl'voted in the endsof strap members 19 depending from a counterbalanced Acrossbar'ZO; The cross bar 201s slidably mounted'ontheuprights18 and has cables. 21 attached thereto which pass over pulleysj22 `and 23 and are fastened to counterweights 24'.The*d of the yair-clamping jig l14, when'infblade receiving posi'- tion, is supported on af'suitable standard 25.

When the blade has been clamped ln the airclamping device 14 and it isdesired tolower the blade andjig into the oil or quenching liquid in the tank l5, the tip receiving end of the air jig is pushed upwardly bythe operator so that the bar -After the blade; lo hasbeen raised to hardening 33 where it is'heated blades without departing Asince the yokes of' .tain changes may 16 is turned in its trunnions 17. As the tip end of the air-jig is raised the center of mass of the jig shifts toward the uprights 18, overcomes the counterbalance weights 24 and the bar 16 carry-I ing the jig slides downwardly on the uprights 18 into the tank 15 until it comes to rest on a spring bumper 26 disposed in the bottom of the tank between the uprights 18.

Since the hollow blade is submerged in the tank with the shank end down, it is apparent that the oil or quenching liquid in the tank passes into the interior of the blade as Well as around the outer surface thereof and as a result all parts of the .blade are given substantially the same degree o! hardness.

After the blade has been a cable 27 passing around pulleys 28 and 29 and having one end thereof attached to a suitable winch (not shown) and the other end to the cross-head 20 -isv wound von the winchand pulls the air-jig -14 out of the tank 15. As the airclamping device-moves upwardly between the upe rights 1S, the end of the jig 14 engages curved slides 30 mounted adjacent to the uprights 18 and the tip end of the air-clamping device is forced away from the uprights which shifts the center of mass and causes the jig to fall on the support 25. Y

The blade 10 is jig 14 and is suspended a suitable spider 32 in then removed from the airthrough the ring 11 from a vertical draw furnace to a temperature of b etween 900 and 1200 .for approximately 3 to 4 hours. After the blade has beenthoroughly soaked in the -draw furnace 33 it is removed therefrom and placed in another clamping jig similar in all respects to the one in which it was held during the Vquenching operation where it is allowed to cool slowly in the air to give it the proper temper'. u

By holding the blade in such a clamping device during the quenching and air cooling operation, it is readily apparent that I am able to prevent the tip end of the blade from curlling and the body of the blade from warping blade by al continuing pressure they follow up the contraction or shrinvage of the blade, and as a result I am .able to produce practically straight hardened* and tempered propeller blades having the proper curvature for any transverse section thereof.

While I have described one embodimentof my invention, it is readily apparent that cerbe made in the steps of my method for hardening and tempering propeller from the spirit of my thoroughly quenched,

three hours, -and the .jig are held against the invention or the scope of the appended claims.

-transverse sections of the blade during the yquenching operation, reheating the blade between a temperature of 900 to 1200 F., and then cooling the blade slowly while applying pressure to succeeding-transverse sections thereof.

' y2. The method of hardening and tempering hollow steel propeller blades, which consists in heating ajblade to a hardening temperature of at least 1650, dipping said heated blade shank lend first in an oil bath to harden both the inner and outer surfaces thereof, holding the edgesof the blade under continuous.r pressure during the quench `to prevent warping, soaking the blade for about three hours at a temperature of at least 900, cooling the reheated blade in air to temper the same, and applying continuouspressure to the edgesoi.' the blade while it is cooling to follow up contraction and shrink- `age therein and prevent warping of the blade.

heating ,a blade to approximately 1650", dipping said heated blade shank end first in a quenching liquid, applying pressure to the solid edges of succeeding transverse sections of the blade while in the quench, raising the quenched blade to a temperature between 900 'and 1200, holding the blade at suchv temperature for at least cooling the blade .in air while succeeding transverse sections thereof are Vsub-l jected to pressure-to prevent warping of the blade.

4. The method of hardening and tempering :hollow steel propeller blades which consists in heating a blade to approximately 1650, dipping said heated blade shankA end first in a quenching liquid, applying continuous pressure to the solid edges of succeeding transverse sections of the blade while in the quench, raising the quenched blade to a temperature between 900 and 1200*?, holding the blade-at such temperature for at least three hours cooling the blade in air, and continuously applyingl pressure to the solid edges of said blade as-it is being cooled to follow up the shrinkage therein and prevent the blade from warping out of shape.` f

cAMEs H. MCKEE.

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