US2437317A

US2437317A - Spot milling tubular blank for propeller blades

Info

Publication number: US2437317A
Application number: US581657A
Authority: US
Inventors: Dwillard J Davis
Original assignee: Avco Manufacturing Corp
Current assignee: Avco Manufacturing Corp
Priority date: 1945-03-08
Filing date: 1945-03-08
Publication date: 1948-03-09
Anticipated expiration: 1965-03-09

Description

D. J. DAVIS March 9, 1948.

SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES Filed March 8, 1945 15 Sheets-Sheet l Ouu IN V EN TOR. 0Qd0 f- March 9, 1948.

D. J. DAVIS SPOT MILLING TUBULAR BLANK FOR PROPELL'ER BLADES Filed March a, 1945 15 Sheets-Sheet z Ill March 9, 1948.

D. J. DAVIS SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES Filed March 8, 1945 15 Sheets-Sheet 5 LADES March 9, 1948. D. J. DAVIS SPOT MILLING TUBULAR BLANK FOR PROPELLER Filed March 8, 1945 15 Sheets-Sheet 4 T'lc 1K e |JJ l I l INVENTOR. d (flaw/L 7 1 J far/M 5 D. J. DAVIS SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES Filed March 8, 1945 15 Sheets-Sheet 5 6 z b 2 1 R f 0 T .m w o m w d a 7 o 5 l4 2 V a 1 W M 2 4 0 Z Z N H z o. 1 5 .I 1 m M w 1 1 w ,7 9 2 2 AMI MW. 2 9 o w 4 o 0 MA.- 9 4 m1 1 Q .5121 w m w 2 1 M m o M o L a k 1. 8 5 wv. 8 5 B o ..H/,..// Q 5 v M L? 0 l 4.. h w 1 s w w 1. M l1 1 i Aw 1|. 5 W M 5 a0 6 a 1 Q H 1 Km 1 Ila I w 5 E z w/fi F B M ,V FE. olo MIT nl lr In m o 4 w w 5 w e 1 z 1 v 5 n 1 m m w m w w m z 2 1 1 1 1 H 6 m D. J. DAVIS March 9, 1948. 2,437,317

SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES Filed March 8, 1945 15 Sheets-Sheet 6 INVENTOR. 0QCUCZ6/5d .OQaz/r/L 11:: 4g o-rrm March 9, .1948.

D. J. DAVIS SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES Filed March 8, 1945 l5 Sheets-Sheet 7 v. 9w a E x Q00 AWWnflH HawHHJUI'I. m |l|| mfiwuufimmmmmmnn l l w L klhlllillvlrvmf o3 a? mo.

INVENTOR lte y March 9, 1948. DAVls 2,437,317

7 SPOT MILLING TUBULAR BLANK FOR PRO PELLER BLADES Filed March a, 1945 15 Sheets-Sheet s Hq i6 IN VEN TOR.

. xQcuMa/m BY H 4 Me a March 9, 1948. 2,437,317

I SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES I D. J. DAVIS Filed March a, 1945 15 Sheets-Sheet 9 Fill INVENTOR. Qw-ig% Jaw/IV L/M Z 1&3 J7 for-7:1

March 9, 1948. L D. J. DAVIS SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES Filed March 8, 1945 15 Sheets-Sheet 10 I a so sisi JNVENTOR.

15 Sheets-Sheet 11 D. J. DAVIS Filed March 8, 1945 SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES- March 9, 1948.

INVENTOR. flaw/LL (@wazz March 9,4948. D. J. DAVIS SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES Filed March 8, 1945 15 Sheets-sheaf 12,

I HINVENTOR. wag/54 (QM/0L,

SPOT MILLING TUBULAR BLANK FOR PROPE ZLLER BLADES Filed March 8,1945 15 Sheets-Sheet l3 IN V EN TOR.

D. J. DAVIS March 9, 1948.

SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES Filed March 8, 1945 15 Sheets-Sheet 14 muu m5 ml 3. i mfi w 03 m 3.

IN V EN TOR.

March 9, 1948. v D. J. DAVIS 2,437,151 7 SPOT MILLING TUBULAR BLANK FOR PROPELLER BLADES Filed March 8', 1945 15 Sheets-Sheet 15 Hg 59' v I so I IN V EN TOR.

Q wZZ/gcd ($140M f L Zz s zo-rmy,

Patented Mar. 9,

SPOT

MILIlING TUBULAR BLANKFOR- PROPELLER BLADES Dwillard J. Davis, Detroit, Miclmassignor to Avco Manufacturing Cqn'poration, a corporation of Delaware Application March a, 1945, Serial No. 581,657

The invention relates to machines for use in providing hollow steel propeller'blades with the desired predetermined wall-thickness, which varies in different portions of the blade according to the stresses to which'they, are subjected in use.

' Heretofore, lers, the wall-thickness of partially fabricated tubular blanks which are to be used in the work ing portions of the blades, was measured at different spots or stations. The spots'were then marked to indicate any excess of wall thickness. lhe outer periphery of the blank was then abraded, usually by a belt sander,'to remove the excess metal. This abrading was done by approximation or guess from observationand frequently resulted in abra'ding too much metal from the blank and leaving insumcient wallthickness, which rendered the tubular blanksunusable or lacking in the requisite thickness for safe use, which necessitated; scrapping such blanks. In propeller; blades great accuracy in wall-thickness is a desideratum. 7

One important object of the invention is to provide a machine for use in fabricating propeller blades with great precision in wall-thickness and uniformity in production. This object is attained in fabricating hollow steel propel 19 Claims. (01. 90-,14)

- rotatable for millingspots in circumferential series and which includes means for locking the blank against rotation during'milling operations.

Another object of the invention is to provide a machine which includes means for indicating to the operator when the contact for engaging the inner periphery of the blank isiengagedfor cooperating with a stop-member for'the tool for controlling the depth of the cut so that theoperator will not operate the tool to make the cut' if there is interference between the inner memher and the blank.

Other objects of the invention will appear from the detailed description The invention consists in the several novel.

' features hereinafter described and more particuprimarily by milling or machiningwith great accuracy. spots of the tubular. blank, so asto leave the desired thicknesses at different points on the outer surface of the blank, and then abradlng the outer surface of the blank until'the spots or depressions are blended into the surface of the blank and eliminated. This makes itpossible to accurately determine whenthe abrading process should be discontinued to, leave the correct wall-thickness of the metal at the different points and avoids the production oi blades which must be scrapped on account of thin walls.

Another object of theinvention is to provide.

a machine for expeditiously milling spots in the wall of the blank for the aforesaidjpurpose.

Another object of the invention is to provide 7 a machine for milling Or machining spots of different controlled depths according to the desired variations in wall-thickness in difierent portions of the blade. 7

Another object ofthe invention, toprovide a machine forthe aforesaid purpose which is readily adjustable to mill .SI Qtsinthe blank on axes at rightangles to longitudinally curved or tapered tubular portions and straight cylindrical portions of the blank.

Another object is toprovlde a machine which can be expeditiously operated for production and loaded with a blankiorfmllling spots in circumferential and longitudinal series in different portions of the blank.

Another object of the invention is to provide machine for this purpose in which the blankis said wheel. Fig. 9 is a front larly defined by claims at thelc'onclusion hereof.

In the drawings:

Fig. 1 is a front. elevation of a machine embodying the invention.

Fig. 12 is a longitudinal section iof'a portion of the bed of the machine, illustrating themanner of securing togetherthe bed-sections, and su pporting the bed.

V Fig. 3 .is a diagrammatic view illustrating the milling toohpositioned for machining a spot in a. tapered portion of the blade-blank.

Fig. 4 is a plan view of the machine. Fig. 5 is an endview of. the supporting structure for the tilting'beams which carry stop or gauge-members used in controlling the depth of.

the cuts.

Fig. 6 is a transverse sectiontaken on line 66 of Fig.4, illustrating the pivotal support for said elevation of the spot milling mechanism... H

Fig. 10 is an end elevation of the milling mechanism viewed from the left hand side.

Fig. 11 is a fragmentary view of the solenoid controlled make for raising and lowering operations of the milling tool. D

Fig. 12 is a partial rear view of the machine.

Fig. 13 is a section takenonline l3--l3 of Fig. 12. V

Fig. 14 is a section taken on line l4-|4 of Fig. 9. r

Fig. 15 is a partial .front elevation, parts being 7 broken away.

3 Fig. 16 is a section taken on line I.8 l6 of Fig. 15. v Fig. 17 is a section taken on line l'L-H of Fig. 15.

Fig. 18 is a transverse section, illustrating the milling tool in elevation and the devicefor ad' 7 x H I ton. and maintaining them in co-related posijusting the stop-plunger movable vertically with said tool.

Fig. 19 is a section takenoni ne I 9fl9" of Fig. 5. Fig. 20 is a section taken on line 20-20 of Fig. 19.

4 tudinally movable and on which the blank is rotatable, .for presenting difierent longitudinal points'or stations on the blank to the spot milling tool; a roll which is calibrated to indicate the "spots where the blank is to be milled; gearing for ldrijointlylrotatingl the blank and the calibrated tions; brake meansfor locking the blank against Fig. 21 is an end view of the carriageior the; blank and the gearing for connecting the tubular 15 engaging its inner periphery, a second beam outblank and therollwhiehis calibrated for.wallthickness for conjoint rotation. v g I 7 Fi 22 is,,a. sectiqn ta en on lin'e 22-22 er Fig. 21. c

Fig. 23' is a action taken on line 23-23 of Fig.21.

Fig.24 is a section illustrating the bearing for the right hand end of the calibr'ated roll.

Fig. 25 is a section takenon line 2525 of Fig. 22.

Fig. 26 is a perspective of one of the internal 2 gripping jaws for the'tubular'bl'ank.

Fig. 27 is a-section taken on line 21-2! of Fig. 15. i

Fig. 2'7 isa detail persnective of the pointer for r'otatively sp'ottingthe tubular blank.

Fig. 27 is .a transverse section through the portion of the tubular blank which has been camturned.

Fig. 28 is a plan view of a portion of thecalibrated tube and thesight Ior'reading the longitudinal stations and ,annularly arranged points for milling the spots.

Fig. 29 is a section taken on line 2 9 29 of' Fig. 18.

Fig. 3'O1is a detail section illustrating the contact-ball carried by one" of the tilting beams for engaging the inner periphery or the tubular" blank.

Fig. 31 is a detail sectionilhistrating the milling tool in its", ilationQtojth ifinercontact for the blank, with a cut of a' predetermine de th.

Fig. 32 is aside elevationof the brake mechanism for the vertical movement of the tool head. Fig. 33 is a plan view of the parts shown in Fig. 32. g

Fig. 34 is a plan view of the tilting beams, the outer of which c'arriesf the contact device for locking said beams: beforefthe spots are milled in the tubular blank. I F

' Fig. 35 is a vertical section taken on line 35-3 5 dfFig.34. l

Fig. 36 is a horizontal section taken on line sit-3s of Fig". 35.

Fig. 37 is'a vertical'sectiontaken on line 31-31 of Fig. 34.

r Fig. 38 is a diagram of the electric circuits and hydraulic mechanisms, for controlling the brake for the vertical movement of the tool, the brake for the blank, the lock for; thetilting beamsQan-d the signals. 3 c Fig. 39 is an; end elevation of amodified form of mechanism for angularlyfshifting the tool.

Fig. 40 is aside elevation of the variable stopdevice shown in Fig. 39'.

Fig. 41 is a sectio'ritaken on line ii-4| of Fig/10.

' The machine exemplifying the invention Com". prises. generally: a bedfor supporting the several mechanisms in accurately co-acting relation; a carriage for the tubular blank, which is 'iongi vertical" is vertically movable; mechanism for controlling thedeptli of the 'cuts made by the tool, which inc1udes, a pivoted beam adapted to extend into the blank and is provided with a contact for side er the blank and movable with the inner beam, at stop-niembeion the outer beam, nd mm ab e s e mean m ab e vertically w the tool; m'e'ans 01 flocking the beams against movement during the milling operations; means for adjusting the tool angularly to produce cutsfin the blanksubstantialiy normal to longitudinally tapered or curved surfaces on the blank; brake means foriarresting the lowering movements 'of the tool until the inner beam is engaged with the inner periphery of the blank; and means for signaling to the operator that the inner beam has engaged the-blank periphery preparatory to a milling operation and also the -6 completion of thefinilling cut.

The several mechanisms of the machine are supportedon a solid bed which is mounted ona rigid framei SL screws'ii carried by frame 5i are adapted-to support the seem a truehori zontai piane'so' it 'wiii neretained'ivei (Figs.

1 and 2 *Tnis is ibrmedof' ctions, the ends of which are sec'ii'i editogether by bolts 54 with a locking bar 55 fitting into and clamped in groovesin the contiguous end faces of the sec- '6 tions."

The carria e generally designated 51, for the tubular blank is" movable longitudinally over the bed and compris'sa left-hand end-frame, generally designated 58 (Figs. 15 and 16), for carry mg the end a of the*ijuloular blade-blank a), a

right hand end-frame g nerally designated 59 (Fig. 1 7)","rod's 50, Si which secure said frames together for longitudinal movement over the bed. End fram'e 58 is equipped with rollers 62 and so tra n es eqe'i eei'witjh rollers" 63 which are adaptedto travel on on the'topj-face of the bedSQ. -Each

frame

58, 58 has scu red thereto a 'bar BS which slides 'i'n a longitudinal groove 65 in the bd-ifl'toiri'sure preciseiectilinear 5 movement o'fthecarriage over the bed and in a plane parallel to" the longitudinal axis of the tubular blank. 'l-iiod- 60 -is provided with notches s1 eerrespondmgto-the predetermined longitudinal stations of the blank which are to be spotmill'ed.

'The blade-blank a, before the spot-milling operations therein, is usually upset or swaged to form hank-form ng end a, a straight cylindric'al portion ofd 't'o be formed into the face 3 sections ofthe blade and a longitudinally taperedportion a between the portions a and a As Well understooddn the artfthe Wall-thickness usually tapers longitudinally from the shank to the tip of the'blade. The portions used in the 7 faces, leading alidtrailing edges of the blade are usually cain'turned' to" "provide maximum wallthickness, along said edges as at aiand reduced thickness in theiace portions between said edges o gan);

' Theshank-end a" of the-blade is secured on the carrI'ageBI for longitudinalimovement over the bed 50 by a chuck or internal gripping devicewhich comprises: a series of gripping shoes I0 (Figs. 22 and 25) which are adapted to grip the,

internal periphery of the blank-portion a and are slidable in radial slots in a chuck-head 'II, which is journalled in a supporting bracket I2 on end-frame 58; an expander I3 for shoes I0 which is axially slidable in head II; and a hand-wheel -'I4 which is screw-threaded to the stem of expander I3, and adapted to axially shift the expander to secure the shoes I0 against the inner periphery of shank a; and an annular spring I5.

prises (Figs. 15,"21) an air cylinder 80 which is supported on bracket I2, a piston in said cylinderand provided with a stem BI, and a brake-shoe 82 adapted to be forced against the outer periphery of the blade-shank a.

Pipes

84 and 84 are provided to alternately deliver air into and exhaust it from cylinder 80, as hereinafter described.

A roll 85 (Figs. 15 and 28) is calibrated as at 86 according to the longitudinal and circumferential locations of the spots to be milled, is rotatably mounted for synchronous rotation with the blank, and supported on the carriage 51 to move longitudinally therewith. One end of roll 85 is secured by a screw 88 (Fig. 23) to a trunnion '89 which is J'ournalled in an anti-friction bearing 90 which is carried by a bracket 9| which is secured to end-frame 58. The opposite end of roll 85 (Fig. 24) is fixed to a trunnion 96 which is journalled in an anti-friction bearing in a bracket 96 fixed to endframe 59. A gear 92 is keyed to trunnion 89, meshes with a gear 93 which is fixed to the chuck-head I I, for rotatively adjusting the blank a and roll'85 in unison,'on the carriage 51. A clamp comprising members 95pivoted to head 58 and a' screw 91 (Fig. 16), is adapted to lock roll 85 against rotation while the blank is being positioned rotatively and secured on .the chuck.

A plate I02 (Figs. 27 and 28) with a sight opening I03- for'viewing the calibrations on roll 85 corresponding to the spot to be milled on the blank by a milling tool I05, is pivoted to the upper end of a bracket I04 which has its lower end fixed to the bed 50. The roll 85 in its longitudinal movement with the blade carriage 51 and its rotative movements on said carriage moves the calibrations 85 relatively to the sight-opening I03 to indicate the longitudinal and circumferential locations of the spots on the blank where the milling tool will operate on the blank and to indicate required wall thickness of the blank. A

dog I04is pivotally connected to the lower por- I tion of bracket I04 and is provided with a tooth I04 which is adapted to drop into'the notches 61 in rod 60 for spotting and locking the carriage 51 and roll 85 against longitudinal movement, at different predetermined longitudinal stations.

The shanks of the'blade blank are provided with punch marks I00 (Fig. 27 .at each of its ends when the blank is cam-turned to define a longitudinal line for rotatively positioning theblank on the chuck corelatively with the calibrations. onv the roll .85.. A pointer IN is. pivotally supported on bracket 1215c register with punch mark I00 on the shank when-the roller is set to indicate the calibrations for-the corresponding longitudinal line. In this manner the blank can f. be initially set on its chuck with the points on the blank to be spot milled correctly co-related to the calibration indicated at sight-opening for roll 85.

The machine comprises a suitable milling tool I05 (Figs. 9, 18.and 31) for cutting spots into the outer surface of the blank and power mechanismfor driving the tool (Figs. 7, 10 and 18). The tool is mounted for verticalmovement to and from. the blank and is removabiy secured in a vertical. driven spindle H0. The mechanism for driving, the tool comprises an electric motor I28, a pulley I30 on the motor shaft, an endless belt I29, and a pulley I3! driven by belt I29 and secured to the.

upper end of the spindle H0, which is rotatably mounted in asleeve 2. Motor I28 is supported on a frame or head H4 and sleeve II2is slidable vertically in said head or frame. The sleeve 2 which carries tool- I05 is vertically shiftable by a handwheel I24 fixed to a shaft I25 which is jour nalled in head I I4 and is provided with a pinion I25 which engages 'a rack 2' on sleeve II2.

Springs I2'I are applied to lift sleeve H2 and the tool I05 carried thereby. Head II4 which supports the tool and the power driven mechanism is clamped to a post II5. Post H5 is supported in a bracket II6 which'is pivotally supported on.

a bracket I19 by a pin I I8 to permit'the head I I4 to be tilted longitudinally of the blank for varying the angular relation of the axis of the tool to the outer surface of the blank. Bracket I I9 is mounted on a bracket I20 which is fixedlysecured on the bed 50. p

The machine comprises mechanism for controlling the depth of the spot cuts of the tool I05 to leave the predetermined wall-thickness desiredin the different portions of the blank. This mechanism comprises a beam adapted to enter the blank and which carries a contact or feel for engaging the inner periphery of the blank at the spot to be milled, a beam outside of the blank which carries a stop member controlled by the contact on said inner beam, and co-acting stopmeans movable vertically with the tool and which isadjustable to vary the depth of the cut. v

V The beam, which enters the blank a is generally designated I40 (Fig. 1), comprises: an

attaching-member I4I, (Fig. 19), which secures said beam at one end to a cross-shaft I42, which is journalled in anti-friction bearings I43 which are supported on a bracket I44, a structural member I45, adapted to extend into the tubularblank, extending from and bolted to attachin member MI, and stiffened by a truss-rod I46;

a socket plate I 41 secured to the distal endof member I45'by.,b'olts and which is electrically.

insulated from saidmember, by aninsulation plate I48 and sleeves I49 (Fig. 30); and a contact ball I50 confined in the socket in plate I41 and adapted to engage the inner periphery of the blank in axial alignment with the milling tool I05.- A mating beam I55 is adapted to extend along the outside of the blank a and is fixed to an attaching-member I56 whichis fixed to cross-shaft I42, and has a block I58 (Fig. 7)

fixedly secured to the distal end. A st0p-' 'member I59 is secured on the top of said blocks The stop-member I59, through beams I40, [55, moves vertically with the contact-ball I50 on beam I40, sothat member I59 will be positioned correspondingly to ball I50 as it is moved into a rmai sulated from said block by sleeves I62 and a strip I63. Counterweights II are carried by a rod I52 which is fixed toaplate I52 which is fixed to attaching-members I4 I, I 56 for pressing the contact-ball I50 into engagement with the inner periphery of the lolanka.

The means for co-acting with the stop-member I59 on beam I55 which i :controlled by the inner periphery of the :blank :11, .to limit the depth of the cut of tool .I'05,.ls mounted on a housing or head'III whichiiscclamped to sleeve H2 and is movable vertically with said tool and adjustable to selectively centre-lathe: depth ofthe cuts according to the wall-thickness -desired'in different portions of the: blank; This means comprises: a stem I85 (Figsrii, 18) adapted :to engage the-stop-member I59 'onbeams I55 and secured to a plunger I86 which is slidably mounted inthe housing. III and is providedat its upper end withan'inclined cam-surface I90; 2. wedge-member l9lmountedin housing III to slide'transversely of the plunger 'I 86;:a slidable yoke I92 (Fig. 29) secured to wedge-member I9I; an index arm I93 fixedly'secured'by screws toa hub 200 on the front end of yoke I92; 'a stem I95 providedwith-a screw-thread I94 and keyed in "forwardly projecting bosson housing' III; an index wheel Ii96'having a hub provided with a screw-thread engaging the screw-thread I94 on non-rotatablestem [55,-Withcalibrations I91 which indicate the fractionalrotations of the wheel I96 from apredetermlned-position on a-pointer I98 on index arm I-93; 'and-a split' collar I99 secured to an inner face of the hub'of'wheel- I99 by screws and having a rib fitting in an annular groove in hub 200 ofyoke I-92 for imparting sliding movement to the-yoke I92=and wedge-bar I9I by the axial=movement of yoke I92 resulting from rotation of said wheel on thescrew-thread I94 on stem I93. The front end of stem I95 is pi'ovidedwith annulargrooves 202, which with the front bevelled edge of a :sleeve 294 on Wheel I96 indicate the rotations of the hand whe'el I96. The calibrations I91 on the said wheel I96 and grooves202'indicate the position of the stem I85 'for -arresting'the lowering movements of housing I II and the tool I05 until said stem engages the stop-member 459 on beam I55. Rotative adjustment-of han'd wheel I95, through its screw-threaded connection with stem I95 slides the yoke I92 to shift wedge-bar I9I laterally'for shifting plunger I 86' and stem I85 vertically,relatively to the housing .III which is-slidable with'the tool I05 for arresting the tool I05'when ithas milled spots to the correct depth to leave the desired wall thickness in the blankat the respective spots. A

spring 295, engaging a shoulder .onpl'unger I86,v

holds the latter in engagement with cam bar I9I. This mechanism is. adapted for micrometric adjustment and indications of the depth of the cut made by the tool I05, for the precision desired in the wall-thickness of propeller blades. During'each downward milling stroke of. the 1001 I05 by hand-wheel I24, the .stop-iplunger I85 will engage the stop-member I59. on beam I55, the position of which'is'controlled by the engagement of stop-member 150 on he-am :I40 with the inner periphery of the blank. For guiding-the housing III and tool IU'JTIBCIJIHIIBMIY .and;preventing deflection; a guidezblcck w-ll35'iis rfixed to 8. housing III,'and' is slidablein'a'g uide I 36, which is fixed to the bracketI' I 6.

A 'fluid controlled locking-mechanism (Figs. 7, 35 and 36) is provided for locking the beam I55 and stop-member I59 against movement during the milling operations of tool I05. This mechanism comprises a post I64, the upper end of which isfixedly secured in and depends from black I58; shoes I65, I 61 for gripping post I64; springs I63 forreleasing the shoes; 2. block I10 inlwhich the shoes I61 areslida'bly confined and which is secured by bolts I1I, to a bracket I12, which is .secured to bracket I20; aWedge-bar I14 which is horizontally slidable between shoe I61 and the innerside I 55 of bracket I12; a cylinder I16, supported by an extensionion bracket I12, and connected to pipes I18, I19 for alternately delivering and discharging fluid under pressure; and a piston operable by saidfiuld and provided with a stem I80, which is coupled by a pin I8I to the wedge-bar I 14.

In spot milling partially fabricated blanks for propeller blades, it is necessary for precision in leaving the necessary wall-thickness to operate the-tool on an axis which is substantially perpendicular to the surfaces of the blank, and for this "purpose it is necessary to vary the axis of the tool relatively to the blank where the latter has tapered or'longitudinally curved portions. The pivot pin I I8 is supported in the'stationary bracket H9 and the bracket H6 which supports the post[ I5, the head I M and the driving mechanism for the tool I55 is journalled on the pin II8,-so as to permit the operation of the tool in different angular relations in a plane-parallel to the longitudinal axis of the blank, so the axis of the too1- will be perpendicular to the longitudinally curved or inclined surfaces on the blank, as diagrammatically indicated in Fig. 3. The bracket H6 is locked in its adjusted angular positions, (Figs, 9, 14 and 15) by a screw-clamp 209 threaded into an arm ZIEI which is fixed to the post II5 which is fixed in bracket H6; and extends through an arcuate slot ZI I in a member 2I2 which isfixedly supported at the upper end oi. a bracketZIS (Fig. 12) which is secured to the bed 50. The member 2I2 has minute calibrations 2I4 for indicating the settings of the bracket I I6'and the parts carried thereby.

Mechanism for shifting the bracket IIB comprises (Figs. 10, 12 and 13) an arm 2I5 depending from and fixed to bracket H6, at screw-shaft 216 journalled on the bed '50, a runner 2l1 on shaft 2I61pivotally connected'by pins 2I8 to arm 2I5,-a transverse shaft 2I9 provided at the front of the bed 59 Withahand-wheel 220, and bevelgears 22I between shafts M5 and M9.

Brake means is provided for the lowering movements of'the tool I and comprises (Figs. 11, 32 and 33) a finely-toothed ratchet-Wheel-224 which is'flxed to the shaft of hand-wheel I24; atoothed dog 225 fulcrumed on hea-dII I and adapted to engage wheel 224; a spring 226 for yieldingly holding .dog 225 engaged with Wheel 224; and a solenoid magnet 221 for shifting dog 225 to release wheel 220. Dog 225 and ratchet wheel 224 act to hold the hand-wheel I2'4'and the sleeve switch 228 and conductor 22911 to plate I41 which is insulated from beam I40, ball I 50, and the blank a to the frameof the machine which is connected to ground. The release of this brake does not occur until the'ball I50 has contacted the blank a. A low-voltage signal lamp 230 (Fig. 38) is connected in parallel with the circuit for. switch 228 to signal the operator that the contact-ball I50 on beam I40 has engaged the inner periphery of the blank a and that the brake on the tool I05 has been released by dog 225 in readiness for a milling operation.

A lamp 23I is included in a conductor 232 which is connected to the insulated stop-member I59 on beam I55 (Figs; 37 and 38) and to transformer 229. When stem I85 contacts insulated stop-member I59 which is carried by beam I55, which occurs when the spot has been milled to the predetermined depth, the circuit for lamp 23I will be closed to indicate the completion of.

" riage 51 will next be shifted to the right so the greater thickness at d for the leading and trailing edges and lesser wall-thickness between the said edges" (Fig. 27). The blank is punched marked as at I00 to rotatively spot the line along the leading edge line extending longitudinally of the 1 blank; The calibrated roll 85 is rotated to position the line of calibrations corresponding to the 1 line on the blank indicated by'the punch mark I 00 at the sight openingl03, and locked by tuming screw 96 to'cause members '95 to clamp roll 85 against rotation. The blank is then placed on

rollers

16, 11 with its shank around the chuck member 1|." The punch mark I00 is spotted in alignment with the pointer IOI which is pivotally supported so it can be swung to engage the blank.

After the blank-has been thus rotatively positioned on chuck member 1I hand-wheel 14 is rotated to expand jaws 10 into gripping engagement withthe blank. Next the screw 96 will be turned to spread clamping members 95 and release the roll 85 so'that the said roll and the blank will be conjointly

rotatable through'gears

92, 93.

' The calibrations'on roll 85 will then be correctly co-related with the'blank for milling the spots in the blank corresponding to the calibrations on roll 85. While the'blank is being secured on end of cylinder I16 and'exhausts air from its other end, for retractingb'ar I14 to release beams I40, I55 for pivotal movement. When the valvepedal is depressed, the air flow to and from cylinder 80 will be reversed to apply brake 82 to the blank a and reversed to land from cylinder I16 for shifting the wedge-bar I14 and releasing the beams I40, I55. A switch 2H for controlling motor I28 is mounted on arm 2I0 (Fig. 10).

A modification of the means for the angular adjustment of the milling tool I05 and itssupports is illustrated in Figs; 39 to 41. This includes a cylinder 240 which has its rear end pivotally connected at 24I to a bed-supported bracket 242 and is provided with a piston, the stem 243 of which is pivotally connected at 244 to arm 2I0 which is fixed on post I I5. Fluid, such as air under pressure,- is alternately delivered into and exhausted from the ends of the cylinder by pipes" 246 and 241,for operating the piston in opposite directions. A stop or abutment 249 is fixed to the underside of bracket I I6 for engagement with variable stop means for arresting the bracket I I 6 in different angular positions. comprises a disk 250 provided with stepped stop-faces 25I of difierent radii, trunnions journalled in a bracket 252, which is vfixed to stationary bracket H9; anda handle 253 for rocking the disk. A spring detent '254 is pressed into notches in one side of disk 250, for yieldingly spotting the faces 25I in position for engagement by abutment 249; In'this construction the pressure of fluid in cylinder 240 urges the bracket I I6 so the abutment 249 and the disk will firmly hold thebracket in predetermined angular posit-ions. A stop pin 256 limits the'rotative movement of disk 259. 1

The operation of the machine is as follows: the

blank a. to be spot-milled is partially fabricated by upsetting one end portion thereof to form a shank a, shaping the tapered portion a and camturning the remaining cylindrical portion to provide the variations in the wall-thickness desired in the diiferent portions of the lathe', such as This stop-means carriage 51, the latter will be positioned at the left hand side of bed 50150 that the large end of the blankwill be to the left of beam I40 and the latter will not extend'into the blank. The'carblank will extend around the contact-ball I50 on beam I40. The carriage with the blank thereon will be shifted by the operator longitudinally of the bed 50'to oneiofthe predetermined longitudinal stations for spot milling at that station. The carriage 51 will be there locked against longitudinal movement by'the dropping of dog I04 into one of the notches 61 in rod 60 of the carriage 51. "At each longitudinal station the blank may be rotated-on the carriage correspondingly to the calibratio'ns'oi' a circumferential series of roll 85 for spot milling corresponding series on i the blank. The carriage 51 is successively moved from one longitudinal station to the next and the blank thereon 'is rotated on the carriage 51 at each longitudinalstation, for milling each of the points desired. The ball I is'supported'by beam I40 in substantial axial alignment'with'the t-ool I05; The milling tool is operated as hereinafter described for singly cutting the spots at the several longitudinal stations. i

The operator will rotatively set wheel I06 to adjust the stop-plunger I85 so that the lowering movementof the millingtool I05 will be arrested by the stop-member I59 on the locked beam I55 when the milling tool has cut away the metal in the wall of the blade to leave the predetermined "wall-thickness desired at each spot. This depth wi l be indicated by the pointer I96 on the calibrations I91'on' wheel I96 and the groove 202 on stem I93.

Assuming'the'blank etc have been secured 'on carriage 51,and"positioned as before described for milling a spot, the counterweights I5I will press the contact-ball I50 on beam I40 into contact with theinner periphery of the shank of the blade'and thestop-mernber I59 'on beam I55'will 'be'correspondingly positioned. The operator will then depress the pedal of valve 260 to supply compressed fiuid to cylinder 80 to operate brake shoe .82 against the outer periphery of the shank of simultaneously "supply compressed fluid to cylinthe blank and'lock the'blank and the calibrating roll'against rotation'on the carriage 51 and to