US2859936A

US2859936A - Compressor blade and method of forming same

Info

Publication number: US2859936A
Application number: US413743A
Authority: US
Inventors: Elmer P Warnken
Original assignee: Cincinnati Testing and Research Laboratories
Current assignee: Cincinnati Testing and Research Laboratories
Priority date: 1954-03-03
Filing date: 1954-03-03
Publication date: 1958-11-11
Anticipated expiration: 1975-11-11
Also published as: GB775816A

Description

Nov. 11, 1958 E. P. WARNKEN 2,859,936

COMPRESSOR BLADE AND METHOD OF FORMING SAME Filed March 3, 1954 3 Sheets-Sheet 1 IN V EN TOR.

ELMER WARNKEN BY 0 m 9 V Y Y Azys.

Nov. 11, 1958 E. P. WARNKEN I 5 ND METH D OF FORMING SA r 5% IN VEN T 0R v ELMERPWARNKEN NW, H 1958 E. P. WARNKEN 2,859,936

COMPRESSOR BLADE AND METHOD OF FORMING SAME :5 Sheets-sheaf 3 Filed Marh s. 1954 INVENTOR. ELMER R WARNMEN United States Patent zesi'sss comnas son time Animyniinoij 6F FoRMiNG SAME eingi P.' wanna, Cincinnati, oifiaass'aasats era-an nati Testing & Research Laboratories, ilincinnati, Ohio; ii l iartiisliip Application March 3 19 54,-Serial N6. 413,743

Claiins. c1. ass- '77 Th s i t ar aw cm lade tmra a pre ses; bl we Q l de le; M te r'at iqu y. th tent oare a bm'n e 'q l e ies 'a i its. pressprs and to a method for making such compressor da g t. ten 'fbie a flfi n e i n, s t P a e1 a l l blade composedofa resin whichis reinforced by e'lon gated glass fibres that extend the length of the add and areprestressed ir tension so that the body at the blade is stre'ssedin corih'pres'siorn thereby giving the body of the b l the strength required t6 carry the load tau-sea by cen fng' al force' I A fnrth e r object of this invention i s to provide a blade of this type in which the fibers extend lengthwise of the blade are of folded doublet form, the fold of the doublet being at the root at the blade. I A: fnrther object of this invention is to" ieviaei are; stressed cornpressor blade having a core of reseessea lengths of fibre glass material anda skin ar'oiiridth' tria ter ial which gran is formed of amiiiture of res n and short staple glass fibres the pres tress'ed lengths of fibre glass material stress'ihg th resin and the shaft staple fibies in compression. v r v A further object of this invention is; te pr'oyidea blade of this type in which a rigid-pin extends the folder the doublet so that the folded end i thereby rendered thicker than the remainderof the blade, an shaped to form a retaining key at the robt end of the blade;

A farther object of this inventior'i is' o provide a blade of this type in which the pin is a pager slotted key member h ving a key pbitiohand a pin portion spaced fr'en'i each other by thef ;s1dt and iii which the lengths of fibre glass materiai extend thrdtigh the slot of the key member. u h r Ahd a further ghje'c't of this invention is to provide" a method of forming a prestres'sed blade having a core of lengths of resindinpregnated fibre lass material arid a skin formed of resin and short staple fibres which includes the steps of disposing the lengths of material in an elongated mold, and, while in the mold, stressing the material in tension and injecting into the mold a miiiture of resin and short staple" gla'ss' fibres to impregnate and cover the lengths of material; aiid then curing the resin to form a hard, infn'sible pr'es'tres sed resin bladeandbla'de rbo t.

The above and other objects and features or the invention will be apparent to those havin'g' or'dinary' skill in the art to which it pertains from the renewing detailed pt e n hedtw a n whi is l s a a a tiiev s .ShQ et mr' s q blade constrncte'd iri accordance with an embodiment of s n s. a 7,, .7. it it Big. 2 is a plan view of a mold for forming the blade; 4 Fig. 3 is a view in section taken on the line Hi -III in Fig. 2, pres'tresis'ed rovings being shown in the mold in position after mo lding; I Fig. 4 is a view in section taken on the line IV-'IV in Fig. 3;

2,859,936 Fatented Nov. 11, 1 958 Fig. 5 is a perspective view' showirigari alternate forni er pin for nse'in forming the blade;- y r r Fig. 6 is a" schematic view showi'g the operationof the prestressing mechanism of the mold;-

Fig. 7 is a schematic v' lew showing; a porti'o' i of the rotor afar; axial flow air compressor with one or the blades -mountedthereon; m l

Fig. 8 is a perspective View showing a blade-' coil struc ted in accordance with aii'other etnbo'dirfft':fit of the invention;

Fig. 9 is a perspective view showingthepin ofthe Blade iiltistrated inFi'g. 8; 1

Fig. 10 is a fragmentaryperspective view showing" the arrangement of rovings on the pinp're'pa'ratbry to the moldingof theblade illustratedin hi'gt'sz Y Fig; 11 isa View in vertical sectiomshowiiig the'rnb'l'd' used'iri forming the blade illustratedirrFig. 8;

Fig: 12 is a fragmentary sectional view of the blade illhstrated'in'Fig. 8'; i i i Fig." 13 is a perspective view showinga blade' con-T structed in accordance with another embodimentof this" invention;

Fig; 14 is a perspective View showing a key andpin' member Which forms apart of the blade illustratedfin' Fig;;;1'3; I f

Fig; 15 isja perspective'view 'showing'the arrangement of elongated ro'vings ofl the key and pinmeinber'prior to the molding of the blade illustrated in Fig. 13;

Fig; 16 is' a fragmentary sectional view showing the mold for molding the blade illustrated ,in Fig: 13, the mold being shown before the injection of resin andshort staple glass fibres; i t, t

Fig.- 17 is a sectional view showingthe mold of Fig. 16 following injection; H

, Fig. 18 is an exaggerated sectiojnal view of the blade illustrated in Fig. 13; and

Fig. 19 is' a schematic view showing the arrangement of rovings and pin used in molding the blade shown in Figzlt in the following detailed description,- and the drawings,- like reference characters indicate likeparts I r In F s 1 t o n. a, ca re v th de? r' axial-flow air compressor, such as the gornpressor section of a jet'aircraft engine. The blade 2 comprises avane portion 16 of airfoil configuration-and a root end portion o generally t dr s a -i ,Th s e s. t fl isd to be mounted 'n a slot 13 'n arotor ring 14 of a-compressor; as showrrin Fig. 7,.

In the formation or the blade 9, lengthslofelongated fibre glass material 16 (Fig. 19) of resin-impregnated glass fibres are arranged in doublets. throi' 'gh the lo'o'poi fold of which a pin 17 extends. The material may be fibre glass fabric or Woven clothl, Preferably, the mate rial is in the form of elongated rovings which extend lengthwise of the blade. The fibres of the material may be coated with a thermo-settingresimby dipping the same in the resin. As indicated in Figs. 3 and 6, the mat ial 16 and thhe pin 17 are, placed in a lower mold rnembe'r 18. The free or blade" tip ends of the material are clamped to mold member :18 by means or" a clamp plate' 19 secured tomernber. 18 by means rma hines rew 2. wh n i ,1 slqc ed Slots z i n 2 n' he mold member 18, he material is stressed in tension, as will be explained. p i r! As indicated in Fig. 6, the distance f rom t M1 the u pe d of the t 1 3 .23 3 haw the distance B to the lower ends of the slots; Thus when the pin 17 is advanced downwardly into the

slots

22 and 23 the rovings are stressed in tension. When the material is stressed, a space 24 opens between the converging portions 24a and 24b of the rovings. A plug 24' of resinimpregnated glass fibres may be disposed in space 24 to provide material for filling this space when the blade is molded (see Fig. 19).

The mold member 18 is provided with a molding surface or face 25 which is of airfoil configuration for molding the vane portion of the blade. At the left hand end of the face 25 is provided a rounded mold portion 25' for molding one face of the root end of the blade. When the pin and fibre glass material are positioned in the mold, a movable mold member 26 is actuated by a ram 26' into the cavity of the lower mold member 18 against the material and the fold containing the pin 17, whereby the pin is forced into the bottom of

slots

22 and 23 and the material is stressed in tension, and the resin is molded and set. When the plunger is raised, as indicated in Fig. 3, the resin holds the material in prestressed condition.

The lower face of the plunger 26 is provided with a mold cavity which mates with the molding face of the lower mold member to form the blade. While pressure is applied to the mold by ram 26', the prestressed material and resin are heated to sufficient temperature and for a sufficient time to cause curing of the resin, and theresin, when cured, holds the material in prestressed condition and forms a hard, smooth, infusible blade surface. After curing, the blade is removed from the mold and trimmed to the final shape of a finished blade as shown in Fig. 1.

In the finished blade, the tension of the fibre glass material stresses the resin of the blade in compression. Preferably the blade is prestressed to sufficient degree so that the prestress load on the blade is greater than the design load level to be produced in the blade in actual use. Thus, when the blade is mounted in the rotor ring 14 and in actual operation, the prestress load maintains a compression in the resin of the blade. 7

As shown in Fig. 1, ends 27 of the pin 17 project beyond the ends of the blade. The ends 27 may be retained, as shown in Fig. 1, or, if desired, the ends 27 may be trimmed off flush with the ends 28 of the blade (only one of which is shown).

The pin of the blade described to this point is shown as a round pin. If preferred, a pin of the form shown in Fig. 5 at 30 may be used instead of a round pin. The pin shown in Fig. 5 includes a main portion 32 of tear drop shape. At the ends of the main portion 32, integral rounded portions 33 and 34 are provided. The portions 33 and 34 are receivable in the

slots

22 and 23 of the mold 18. When the pin of Fig. 5 is used, the blade is formed in the same manner as when pin 17 is employed, but in that case pad 24' is not required as the pointed portion 36 of the pin 30 fills the gap between the layers of material atthe root end of the blade.

The blade illustrated in Fig. 1 is of particular use where a slot 13 of the special shape shown in Fig. 7 may be employed for receiving the root end of a blade. However, for some purposes, a blade 38 of the shape illustrated in Fig. 8 is more desirable because the blade illustrated in Fig. 8 can be used with rotors constructed to employ conventional blades. The blade 38 shown in Fig. 8 includes a metal pin member 39 (see Fig. 9). The pin member 39 includes a main portion 41 of tear drop shape, and root-strengthening

rib members

42, 43, and 44. In the formation of the blade illustrated in Fig. 8, the pin 39 extends through the loop of the doublets of glass fibre rovings 46 or the like, in the manner shown in Fig. 10, and the rovings and pin are positioned in a mold, as shown in Fig. 11.

The mold of Fig. 11 includes a lower member 47 and an upper member 48. The mold contains a mold cavity 49 between

members

47 and 48. The elongated rovings extend through an opening 51 ,at one end of the mold 4 cavity and are clamped by an appropriate clamp 52. The clamp 52 is urged to the right, as shown in Fig. 11, to prestress the rovings 46. When the rovings have been prestressed, a molding compound consisting of a mixture of resin and short stable glass fibres is introduced into the mold cavity through a gate 53.

The short staple glass fibres may be of relatively short length, say about one-half A2) inch, for example, whereas, the length of the elongated prestressed rovings is greater than the overall length of the finished blade. Preferably, both the elongated rovings and the short staple fibres are resin-coated or impregnated. The resin-impregnated short staple fibres are forced into mold cavity 49 under a very high pressure of the order of magnitude of two and r one-half (2 /2) tons per square inch so that the short staple fibres and resin are forced around and through spaces between the fibres of the prestressed rovings to form a body and outer skin or blade surface and filling a root end cavity 54 and encasing the pin 39. The mold pressure is sufiicient to compact the resin and short staple fibres around the rovings to form a solid blade mass. While under pressure, the blade is heated to a sufficient temperature to set the resin and form a hard infusible blade mass. The molding compound preferably contains short staple glass fibres but may contain a resin and other suitable short fibres.

In the finished blade 38, the short staple fibres form a section 54 overlying and surrounding the prestressed rovings 46, as shown in Fig. 12. The prestressed rovings are thus stressed in tension in the finished cured blade, while the resin and short staple fibres in the vane portion 56 of the blade (see Fig. 8) are stressed in compression.

In Fig. 13 is shown a blade 61 having a rigid metal key and pin member 62 having an exposed metal key portion 63 which may be inserted in an appropriate key-shaped slot of a rotor. As shown in Fig. 14, the member 62 is provided with a slot 64. The slot 64 divides the member 62 into the key portion 63 and a pin portion 66 with the slot 64 therebetween. The

portions

63 and 66 are connectcd together by end plate members 67 and by a sufficient number of bridging members 68 to maintain the

members

63 and 66 in rigidly spaced relation. As shown, a portion of the member 63 is cut away, as indicated at 69, to form a gate through which resin-impregnated short staple fibres are injected during molding of the blade 61.

The key and pin member is preferably formed of rigid forged metal or the like.

As shown in Fig. 15, resin-impregnated doublets 71 are formed upon the pin 66 with the folds of the doublets extending through the slot 64. The doublets may be of fabric but preferably are rovings of glass fibers. The key and pin member 62 and the doublets of rovings 71 are disposed in a mold 72, as indicated in Fig. 16. As shown in Fig. 16, the mold 72 includes a lower portion 73 and an upper portion 74 between which are formed two

mold cavities

76 and 77. Free ends of the rovings 71 are clamped by means of clamps 78, and the clamps are urged away from the center of the mold to prestress the elongated rovings. Then, resin-impregnated short staple rovings are injected into the mold cavities through gate 79 to fill the mold cavities around the elongated rovings. As shown in Fig. 18, in the finished blade, the elongated rovings 71 are-surrounded by a mass or skin of resinimpregnated short staple rovings 81. In Fig. 18,'the mass 81 is exaggerated in size'for clarity of showing.

The blade 61 includes an exposed metal member 63 of key shape which takes the stress on the key portion of the blade when the blade is in use.

The prestress load of each of the blades is preferably calculated to be sufiicient so that the internal centrifugal force load of the blade during use is all taken by the prestressed elongated rovings, and the resin and short staple fibres remain under compression even when the blade is in rapid rotation during use. For a blade four (4) inches long and having a cross section area of one-quarter (l4) of a sc'iuar inch for use in a rotor having a tip diameter of thifty-fiv (35) inches androtatioiial rate of eight thousand (8,000) R,, P. M.,, the p r es tress load on the elongated rovings may be ap ma one thousand fifty (11 050) pounds. The pfestressing; is suflicient to maintain centrifugal load off the resin of the blade within safe working limits. In other words, the prestress compression of the body of the blade will not be sufiiciently dissipated when rotating within intended maximum speeds, to cause failure of the blade.

The compressor blades described above and illustrated in the drawings are subject to structural modification without departing from the spirit and scope of the appended claims.

Having described my invention, what I claim as new, and desire to secure by Letters Patent is:

1. A prestressed airfoil rotor blade which comprises a rigid key and pin member comprising an outer portion of key shape, a pin spaced from and substantially parallel to the outer portion, and bridging members holding the key-shaped portion and the pin in spaced relation, a plurality of prestressed elongated rovings of doublet form, each doublet having a loop at one end thereof mounted on said pin, and a cured resin impregnating the rovings to hold the rovings in tension, the blade at the doublet loops of the rovings being of key shape, the portion of the rovings remote from the pin being of airfoil configuration.

2. The method of forming a blade having airfoil surfaces, the blade having a calculated centrifugal load capacity and being composed of resin-impregnated fibres, that consists in laying resin-impregnated fibres in a mold having a cavity shaped to the configuration of the blade, stressing the fibres in tension in a direction lengthwise of the mold cavity to a load at least-equal to the calculated load capacity, closing the mold on the stressed fibres, and, While maintaining said tensile load, heating the fibres to a temperature at which the resin sets.

3. The method of forming a cured resin airfoil rotor blade having prestressed fibre glass reinforcement and a rigid metal root key and pin member which comprises impregnating glass fibres with a resin, forming a doublet of said glass fibres about the root key and pin member, placing said glass fibres and root key and pin member in a die cavity, stressing the fibres in tension substantially normally to the axis of the key and pin member and setting the resin while the glass fibres are stressed and molding the resin between dies to mold the resin and glass fibres to an airfold blade shape.

4. A prestressed airfoil rotor blade which comprises a rigid key and pin member comprising an outer portion of key shape, a pin spaced from and substantially parallel to the outer portion, and bridging members holding the key-shaped portion and the pin in spaced relation, a plurality of prestressed, elongated rovings of doublet form, each doublet having a loop at one end thereof mounted on said pin, a cured resin impregnating the rovings to hold the rovings in tension, the blade at the doublet loop of the rovings being of key-shape, and a mass of resinimpregnated short staple fibre glass forming a skin surrounding the prestressed rovings, the portion of the blade remote from the pin being of airfoil configuration.

5. The method of forming a cured resin airfoil rotor blade having prestressed fibre glass reinforcement and a rigid metal root key that comprises impregnating rovings of glass fibres with a phenol-formaldehyde resin, forming a doublet of said impregnated rovings to provide a loop at one end thereof, inserting a root pin through the loop, stressing the rovings in tension in a direction normal to the axis of the pin, covering said rovings and pin with a phenol-formaldehyde resin, applying heat and pressure to the same to impregnate the rovings and form a hard, smooth surface on the blade while the rovings are stressed in tension, and setting the resin coating on the fibres in the rovings to a hard and infusiblemass while the fibres of the rovings are in tension. x 6 The method of forming a cured resin airfoil rotor blade'h'aving prestressed fibre glass reinforcement and a rigid metal root key that comprises impregnating" rovings of glass fibr es" with a phenol-formaldehyde resin, forming a'doublet of said impregnated rovings; to provide a loop at one end thereof, inserting a root pin through the loop, stressing the rovings in tension in a direction normal to the axis of the pin, and covering said rovings with a mix ture of phenol-formaldehyde resin and short staple glass fibres, and, while the rovings are in tension, applying heat and pressure to the same to impregnate the rovings and form a hard, infusible resin blade and root surface.

7. The method of forming a cured resin airfoil rotor blade having prestressed fibre glass reinforcement and a rigid metal key and pin member, that comprises impregnating rovings of glass fibres with a phenol-formaldehyde resin, forming a doublet of said impregnated rovings to provide a loop atone end thereof, inserting a root key and pin member through the loop, placing said rovings and member in a die cavity, stressing the rovings in tension in a direction normal to the axis of the root key and pin member, injecting an injectable phenol-formaldehyde resin molding compound into the die cavity through a gate under pressure, and applying heat to the mold to set and cure the resin while the rovings are stressed in tension to a hard, infusible mass throughout the blade and the rovings, and form a hard, smooth surface on the blade.

8. A method of forming an airfoil rotor blade which comprises forming a core of elongated, substantially parallel resin-impregnated rovings in a mold cavity having a root end and a blade portion, the rovings extending lengthwise of the blade portion, stressing said rovings in tension in a direction normal to the axis of the root end and lengthwise of the blade portion of the mold cavity, injecting short fibre resin-impregnated injectable rovings through a gate into said mold cavity around said elongated rovings to fill the root end of the cavity while the rovings are stressed, and curing the resin to form a hard, smooth blade surface, whereby the resin holds the rovings in tension. j

9. A method of forming an airfoil rotor blade which comprises forming a core of elongated substantially parallel resin-impregnated rovings in a mold cavity having a root end and a blade portion, the rovings extending lengthwise of the blade portion and into the root end, the elongated rovings partially filling the mold cavity, stressing the rovings in tension in a direction normal to the axis of the root end and lengthwise of the blade portion of the mold cavity, injecting short fibre resin-impregnated injectable rovings through a gate into said mold cavity around the elongated rovings to fill the mold cavity around the elongated rovings while the rovings are stressed in tension, and curing the resin to form a hard smooth blade surface, whereby the resin holds the rovings in tension.

10. A method of forming an airfoil rotor blade which comprises forming a core of elongated resin-impregnated rovings with a return bend at one end of the core about a transverse pin, the rovings extending from the pin into substantially parallel parts, the rovings being disposed in a mold cavity having a root end portion and an elongated vane-forming portion with the return bend in the root end portion of the cavity and the parallel parts extending lengthwise of the vane-forming portion, stressing the elongated rovings in tension in a direction normal to the axis of the transverse pin, injecting short staple resinimpregnated injectable rovings through a gate into said mold cavity and around the elongated rovings while the rovings are stressed, and curing the resin to form a hard, smooth blade surface, whereby the resin holds the elongated rovings in tension.

(References on following page) References Cited in the file of this patent 2,621,140

UNITED STATES PATENTS 3 2,630,868

1,035,364 Leblanc Aug. 13, 1912 2,182,812 Lougheed Dec. 12, 1939 5 501,649 2,484,141 Alex Oct. 11, 1949 502 409 2,511,421 Werner June 13, 1950 2,602,766 Francis July 8, 1952 8 Bitterli et a1 Dec. 9, 1952 Elle'nberger Mar. -10, 1953 FOREIGN PATENTS Great Britain Feb. 27, 1939 Great Britain Mar. 13, 1939