US2147005A - High temperature fan - Google Patents

Description

Feb. 14, 1939; F, WILLIAM 2,147,005

HIGH TEMPERATURE FAN Fil'ed May'6, 1938 5 Sheets-Sheet l Feb. 14, 1939. c w Ms 2,147,005

HIGH TEMPERATURE FAN Filed May 6, 1938 5 SheetsSh eet 4 Feb. 14, 1939. F. c. WILLIAMS 2,147,005

\ HIGH TEMPERATURE FAN Filed May 6, 1938 5 Sheets-Sheet 5 Patented Feb. 14, 1939 UNITED STATES PATENT OFFICE Francis 0. Williams, Dearborn, Mich.

Application May 6, 1938, Serial No. 206,433

- In Great Britain March 13, 1937 16 Claims.

This invention relates to centrifugal fans or blowers for handling gases at high temperatures.

In the nature of things such a fan gets hot. and expands. In many instances the shaft is cooled .and the unavoidable effect is a temperature difference perhaps at times as much as several hundred degrees between the inner and outer parts of the fan wheel, though actual measurements are diflicult.

In all prior constructions (that I have been able to find) the expansion of the parts, varying as it does with the temperature, has caused distortion and thrown the fan out of dynamic balance. In some prior constructions the work of fabrication has set up internal stresses that, being relieved by heat, have caused other distortion. And, of course, lack of dynamic balance at the necessary high speed soon develops unit stresses that no material can endure at high temperature. As a result, fans for handling high temperature gases have been short lived and costly.

The principal object ofthis invention is to overcome the difficulties of the past and provide fans that will endure long periods of service at high temperature. Generally speaking, this is accomplished by allowing such movement between the parts that each may expand according to the law of its being without putting strains on any other part, or throwing the fan out of dynamic balance.

Several forms suited to different conditions are shown in the drawings in which:

Fig. 1 -is a diagrammatic front view of a centrifugal fan with the casing cutaway along the middle;

Fig. 2 is a similar diagram looking at the side of the fan with the near half of the casing removed;

- Fig. 3 (Sheet 2) is an axial section through the double fan proper and its shaft;

Fig. 4 is a perspective view of one of the wheellike side pieces of the fan;

Fig. 5 is a perspective view of one of the fan blades;

Fig. 6 is a perspective view of a spacer, two of which are interposed between the side pieces .and

10 is a section taken on the line Ill-Ill of Fig.

Fig. 11 (Sheet 3) is an axial section through a single fan proper;

Fig. 12 is a perspective viewof one of the fan blades;

Fig. 13 is a side View of the fan with one-half broken away, as by a section taken at right angles to the axis, as indicated by the line I3-l3 on Fig. 11; r

Fig. 14 (Sheet 5) is an axial section of a double fan for less high temperatures;

Fig. 15 (Sheet 4). is a side view with half broken away, as on a section indicated by the line Iii-l5 on Fig.14;

:Fig. 16 is an enlarged detail showing the interlocking'joint between one of the fan blades and 4 one of the shrouds;

Fig. 1'7 is a transverse section on line l1-l'l of Fig. 16;

Fig. 18 is a view similar to Fig. 16, showing an alternative formof interlocking joint;

Fig. 19 is a transverse section on the line Ill-I9 of Fig. 18;

Figs. 20 and 21 are fragmentary views showing '25 an alternative form of fastening for the ,inner ends of the fan blades.

Referring now to Sheets 1 and 2, Figs. 1 and 2 show a double fan l0, mounted on a water cooled shaft ll, within a casing l2,-and the shaft is journaled in bearings l3 and driven by a pulley 14.

-As will be seen particularly in Fig. 3 (Sheet 2) the shaft ID has a hollow, or bore, |5.through which a cooling fluid is to be circulated to keep the temperature of theshaft within an allowable range for the strains put upon it.

The fan includes two side members, indicated generally by the letters A and B, each having a hub 16, spokes I! and a rim l8, here shown as cast in one piece, but that is a matter of choice. The side piece B is held against rotation on the shaft II by a key I9 which, in turn, is secured in place against the end of the key'slot 20 by the hub of the side piece. The side piece A is similarly secured by a key 2l, fastened by-a plate 22, held in place by screws 23. Between the two side pieces are spacers 24 and 25, in fact parts of the hub, but for convenience in assembling, made in separate pieces. They are fixed to the shaft II by a key 26.

In thisparticular embodiment the inner face 21 of each shroud is inclined and provided with a series of radial grooves 28 to receive the edges of the fan blades 29, the ends 30 of which are slightly thickened to form tongues to fit within the 56 grooves 28. The intermediate portion of each groove 28 is curved 'and deepened at 3|, as by being milled with the familiar form of cutter and the corresponding portion of the tongue .is curved lengthwise at 32 like a Woodruif key. This form of tongue and groove affords a very strong connection with a minimum weakening of the shroud. Under some conditions the curved part of the tongue and groove may be used to the practical exclusion of the straight part, and vice versa.

In the enlargements (Figs. 9 and 10, Sheet 1) the clearance between the extreme edge of the tongue and the bottom of the groove is marked 33. Its dimensions will, of course, vary with the metals used and the temperature to which the fan is to be subjected; but, having the coefficient of expansion of the metal and the forms of the parts, the clearance can easily be calculated to allow for the unavoidable expansion.

The tongues 30 should have a push fit in the grooves. They are here shown as the same width, and manufacturing tolerances should not prevent necessary movement or permit play.

The body of each blade 29 is generally flat, but towards the inner end each is curved at 34, as appears best in Fig. 8 (Sheet 1) and is provided with a segmental foot 35, lying at right angles to the main bodyof the blade and serving with the other feet to form a ring after the fashion of the-spokes in an artillery wheel. These feet 35, collectively, are gripped between flanges 36 at the inner ends of the spacers 24 and 25 and they are made fast by pins, each having a large middle portion 31 received in an opening in the foot 35, and reduced end portions 38 received in corresponding openings in the flanges 36.

In assembling such a fan the key I9 is placed in the keyway in the shaft H and the side piece B pressed over the shaft and moved into the positionshown in Fig. 3. The spacer 25 and the key 26 are next assembled with the shaft, then a complete set of blades 29, with the corresponding pins, are put in place, followed by the spacer 24, the side piece A and the key 2|, in order. finally, the plate 22 is made fast by the screws When the fan is put in operation a cooling fluid, such as water, is circulated through the hollow l5 of the shaft II, and as the furnace, or other device, approaches normal operation, the outer portion of the fan heats up to correspond with the gases being handled, while the inner portions remain relatively cool. That means that the hubs l6 to a large extent, the spokes I! to a decreasing extent, are cool as compzred with the blades 29 and the rims, or shrouds However, with the scheme of construction shown, the blades can expand without forcing the rims apart or otherwise causing any distortion in the side members, which likewise can expand according to the law of their being, the clearance 33 being always made sufficient to permit the necessary movement for the maximum expansion to be had in service for which the fan is designed.

The action of centrifugal force on the blades 29 is, in the main, resisted by the pins securing the feet 35 to the flanges 36. This fastening insures that the blades will be assembled in proper relation to the axis toprovide dynamic balance and willbe maintained in that relation as the fan heats up in service, or cools down after being in service.

By preference the spokes I! are designed as inlet vanes to propel the gas into the body of the fan. They are here shown cast in one piece with the hub 6 and the rim l8, but under some conditions it will be preferable to make them physically separate from the hub in order to avoid strains that would otherwise be set up.

The fan shown in Sheets 1 and 2 is for high capacity at high temperatures. It is 24" in diameter and 15 between the outer edges of the rims l8. The grooves 28 are A wide and the tongues are of equal thickness. The grooves are deep and the curved portions thereof are 1%" deep, being made with a 2%" cutter. The Woodruff key on the tongue is struck on a radius of 1 5 providing a clearance of The feet 35 of the blades are 25 thicker than the space between the flanges 36, and are therefore gripped tightly by the flanges.

The alloy found satisfactory for this construction up to 1600 F. consisted of chromium 25%, nickel 12%, and the remainder principally iron, with low carbon. But, of course, metal must be selected to suit the conditions of service.

Turning now to Sheet 3 of the drawings, there will be found a construction suitable for the same temperatures as the first form described, but having approximately half the capacity.

Only one wheel-like side piece 39 and one,

spacer "is used. On the left of the fan there is a disk-like side piece 4|, having a hub 42 and a rim 43 forming a shroud.

The blades 44 are interlocked with the shrouds in substantially the same way as described in connection with the double fan. Their inner portions 45, however, are curved somewhat differently and cut away at an angle to join segmental feet 46 at the extreme left. Those feet are assembled as before and made fast by pins 41, but in this instance instead of being gripped between the two flanges on spacers they are gripped between a flange 48 on the spacer 40 and the side piece 4|. As before, however, the feet are thicker by a few thousandths of an inch than the space allowed between the clamping parts.

In assembling this single fan, the key 49 is inserted in the keyway in the shaft 50 and the wheel-like side piece put in the position shown at the right in Fig. 11. Then the spacer 40 is slipped over the shaft and the key to its position, followed by the blades 44, the pins 41, and the side piece 4|, which is madev fast by'the collar 5| and the screw 52.

- Turning now to Sheets 4 and 5, there is shown a high capacity fan construction suitable for temperatures somewhat lower than that for which the first two forms are best adapted.

In Fig. 14'the side piecesC and D are like the side pieces A and B in Fig. 3, except at the inner sides of the shrouds l8, where it will be seen that the grooves 23 are intersected by curved grooves 53, milled into the inclined face of the shroud adjacent to its inner circumference. They receive curved keys 54 on the edges of the blades 55 which serve to make the blades fast against centrifugal forces tending to throw them bodily outwardly.

The inner ends 56 of the blades are curved as best shown in Fig. 15 and thereby given sufficient strength without any other support.

A specimen of this type of fan is 24" in diameter -3" between the outsides .of the rim l8. The grooves .53 were made with a milling cutter 1 /2" radius and the clearance between the bottom of the groove and the curved surface of the sinking at 60.

key was Y3", the sides of each key 54 having a .push-fit in the grooves 53. The mode of assem- In Figs. 18, 19, is shown a form of key that is very satisfactory in place of the curved keys 56. In this instance the edges of the fan blades are provided with integral rounded pins 57, having axes, parallel to the axis of rotation, and their outer ends 58 are machined to make a push fit with sockets 59, drilled or bored in the shrouds I8. When the shrouds are at an angle as shown, it is necessary to provide a slight coring or counter- The clearances in this case are substantially the same as in the form for which it is an alternative.

By making the blades fast in either of these ways the outer portion expands outwardly and the inner portion expands inwardly with respect to the fastening keys or pins. The location of the fastening with respect to the circumference of the shroud is somewhat a matter of choice, but as a rule the fastening should be located to.- wards the axis of rotationrather than towards the outer circumference. of the fan wheel, al though under some conditions the'fastening may be made adjacent to or at the circumference of the shroud, thereby forcing most of the expansion to take place inwardly.

Under some conditions of service the inner ends of the fan blades can be made fast bytap bolts, as shown at 6| in Figs. 20 and 21, in which case the blades 62 will have flat feet 63 arranged -to rest upon a cylindrical flange 64, on a spacer, or hub, attached to the shaft,

With the present scheme of fan construction the parts can be machined, finished and annealed at temperatures above those expected in service.

They can then be assembled free from any internal strains whatever and with provision made for unavoidable expansion. As the fan heats up the clearances will diminish and when approximately the normal temperature of service ,is reached the parts will-be tightly fitted together, but without distortion. The freedom allowed the parts in their expansion insures that the enlargement will be in such a way as not to disturb the dynamic'balance of the fan. i

.In prior constructions where the blades an shrouds are secured together by riveting and such like, the parts have been put under initial strains which remained after the fan had been adjusted for balance. Then upon putting the fan in servthe balance was determined, thus disturbing the dynamic balance and setting up stresses that grew until the material failed. Prior fans made in one piece have also failed in high temperature service due to distortion.

The possible forms that will ,embody the pres-.

and in applying the invention, others will change the form to suit conditions and preference.

The same shapes can be used forthe wheellike members in all the forms shown. The tongue andgroove connections shown have the advantage that they make it possible to machine the parts on the inner side of the shroud and in the majority of cases obtain perfect balance without adding or cutting away any metal for that purpose. a

The scheme of construction can be used in fans made of steel and such like working at temperatures around 900 F. or below, but this scheme offers the greatest advantage in fans operating at higher temperatures and requiring the use of heat resisting alloys of some kind. Of course, in each instance the alloy will be chosen to suit the temperatures and the corrosive or abrasive conditions with which the parts must-cope.

' When the shaft is cooled it need not be made of alloy; and making the spacers separate from the side pieces renders it possible to use cheaper material for the spacers than that required for the side pieces and blades.

The parts should have a drive fit or a press fit on the shaft. The heads of the keys should be undercut as shown at 65 in Figs. 3 and 14, especially when the shaft is cooled, thus when the parts heat up (which take hours or days) ,the lengthwise expansion of the hub deforms the head of the key and makes the shoulder approximately the same as the end of the hub. Without some such allowance for expansion the head of the key is likely to be broken ofi.

This application is a continuation in part of my applications, Serial No. 178,985, filed December 9, 1937, and Serial No.194,648, filed March 8, 1938.

I claim as my invention:

1. A fan blade comprising a fiat outer portion, a curved inner portion and a segmental securing foot portion at right angles to the fiat portion.

2. In a fan, a shaft, an open and a closed side piece fast on the shaft, each side piece having a peripheral shroud portion spaced axially from the other, blades extending between the shroud portions, tongue and groove joints between the edges of the blades and the shroud portions with clearance for expansion, and means fastening the inner ends of the blades against outward bodily movement with respect to the side pieces formed in a ring about the axis of rotation.

3. In a fan, a shaft, an open and a closed side piece fast on the shaft, each side piece having a peripheral shroud portion spaced axially from the other, blades extending between the shroud portions and having their edges'joined to the shrouds for normal rotation together and movement relative. to the shrouds in expanding and contracting, and meansfastening the inner ends of the blades to the inner portion of the closed side piece to hold said blades against outward bodily movement with respect to said side piece.

.4. In a fan, a shaft, side pieces having hubs fixed against relative movement on the shaft, and

having shrouds spaced apart lengthwise to the shaft, at least one of the side pieces having an inlet opening about the shaft within the shroud, blades each separately mounted between the shrouds and having its respective edges interlocked with the shrouds for normal rotation with them but capable of. appreciable movement relative to the shrouds in expanding and contracting through a considerable range of temperature, and

means securing the bladesagainst centrifugal blades each Separately mounted between the shrouds and having its respective edges interlocked with the shrouds for normal rotation with them but capable of appreciable movement relative to the shrouds in expanding andcontracting I tening the corresponding blade against centrif-- through a considerable range of temperature, andmeans remote from the outer periphery of the shrouds securing'the blades against centrifugal movement, whereby dynamic balance is maintained.

6. In a fan, a shaft, side pieces having hubs fixed against relative movement on the shaft and having-shrouds spacedapart lengthwise to the shaft, at least one of the side pieces having an inlet opening about the shaft within the shroud, blades each separately mounted between the shrouds and having its respective edges interlocked with the shrouds for normal rotation with them but capable of. appreciable movement inwardly and outwardly and axially relative to the shrouds in expanding and contracting through a considerable range of temperature, and means securing the blades against centrifugal movement, whereby dynamic balance is maintained.

7. Ina fan, a cooled shaft, side pieces having hubs fixed against relative movement on the shaft and having shrouds spaced apart length-.

wise to the shaft, at least one of the side pieces having an inlet opening about the shaft within the shroud, blades each separately mounted be-' tween the shrouds and having its respective edges interlocked with the shrouds for normal rotation with them but capable of appreciable movement relative to the shrouds in expanding and contracting through a considerable range of temperature, and means securing the blades against centrifugal movement, whereby dynamic balance tive to the shrouds in expanding and contracting through a considerable range of temperature, and .keys fastening the blades to the side pieces to hold the blades against bodily movementloutwardly and permit expansion and contraction inwardly and outwardly of said keys, whereby dynamic balance is maintained.

9. In a fan, a shaft, side pieces having hubs fixed against relative movement on the shaft and having shrouds spaced apart lengthwise to the shaft, at least one of the side pieces having an inlet opening about the shaft within. the shroud, and blades each separately mounted between the shrouds and having its respective edges interlocked with the shrouds for normal rotation with them but capable of appreciable-movement relative to the shrouds in expanding and contracting through a considerable range of temperature, the interlocking means including surfaces curved like Woodrufi keys, whereby dynamic balance is maintained.

10. In a fan, a shaft, side pieces having hubs fixed against relative movement on the shaft and blades each separately mounted between the shrouds and having its respective edges interlocked with the shrouds for normal rotation with them but capable of appreciable movement rela tive to the shrouds in expanding and contracting through a considerable range of temperature, and means in the general plane of each interlock fashaving shrouds spaced apart lengthwise to the shaft, at least one of the side pieces having an inlet opening about the. shaft within the shroud,

blades .each separately .mounted between the shrouds and having its respective edges interlocked with the shrouds for normal rotation with them but capable of appreciable movement relative to the shrouds in expanding and contracting through a considerable range of temperature, and means securingthe blades to the side pieces to prevent centrifugal movement of the blades,

whereby dynamic balance is maintained.

12. In a fan; a shaft, side pieces having hubs fixed against relative movement'on the shaft and having'shrouds spaced apart lengthwise to the shaft, at least one of the side pieceshaving an inlet opening about the shaft within the shroud, blades each separately mounted between the shrouds and having its'respective edges interlocked with the shrouds for normal rotation with them but capable of appreciable movement rela-' tive to the shrouds in expanding and contracting through a considerable range of temperature, the inner end of each blade having a segmental foot, and means fastening the segmental feet in a ring-like arrangement about the axis of rotation. 13. In a fan, a shaft, side pieces having hubs fixed against relative movement on the shaft and having shrouds spaced apart lengthwise to the inlet opening about the shaft'withinthe shroud, blades each separately mounted between the shrouds and having its respective edges interlocked with the shrouds for normal rotation with them but capable of appreciable movement relative to the shrouds in expanding and contracting through a,corisiderable range of temperature-and fastening means for the blades to hold them against centrifugal movement-comprising a pin shrouds and having its respective edges interlocked with the shrouds for normal rotation with them but capable of appreciable movement rela-' shaft, at least one of the side pieces having an tiveto the shrouds in expanding and contracting through a considerable range of temperature, and

fastening means for the blades to hold them against centrifugal movement, comprising pins blades each separately mounted between the shrouds and having its respective edges interlocked with the shrouds for normal rotation with them but capable of appreciable movement relative to the shrouds in expanding and contracting through a considerable range of temperature, the inner endof each blade having a segmental foot, and means fastening the feet in a ring-1ike arrangement about the axis of rotation comprising mating circular flanges gripping the segmental feet.

16. In a fan, a shaft, side pieces having hubs fixed against relative movement on the shaft and having shrouds spaced apart lengthwise to the FRANCIS C. WILLIAMS.

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