US2553987A

US2553987A - Gyratory crusher

Info

Publication number: US2553987A
Application number: US712841A
Authority: US
Inventors: Robert W Stevens
Original assignee: Dominion Engineering Works Ltd
Current assignee: Dominion Engineering Works Ltd
Priority date: 1946-11-29
Filing date: 1946-11-29
Publication date: 1951-05-22
Anticipated expiration: 1968-05-22

Description

R. W. STEVENS GYRATORY CRUSHER May 22, 1951 5 Sheets-Sheet 1 Filed Nov. 29, 1946 3 S. 8 2 2 .2 E g .8. a Q. mm m m Mm: m w m 2: M .u 3. 8w 9" a. a B a m Own hm QM v2 E k 0m 22 "mom i a Q mm 0 25 i .q o. 2 QM 1 O mu m 2 M @m 3 5 mm @m 3 a 6 k m x mm s W2 3 mi M R R mm a .2 K E 3 2; 5.x mu 2.

All R INVENTOR R.W-STEVENS A'IfijEYS Patented May 22, 1951 UNITED STATES PAT ENT OFFICE GYRATQRY CRUSHER Robert W. Stevens, Montreal, Quebec, Canada,

assignor to Dominion Engineering Works Limited, Lachine, Quebec, Canada Application November 29, 1 946, -Serial No.' 712,841

4 Claims. (01. 241-215) 'This invention 'rela'tes'to'improvements in gymtbry Crushers in which the crusher-head is gyr'ated by rotation of an eccentric comprising fa cylindrical member rotatabl y 'jou'r nalled in the frame structure of the crusher and provided with an inclined shaft-receiving bore in which the crusher-head shaft is rotatably jo'iir n'alled.

According to one feature of this invention, the crusher-head and eccentric are supported by an improved arrangement -'of thrust-bearings comprising an eccentric supporting thrust-bearing interposed between a downwardly facing bearing "surface at the upper port-ionof theeccentric and an opposing upwardly facing bearing surf-ace of the frame structure; and asecond 'crusher head supporting 't hrust b'earing interposed between an upwardly facing bearing surface provided at the upper portion of the eccentric and an opposing downwardly facing bearin surface of the crusher-head.

Y Another feature of the "inventione'onsists in the provision of an improved lubricating system including provision for flooding said thrustbear gs with oil when the crusher is in operatrio and meshing with "a pinion carried by a drive shaft journalled in said name structure, the location of the gear at the lowerend of th'eeccentri'c making said gear easily accessible so that shims may conveniently be interposed between said gear and eccentric; when relative adjustment of the gear and pinion is necessary to ensure proper meshing thereof.

Another feature of the invention consists in collecting the overflow oil from saidthrust -bean ings in a sump provided with an opening through which the oil drops onto said gear and pinion while passing downwardly'to a lower sump located at the bottom'of the frame structure. v Another feature of the invention consists in the provision'of a novel arrangement of oil passages through which oil is fed to lubricate '(a') a hearing liner fitted in the inclined shaft-receiving pore-of the eccentric and (b) a bearin bushing by means :of which the eccentric is journal ed in said framestructure.

A further feature of the invention eonsistsfin the provision of a novel air seal arrangement for "the crusher-' head, the eccentric, and the portion of the frame structure "in which the eccentric is 'journ'alled.

Figure 3 is a viewsimilar t0 nigure'z bl'lt' shbwing certain modifications. v I

Figure 4 'iS a "sectional View aldng seetion'ime 4-4 (if Figure 3.

As shown in these drawings, the mam name structure of the crusher includes a generally cylindrical outer frame member 5 "provided, at

its lower end, with an outwardly directed -'1lange "B forming a square base which supports thecrusher on its foundations. Member '5 is connected, by radial vertical ribs"! and horizontal tubular memher 8, to a generally cylindrical intermediate frame member 9. The last mentioned member 9 is connected to an inner cylindrical frame member ID by horizontal ribs H and 'I2 and also by inward continuations 1a of vertical ribsl. Memher It] is bored to receive a bronze bearing [3.

An outwardly directed flange [4 'is provided at the upper end of member 5, This member is bored to receive a number of inserts i5 and carries a packing l6 fitted in groove ll. Locking studs I8 extend upwardly through inserts [5 in screw threaded engagement therewith. These locking studs are provided with non-circular "lower ends [9 so that they may be turned to jam "their upper ends against wearing rings 20 carried "packing I6 and is provided with a circular seri s of outwardly directed projections 25 These pro jections 25' are adapted to be engaged by a ringturning lever (not shown) which is removably fulcrumed in a fulcrum bearing 26 carried by a bracket 2'! which is bolted to frame member 5.

The inner cylindrical portion 23 of ring 2| is provided with a threaded section 29 engaging a correspondingly threaded section 39 of frame member 5. A packing 3| is arranged in groove 32 provided in frame member below threaded section 29 and engages the inner cylindrical portion 23 of ring 2| to exclude dust and foreign material from the interior of said ring. The inner cylindrical portion 23 of ring 2! also carries a plate steel liner 33 suitably fastened thereto A wear ring 35 is arranged on horizontal section 24 of adjusting ring 2| and supports the outwardly directed flange 36 of bowl member 31. Wear ring 35 presents a convex, toroidal bearing surface 35a engaging and supporting a complementary concave toroidal bearing surface 36a 'of bowl flange 36.

Flange 36 of bowl member 31 is yieldingly held down on wear ring 35 by the lower ends of compression springs 39 arranged in groups of three each. The outer springs 39 of each group encircle studs 40 which extend through holes 4| in flange 36 and holes 42 in wear ring 35 into tapped openings 43 provided in section 24 of ring 2|. The upper ends of the three springs of each held in place at its lower end by the upper portion of a dowel 49 having its lower portion screwed into a tapped hole 50 provided in adjusting ring 2 I The principal functions of dowel 49 are to guide bowl flange 3B and to hold the wear ring 35 down on adjusting ring 2|. In this connection it will be noted that each dowel is provided with a hold down flange 5!] countersunk in a recess 5| formed by enlarging the upper end of a dowel-receiving opening 52 provided in wear ring 35. It will also be noted that a conical portion 53 of each dowel located immediately above flange 5| is slidably fitted in a cornplementary conical bore provided in a hardened steel bushing insert 54 carried by bowl flange 36. Bowl 31 comprises three conical sections 55, 51 and 58 which are stiffened by a plurality of ribs 59 formed integral therewith. The bowl flange 36 is formed as a horizontal continuation of bowl section 58. The main bowl section 56 is a downwardly and outwardly flaring conical annulus having the lower portion of its inner surface machined to provide a seat 69 for the lower portion of the bowl liner 6| Bowl section 56 and liner 6| are designed to leave an intervening space which is filled with ductile metal Ela to provide a yieldable seat for the liner.

At each of a plurality of points around its circumference bowl 3! is cored out to provide a pocket 63 receiving therein a hook-shaped lug 33 projecting outwardly from bowl liner 6|. Each lug -64 is supported on the central portion of a U- bolts 65, the side legs of which extend upwardly through supporting bar 66 and are equipped with adjusting nuts 6'! bearing on washers 68 car- Y .4 ried by said bar. The ends of bar 66 rest on seats 69 provided at the upper edges of two ribs 59 between which the pocket 63 is formed. Each pocket 63 includes an outer dust excluding wall 19 which prevents dust passing upwardly through the pocket 63 into the spring housing hereinafter referred to.

A cover ll is preferably secured to bowl member 31 to provide a spring housing 12 enclosing the springs 39. This cover comprises an outer cylindrical portion 13 and an inner cylindrical portion 14 having their upper edges integrally joined to a horizontal connecting portion 15. The lower edge of the outer portion 13 of cover H is fastened to the outer periphery of bowl flange 36 by cap screws 16. The lower edge of the inner cylindrical portion 13 of cover 1| is supported on a seat 11 provided at the upper edge of bowl section 51.

The conical section 51 of bowl 31 is an upwardly and outwardly flaring section which provides a hopper from which the material to be crushed is fed into the crushing zone A between the bowl liner GI and the crusher head assembly generally indicated at 62. A suitable onepiece lining 18 is preferably arranged on the upper surface of the hopper section 51 of bowl 31 so that the lower edge of hopper lining 18 overlies the upper edge of bowl lining 6|.

When cover H is used the inner cylindrical portion 14 thereof forms a cylindrical side wall extension of the hopper provided by bowl section 51 and is preferably equipped with a removable liner 19.

The portion of cylindrical frame member 9 which extends above horizontal rib H is expanded outwardly to form a larger cylindrical portion 9a which is machined to form the bottom wall and inner side wall 8| of an annular air chamber 82. The top wall 83 and outer side wall 84 of air chamber 82 (see Fig. 2) are formed by machined surfaces of an air chamber ring 35. Air is admitted to air chamber 82 through a horizontal air inlet bore 81 provided in tubu lar frame member 8 and connecting vertical bore 88 provided in frame member 9. A cover 89 is fastened to the lower end of frame member 9 by bolts 90.

Tubular frame member 8 is bored to receive pinion shaft housing 9| and is also tapped to receive the shaft housing fastening bolts 92. A pinion shaft 93 extends inwardly through housing 9| and has a bevel pinion 94 fixed to its inner end. This pinion drives a bevel gear 95 which is fastened by bolts 96 to the lower end of an eccentric 91 journalled in the bronze bearing I3 fitted in frame member ID. Gear 95 is spaced from the lower portion of frame member H) to provide an intervening oil passage 98. Gear 95 is also provided with central oil hole 99 to which oil is delivered through central oil inlet opening I provided in cover 89. The hole 99 in gear is surrounded by a depending annular wall |0| which extends downwardly with an an nular wall I02 rising from cover 89. A suitable oil seal I03 is interposed between annular walls HH and I92 to force the oil supplied to oil inlet opening I99 to flow upwardly through the oil hole 99 whence it is distributed as hereinafter described.

That portion of eccentric 9'! which is journalled in bearing l3 is a cylinder on axis A and is provided with an inclined conical shaft receiving bore 194 on axis A which makes a small angle thrust bearings. :surface :.I 'I 2 :is perpendicular to :axis .A' 'while the .dicularto axis A "tioned between and .in "spaced relation to outer and inner oil-retaining :lips 113a -and 11:31; aproring 35 extends into agroove I I'I.

surface crusher head is machined to provide .a;seat I35 The -porvtions'of crusher head I29 and mantle 136 which lie above seat I35 are designed to :leavean inmessages? expanded toiprovide atfiange-like portion including :a -central .section 1:99 :and =.a :rim section H ronneicted to central section EH39 by a::p1urality of connecting ribs III. The r-central section 5199 is machined to providebearing surfaces III 2 and H3 :for "hearing pads .I I4 and I I5 which. serve :aS The downwardly facing bearing upwardly .facing bearing surface I13 iis per-pen- Bearing pads =Ii-I:3 rare 1-posi :jecting upwardly from bearing. surface 1H3. :An-

.nular grooves 'I I1! and Isl '8 are machined in the underside of rim section I09 of eccentric :91.

These grooves are machined foncaxis .A. "An upwardly directed projection 119 :of "an air chamber A similar upwardly directed projection -I .oicylindrica'l :portion 9a of frame member 19 extends into groove H8. The grooves Ill and H8 serve,r':incon'jun'ction with the projections H9 and I20, :to form a labyrinth IIZI. Suitably placed holes 185a :are

provided :in ring 85 to :allow :passage ofair from air chamber 82to labyrinth .I 21

. The upper portion of rim :section III] of -:eccentric 197i :is machined on axis A to provide labyrinth formingportions I23, I24 and 'I25zma-ting with complementarymachine'd portions 1125, I27 and .628 .of a conical 'crusher head 1:29 'to provide a secondlabyrinthlitll. A series'of holes I3I ar drilledin rim portion III? of eccentric '9'I to provide for passage of air from the lower labyrinth IZI to'the upperzlabyrinth 133.

The lower portion of crusher head I29 .15 machined to providegroove I33 :in which the upper bearing pads H5 are fitted. The-bottom 'wall of groove I33 provides a downwardly facing .bearing surface opposing the upwardly facing bearing H3. The outer conical surface of the for the manganese steel mantle "I36.

tervening space which is filled with "ductile. metal I31, such as zinc, to provide :ayyieldableiseat :for

the mantle.

Cylindrical shaft bores I39 and 1I4il are provided in crusher head I29 to receive :the upper portion of crusher .headshaft MI. The portion of shaft [4| which extends downwardly ifrom crusher-head I29 is conicalandis fitted in conical .liner I95 of eccentric 91 so that the crusher head is aligned with axis A Mantle 136 is held ,firmlyagainst crusher head I29 by a nut M2on the upper end of shaft III, the pressure of the nut being transmitted to the mantle through sleeve M3.

The upper portion of nut M2 is formed with inside vertical grooves M5 to provide for insertion of a suitable wrench for initial tightening. The upper end of nut I 42 is also expanded to provide a supporting flange I46 to'which a 'feed distributing plate I4! is fastened by bolts I48.

The eccentric 9.! and crusher head I29 are-supported by the lower bearing pads H4 which are fitted in groove I50 provided in horizontal frame portion I5I extending between-the expanded 'por-- tion 9a of frame member "9 and the upper portion of frame member Ill. The bottom wall of groove I'5I provides an upwardly facing bearing surface, opposing the downwardly facing bearing .and seal I6 I,

surface 442. Bearing pads H4 are positioned Reverting to the previously mentioned crush- I ingzoneA-it will be noted that the "outer andininer walls of this zone are .formed, respectively,

. by the bowl liner 6 I and the crushing :head'mantle'or liner I36. Beginning at the lowerend of the crushing 'zone these liners are arranged to provide a parallel section I66 when they are in apositionrof closest approach. Above this parallel section the crushing :zone widens outby reason of the fact thatoneof the .liners is built in a series -of conical steps I31, I68 and I69, -the angle between the-conical sections of the liners at the top being not larger than that which will nip-the rock to be crushed without forcing iitfrom the crushing zone.

The bore I94 -of-eccentr-ic '91 is provided with .anoil groove I88 (see Fig. 4) extending from the .lower end of the bore to a radial opening I82 and with a second oil groove I8I diametrically opposite extending to the upperend of said here. Opening I82 extendsradiallyfrom bore N14 to the outer surfaceof the eccentric. Grooves I and .I BI are covered by liner I I35.

Ho'les I84 are drilled'radially inbronze'bearing liner IE5 "to allow oil to pass from groove I80t0 lubricate this bearing. Similarly, holes I85 :are :drilled radiallyin the eccentric to meet groove Iii-I and "allow oil to ,passfrom this groove to Inbricateibronze-bearing l3. 7

A pocket I55 .is provided at the inner end of pinion shaft housing 9i to :pick up oil and lead -.-it to-the combined radial and thrust bronzeb'earings I51 and I58. If desired, the bearings I51 and --I 58 may bereplaced by anti-friction bearings which take care of both-radial and thrust loads. .The end cover I69 of shaft housing Si :is'provi'd'ed with a seal :I 6 I and a seal cover I52.

.Poweris transmitted topinion shaft 93 through a coupling (not .shown) which is fitted on the :shaft so that it is presseda'gainst'a spacer sleeve I63 extending outwardly through end cover I63 Pinion 9:3 is pressed on shaft'93 and held against endwise displacement by'retaining plate I 64 which is held in place by' cap screws (not shown) Operation Rotation of pinion shaft 93 by an electric motor -;or other prime mover serves to rotate eccentric 97 about axis A through the agency of pinion 94 and gear .95. This rotation :of eccentric 91 im- 1, parts a conical motion to crusher head shaft MI and gyrates the crusher head I29. The crusher head must be free to rotate about axis A independently of eccentric s7 and this is provided for by the fitting of the conical portion of shaft MI in the-'conicalbearing liner I 95 of eccentric 91.

Lubrication Oil is pumped to central oil inlet opening I00 provided in cover 39- and is directed through oil hole '99 of soaring 95 by the constraining effect of oil seal I113. The oil is then free to divide itself between 0-11 grooves H35 and NH in bore IIM of eccentric 91 (see :Fig. 4). Oil following oil groove I80 of eccentric 9! passes outwardly through radial openings I82 to flood the lower b'earing pad I'M. Oil following the oil groove I"=8I of-eccentric 9'! floods the upper'surilace of the eccentric to lubricate the upper bearing pad I15.

The oil which floods the thrust bearing pads I I4 and I I5 is thrown downwardly and outwardly into an oil sump I68 which lies in the upper part of the central section of the frame structure and is bounded by the horizontal frame portion I5I, the upper portions of the frame members '8 and 9 and the horizontal rib I I. The upper horizontal frame portion I 5I is provided with openings I5Ia through which the oil passes. The rib II forming the bottom wall of the oil sump I68 is provided with an opening I8? through which oil drops, passing along wall I88 and onto bevel gear 95 at the point where it meshes with bevel pinion 94, to be thrown outwardly, a large portion of it passing through the gear mesh.

Rib I I is also provided with a small opening I89 through which a small quantity of oil passes to collect in pocket I56 whence it is led to the pinion shaft bearings. Suitable arrangements are made to return oil from these hearings to sump I III or, alternately, direct to external sump (not shown). Oil thrown outwardly by the gear falls into sump I'IU formed in cover 89 from which it is removed through hole III.

In the modified arrangement shown in Figures 3 and 4, the bottom cover 89 of the frame is formed with a relatively large opening 39a normally closed by relatively light auxiliary cover I15. In this case the openings I90 and III are formed in the auxiliary cover I'I5 which also carries the parts I62 and I03. The main cover 89 is formed with an upstanding annular wall I16 surrounding opening 89a and with ribs III extending outwardly from said wall. The wall "6 is provided with oil holes IIB through which oil enters sump I 7!} from the oil spaces provided between adjacent ribs I'I'I. Ribs I'I'I will stop any swirl caused by the rotating gear.

The advantage of the double cover arrangement shown in Figures 3 and 4 is that the removal of the light auxilary cover [75 enables the eccentric 9? to be detached from gear 95 and removed for examination or replacement without removing the gear 95 which is too heavy for man handling. When cover I15 and the gear fastening bolts 96 are removed, the gear 95 will be supported and retained in position for re-attachment to the cocentric by the gear supporting annular wall I16 of main cover 89.

Some of the excess oil from hearing I 3 will join the oil flowing from passage I82 to the lower bearing pad and some of such excess oil will drop onto gear 95.

An external oil sump (not shown) is provided for collecting and, if necessary, cooling the oil. The oil is led to this sump by suitable piping including a pipe (not shown) connected to an oil hole III in the bottom wall of oil sump I and a second piping (not shown) connected to an oil hole I72 provided at the outer end of the pinion shaft housing 9 I.

In order to protect the bearings H4 and I I5 from starting without oil, means are provided for retaining a pool of oil at the contacting surfaces after the oil pump is shut off. This is accomplished by means of the oil retaining lips I I 3a and I I31) arranged at opposite sides of the upper bearing pad H5 and the oil retaining lips I52 and I 53 provided at opposite sides of the lower bearing pad II4.

The oil pump will preferably be driven separate 1y from the main motor (not shown) but will be interlocked with the main motor in such a way as to start before the main motor and to run for a short time after the main motor is shut off.

Seal

As previously noted, air under suitable pressure is forced through the air inlet bores 81 and 88 into air chamber 82 from whence it passes into labyrinth I2I through holes 85a and from labyrinth I2I through holes I3I into the upper labyrinth I30. In this way air pressure is maintained in the air chamber 82 and in the labyrinthine air passages so that there will be arconstant flow of air outwardly and inwardly from said air chamber through passages, the outward flow providing protection against dust and the inward flow toward the sump I68 tending to prevent the entrance of oil to these passages. A suitably placed and protected air vent (not shown) is provided to permit the air to flow freely out of the sump.

Having thus described the important characteristics of my invention and a preferred embodiment thereof, it will be understood that various modifications may be resorted to within the scope and spirit of the invention as defined by the appended claims.

I claim:

1. In a gyratory crusher of the kind described, a stationary vertically extending frame member provided with a vertical cylindrical bore, a horizontal frame member surrounding and integrally joined to the upper end of said vertical frame member, said horizontal frame member presenting an upward facing bearing surface bounded on its outer side by an integral upwardly projecting oil retaining lip, a bearing sleeve fitted in the bore of said vertical frame member with the upper end of the bearing sleeve projecting above said bore to provide an oil retaining lip at the inner side of said bearing surface, a verticall disposed eccentric rotatably journalled in said bearing sleeve, said eccentric comprising a cylindrical member provided with a shaft receiving bore having an axis which is inclined to intersect the cen tral vertical axis of the eccentric at a point above the latter, a crusher head shaft journalled in and projecting above the bore of said eccentric, a crushes head rigidly secured to the upper end of said shaft in co-axial relation therewith, an integral flange projecting outwardly from the upper portion of said eccentric in spaced relation to said upwardly facing bearing surface and the bottom of said crusher head, said flange presenting downwardly and upwardly facing bearing surfaces, the downwardly facing bearing surface of the flange being perpendicular to the central axis of the eccentric and the upwardly facing bearing surface of said flange being perpendicular to the inclined axis of said shaft receiving bore and. being bounded at its inner and outer sides by integral upwardly projecting oil retaining lips, a thrust bearing interposed between the downwardly facing bearing surface of said flange and. the upwardly facing bearing surface of the horizontal frame member, a second thrust bearing interposed between the upwardly facing bearing surface of said flange and a downwardly facing bearing surface of said crusher head, said eccentric being provided with oil passages through which, oil is conducted to and over the upper edges of the inner oil retaining lips bordering the inner sides of the upwardly facing bearing surface of said flange and said horizontal frame member and means for rotating said eccentric.

2. In a gyratory crusher of the kind described, a stationary vertically extending frame member provided with a vertical cylindrical bore, a horizontal frame member surrounding and integrally joined to the upper end of said vertical frame member, said horizontal frame member present ing an upwardly facing bearing surface bounded on its outer side by an integral upwardly projecting oil retaining lip, a bearing sleeve fitted in the bore of said vertical fram member with the upper end of the bearing sleeve projecting above said bore to provide an oil retaining lip at the inner side of said bearing surface, a vertically disposed eccentric rotatably journalled in said bearing sleeve, said eccentric comprising a cylindrical member provided with a shaft receiving bore having an axis which is inclined to intersect the central vertical axis of the eccentric at a point above the latter, a crusher head shaft journalled in and projecting above the bore of said eccentric, a crusher head rigidly secured to the upper end of said shaft in co-axial relation therewith, an integral flange projecting outwardly from the upper portion of said eccentric in spaced relation to said upwardly facing bearing surface and the bottom of said crusher head, said flange presenting downwardly and upwardly facing bearing surfaces, the downwardly facing bearing surface of the flange being perpendicular to the central axis of the eccentric and th upwardly facing bearing surface of said flange being perpendicular to the inclined axis of said shaft receiving bore and being bounded at its inner and outer sides by integral upwardly projecting oil retaining lips, a thrust bearing interposed between the downwardly facing bearing surface of said flange and the upwardly facing bearing surface of the horizontal frame member, a second thrust bearing interposed between the upwardly facing bearing surface of said flange and a downwardly facing bearing surface of said crusher head, the bore defining wall of said eccentric being provided with a vertical groove through which oil is fed to and over the upper edge of the oil retaining lip bordering the inner side of the upwardly facing bearing surface of said flange and with a second vertical groove through which oil is delivered to an intermediate radial passage of the eccentric which delivers the oil to and over the upper edge of the oil retaining lip provided by the upper end of said bearing sleeve, and means for rotating said eccentric.

3. A gyratory crusher as set forth in claim 1,

including a second vertical frame member surrounding and spaced from the first mentioned vertical frame member and having its upper portion integrally joined to the outer portion of said horizontal frame member, and a horizontal web connecting the vertical frame members below the horizontal frame member and forming the bottom wall of an oil sump having its side walls 10 rounding and spaced from the first mentioned vertical frame member and having its upper portion integrally joined to the outer portion of said horizontal frame member, and a horizontal web connecting the vertical frame members below the horizontal frame member and forming the bottom wall of an oil sump having its side walls formed by portions of the vertical frame members extending above said web and having its top wall formed by said horizontal frame member, the last mentioned frame member and the flange of said eccentric being provided with vertical oil openings through which oil overflow ing the outer oil retaining lips bordering the upwardly facing bearing surfaces of said flange and said horizontal frame member is delivered to said sump, the second mentioned vertical frame member including an air chamber extending around the upper portion thereof, said air chamber including a top wall having air discharge openings bounded by upwardly directed projections extending into downwardly facing grooves in the outer portion of the eccentric flange and forming, with the walls of said grooves, a labyrinthian air passage open at its outer side to the atmosphere and at its inner side to said sump, the said outer portion of the eccentric flange and the bottom portion of the crusher head being formed with interfltting parts defining a second labyrinthian air passage open at its outer side to the atmosphere and at its inner side to the oil passages of said flange, said outer portion of the flange being also provided with vertical air ports connecting the aforesaid labyrinthian air passages and means for supplying air under pressure to said air chamber for delivery to the labyrinthian air passages through the top openings of the air chamber and the air ports of said flange.

ROBERT W. STEVENS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 19,538 Rumpel Apr. 16, 1935 1,031,083 Newhouse July 2, 1912 1,083,283 Kelly Jan. 6, 1914 1,436,338 Carman Nov. 21, 1922 1,553,202 Symons Sept. 8, 1925 1,575,874 Symons Mar. 9, 1926 1,691,553 Rumpel Nov. 13, 1928 1,863,529 Symons June 14, 1932 1,945,791 Rumpel Feb. 6, 1934 1,960,980 Rumpel May 29, 1934 1,993,900 Rumpel Mar. 12, 1935 2,000,385 Gruender May 7, 1935 2,017,108 Symons Oct. 15, 1935 2,054,326 Jacobson Sept. 15, 1936 2,066,281 Traylor et al. Dec. 29, 1936 2,079,882 Traylor May 11, 1937 2,231,491 Bousman Feb. 11, 1941 2,359,987 Gruender Oct. 10, 1944 FOREIGN PATENTS Number Country Date 66,645 Norway Aug. 16, 1943