US2681208A - Sealing means for rotary air preheaters - Google Patents

Description

G. K. w. BoEsTAD ET Al. 2,681,208 SEALING MEANS FOR ROTARY AIR PREHEATERS June 15 1954 Filed Dec. 28, 1948 6 Sheets-Sheet l y /W w June 15, 1954 G. K. w. BoEsTAD ETAL 2,681,208

SEALING MEANS FOR ROTARY AIR PREHEATERS 6 Sheets-Sheet 2 Filed Dec. 28, 1948 E nr@ June 15, 1954 G. K. W. BoEs'rAD ET AL 2,681,208

v SEALING MEANS FOR ROTARY AIR PREHEATERS Filed Deck. 28, 1948 6 Sheets-Sheet 5 G. K. w. BoEsTAD ETAL 2,681,208 SEALING MEANS FOR ROTARY AIR PREHEATERS Jlune 15, 1954 6 Sheets-Sheet 4 Filed Dec. 28, 1948 Fig-1D June 15, 1954 G. K. w. BoEsTAD ETAL 2,681,208

SEALING MEANS FoR ROTARY AIR PREHEATERS 6 Sheets-Sheet 5 Fia-l? Filed Dec. 28 1948 zo 1 v @a Fig-1E June l5, 1954 G. K. w. Bol-:STAD ET AL 2,581,208

SEALING MEANS FOR ROTARY AIR PREHEATERS 6 Sheets-Sheet 6 Filed Deo. 28,- 1948 l sequent short life.

Patented June 15, 1954 SEALING MEANS FOR ROTARY AIR PREHEATERS Gustav Karl William Boestad, Lidingo, and Per Walther Sigvard assignors, by Marble, New York,

meSIle a Persson, Stockholm, Sweden, ssignments, to Jarvis C. N. Y., Leslie M. Merrill,

Westfield, N. J., and Percy H. Batten, Racine,

Wis., as trustees Application December 28, 1948, Serial No. 67,726

Claims priority, application Sweden December 30, 1947 36 Claims.

The present invention relates to regenerative preheaters and especially to preheaters of the so-called Ljungstrm type. rIhis type of preheater has a cylindrical rotor divided into sectors which are filled by heat transferring plates, said plates upon rotation of the rotor rst accumulating heat from the hot gases and then, after entering the air side, delivering the accumulated heat to the air. The rotor is surrounded by an outer shell with two end plates, generally called sector plates, provided with openings for permitting the flow of gas and air into and from the preheater. In order to prevent undue leakage now between the air and gas sidesv the rotor usually has been provided with radial as well as peripheral seals, bearing against the sectorplates or any other suitable part of the stationary casing.

Earlier designs of such seals have generally been made as elastic elements of thin plates or the like, which by iiexible bending maintain .the sealing contact at all times or sometimes as rigid sealing elements, which by means of springs or the like are pressed against the surfaces against which sealing contact is desired.

In practice, however, it has proved impossible by using ilexible sealing elements to maintain the sealing edges suiciently flexible and at the same time strong enough to resist the stresses occurring for instance during soot-blowing operations, The rigid sealing elements movable by means of springs have shown the defect that their proper operation is lost after a short time on account of deposits from the gas in the form of soot, ash and tar-like compositions, such deposits occurring not only between the sealing surfaces but also between the different parts of the seal arrangement itself, resulting in lost sealing capability. Be-

cause of the uneven temperature distribution i prevailing in the preheater, the devices supporting the sealing elements have shown a tendency to distort whereby the elements are separated from the sealing surfaces. By overdimensioning the springs inv order to overcome every conceivable disturbance of the kind mentioned above and always secure the sealing elements in sealing position the resulting high surface pressures cause excessive wear of the sliding surfaces and con- Besides, the motor driving the rotor must be bigger due to the higher power consumption.

The sealing arrangement according to this invention consists of short elements of the rigid type, which, however, contrary to the previous designs, are connected to the rotor or the casing by means of a tilt-attachment giving swinging mobility to the elements. The pressure between the elements and the sealed preheater' parts may be obtained by fluid pressure diierence prevailing between the different sides of the sealing line. In this way the specic surface pressure is kept as low as possible and the wear between the sealing surfaces will be small. In certain cases an increase of the contact pressure by means of springs or counterweights which simultaneously hold the sealing elements in position is of value, especially in the case of low pressure differences or if complete sealing is desired also on the cold air side.

The seals can either be double-acting or singleacting. In the first case complete sealing is obtained independently of the location of the sealing element, whether on the air or on the gas side of the preheater. When using single-acting seals, on the other hand, complete sealing is obtained only for one of the two sides.

In the following the invention will be more fully described in detail with reference to the drawings, which by way of example show some preferred embodiments of the invention.

Fig. 1 shows in cross-section, a rotary preheater provided with seals according to the invention. The section is taken along line I-I of Fig. 2.

, Fig. 2 is a top plan view, broken away in part and with certain elements omitted for the sake oi clarity, of the apparatus shown in Fig. 1.

Figs. 3-20' show different types of sealing arrangements. i

In Figs. 1 and 2, the reference numeral it indicates the shell or casing of a preheater with end or sector plates l2 and. I4 respectively, which are provided with openings. IE and I8 for gas and openings 20 and 22 for air flowing through the rotor. The openings are framed by channel irons to give suitable connections to the air and gas channels. The rotor 24 consists of a rotor hub 28, radial partition walls 30 and an outer shell 32, forming a plurality of sectorsgenerally twelve-containing the heat transferring plates 26. Said plates generally consist of specially corrugated thin plates spaced from one another in such a manner that suitable channels for effective heat transfer are formed between the plates. The plates 25 are supported by radial rods 36 at the bottom of the sectors and, at least in biggerv preheaters the sectors have peripheral partition walls 33', reinforcing the rotor and simultaneously preventing undue radial movement of the heating plates. The bars L36 secure the plates 2E against axial movement. The whole rotor is carried by a shaft 42, supported in the axial bearing Mi, the casing of which is mounted in the frame work 43. The bearing 48 and the above mentioned bearing lis guide the rotor in radial direction. The preheater rotor is rotating slowly by means of a motor and a co-operating gearing indicated at 50.

Generally the preheater works with air and gas owing in counter-flow to obtain the highest possible efliciency. In the apparatus illustrated the arrow 52 indicates the direction of the gas iiow and the arrow 54 the direction of the air flow. Due to the pressure drop through the preheater and apparatus connected therewith a pressure difference will occur between the air and the gas side, so that the pressure is highest at the air inlet opening and lowest at the gas outlet opening. Leakage ow will thus take place between the rotor and the end plate i4 from the air inlet to the gas outlet as well as between the rotor and the end plate l2 from the air outlet to the gas inlet. A third leakage now takes place through the narrow space at the periphery of the rotor where air from the inlet opening enters the intermediate space i between the rotor and the stationary casing, this way flowing to the gas inlet and outlet as well as to the air outlet. In Figs. l and 2 the above mentioned two leakage flows occurring at the ends of the rotor are reduced by the radial seals 58 and 60 mounted ony the partition Walls 3D, and in a similar way the leakage iiow at the periphery is reduced by the peripheral seals 62 and M.

It is of importance to reduce these leakage ilows because high leakage loss means decreased preheater efciency and increased power consumption of the air and gas fans, and thus a decrease of the overall eciency of a power plant containing such preheaters.

Figs. 3 and 4 show a peripheral seal of the single-acting type with the sealing elements pressed against the sealing surface by the air pressure in the space 5%. On the rotor shell 32 there is riveted a ring 66 acting as a contact surface for the sealing elements 68. Each element is supported by a carrier plate 'i2 bolted to the plate I4.

The flange of each carrier 12 is provided with a suitable number of riveted pins I4- in the case illustrated two--tting in the corresponding holes TB of the sealing element which is made comparatively short with its edge along the ring 66 correspondingly curved and of bulbous crosssection whereas its opposite edge is straight as is also the flange of the carrier plate l2. The holes 'l0 for the carrier pins 'ifs widen in both directions from their central sections, a shape which allows a tilting of the elements in relation to the carrier plates and thus makes it possible for the elements to slide on the rotor ring E6, even if the rotor should be distorted due to uneven temperature stresses. The plate I6, welded to the carrier plate I2, serves as a stop preventing the sealing elements from leaving the sealing rings too far and enabling the air pressure to bring them back to sealing position.

The peripheral sealing arrangements shown in Figs. 5 and S consist of a number of element carriers 18 bolted to the sector plates I2 and i4 respectively whereas the sealing elements 68 are hinged on the carriers 18 by means of pins 'M according to the same principles as in the above described device. The spring Si) is guided by an arm B2 projecting from the holder 'H8 and presses the sealing element 68 against the rotor shell 32 with comparatively small force, while the excess pressure in the space 56 gives the essential force acting on the sealing elements of the gas side. On the cold air side the spring 8i) must also overcome the Whole pressure diiierence, counteracting the sealing pressure. The said seals may even be eliminated over this part of the periphery, the sealing effect in such case only being due to the sealing of the gas side. As in the above described arrangement the elements are characterized by a straight part at the element carriers but curved in accordance with the curvature of the rotor shell for the free sealing part.

Figs. '7-9 show another type of peripheral sealing elements 6B which are supported by the edge of the shell plate 32 of the rotor 2 in V-shaped grooves formed between each pair of abutments 84 projecting from the sealing elements. The elements are held inproper relation by means of a rod 86 and a spring 88, which connect an element in the upper sealing line with a suitable element in the lower seal. The rod 8E is movably mounted in the upper element by means of the two arms 96 and the cylindrical pin 92 and the spring 88 is correspondingly rotatably attached to the lower element. Even in this design it is of course possible to spring-load each element separately or to use weights without connecting the elements in pairs of above described.

In order to further reduce the leakage the sealing elements 68 are in this case provided with a groove QI at one end and with a flange 93 of corresponding shape and size at the other end so that an overlapping of the peripheral spaces between the elements is obtained.

Figs. l0 and l1 Show a peripheral sealing with the elements 58 supported by the V-shaped grooves formed between projections 84 extending from the elements which in turn are pressed against the flange 94 on the end plates l2 and Hl respectively due to the action of the spring 96. The latter acts between the arm S3 of the sealing element 68 and a hook l, fixed to the shell 32.

The peripheral seals shown in Figs. 12-13 consist of short sealing elements 68 provided with projections 84, forming V-shaped supports for the elements on the rotor shell 32, said elements being preferably kept in position against the edge of the rotor shell 32 by a resilient plate |02 bolted to the rotor. Depending on the side from which the higher pressure is acting, the sealing against the stationary casing H! occurs either at the upper end plate I2, or at a flange I0!! extending from the casing I0.

In Fig. 14 the curved sealing element 68 is kept in adjusted sealing position by a counter-weight |96 acting on a lever B08 which is rigidly connected to said element and passes through a bore in the rotor shell 32, in which bore the lever is tiltable. This type of seal is especially suitable for the upper peripheral seal.

For the lower seal it is not necessary to use a counter-weight as the weight of the element itself is suliicient for urging it to sealing position. Such an arrangement is shown in Fig. i5. The curved sealing element 558 in this case is movably connected to the rotor shell 32 by a bolt il!) which according to the illustrated design runs through a suitably formed bore in the sealing element itself.

In Fig. 16 there is shown a modiication of the device according to Figs. 14 and 15 which is adaptable for preheaters with horizontal axes of rotation. A spring H2 presses the sealing element 68 against the end plates I2 and Iii respectively. The spring is supported by an arm liti and a pin l lli fixed to the rotor shell 32, whereby the pin guides the spring which acts against a projection H8 on the sealing element.

I'he peripheral seal shown in Fig. 17 consists of a channel beam |20, fixed to the end plate I2, twol flat irons 22 and 25 bolted to the rotor, which flat irons likewise form a channel guide groove on the rotor shell 32, and the sealing elements 68 which are shaped as short dat irons of the same curvature as the rotor sh-ell and are inserted into the two channels. Depending on the influe ce of the air pressure the seals will seal against the flat iron E22 and the outer flange of the channel |26, or against the inner flange of` the same and the iron 24. It is of importance that the widti':v of the channels is not too small but permits .a certain inclination of the sealing elements without risk of seizing'.

In Fig. 18 the sealing elements 63 are fixed to the rotor by plate-like hooks l 26 acting as hinges. The counter-weight iii on the lever i021 is connected to the sealing element 68 and presses the same against the fiange 28, bolted to the end plate l2.

Figs. 19 and 20 show examples of double-acting seals mounted on the radial partition walls 35i, the direction of rotation being indicated by the arrow |255. The sector-formed parts of the end plates l2 and ifi are rounded or chamfered on that edge which the partition walls 3o meet when the rotor rotates, so that the curved sealing elements 535i and E32 easily can slide up on the sector plates l2 and it respectively. This action is also facilitated by the curved shoes i311, projecting from the leading elements 32. The upper sealing elements l3i and E32 are hinged on the common pin 138 in the same way as has already been described for the embodiment of Fig. 14, said pin being fixed to the radial partition wall to. The lower seals are correspondingly hinged to the partition walls according to the system shown in Fig. 15. It is obvious that either the elements ii or the elements |32 will seal independently of whether the rotor sectors turn from the air to the gas side or vice versa,

which means that the o'verpressure, acting on the sealing elements, changes direction.

As described above all embodiments according to the invention are based on the principle that the sealing elements are hinged in such a way that the mutual movement between the sealing means is in an arcuate path. At the same time, the seals are designed and mounted in such a way that they can be cleaned easily and thoroughly by air or steam jets.

We claim:

l. In a regenerative air preheater comprising two main parte, a first part providing stationary structure comprising a cylindrical casing and end plates having inlet and outlet openings for Ilow of gas and air respectively, the second part comprising a rotor mounted within said stationary structure and provided with radial partitions forming compartments with heat transfer material disposed in said compartments, sealing means between the periphery of said rotor and said stationary structure comprising a plurality or rigid sealing elements pivotally mounted on one of said parts in close proximity to each other to have rocking movement relative to both of said parts and forming a substantially continuous ring, a cooperating sealing surface on the other `of said parts with respect to which said sealing elements' have rocking movement, sealing means between said end plates and each of said radial partitions comprising a pair of rigid sealing members mounted on each side of each partition in opposed relation to rock in sealing contact with said end plates, and biasing means associated with certain of said sealing elements to urge the same into rocking contact with their associated sealing surfaces.

2. An apparatus as defined in claim 1 in which said biasing means comprises springs.

3. in apparatus as defined in claim 1 in which said biasing means comprises weights.

4. In a regenerative air preheater comprising two main parts, a rst part providing stationary structure comprising a cylindrical casing and end plates having inlet and outlet openings for flow of gas and air respectively, the second part comprising a rotor mounted within said stationary structure and provided with radial partitions forming compartments with heat transfer material disposed insaid compartments, sealing means between the periphery of said rotor and said stationary structure comprising a plurality of sealing elements pivotally mounted on one of said parts in close proximity to each other to have rocking movement relative to both of said parts forming a substantially continuous ring, a cooperating sealing surface on the other of said parts with respect to which said sealing elements have rocking movement, sealing means between said end plates and each of said radial partitions comprising a pair of sealing members mounted in each side of each partition in opposed relation to rook in sealing contact with said end plates, and biasing means associated with certain of said elements to urge the same into rocking contact with their associated sealing surfaces.

5. In a regenerative air preheater comprising two main parts, a nrst part providing stationary structure comprising a cylindrical casing and end' plates having inlet and outlet openings for flow of gas and air respectively, the second part comprising a rotor mounted within said stationary structure and provided with radial partitions forming compartments with heat transfer material disposed in said compartments, sealing means between the periphery of said rotor and said stationary structure comprising a plurality of sealing elements pivotally mounted on one of said parts to have rocking movement relative to both of said parts, a cooperating sealing surface on the other of said parts with respect to which said sealing elements have rocking movement, sealing means between said end plates and each of said radial partitions comprising a pair of sealing members mounted on eac-h side of each partition in opposed relation to rock in rocking contact with said end plates, and biasing means associated with certain of said elements to urge the same into rocking contact with their associated sealing surfaces.

6. In a regenerative air preheater comprising two main parts, a first part providing stationary structure comprising a cylindrical casing and end plates having inlet and outlet openings for now of gas and air respectively, the second part comprising a rotor mounted within said stationary structure and provided with radial partitions forming compartments with heat transfer material disposed in said compartments, sealing means between the periphery of said rotor and said stationary structure comprising a plurality of rigid sealing elements pivotally mounted on one of said parts in close proximity to each other to have rocking movement relative to both of said parts and forming a substantially continuousrring, a cooperating sealing surface on the other of said parts with respect to which said sealing elements have rocking movement, and biasing means associated with certain of said sealing elements to urge the same into rocking contact with their cooperating sealing surfaces.

7. In a regenerative air preheater comprising two main parts, a first part providing stationary structure comprising a cylindrical casing and end plates having inlet and outlet openings for ow of gas and air respectively, the second part comprising a rotor mounted within said stationary structure and provided with radial partitions forming compartments with heat transfer material disposed in said compartments, sealing means between the periphery of said rotor and said stationary structure comprising a plurality of sealing elements pivotally mounted on one of said parts in close proximity of each other to have rocking movement relative to both of Said parts and forming a substantially continuous ring, a cooperating sealing surface on the other of said parts with respect to which said sealing elements have rocking movement, and biasing means associated with certain of said sealing elements to urge the same into rocking contact with their cooperating sealing surfaces.

8. In a regenerative air preheater comprising two main parts, a rst part providing stationary structure comprising a cylindrical casing and end plates having inlet and outlet openings for flow of gas and air respectively, the second part comprising a rotor mounted within said stationary structure and provided with radial partitions forming compartments with heat transfer material disposed in said compartments, sealing means between the periphery of said rotor and said stationary structure comprising a plurality of sealing elements pivotally mounted on one of said parts to have rocking movement relative to both of said parts, a cooperating sealing surface on the other of said parts with respect to which said sealing elements have rocking movement, and biasing means associated with certain of said sealing elements to urge the same into rocking contact with their cooperating sealing surfaces.

9. In a regenerative air preheater comprising two main parts, a first part providing stationary structure comprising a cylindrical casing and end plates having inlet and outlet openings for flow of gas and air respectively, the second part comprising a rotor mounted within said stationary structure and provided with radial partitions forming compartments with heat transfer i material disposed in said compartments, sealing means between said end plates and each of said radial partitions comprising a pair of rigid sealing members pivotally mounted on each side of each partition in opposed relation to rock in sealing contact with said end plates, and biasing means associated with certain of said sealing elements to urge the same into rocking contact with said end plates,

10. In a regenerative air preheater comprising two main parts, a rst part providing stationry structure comprising a cylindrical casing and end plates having inlet and outlet openings for iiow of gas and air respectively, the second part comprising a rotor mounted within said stationary structure and provided with radial partitions forming compartments with heat transfer material disposed in said compartments, sealing means between said end plates and each f said radial partitions comprising a pair of sealing members pivotally mounted on each side of each partition in opposed relation to rock in sealing contact with said end plates, and biasing means associated with certain of said sealing elements to urge the same into rocking contact with said end plates.

11. An apparatus as defined in claim 10 in which each pair of sealing members comprises a member mounted adjacent to the upper edge of the partition and a member mounted adjacent to the lower edge of the partition, said biasing means comprising arms attached to said upper sealing members and a Weight secured on each arm.

12. An apparatus as defined in claim 11 in which the weight of said lower sealing members serves to urge these members into sealing contact with the lower end plate.

13. An apparatus as defined in claim 8 in which each sealing element comprises a rigid elongated bar forming a segment of a circle, fork-like extensions on one edge of said bar disposed over an edge of the periphery of said rotor whereby said element is rockably mounted thereon, an inwardly extending flange on said stationary structure forming said sealing surface, an arm extending from said bar and resilient means secured to said arm and said rotor for urging said bar into sealing contact with said sealing surface.

14. An apparatus as defined in claim 8 in which each sealing element comprises an elongated bar forming a segment of a circle, fork-like extensions on one edge of said bar disposed over an edge of the periphery of said rotor whereby said element is rockably mounted thereon, an inwardly extending ange on said stationary structure forming said sealing surface, an arm extending from said bar and resilient means secured to said arm and said rotor for urging said bar into sealing contact with said sealing surface.

15. An apparatus as defined in claim 8 in whichv each sealing element comprises an elongated bar forming a segment of a circle, fork-like extensions on one edge of said bar disposed over an edge of the periphery of said rotor whereby said element is rockably mounted thereon, an arm extending from said bar and resilient means secured to said arm and said rotor for urging said bar into sealing contact with said sealing surface.

16. An apparatus as defined in claim 8 in which each sealing element comprises a rigid elongated bar, fork-like extensions adjacent to one edge of said bar disposed over an edge of the periphery of said rotor whereby said element is rockably mounted thereon, an inwardly extending flange on said casing forming said sealing surface and a leaf spring having one end secured to said rotor and the free end bearing on said bar to retain said bar on said rotor and urge the same into sealing contact with said sealing surface.

17. An apparatus as deiined in claim 8 in which each sealing element comprises an elongated bar, fork-like extensions adjacent to one edge of said bar disposed over an edge of the periphery of said rotor whereby said element is rockably mounted thereon, an inwardly extending flange on said casing forming said sealing surface and a leaf spring having one end secured to said rotor and the free end bearing on said bar to retain said bar on said rotor and urge the same into sealing contact with said sealing surface.

18. An apparatus as dened in claim 8 in which each sealing element comprises an elongated bar, fork-like extensions adjacent to one edge of said bar disposed over an edge of the periphery of said rotor whereby said element is rockably mounted thereon and a leaf spring having one end secured to said rotor and the free end bearing on said bar to retain said bar on said rotor and urge the same into sealing contact with said sealing surface.

19. An apparatus as denned in claim 8 in which each sealing element comprises an elongated bar, fork-like extensions adjacent to one edge of said -bar disposed over an edge of the periphery of said rotor whereby said element is rockahly mounted thereon and a leaf spring secured to said rotor and bearing on said bar to retain said bar on said rotor and urge the same into sealing contact with said sealing surface.

20. An apparatus as dened in claim 8 in which each sealing element comprises an elongated bar, fork-like extensions adjacent to one edge of said bar disposed over an edge of the periphery of said rotor whereby said element is rockably mounted thereon and resilient means secured to said rotor and bearing on said bar to retain said bar on said rotor and urge the same into sealing contact with said sealing surface.

21. An apparatus as defined in claim 8 in which each sealing element comprises a rigid elongated bar arcuate in cross section, means for rockably mounting said bar on said rotor, an arm eX- tending from said bar inwardly o1" said rotor and a weight secured to said arm for biasing said bar into sealing contact with said sealing surface.

22. An apparatus as dened in claim 8 in which each sealing element comprises an elongated bar arcuate in cross section, means for rockably mounting said bar on said rotor, an arm extending from said bar inwardly of said rotor and a weight secured to said arm for biasing said bar into sealing contact With said sealing surface.

23. An apparatus as defined in claim 8 in which each sealing element comprises an elongated bar, means for rockably mounting said bar on said rotor, an arm extending from said bar inwardly of said rotor and a weight secured to said arm for biasing said bar into sealing contact with said sealing surface.

24. An apparatus as defined in claim 8 in which each sealing element comprises an elongated bar, means for rockably mounting said bar on said rotor, an arm extending from said bar and a weight secured to said arm for biasing said bar into sealing contact with said sealing surface.

25. An apparatus as defined in claim 24 in which said means for rockably mounting said bar comprises an aperture in the periphery of said rotor with said arm rockably disposed in said aperture.

26. An apparatus as defined in claim 24 in which said means for rockably mounting said bar comprises a hinge connection between said bar and said rotor.

27. An apparatus as defined in claim 8 in which said sealing element comprises a rigid elongated bar arcuate in cross section and means for rockably mounting said bar on said rotor, the weight of said bar serving to retain the same in sealing contact With said sealing surface.

'28. An apparatus as defined in claim 8 in which each sealing element comprises an elongated bar arcuate in cross section and means for rockably mounting said bar on said rotor, the weight of said bar serving to retain the same in sealing contact with said sealing surface.

29. An apparatus as defined in claim 8 in which each sealing element comprises an elongated bar and means for rockably mounting said bar on iii said rotor, the Weight of said bar serving to retain the same in sealing contact with said sealing surface.

30. An apparatus as deiined in claim 29 in which said means for rockably mounting same bar comprises an aperture in said bar and a pin secured to said rotor and rockably disposed in said aperture.

31. An apparatus as defined in claim 8 in which each sealing element comprises a rigid elongated bar substantially arcuate in cross section, means for rockably mounting said bar on said rotor and a compression spring engaging said rotor and said bar to urge the same into sealing contact with said sealing surface.

32. An apparatus as defined in claim 8 in which each sealing element comprises an elongated bar substantially arcuate in cross section, means for rockabiy mounting said bar on said rotor and a compression spring engaging said rotor and said bar to urge the same into sealing contact with said sealing surface.

33. An apparatus as defined in claim 8 in which each sealing element comprises an elongated bar, means for rockably mounting said bar on said rotor and a compression spring engaging said rotor and said bar to urge the same into sealing Contact with said sealing surface.

34. An apparatus as defined in claim 33 in which said rotor is provided with an outwardly extending ange and a pin secured to said flange serving to receive and guide said compression spring.

35. An apparatus as defined in claim 33 in which said means for rockably mounting said bar comprises an aperture in said bar and a pin se cured to said rotor and rockably disposed in said aperture.

36. In a regenerative air preheater comprising two main parts, a iirst part providing stationary structure comprising a cylindrical casing and end plates having inlet and outlet openings for iiow of gas and air respectively, the second part comprising a rotor mounted within said stationary structure, said rotor having an outer peripheral shell and being provided with radial partitions forming compartments with heat transferl ma* terial disposed in said compartments, and sealing means comprising a plurality of rigid sealing elements pivotally mounted on one of said main parts to have rocking movement relative to both cf said parts and to bear against cooperating sealing surfaces on the other oi said main parts, said sealing means providing seals between said shell and said partitions of the rotor on the one hand and said stationary structure on the other hand and located to bear against cooperating sealing surfaces on 'the other of said main parts, and biasing means associated with said rocliaoly mounted sealing elements for urging the same into yieldable rocking contact with their cooperating sealing surfaces.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,287,777 Boestad June 30, 1942 2,471,995 Yerrick et al. May 31, 1949 2,517,512 Tigges et al. Apr. 1, D 2,549,656 Yerrick et al. Apr. 17, 1951 FOREIGN PATENTS Number Country Date 162,250 Great Britain July 21, 1922 500,682 Great Britain Feb. 14:, 1939

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