US2588434A - Impact bar assembly for impeller breakers - Google Patents

Description

March 11, 1952 F. P. UNTI ETAL IMPACT BAR ASSEMBLY FOR IMPELLER BREAKERS Filed June 16. 1949 3 Sheets-Sheet l Snnentors:

FRANKPUNTI, JOHN r P0775, A/vaw c. ENS/6W,

. Gttomegg March 11, 1952 P. UNTI EIAL 2,588,434

IMPACT BAR ASSEMBLY FOR IMPELLER BkEAKERs Filed June 16. 1949 5 Sheets-Sheet 2 m ,N, s mnm m w w mm mm 8 mfl MIG nus Y "MW H A smw /H I k Ill 3m 38w \a N n q u 33W N QN March 11, 1952 F. P. UNTI ETAL IMPACT BAR ASSEMBLY FOR IMPELLER BREAKERS 5 Sheets-Sheet 3 Filed June 16, 1949 MM NW FEM/3 5%? JOHN r fPorr's,

Patented Mar. 11, 1952 IMPACT BAR ASSEMBLY FOR IMPELLER BREAKERS Frank P. Unti, Anaconda, Mont, and John T. Potts and Angus. 0. Ensign, Salt Lake City,

Utah

Application .J une 16,. 1949,v Serial No. "99,374

This invention relates to impact bars for impeller breakers which exert an impact action in the breaking of rocks, ores, and similar hard materials. It has particular pertinency to doubleimpeller breakers which exert a so-called dual impact action.

Double-impeller breakers exerting such dual impact action are a comparatively recent developement in the field of crushers and similar machines for breaking rocks, ores, and similar hard materials into pieces of desired size for industrial uses. These breakers represent a, radical departure from conventional crushers, rolls, and similar machines.

The term dual impact action" has reference to the manner in which the double impellers of the machine operate in conjunction with stationary breaker bars, so that raw material fed to the machine receives a first breaking impact. from.

the impellers, and then a second breaking impact as it is forcibly flung against the stationary breaker bars by the impact action of the impellers. Thus, breaking of the material isaccomplished entirely by impact action, as distinguished from conventional crushing action.

In a machine of this type, the two impellers rotate in opposite directions opposed to the feed of material, so that material falling. between them is forcibly ejected outwardly in the direction of the stationary breaker bars. A gravity feed is. commonly utilized, with the material'falling. between the two impellers, which are horizontally disposed. Immediately afterwards, the material is ejected upwardly and outwardly against the stationary breaker bars, whichare horizontally positioned above the rotating impellers in spaced parallel relationship therewith.

The impellers, as commonly supplied, each comprise an elongate center-body of uniform cross-section throughout. mounted on a shaft suitably, journaled for rotation. The crosssectional configuration of the center-body may be appropriately described as approximately equilaterally triangular, with the sides of the triangle convexly arcuate.

The longitudinally-extending vertices of the center-body are re-entrantly recessed to provide elongate locking slots, into which are slid, endwise, respective elongate impact bars of approximately I-configuration in cross-section. One of the longitudinally extending cross-flanges and the web of the I-bar fit into the'locking slot, the remaining cross-flange protruding outwardly and longitudinally of the center-body, at a vertex thereof, as an impeller impact member. End Wedges lock the respective impact bars in place 6. Claims. (Cl. 241-197) 2 against longitudinal movement, and cinch them tightly in the locking slots against play radially of the center-body. Thus, the impact bars are rigid with respect to the center-body. The two cross-flanges of each I-bar are extremely heavy, and have well-defined corner edges for impact purposes, onlyone edge being in working position at any given time.

In operation, the leading edge portions of the respective impact bars exert an upward striking.

action .upon material that-is fed from above into the troughed space betweenthe impellers. This impact action serves to intercept the-incoming material and to project the same upwardly so as to strike'the heavy stationary breaker bars. Such striking actionof the impact bars rapidly wears away those respective corner edges thereof" which l adin the rotation of the impellers.

It is a much-publicized feature of this doubleimpeller. breaker that the I-shaped impact bars of the impellers may be removed from the centerbody, turned, andreinserted when a particular striking edge thereof becomesworn awayor is otherwise rendered unfit for further use. Ordi narily there are four striking edges on each impeller bar, these edges being used successively. Thus, three replacements -for the original strik ing-edgeare provided by each bar. When, how ever, all four longitudinally-extending corner edges of an impact bar have gone. through a working position-and beenlsufiiciently worn, the bar must be completely discarded and replaced by a newone.

Each impact bar of what is known as the model30-30 Double Impeller Breaker manufactured by the New HollandManufacturing Co; of Mountville,Pennsylvania, which is a typical machine of average size, weighs approximately 400 pounds, and, although removal and reversal or replacement of same ordinarily consumes but one-half hour of time, the total time lost from productive work in the reversal or replacement of the six impact bars incorporated in the two impellers, amounts to 3 hours. Furthermore, the labor of two men is required for the handling of each bar; Where the material worked upon is'veryhard and abrasive, as in the case of ores to bereduced in size for use in the metallurgical industry, it has been found that each striking edge of an impact I -bar lasts only approximately 72 hours, meaning a shutdown for aperiod of 3 hours twice a week where a-plant is-operating 24 hours a day. This is prohibitive in most industries, even though great advantages are derived from useof this type breaker ascompared with more conventional types.

Furthermore, heavy losses are sustained in the continual junking of worn impact bars. The discarded bars represent tons of expensive material, the junking of which is highly uneconomic. Again, in instances of unduly abrasive materials it is necessary that the impact I-bars be made of such hard metal that serious difficulty is encountered by cracking of the web of the I under impact on the working flange thereof. Thus, the use of the machine can be justified only in exceptional instances, or in industries where the rock materials handled are of such character as produce only minor wear of the impact surfaces.

Faced with such problems in the use of this double-impeller, dual-impact-action breaker, we have perfected a composite impact bar which overcomes the difliculties to such an extent as to render this type of breaker economically applicable to practically all industries utilizing crushed ore, rock, and other hard, tough, and abrasive materials, almost regardless of the degree of hardness, toughness or abrasiveness of the principal objects of the invention To provide for rigid securement of all parts of the composite impact bar with respect to the center-body, while affording rapid release of impact parts from other parts thereof and from the center-body.

.To provide the improved impact barin such manner that no changes need be made in either the machine proper nor in the center-bodies of the respective impellers, to accommodate such bars.

- To provide theabove by means of a simple and economical arrangement which adds to the overall efficiency of the machine.

We achieve these objects by a construction embodying a permanent core or skeleton bar of reduced cross-section, adapted to be inserted within and extend longitudinally of a locking re cess of the center-body in substantially the same manner as the I-bars presently in use. Such core,.or skeleton bar need not be, however, and preferably isnt symmetrically formed, for it is not turned or reversed in the replacement of wear surfaces. thereof which projects from the recess when such core or skeleton bar is installed in the centerbody, isformed to receive and retain a removable andreplaceable wear and impact cap arrangementwhich contains but a small fraction of the metal content of the entire bar and which may be conveniently and quickly installed and removed with respect to the core or skeleton bar. In this manner, not only is time, labor, and material saved in the replacement of worn striking That longitudinally-extending portion a 4 for the particular operation, being dependent in quality upon the nature of the raw material to be broken by the machine.

The particular construction presently preferred involves the making of the permanent core of a bar formation which differs significantly from that previously utilized, in that it is not symmetrical. A longitudinally-extending foot portion is dimensioned to be received by the locking slot of the center-body, and may be reduced in bulk as found appropriate in order to save material; At the top of the bar, a longitudinallyextending cross-flange portion is reduced in difmension such that it serves as a tongue adapted to receive a mating groove of the wear and impact cap arrangement. In this manner, the permanent core bar and the cap arrangement may be both securely locked in position in the centerbody by means of wedges, enabling rapid removal and replacement of the cap arrangement with respect to the core bar.

We have found it highlyadvantageous in practice to make the cap arrangement in sections,

considered longitudinally of the core bar, the sevedges, but the cap-supporting core may be made of a tough material especiallyadapted to absorb impactwithout cracking, while the cap may be of a hard and abrasive-resistant material selected I,

eral sections being successively slid into place on the core bar which supports them in common. Ordinarily, three cap sections will be utilized for a single core bar, the cap sections being individually fastened to the core bar by means of removable pins or plugs which fit into receiving passages formed through a wear-protected portion of the cap section and having continuations formed in the core bar. A pair of locking wedges,

drawn into place by means of a mutually interconnecting tie rod, is utilized in much the same manner as in the conventional construction to complete the fastening arrangement. Such wedges, however,'are here formed to react against both the respective terminal cap sections and the base flange of the permanent core, effectively locking both the cap arrangement and the per.- manent core in working position in the centerbody of the impeller.

In changing worn caps, the wedges and pins are removed, and the individual cap sections slipped off the receiving flange-tongue of the core bar. Since each cap section has two impact edges, one reversal is possible prior to replacement by a new cap section.

It should be noted that. in this preferred construction, the locking wedges exert pressure longitudinally of the cap arrangement, which results in the binding of the transversely extending fastening pins in their receiving passages and the production of an especially effective lock of shoes to core bar and core bar to center-body. While this presently preferred construction has many characteristics which produce superi'or results in practice, other arrangements of caps and fastening means conforming to the broad inventive concept will be found to be far superior to the conventional impact bars in common use.

Further objects and features of the invention will become apparent from the following detailed description of the presently preferred specific construction illustrated in the accompanying drawings.

In the drawings: Fig. 1- represents a side elevation, partly in Fig, 2, a fragmentary end-elevation of one of I.

the; impellers, showing one .of the composite im pact bflI'Si securely mounted. inithe' center-body of; the; impeller; theview: being drawn to an enlarged scale;

Fig; 3, a partial. elevation and partial. section taken. largely onthe line 3--3 of Fig. 2;

Fig. 4, a. partial top plan and horizontal sectiontaken largely onthe line 4-4 of Fig. 2;

5,.a .side elevation of. the-composite impact bar per-se, showing the pins utilized to fasten. the individual cap sections to the core bar:

Fig 6, a 'vertical, transverse section taken on the :line 6-6 of Fig. 5;

Fig. 7, a fragmentary perspective view, drawn to anenlarged scalerof an end of a center-body showing a wedge-receiving recess thereof; I

Fig. 8,.a perspective view of one of the locking wedges which fit into the. wedge-receiving recesses; and

r Fig. 9, assimilar perspective view but showing theoppositeside of the wedge.

Referring to the drawings: the double-impeller; dual-impact-action breaker illustrated in Fig. 1 is the aforementioned model 30-30, manufactured by the-New Holland Manufacturing Company of Mountville, Pennsylvania. It includes an external-housing I0, within which and at a lowlevel thereof are mounted respective impellers H on horizontal axes of rotation. I

Such impellers each comprise a center-body l2, whose cross section is of equilateral triangularconfiguration, the sides of the triangle being' convexly arcuate. While this particular configuration was adopted by the manufacturer as most desirable in instances where three impact bars are employed, other configurations are possible. The important thing is that the center-body be correctly designed from an engineeringistandpoint to withstand the stresses and strains imposed upon it during rotation, to providefor maximum effectiveness of the impact bars in operation of the machine, and to provide proper anchorage for the removable impact bars.

The center-body 12 is of uniform cross-section throughout its length, and is fixed to a shaft l3 whose-ends are journaled in'respective bearings ll disposed exteriorly'of the housing 10.

The two impellers I I are mounted side by side for rotation in respectively opposite directions, as" indicated by arrows in Fig. 1. Their impact actionis exerted upwardly against raw material I5 fed'from above into the troughed space definedbetween the two impellers.

above the impellers, as illustrated.

In operation, the material l5 receives a first impact action from the upwardly and outwardly rotating impellers 1 I, and is flung against sta-' The invention isnot concerned with the structureth'us far described, except insofar as it provides a setting for the composite impact bars about to be described. Certain aspects of the impeller center-bodies, as hereinafter set forth, are, however, important in combination with the impact bars of the invention and the particular fastening means here shown:

The center-bodies I2 carry impact bars which directly strike the incoming raw material and Thematerial I5 is fed along a table IE to a point of discharge extert. a breaking action thereon. aforestated, such impact bars as conventionally constructed are'j of arrintegral I-configuration possessing-four. striking edges, thebars being re movable and replaceable. within respective receiving recesses formed longitudinally and in spaced relationship along the center-body, being placed atand along the respectiveverticesvin those instances. where the. center-body is. triangularly-formed. This arrangement enables the impact bars to be changed in positionwith respect to the. center-body as. wear dulls the. striking, edges thereof, so that the four striking edges of each bar maybe successively placed in working position during the course. of operation-of the machine, and so. that. the bars. may be.-

replaced after all four striking edges are sufficiently worn.

In accordance withtheinvention, however, the impact bars are of composite formation, embodying a permanent core/or skeleton bar and aremovable and replaceable wear and impactnap arrangement having two striking edges.

As illustrated, it is presently preferred to'make the core orxskeleton bar 20 of each composite impact bar of what may be regarded as a conventionalized T-formation in crosssection having, anupper longitudinally-extending cross-flange Zea formed as a tongueifor receiving the. cap arrangement, a lower longitudinally-extending foot ZOb-for positioning within a locking groove of a center body |2,-"and an intermediate longitudinally-extending ,web 200. Such core bar 2! possesses only a fraction of the bulk of the im-- pact I-bar commonly employed in this machine,

and is a permanent though removable part of the impeller. It is not subject to wear, for it is shielded by the cap arrangement. about to be' described. Accordingly, it may and preferably is formed of --a tough and relatively elastic material, such as a mild low-carbon and high tensile strength steel, capable of absorbingv impact shocks without cracking, even though sucl'rmaterial would be unsuitable as a direct impact surface.

The cap arrangement preferably comprises a series of individual cap sections 2| longitudinah ly disposed with respect to the core bar. Each cap section 21 is formed with a groove. 22 extending longitudinally of its under-surface: and arranged to receive. the cross or tongue flange end abutting alignment so as to completelysheath those portions of the core bar which project from the center-body. Since the groove 22' is re-entrant within the cap sections 2|, respective portions 2 la which define the mouth of the groove longitudinally of the section hug the undersurface of the cross or tongue flange 20a of the core barv and close. aboutthe upper portion of the web 200 thereof. The capsections 2] arcinstalled-on-the core bar 20 by successively sliding them endwise upon the receiving cross or tongue flange 2011, which servesv as the cap attachment portion of the core bar.

For the purposes of securement, transversepin-receiving passages 23., Figs. 5 and 6, are pro-'- vided in the under-portionsZla of the respective capsect'ionsand registering continuationsfl-l.

. are provided in the cross or tongue flange 2-000! the core 'bar. Dowel pins 24 are fitted into the respective passages 23;23l following placement of the cap sections on the core bar.

It should be noted that each cap section 2| has two oppositely-positioned striking edges, indicated 21b respectively, extending longitudinal- 1y thereof, and that the sections may be reversed in position upon the anchoring core bar 20, so that such striking edges are successively disposed in Working position on the impeller.

It is a feature of the invention that the composite core bars may be constructed for utilization with impeller center-bodies currently in use.

Such center-bodies, as here shown of triangular formation in cross-section, have re-entrantly formedlocking grooves 25 extending longitudinally thereof at the respective vertices. The longitudinally-extending feet of the respective composite impact bars are formed to be slidable -endwise into such grooves 25, possessing beveled shoulders 2011 which mate with opposite ly-dis'posed, re-entrant, beveled shoulders a of such grooves, see Fig. 2. The several cap sections 21 have their under-portions 2la beveled downwardly along the outer faces thereof to mate with bevels 251) which define an elongate flaring mouth for the grooves .25. As so formed, wedges,

such 'for example as those here illustrated and indicated 26, may be utilized in connection with the standard wedge-receiving recesses 21, Fig. '7,

formed at opposite ends of each groove 25 of the" center-body, such wedges serving in the case of the present invention to retain both the core.

bar-20 and the several capsections 2| tightly in place.

. The wedges 26 are uniquely formed. As

noted that such bottom-slopes upwardly and m wardly from the open end of the recess, see Fig. '7, and that the wedge-action face 2% slopes ac: cordingly with respect to the upper bevel face 26a of the wedge. The lateral face 260 of the wedge which adjoins the lower edge of the bevel face26a is arranged to be parallel with the 015-: posing lateral face of web 200 when the wedge is inserted within a recess 21, see Fig. 2, such 0p-; posing lateral faces playing no part in the wedging action. The opposite lateral wedgeaction face 26d of the wedge, however, slopes inwardly for face-to-face engagement with the correspondingly sloping lateral wall surface 21b of the recess 21. Thus, the wedge 26 has sloping wedge-action faces bearing against both the bottom and the lateral side wall surfaces, respectively, which define the recess 21, and a guide face bearing against the beveled lower surface of a corresponding one of the under-portions 2 la of a terminal cap section 21.

-It should be noted that the wedge-action face 26b of the wedge, which engages the bottom wall surface 21 of the recess, also has a certain bearing against the corresponding beveled shoulder portion of the longitudinally-extending foot 205 of'the core-bar 20, as a lower pressure guide working in conjunction with the above-described upper pressure guide provided in connection with the terminal cap section 2|. Thus, opposing radial locking pressures are brought to bear against the terminal cap section 2| and the corresponding end of the core bar 20, by the wedge 26, thereby effectively holding the entire cap arrangement, and the core bar on which it is carried, against play radially of the impeller.- 'At the same time, longitudinal pressure is exerted by the wedge, tending to bind the dowel pins 24 of the respective cap sections within theirreceiving passages, and thereby efiecting further securement of the cap arrangement with respect to the core bar, as well as a locking action on both cap arrangement and core bar against movement longitudinally of the impeller.

A beveled face 26c is provided for the wedge at what would otherwise be a sharp corner, thereby maintaining all parts of the wedge within the protective coverage of the receiving recess 21.

Pairs of oppositely-placed wedges 25 are drawn into locking positions within their respective recesses 21 by means of respective inter-connecting tie-rods 28, see Fig. 3.

In operation,-the core bars 20 and can sections 2! are held firmly in position by means of the wedges 26, eflectively resisting the heavy stresses and strains brought to bear against them by reason of the impact action which they exert against the relatively large pieces of hard material [5.

When the leading one of the two longitudinally-extending striking edges 2) of a cap arrangement is sufficiently worn to be ineffective for its intended purpose, the wedges 26 are removed by unscrewing a cinching nut 29 from the end of the tie rod 28 and removing such tie rod. The dowel pins 24 are removed, and the several cap sections 2| are removed from the cross or tongue flange 20a of the core bar 2.,

and are reversed in position, end-for-end, being" replaced on such tongue flange of the core bar with the opposite and unworn striking edges 2lb thereof in leading position. Thereupon, the dowel pins 24, locking wedges 26, tie rod 28, and cinching nut 29 are replaced, and the machine operated again until the newly-positioned strikin edge 21b of the cap arrangement is sufficiently worn. Whereupon, a similar procedure is gone through for the installation of new can sections.

.At no'time need the core bar 20 be removed from the locking slot 25 of the center-body during the changing of caps, though it is freely removable if for any reason that becomes desirable. The individual cap sections are not unwieldly,

and may be easily handled by one workman. The time required for change of caps is only a frac-- tion of that required for the change of the I-bar as previously constructed, and the material lost to scrap is only a fraction of that previously lost. Furthermore, when certain portions of a cap arrangement are subjected to greater wear than other portions thereof, as often happens in practice where the incoming stream of raw material to be broken differs in character transversely of the stream, only those particular cap sections of such cap arrangement which actually need reversal or replacement need be reversed or replaced, whereby waste and maintenance costs are reduced to a minimum.

In order to facilitate the removal of dowelpins 24, their outer ends are advantageously drilled and tapped, as shown at 30, Fig. 6, for receiving the threaded end of a suitable disengaging tool. Furthermore, in order to facilitate the removal of wedges 26, they are provided with openings 31, Fig. 9, for anchoring a suitable wedge-pulling tool.

The tie rod 28 connecting a, pair of oppositely positioned wedges 26 extends through passages 32, Figs. 8 and 9, formed in the respective wedges, and through a passage 33, Fig. 7, formed in and extending longitudinally of the corresponding overhanging lip defining the mouth of re-entrant locking groove 25 of the center-body. Such passages 32 and 33 are approximately oval in configuration, so as to afiord limited lateral travel for the tie-rod 28 as the wedges travel inwardly of the recesses 21 during the cinching operation.

It has been convenient to illustrate and describe important features and characteristics of the invention from the standpoint of impellers employed in a particular type of impeller breaker, namely, the double-impeller dual impact action breaker manufactured by the New Holland Manufacturing Co., as aforesaid. Nevertheless, it is obvious that impact bars of the invention may be utilized in connection with suitable impellers of other types of breakers, whether utilizing a single impeller in connection with other cooperating mechanism or double impellers as here illustrated.

Though this invention is here illustrated and described in detail with respect to one presently preferred form thereof, it should be understood that changes may be made therein and that other forms may be constructed on the basis of the teachings hereof, by those skilled in the art, without departing from the protective scope of the claims which here follow.

We claim:

1. A composite impact bar assembly for impeller breakers having a center-body provided with at least one re-entrant and longitudinally extending locking groove, and wedge-receiving recesses at opposite ends of said groove, said assembly comprising an elongate core bar having longitudinally-extending foot, cap-attachment portion, and intermediate web, said foot being shouldered longitudinally with respect to the web for securement within said re-entrant locking groove of said impeller center-body, and said capattachment portion being formed as a cross flange arranged to project outwardly from said locking groove as an attachment tongue for a cap arrangement when said bar is installed in the center-body; a wear and impact cap arrangement comprising a plurality of individual cap sections adapted to fit together in end-to-end longitudinal alignment, the several cap sections having their undersurfaces correspondingly re-entrantly grooved for snug mating with the attachment tongue of the core bar; and fastening means for.

securing the cap arrangement to the core bar, said means including a pair of wedges for insertion in respectiveones of said wedge-receiving recesses, said wedges being formed for reaction against said foot, the terminal sections of said cap arrangement, and the center-body and means for forcing said wedges inwardly of said recesses.

2. An impeller for impeller-type breakers, comprising an elongate center-body of substantially uniform cross-section throughout its length; a plurality of re-entrant locking grooves extending, respectively, longitudinally from end-to-end of the center-body in mutually spaced relationship about the peripheral surface thereof; wedge-receiving recesses formed at opposite ends of the center-body adjacent and opening into respective locking grooves thereof; a plurality of elongrooves along their undersurfaces snugly mating with the tongues of respective core bars; locking wedges fitted into respective recesses of the cen-.- ter-body, said Wedges being formed for and having reaction against corresponding feet of the core bars, corresponding terminal cap sections, and walls of corresponding recesses of the center-bQdy; and means cinching pairs of opposing wedges tightly into place.

3. The combination recited in claim 2, wherein each cap section has a pin-receiving passage extending transversely through an underpart thereof, and the tongue of each core bar is provided with aligned continuations of the passages of the cap sections which are mounted thereon; and wherein dowel pins are snugly fitted within respective passages and the continuations thereof.

4. The combination recited in claim 2, wherein the cinching means comprise tie rods equipped with cinching nuts.

5. A composite impact bar assembly for impeller breakers having a center-body provided with at least one re-entrant and longitudinally extending locking groove, and wedge receiving recesses at opposite ends of said groove, said assembly comprising an elongate core bar having a longitudinally-extending foot, cap-attachment portion, and intermediate web, said foot being shouldered longitudinally with respect to the web for securement within said re-entrant locking groove of said impeller center-body, and said capattachment portion being formed as a cross flange arranged to project outwardly from said locking groove as an attachment tongue for a cap arrangement when said bar is installed in the center-body; a wear and impact resistant cap arrangement having its undersurface re-entrantly grooved in correspondence with and for snug mating with the attachment tongue of the core bar; and fastening means for securing the cap arrangement to the core bar, said means including a pair of wedges for insertion in respective ones of said wedge-receiving recesses, said wedges being formed for reaction against said foot, opposite ends of said cap arrangement, and the center-body, and means for forcing said wedges inwardly of said recesses.

' 6. In an impeller breaker, the combination with an elongate center-body having at least one reentrant and longitudinally extending locking groove, and wedge-receiving recesses at opposite ends of said groove, of a composite impact bar as sembly which comprises an elongate core bar having longitudinally-extending foot, cap-attachment portion, and intermediate web, said foot being shouldered longitudinally with respect to the web and secured within said re-entrant looking groove of said impeller center-body, and said cap-attachment portion being formed as a cross flange which projects outwardly from said locking groove as an attachment tongue for a cap arrangement, a wear and impact cap arrangement made up of a plurality of individual cap sections having their undersurfaces correspondingly reentrantly grooved for snug mating with the attachment tongue of the core bar, said cap sections being mounted together in end-to-end longitudinal alignment upon said attachment tongue of the core bar, and fastening means securing said cap arrangement to the core bar, said fastening means including a pair of wedges respectively formed for reaction against said foot, against the terminal sections of said cap arrangement, and against the center-body, said wedges being inserted in respective ones of said web-receiving recesses, means for forcing said wedges inwardly of said recesses, and a series of passages extending 10 I 2,486,421

through underportions of the respective cap sections transversely of the length thereof and into the center-body, and. fastening elements positioned within the respective passages.

FRANK P. UNTIL JOHN T. POTTS. A. C. ENSIGN.

12 REFERENCES CITED Number Name Date 550,253 Gross et a1 Nov. 26, 1895 1,798,000 Schultz Mar. 24, 1931 2,378,475 Gruender June 19, 1945 Kessler Nov. 1, 1949 FOREIGN PATENTS Number Country Date 301,386 Italy Oct. 3, 1932'

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