US2581351A

US2581351A - Mast

Info

Publication number: US2581351A
Application number: US649450A
Authority: US
Inventors: Eric A Black
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-02-21
Filing date: 1946-02-21
Publication date: 1952-01-08
Anticipated expiration: 1969-01-08

Description

Jan. 8, 1952 I BLACK 2,581,351

MAST

Filed Feb. 21, 1946 4 Sheets-Sheet l INVENTOR.

ERIC A. BLACK ATTORNEY Jan. 8, 1952 Filed Feb. 21, 1946 E. A. BLACK MAST 4 Sheets-Sheet 2 l/3O K 94 INVENTOR.

ERIC A. BLACK 13y L "/-'e/4'M g, A

ATTORNEY Jan. 8, 1952 E. A. BLACK 2,581,351

MAST

Filed Feb. 21, 1946 4 Sheets-Sheet 3 INVENTOR.

ERIC A. BLACK ATTORNEY E. A. BLACK MAST Jan. 8, 1

4 Sheets-S 4 Filed Feb. 21, 1

I WM M lllllm lllllllr INVENTOR. ERIC A BLACK ATTORNEY FIG.8

Patented Jan. 8, 1952 UNITED STATES PATENT OFFICE MAST Eric A. Black, Red Bank, N. J. Application February 21, 1946, Serial No. 649,450

(Granted under the actof March 3, 1883, as

12 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

The present invention relates to masts. v

In the erection and use of various braced compression members, including masts or towers, particularly of the portable type, such as for radio antennas and the like, it is desirable that the parts have lightness coupled with suificient structural strength to resist the stresses incident to erection and use. Although the present invention is particularly well adapted to portable radio towers and .it will be illustrated in connection therewith, it is to be understood that the invention has considerably wider application.

Conventional portable masts and the like are usually sustained by a plurality of guys. In sustaining such masts great care must be taken during erection to avoid rupture of the central mast member. In many cases it has been found necessary to make the central mast member considerably oversized and overweight so that it may withstand the rigors of erection.

If a mast is of the portable type it is ordinarily desirable that it be separable into convenient units to facilitate transportation and handling. Difficulties have arisen in connection with providing suitable coupling means to join said units into an integral structure. Oversized, overweight and complicated parts are a handicap to portability.

The present invention is intended to provide means and a method of construction for masts and the like and also a means of erection wherein simple, relatively inexpensive parts, of less weight and smaller size, may be utilized for structures which may be separated into easily managed units, which may be simply and quickly erected, and which have sufficient structural strength and stability to provide the desired safety factors.

It is therefore an object of the present invention to provide a mast or other structure which may be fabricated of lightweight materials, such as aluminum.

It is a further object to provide such a mast which may be assembled of a plurality of units, each of which may be of a size and weight suitable for portability.

It is still another object to provide simple means for giving such a mast suficient structural strength to allow it to be easily and safely erected and to enable it to withstand windage, loads and other stresses involved in its use.

It is a further object to provide means for prestressing the elements of a mast so as to give it the requisite structural strength and stability.

It is still another object to provide means for applying tension to brace members without the use of turnbuckles or the like thereon.

. .Yet another object isto provide a means for amended April 30, 1928; 370 O. G. 757) 'of post section spliced together.

2 It is still another object to provide a construction for masts and the like which requires a much smaller number of guys and anchor means than conventional structures.

It is still another object to provide a mast wherein stresses within the parts are far better equalized than in conventional structures utilizing a plurality of sets of guys fastened at different levels.

It is another object to provide a construction for masts and the like which is triangular in cross section and thereby has greater sturdiness, strength and stability than conventional quadrilateral structures.

It is yet another object to provide a mast and the like wherein erection may be accomplished without the use of auxiliary gin pole devices.

The foregoing objects and others, which will become clear from the present specification, are accomplished by providing a structure for a mast or the like which includes a central post, which may be made up of a single post or a plurality Said mast is given rigidity and strength by means of a plurality (preferably three) of brace members which are secured, at their opposite ends, to the post and are forced outwardly, at their central portions, so as to be put under suitable tension, by

means of strut members. Said strut members are made adjustable in effective length in a manner somewhat similar to a conventional umbrella.

Each strut member incorporates a stiff strut I having its outer end pivoted to the central portion of a brace member and having its inner end pivoted to a part (hereinafter referred to as a spider) which is longitudinally slidable along the post and is provided with means to pivotally connect with the inner end of said strut. During assembly of the components the said strut is disposed at an angle of somewhat less than to the post. When the spider is moved longitudinally relative to the post, said angle approaches 90 thus pushing the central portion of the brace member outwardly. This subjects the braces to tension and the post to compression.

A simple tower (as shown in Figures 1A and 8) might includes a two section post provided with three outwardly extending adjustable struts and suitable braces. The same principle might be applied to larger masts having any number of sections. One such tower made up of four post sections is shown in the accompanying drawings (Figures 5-7).

Said masts are preferably assembled on their sides on the ground and may then be raised in a number of ways. A simple erecting method, in which some of the parts needed for erection are incorporated permanently into the mast is 60 illustrated in connection with the simple tower aforesaid (Figure 4).

For a better understanding of the invention, together with other and further objects thereof,

referenceis" had to the following description taken in connection with the accompanying drawings, wherein like parts are indicated by. like reference numerals and its scope will be pointed out in the accompanying claims.

In the drawings,

Figure l is an isometric view of a simple'form of mast embodying the presentinvention;

Figure 2 is an enlarged fragmentary perspective view showing details of thecentral-portion of the mast of Figure 1;

Figure 3 is a further enlarged fragmentary view of the central portion of the mastcf Figure l, the upper portion beingshown in vertical section a'n'dth'e lower portion in elevation with parts cut awa for clarity;

Figure 4 is an elevational'viewof the mast of Figure 1 during erection; them as't being shown in solid lines upon the ground and in" broken lines when about halfway up;

Figure 5' is an elev'ati'oiialv'iew of a more complicated mast incorporating the present invention;

Figure 6 is a fragmentaryenlarged'elevational' Referring'now to thefdrawi'ngs, and more'par-' ticularly' tojFigui'es' 1-3 and 8" thereof, the form of radio antenna mastembodying the present invention which is there shown includes a central post sustained upona base ll". Said central post is made up of have and upper post sections l3,

15, each of which sections comprises'an'elongated'm'etal pipe IT, having" three longitudinally disposed slots I9cut throughit', 120 apart, at one end; The slotted end of" each pipe ll (namely, the upper end of the lower post" sec tion I3 and the lower end-of the upper post'sec tion i5) is closed by a" transversely disposedtriangular endplate 21, which is pierced by a'hole 23 at its midpoint and an inwardly extending slot' at each corner, and which is rigidlysecure'd tothe end of the pipeby'anyv suitable means, such as welding.

Three pairs of spaced" parallel gusset flanges 25 (Figures 2, 3 and 8)- aresecured, as by weld ing, to the'outside' of each pipe t1, so as to ex tend outwardly from" said pipealong both sides' of each of theslots' l9 aforesaid. Each of the flanges 25 is pierced along its length by several holesZ'I. Thelower and upper post'sectio'ns i3; 15 are aligned with each other, but with their end plates 2| spaced from each other; and are joined together by three splice plates'z'a'; each of which is a fiat elongated plate pierced by a hole at each end. Each splice plate 29"hasone'enjdf extending between one pair of gusset flanges 25 of one of thepost sections 13, i5 and bolted thereto by a bolt 30, and its other end similarly bolted to the other of said post sections.

Each pipe H is also provided with a spider- 3! (Figures 2, 3 and 8). Each spider 3f is made" up of a short internally threaded sleeve 33 to the outside of which are secured three radially disposed legs 35. Said legs 35 are rigidly joined to the sleeve'33, as by welding, and are'positioned' 120 apart and each leg is pierced by a parrot holes 39. A short tubular g'uidetl. positioned coaxially with the sleeve 3'3; is securedto the three" p 4 lgsi35. Each' spider 3i ispositioned coaxially withoneof the pipes I! so that the sleeve 33 and guide 31 are positioned within said pipe and the three legs 35 extend outwardly through the slots i9 in said pipe. The tubular guide 3? is of a size to makea longitudinally slidable fit within the pipe 11. I

Extending'through the hole 23 in the end plate 2l andthreaded into the sleeve 33 is a hexagonall-y headed spider adjusting bolt ti. Between the head of thebolt' ll and said end plate 2! is a suitable annular thrust bearing 40, which may be of the Oilite type,.which.is made up of metal impregnated"with allubricant. A collar 33 encircling? the bolt just: inside the end plate 21 is fastened to said bolt by a cotter pin as.

The heads of the twospider adjusting bolts 4! are provided; respectively, with an axially disposed dowel 45 and witlij an axial cavity 4?, receivable to saiddowelf fi; so thatsaid'bolts maybev positioned coaxially." head to' head for inch-- vidual"operationalrotation. Itwillnow be seen that,.upon rotationof either one of the spider adjustingibolts 4I,,the'spider'3|, in threaded engagement with'it, is caused tomove longitudi nally relativeto'the' pipe IT;

The lowerextremity'of the lower post section 13' and the'upper' extremity of the upper post section !5 are'e'ach fitted withthree pairs of outwardly extending spaced parallelgusset plates 39 which are" respectively aligned with the pairs of gusset flanges25" at'the other ends of said post sections. The lower end of the-lower post' section l3'is rigidly joined to the T-shaped base I I by means'o'faj base bracket 53;

The T-shaped base is madeup of a stem- 55 and a cross member 51, both of which are preferably made of metal pipe, one end of the stem 55 being securely "joined perpendicularly to the cross member 51 at its midpoint, by any suitable'means, such'as welding, or preferably by a suitable separable bracket (not shown) to allow said stem 55 and cross'me'mber 57 to be disconnected for transportation. A' pair of short tubular cross member extensions 58 are rotatably coaxially joined to the extremities respectively of the'cross in'emberfl" by Ineans'of pipes 68 of slightly smaller diameter, which are rigidly se-- cured to said'cross member extensions 58 and are rotatable relative to the cross member 5'1;

The stem 55; near'its outer end, and each of said cross member extensiorisBBis pierced by a' transverse" anchor opening 64- receivable to the upper end'of aground anchor 62of any suitable of metal pipe is pivptally secured to the outer end of each of the six legs 35 of the two spiders 3i, thus providing three pairs of spider struts 6t extending outwardly from the midportion of the central post, said pairs of spider struts 6| being spaced at intervals about the central post. The outer ends of each pair of spider struts 5i are'pivo'tably fastened to a strut connector 63.

Each of the three strut connectors 63 (see Figured) includes a ihorizontally disposed, flat strut gusset plate 65" to which arewemecr veal:

cally disposed upwardly and downwardly extending connector fins 61, each of which fins is pierced by a hole. Two gusset shackles 69 are secured respectively to said connector fins 61.

Each gusset shackle 69 is made up of a piece of flat metal folded upon itself so as to give it the shape of a U in cross section and its opposite sides are pierced by four holes in mutual register, one of said holes being a horizontally disposed slot 19. Each gusset shackle 69 is also pierced by an elongated fin aperture along its folded portion to allow one of the connector fins 61 to extend therethrough so as to be bolted to said gusset shackle by means of a bolt passing through the slots 16. Said fin apertures are longer than the width of the connector fins 61 extending through them, to allow adjustment therebetween, as will be made clear hereinbelow. One of the strut connectors 63 is fitted, either permanently or temporarily during erection, with a metal ring 68. Said ring 68 should be to the same side of the post sections |3, |5 as the pulley 66 mentioned above. The three strut connectors 63 are joined by three struts 73 which form an equilateral triangle and maintain the strut connectors 63 in their equally spaced positions. Each strut i3 is preferably made of metal pipe, and each of its ends is slotted and bolted directly to one of the strut gusset plates 65.

Three lower braces I5, also preferably made of metal pipe, are bolted, at their lower ends, respectively to the gusset plates 49 at the lower end of the lower post section l3 and, at their upper ends, respectively to the three lower gusset shackles 69 of the three strut connectors 63. Three similar upper braces 11 have their upper and lower ends similarly bolted respectively to the gusset plates 49 at the upper end of the upper post section I5 and to the upper gusset shackles 69 of the strut connectors 63.

Three guys 19, which are also preferably made of metal pipe, have their upper ends pivotally secured respectively to the lower gusset shackles 69 of the strut connectors 63 and their lower ends secured respectively pivotably to guy bolts 8| which extend downwardly through holes in the upper ends of the erection connector arms 59 and are connected thereto (during erection of the mast) by adjusting nuts. The lower ends of said guy bolts 8|, (when the mast is in its erected position) are secured respectively to three ground anchors 62 through suitable adjustable members, such as turnbuckles 83.

A radio antenna 85 (indicated by broken lines) may be sustained upon the upper end of the upper post section l5 in any suitable way and may be maintained thereon by three antenna braces 81 (also indicated by broken lines), preferably of metal pipe, secured at their upper ends to said antenna and at their lower ends respectively to the upper gusset shackles 69 of the strut connectors 63.

As shown in Figure 4, in order to erect the antenna mast described above (Figures 13 and 8) some additional equipment is necessary. This additional equipment includes a conventional chain hoist 89 which includes a loop 9| of chain by which it is operated and two

single ends

93, 95, one of which is shortened while the other is lengthened upon operation of the said loop 9|. Also required are a large coil sprin 91 and an auxiliary ground anchor 62a which is used only during erection and is not needed to support the mast after erection.

The mast just described (Figures 1-4) may be raised in variousways. Howeverpa preferrederection method, and a method for which certain .components of the mast were specifically designed, will now Figure 4.

The base H is first placed horizontally upon the ground in the position it is to occupy when the tower is erected. Using said base as a template a marker is placed in the ground below each anchor hole 64,. The base H is then removed and three ground anchors 62 are sunk into the ground at the three places so marked. The base i! is then replaced in the position which it will finally occupy, so that the three ground anchors 62 respectively extend upward through the three anchor openings 64.

The fourth auxiliary ground anchor 62a is then sunk into the ground at a point aligned with the base stem 55 and distant from the cross member 5'l a distance equal to approximately one-half of the height of the finished tower, so that the three anchors 62 and the auxiliary anchor 62a will delineate the four extremities of a cross upon the ground. I

The upper and lower post sections |3, |5, while on the ground, are then positioned end to end so that the dowel 45 on the head of one of the spider adjusting bolts 4| fits into the axial cavity 5? in the head of the other spider adjusting bolt 4|. The three splice plates 29 are then slipped into the openings between the flanges 25 be described in connection with of the lower and upper post sections I3, l5. The

opposite ends of said three splice plates 29 are then bolted respectively to the three pairs of flanges 25 of the lower and upper post sections I3, I5. The outer end of the base stem 55 is then swung upwardly, the cross member 51 pivoting about its axis during this operation, untilthe base takes the position shown in Figure 4. The lower end of the lower post section I3 is then raised to the position shown in Figure 4 and secured to the base II by means of the base bracket 53.

The spiders 3| should be so positioned at this time that the legs of the upper spider are in register with the uppermost hole of the flanges 25 of the upper post section 15, and the legs 35 of the lower spider 3| are in register with the lowermost holes of the flanges 25 of the lower post section |3.- The six struts 6| are then bolted to the outermost holes 39 of the six spider legs 3| and the other ends of said struts are bolted respectively to the six gusset shackles 69 of the three strut connectors 63. The lower and upper braces 15, H are then bolted into place between the strut connectors 63 and the gusset plates 49 andthe guys 79 are bolted to the strut connectors 63 at one endand to the erection connector arms 59 at the other.

The spider bolts 4| are now rotated by means of a wrench so as to bring the spiders 3| toward each other. While this is being done the bolts H must be loose so that the gusset shackles 69 can slide outwardly while the strut gusset plates 65 and their connector-fins 61 remain stationary. When the arms 35 of the two spiders 3| are so positioned that the inner holes 39 thereof are in register with the middle holes 2'! of the flanges 25, they are bolted in place. The bolts 1| may then be tightened to secure the strut gusset plates 65 respectively to their upper and lower gusset shackles 69.

The chain hoist 89 is now attached to the ring 68 which is attached to the uppermost strut connector 63 as the mast rests on its side. The free end-93 of the said hoist 89 1s brought over ensam the pulley '66: andi down. to the ground: anchor; 62 (to-:th'e right in Figural- 4) where itzistmade'i fast. The other end 95 fiisaid chain hoistl89 connected to the spring 91, the otheinendnof which is made fast to the; auxiliary? ground anchor 62a.- The 2100p 91 L of: the hois't :89 .isxnow pulled in: the direction which I. will: shorten.. the end s3 and lngthen theetxddflr As :this-xis idoner'. the upper end of the mast will begin =to1 rise: and: the entire mast-structura will pivot? about the: axis-of the cross member- 51; saldicrosamember rotating about the-pipes 681 Whenthe mast has been swung. up; to: as. suitable working-- level,- the antennas-85 and an,- tenna braces 83 may be secured iii-2place, w-here.-- upon the erection of i: the: mast by means -i of r" the chain hoist 59- may beresumedluntil the post. sections-i3, Hi areverticali The anchor fii (to the right inF-igure 4J willv then have passed: through the anchor opening fi l' inzthe stemr55.

It willbe noted that during erection the lower: ends of the guys 9- are-helcl in place by theereotion connector arms 59. Assoon-as:th'e mast'is erect, however; the guy bolts B-I- aresecured to the-anchors 6 2- through the turnbucklesflii and are suitably tensioned thereby; The arms 59'may then either be left in'place or removed; asdesired, as-they are only needed durin erection or dis-- nrantling of the mast. The chain hoist-89; spring- Q'I i and auxiliary anchor 62% (to the left in Figurea) may also be removed.

It will be seen that the tightening of the spiders 31; as described above; will'causesuitable tension of the braces l; l'I-and compression ofithe pipes H; but will subject the'struts- I3 to no" strain at-all as the strut gusset platesSS to which theyare secured, are not moved outwardly during-the prestressingoperation.

The nest described (Figures- 14 and- 8') may be sustained by but three guys I9 and ground anchors 62; whereas comparable masts of con ventional design are rectangular so as 'to require atleast four guys and" four anchors and more likely requirea multiple of four guysand anchors, said guys going up tosteady themastsatdifferent levels. For example, a conventional mast known to the applicantrequires sixteen guys and anchors, and two auxiliary anchors needed during erection, making eighteen anchors in all, whereas amast embodying the-present invention, of like size and usefulness; requires but three anchors; and one auxiliary anchor for erection, making four in all. Thus'th'ere isa great saving in expense and" labor. Also addi tional erection equipment, comprising gin poles and the like, areneeded-toraise a-conventional mast Whereas it may be dispensed with in erect ing the mast described above.

A modified form of'antenna' mast embodying the present invention is shown imF-igures 5-7'; Said mast is constructed soas to utilize thesame principles as in the simple mast already de scribed, but is preferably usedin a mast of larger size or ina mast ofsimilar size'but wherein smaller component parts =-a1e provided to facilitate portability.

Saidzmodified form of mast is madeup of a centralpost comprisingfour postsections. IIH', I62; I03; I04, whichare similar: tothe post sections- [3, I5 alreadydescribedinconnection with the simple mast (Figures 1-3),,excep t that the intermediate post sections. I 02', I 0-3 are:- provided withslots- I9. and spiders 31 a-trbothzends. The; two lower post sections I0 I and I02; are. spliced a-.strut:.systemi as? already described; and: shown: in connection with .thersimple form of:mast1(llig -1 mesa-1+3 and;8)-.. Thus. saidpost sections IIJI;. I 02 are joined by; three splice. plates: 29 andtheir strut:spiders;3l are. joined tozthreestrut: conmotors-163 M. meansof six'spider strutsifiL. The: twomppenpostsections 03,104 are alsojoined: toceachother. .in exactly the same way:

The; two; intermediate post. sections; "12,. I03

howeven'. although. joined. together by; similar:

splice plates. 25:, are. providedwith.amorecome pli'cated strut system (see Figures; Gand '7) Said; strut'lsystem includes three. inner:- strut connece tors I: and three. outer.strutconnectors: III'I.

i Each inner-strut.connectoixI 95.;comprises an inner.

3-2 and downwardlyextendingLflat connectonfins ill I and also :piercediby: two. holeson each side re-- ceivable to.v the inner strutsv H5 and theintermediate struts iii; Each of the inner. gusset: shackles H3. is U-shaped in cross section, the: arms being piercedby four holes inregister, one: of i which holes is a horizontally disposed slot Hill-for slidable coupling to a connector fin :H I. Eachshackle II3 is also pierced along its folded portion by an elongated fin aperture to slidably. receive one or the connector fins I I I.

Theinner strut connectors 495 are pivotally joined respectively to the legs35 of the spiders 31 hy pairs of spider struts fil-as already tie-'- scribed above in connection with the simplertower-(Figures 1-3 and 8).

Each inner strut connector IUiikis rigidlyjoined to-one'of the outer strut connectors I 81 by means oi arpair-of=horizontally disposed extension struts 22 i. E'achextension strut is preferably a-length of metal pipe rigidly secured at one end to-oneof 'tlie inner gusset shackles I I3and at theother end' to an outer gusset shackle I23.- Each of'theouter gussetsliackles I23 is U-shaped-in cross" section; is-pierced al0ng its folded-portion by an elongated fin'aperture, and its=arms=are pierced by five holes in register, one of which holes isslot- I25; bywhich said shackle I23 may-be slidably joinedto an outer strutgusset plate I21, which-is a horizontally-disposed flat metal plate pierced i by two holes and provided with two upwardlyext'ending fiat connectorfins I29 extend-- inginto said shackles '423 'throughsaid elongated fin apertures in said shackles-123';

The three outerstrut'connectorsltil-are rigidly joined to'each other by three'outer" struts l3iwhich forma horizontally-disposed equilateral triangle; Each outer strut I 31- is provided. atits" midpointwith an intermediate strut connector I 33 "to Whichare rigidly connected. the outer ends ofthe' intermediate struts I I I;

Itwill now be seen that, although the strut system (Figures 6 and '7) just described. has more component parts than the. simpler strut system. described previously, the principle of, operation, is exactly the same.

Whenthe various component-parts ofnthe mast. (offFigureii). have been joined'together whileon. the. ground. the. spider. bolts M. at the several junctions between thepostsectionslfil, I02; I93: and IM'are rotated to. bring the pairs-oispidfirs 3]? toward. each other. The. lowerjunction (betweenpost sections Iilhand; I02) and the upper junction (between post sections:I0-3-. and IIl4-) will operate exactly as: described in connection with together. andare.providedattheir:iunctioniwithr theflsimple mast-(Figures 1-3and8);

At the midjunction (between post sections I02 and I03) the adjustment of the two strut spiders 3|, however, will cause the two inner gusse shackles N3 of each inner strut connector I05 to move outwardly. The inner strut gusset plate I09 however will not move, being only loosely connected to the gusset shackles II3 during this operation. The outward movement of the said inner gusset shackles II3 will likewise cause outward movement of the extension struts I2 I, rigidly secured thereto, and of the outer gusset shackles I23, rigidly secured to said extension struts I2I. The outer strut gusset plate I21 during this operation will also be loosely connected and hence will not move outwardly. After the spiders 3| have been bolted into their stressed positions (as shown in Figure 6) the bolts joining the connector fins I I I, of the inner strut gusset plates I09, to the inner gusset shackles H3, and the bolts joining the connector fins I29, of the outer strut gusset plates I21, to the outer gusset shackles I23 will be tightened.

The three outer strut connectors I01 are joined to the three upper strut connectors 63 by three upper outer braces I35 and said outer strut connectors III? are similarly joined to the three lower strut connectors 63 by three lower outer braces I31.

The lower end of the'lowermost post section IN is joined to a base I39 by means of a ball and socket joint I4I. Said base I39 is concave on its under surface and is provided with sharp downwardly extending feet I43.

' The mast (Figure 5) is supported by three guys I45 which are preferably made of metal pipe and extend respectively from the three outer strut connectors IITI to three ground anchors I 4! secured in the ground equidistant from each other.

As shown in the drawings (Figure 5) the mast supports an antenna 85 by means of an extension post I5I rigidly secured to the upper end of the uppermost post section I04. Said extension post I5I and antenna 85 are sustained by three antenna braces I53 which respectively are secured at their lower ends to the upper strut connectors 03 and are strengthened by three nonadjustable fiat metal antenna struts I55 which extend outwardly from the lower end of the extension post I5I and are rigidly secured to said post and to the antenna braces I53.

The modified and more complicated form of the antenna just described (Figures 5-7) may be raised in any suitable manner. If it is to be raised as is the simpler form already described (Figure 4), it should preferably be provided with the T-shaped base II (as shown in Figure 1).

While there has been described what is at pres-' ent considered preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims, to cover all such changes and modifications as fall within the true spiritand scope of the invention.

What is claimed is:

1. In a mast, a vertically disposed central post, a strut system for said post including a spider longitudinally adjustable relative to said post and a stiff spider strut disposed obliquely to said post and pivotably secured at its inner end to said spider, means to adjust said spider longitudinally relative to said post, an upper brace secured at its lower end to the'outer end of said spider strut and secured at its upper end to the central post at a point higher than said strut system, and a lower brace secured at its upper end to the outer end of said spider strut and secured at its lower end to the central post at a point lower than said strut system.

2. In a mast, a vertical central post, a pair of strut spiders substantially concentric with said post and longitudinally adjustable relative thereto, each spider including a like plurality of legs extending substantially radially outwardly relative to said post, the legs of the spiders being disposed in pairs, each pair comprising a leg on the lower spider and a leg on the upper spider positioned substantially above it, means to adjust said spiders longitudinally relative to said post, a plurality of spider struts pivotably secured at their inner ends to said legs respectively so as to make up a plurality of pairs of spider struts, each pair comprising one spider strut substantially above another, a strut connector secured to the outer ends of the spider struts of each pair, a plurality of pairs of braces, each pair comprising a brace secured at its lower end to a strut connector and at its upper end'to the central post at a higher level and a brace secured at its upper end to said strut connector and at its lower end to the central post at a lower level, each of said strut connectors including a strut gusset plate horizontally adjustable relative to the balance of said connector, and a plurality of I struts joining the several strut gusset plates.

3. In a mast as defined in claim 2, a plurality of ground anchors disposed about the lower end of the central post and a plurality of guys connecting the several strut connectors to the several anchors.

4. In a mast, a vertical central post, a pair of strut spiders substantially concentric with said post and longitudinally adjustable relative thereto, each spider including a like plurality of legs extending substantially radially outwardly relative to said post, the legs of the spiders being disposed in pairs, each pair comprising a leg on the lower spider and a leg on the upper spider positioned substantially above it, a plurality of spider struts pivotably secured at their inner ends to said legs respectively so as to make up a plurality of pairs of spider struts, each pair comprising one spider strut substantially above another, a plurality of strut connectors, each strut connector comprising a horizontal strut gusset plate and two gusset shackles slidably secured to said plate respectively above and below it, said two gusset shackles respectively being pivotably secured to the outer ends of the spider struts of one pair thereof, a plurality of pairs of braces, each pair comprising a brace secured at its lower end to the upper gusset shackle of a strut conhector and at its upper end to the central post at a higher level and a brace secured at its upper end to the lower gusset shackle of said strut connector and at its lower end to the central post at a lower level, and a plurality of struts joining the several strut gusset, plates.

5. In a mast, a vertical tubular central post, two strut spiders adjustable longitudinally relative to said post, each strut spider comprising a central internally threaded sleeve longitudinally movable within said post and a plurality of outwardly extending legs, said legs respectively extending through longitudinal. slots in said central post, a plurality of outwardly extending still spider struts respectively pivotably secured to said legs, said spider struts being disposed in pairs one above the other, the outer ends of the spider struts of each such pair being pivotably secured respectively to a pair of gusset shackles, 'means for joining said gusset shackles of each pair, a brace joining the upper gusset shackle of each pair to the central post at a higher level, a brace joining the lower gusset shackle of each pair to the central post at a lower level, means to move the spiders longitudinally relative to the central post so as to move the gusset shackles outwardly from the post.

6. A mast as defined in claim 5, including struts connecting the several pairs of gusset shackles, the connections between the struts and shackles being slidable.

7. In a mast, a central post, a strut spider longitudinally adjustable relative to said post, an elongated brace member having its opposite ends secured to the post at two points spaced from each other, a stiff spider strut extending obliquely outwardly from said-post and pivotably secured 8. In a mast, a central post, a strut spider longitudinally adjustable relative to said post, a plurality of elongated, brace members having their opposite ends secured to the post at two points spaced from each other, a plurality of stiff spider struts extending obliquely outwardly from said I post and pivotably secured at the outer ends respectively to the brace members at points intermediate the ends of said brace members and pivotably secured. at their inner ends to the. strut spider, whereupon the spider may be adjusted to swing said spider struts and thereby increase the perpendicular distances from the post to the outer ends of said spider struts and thereby subject the brace members to tension and the post to compression.

9. In a mast, a vertical central post, three strut spiders longitudinally adjustable relative to said post, said spiders including a central spider disposed substantially at the central portion of said post, a lower spider disposed intermediate the lower end of said post and. the central portion thereof, and an upper spider disposed intermediate the central portion of said post and the upper end thereof, a plurality of lower elongated brace members having their opposite ends secured respectively to the lower end or the post and to the central portion of the post, a plurality of upper elongated brace members having their opposite ends secured respectively to the central portion of the post and to the upper end of the. post, a plurality of stiii lower spider struts pivotably secured at their inner ends to the lower spider and at their outer ends respectively to the lower brace members at points intermediate the ends of said lower brace members, a plurality of stiff upper spider struts pivotably secured at their inner ends to the upper spider and at their outer ends respectively to the upper brace members at points intermediate the ends of said upper brace members, a plurality of central elongated brace members having their opposite ends secured respectively to the outer ends of the lower spider struts and the outer ends of the upper spider struts, and a plurality of stiff central spider struts i2 pivotably secured at their inner ends to-the central spider and at their outer ends respectively secured to the central brace members at points intermediate the ends of said central brace members. y

10. In a mast as defined in claim 9 which in cludes a plurality of ground anchors and a plurality of guys extending from the said ground anchors up to the central brace members at points intermediate the ends of said central brace members. Y

11. The method of erecting a mast, of the type having a central post and three struts extending outward from the midportion of the post'and a three cornered base having pulley means at one corner and rotatable means at the other two corners to allow rotation of the mast about an axis extending through said other two corners, comprising the following steps? installing three ground anchors in the ground substantially at the points where the three corners of theibase are to rest when the mast is erected,'installing an auxiliary ground anchor at a point'so that the four anchors delineate the extremities of a cross, the distance between the said auxiliary anchor and the nearest of the other anchors being less than the distance between the base and struts of the mast, assembling the components of the mast upon the ground so that the two corners of the base provided with rotatable means are disposed at two of the anchors and the struts are adjacent a point above said auxiliary anchor and the pulley means is on the corner of the base extending upwardly, securing a chain hoist to the outer end of the upwardly extending strut, rum ning one free end of cable of said hoist over the pulley and down to the third ground anchor and securing it thereto, securing the other free end of cable of said hoist to a coil'spring, securing the other end of said spring to the auxiliary anchor, and operating the chain hoist so as to pull in the first free end of cable thereof and let out the other end. I

12. In a mast, a vertical central post, a strut extending obliquely, outwardly from said post, a

brace extending from the outerend of said strut up to the post, a second brace extending from the outer end. of said strut down to said post, means to swing'said strut toward a more nearly horizon tal position so as to lengthen the horizontal component of said strut and thereby subject said post to compression and prestress said braces, said means including a spider longitudinally movable relative to the post, the inner end of the stint being pivotally secured to said spider, and means to move said spider longitudinally relative to said post.

ERIC A. BLACK.

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

UNITED STATES PATENTS Number Name Date 125,771 Trego M Apr. 16, 1872 434,639 Maxwell Aug. 19, 1890 522,817 Zerfas July 10, 1894 845,242 Leidl Feb. 26, 1907 2,176,965 Haynes Got. 24, 1939 2,267,705 Athy Dec. 30, 1941 2,271,578 Woolslayer et al. -0..- Feb. 3, 1942 2,319,303 Crawford May 18, 1943 2,403,081 Hil qlfn .a July 2,1946