CA1110091A - Mine roof or rock bolt expansion anchor of the bail type - Google Patents
Mine roof or rock bolt expansion anchor of the bail typeInfo
- Publication number
- CA1110091A CA1110091A CA304,441A CA304441A CA1110091A CA 1110091 A CA1110091 A CA 1110091A CA 304441 A CA304441 A CA 304441A CA 1110091 A CA1110091 A CA 1110091A
- Authority
- CA
- Canada
- Prior art keywords
- leaves
- shell
- bolt
- striations
- bail
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000011435 rock Substances 0.000 title description 22
- 239000002184 metal Substances 0.000 claims abstract description 8
- 229910052751 metal Inorganic materials 0.000 claims abstract description 8
- 238000004873 anchoring Methods 0.000 claims description 14
- 230000000694 effects Effects 0.000 claims description 8
- 230000004323 axial length Effects 0.000 claims description 2
- 238000003892 spreading Methods 0.000 claims description 2
- 210000003141 lower extremity Anatomy 0.000 claims 7
- 210000001364 upper extremity Anatomy 0.000 claims 7
- 229920000136 polysorbate Polymers 0.000 abstract 1
- 238000004519 manufacturing process Methods 0.000 description 9
- 238000009434 installation Methods 0.000 description 6
- 239000002994 raw material Substances 0.000 description 4
- 238000009412 basement excavation Methods 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 229910001018 Cast iron Inorganic materials 0.000 description 1
- ONIBWKKTOPOVIA-BYPYZUCNSA-N L-Proline Chemical compound OC(=O)[C@@H]1CCCN1 ONIBWKKTOPOVIA-BYPYZUCNSA-N 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000013011 mating Effects 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
Landscapes
- Dowels (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A bail type expansion anchor for mine roofs and the like including a threaded bolt, and expander cone nut, and an ex-pansible shell assembled together, with the shell formed from an integral blank of sheet metal having a pair of initially flat rec-tangular leaves bent to semi-cylindrical configuration with side edges thereof in abutment with each other to define a complete cylinder and having a bail strap of U-shaped configuration extend-ing upwardly from the leaves and along side the cone nut. The bolt is threaded through the cone nut with the cone nut extending be-tween the leaves of the shell, and the bail portion of the shell includes a circular top portion having a pop-out center having an interrupted circular periphery of slightly larger diameter than the bolt aligned with the bolt and connected to the remainder of the bail by frangible uncut attachment sections, designed to be broken out from the bail upon predetermined rotation of the bolt and form an aperture for passage of the bolt therethrough.
A bail type expansion anchor for mine roofs and the like including a threaded bolt, and expander cone nut, and an ex-pansible shell assembled together, with the shell formed from an integral blank of sheet metal having a pair of initially flat rec-tangular leaves bent to semi-cylindrical configuration with side edges thereof in abutment with each other to define a complete cylinder and having a bail strap of U-shaped configuration extend-ing upwardly from the leaves and along side the cone nut. The bolt is threaded through the cone nut with the cone nut extending be-tween the leaves of the shell, and the bail portion of the shell includes a circular top portion having a pop-out center having an interrupted circular periphery of slightly larger diameter than the bolt aligned with the bolt and connected to the remainder of the bail by frangible uncut attachment sections, designed to be broken out from the bail upon predetermined rotation of the bolt and form an aperture for passage of the bolt therethrough.
Description
9~
BACKGROUND AND OBJECTS OF THE INVENTIOi!l I The present invention relates in general to mine roof or rock bolt expansion anchors, and more particularly to an improved 1lmine roof or rock bolt expansion anchor provided with means for S llquickly initially expanding the same in a mine roof bore hole to achieve initial anchorage for further manipulation to properly anchor it in place, and wher~in the anchor is formed with a shell land bail composed of a uniforrn thickness of one ~iece of metal ,lactivated by a cone nut threaded onto a bolt to expand the shell ¦into contact with the rock of the bore hole wall.
i! Roof suspension bolts or, as properly called, mine roof l~bolts~ are now widely used. In the use of these bolts, holes are drilled upwardly into the mine roof or cei]ing or into the over-1lhanging rock mass, in a mine or similar excavation, and supporting lS ,¦bolts, designed to be secured in the bore holes to ex~rt compres-sive force against the roof or to be direct~d throuyh supporting plates or bars engaged with the roof or ceiling, are inserted in ~jthe holes and anchored therein for securely su~porting the ~or-1ltions of the mine roof or ceiliny near the bolts. The anchoring 1 of the bolts is effected by employing an cY.pansion anchor, inser~ed 'into the roof bores and through ~Ihich the bolts arc i~hreaded.
Means are included in these ex?ansion anchors wnicll are cfcctive upon threading of the bolts inwardly to a ~rede-termined extent -to lexpand the shell portion of the anchors and cause them to firmly 1¦grip the wall portions of the bGlt receiving ~ores. It is the pur-pose of the present in~ention to provi~c a r~o~el form tor .sucn a mine roof or rock bolt expansion anc}lor w..ch ca1l bc casily ~Ind economically manufacturea, and which is su,Jject to being inscl~c~
¦into a receiving bore formed in the rock ccilin~ or 1-O0L ~"ith <~~eat 30 I facility and ca~able of ~cry securel;~ anc..vi- ng a bol~ th.caded ~~therethrou~h.
Such mine roof bolts as previously known usually consist of a long bolt provided with a multi-part permanent anchoring means on one end of the bolt to be expanded into secure retaining engagement with the side walls of the upper portion of a hole drilled in the roof of a deep mine, rock or other excavation. The anchoring means of conventional mine roof bolts presently in use are expandable, usually by manually driving the holt with an appropriate bolt rotating tool. A problem involved in the installation of conventional mine roof bolts resides in the fact that such bolts are inserted in a substantially vertical hole in the roof or ceiling of a mine passageway, and many mine roof bolts do not have provision for quickly achieving initial expansion to temporarily restrain the bolt in place, after it has been inserted to its full extent in the drilled hole in the mine roof, and consequently, difficulty is encountered in holding the bolt temporarily in the hole while sufficient torque is applied to the bolt to expand the anchor to permanent anchoring condition. It is rather difficult and requires a great deal of care on the part of a laborer to manually hold the bolt in place during the period required to manipulate an appropriate tool to expand the expandable anchoring means so that it reliably retains itself in place in the hole.
According to the present invention, there is provided an expansion anchor for mine roofs and the like including an expansible shell formed from an integral uni-tary blank of sheet metal having a pair of initially substan-tially rectangular leaves interconnected to each other at proximal ends thereof by a bail strap and free at the other ends thereof. The bail strap is bent to a U-shape and the leaves are bent to semi-cylindrical shape concentric with a l~lQ~l bolt axis with their side edges in mutual abutment defining a generally cylindrical exterior for engagement with the walls of a mine ceiling bore. The bail strap has an enlarged circular top portion midway along its length and straight narrow leg portions extending in parallelism therefrom to the proximal ends of the leaves. There is provided an expander cone nut having an internally threaded bore and located in confined relation between the leaves and between the leg portions and having a generally frusto conical outer surface convergently tapering to a small diameter end interposed between the leaves to abut the leaves and spread them out-wardly. A bolt is threaded through the cone nut for moving the nut downwardly in the shell and bring progressively larger diameter portions of the outer surface against the leaves for spreading the leaves outwardly. The circular top portion of the bail has a pop-out center formed by a pair of substantially semi-circular arcuate cuts therethrough defining a concentric circle interrupted by a pair of frangible uncut attachment sections. The pop-out center is of slightly larger diameter than the bolt and is aligned with and is adjacent the free end of the bolt to be abutted by the same and popped out upon predetermined rotation of the bolt so as to form an aperture for passage of the bolt through the top portion. The circular top portion of the bail strap which includes both the pop-out center and the remaining encircling portion is shaped in an upwardly convex cylindrical path having its axis of revolution passing through the bolt and located along the bolt axis at a position lying between the circular top portion and the proximal ends of the leaves and with the uncut attachment sections being arranged along a diametric axis parallel the axis of revolution of the cylindrical path to facilitate centering of the bolt relative to the circular top portion upon abutment thereof.
l~lQQ91 An object of the present invention, therefore, is the provision of a novel form of mine roof or rock bolt expansion anchor of the bail type which can be easily and economically manufactured, which is convenient to operate, and which is capable of providing highly reliable anchoring of a bolt in a hole formed in a mine roof or rock ceiling or the like.
tm/ ~ 3a l~QQ9t Another object of the present invention is the provision of a novel expansion bolt anchor of the bail type for mine roofs or similar installations formed so that the anchor will expand at a more rapid rate during initial turning of the bolt after the unit is placed within the bore hole and thereby achieve fast initial anchorage and which then expands at a slower rate upon further turning of the bolt, facilitating installation of the expansion anchor and providing highly reliable anchorage capacity.
Another object of the present invention is the provision of a novel expansion bolt anchor for mine roofs or ceilings and like installations, having high total anchorage capacity, wherein the anchor shell is designed with the two opposing leaves permitting utilization of raw material which can be conveniently purchased in coil form, minimizing the cost of shearing of the raw material and the cost of handling the raw material when compared to the use of individual strips, thereby offering a most economical method for production of the unit without welds or mechanical attachment of a bail to the shell which might break off or distort in production.
Another object of the present invention is the provision of a novel expansion bolt anchor for mine roofs or ceilings and the like to be inserted in bore holes formed in the rock or roof formation, wherein the cone nut is provided to be threaded on the bolt to be anchored in the bore hole and drawn between the opposite substantially semi-cylindrical leaves of the expandable shell formed initially as a one piece blank from a flat coil of metal raw material with the two leaves of the shell interconnected by the bail having a circular top which may be slightly cupped in manufacture and includes the pop-out portion which is Q(~91 i ,, I
, cdesiyned to break away under a speeified load when ~le end of the bolt is driv~ ayainst the pop-out yortion with sufficient load Il during advaneement of the bolt to fix the bolt anehoring assembly Il in tlle bor~ hole.
5 , Other objeets, advantages and eapabilities of the present invention will beeome,apparent from the following detailed deseription, taken in eonjunetion with the aeeompanying drawings illustratiny a preferred embodiment of tlle invention.
I BRI~F DESCRIPTION OF TIIE FIGURES
10 I FIGURE 1 is a perspeetive vie~ of a mine roof or roek bolt expansion anehor assembly eonstrueted in aeeordanee with the , present invention;
FIGURE 2 is a lonyitudinal seetional ViC~I throuc3h a mine eeiliny bore showing the bolt cxpansion anehor assem~ly in 15 I position 3-or beincj anehorecl in thc bore by turniny of the anehor bolt, the bolt expansion anehor asselr,bly l~einy shown in side elevationi FIGURE 3 is an elevation view of the bolt expansion ~ anehor assernbly, viewed frorn a position eireumferentially spaced 90~ from the elevation of Fic~ure 2j FIGURE 4 is a top plan vie~l 03- tnc expansion anehor assembly;
~ IGURE 5 is a vertieal seetion vic,~/ taken alony -thc ~ line 5-5 of Fiy. 4;
I-IG~RE 6 is a plan vie~ o~ thc ~la~ ori,lcc' I rc r~ thc~
~lat sheet rlaterial of eoil stoc,~ to pl-o~ldc t,:c s~i.~cve;
I'IGURE 7 is a vertieal seetion vic~ tilrouc,h thc CGIIC
nut; and FIGURE 8 is an end elevation view of the cone nut, lviewed from the larger diamcter end.
ii j DET~IL~D DESCRIPTION OF ~ PREFERRED EMBODIMENT
¦l Referring to the drawings, wherein like reference charac-5 ¦¦ ters designate corresponding parts throughout the several figures, ¦
¦Ithe bolt expansion anchor assembly of the present invention, indi-cated generally by the reference cl-aracter 10, is illustrated in Figure 2 in position in a section of a mine roof ceiling, indicated liat 11, inserted in a drilled bore hole 12 in which the assembly is ¦Ito be received and anchored. The anchoring assembly 10 is designed to serve as an anchor means to fix the bolt 13 in the bore hole, and in some applications, to extend through ard seat its head 14 ¦against a plate 15 which in turn supports the roof or ceiling, in l¦one typical installation.
~! The improved bolt expansion anchor assembly 10 may be ~generally described as including an integral shell, indicated at ~16, forrned for example from a flat blank of steel or similar metal of the shape illustrated in Figure 6 from material which can be llsupplied as coil stock, and includes a cone nut or expander plug 1l17, for example of forged steel or rnalleable cast iron, which, when the parts are completely shaped and prol~erly assemblfd, is l~held within the shell 16 against inadvertent fallout, in a Inanner j~to be described hereinafter.
The bolt 13 has the usual square or non-round head, I,indicated at 14 and an elongated round shank 13a with threads 13~
'extending from thc end portion over a major ~.~ortion of its length.
The cone nut 17 is of truncated conical contiguration over most of its axial lengtll, having a conically shapcd wall or surface portion ' 17a progressively enlarging in diameter from the smallfr end ]7b 30 I,to the larger diameter cylindrical shoulc~ie~r portion 17c at thc ., ~
~ ! .
',opposite end of the cone nut. The cone-shape surface portion 17a !land shoulder portion 17c are interrupted at diametrically opposite ¦
¦¦regions by bail slots or grooves 17d extending the entire axial l length of the cone nut 17 along longitudinal a~es parallel to the cone nut center axis to receive legs or sides of a bail portion of I
the shell 16 as later described. The cone nut 17 is designed with ¦
a center bore shaped to provide a beveled entrance 17e to facili-tate and guide entrance of a drill and tap ~uring n~anufacture to jlform threads 17f along the midregion of the bore, and is provided llalso with adequate clearance and an upper bevel, in the region 17g, !
to facilitate assembly of the bolt and anchor unit while still maintaining sufficient thread length along the region 17f to develop maximum strength of the bolt during tension. The base of the cone 'nut 17 is cut out as indicated at 17h to provide a pilot for pro-lS ¦Iperly aligning the cone nut in relation to the bail and leaves ofthe shell 16 during manufacture.
Il The anchor shell 16 is formed basically of a pair of leaves 18a, 18b which are of half cylinder form in the final assem-¦bly interconnected by a bail generally indicated at 19 having a I!circular top 20. The shell and bail element forming the leaves18a, 18b and the interconnecting bail 19 with its circular top portion 20 are composed of a unifor~ thickness of one ?iece of ,metal which is formed as a flat blank and permits economical pro-~uction from common, inexpensive ra~ r,ateria] which can be pur~ ~
Ichased in coil form. The t~lO opposing leaves 18a, 18b are initially ,substantially rectangular in confic,uration, havincJ straig}lt parallel side edyes 21a, 21b and 22a, 22b and havinc, a transvcrse bottom edge 23a, 23b interrupted by an elongated inset or shallow recess 24. The top edges 25a, 25b of the leaves 18a, 18b form straight l l l l l l transverse shoulders which merge into the bail sides formed by narrow, straight legs 26a, 26b extending from the leaves to the enlarged circular top 20. The enlarged circular top 20 is provided with a small hole 27 which is used as a pilot hole during manufacturing and serves to keep the bolt centered as it turns in contact with the bail during operation, as later described.
The circular top 20 of the bail structure also includes a pop-out center portion 28 formed by two substantially semi-circular cuts 29 concentric with the center of the hole 27 and the circular periphery of the circular top 20 but held in place until use by uncut or unsheared sections or inter-ruptions 3C at diametrically opposite locations. The unsheared sections 30 of the circular top are designed to break under a specified load and permit the circular center portion 28 defined by the cuts 29 to pop out of the circular top 20 as the bolt is initially turned sufficiently to butt the end of the bolt against the pop-out portion 28 and apply sufficient force to break the unsheared portions 30, and provide a hole of sufficient diameter to give the advancing bolt adequate clearance to pass through the circular hole left when the pop-out center 28 breaks out, while leaving the annular rim of the circular top of the bail which remains with sufficient strength to prevent any misalignment of the two leaves of the shell as the cone nut continues to draw down and expand the shell. The circular top 20 of the bail is slightly cupped in manufacture to assume the curYature illustrated in Fig. 2.
The pop-out center and the remaining encircling portion is shaped in an upwardly conYex cylindrical path having its axis of revolution passing through the bolt and located along the bolt axis at a position lying between the circular top portion and the proximal ends of the leaves 18a, 18b. By l~lQ~91 virtue of this geometry, the pop-out portion 28 can be sheared in manufacture without the necessity of cutting an opening in the metal which would let dirt fall into the cone nut threads. In addition, the cupped geometry of the circular top 20 of the bail facilitates entry of the unit into the bore hole while the curved geometry of the pop-out section 28 provides a - 8a -ll~Q~9~
self-eentering surfaee for eontaet with the top of the advaneiny bolt. The eireular top 20 o~ the bail Wit}-l no openings other than the small eenter pilot and guiding hole 27 WiliC}l is bloekc~d by the llbolt end in the assembled eondition of the unit ready for use, S llvirtually fills the entire bore hole thereby preventin~ dirt and ,¦dust from falling into the eone nut and interferring with the in-ternal threads. This results in more eonsistent bolt torque and therefore better eontrol of the tension in the bolt as measured ,Iby tne to~que required for proper installation.
¦I The thiekness of the material used to form the shell mak-ing up the leaves 18a, 18b and the bail 19 witll its eireular top llportion 20 is ealeulated as that maximum amount, cJiven the diameter ,~of the bore hole, whieh subtraeted from thc diameter of the eone Inut or ~lug 17 in order to provicle for the bail slots 17d in the l'eone nut for the bail lec~s 26a, 26b, would lcave suf.ieient wall thiekness bct~Jecn thc bail slots 17cl of thc eonc nut and the inter-lnal threads thereof to prevent eollapse of the eone nut under load.Tne perforrrlanee of the anehor is der~endent u~,on the cotal expansion lleapaeity of the shell whieh in turn is cieterl,line~ the rna~imum 20 1l diameter of the eone nut, the thie~llcss OL Lihe e~p(~.~sioll shell, and the elevation of the striations ~J~.iC}l ~ JC ;-OrlllC'~ in t.lC 1 f`aVCS
of the shell as later 'eseri,)e~i.
~Lhe t~o sides or le~s 26a, 2~ o-. thf `~ ' a.e ~iesi~ne~l llof minim~in ~iidth ~hieh pcrmit~ it~ thc i~hlr;~Aicss ar~i ml?rri,ll 11 us~d, rl(if->~ tr~ str~ Jth to hold th~ t~o lc..~c~s 1,',a, 18b o~ thc shell in proper aJi~nme.lt throuahout the :~roccss G- in'jf`i-'LlOn ln thc ibOr~f`~
Iholc a~(3 ci~ sion of tii~ ~sscrrbly. ,~ - Uf~ o.~ :~c~ < his '. icith ;lat a mirlimu;n, the bail slots l7(~ in },} C~O;~r ;~ !7 .-c ~.ccr?~lscc to thei:L rrlirirlJ-l ,r~ic7ith/ thcreby lr,ercas~ thl jor'io.-. o~~ I. circim-'.
' l, :
Iference of the cone nut which is available for expanding the twoleaves of the shell.
The two sides or legs 26a, 2Gb of tihe bail 19 offer a ¦convenient place for the manufacturer to stamp the hole diameter S ¦iand manufacturer's identification required by government specifica-¦¦tions for roof and rock bolt anchorage devices. Since these bailsides or legs 26a, 26b are of one piece integral with the leaves ¦18a, 18b of the shell, these inforrnation stampings can be stamped ,Iduring the forming process in an economical manner. The entire ¦Ibail 19, compos~d of the circular top 20 with its pop-out center ¦section 28 and the two bail legs or sides 26a, 26b, by virtue of being integral with and composed of the same rnaterial as the two leaves 18a, 18b of the shell, offer tne most economical method for !
Illproduction of the unit, since no welds or a mechanical attachment 15 !: f the bail to the shell which might break off or distort in pro-l,duction or utilization are involved and facilitates minimizing ¦Ico5t of assembly for the expansion anchor unit.
~I The two leaves 18a, 18b of the anchor shell 16 are ¦¦swaged in the region 32 transversely across the width of each leaf 20 11 adjacent the shoulder or top edge portion 25a, 25b ~o provide a lseat for the cone nut 17. By virtue of this swaged section 32, ¦the bottom or minimal diameter of the smaller end 17b of the cone Znut 17 can be increased, thereby decreasing the ta-per of the cone ' IZInut side 17a over a given length. Minimizing this taper decreases 25 ¦11 the effect of bleed-off or the tendency o the bolt and anchor assembly to lose tension over time. The s~aced section 32 also increases the rate of initial expansion as the cone nut 17 cdra~Js ~do~n into the shell 16, permitting the anchor to take a rapid ini-tial set with minimal movement of the unit wi~hin the borc hole and ' ' , , ~ --1 0--! , `I 1110~91 ~ ` ~
l,thereby minimal disturbance of the supporting rock comprising the j~bore hole wall. The length of the bail sides or legs 26a, 26b is designed as that minimum for economic construction and minimization llof scrap which will still permit clearance for the cone nut 17, lltaking into consideration the swaged seat section 32 on the leaves 18a, 18b of the shell 16 which keeps the cone nut from misaligning prior to its engagement and starts the expansion of the shell as the cone nut 17 starts its downward travel.
!¦ During manufacture, the two leaves 18a, 18b of the shell 1116 are coined at multiple points to raise striations or pointed jdeformations 33 on the exterior of the shell across the entire width of the two opposing leaves so that they will be aligned when !
the shell is formed into final shape. This coinincJ operation ~Iprovides the striations or external deformations 33 at the lowest llpossible cost of manufacture, and by virtue of the coining opera-lltion, the striations can be formed with no interruption across the j ¦entire ~idth of the leaves, thereby permitting formation of sub-llstantially full 360 circular striations in the final assernbly to ¦!bite into the bore hole wall. The width of the coined deformations lon the interior surface of the leaves ?rovicling the striations 33 lare designed as that minimum which will still permit full forma-ltion of the required striations 33 on the c~terior of the shell 'I
¦while the cylindrical shoulder portion 17c of thc cone nut is des- ' ¦igned to be of sufficient axial length to bridge the coined defor- j ~!
i,mations for the striations 33 at the interior su~face of the leaves~
¦'18a, l~b, thereby maintainincJ smooth and cor.tinuous e~pansion of the anchor uni-t as the cone nut is dra-Tn down into the shell. Thc first two striations 33a, 33b on the exterior of the shell 1~ are desigried with a geometry providing shear strcngth a;JprGxi"matel~
, I , ~, ,1 , ~ 110~9~
jl i equal to the average shear strength of the rock in the bore hole wall between the two striations 33a, 33b, to permit maximum utili-zation of the strength of the undisturbed rock in the bore hole ¦wall, thereby increasing the total anchorage capacity of the unit.
The final striation 33c is designed with a wider base dimension than those at 33a and 33b, an~ the slope of the striation 33c is decreased making this striation harder to press into the bore hole wall than the sharper striations at 33a and 33b. This increase in~
'difficulty with which the striation 33c enters the bore hole wall !
¦loffers increased resistance to the downward travel of the cone nut ~17 thereby increasing the tension placed in the bolt during the ~,final stages of tightening. The striations 33 are placed far ¦! enough apart to prevent crushing of the rock in the bore hole wall !¦as the striations bite into the rock, thereby offering the maximuml ¦undisturbed rock for support of the anchor unit. The height of the striations 33 are designed to be the minimum which will offer ade-~j quate strength to bite into the bore hole wall and contribute to 1 maximum anchorage capacity and that maximum height which when ¦¦ added to the thickness of the shell wall and formed into a cylinder jwill permit adequate clearance or the bolt and cone nut during ! both assembly and expansion of the unit. I
In forming the complete bail type expansion anchor assem-¦ bly ready for use, the two leaves 18a, 18b of the flat blank for I the anchor shell 16 are first formed into hal~ cylinders, and the ! shell blank is then bent about the central circular top portion 20j ! to deform the outer rim portion of the circular to? to the slightly ~ cupped or arched configuration illustra~ed in Figure 2 a.~d cause j the center pop-out portion 28 to assume a corresponding arched configuration, and the bail legs or sides 26a and 26b are bent l! l nsl ' downwardly in the region where they join ti~c circular top 20 to seat them in the bail slots 17d of the cone nut 17 and bring the Illside edyes 21a, 21b of the half cylinder shaped leaves 18a, 18b !1 into contact with each other. The sides or legs 26a, 26b of the llbail 19 are bent inwardly at 26c to provide slightly inwardly con-¦Iver~ing lower leg portions in order to insure a tight closure of the mating edges of the half-cylindrical leaves while still allow-ling free do~nward travel of the tapered cone nut 17. By thus fold-lling the shell to form the half cylinder shaped leaves 18a, 18b in-l¦to a full cylinder shape, full 360 contact of the leaves of theshell with the bore hole wall are permitted, thereby increasing the total anchorage capacity of the assembly when compared to ' anchors of the ty~es havin~ three or four leaves l,l In utilization, the bail type expansion anchor assembly j 15 ll comprising the assembled cone nut 17 ~nd shell 16 is threaded loosel~ onto the ends of the mine roof or rock bolt 13 to thread the shank of the bolt 13 into the th~eaded pOrtiGn 17f of the cone jnut 17 and this assembly is then inscrted into an appropriate dia-llmeter hole drilled in the roof of the mine or into the rock or 20 ,lother excavation in which the anchor is to be installed. The bolt;
13 is then turned, advancing it through the threadecl cone nut 17 until the threaded end of the bolt 13 con~ac'~s trle circular top 20 of the bail 19. This contact prevents furthcr mover~ient of the Il,shell 16 in relation to the bolt 13. Uporl continued turning of the 25 1l bolt 13, the cone nut 17 is drawn down into the shcll 16, thereby 'expanding -the anchor into contact ~ith tnc rock OJ~ +he bore hole ~all. .~ftcr initial anchorage i~ achi~ , thc c~ c~ ior~ion _~ ' of .he ~ail 1~ pcps out at a predeterrnl;led~ Joad c.~crted !~ r,c top, l o the bolt. This then permits the shank of tr.e b~ .3 io pass thro~gh the circular top 20 of the shell lf, as i~: is fur~ cf O tighterled b~ rotating the head 14 ir~ ofder to e~ r af,rlro;~rla~( compressive ~orce against the roof o.- ~_he ;~ c o~ aivat:lon aild ' ' ~
9~
place appropriate tension in the bolt in order to secure the rock ~mass. Durin~ this further tightening, the cone nut 17 continues -to pull into and expand the shell 16 which is now prevented from moving by its initial anchorage in the bore hole wall.
, , , -14-
BACKGROUND AND OBJECTS OF THE INVENTIOi!l I The present invention relates in general to mine roof or rock bolt expansion anchors, and more particularly to an improved 1lmine roof or rock bolt expansion anchor provided with means for S llquickly initially expanding the same in a mine roof bore hole to achieve initial anchorage for further manipulation to properly anchor it in place, and wher~in the anchor is formed with a shell land bail composed of a uniforrn thickness of one ~iece of metal ,lactivated by a cone nut threaded onto a bolt to expand the shell ¦into contact with the rock of the bore hole wall.
i! Roof suspension bolts or, as properly called, mine roof l~bolts~ are now widely used. In the use of these bolts, holes are drilled upwardly into the mine roof or cei]ing or into the over-1lhanging rock mass, in a mine or similar excavation, and supporting lS ,¦bolts, designed to be secured in the bore holes to ex~rt compres-sive force against the roof or to be direct~d throuyh supporting plates or bars engaged with the roof or ceiling, are inserted in ~jthe holes and anchored therein for securely su~porting the ~or-1ltions of the mine roof or ceiliny near the bolts. The anchoring 1 of the bolts is effected by employing an cY.pansion anchor, inser~ed 'into the roof bores and through ~Ihich the bolts arc i~hreaded.
Means are included in these ex?ansion anchors wnicll are cfcctive upon threading of the bolts inwardly to a ~rede-termined extent -to lexpand the shell portion of the anchors and cause them to firmly 1¦grip the wall portions of the bGlt receiving ~ores. It is the pur-pose of the present in~ention to provi~c a r~o~el form tor .sucn a mine roof or rock bolt expansion anc}lor w..ch ca1l bc casily ~Ind economically manufacturea, and which is su,Jject to being inscl~c~
¦into a receiving bore formed in the rock ccilin~ or 1-O0L ~"ith <~~eat 30 I facility and ca~able of ~cry securel;~ anc..vi- ng a bol~ th.caded ~~therethrou~h.
Such mine roof bolts as previously known usually consist of a long bolt provided with a multi-part permanent anchoring means on one end of the bolt to be expanded into secure retaining engagement with the side walls of the upper portion of a hole drilled in the roof of a deep mine, rock or other excavation. The anchoring means of conventional mine roof bolts presently in use are expandable, usually by manually driving the holt with an appropriate bolt rotating tool. A problem involved in the installation of conventional mine roof bolts resides in the fact that such bolts are inserted in a substantially vertical hole in the roof or ceiling of a mine passageway, and many mine roof bolts do not have provision for quickly achieving initial expansion to temporarily restrain the bolt in place, after it has been inserted to its full extent in the drilled hole in the mine roof, and consequently, difficulty is encountered in holding the bolt temporarily in the hole while sufficient torque is applied to the bolt to expand the anchor to permanent anchoring condition. It is rather difficult and requires a great deal of care on the part of a laborer to manually hold the bolt in place during the period required to manipulate an appropriate tool to expand the expandable anchoring means so that it reliably retains itself in place in the hole.
According to the present invention, there is provided an expansion anchor for mine roofs and the like including an expansible shell formed from an integral uni-tary blank of sheet metal having a pair of initially substan-tially rectangular leaves interconnected to each other at proximal ends thereof by a bail strap and free at the other ends thereof. The bail strap is bent to a U-shape and the leaves are bent to semi-cylindrical shape concentric with a l~lQ~l bolt axis with their side edges in mutual abutment defining a generally cylindrical exterior for engagement with the walls of a mine ceiling bore. The bail strap has an enlarged circular top portion midway along its length and straight narrow leg portions extending in parallelism therefrom to the proximal ends of the leaves. There is provided an expander cone nut having an internally threaded bore and located in confined relation between the leaves and between the leg portions and having a generally frusto conical outer surface convergently tapering to a small diameter end interposed between the leaves to abut the leaves and spread them out-wardly. A bolt is threaded through the cone nut for moving the nut downwardly in the shell and bring progressively larger diameter portions of the outer surface against the leaves for spreading the leaves outwardly. The circular top portion of the bail has a pop-out center formed by a pair of substantially semi-circular arcuate cuts therethrough defining a concentric circle interrupted by a pair of frangible uncut attachment sections. The pop-out center is of slightly larger diameter than the bolt and is aligned with and is adjacent the free end of the bolt to be abutted by the same and popped out upon predetermined rotation of the bolt so as to form an aperture for passage of the bolt through the top portion. The circular top portion of the bail strap which includes both the pop-out center and the remaining encircling portion is shaped in an upwardly convex cylindrical path having its axis of revolution passing through the bolt and located along the bolt axis at a position lying between the circular top portion and the proximal ends of the leaves and with the uncut attachment sections being arranged along a diametric axis parallel the axis of revolution of the cylindrical path to facilitate centering of the bolt relative to the circular top portion upon abutment thereof.
l~lQQ91 An object of the present invention, therefore, is the provision of a novel form of mine roof or rock bolt expansion anchor of the bail type which can be easily and economically manufactured, which is convenient to operate, and which is capable of providing highly reliable anchoring of a bolt in a hole formed in a mine roof or rock ceiling or the like.
tm/ ~ 3a l~QQ9t Another object of the present invention is the provision of a novel expansion bolt anchor of the bail type for mine roofs or similar installations formed so that the anchor will expand at a more rapid rate during initial turning of the bolt after the unit is placed within the bore hole and thereby achieve fast initial anchorage and which then expands at a slower rate upon further turning of the bolt, facilitating installation of the expansion anchor and providing highly reliable anchorage capacity.
Another object of the present invention is the provision of a novel expansion bolt anchor for mine roofs or ceilings and like installations, having high total anchorage capacity, wherein the anchor shell is designed with the two opposing leaves permitting utilization of raw material which can be conveniently purchased in coil form, minimizing the cost of shearing of the raw material and the cost of handling the raw material when compared to the use of individual strips, thereby offering a most economical method for production of the unit without welds or mechanical attachment of a bail to the shell which might break off or distort in production.
Another object of the present invention is the provision of a novel expansion bolt anchor for mine roofs or ceilings and the like to be inserted in bore holes formed in the rock or roof formation, wherein the cone nut is provided to be threaded on the bolt to be anchored in the bore hole and drawn between the opposite substantially semi-cylindrical leaves of the expandable shell formed initially as a one piece blank from a flat coil of metal raw material with the two leaves of the shell interconnected by the bail having a circular top which may be slightly cupped in manufacture and includes the pop-out portion which is Q(~91 i ,, I
, cdesiyned to break away under a speeified load when ~le end of the bolt is driv~ ayainst the pop-out yortion with sufficient load Il during advaneement of the bolt to fix the bolt anehoring assembly Il in tlle bor~ hole.
5 , Other objeets, advantages and eapabilities of the present invention will beeome,apparent from the following detailed deseription, taken in eonjunetion with the aeeompanying drawings illustratiny a preferred embodiment of tlle invention.
I BRI~F DESCRIPTION OF TIIE FIGURES
10 I FIGURE 1 is a perspeetive vie~ of a mine roof or roek bolt expansion anehor assembly eonstrueted in aeeordanee with the , present invention;
FIGURE 2 is a lonyitudinal seetional ViC~I throuc3h a mine eeiliny bore showing the bolt cxpansion anehor assem~ly in 15 I position 3-or beincj anehorecl in thc bore by turniny of the anehor bolt, the bolt expansion anehor asselr,bly l~einy shown in side elevationi FIGURE 3 is an elevation view of the bolt expansion ~ anehor assernbly, viewed frorn a position eireumferentially spaced 90~ from the elevation of Fic~ure 2j FIGURE 4 is a top plan vie~l 03- tnc expansion anehor assembly;
~ IGURE 5 is a vertieal seetion vic,~/ taken alony -thc ~ line 5-5 of Fiy. 4;
I-IG~RE 6 is a plan vie~ o~ thc ~la~ ori,lcc' I rc r~ thc~
~lat sheet rlaterial of eoil stoc,~ to pl-o~ldc t,:c s~i.~cve;
I'IGURE 7 is a vertieal seetion vic~ tilrouc,h thc CGIIC
nut; and FIGURE 8 is an end elevation view of the cone nut, lviewed from the larger diamcter end.
ii j DET~IL~D DESCRIPTION OF ~ PREFERRED EMBODIMENT
¦l Referring to the drawings, wherein like reference charac-5 ¦¦ ters designate corresponding parts throughout the several figures, ¦
¦Ithe bolt expansion anchor assembly of the present invention, indi-cated generally by the reference cl-aracter 10, is illustrated in Figure 2 in position in a section of a mine roof ceiling, indicated liat 11, inserted in a drilled bore hole 12 in which the assembly is ¦Ito be received and anchored. The anchoring assembly 10 is designed to serve as an anchor means to fix the bolt 13 in the bore hole, and in some applications, to extend through ard seat its head 14 ¦against a plate 15 which in turn supports the roof or ceiling, in l¦one typical installation.
~! The improved bolt expansion anchor assembly 10 may be ~generally described as including an integral shell, indicated at ~16, forrned for example from a flat blank of steel or similar metal of the shape illustrated in Figure 6 from material which can be llsupplied as coil stock, and includes a cone nut or expander plug 1l17, for example of forged steel or rnalleable cast iron, which, when the parts are completely shaped and prol~erly assemblfd, is l~held within the shell 16 against inadvertent fallout, in a Inanner j~to be described hereinafter.
The bolt 13 has the usual square or non-round head, I,indicated at 14 and an elongated round shank 13a with threads 13~
'extending from thc end portion over a major ~.~ortion of its length.
The cone nut 17 is of truncated conical contiguration over most of its axial lengtll, having a conically shapcd wall or surface portion ' 17a progressively enlarging in diameter from the smallfr end ]7b 30 I,to the larger diameter cylindrical shoulc~ie~r portion 17c at thc ., ~
~ ! .
',opposite end of the cone nut. The cone-shape surface portion 17a !land shoulder portion 17c are interrupted at diametrically opposite ¦
¦¦regions by bail slots or grooves 17d extending the entire axial l length of the cone nut 17 along longitudinal a~es parallel to the cone nut center axis to receive legs or sides of a bail portion of I
the shell 16 as later described. The cone nut 17 is designed with ¦
a center bore shaped to provide a beveled entrance 17e to facili-tate and guide entrance of a drill and tap ~uring n~anufacture to jlform threads 17f along the midregion of the bore, and is provided llalso with adequate clearance and an upper bevel, in the region 17g, !
to facilitate assembly of the bolt and anchor unit while still maintaining sufficient thread length along the region 17f to develop maximum strength of the bolt during tension. The base of the cone 'nut 17 is cut out as indicated at 17h to provide a pilot for pro-lS ¦Iperly aligning the cone nut in relation to the bail and leaves ofthe shell 16 during manufacture.
Il The anchor shell 16 is formed basically of a pair of leaves 18a, 18b which are of half cylinder form in the final assem-¦bly interconnected by a bail generally indicated at 19 having a I!circular top 20. The shell and bail element forming the leaves18a, 18b and the interconnecting bail 19 with its circular top portion 20 are composed of a unifor~ thickness of one ?iece of ,metal which is formed as a flat blank and permits economical pro-~uction from common, inexpensive ra~ r,ateria] which can be pur~ ~
Ichased in coil form. The t~lO opposing leaves 18a, 18b are initially ,substantially rectangular in confic,uration, havincJ straig}lt parallel side edyes 21a, 21b and 22a, 22b and havinc, a transvcrse bottom edge 23a, 23b interrupted by an elongated inset or shallow recess 24. The top edges 25a, 25b of the leaves 18a, 18b form straight l l l l l l transverse shoulders which merge into the bail sides formed by narrow, straight legs 26a, 26b extending from the leaves to the enlarged circular top 20. The enlarged circular top 20 is provided with a small hole 27 which is used as a pilot hole during manufacturing and serves to keep the bolt centered as it turns in contact with the bail during operation, as later described.
The circular top 20 of the bail structure also includes a pop-out center portion 28 formed by two substantially semi-circular cuts 29 concentric with the center of the hole 27 and the circular periphery of the circular top 20 but held in place until use by uncut or unsheared sections or inter-ruptions 3C at diametrically opposite locations. The unsheared sections 30 of the circular top are designed to break under a specified load and permit the circular center portion 28 defined by the cuts 29 to pop out of the circular top 20 as the bolt is initially turned sufficiently to butt the end of the bolt against the pop-out portion 28 and apply sufficient force to break the unsheared portions 30, and provide a hole of sufficient diameter to give the advancing bolt adequate clearance to pass through the circular hole left when the pop-out center 28 breaks out, while leaving the annular rim of the circular top of the bail which remains with sufficient strength to prevent any misalignment of the two leaves of the shell as the cone nut continues to draw down and expand the shell. The circular top 20 of the bail is slightly cupped in manufacture to assume the curYature illustrated in Fig. 2.
The pop-out center and the remaining encircling portion is shaped in an upwardly conYex cylindrical path having its axis of revolution passing through the bolt and located along the bolt axis at a position lying between the circular top portion and the proximal ends of the leaves 18a, 18b. By l~lQ~91 virtue of this geometry, the pop-out portion 28 can be sheared in manufacture without the necessity of cutting an opening in the metal which would let dirt fall into the cone nut threads. In addition, the cupped geometry of the circular top 20 of the bail facilitates entry of the unit into the bore hole while the curved geometry of the pop-out section 28 provides a - 8a -ll~Q~9~
self-eentering surfaee for eontaet with the top of the advaneiny bolt. The eireular top 20 o~ the bail Wit}-l no openings other than the small eenter pilot and guiding hole 27 WiliC}l is bloekc~d by the llbolt end in the assembled eondition of the unit ready for use, S llvirtually fills the entire bore hole thereby preventin~ dirt and ,¦dust from falling into the eone nut and interferring with the in-ternal threads. This results in more eonsistent bolt torque and therefore better eontrol of the tension in the bolt as measured ,Iby tne to~que required for proper installation.
¦I The thiekness of the material used to form the shell mak-ing up the leaves 18a, 18b and the bail 19 witll its eireular top llportion 20 is ealeulated as that maximum amount, cJiven the diameter ,~of the bore hole, whieh subtraeted from thc diameter of the eone Inut or ~lug 17 in order to provicle for the bail slots 17d in the l'eone nut for the bail lec~s 26a, 26b, would lcave suf.ieient wall thiekness bct~Jecn thc bail slots 17cl of thc eonc nut and the inter-lnal threads thereof to prevent eollapse of the eone nut under load.Tne perforrrlanee of the anehor is der~endent u~,on the cotal expansion lleapaeity of the shell whieh in turn is cieterl,line~ the rna~imum 20 1l diameter of the eone nut, the thie~llcss OL Lihe e~p(~.~sioll shell, and the elevation of the striations ~J~.iC}l ~ JC ;-OrlllC'~ in t.lC 1 f`aVCS
of the shell as later 'eseri,)e~i.
~Lhe t~o sides or le~s 26a, 2~ o-. thf `~ ' a.e ~iesi~ne~l llof minim~in ~iidth ~hieh pcrmit~ it~ thc i~hlr;~Aicss ar~i ml?rri,ll 11 us~d, rl(if->~ tr~ str~ Jth to hold th~ t~o lc..~c~s 1,',a, 18b o~ thc shell in proper aJi~nme.lt throuahout the :~roccss G- in'jf`i-'LlOn ln thc ibOr~f`~
Iholc a~(3 ci~ sion of tii~ ~sscrrbly. ,~ - Uf~ o.~ :~c~ < his '. icith ;lat a mirlimu;n, the bail slots l7(~ in },} C~O;~r ;~ !7 .-c ~.ccr?~lscc to thei:L rrlirirlJ-l ,r~ic7ith/ thcreby lr,ercas~ thl jor'io.-. o~~ I. circim-'.
' l, :
Iference of the cone nut which is available for expanding the twoleaves of the shell.
The two sides or legs 26a, 2Gb of tihe bail 19 offer a ¦convenient place for the manufacturer to stamp the hole diameter S ¦iand manufacturer's identification required by government specifica-¦¦tions for roof and rock bolt anchorage devices. Since these bailsides or legs 26a, 26b are of one piece integral with the leaves ¦18a, 18b of the shell, these inforrnation stampings can be stamped ,Iduring the forming process in an economical manner. The entire ¦Ibail 19, compos~d of the circular top 20 with its pop-out center ¦section 28 and the two bail legs or sides 26a, 26b, by virtue of being integral with and composed of the same rnaterial as the two leaves 18a, 18b of the shell, offer tne most economical method for !
Illproduction of the unit, since no welds or a mechanical attachment 15 !: f the bail to the shell which might break off or distort in pro-l,duction or utilization are involved and facilitates minimizing ¦Ico5t of assembly for the expansion anchor unit.
~I The two leaves 18a, 18b of the anchor shell 16 are ¦¦swaged in the region 32 transversely across the width of each leaf 20 11 adjacent the shoulder or top edge portion 25a, 25b ~o provide a lseat for the cone nut 17. By virtue of this swaged section 32, ¦the bottom or minimal diameter of the smaller end 17b of the cone Znut 17 can be increased, thereby decreasing the ta-per of the cone ' IZInut side 17a over a given length. Minimizing this taper decreases 25 ¦11 the effect of bleed-off or the tendency o the bolt and anchor assembly to lose tension over time. The s~aced section 32 also increases the rate of initial expansion as the cone nut 17 cdra~Js ~do~n into the shell 16, permitting the anchor to take a rapid ini-tial set with minimal movement of the unit wi~hin the borc hole and ' ' , , ~ --1 0--! , `I 1110~91 ~ ` ~
l,thereby minimal disturbance of the supporting rock comprising the j~bore hole wall. The length of the bail sides or legs 26a, 26b is designed as that minimum for economic construction and minimization llof scrap which will still permit clearance for the cone nut 17, lltaking into consideration the swaged seat section 32 on the leaves 18a, 18b of the shell 16 which keeps the cone nut from misaligning prior to its engagement and starts the expansion of the shell as the cone nut 17 starts its downward travel.
!¦ During manufacture, the two leaves 18a, 18b of the shell 1116 are coined at multiple points to raise striations or pointed jdeformations 33 on the exterior of the shell across the entire width of the two opposing leaves so that they will be aligned when !
the shell is formed into final shape. This coinincJ operation ~Iprovides the striations or external deformations 33 at the lowest llpossible cost of manufacture, and by virtue of the coining opera-lltion, the striations can be formed with no interruption across the j ¦entire ~idth of the leaves, thereby permitting formation of sub-llstantially full 360 circular striations in the final assernbly to ¦!bite into the bore hole wall. The width of the coined deformations lon the interior surface of the leaves ?rovicling the striations 33 lare designed as that minimum which will still permit full forma-ltion of the required striations 33 on the c~terior of the shell 'I
¦while the cylindrical shoulder portion 17c of thc cone nut is des- ' ¦igned to be of sufficient axial length to bridge the coined defor- j ~!
i,mations for the striations 33 at the interior su~face of the leaves~
¦'18a, l~b, thereby maintainincJ smooth and cor.tinuous e~pansion of the anchor uni-t as the cone nut is dra-Tn down into the shell. Thc first two striations 33a, 33b on the exterior of the shell 1~ are desigried with a geometry providing shear strcngth a;JprGxi"matel~
, I , ~, ,1 , ~ 110~9~
jl i equal to the average shear strength of the rock in the bore hole wall between the two striations 33a, 33b, to permit maximum utili-zation of the strength of the undisturbed rock in the bore hole ¦wall, thereby increasing the total anchorage capacity of the unit.
The final striation 33c is designed with a wider base dimension than those at 33a and 33b, an~ the slope of the striation 33c is decreased making this striation harder to press into the bore hole wall than the sharper striations at 33a and 33b. This increase in~
'difficulty with which the striation 33c enters the bore hole wall !
¦loffers increased resistance to the downward travel of the cone nut ~17 thereby increasing the tension placed in the bolt during the ~,final stages of tightening. The striations 33 are placed far ¦! enough apart to prevent crushing of the rock in the bore hole wall !¦as the striations bite into the rock, thereby offering the maximuml ¦undisturbed rock for support of the anchor unit. The height of the striations 33 are designed to be the minimum which will offer ade-~j quate strength to bite into the bore hole wall and contribute to 1 maximum anchorage capacity and that maximum height which when ¦¦ added to the thickness of the shell wall and formed into a cylinder jwill permit adequate clearance or the bolt and cone nut during ! both assembly and expansion of the unit. I
In forming the complete bail type expansion anchor assem-¦ bly ready for use, the two leaves 18a, 18b of the flat blank for I the anchor shell 16 are first formed into hal~ cylinders, and the ! shell blank is then bent about the central circular top portion 20j ! to deform the outer rim portion of the circular to? to the slightly ~ cupped or arched configuration illustra~ed in Figure 2 a.~d cause j the center pop-out portion 28 to assume a corresponding arched configuration, and the bail legs or sides 26a and 26b are bent l! l nsl ' downwardly in the region where they join ti~c circular top 20 to seat them in the bail slots 17d of the cone nut 17 and bring the Illside edyes 21a, 21b of the half cylinder shaped leaves 18a, 18b !1 into contact with each other. The sides or legs 26a, 26b of the llbail 19 are bent inwardly at 26c to provide slightly inwardly con-¦Iver~ing lower leg portions in order to insure a tight closure of the mating edges of the half-cylindrical leaves while still allow-ling free do~nward travel of the tapered cone nut 17. By thus fold-lling the shell to form the half cylinder shaped leaves 18a, 18b in-l¦to a full cylinder shape, full 360 contact of the leaves of theshell with the bore hole wall are permitted, thereby increasing the total anchorage capacity of the assembly when compared to ' anchors of the ty~es havin~ three or four leaves l,l In utilization, the bail type expansion anchor assembly j 15 ll comprising the assembled cone nut 17 ~nd shell 16 is threaded loosel~ onto the ends of the mine roof or rock bolt 13 to thread the shank of the bolt 13 into the th~eaded pOrtiGn 17f of the cone jnut 17 and this assembly is then inscrted into an appropriate dia-llmeter hole drilled in the roof of the mine or into the rock or 20 ,lother excavation in which the anchor is to be installed. The bolt;
13 is then turned, advancing it through the threadecl cone nut 17 until the threaded end of the bolt 13 con~ac'~s trle circular top 20 of the bail 19. This contact prevents furthcr mover~ient of the Il,shell 16 in relation to the bolt 13. Uporl continued turning of the 25 1l bolt 13, the cone nut 17 is drawn down into the shcll 16, thereby 'expanding -the anchor into contact ~ith tnc rock OJ~ +he bore hole ~all. .~ftcr initial anchorage i~ achi~ , thc c~ c~ ior~ion _~ ' of .he ~ail 1~ pcps out at a predeterrnl;led~ Joad c.~crted !~ r,c top, l o the bolt. This then permits the shank of tr.e b~ .3 io pass thro~gh the circular top 20 of the shell lf, as i~: is fur~ cf O tighterled b~ rotating the head 14 ir~ ofder to e~ r af,rlro;~rla~( compressive ~orce against the roof o.- ~_he ;~ c o~ aivat:lon aild ' ' ~
9~
place appropriate tension in the bolt in order to secure the rock ~mass. Durin~ this further tightening, the cone nut 17 continues -to pull into and expand the shell 16 which is now prevented from moving by its initial anchorage in the bore hole wall.
, , , -14-
Claims (11)
1. An expansion anchor for mine roofs and the like comprising an expansible shell formed from an integral uni-tary blank of sheet metal having a pair of initially substan-tially rectangular leaves interconnected to each other at proximal ends thereof by a bail strap and free at the other ends thereof, said bail strap being bent to a U-shape and said leaves being bent to semi-cylindrical shape concentric with a bolt axis with their side edges in mutual abutment defining a generally cylindrical exterior for engagement with the walls of a mine ceiling bore, said bail strap having an enlarged circular top portion midway along its length and straight narrow leg portions extending in parallelism there-from to said proximal ends of the leaves, an expander cone nut having an internally threaded bore and located in confined relation between said leaves and between said leg portions and having a generally frusto conical outer surface con-vergently tapering to a smaller diameter end interposed between said leaves to abut the leaves and spread them outwardly, a bolt threaded through the cone nut for moving the nut downwardly in the shell and bring progressively larger diameter portions of said outer surface against the leaves for spreading the leaves outwardly, said circular top portion of the bail having a pop-out center formed by a pair of substantially semi-circular arcuate cuts therethrough defining a concentric circle inter-rupted by a pair of frangible uncut attachment sections, said pop-out center being of slightly larger diameter than the bolt and aligned with and adjacent the free end of the bolt to be abutted by the same and popped out upon predetermined rotation of the bolt and form an aperture for passage of the bolt through said top portion, and said circular top portion of said bail strap including both said pop-out center and the remaining encircling portion being shaped in an upwardly convex cylindrical path having its axis of revolution passing through the bolt and located along said bolt axis at a position lying between said circular top portion and said proximal ends of said leaves and with the uncut attachment sections arranged along a diametric axis paralleling the axis of revolution of said cylindrical path to facilitate centering of the bolt relative to the circular top portion upon engagement thereof.
2. An expansion anchor as defined in Claim 1, wherein said cone nut has a diameter larger than the distance between the leg portion of said U-shaped bail strap at the larger end of the cone nut nearer said circular top portion and the tapered conical sides of the cone nut having rectilinear channel grooves in diametrically opposite portions thereof spanning the axial length of the cone nut parallel to its axis receiving said leg portions in slidable nesting relation therein to prevent rota-tion of the cone nut relative to the shell during rotation of the bolt.
3. An expansion anchor as defined in Claim 1, wherein the inner confronting surfaces of said leaves along a path laterally spanning and adjacent the proximal end portions thereof are swaged to provide an inclined ramp surface defining a conical camming seat confronting and concentrically encircling the cone nut to insure proper alignment of the cone nut and shell.
4. An expansion anchor as defined in Claim 2, wherein the inner confronting surfaces of said leaves along a path later-ally spanning and adjacent the proximal end portions thereof are swaged to provide an inclined ramp surface defining a conical camming seat confronting and concentrically encircling the cone nut to insure proper alignment of the cone nut and shell.
5. An expansion anchor as defined in Claim 1, wherein the shell leaves are coined outwardly along multiple circular paths along transverse planes of the cylinder formed by the leaves intermediate the upper and lower extremities thereof to provide outwardly pointing encircling striations on the shell exterior to press into the bore hole wall and increase the anchoring effect, the striations being of outwardly pointing triangular cross-sectional configuration.
6. An expansion anchor as defined in Claim 2, wherein the shell leaves are coined outwardly along multiple circular paths along transverse planes of the cylinder formed by the leaves intermediate the upper and lower extremities thereof to provide outwardly pointing encircling striations on the shell exterior to press into the bore hole wall and increase the anchoring effect, the striations being of outwardly pointing triangular cross-sectional configuration.
7. An expansion anchor as defined in Claim 3, wherein the shell leaves are coined outwardly along multiple circular paths along transverse planes of the cylinder formed by the leaves intermediate the upper and lower extremities thereof to provide outwardly pointing encircling striations on the shell exterior to press into the bore hole wall and increase the anchoring effect, the striations being of outwardly pointing triangular cross-sectional configuration.
8. An expansion anchor as defined in Claim 4, wherein the shell leaves are coined outwardly along multiple circular paths along transverse planes of the cylinder formed by the leaves intermediate the upper and lower extremities thereof to provide outwardly pointing encircling striations on the shell exterior to press into the bore hole wall and increase the anchoring effect, the striations being of outwardly pointing triangular cross-sectional configuration.
9. An expansion anchor as defined in Claim 1, wherein the shell leaves are coined outwardly along multiple circular paths along transverse planes of the cylinder formed by the leaves in-termediate the upper and lower extremities thereof to provide outwardly pointing encircling striations on the shell exterior to press into the bore hole wall and increase the anchoring effect, the striations being of outwardly pointing triangular cross-sectional configuration and the lowermost striation nearest the free end of the leaves having a wider base dimension providing a less sharp striation than the remaining striations to increase force requirements for pressing the lowermost striation into the force hole wall.
10. An expansion anchor as defined in Claim 2, wherein the shell leaves are coined outwardly along multiple circular paths along transverse planes of the cylinder formed by the leaves intermediate the upper and lower extremities thereof to provide outwardly pointing encircling striations on the shell exterior to press into the bore hole wall and increase the anchoring effect, the striations being of outwardly pointing triangular cross-sectional configuration and the lowermost striation nearest the free end of the leaves having a wider base dimension providing a less sharp striation than the re-maining striations to increase force requirements for pressing the lowermost striation into the bore hole wall.
11. An expansion anchor as defined in Claim 3, wherein the shell leaves are coined outwardly along multiple circular paths along transverse planes of the cylinder formed by the leaves intermediate the upper and lower extremities thereof to provide outwardly pointing encircling striations on the shell exterior to press into the bore hole wall and increase the anchoring effect, the striations being of outwardly pointing triangular cross-sectional configuration and the lowermost striation nearest the free end of the leaves having a wider base dimension providing a less sharp striation than the re-maining striations to increase force requirements for pressing the lowermost striation into the bore hole wall.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA304,441A CA1110091A (en) | 1978-05-30 | 1978-05-30 | Mine roof or rock bolt expansion anchor of the bail type |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA304,441A CA1110091A (en) | 1978-05-30 | 1978-05-30 | Mine roof or rock bolt expansion anchor of the bail type |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1110091A true CA1110091A (en) | 1981-10-06 |
Family
ID=4111583
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA304,441A Expired CA1110091A (en) | 1978-05-30 | 1978-05-30 | Mine roof or rock bolt expansion anchor of the bail type |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1110091A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4753559A (en) * | 1984-10-19 | 1988-06-28 | Seneca (St. Catherines) Manufacturing Ltd. | Expansion shell |
| CN114607428A (en) * | 2022-03-08 | 2022-06-10 | 长江水利委员会长江科学院 | An inner anchor type retractable bolt for soft rock reinforcement and application method |
-
1978
- 1978-05-30 CA CA304,441A patent/CA1110091A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4753559A (en) * | 1984-10-19 | 1988-06-28 | Seneca (St. Catherines) Manufacturing Ltd. | Expansion shell |
| CN114607428A (en) * | 2022-03-08 | 2022-06-10 | 长江水利委员会长江科学院 | An inner anchor type retractable bolt for soft rock reinforcement and application method |
| CN114607428B (en) * | 2022-03-08 | 2024-06-11 | 长江水利委员会长江科学院 | Internal anchor type telescopic anchor rod for soft rock reinforcement and application method |
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