US2400878A

US2400878A - Method of inserting bolts into concrete

Info

Publication number: US2400878A
Application number: US392896A
Authority: US
Inventors: Stephen M Dunn
Original assignee: Individual
Current assignee: Individual
Priority date: 1941-05-10
Filing date: 1941-05-10
Publication date: 1946-05-28
Anticipated expiration: 1963-05-28

Description

3 Sheets-Sheet l ay 2, E945., s. M. DUNN METHOD OF INSERTING` BOLTS INTO CNCRETE Filed May l0, 1941 nu um,

Maly 2, QQSO S, M DUNN ZQV METHOD 0F INSERIING BOLTS INTO CONCRETE Filed May l0, 1941 5 SheeS-Sheel'l 2 G mlmum lmlllllll METHOD OF INSERTING BOLTS INTO CONCRETE Filed May l0, 1941. 3 SheebS-Shee't 5 Figi@ Fo AZ- ite-else f time STATES l PTE y 22a-)0378; Lvl( 'n l' I METHOD FisERrnvGnoL-Tsm'ro.

. .coNcnE'ra-g- ,1f i stephen 511mm, Loe'ngeies-, oeuf.' Appueetiengtayic, 1941;; serial Ne, 39as9sf- L y ,I 4-o1eims.'f wirres) My inventiqn relates primaria; to the art of' V which are laborconsumingoperations requiring embedding bolts, studs; o r thelike in concrete 'or -additional materials'such as special anchors and similar-substanceaand more -.particularly .ifo a cement; which also increase/the cost. vlily either method .for accomplishing this purpose x prior artmethod, however', only Va relatively'weak 4in connection therewith, although ite is to be the 'concrete if large pulling strains are impressed -recognized that my mthodvmay be usedin other thereon. Thus, 'such' prior artmethods are not .arts without departing" from 'the spirit of myonly expensive -to perform but actually produce thereof is'e'mbedded in a mass of'solid concrete.

invention. In the concrete construction art, itl is comand the concrete..`

monly desirable or necessary to set bolts or studs For the'pu'rposelof simplicity in this specifica- MLV invention is of particular 4utility,` in con- 5'; b ond'can be formed between' the studs andthe -structionwork and, accordingly, Will be described'- concrete, which allowsthe studs to pull out of" loon-1y' aA relatively \w eak bond between Athe studsformed of steel or other material solthat one end tion and claims, I shall describe my invention as` A A being used in connection witha massv of ag- Such embedded boltsor studs are f requentlyused vgregated material, which I "hereby ydefine vas to provide meanswhereby other structures may meaning aggregated or fired earthen materials be "joined or fastened tosucha concrete mass. -having a low modulus of lelasticity and beingsub-I i For example, in the fabrication of concrete .provide extensive metalpiping systems, such as of which my invention is applicable.

plumbing, -which'must be fastened in somemanxA primary object of my invention is to provide -ner to the concrete walls ofjthestiucture. The .a methodfor embedding a stud in a mass of standard practice is to partially embed fa series aggregated materialwhichare moreteconomcal methods of accomplishingthis result known in i I the art at the present time, and both methods of4 bolts or studs in the concrete -walls so as to to use than the prior art methods described above stantially non-ductile, such ashfor examp1e,=con building structures it isfrequent1y necessary to crete, cement,'lbrick,,clay, andthe like, to all leave an end 'thereof projecting, to which .the 25 and which forme greatly stronger bond between l pipingmay be tied by conventional methods.` the stud. and the aggregated material than such Heretofore, the embedding o f thelmlts-or' studs prior art methods.' I intend to accomplish this has been accomplished by either of two methods: by shooting a stud directly into 'a mass. of aggre- (a) bolts or studs are set in the forms in which, the wallsare originally cast so as to actually cast in. -I have found that such a method is very gated material sofas to rigidly fix the stud tliere-y thevstuds `IlliO the Walls; .01 (b) lthe Walls alle economical-.and attains a result much superior first formed complete and then are-drilled by -to the standard methods described above. For 'conventional methods, as by apneumatic drill, exam-pkg, a large number o fpull'ing tests have to ferm holes-to receive the studs which eresebeen run on sand-blasted studs weten were ease .cured inthe holes ivy-anchoring devices er leyA fully tempered and cemented in drilled. melee in cementmg, or both. These are the only two prior art methods. .It was iotmd that all of h t ul 11e fro .the c ner te b have many marked disadvantages. For exam- Suc s'uds co d be pu d m O 'e y 90o d ple, itis extremely expensive to cast studs directly 40 a'pplymg a' pulling force thereto of poum s in the concrete as it is 'poured as special provision per squaremchl gr less" of circumferential area therefor must be madein theconcrete fornis, an`d, of the embedded Demon 'of 'the stud 'slmar Y ulling tests conducted .byme on studs embedded `arto rl inh castn vpelyl'dlcuslt totscure la t'lofdllgbevtl/lelntll im' concrete by my method as descnbed harem concrete and the studs asvoids tend to form be-l after have established tha-'t the pulling force re" low the studs as the concrete is poured. Also, by quired tol-Dun smh a stud is commonly over 3800- concreteblocks, in accordance I with conventional this standard method 'errors in location or pounds. per square inch of circumferential afreaf changesin Plans aftercompletion'of the pour of the embedded portionofthe'stud In fact by ing ofthe concrete frequently 'necessitate the in extensive tests mplllng Studs hal/ing a diam' sertion 'of additional-studewhieh must then be to eier 0f .GHF-luefter inch' .and which? had be?? put in by the second conventional method, which embedded in concrete bymy process, I have d1s causes delay in construction.. -The second 'methcovered that4 a bond-.maybe formed between the be drilled in the "concrete, vandthe studs jmust'k od, similarly, is' fexpensive as special holes must stud and the concreteof such strength that the then be' anchored andcfmented in 'the holes, 'c5 and thel concrete will break; i. e., the bond be..

`stud will breakbefore'the bond between the 'stud tween the stud and the concrete isv-greatertha the breaking strength of the stud. i

My process includes-the use of a gun of special design foriiring a stud into aggregated materials. f

I have found that it is important in the practice of my process to hold the surface of the aggregated material in placev while the bolt is shot thereinto, and I prefer to accomplish this by holding the muzzle of my gun solidly against the aggregated material whenthe vgun isiired and until the stud is embedded therein, and this is a feature of my invention. To accomplish this purpose, it is necessary to provide' for theexhaust of'gases from thje gun barrel, to assist inprevent-Q the same 'is-put on the breechblockthereof which is allowed to`recoi1 independently of the/gun barf rel, thus further 'reducing the' possibility'ofrecoil of` the muzzle of the gun from the surface of the` concrete, and this is -vention. i

another object of the in' A further object of my'inven'tion is-,to provide `such' a gun having a locking mechanism which is vso designed that the gun cannot be fired unless the muzzle of thegun'is in pressure engage7 ment with a surface. This feature'of my gun insures that the desirable supporting pressure is 'applied'. to

`fthe concretewhile the gun'. is; being fired. Although in carrying out the methodof my invention it -is limportant toprovidey "a, supporting lpressure on the surface of the concrete surroundingthe area tobe penetrated -by -the s tudduring' agunin Fig. 6 is a cross-sectional view taken en the line 6 6 of Fig. 2.

Fig. '7 is a diagrammatic vie/w illustratingfthe. gun muzzle in position for firing.

Fig. 8 4is a diagrammatic `view illustrating `the conclusion projectile and the gun muzzle at the of firing.

at the conclusion of the operation'.

Fig. 9 is a Idiagrammatic view showing'thebolt'f'.

Fig. 10 is alongitudinal sectional view of novel cartridge.

Fig. l1 is a longitudinal sectional view of an alternative form of gun muzzle for my invention.

.Referring to the drawings; I showa. gun-I5 including a breechblock member'lii t'o which is rigidly secured, as by an rupper-boltv Il and alower bolt I, a handle frame memberv Ishavinga handle 20 at its outer end. T he'breechblock member I6 is formed to provide a central chamf Y ber 22 -and an outerl` chamber 23,Qand having an opening 24 'in one side thereof, as best in Fig. 6. The central chamber 22 'is'floroviled` .fw with afirst wall 25 at one end thereof andaeeond wall 26 at the other end thereof. the latter 1 being provided with a cyiindricai boss 2s 'pre-` jecting intothe central chamben member I6 so as to normally hold theheadjniemf, ber 30 forwardly with considerable Apressure' penetrationthereof, it is sometimes diicult for an operator to hold agun barrel against the surface andv perpendicular ftothe surface'so as to supply the necessary supporting pressure from the` muzzle of the gun.-}It is therefore another object of my invention toprovidev means forapplyingsuch vsupporting pressure to such a surface. by-the guni barrel withoutjrequiring' they gun bar -y rel to 'be perpendicular to the surface.

i Although'l any suitable type `of stud may be used incarrying outmynovel method described above, I have discovered that a particular type of 4projectile construction. as described hereinafter, gives excellent. results, and it is a vfurther object of my inventionl to provide such a projectile. I prefer` to provide a projectile having a body portion-.whichis atleast partiallycovered by a non-metallic sleeve, which. may be formed of paper, for example, which projects -beyond l.the

. rear ofthe-.projectile toform an expansible cup.

Suche projectile maybe used otherwise than in my present method, and'I do notI intend to be limited to the specific use described forsuch'a projectile. i l Other objects and advantages will appear from the following description and from the drawings, which are for the purpose of illustration only andinwhich: f

lFig. 1 is a longitudinal sectional view of my gun loaded with my novel projectile.

Fig. 2 is a View similar to Fig. 1 but illustrating the positionof the parts during firing of the gun. -Fig. -3 is an enlarged crossfsectio'nal view taken on the line 3-3 of Fig. 1.

Fig. 4 is an'enlarged cross-sectional view taken ontheline4-4ofFlg.1. f Fig. 5 is a longitudinal fragmentary sectional A gun barrel 23 is provided With a head meinber 30 which is rotatably supported on'the'lower i bolt I8 which passes through `an opening. '1 formed in the head member. The 'openinglIf-,v is providedwith a counterbore''32'"i Whlfbh is retained a -relatively stiff compressionv spring?` 33 which engages the inner endof thecounterbore. and also the second wall 26 of the lbre'echblock against the first wall 25 and a'vvayfrruii"the`vv second wall 26, .in the position shown in Fig'.;1`.' The gun barrel Z9 is provided with'abore,

the inner end of which is provided withafcartridge chamber 36, the inner end thereof being chambered at 3l so as to receive the cylindrical. boss 28,- as best shown in Fig. 2. -1The1outerlend [of the gun1bar'rel'29 forms 'a muzzle ngandfthe 'i gun barrel is provided'with -radialports 3 9 which communicate between the bore 35 andthebuter.

chamber 23 of the breechblock memberfl; the

outer chamber in turn communicating through the opening 24 in the side thereof-with lvther atmosphere so as to permit exhaustgase'stoidlscharge therethrough from the bore.` j The handle frame member I9 is provided'w'ith a ,vertical wall 4! having a central opening`42 therein in which is held the outer endof a guidey `sleeve 43 having an inner. end 44 :fof reduced -diameter which makes a close tvwith thefwalls. of an axial bore 45 formed through the second i.;

wall 26 of the breechblock member llfl'he!y inner end M of the guide sleeve 43 is 'provided with a iring pin bore 4 6 through which extends.v a. ring pin M.

ing cup element, and an outerhead 5I engaged for sliding movement in the guide sleeve 4I, being guided therein by a lug 56 formed on the'top The firing pin 41 is supported. i in an actuating cup element 48 so as to restricted relative axial movement therebetween, f i the firing pin being provided With a flringap'oint 49 and an inner .head 50 which limitsvrightward u movement oi the firing pin relative to the actuatof the actuating cup element and conned in a longitudinal slot 53 formed in the top of the guide sleeve 43. A compression spring 64 is provided in the guide sleeve 43 and engages the outer face of the actuating cup element 48 and a screw plug 55 threaded into the outer end of the guide sleeve, the compression spring 64 exerting a substantial leftward force on the actuating cup element 48 so as to yieldably retain it in the position shown in Fig. 1. The inner end of the guide sleeve 43 is cut away to provide a transverse slot 51.

As best shown in Figs. 3 and 4, against the outer face of the second wall 26 of the breechblock member I6 is provided a vertically movable plate member 58 which is guided for vertical movement by guide screws 59 which are threaded into the second wall 26 of the breechblock member. The plate member 58 has a cutaway central portion 60 providing a horizontal face 6| having a semicircular opening 62 therein. The radius of the semicircular opening 62 is less than the radius of the inner head 50 formed on the i'lring pin 41, and, as best shown in Fig. 1, when the plate member 58 is in its lowermost position, the semicircular opening 62 partially encircles the firing pin 41 and the inner head 50 engages the plate member to prevent the ring pin from moving to the left from the position shown in Fig. 1. Consequently, the vertically movable plate member 58 comprises a means for preventing actuation of the ring pin 41, and, as will be understood by those skilled in the art, the plate member must be raised before the firing pin can be moved to the left into rlng relation. The plate member 58 is normally retained in its lowermost position, as shown in Fig. 3, by a leaf spring 64 which engages the top of the plate member and which is suitably secured to the breechblock member |6 as by screws 65.

Locking means is provided to positively lock the plate member 58 in its lower position, as

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trigger bar 18, so as to tend to rotate the releasing dog in a clockwise direction as seen in Fig. 1. Also secured in the trigger bar v18 is a cross pin 89 which engages beneath a spring plate '80, the inner end 9| of .which is press-iitted into a suitable slot -92 formed in the Plate member 58, as best shown in Fig. v2, and the outer end 93 of which is press-tted into a slot 94 formed in the vertical wall 4| of the handle frame member |9, the spring plate being bent toward the rear thereof so as to form a cam face 95 thereon. The ,Spring plate 90 is preferably formed of resilient material, such as spring steel.

Adapted to be inserted into the cartridge chamber 38 of thergun barrel 29, as shown in Fig. 1,

l is a cartridge |00, the details of which are best shown in Fig. 10. The cartridge |60 includes a cartridge case |0| having a primer |02 in the end. thereof, the cartridge case and primer being of any standard construction well known in the art. Inserted into the open end of the cartridge case |0| is a projectile |03 which includes a stud |04 and a piston means |05 thereon. The stud |04 is preferably formed of a relatively hard metal, such as steel. and is formed with a tapered outer end |06, on the sides of which longitudinal flutes shown in Figs. 1 and 3, which includes a stud 66 which is slidably mounted in an opening 61 formed in the second Wall 26 of the breechblock member and having an inner end 68 projecting into the central chamber 22 into the line of the head member 30, the stud having a head member 68 thereon adapted to engage an angled top surface 10 formed on the plate member 58. The stud 66 is normally urged toward locking position by a compression spring 12, one end of which engages the head member 69 and the other end .of which engages a bracket element 13 rigidly xed to the handle frame member |9 as by screws 14, the compression spring 12 being centered by the outer end 15 of the stud 66 and by a boss 16 formed on the bracket element 13.

As best shown in Fig. 5, a rectangular opening 11 is provided in the vertical Wall 4| and acts as a guide for a trigger bar 18 passing therethrough, to the outer end of which is xed a trigger handle 19, the trigger bar 18 also being guided by passing through a rectangular slot 80 formed in the bracket element 13, as best shown in Fig. 4, the rectangular slot 88 providing an engagement shoulder 8| at the top thereof for a purpose to be described hereinafter. The inner end of the trigger bar 18 is provided with a vertical slot 82 in which is disposed an L-shaped releasing dog 83 having an upper leg 84 and a lower leg 85 and being pivoted to the trigger bar by a suitable pivot pin 81 passing therethrough. Resiliently engaging the lower leg 85 of the releasing dog 83 is the |01 are preferably formed, the lower end terminating in a sharp point |08 which is preferably treated so as to render it extremely hard. Of course, if desired, the entire stud |04 may be hardened, in which case the point |08 does not `need to be separately hardened. The inner porinvention. It is important, however, to provide.

a pointed penetrating end, such as the point |08, of very hard material, and it is a feature of the invention to provide a stud having such a hard point with a shank formed of tough metal of lesser hardness. Also, if desired, the flutes |01 may be omitted without departing from the invention, although I have found that the provision of such iiutes materially contributes to successful operation of the method. The piston means |05 is tightly secured to the inner portion |09 of the stud |04 and is press-fitted into the open end of the cartridge case |0| to seal the same. As will be understood, the inner portion of the cartridge case |0| is llled with powder 99 which is plugged on' in conventional manner by a wadding H2. As will be noted from 1, the piston means |05 is of substantially the same diameter as the bore 85, making a close sliding t therewith, the piston guiding the projectile |03 through the bore 35 when the gun l5 is red and keeping the threaded portion |09 out of contact with the bore. Although the piston means |05 may be formed of any desirable or suitable material, such as, for example, metal, wood, or paper, I have discovered that superior results are attained if the piston is formed of paper. In forming such a piston means, I prefer to helically wind a strip of paper directly over the threaded portion |09 of the stud |04, the paper being tightly wound on the stud and the outer end thereof being glued or otherwise secured to the body of the piston so as to provide a cylindrical piston means as shown. In making the piston means |05, I prefer to use a paper which is provided with a glue or cement free end of a leaf spring 88 suitably fixed to the 75 coat on one side so that the piston may be fixed to the stud |04 and also so that the spiral layers of paper may be secured together to form a more or less homogeneous mass. Good results can also be attained by impregnating the piston |00, when it is made of paper, after winding with a. wax, resin, or other similar binding material. By impregnating the piston Ill with wax, paramne, or other material having good lubricating qualities, a lubricated piston is provided, which is desirable in that it assists in keeping clean the bore Il of the gun I5. By winding the paper piston directly over the threaded portion |00 of the stud |04, the threads make an excellent anchorage for l the piston, thus preventing the stud from being driven out of the piston upon the initial explosion of the cartridge. Due to the helical winding of the strip of paper forming the piston means III. the piston projects out over the inner end of the stud |04 to form a shallow cup IIII which is expanded outwardly by the combustion gases when the cartridge is fired to form a tight seal between the piston means Ill and the bore Il of the gun barrel 20, and this is a feature of the invention. Also, since the paper forming the piston |00 has comparatively little weight, substantially all of the energy of the powder explosion is stored in the stud |04, which is important In the practice of the invention as dcribed hereinafter. It is also to be .noted that although my projectile Il# has been particularly designed for use in carrying out my nove1 method, I do not intend to be limited to such use of such a projectile. For example, my conception of` providing adpaper or non-metallic sleeve, such as the piston means' I", on any standard type of projectile may be very desirable in view of the beneficial results derived therefrom, and this is a part of my invention.

In operation, the gun Il is first loaded with the angled top surface.' 10 of the vertically movable plate member I0, permitting the top of the plate f member to clear the head member Il. Since the cartridge I00, the operating parts of the gun bef ing initially in the position shown in Fig. 1. To accomplish this loading Operation, the gun barrel is first rotated on the lower bolt Il in a counterclockwise direction, as seen in Fig. 6, to the. position shown by dotted lines III shown therein, rotation of the gun barrel beingstopped by engagement thereof with a shoulder II4 formed by one wall of the opening 24 in the breechblock' member i0. When the gun barrel is in the position shown by the dotted lines IIS of Fig. 6,

it will be noted that the bore, indicated by dotted lines I I5 thereof, is aligned with an arcuate open.- ing IIS formed in ythe breechblock member I6 through which the cartridge |00 may be inserted into the' cartridge chamber I0 formed in the gun barrel. The gun barrel is then rotated in a clockwise direction back to the full line position shown in Fig. 6, in which the gun is ready for nring.

Prior to firing of the gun, the muzzle I0 of the gun barrel 29 is firmly pressed against the surface II1 of the mass of aggregated material IIO into which the stud |04 is to be embedded, Force is then applied by the operator through the handle 20 to move the handle frame member Il and the breechblock member I0 rigidly secured thereto to the left, as seen in Fig. 1, against the action of the compression spring 33 to cause the cylindrical boss 28 formed on the second wall 20 to move into the chambered portion I1 of the cartridge chamber 10 to the position thereof shown in Fig. 2. During such leftward movement of the breechblock member llas soon as the head member 00 of the gun barrel 20 engages the inner end 00 of the stud 00, the stud 00 is moved to the right to the position shown in Fig. 2, in which the head member Il thereof is out of engagement with the semicircular opening 02 in the plate member l0 normally encircles the firingpin. between the innerI head I0 formed on the ring pin and the inner wall 20, it vwill be apparent that the firing pin cannot be moved to the left from the position shown in Fig. 1 into engagement with the primer |02 of the cartridge |00 until the vertically movable plate member I8 has been raised to the position shown in Fig. 2. Consequently, It will be understood that the stud 00, which is normally heid in the position shown in Fig. l by the compression spring 12, operates as a locking means to prevent firing of the gun until such time. as the muzzle 08 ofthe gun 'barrel 2l is in ,strong pressure engagement with the surface II1. This is an importantv feature of the invention.

With the stud 00 in its unlocking position, as shown in Fig. 2, the trigger handle 10 is then drawn rearwardly in the direction of the arrowv IIO of Fig. l to the position in whichit is shown in Fig. 2. As the trigger handle 10 and the trigger bar 10 move rearwardly from the position shown in Fig. l, the cross pin 00 secured inthe trigger bar moves along beneath the spring plate 00 until it engages the cam face 0i thereof, at which time it exerts a cam action on the spring plate which lifts the same to the position thereof shown` in Fig. 2. Since the inner end 0I of the springplate l0 is secured in the vertically movable plate member l0, lifting of the spring plate 00 causes asimilar lifting of the plate member l0 against the action of the leaf spring 04 to move semicircular opening 02 of the plate member are raised above the inner head 0I of the firing pin 41. As will also be appreciated, rightward movement of the trigger bar 'I8 causes a similar rightward movement of the actuating cup element 40, due to engagement of the lower leg 05 of the releasing dog 03 with the lug 50 formed on the actuating cup element, thus compressing the compression spring l4 and storing energy therein. Upon continued movement of the trigger bar 10 to the right. the upper leg of the releasing dog 0I engages the engagement shoulder 0I (Figs. 2 and l2) formed on the bracket element 1I, so as to cause the releasing dog to rotate in a counterclockwise direction so as to rotate the lower leg 00 thereof out of engagement withthe lug l0 formed 'on the actuating cup element 40. The storedenergy of the compression spring 54 is releasedrthereby, which drives the actuating cup element 4I and the firing pin 41 to the left at high speed, the actuating cup element 40 stopping its leftwad'movement upon engagement with the guide sleeve 4l, in the position shown in Fig. 2, but the firing pin 41, due to its inertia, continues its leftward movement and the point 40 thereof pierces the primer |02 of the cartridge case III through the bore 35 of the gun barrel 20 and enters the mass of material I I0 to approximately the position shown in Fig. 8. It is to be noted that until after the projectile III has penetrated the mass of aggregated material III to its det #f @acodavs' sired'depth, the muzzle-.38 of 'the .'gun"barrel29\ is held inpressure engagement with the surface 1 \||1 of the aggregated'material, thus providing substantial support for the surface QitheJagge` gated material around. the area of penetration of the projectile |03. This is an important fea, ture of my invention. 'From extensive tests', I have discovered that unless the muzzle 30 fofthe gun barrel 29,- or some other equivalent support, is providedA for the surface ||1 of the'fmass of material 8 aroundthe area of, penetration of .the projectile |03, the mass of material arour'id..l

such area invariably cracks. and shatters, andJ usually forms a small craterl around theembedded stud, which is very undesirable as it mars. the surface |1 and weakens the bond between the projectile and the aggregatedmaterial 8t. Consequently, I believe it is very desirable to maintain a pressuregsupport for vthe surface ||1 directly surrounding the areaof penetration of the projectile |03.

To additionally assist in maintaininlgthe muzl" was exerted on the upper portion of the stud at .which point the-stud broke in half in the upper threaded portion. The portion of the stud embedded in the concrete had not moved relative to the` concrete, and the surface of the concrete surrounding the embedded portion of the stud 4was not cracked or shattered but \was perfectly "smooth around the stud. Better results have normally been attained by me by the use of a' stud having flutes, such as the longitudinal flutes |01, and a hardened point, such as the point |08, 'and I .prefer to `incorporatethese features. in my .'device, although; as indicated by the' above test,-

ltheyI may be omitted if desired.

j The depth of penetration `of-the projectile |03 'into the mass of aggregated material. I8 depends almost solely on the powder charge 99 ,used in the cartridge -|00,.for'projecti1esl of the same dizle 38 of the gun barrell 29 in 4pressureefigagement with the surface. I|1 of the mass .of mate;

rial ||8 during the ring of the gun l, several additional features are incorporated ,inthe gun.

For example, during firing, after the-projectile |03 has passed outwardly through the bore 35 beyond the radial ports 39, the combustion gases from thefpowder 99 may then 'pass radially outwardly therethrough to exhaust to the atmosrel 29 which would occur if these ports were omit- \ted.Y Also, since the cartridge case |0| is insolid engagement with the cylindrical boss.28 formed in the breechblock member l6,upon ring of the cartridge y|00 the reactive force of the powder 99 is applied directly on the breechblock, tending to move it rearwardly relative to the head 30 ofy material Iwithout cracking, shattering, or otherwise marringthesurface l |1 thereof. A typical test of the invention performed by me was as follows: The stud |04 had an external diameter oi" 0.25 inch at the upper portion |09 thereof, being provided with a Number 20 thread. Apow `mass of aggregated material H8, as shown in mensions. Extensive tests) on firing similar -pro'- jectiles into generally similar 'concrete have shownthat there is substantially no variation in the `depth of penetration of th'e projectiles. yBy

.',varying thel size or shape of .the projectiles, how-- ever, o r by varying the 'powder charge employed in the cartridges therefor, thedepth of penetration may-be controlled as desired.

After the projectile |03 has been red into the Fig. 8, the cylindrical vpiston |05 may. e readily removed therefrom, as by cutting or otherwise,

` phere, reducing the ynatural recoil of 'the gun bar and a standard nut |10 may be threaded onto the projecting end of the stud |04, as shown in Fig. 9.

'.Thus, the projecting portion |09 of the stud |04 may be used as atie member for fastening anyl desired object to the mass ofaggregated ma- In lligfll,` I show an alternative embodiment of the invention, which Aprovides means for insuring a solid supporting pressure' against the surface of the supporting material around the area to be penetrated by the stud. In this form of the device, algun barrel |20 'is provided for a gun (not shown) which is in all respects similar to the der charge approximately equal to the powder charge of a standard .410 bore Shotgun shell was used in the cartridge |00. .The stud used was a steel stud provided with apaper piston |05, as described hereinabove, and the stud was notprovided with the longitudinal utes |01, nor was. the point |08 specially hardened The stud was red by my gun into a solid concrete floor of standard construction, and the point |08 of the stud penetrated to a depth of 2.12 inches so that the entire tapered end |06 of the stud was embedded in the concrete floor with just the upp'er threaded portion |09 projecting therefrom. The paper piston |05 remained on the stud during 'penetration of the concrete and was removed by hand after completion of the ring operation. A pulling machine was connectedto the project' ing upper portionv |09 ofthe stud and a pulling pressure exerted on the stud thereby; the pressure being gradually increased over a considergun I5 except for the muzzle construction to be described.- The outer end of the gun barrel |20 lis machined to provide a spherically convex muzzle |2| adapted to iit against a spherically concave surface |22 formed in a foot member |23 having a flat engaging end |24 adapted to engage the surface |25 of a mass of aggregated material |26. The foot member |23 is provided with an axial bore |21. of considerably largerdiameter than the bore .|28 of the gun barrel |20, and is provided withradial exhaust ports |29 which communicate between the axial bore |21 and the atmosphere to permit the exhaust of air ahead of the projectile when it is fired. The foot member |23 is yieldably held in engagement with the muzzle |2| by a tension spring |30, one end of which is bent into a suitable tappedopening |3| in the Igun barrel |20 and the other end of which is bent into a suitable tappedy opening |32 in the foot member, one end portion of the spring being retained in a helical groove |33 cut in the periphery of theglLn barrel and the other end Y portion of the spring beingretained in a. helical groove |30 cut in the periphery of the foot mem.-

ber. It will thus be apparent that the gun barrel |20 may deviate several degrees in any direction from the perpendicular to the surface |25 without unseating any portion of the engaging end |24 from the surface |25 of the mass 'of aggregated material |26. This featureof the invention obviates the necessity of holding the gun barrel |20 j able: period oftime until a force of 2.500y pounds exactly perpendicular to the surface |25, as must be done with the gun barrel 29,' while retaining an even supporting pressure around the area to be penetrated by the stud. The radial exhaust ports |29 also permit the release of air ahead of the projectile when it is fired, which further reduces the tendency of the gun barrelto recoil from the surface |25 during tiring of the gun.

Although I have shown and described a preferred embodiment of my invention, it will be understood that certain parts and elements thereof may be replaced. by mechanical equivalents Without departing from the spirit of my invention. Consequently, I do not intend to be limited to the specic embodiment shown and described, but desire to be afforded the full scope of the following claims. y

I claim as ymy invention:

1. A method of embedding a stud in a solid mass of concrete, which consists in applying a temporary holding pressure to an area of the surface of the mass of concrete and moving the stud at high velocity so es to cause a portion of the stud to penetrate through said area and into the concrete and form a strong bond therewith. 2. The method o1' inserting attachment studs in hard fracturable substances such as concrete which comprises shooting a pointed stud into' the substance while maintaining a temporary holding pressure on the surface of the substance immediately surrounding the area penetrated by the stud to prevent the shattering of the `mass of said substanc/e immediately surrounding the area of entry of said stud.

'3. A method of embedding a stud in a solid mass of concrete, which consists in applying a temporary holding pressure to an area. of the sur` vface of the mass of concrete'l and shootingthe stud so as to cause a portion of the stud to penetrate through said area and into the concrete and form a strong bond therewith..

4. The method of inserting attachment studs in hard fracturable substances such as concrete which comprises shootinga pointed stud into the substance while maintaining a temporary holding pressure on the surface of the substance in proximity to the area penetrated by the stud to prevent the shattering of the mass of said substance immediately surrounding the area of entry of said stud. y v

STEPHEN M. DUNN.