US2504311A - Apparatus for inserting bolts into concrete - Google Patents

Description

` April 18, 1950 s, M, DUNN 2,504,311

APPARATUS FOR INSERTING BOLTS INTO CONCRETE Original Filed May 10, 1941 3 Sheets-Sheet 1 INVENTR: J ram-IENy M. DUN/u ATroRNEy; j

April 18, 1950 s. M. DUNN 2,504,311

APISARATUS FOR INSERTING BOLTS INTO CONCRETE Original Filed ay 10, 1941 I 3 Sheets-Sheet 2 JNVENTOR; .STEPHEN M. DUNN ATT URNL' Y.

April 18, 1950 s. M. DUNN APPARATUS FOR INSERTIHG BOLTS INTO CONCRETE original Filed may 1o. 1941 3 Sheets-Sheet 55 ATTOREY.

mOn. T m m PHEN M. DUNN Patented Apr. 18, 1950 UNITED .s'rA'rss PATENT ortica l 2,504,241 l i l I APPARATUS FO BOLTS M0 stephen M. mma, Le Angerer, oeuf. original alleman my 1o, 1941, serial No.

ivided and this application Febru- A ary 4, 1946, Serial No'. 645,400

' 1o claim. (c1. 1 4'0 My invention relates primarily to the art oi embedding bolts, studs, or the like in concrete or similar substances, and more particularly to a method and apparatus for accomplishing this purpose.

My invention is of particular utility in construction work, and accordingly, will be described in connection therewith, although it is to be recognized that my apparatus, method, and article may' be used in other arts without departing from the spirit of my invention. This is a division of my co-pending application, Serial No. 392,896, iiled May 10, 1941. and issued as U. S. Letters Patent No. 2,400,878, on May 28,- 1946.

In the concrete construction art, it is commonly desirable or necessary to set bolts or studs formed' of steel or other material so that one end thereof is embedded in a. mass of solid concrete. Such embedded bolts or studs are frequently used to provide means whereby other structures may be joined or iastenedto such a concrete mass. For example, in the fabrication of concrete building structures it is frequently necessary to provide extensive metal piping systems. such-as plumbing, which must be fastened in somemanner to the concrete walls of the structure. The standard practice is to partially embed a series of bolts or studsl in the concrete walls so as to leavejjan end thereof projecting, to which the piping may be tied by conventional methods. Heretofore, the embedding of the bolts or studs has A`been accomplished by either of two methods:

(a) bolts or studs are set in the forms in which the walls are' originally cast so as to actually cast the. studs into the walls; or (b) the walls are first formed complete-and then are drilled by conventional methods, as by a pneumatic drill, to holes to receive the studs which are secure'rlin the holes by anchoring devices or by cementing, or both. These are the only two methods of accomplishing this result known in the art at the present time, and both methods have many marked disadvantages. For example, it is extremely expensive to cast studs directly in the concrete as it is poured as special provision therefor must be made in the concrete forms, and. particularly in the casing of vertical walls, it is very dliiicult to secure a good bond between the concrete and the studs as voids tend to form below the studs as the concrete is poured. Also, by this standard method errors in location or changes in plans after completion of the pouring of the concrete frequently necessitate the insertion of additional studs, which must then be put in by the second conventional method, which causes delay in construction. The second method, similarly, is expensive as special holes must be drilled in the concrete, and the studs must then be anchored and cemented inthe holes, which arelabor-consuming operations requiring additional material such fas special anchors and cement, which also increase the cost. By either prior art method', however, only a relatively weak bond can be formed between the studs and the concrete, which allows the studs to pull out of the concrete if large pulling strains are impressed thereon. Thus, such prior art methods are not only expensive. to perform but actually produce only a' relatively weak bond between-the studs and the concrete;

For the purpose of simplicityin this specification and claims, I shall describe my invention as being used inl connection with a mass of aggregated material," which I hereby define as meaning aggregated or fired earthen materials having a-low modulus of elasticity and being substantially non-ductile, such as, for example, ooncrete, cement, brick, clayrand thelike, to all of which my invention is applicable.

A primary object'of rnyinvention is to provide a method and apparatus for embedding a stud in a mass of aggregated material which is more economical to use than the prior art methods described above and which formsa much stronger bond between the stud .and the aggregated material than such prior art methods. I intend to accomplish this by sheeting avstud directly into a mass oi aggregated material so as to rigidly x the stud therein. I have foundthat such a method is very economicaland attains a result f much superior to the standard methods described above. For example, a -large number of pulling tests have been run on sand-blasted studs which were carefully tamped and cemented in drilled holes in concrete blocks, in accordance with conventional prior art methods. It was found that all of such studs could be pulled from the concrete by applying a pulling force thereto of 900 pounds per square inch, or less, of Icircumferential area of the embedded portion of the stud. Similar pulling tests conductedby me on studs embedded in concrete by my method, as described hereinafter, have established that the pulling force required to pull such a stud is commonly over 3800 pounds per square inch oi` circumferential area of the embedded portion of the stud.

In `fact, by extensive tests on pulling studs hav ing a diameter of one-quarterA inch and which had been embedded in concrete by my process, I have discovered that a bond may-be formed between the stud and the concrete of such strength that the stud will break before the bond between the stud and the concrete will break; i. e., the bond between the stud and the concrete is greater thanthe breaking strength of the stud.

My process and apparatus include the use of a gun of special design for firing a stud into aggregated materials. I have found that it is important in the practice of my process to hold the -surface of the aggregated material in place while the bolt is shot thereinto, and I prefer to accomplish this by holding the muzzle of my gun solidly against the aggregated material when the gun is fired 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 the exhaust of gases from the gun barrel, to assist in preventing recoil of the gun barrel away from the surface of the aggregated material, and it is another object of my invention to provide a gun capable of accomplishing this result.

It is also important to provide such a gun in which the recoil of the gun resulting from ring the same is put on the breechblock thereof which is allowed to recoil independently of the gun barrel, thus further reducing the possibility of recoil of the muzzle of the gun from the surface of the concrete. and this is another object of the invention.

A further object of my invention is to provide such a gun having a locking mechanism which is so designed that the gun cannot be red unless the muzzle of the gun is in pressure engagement with a surface. This feature of my gun insures that the desirable supporting pressure is applied to the concrete while the gun is being fired.

Althoughin carrying out the method of my invention it is important to provide a supporting pressure on the surface of the concrete surrounding the area to be penetrated by the stud during Figure 10 is a longitudinal sectional view of an alternative form of gun muzzle for my invention.

Figure 11 is a sectional view illustrating the position of the parts at the time when the firing pin is fully retracted.

Referring to the drawings, I show a gun I5 including a breechblock member l5 to which is rigidly secured, as by an upper bolt I1 and a lower bolt i8, a handle frame member I9 having a handle 20 at its' outer end. The breechblock member i6 is formed to provide a central chamber 22 and an outer chamber 23. and having an opening 24 in one side thereof, as best shown in Figure 6. The central chamber 22 is provided with a first wall 25 at one end thereof anda second wall 26 at the' other end thereof, the latter being provided with a cylindrical boss 28 projecting into the central chamber.

A gun barrel 29 is provided with a head member 30 which is rotatably supported on the lower bolt i8 which passes through an opening 3| formed in the head member. The opening 3|. is provided with a counterbore 32 in which is retained a relatively stlff compression spring 33 which engages the inner end of the counterbore and also the second wall26 of the -breechblock member l5 so as to normally hold the head member 30 forwardly with considerable pressure against the first wall 25 and away from the second wall 26, in the position shown in Figure 1. The gun barrel 29 is provided with a bore 35, the inner end of which is provided with a cartridge chamber 36, the inner penetration thereof, it is sometimes difficult for an operator to hold a gun barrel against the surface and perpendicular to the surface so as to supply the necessary supporting pressure from the muzzle of the gun. It is therefore another object of my invention to provide means for applying such supporting pressure to such a surface by the gun barrel without requiring the gun barrel to be perpendicular to the surface.

` Other objects and advantages will appear from the following description and from the drawings, which are for the purpose of illustration only and in which: i Figure 1 is a longitudinal sectional view of my gun loaded with my novel projectile.

Figure 2 is a view similar to Figure 1 but illustrating the position of the parts during ring oi' the gun.

Figure 3 is an enlarged cross-sectional view taken on the line 3-3 of Figure l.

Figure 4 is an enlarged cross-sectional view taken on the line 4-4 of Figure 1.

Figure 5 is a longitudinal fragmentary sectional view, considerably enlarged. taken on the line `5-5 of Figure 1.

. Figure 6 is a cross-sectional view taken on the line 6-6 of Figure 2.

Figure '1 is a diagrammatic view illustrating the gun muzzle in position for ilring. Figure 8 is a diagrammatic view illustrating the projectile and the gun muzzle at the conclusion of firing.

Figure 9 is a diagrammatic view showing the bolt at the conclusion of the operation.

end thereof being chambered at 3l so as to receive the cylindrical boss 28, as best shown in Figure 2. The outer end of the gun barrel 23 forms a muzzle 38, and the gun barrel is provided with radial ports 39 which communicate between the bore 35 and the outer chamber 23 of the breechblock member I6, the outer chamber in turn communicating through the opening 24 in the side thereof with the atmosphere so as to permit exhaust gases to discharge therethrough from the bore.

The handle frame member I9 is provided with -a vertical wall 4| having a central opening 42 therein in which is held the outer end of a guide sleeve 43 having an inner end 44 of reduced diameter which makes a close iit with the walls of an axial bore 45 formed through the second wall 26 of the breechblock member I6. The inner end 44 of the guide sleeve 43 is provided with a ring pin bore 45 through which extends a firing pin 4l. I'he ring pin 41 is supported in an actuating cup element 48 so as to permit restricted relative axial movement therebetween, the ring pin being provided with a ring point 43 and an inner head 50 which limits rightward movement of the ring pin relative to the actuating cup element, and an outer head 5i engaged b'y a ring pin return spring 52 which is adapted to normally hold the firing pin relative to the actuating cup element 48 in the position shown in Figure l. The actuating cup element 48 is adapted for sliding movement in the guide sleeve 43, being guided therein by a lug 56 (Fig. 4) formed on the top of the actuating cup element and confined in a longitudinal slot 53 formed in the top of the guide sleeve 43. A compression spring 54 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 54 exerting a substantial leftward force on the actuating cup element 48 so as to yieldabl;

retain it in the position shown in Figure 1. The inner end of the guide sleeve 43 is cut away to provide a transverse slot 61.

As best shown in Figures 3 and 4, against the outer face of the second wall 28 of the breechblock member I8 is provided a vertically movable plate member 58 which is guided for vertical movement by guide screws 58 which are threaded into the second Wall 28 of the breechblock member. The plate member 58 has a cut-away central portion 60 providing a horizontal face 8| having a sernicircular opening 82 therein. The radius of the semicircular opening 82 is less than the radius of the inner head 50 formed on the firing pin 41, and, as best shown in Figure 1, when the vplate member 58 is in its lowermost position, the semicircular opening 82 partially encircles the firing pin 41 and the inner head 50 engages the plate member to prevent the firing pin from moving to the left from the position shown in Figure 1. Consequently, the vertically movable plate mem'- ber 58 comprises a means for preventing actuation of the firing pin 41, and, as will be understood by those skilled in the art, the plate member mustbe raised before the firing pin can be moved to the left into firing relation. The plate member 58 is normally retained in its lowermost position, as shown in Figure 3, by a leaf spring 64 which engages the top of the plate member and which is suitably secured to the breechblock member I6 as by screws 65.

Locking means is provided to positively lock the plate member 58 in its lower position, as shown in Figures 1, 3, and 5, 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 69 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 fixed to the handle frame member |9 as by screws 14, the compression spring 12 being centered by the outer end 15 of the stud 68 and by a boss 16 formed on the bracket element 13.

As best shown in Figure 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 fixed a trig- A is cylindrical and is externally threaded so as to accommodate a nut ||0 after the stud has been embedded in a surface, as best shown in Figure 9.

In operation, the gun |5 is first loaded with the cartridge |00, the operating parts of the gun being initially in the position shown in Figure 1. To accomplish this loading operation, the gun barrel 29 is first rotated on the lower bolt I8 in a counterclockwise direction, as seen in Figure 6, to the position -shown by dotted lines ||3 shown therein, rotation of the gun barrel being stopped by engagement thereof with a shoulder |4 formed by one wall of the opening 24 in the breechblock member I6. When the gun barrel 30 is in the position shown by the dotted lines ||3 of Fig. 6, it will be noted that the bore, indicated by dotted lines I5 thereof, is aligned with an arcuate opening-fl I6 formed in the breechblock member |6A through which the cartridge |00 may be inserted into the cartridge chamber 38 formed in the gun barrel. The gun barrel is then rotated in aclockwise direction back to the full line position shown in Fig. 6, in which the gun is ready for firing.

Prior to ring of the gun, the muzzle 38 of the gun barrel 29 is firmly pressed against the surface ||1 of the mass of aggregated material ||8 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 |9 and the breechblock member I8 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 26 to move into the chambered portion 31 of the cartridge chamber 36 to the position thereof shown in Fig. 2. During such leftward movement of the ger 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 Figure 4, the rectangular slot 80 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 free end of a leaf spring 88 suitably fixed to the trigger bar 18, so as to tend to rotate the releasing dog in a clockwise direction as seen in Figure 1. Also secured inthe trigger bar 18 is a cross pin 89 which engages beneath a spring plate 90, .the inner end 9| of which is inserted into a suitable slot 92 formed in the plate member 58, as best i breechlock member I6, as soon as the head member 30 of the gun barrel 29 engages the inner end 68 of the stud 66, the stud 66 is moved tothe right to the position shown in Fig. 2, in which the head member 89 thereof is out of engagement with the angled top surface 10 of the vertically movable plateunember 58, permitting the top of the plate member to clear the head member 69. Since the semicircular opening 62 in the plate member 58 normally encircles the firing pin 41 between the inner head 50 formed on the firing pin and the inner wall 26, it will be apparent that the firing pin cannot be moved to the left from the position shown in Fig. l into engagement with the primer |02 of the cartridge |00 until the vertically movable plate member58 has been raised to the position shown in Fig. 2. Consequently, it will be understood thatthe stud 66, which is normally held in the position shown in Fig. 1 by the compression spring 12, operates as a locking means to prevent firing of the gun i until such time as the muzzle 38 of the gun barrel 29 is in strong pressure engagement with the surface ||1. This is an important featureof 'the invention.

With ihestud se in its unlocking position, as.

||8 of Fig. i to the position in which it is shown in Fig. 2. As the trigger handle 18 and the trig' ger bar 18 move rearwardly from the position shown in Fig. 1, the cross pin 88 secured in the trigger bar moves along beneath the spring plate 80 until it engages the cam face 85 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 8| of the spring plate 90 is secured in the vertically movable plate member 58, lifting of the spring plate 90 causes a similar lifting of the plate member 58 against the action of the leaf spring 04 to move the plate member upwardly to the position shown in Fig. 2, in which the horizontal face 3| and the semicircular opening 82 of the plate member are raised above the inner head 50 of the firing pin 41. As will also be appreciated, rightward movement of the trigger bar 18 causes a similar rightward movement of the actuating cup element 48, due to engagement of the lower leg 85 of the releasing dog 03 with the lug 50 formed on the actuating cup element, thus compressing the compression spring 54 and storing energy therein. Upon continued movement of the trigger bar 18 to the right, the upper leg 84 of the releasing dog 83 engages the engagement shoulder 8| (Fig. 2) formed on the bracket eiement 13, so as to cause the releasing dog to rotate in a counterclockwise direction so as to rotate the lower leg 85 thereof out of engagement with the lug 58 formed on the actuating cup element 48. The stored energy of the compression spring 54 is released thereby, which drives the actuating cup element 48 and the firing pin 41 to the left at high speed. the actuating cup element 48 stopping its leftward movement upon engagement with the guide sleeve 43, in the position shown in Fig. 2, but the firing pin 41, due to its inertia, continues its leftward movement and the point 49 thereof pierces the primer |02 of the cartridge case IOI to fire the cartridge in a manner well known in the art. Fig. 2 shows the firing pin 41 having just pierced the primerv |02 to nre the cartridge |00, and shows the projectile |03 just starting its travel through the bore 35 of the gun barrel 29.

Under the impact of the explosion of the powder 39 the projectile |03 travels outwardly through th bore 35 ofthe gun barrel 29- and enters the m of material to approximately the position shown in Fig. 8.- It is to be noted that until `after the projectile |03 has penetrated the mass of aggregated material |I8 to its desired depth. the muzzle 38 of the gun barrel '29 is held in pressure engagement with the surface |I1 of the aggregated material, thus providing substantial support for the surface of the aggregate material around the area of penetration of the projectile |03. This is an important feature of nLv invention. From extensive tests, I have discovmuzzle 38 of the gun barrel 28 in pressure engagement with the surface I I1 of the mass of material ||8 during the tiring of the gun I5, several additional features are incorporated in the 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 the powder 99ggmay then pass raered that unless the muzzle 38 of the gun barrel 28, or some other equivalent support, is provided for the surface ||1 of the mass of material III around the area of penetration of the projectile |03, the mass of material around such area invariably cracks and shatters. and usually forms a small crater around the embedded stud, which is very undesirable as it mars the surface I I1 and weakens the bond between the projectile and the f Fig. 9.

dially outwardly therethrough to exhaust to the atmosphere, reducing the natural recoil of the gun barrel 29 which would occur if these ports were omitted'. So long as the muzzle 38 of the gun barrel 29 is held in pressure engagement with the surface ||1 of the aggregated material I|8 during firing of the gun I5, as described, the projectile |03 will cleanly enter into the mass of aggregated material without cracking, shattering, or otherwise marring the surface I I1 thereof.

After the projectile I 03 has been red into the mass of aggregated material IIS, as shown in Fig. 8, the cylindrical piston |05 may be readily removed therefrom, as by cutting or otherwise, and a standard nut ||0 may be threaded onto the projecting end of the stud |04, as shown in Thus, the projecting portion |09 of the stud |04 may be used as a tie member for fastening any desired object to the mass of aggregated material I I8.

In Fig. 10 I show an alternative embodiment of the invention, which provides means for insuring a solid supporting pressure against the surface ofthe supporting material around the area to be penetrated by the stud. In this form of the device, a gun barrel |20 is provided for a gun (not shown) which is in all respects similar to the gun I5 except for the muzzle construction 'to be described. The outer end of the gun barrel |20 is machined to provide a spherically convex muzzle |2| adapted to fit against a spherically concave surface |22 formed in a foot member |23 having a at 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 larger diameter than the bore |28 of the gun barrel |20, and is provided with radial exhaust ports |28 which communicate between the axial bore |21 and the atmosphere to permit the exhaust of air ahead ofthe 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 tapped opening I8| in the gun barrel |20 and the other end of which is bent into a suitable tapped opening |32 in the foot member, one end portion of the spring being retained in a helical groove |33 cut in the periphery of the gun barrel and the other end portion of the spring being retained in a helical groove |34 cut in the periphery of the foot mem-I ber. It will thus be apparent that the gun barrel |20 may deviate several degrees in any direcytion 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 feature of the invention obviates the necessity of holding the gun e barrel |20 exactly perpendicular to the surface support for the surface ||1 directly surrounding the area of penetration of the projectile |03.

|25, as must be done with the gun barrel 28. while retaining an even supporting pressure around the area to be penetrated by the stud. The radial exhaust ports |28 also permit the release of air ahead of the projectile when it is fired, which further reduces the tendency of the gun barrel to recoil from the surface |25 during To additionally assist in maintaining the u firing ofthegun.

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 specific embodiment shown and described, but desire to be afforded the full scope of the following claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A gun for shooting attachment projectiles into substances so as to have them embedded therein comprising means providing a gun barrel, a chamber to receive a cartridge and said projectile, means for firing the cartridge, and a foot member attached to and having the axis thereof shiftable relative to the axis of the gun barrel so as to be capable of being positioned squarely against the surface of the substance to be penetrated independently of the degree of deviation of the body of the gun barrel from a position normal to said surface.

2. A gun for shooting attachment devices into substances so as to have them embedded therein comprising means providing a gun barrel, a chamber to receive said attachment device and means for propelling said attachment device through the gun barrel, and a foot member attached to and having the axis thereof tiltable relative to the axis of the barrel whereby said foot member is capable of being adjusted flatly against the surface of the substance to be penetrated independently of the degree of deviation of the body of the gun barrel from a position normal to said surface.

3. A gun for shooting attachment devices into substances so as to have them partially embedded therein comprising means providing a. gun barrel. a chamber to receive said attachment device and means for propelling said attachment device through the gun barrel, and an adjustable foot member having a flat outer face, said foot member and the gun barrel having a ball and socket joint therebetween whereby the foot member is capable of being adjusted flatly against the surface of the substance to be penetrated independently of the degree of deviation of the body of the gun barrel from a position normal to said containing the projectile, means for firing the` cartridge, and an adjustable foot member having a ball and socket joint with the gun barrel and a resilient element attached to the foot member and the gun barrel whereby said foot member is capable of adjusting itself relatively to the body of the gun barrel so as to be capable of being positioned flatly against the surface of the substance to be penetrated independently of the position of the body of the gun barrel and to return therefrom at completion of the discharge.

5. A gun for shooting projectiles into substances so as to have them partially embedded therein comprising means providing a gun barrel adapted to receive a cartridge, the muzzle end of said barrel being equipped with a foot plate movably attached to the barrel, means for attaching the foot plate to the gun barrel so as to resist movement of the foot platelongitudinally of the gun barrel but permit lateral movement of the foot plate with respect thereto, said foot plate having a bore larger in vdiameter than`the bore of the barrel whereby the axis of the bore of the gun barrel may deviate considerably from a line normal to theV engaging surface of the foot plate and the foot plate and the gun will function as a unitary structure in providing an inert mass either held or pressed against the surface of the substance. f

6. A gun for shooting attachment projectiles into substances so as to have them partially embedded therein comprising means providing a jointed gun barrel adapted to receive a cartridge containing the projectile, means for firing the cartridge, said jointed barrel comprising a fixed portion and a foot plate adjustably secured to the fixed portion and capable of adjusting itself relatively to the xed portion and to a position squarely against the surface of the substance to be penetrated independently of the position of the body of the gun barrel, there being outlets for air in the jointed gun barrel ahead of the projectile.

7. A gun for shooting attachment projectiles into substances so as to have them partially embedded therein comprising means providing a gun barrel adapted to receive a. cartridge containing the projectile, means for ring the cartridge, foot plate adjustably secured to the barrel` breechblock mounted around the barrel adapted for movement endwise with respect thereto and spring means adapted to extend the barrel relative to the breechblock, means for igniting the explosive charge, means on the breechblock adapted to prevent the ignition of said charge until a positive pressure is applied to the end of the barrel against the spring means, comprising an arresting device normally holding said igniting means in inoperative position, and a release responsive to movement of the barrel relative to the breechblock for releasing said arresting device.

9. A gun comprising a barrel having a bore therein open endwise to the atmosphere, a chamber to receive a projectile and an explosive charge, means for igniting said explosive charge, a breechblock mounted for spring-loaded longitudinal movement relative to the barrel, arresting means on the breechblock for the firing pin, a pressure release therefor cooperable with the barrel adapted to prevent the ignition of said charge until a positive pressure is applied to the end of said barrel adapted to move said barrel relative to the breechblock, and a series of interconnected passage means through the barrel communicating between the chamber and the atmosphere adapted to permit the escape of air in thebarrel directly into the atmosphere ahead of said projectile.

l0. A gun comprising a stock, a barrel having a longitudinally movable attachment to the stock, a chamber in the barrel adapted to receive a projectile and an explosive charge, a firing pin mechanism in the stock for igniting said explosive 1l a charge, means to prevent the ilnition of said charge until a positive longitudinal pressure is applied to the end of said barrel comprising pressure means adapted to normally extend the barrel relative to the stock. an arresting device on the stock normally engaging the mechanism in safety position, and a release for said arresting device responsive to movement of the barrel against the pressure means and actuable by longitudinal movement oi' the barrel relative to the stock.

M. DUNN.

, iz nmnnnczs Crum UNrrnD STATES rATENTS Number Name Dete Miller Aug. 23, 1921 Smith Sept. 4, 1923 Pipes June 23, 1936 Temple Apr. 6, 1943

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