US2747187A - Safety shield for explosively driven tool - Google Patents

Description

May 29, 1956 R. T. cATLlN ETAL SAFETY SHIELD FOR EXPLOSIVELY DRIVEN TOOL Filed Sept. '7, 1954 A2 Sheets-Sheet l l May 29, 1956 R. T. cATLxN ETAL 2,747,187

SAFETY SHIELD FOR EXPLOSIVELY DRIVEN TOOL Filed Sept. 7, 1954 2 Sheets-Sheet 2 n'tecl States Patent SAFETY SHIELD FOIIILOSIVELY DRIVEN Robert T. Catlin and Paul Hickman, Trumbull, Conn.,

assignors to Remington Arms Company, Inc., Bridgeport, Conn., a corporation of Delaware Application September 7, 1954, Serial No. 454,526

6 claims. (Cl. 1-44.s)

This application is a continuation-impart of our copending application Serial No. 300,716, filed July 24, 1952, now Patent No. 2,700,764, issued February l, 1955.

This invention relates to :a shield or guard for use on an explosively driven tool which is designed to minimize or prevent altogether the projection of loose flying particles as an incident to the normal operation of the tool. Accompanying the penetration of the work there is usually some spalling of a concrete surface, and fragments of rust, scale, or paint are frequently chipped from metallic surfaces. To these loose materials there must be added fragments of any gas sealing devices used in the bore of the tool and an occasional stud which breaks, chips, or ricochets on impact with the work surface. All of these materials are present in more or less quantity in the region adjacent the point in which the stud penetrates the work surface and, in the absence of exceptionally effective safety guards, are swept laterally at high velocities by the muzzle blast of high pressure gas from the barrel of the tool. The lateral projection of such materials places severe limitations upon the use of explosively operated tools and, in some jurisdictions, the use of such tools with the types of shields heretofore devised is forbidden by law or by industrial safety regulations.

The major object of our invention is to provide a shield which retains any loose particles within the confines of the shield.

There have been heretofore devised shields which prevent the rearward projection of such loose particles which are fairly effective in protecting the actual operator of the tool. Such a shield is shown in the application of Walker, Serial Number 225,146, filed May 8, 1951, U. S. Patent No. 2,645,772, issued July 2l, 1953, and an improvement thereon is shown in the application of Catlin, Serial Number 252,949, filed October 24, 1951, U. S. Patent No. 2,669,716, issued February 23, 1954. The tool of the first mentioned of these applications is provided with a safety device which will not be operated to permit firing unless the shield is firmly pressed against the work, which may be defined as the surface of the wall, floor, beam, or other structural member which is to be penetrated by a driven stud. ln the Catlin patent above identified, there is shown an improvement upon the shield of the Walker patent designed to require not only that the shield be pressed firmly against the surface of the work but that the barrel of the tool should also be substantially per- 2,747,187; Patented May 29, 1956 `ice jectives have been accomplished by the provision of a hollow boxlike shield slidably mounted on the end of the barrel and spring-urged to remain in contact with the work surface as the tool recoils away from the work on firing.

In this invention these objectives have been accomplished by the provision of a shield characterized by a top plate capable of recoiling with the tool and surrounded by a movable peripheral skirt which is spring-urged against the work surface and which, with the top plate and the work surface, forms a boxlike chamber enclosing the muzzle of the barrel after firing of the tool. The skirt of the new shield is so mounted upon the top plate that the tool and the top plate may recoil togetherrelative to the work surface without disengaging the edge of the peripheral skirt from the work surface. -Preferably, the shield will be capable of providing during this operation an expansion chamber of substantial volume within which the blast of escaping gases may be confined and substantially dissipated. Although the shield may be vented to permit expanding gas to escape, such vents should be of such dimensions that no particles of matter of substantial size may escape.

The exact nature of the invention as well as other objects and advantages thereof will become apparent from consideration of the following specification referring to the attached drawings in which:

Fig. l is a side elevational View, partially in longitudinal section along the line 1-1 of Fig. 4, showing a complete tool embodying the present invention.

Fig. 2 is a plan view, partially in section, on the line 2 2 of Fig. 1.

Fig. 3 is a fragmentary longitudinal sectional view, lshowing the fact that the sear remains locked when the tool is pressed against the work surface at a position inclined thereto.

Fig. 4 is a view similar to Fig. 3, showing the unlocking of the scar when the tool is pressed against the work surface in a position substantially perpendicular thereto.

The illustrative tool shown in the drawings comprises a barrel 1 provided with a chamber 2 adapted to receive a cartridge which is provided with a projectile in the form of a stud or other element to be driven into or against the work. The chamber is closed by a breech block 3 which is apertured to provide for the movement of a firing pin 4 to engage the cartridge primer. Breech block 3 is secured in a frame or housing 5 which houses the tiring mechanism and is extended into a handle or grip 6. The firing pin 4 is provided with a scar-engaging enlargement 7 and is urged forwardly by a firing spring 8;

Cooperating with the Sear-engaging part 7 is a sear 9 pivoted in the frame at 10 and provided with a head 11 adapted for displacement to release the firing pin by cam engagement with a trigger 12 which is mounted for rectilinear movement in the frame and is provided with a finger piece 13 within the grip 6. Normally, the sear is locked against firing pin releasing movement by la sear lock 14 which underlies the firing pin engaging portion 9a of the Sear 9 and is mounted for rectilinear movement in the frame, being thrust forward to its effective or searlocking position by a spring 15 (Fig. l).

The barrel 1 is held in a housing or action tube cover 16 provided with an end plate or frame 17 to which the barrel is secured, said end plate being rotatably secured to the breech block 3 by means of the pivot bolt 18 passing through both breech block and end plate. Slidably mounted on the 'barrel within the action tube cover 16 is an action tube 19 to which is secured an action bar 20 that extends rearwardly in alignment with and is adapted to displace the sear lock 14, to permit firing. Secured to the forward end of the action tube 19 and extending forwardly therefrom through action tube cover 16 is an .3 acties tube extension ..21. A Sprite .2.2 interposed between the rear end of the action tube extension and a shoulder on the barrel normally holds the action tube assembly laf- 20:21 `in the forward position illustrated in Fig. l.

The tool as thus far described `is substantially identical with .the one .Shown in the aforementioned patent to Walker, and is designed particularly for driving studs into diflcultly penetrable materials, such as cinder block, cement block, Portland cement concrete, and steel. The impact of the stud against aggregate materials of the concrete type tends to dislodge and forcefully expel small fragments ,or` chips at the surface. To prevent damage and injury by such flying particlCS, i-t is desirable Vto provide a shield which must .be .firmly pressed against the surface of the wall, floor, beam, or other kstructural member or fixture which is to be penetrated by the driven stud. For convenience in this specification angl the claims appended thereto, any member to which the tool is applied for the purpose of securing a stud therein will, in accordance with well-established practice, be referred to as the wor,. Since the work is usually a hard and difiicultly penetrable material, it becomes important to insure that the tool be so applied to the lwork surface that the Stud is driven in a direction substantiallyrerpendicular to said surface rather than oblique thereto. The invention of the prior Catlin patent above referred to provides not only that the tool must be held against the work, but that it must be held substantially perpendicular to the work surface to enable rotation of the scar 9 to firing position.

Y To this end, two assemblies were provided in the prior patented Catlin construction, one an action tube assembly or action member comprising action bar 20, action tube 19, and action tube extension 21; and the other, a shield assembly slidably mounted on the action tube extension 21.

i Our present invention is an improvement in the shield assembly and is mounted in an equivalent fashion i be capable of sliding over the end of the barrel 1. The preferred embodiment of our new shield assembly comprises a sleeve'v 623 secured by bravzing or other equivalent means to a top plate 624, which assembly is slidably mounted on the action tube extension 21 with limited capacity for longitudinal movement thereon as a result of theinterengagement of the stop pin 6.233 and groove 62324. If desired, there may be secured to the forward or work contacting face of the topfplate 624 a pad 6,241 of neoprene-or other heavy rubberlike, impact-resistant material.- The top plate 624 and the pad. 6241 thus form a unitary shieldV plate structure. A spring A2.3.4 may be received on the action tube extension bearing on the housing. 16 and on the top plate 624 tending to hold the shield assembly in a forward position relative to the housing 16, as inA the parent application, although such a spring is. not essential to the operation of this modification.

Mounted on the top or rearward surface of the topplate 62,4 are several, for example four, posts 6250 each passing through an aperture in a tab 6252, preferably integral with the skirt 6:25. A spring 62,53 surrounding each post 6250 bears on each tab 6252 and urges the bottom edge 62,51 of the skirt to project in advance of the face of the pad 6241 to the limit provided by the engagement of the tabs 62,52 with the top or rearward face of the top plate 6.2.4-

Insofar as operation ofthe safety devices is concerned, the operation of this form of shield is identical with that of the two prior patents referred to and to the application of which this is a continuation-impart. To minimize the need for reference to those patents, however, the operation of the safety devices` will be briefly discussed here.

Fig. l shows the shield assembly comprising thev sleeve 623, top plate 624, and skirt 625 in their normal extended position on the action tube extension 2l. The action tube volume of less than one cubic inch.

assembly is in its foremost position with respect to action tube cover 16 and the action bar 20 is spaced some distance away from the sear lock 14. Fig. 3 shows diagrammatically the position of these parts when the tool is pressed against a solid surface in a position inclined to such surface. A small portion only of the periphery of the edge of the face of pad 6241 engages the work surface W. This engagement stops forward lmovement of the shield assembly which overcomes spring 234 until shoulder 6231 of the shield assembly .engages the forward end 161 of the action tube cover. As seen in Fig. 3, the act-ion tube assembly has been partially displaced, but still projects forwardly from the shield face into engagement with the work face W and, due to its forward positioning with respect to the fire control, the action bar 20 has not moved thc scar lock 14 far enough to permit the cartridge to be tired. Fig. 4 shows the tool pressed against a work face in a position perpendicular thereto. The end of the action tube assembly, in addition to the entire periphery of the pad 6241, has engaged the work and,

. due to this engagement, the action tube assembly is rearwardly displaced within the shield assembly and the housing 16 to the extent necessary to bring the action bar 2t) into engagement with and displace the scar lock 14, to an extent sufficient to clear the seat 9 and permit tiring movement of the scar. Any desired variation in the range of angles departing from the perpendicular and within which tiring is still possible may be provided merely by varying the over-all length of the action tube assembly.

In our consideration thus far the present invention functions exactly as did that of the prior Catlin invention previously referred to herein. Upon ring of the cartridge, however, the improved features of our present invention come into play. In accordance with wellknown physical principles, the projection of any missile, such as the stud projected by the Walker tool, is accompanied by an equal and opposite recoil reaction which may be resolved into a reaction component due to projection of the mass of the stud and a reaction component due to gas blast during the expulsion at extremely high velocity of a charge of gas having a weight equal to that of the powder charge. With the Walker tool, the total recoil reaction, which is the sum of the two cornponents, is primarily exerted upon the barrel, which is thus forcibily retracted within the action tube and action tube extension away from the surface of the work, providing a chamber which, at maximum retraction, has a With the Walker tool, when the barrel has recoiled to an extent such that the inner surface of the housing 16 is again engaged by the forward end of the action tube 19, the action tube extension is pulled away from the surface of the work by the recoil of the barrel and the propellant gas confined therein escapes laterally at the face of the work. This much of the action on ring is common to the Walker tool and to the prior Catlin improvement.

In this application, as in the prior Catlin improvement, when the recoil reaction exertedl on the barrel tends to lift the housing 16 and action tube extension 21 away from the work surface, these members no longer exert any restraining influence upon movement of the top plate 624- and pad 6241 away from the work surface. These members andthe sleeve 623i will therefore tend to raise from the work surface to the extent permitted by recoil of the action tube extension 21 and the inter-connection between the pin 61233 and groove 6232, for gas escaping from the muzzle of the barrel will be expanding between the work surface and the surface, of the pad 6.241.

This expanding gas and any fragments of gas seal orA work surface carried with it will still be confined. because the skirt 625 is movably mounted on the top plate 62,4, and urged by the springs 6253 to project forward in advance.- of the, pad 6,2;41 with the. edge 6251 remaining in contact with the work surface. Thus., the top plate 62.4.- and pad 624.1together with the skirt 625 and the work surface, form a substantially closed chamber within which the blast of gas from the muzzle of the barrel may dissipate its energy as work in lifting the top plate 624, by cooling, and by leakage at the edges of the top plate 624 and between the edge 6251 and the work surface.

We have found that, if the closed chamber so created has a volume of at least four cubic inches, e. g., 4 square and 1A extension of the skirt in advance of the face of the pad 6241, it is quite effective in retaining the larger and more dangerous fragments of spall, etc. If the chamber so created has substantially less than this enclosed volume, we have been unable to discern any practical advantages not shared by the flat pad guards of the prior art. Increasing the chamber volume renders the guard much more effective, one having a volume of 24 cubic inches (e. g. 4 square and with 11/2 extension of the skirt in advance of the pad 6241) appeared to retain the edge 6251 in substantial contact with the work throughout the firing cycle, retained both large and small particles of spall, and showed a clear and denite 4" square pattern of accumulated dust when the tool was removed from the work surface. If anything, the action of the composite guard was more effective than that of the solid box claimed in the parent application, probably because of the expenditure of energy in the escaping gas at the muzzle of the barrel in doing work in lifting the pad 6241 and top plate 624.

The top plate 624 and skirt 625 are necessarily made of fairly heavy steel or other material which will be resistant to the impact of a possible ricocheting stud.

Narrow vent slots may be cut in the peripheral skirt walls with some lessening of the tendency of relatively low volume shields to separate from the work surface, but such vents should be so small that no dangeous particle could be projected therethrough. With charnbers of a volume of 16 cubic inches or more, the provision of vents does not seem to provide any useful result. However, with this design some venting of gas is possible at the periphery of the pad 6241 and top plate 624 and this escape also reduces any tendency to lift the top plate 624 so high as to pick up the skirt 625 and lift it from the work surface. To avoid any danger of dust particles being carried back to an operator by gas escaping at the periphery of the top plate 624, we prefer to provide an inturned flange 6254 on the upper edge of the skirt 625.

Obviously, other equivalent means may be provided to spring mount a skirt such as 625 and urge it to remain in contact with a work surface while the rest of the shield recoils, and we contemplate that such equivalent springing systems are within the purview of our invention.

Although we have specifically shown only on modification of our device, we do not intend that our invention should be considered as' limited thereto. For an exact definition upon the limits of our invention, reference may be had to the appended claims.

As used in this specification and the claims hereafter, the terms forward and rearward are oriented with respect to the direction in which a fastening device is projected from the barrel. Thus, the rearward end of the barrel is the breech end into which the propellant cartridge is loaded and the forward end of the barrel is the muzzle end from which the fastener is projected.

We claim:

1. In a stud driving tool having a barrel through which a fastening device may be projected into a work surface by the combustion of an explosive propellant, a safety shield comprising in combination a shield plate structure having a barrel aperture, mounting means on said tool supporting said shield plate structure normal to said barrel with said aperture surrounding said barrel, a skirtlike 6 l member having a dependent work surface contacting edge, said shield plate structure being marginally enclosed by said skirtlike member and recprocable therein from a tool firing position in which a face of Said shield plate structure is in engagement with said work surface in the plane of said work surface contacting edge to a chamber forming position in which said shield plate structure is recessed with respect to said work surface contacting edge and forms with said skirtlike member a hollow chamber surrounding the muzzle end of said barrel, spring means engaged between said skirtlike member and said shield plate structure for yieldably urging said skirtlike member and said shield plate in opposite directions of movement to chamber forming position, said spring means thereby retaining said dependent work surface contacting edge of said skirtlike member against a work surface as said shield plate structure is moved from said tiring position by the explosive propellant forces incidental to the projection of a fastening device.

2. In a stud driving tool having a barrel through which a fastening device may be projected into a work surface by the combustion of an explosive propellant, a safety shield comprising in combination a tubular sleeve surrounding the barrel at the muzzle end thereof, a shield plate structure mounted on said sleeve normal to said barrel for engagement with the area of said work surface surrounding said barrel muzzle, a skirtlike member having a dependent work surface contacting edge, said shield plate structure being marginally enclosed by said skirtlike member and mounted for reciprocation therein from a tool tiring position in which said shield plate structure is in engagement with said work surface and is co-planar with said work surface contacting edge to a chamber forming position in which said shield plate structure is recessed within said skirtlike member and forms with said skirtlike member a hollow chamber surrounding said barrel muzzle and adapted to confine material displaced by the projection of a fastening device, spring means operatively engaged between said skirtlike member and said shield plate structure lyieldably urging said skirtlike member and said shield plate structure in opposite directions of movement to said chamber forming position, said spring means thereby retaining said work surface contacting edge of said skirtlike member in contact with said work surface as said shield plate structure is moved from said tool firing position to said chamber forming position by the explosive propellant forces incidental to the projection of a fastening device.

3. A safety shield as defined in claim 2, said skirtlike member projecting forward relative to said shield plate structure when in said chamber forming position by an amount suicient to laterally enclose a space having a volume of at least four cubic inches.

4. A safety shield as defined in claim 8, the rearward edge of said skirtlike member being formed to provide an inturned flange which in said chamber forming position partially overlaps and is in engagement with the rearward surface of said shield plate structure.

5. A safety shield as dei-ined in claim 4, said shield plate structure being provided with rearwardly extending posts projecting from its rearward surface and said skirtlike member being provided with inturned tabs having apertures through which said posts may pass to guide said skirtlike member for reciprocation relative to said shield plate structure.

6. A safety shield as defined in claim 5, said spring means comprising compression springs received on said posts and engaged between the rearward surfaces of said tabs and headed means provided on the rearward end of said posts.

No references cited

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