Impact stapling method

Abstract

Method of impact stapling with an impact stapler having a staple with integral pointed target-penetration and securing forward section, rear hammer section, and medial compression shear section, the forward section having a threaded object-securing surface rearwardly of its pointed forward target-securing end. The staple is propelled into a target by a percussion-ignited propellant charge, and the forward section is secured by initial point penetration and subsequent compression shear of the medial shear section to enable the hammer section to impart a secondary securing impact to the forward section.

Parent Case Text

This is a division of application Ser. No. 334,397 filed Feb. 21, 1973 now abandoned, which in turn is a division of application Ser. No. 180,333 filed Sept. 14, 1971, now abandoned.

This invention relates to a method of stapling with impact stapling arrangements which may be utilized to effect securing of an object to a target piece which may be formed of high-strength relatively low-elasticity steel or the like.

Hand-held staplers have heretofore been made for attaching a metal sheet or other object, such as a bracket, to a target in the form of a steel plate, such conventionally incorporating a high-strength steel stud stapled to the target and utilized as a bolt or tension member to fasten metal sheets, brackets, or other items to the target. A primary problem associated with this type of connection is the fastening or retention of the stud to the target. This has been accomplished by the partial penetration and embedment of a knurled tapered point end on the stud staple into the target material, utilizing a hand-held holder and propellant powder for imparting stud penetration. Typical stud firing velocities of 750 to 800 feet per second have been utilized with hand-held stapling arrangements. At this velocity, the stud staple may penetrate the target sheet to a depth of 0.4 inches, which is a sufficient depth to imbed the point and knurled surface thereon into a target sheet of relatively low-strength, high elasticity steel, and thereby achieve a nominally satisfactory structural joint between the stud staple and the target sheet. In this respect, the stud is retained in the target material of this type due to the ability of the elastic target material to deflect in a radial direction during stud penetration and then to elastically flow back over the stud knurl, thereby entrapping the stud in the target sheet. The target material entrapping the knurled point stud staple with the target provides a stud retention which will resist tension pull-out loads of a sometimes acceptable order of magnitude, as for instance up to 2200 pounds. However, with the prior art methods and arrangements of this type, such have been found to be useful only in low-strength steel target plates of up to 1 inch thickness, as above this thickness the rebound energy of the stud is of such a magnitude that it exceeds the transient gripping forces during penetration and rebound, and results in the stud bouncing out of the hole or its being loose in the target material, with relatively low and ineffective joint strength.

This prior art stapling arrangement and method depends on the elasticity of the steel target material in order to achieve intimate material contact between the knurls of the staple and the hole surface of the target material. It is also dependent on the area of this contact in order to provide a joint of effective structural quality. Among the disadvantages inherent in this prior art method of stapling, in addition to those noted above, are that the knurled stud point used for joint connection is inherently an inefficient penetrator which must be of sufficient size and driven to a sufficient depth in the steel target so as to insure that the knurls of the stud are effectively engaged by the target material.

To attempt to drive this inefficient configuration into a steel target requires a high level of energy to achieve the necessary stud velocity. To increase the capability of this prior art device so as to afford greater stud holding power with a given target material, or with respect to its use against targets of thicker steels and/or higher strength steels, would require even higher levels of energy, which levels of energy would produce excessive recoil loads for hand-held operation, which is a particularly desirable form of operation in some instances such as in underwater use. In addition, such higher levels of energy being imparted to the stud staple impose stringent design criteria on the stud staple firing device and produce high structural loads on the stud staple during penetration, which high structural loads may cause unpredictable degradation of the stud staple. In addition, in utilizing this prior art arrangement the steel target material must be sufficiently elastic to properly engage the knurls of the stud penetrating section, and this condition precludes its use for stapling to higher strength but less elastic steels, as the strength of the joint is relatively low in such instances, if the joint is effective at all, as the joint strength is basically determined by the small amount of target material which entraps the stud knurl. Further, this prior art arrangement provides essentially little or no capability for fastening to steel target plates of 1 inch or thicker, even with relatively low-strength more elastic steels.

It is an object and feature of this invention to effect a substantial improvement in the stapling methods, and particularly to provide a method utilizing arrangements which may be hand-held in order to achieve higher strength joints in relatively high-strength steels, independent of thickness, with energy requirements compatible with hand-held operation.

It is a further feature to provide an improved staple method which enables the utilization of a smooth pointed penetrator as the joint connection, without the requirement for knurls or the like at the zone of joint connection between the target and the stud staple, and in which the stud staple may be effectively secured to target materials of high-strength low-elasticity steels and/or steels of infinite thickness.

Still a further feature is the provision of a stapling method which is employed in conjunction with a staple so as to cause the staple to impart a self-operated secondary impact for improved fastening to a target.

A further object and feature is the provision of an improved impact stapling or nailing method employing secondary self-impacting of a penetrator section of a staple or nail after and as a function of external drive-impacting of the staple or nail.

Description

Still other objects, features and attendant advantages will become apparent to one skilled in the art from a reading of the following detailed description of a preferred mode of practice in accordance with the invention, taken in conjunction with the following drawings wherein:

FIG. 1 is a longitudinal section view of a stapling or nailing arrangement employed according to the invention.

FIG. 2 is a fragmentary side view of the upper section of the arrangement of FIG. 1, taken as viewed from the righthand side of FIG. 1.

FIG. 3 is an enlarged view in perspective of the firing pin in the arrangement of FIG. 1.

FIGS. 4, 5 and 6 are schematic section views illustrating sequential steps in the method according to the invention, utilizing the arrangement of FIG. 1 in securing the stud staple to a target plate.

FIGS. 5a and 6a are enlarged views in partial section of the medial shear section of the staple or nail during carrying out of the method according to the invention, and corresponding to the shear rupture and secondary self-impacting conditions illustrated respectively in FIGS. 5 and 6.

Referring now in detail to the Figures in the drawings, a staple cartridge arrangement for utilization according to the method invention is generally indicated by the reference numeral 11, and includes a cartridge barrel 13 having a frangible seal 15, and within the bore 13a of which is disposed a staple or nail generally indicated at 31, which in turn is secured as by a retaining pin 39 to a pusher generally indicated at 41. Pusher 41 is in turn connected through a shear pin 49 to a propellant cup base 51 which is threadedly secured in the rear end of barrel 13, and which houses a percussion primer 53 and charge of ignitable propellant mix 55.

The cartridge 11 is removably secured within the bore 91a of a hand-held holder 81 which is closed at one end by closure member 85, formed of material such as steel, or other material suitable to enable member 85 to serve as a jam washer or nut portion of a threaded unit connection with the staple 31. Closure 85 is press-fit into the lower open end of holder 81, and may be removed in the course of firing and securing of the staple to a target sheet or thereafter by simply rocking the holder 81 after target securement. To this end, the closure 85 has a central recess 85b on its interior face, which recess is preferably of sufficient cross section to accommodate passage of the smooth pointed penetrator section 31a of the staple 31 and of less diameter than the outer thread diameter of a threaded securing section 31b rearward of the tapered point 31a. A puncturable closure membrane 85a is formed across the bottom of the recess 85b, and is punctured by the staple 31 in the course of firing the cartridge 11, the walls of recess 85a then engaging with threaded securing section 31b.

Securing of the cartridge 11 within the holder 81 is suitably effected by set screws 91 which engage with the exterior of the cartridge 11 rearwardly of a damping and center ring 16. A guard 87, with O-ring seals 89, may be secured over the area of set screws 91, through the medium of a set screw 93, thereby affording a substantially water-tight seal at this point between the bore 81a of the holder 81 and the exterior of the holder, and enabling the device to be more advantageously used underwater if so desired.

Disposed rearwardly of the cartridge 11 in the bore 81a is a firing pin which is held in the cocked position as shown in FIG. 1, against the action of compression spring 65, through the medium of a retention/release pin 71. The retention/release pin 71 is held in the retention position by a safety handle 101 which longitudinally slidably engages therewith from the lower side, the safety handle 101 having a bifurcated end which extends between the enlarged head of the pin 71 and the exterior body of handle 81 to prevent movement of the pin toward the handle 81 until removal of the handle is effected preparatory to firing. A safety pin 103 extends through lateral holes in pin 71 and handle 81, and may be selectively removed by exerting a pulling force thereon with a pull ring 105, after which the safety handle may be slid downwardly along the holder 81 for removal. In the normal safety position, the safety handle is prevented from being angularly moved about the axis of pin 71, through engagement of a pin 101a on the safety handle with a guide slot 81b on the outer surface of the handle 81.

The actuator retention/release pin 71 retains the firing pin 61 in the cocked position by engagement of retention sections 73 thereof with enlarged release holes 61r, 61R' formed in the opposite walls of cup-shaped firing pin 61, these retention holes being best seen in FIG. 3, and the retaining relationship being illustrated in FIG. 1. Immediately adjacent the retention sections 73 of pin 71 are reduced neck release sections 75, which are of sufficiently small diameter to pass freely through release slot sections 61b, 61b' formed in the upper end of the cup-shaped firing pin 61, to thereby enable the firing pin to move downwardly upon the movement of the release pin 71 to the left by a small incremental extent after removal of the safety handle 101. The reduced neck release sections 75 are caused to be in registry with the release slots 61b, 61b' by engagement of a shoulder stop 72 on the release pin 71 with the exterior surface of handle 81 when the pin 71 is moved to the left, as viewed in FIG. 1. O-ring seals 77 may be employed adjacent the internally opposite ends of pin 71 to afford water-tight sealing of the interior bore 81a of handle 81.

Upon registry of the reduced neck release sections 75 of pin 71 with the enlarged retention holes 61r, 61r', the firing pin will move forward under the influence of the compression spring 65, being guided in this respect by a set screw guide pin 94 which slidably engages with guide slot 61a formed as a lower extension of release slot 61b and enlarged retention hole 61r in the firing pin 61. The firing pin 61 may have one or more fluid bypass orifices 63 formed in its forward end to enable fluid pressure equalization, and thereby enable full utilization of the firing pin force exerted by compression spring 65.

Upon impacting of the firing pin 61 with the primer 53 the propellant mix 55 will be ignited to effect shearing of the shear pin 49 and movement of the pusher 41 and staple 31 downward as viewed in FIG. 1, it being appreciated that the reference to direction as being downward is only with respect to the Figure and does not indicate that the device will or must be fired in any given position. The device is capable of operating in any orientation relative to a given target to which it is desired to secure the staple 31 and closure nut member 85.

Pusher 41 has formed on its outer annular surface a series of sealing and shear stop rings 41b which are separated by annular grooves 41a, these rings and grooves serving the dual purpose of aiding in sealing the propellant gases and also enabling final energy absorbing stopping and retention of the pusher 41 within the forward end of cartridge 11. To this end, there is formed at the forward end of bore 13a in cartridge barrel 13 a shoulder stop 11a which enables the free passage therepast of the staple 31, while engaging the shear stop rings 41b, thereby causing the rings 41b to be sheared as the pusher 41 attempts to move therepast, the number of rings being sufficient to absorb the remaining energy in the pusher 41 after staple 31 is secured to the target, and to retain the pusher within the cartridge barrel 13 at the end of the firing sequence.

As noted heretofore, the staple or nail 31 is formed with a penetrator section 31a which takes the preferred form of a smooth tapered securing point 31a, rearwardly of which is a threaded securing section 31b which is of substantially constant thread diameter along its length, to thereby simulate a threaded stud end when the staple 31 is embedded in a target sheet, with the threaded securing section 31b protruding on the exterior of the target. The staple 31 is formed as an integral unit with a rear hammer section 31d connecting with the forward penetrator section 31a and threaded securing section 31b through a reduced diameter shear section 31c. A plug 42 may be employed, if desired, rearwardly of hammer section 31d to absorb shock and forward motion force between the hammer section 31d and pusher 41.

The reduced diameter shear section 31c is formed with a sufficient diameter to provide the necessary column strength between the penetrator and threaded nut or washer-securing sections 31a, 31b on the one hand and the hammer section 31d on the other hand, to insure that the necessary precise force is imparted from the pusher 41 to the penetrator section 41a to afford desired penetration of the point 31a into a target sheet. With a high tensile steel target (eg 100,000 psi ultimate tensile strength), a desired and proper extent of penetration by a point having a length of 0.45 inch and a rear diameter of 0.230 inch, has been found to be approximately 0.35 inch. To effect this extent of penetration, using a one-piece high-strength steel (eg, maraging steel 300) staple 31, a diameter of approximately 0.150 inch for the frangible section has been found satisfactory, with a 0.280-inch diameter hammer section 31d and threaded securing section 31b thereadjacent. After the proper depth of penetration of point 31a has been effected during initial impact, increased resistance by the target to further point penetration causes the frangible reduced diameter shear section 31c to fail in compression shear, and the hammer section 31d will continue forward to impart a further secondary impact to the rear of the integral point and threaded securing sections 31a, 31d, as illustrated in FIGS. 5 and 6 respectively, as well as enlarged FIGS. 5a and 6a, the shear rupture zone being indicated schematically at 31cs, FIGS. 5 and 5a being schematically illustrative of the secondary impacting effected as a result thereof, by the hammer section 31d.

As will be seen from FIGS. 4-6, the penetrator section 31a of staple 31 passes through closure membrane 85a and the object, such as a metal sheet 121, which is to be attached to a target plate 131, causing lateral displacement of each of the closure membrane 85a, the metal object sheet 121 and the metal target plate 131, an effective degree of penetration being illustrated in FIGS. 5 and 6, at which point the threaded section 31b is in radial jam engagement with the walls of closure member recess 85b, and the smooth tapered point section 31a is engaging with the metal sheet 121 and the target plate 131. At this position, the resistive forces of the target plate 131 are sufficient to overcome the column strength of the shear section 31, thereby effecting the shear rupture as indicated at 31cs. The remaining kinetic energy of the pusher 41 and hammer section 31d will thereupon cause the hammer 31d to effect a secondary impact on the rear end of the penetrator and threaded securing sections 31a, 31b, to thereby prevent the penetrator point section 31a from bouncing out of its penetration contact with the target 131, and also affords a further securing action at the point of contact with the point section 31a and the target 131. The thus embedded point is effectively secured with the target plate, being frictionally secured and apparently to some extent welded to the target material. It has been found that with an arrangement of this nature the staple may be effectively secured to withstand an axial pull of approximately 6,000 pounds, and such has been successfully used as a fastener to mild steel, 4130 steel, HY80 steel, and HY100 steel, in thicknesses ranging from 3/8 inch to effectively infinite thickness.

While the invention has been described with respect to its practice with a single preferred embodiment, it will be apparent that various modifications and improvements will be made without department from the scope and spirit of the invention. For instance, while the method is described and illustrated as applied with an illustrative apparatus in which there is disclosed a particular means for actuating the latent energy means, it is not necessary that such be a part of the manufactured apparatus, nor that such be sold or furnished to a user with such an actuating means. The actuating means could be added or supplied later at time of use, or actuation could be accomplished manually as with a manually wielded hammer or other impact, electrical, chemical reaction, or other desired type of device, which might suitably fire or otherwise actuate a primer, propellant charge, spring, or other latent energy means. Various separate auxiliary apparatus, both mechanical and electrical, for firing or otherwise actuating primers, propellant charges, etc., or other latent energy means, are well known, as in the ordnance art, and are not necessary to be described for an understanding of this invention as to scope or manner of alternative practice thereof by one skilled in the art. Additionally, while the illustrative apparatus utilized in carrying out the method employs latent energy means in the form of ignitable propellant, it will be appreciated that other latent energy means might suitably be employed, such as a spring, a selectively releasable suspended weight movable under force of gravity, a chemical composition or compositions which generate useful energy such as gases and/or heat upon selective chemical reaction, etc. Further, while practice of the method with the specific illustrative apparatus has been illustrated and described, and has been found to be a desirable mode of practice, and while various detailed features of such apparatus may themselves be additionally novel and inobvious, the broad invention of my double impact nailing method with an impact-compression-shearable double impact nail unit clearly does not require the particular structural arrangement of the illustrative apparatus, such as the sealed barrel 13, hand-held holder 81, cartridge 11, pusher 41, primer-ignited propellant powder latent energy means 55, safety firing pin arrangement 63, 73, 75, 101, 105, or energy-absorbing shear ring arrangement 41b, 11a. For example, for normal use outside of underwater use, a sealed barrel is not necessary, and the initial external drive force for imparting initial penetrating velocity to the staple or nail unit may be imparted directly to the nail unit without use of a pusher 41, as by a spring, a weight imparted thereagainst, or a chemical or electrical energy-generating and force-transmitting reaction. Accordingly, the invention is not to be limited by the illustrative embodiment, but only by the scope of the appended claims.

Claims

I claim:

1. The method of attaching a staple unit to a target, comprising

imparting a forward velocity to an impact staple having a forward point section, a hammer section and a medial compression shear section between said point section and said hammer section, said forward velocity being in the direction of a target mass,

impacting said staple unit at its forward point section with said target mass,

compression shearing said medial compression shear section by inertial mass kinetic energy action of said hammer section on the rear of said shear section upon impact of said forward point section with said target mass,

and forwardly impacting said forward point section by the continued forward inertial mass kinetic energy movement of the resultant compression-shear-separated rear hammer section of said staple.

2. The method of attaching a staple or nail unit to a target, comprising

imparting a forward velocity to an impact staple or nail having a forward point section and a rear inertial mass hammer section, said forward velocity being in the direction of a target mass,

impacting said staple or nail unit at its forward point section with said target mass,

compression shearing said staple unit intermediate said forward point section and said rear inertial mass hammer section by inertial mass kinetic energy action of said hammer section upon impact of said forward point section with said target mass,

and forwardly impacting said forward point section by the continued forward inertial mass kinetic energy movement of the resultant compression-shear-separated rear hammer section of said staple or nail.