Nail Feed Mechanism

Abstract

A mechanism for feeding successive fasteners from a fastener package into a position to be driven by a fastener driving element during the drive stroke thereof, the fastener package being in the form of a coil of circular headed nails flexibly interconnected in series with their shanks in spaced parallel relation, the mechanism including a nosepiece assembly defining an elongated drive track receiving the fastener driving element therein during the operating cycle thereof and a nail feeding track communicating laterally with the drive track, and a ratchet type feeding mechanism for feeding successive fasteners within the nail feeding track into the drive track, including a spring pressed feeding pawl carried by a reciprocating actuating member and a pivoted spring pressed holding pawl provided with surfaces for laterally substantially closing the drive track at the position of communication with the nail feeding track, the feeding pawl having a first feeding surface for engaging the trailing surface of the shank of the second nail to move the second nail forward in the nail feeding track during the drive stroke of the feeding pawl and hence the leading nail into the drive track due to its interconnection with the second nail, the feeding pawl also having a second feeding surface for engaging the last nail and moving it partially into the drive track, the juncture between the drive track and the nail feeding track having a cam surface for camming the partially positioned last nail fully into the drive track during the initial movement of the fastener driving element through its drive stroke.

Description

This invention relates to fastener containing and feeding mechanisms for fastener driving devices and more particularly to such mechanisms for containing a fastener package in the form of a strip of circular headed nails interconnected in series with their shanks in spaced parallel relation and for feeding successive fasteners from the package into the drive track of the device.

Nail feeding mechanisms embodying a nail feeding pawl provided with a surface for engaging the trailing shank surfaces of the leading nail in the nail feeding track are known in the art. At the end of the nail feeding stroke of such a nail feeding pawl, the shank engaging surface thereof is disposed within the drive track at a position beneath the trailing portion of the circular head of the nail therein. Because of this relationship of the nail feeding pawl within the drive track, it is essential to provide for a rapid return stroke of the nail feeding pawl in order to prevent interengagement of the nail head therewith during the driving movement of the latter. Where air under pressure is utilized as the means for effecting the return stroke of the nail feeding pawl, the rapidity at which the return stroke can be initiated tends to vary in accordance with source pressure. Thus, where lower source pressures are utilized or occur interference tends to take place.

There are many feed mechanisms proposed in the patented prior art which embody some arrangement for obviating the problem noted above relating to nail head interference with the feed pawl. Some systems propose utilizing a feed pawl which is retained within the drive track but mounted so as to be moved out of the drive track by engagement of the nail head therewith. Such an arrangement suffers from the disadvantage of excessive wear due to impact, thus detrimentally affecting the endurance and reliability of the feed mechanism.

Other proposals include the repositioning of the feed pawl rearwardly in the nail feeding track in spaced relation from the drive track so as to engage the fourth and fifth nails in the package. However, since an arrangement of this type is incapable of feeding the last nails of the package into the drive track, a mechanism must be provided for preventing actuation of the device when the last nails of the package remain in the nail feeding track.

The present invention is based upon the principle that the aforesaid nail head interference problems can best be overcome by positioning the nail feeding pawl so as to engage the second nail in the nail package during the feeding stroke thereof and providing the nail feeding pawl with a second nail shank engaging surface positioned forwardly of the surface which engages the shank of the second nail at a position such as to be disposed within the area of communication between the drive track and the nail feeding track when the nail feeding pawl reaches the end of its nail feeding stroke. This leading nail shank engaging surface on the nail feeding pawl thus never moves into a position of engagement within the drive track but still functions to insure that the leading nail and specifically the last nail of the package will always be moved at least into a position with respect to the drive track in which its shank is wholly disposed therein. The present arrangement contemplates cam surfaces at the juncture of the nail feeding track and drive track for engaging the head of a leading nail thus partially disposed within the drive track so that, during the drive stroke of the fastener driving element, the nail will be cammed fully into the drive track for accurate and positive movement into the workpiece.

Accordingly, it is an object of the present invention to provide a nail feeding mechanism of the type described which obviates the problem of head interference in the manner set forth above and which operates in accordance with the principles set forth above.

Other objects of the present invention will become more apparent during the course of the following detailed description and the appended claims.

The invention may best be understood with reference to the accompanying drawings wherein an illustrative embodiment is shown.

In the drawings:

FIG. 1 is a side elevational view of a fastener driving device, with parts broken away, embodying the principles of the present invention;

FIG. 2 is a top plan view of the device shown in FIG. 1;

FIG. 3 is a front elevational view of the lower portion of the device of the present invention including the fastener containing and feeding mechanism;

FIG. 4 is a fragmentary side elevational view of the fastener feeding mechanism illustrating the same in its opened loading position;

FIG. 5 is an enlarged fragmentary sectional view taken along the line 5--5 of FIG. 3 showing the position of the parts in their normal inoperative position;

FIG. 6 is a veiw similar to FIG. 5 showing the position of the parts during the return stroke of the actuating means; and

FIG. 7 is a view similar to FIGS. 5 and 6 showing the position of the parts during the operative stroke of the actuating means.

Referring now more particularly to FIGS. 1-4 of the drawings, there is shown therein a fastener driving device, generally indicated at 10, having a fastener containing and feeding mechanism, generally indicated at 12, embodying the principles of the present invention. The device 10 includes the usual fastener driving element 14 which is moved through an operating cycle including a drive stroke and a return stroke preferably by a conventional pneumatic system (not shown). It will be understood that any type of pneumatic system may be utilized, as for example, the system disclosed in commonly-assigned application Ser. No. 843,665, filed July 22, 1969, for FLUID PRESSURE OPERATED FASTENER DRIVING DEVICE, now U.S. Pat. No. 3,572,572, issued Mar. 30, 1971. While pneumatic systems are preferred, other systems for effecting the cycle of operation of the fastener driving element may be utilized as, for example, electrical systems, hammer actuated systems, spring actuated systems and the like.

The fastener mechanism 12 of the present invention is useful in handling and feeding fastener packages in the form of a strip of circular headed nails interconnected in series with their shanks in spaced parallel relation, either of the rigid stick form, although particularly suited for the flexible coil or folded form.

Fastener packages of the preferred type are well known in the art. One example of a fastener package of this type is disclosed in commonly-assigned Peterson U.S. Pat. No. 3,083,369 dated Apr. 2, 1963. Other examples of fastener packages of this type are disclosed in the following U.S. Patents: Nos. 3,276,576; 3,338,396; 3,357,761; and 3,442,374. The Peterson patent, as well as U.S. Pat. No. 3,276,576, discloses fastener packages of both the rigid stick form as well as the flexible coil form. Other examples of rigid stick type packages are illustrated in the following U.S. Pat. Nos.: 3,212,632; 3,349,899; 3,358,822; 3,463,304; and 3,471,008.

The mechanism 12 includes a nosepiece assembly, generally indicated at 16, defining an elongated drive track, generally indicated at 18, for receiving the fastener driving element 14 during the operating cycle thereof and a nail feeding track, generally indicated at 20, communicating at one end laterally with the drive track.

The nail feeding mechanism 12 also includes a nail feeding means, generally indicated at 22, a nail holding means, generally indicated at 24, cooperable with the nail feeding means 22 and an actuating means, generally indicated at 26, movable through an operating cycle including a feeding stroke and a return stroke for effecting a movement of successive fasteners through the fastener feeding track and into the drive track. As shown, the mechanism 12 also includes a magazine assembly, generally indicated at 28, disposed in communication with the other end of the nail feeding track for supporting the coil form of the package with the leading portion of the strip extending into and through the nail feeding track.

As best shown in FIG. 4, the nosepiece assembly 16 includes a fixed part 30 and a movable part 32. The fixed part is formed with an upper horizontally extending base portion 34 detachably rigidly connected to the housing of the fastener driving device 10 by any suitable means as, for example, bolts or the like (not shown).

The terms "upper" and "horizontally," as well as other terms such as "above," "below," "vertical," "forward," "rearward," as used hereinafter are to be construed in their relative sense. Thus, for convenience, the device 10 will be described in an orientation operable to drive fasteners downwardly into a horizontal workpiece, although it will be understood that the device is not limited to such application but can be used to drive fasteners into vertical workpieces or beneath horizontal workpieces, as well as workpieces of any other orientation.

Extending downwardly from the base portion 34 is a vertical wall portion 36 having a vertically extending surface 38 of concavely arcuate cross-sectional configuration formed in alignment with a circular opening 40 extending through the base portion 34. The lower end of the surface 38 merges into the interior cylindrical surface of a lower sleeve portion 42 formed integrally on the fixed part 30 in depending relation thereon. The surface 38 as well as the surfaces forming the openings at each end thereof define a part of the drive track 18. The wall portion 36 also includes a recessed central vertical surface 44 defining a complementary shank receiving portion of the nail feeding track 20. The upper end of the surface 44 communicates with a generally horizontally extending surface 46 of concave U-shaped cross-sectional configuration, defining a complementary head receiving portion of the nail feeding track 20 which converges forwardly from its rearward end.

Formed on the end of the wall portion 36 adjacent the drive track defining surface 38 and extending outwardly therefrom is a pair of vertically spaced pivot lugs 48. The movable part 32 is, as shown, in the form of a wall portion similar to the wall portion 36 having three vertically spaced complementary pivot lugs 50 formed on one end thereof. The lugs 48 and 50 as well as the base portion 34 are vertically apertured to receive a pivot pin 52 (FIGS. 5-7) which serves to mount the movable part 32 for pivotal movement on the fixed part 30 between an opened access position, as shown in FIG. 4, and a closed nail feeding position, as shown in FIGS. 1-3.

As best shown in FIG. 4, the movable part 32 is provided with a complementary drive track defining vertical surface 54 similar to the surface 38. Also as before, the movable part 32 includes a horizontally extending surface 56 defining a forwardly converging complementary head receiving portion of the nail feeding track 20 and an adjacent recessed surface 58 defining a complementary shank engaging portion of the nail feeding track 20.

The nail feeding means 22, as shown, is preferably in the form of a U-shaped pawl member 60 formed with angularly extending leg portions guidingly received within a pair of horizontally extending openings 62 formed in the vertical wall portion 36 of the fixed part 30. Each of the angularly extending leg portions of the pawl member 60 is provided with a pair of parallel leading and trailing nail feeding surfaces 64 and 66 facing in a direction toward the drive track and extending transversely across the nail feeding track. The trailing feeding surface 66 is operable to engage the trailing surface of the shank of the second nail disposed in the nail feeding track. The leading nail feeding surface is spaced longitudinally from the trailing surface a distance less than the spacing between the axis of adjacent nail shanks for a purpose hereinafter to be more fully described. Each angularly extended portion 60 also includes a pair of parallel pawl camming surfaces 68 which extend across the nail feeding track in an angular direction outwardly of the U-shaped pawl 60 and toward the drive track so as to engage a leading portion of the shanks of the nails disposed within the drive track.

As shown, the actuating means 26 is in the form of a cylinder 70 formed integrally on the outer side of the wall portion 36. A piston 72 is slidably mounted within the cylinder 70 and has a piston actuating rod 74 formed thereon extending outwardly of the cylinder. The outer end portion of the actuating rod 74 is slidably received within a bearing block 76 detachably mounted, as by a pair of bolts 77 (FIG. 3) extending through apertured flanges in the bearing block and threadedly engaged within a pair of vertically spaced horizontally elongated bosses 78 formed integrally on the outer surface of the wall portion 36 of the fixed part 30. As best shown in FIGS. 5-7, the U-shaped pawl member 60 is disposed in embracing relation to a block portion formed on the actuating rod 74 intermediate its ends thereof and is pivotally connected thereto by a pivot pin 80 extending vertically through suitable apertures formed in the leg portions of the pawl member and the block portion of the actuating rod.

Suitable spring means is provided for resiliently biasing the pawl member 60 into a feeding position wherein the bight portion of the pawl member engages the block portion of the actuating rod 74 and the feeding surfaces 64 and 66 extend across the nail feeding track. While the spring means may take any desired form, the arrangement shown in the drawings is preferred since a single spring means is utilized to perform the dual purpose of resiliently biasing the pawl member into its feeding position and of effecting movement of the actuating rod through its drive stroke. In the embodiment shown, the spring means is in the form of a helical compression spring 82 mounted in surrounding relation to the actuating rod 74 with its rearward end engaging the bearing block 76 and its forward end engaging the rearward surface of an annular flange 84 formed on the forward end of a sleeve element 86. As shown, the sleeve element 86 is slidably mounted on the actuating rod 74 within the spring 82 and the forward surface of the flange 84 engages the rearward surface of the bight portion of the pawl member 60 to effect the resilient bias of the latter into its feeding position. In this way, the spring 82 not only serves to maintain the pawl member 60 in its feeding position but at the same time applies a resiliently biasing force on the actuating rod 74 tending to move the piston 72 into the forward end of the cylinder member 70. The actuating rod is moved through its return against the action of the spring 82 by air under pressure from the pneumatic system of the device. As best shown in FIG. 3, the fixed part 30 of the nosepiece assembly 16 is formed with an integral portion 88 extending between the forward upper portion of the cylinder member and the base portion 34 adjacent the periphery thereof. The portion 88 is provided with a passage extending therethrough which communicates at its lower end with the feed end of the cylinder and at its upper end with the pneumatic system of the device 10 at a location therein which provides for a change in pressure from atmospheric to reservoir during the cycle of operation of the pneumatic system. A preferred example is to communicate the passage with the upper end of the drive chamber of the device.

During the return stroke of the actuating rod 74, the pawl member 60 cooperates with the holding means 24 which, as shown, is preferable in the form of a plate-like holding pawl member 90 disposed within a recess 92 formed in the central portion of the movable part 32. Formed in the rearward end portion of the pawl member 90 is a pair of vertically spaced vertically apertured bosses or lugs 94 defining an opening therebetween for receiving a cooperating vertically apertured lug 96 formed on the adjacent interior surface of the movable part 32. A pivot pin 98 extends through the apertured bosses 94 and 96 and serves to pivotally mount the holding pawl member 90 on the movable part 32 of the nose piece assembly 16 for movement about a vertical axis disposed in spaced parallel relation to the axis of the drive track 18. The holding pawl member 90 is resiliently biased into a nail holding position by suitable spring means which, as shown, is preferably in the form of a spring strap 100 fixed at its forward end to the outer surface of the holding pawl member 90 and having its rearward end disposed in engagement with the inner surface of the movable part 32.

The forward end of the holding pawl member 90 is formed with a drive track closing surface 102 disposed, when the pawl member is in its nail holding position, transversely across the nail feeding track within the area of lateral communication between the nail feeding track and the drive track. The holding pawl member 90 also includes a nail holding surface 104 parallel with the surface 102 and spaced therefrom in a direction away from the drive track a distance less than the distance between the axes of adjacent nail shanks. In addition, the holding pawl member 90 includes a pair of cam surfaces 106 which extend across the nail feeding track in an angular direction outwardly of the pawl member and toward the nail track so as to be engaged by a leading portion of the shanks of the nails disposed within the nail feeding track.

As best shown in FIG. 4, the drive track closing surface 102 extends vertically substantially throughout the longitudinal extent of the portion of the drive track which communicates laterally with the nail feeding track. As shown, the nail holding surface 104 is of like vertical extent as well as the associated camming surfaces 106. The upper end of the holding pawl member 90 is preferably disposed at a level just below the upper leg of the feeding pawl member 60. In order to accommodate the physical presence of the lower leg of the feeding pawl member 60, a slot 108 is formed in the adjacent portion of the holding pawl member 90. Also, with reference to FIG. 4, it will be noted that both the fixed part 30 and the movable part 32 are provided with nail head camming surfaces 110 and 112 respectively disposed at the juncture between the head guiding surfaces 46 and 56 and the drive track defining surfaces 38 and 54 respectively.

Referring now more particularly to FIGS. 1-3 the magazine assembly 28 includes a bottom wall 114 which is of circular configuration in plan providing an upper nail point engaging and supporting surface of shallow frustoconical form. The central portion of the bottom wall 114 has a spindle 116 rigidly secured thereto which extends upwardly therefrom so as to engage within the core of the coiled nail package. Rigidly secured to one side peripheral edge of the bottom wall 114 is a fixed arcuate side wall 118 one end of which is bent outwardly, as indicated at 120, so that its interior surface is in alignment with the surface 44 of the fixed part 30 of the nose piece assembly. The outwardly bent portion 120 includes an upwardly facing forwardly and upwardly inclined ledge 122 which is in alignment with the lower end of the rearwardly diverging head receiving surface 46 of the fixed part 30.

The bottom wall 114, spindle 116 and arcuate side wall 118 constitute a fixed part of the magazine assembly 28. Any suitable means may be provided for fixedly attaching the fixed magazine part on the device and, as shown, such means takes the form of an arcuate mounting bracket 124 rigidly secured, as by welding or the like, to the exterior periphery of the arcuate side wall 118 and having a pair of outwardly extending attaching flanges 126 and 128 formed on the ends thereof. The flange 126 is fixedly connected with the fixed part 30 of the nose piece assembly as by engagement between the adjacent outer surface of the fixed part and the bearing 76 as best shown in FIGS. 5 and 7. The opposite attaching flange 128 is rigidly secured to the housing of the device as best shown in dotted lines in FIG. 2.

The magazine assembly 28 also includes a movable part consisting essentially of a complementary arcuate side wall 130 and a top wall 132 of generally frustoconical configuration fixedly secured along a portion of its periphery with the upper edge of the arcuate side wall 130. The fixed and movable parts of the magazine assembly are interconnected by an inclined hinge assembly 134 connected to adjacent ends of the arcuate side walls 118 and 130 so as to permit pivotal movement of the side wall 130 and top wall 132 between a closed nail containing position and an open access position wherein the side wall 130 extends upwardly and outwardly of the bottom wall 114 and side wall 118.

The free end of the side wall 130 is bent outwardly, as indicated at 136, in a manner similar to the outwardly bent end portion 120 of the side wall 118. Also as before, the outwardly bent portion 136 is provided with an upwardly inclined ledge 138 disposed in alignment with the lower edge of the head receiving surface 56 when the movable magazine part is in its closed position. The outwardly bent portion 136 includes an extension or tongue portion 140 of a lesser vertical extent adapted to engage within a shallow recess 142 formed in the interior rear end portion of the movable part 32 when the movable magazine part is in its closed position, as best shown in FIGS. 4, 5 and 7.

It will be readily apparent that access both to the nail feeding track 20 and the interior of the magazine assembly 28 is obtained when the movable parts of the nose piece and magazine assemblies are disposed in their opened position. After a coil package of nails is loaded therein the side wall 130 is first moved into its closed position and then the movable part 32 of the nose piece assembly is moved into its closed position. Due to the overlapping arrangement of the tongue portion 140 within the recess 142, a single releasable latch means may be provided for retaining both of the movable parts in their closed positions. As shown, a preferred embodiment of such a latch means includes a generally U-shaped latch element 144, the legs of which are disposed horizontally and include apertures for receiving an upper extension of the pivot pin 98. As best shown in FIG. 4, the movable nose piece part 32 is provided with an appropriate opening 146 for receiving the lower leg of the latch element 144 and the upper leg is disposed above the upper surface of the movable part 32.

As best shown in FIG. 2, the upper leg also includes a hook-like extension, indicated at 148, adapted to engage a cooperating lug 150 formed on the upper surface of the fixed part 30. The latch element 144 is resiliently biased into a latching position by any suitable means. As shown, this means takes the form of a coil spring 152 disposed within a hollow horizontally elongated boss 154 formed on the outer surface of the movable part 32. As best shown in FIGS. 1-3, the rearward end of the spring 152 extends outwardly of the hollow boss 154 and engages a tab 156 bent inwardly from the bight portion of the latch element, the tab element also serving as a stop surface limiting the biased pivotal movement of the latch element in a counterclockwise direction, as viewed in FIG. 2, by engagement with the adjacent surface of the movable part 32. It will be noted that the hook-like extension 148 includes the usual forwardly extending cam surface adapted to engage the locking lug 150 as the movable part 32 is pivoted toward its closed position. The latch element is thus automatically moved out of its latching position against the action of the spring 152 as the movable part approaches its closed position, the hook-like extension 148 moving into locked engagement with the lug 150 when the movable part reaches its fully closed position, as best shown in FIG. 2.

The principles of the present invention have been illustrated in a preferred embodiment including specific features of construction disclosed and claimed in a commonly-assigned application, Ser. No. 125,772, filed herewith, in the name of George M. Smith and entitled MECHANISM FOR CONTAINING A NAIL PACKAGE AND FEEDING SUCCESSIVE NAILS THEREFROM. These features include the particular construction of the spring assembly for independently and simultaneously effecting the movement of the actuating rod through its drive stroke and the feeding pawl into its feeding position, the construction of the nail holding pawl which serves to close the drive track and the construction of the magazine assembly. It will be understood that while the preferred embodiment of the present invention is shown and described with these features, the principles in the present invention are applicable to mechanisms which do not include these features and therefore a detailed description of the same is not believed to be necessary, since reference may be made to the aforesaid Smith application in this regard.

For present purposes the operation of the present feed mechanism will be described with the assumption that the mechanism has been properly loaded in accordance with the disclosure of the aforesaid Smith application. When the device is actuated, air under pressure is communicated with the drive cylinder to effect movement of the drive piston and the fastener driving element 14 connected therewith through its drive stroke. The air pressure which serves to drive the drive piston is likewise communicated through the portion 88 of the nose piece assembly 16 with the cylinder 70 thus simultaneously commencing the return stroke of the actuating rod 74 against the action of spring 82. During the return stroke of the actuating rod 74, the cam surfaces 68 of the feeding pawl 60 engage the leading shank surfaces of the two leading nails within the nail feeding track. The nail holding surface 104 of the holding pawl 90 in engagement with the trailing shank surface of the leading nail within the nail feeding track prevents movement of the nails within the nail feeding track in a direction away from the drive track, thus causing the feed pawl to be pivoted out of its feeding position against the action of spring 82. It is important to note that prior to the initial return stroke movement of the feeding pawl, the leading feed surface 64 thereof is positioned in the area of the juncture between the nail feeding track and the drive track and is not disposed within the drive track. With this relationship there is no possibility presented of head interference with the nail feeding pawl in the event of a lag in the initiation of the return stroke of the nail feeding pawl.

When the actuating rod 74 reaches the end of its return stroke, cam surfaces 68 will move out of engagement of the shanks of the leading nails in the nail feeding track permitting the spring 82 to effect pivotal movement of the feeding pawl back into its feeding position wherein the feeding surface 66 extends across the nail feeding track in a position to engage the trailing surface of the second nail of the fastener package.

It will be understood that during the return stroke of the actuating rod 74, the fastener driving element 14 is simultaneously moving through its drive stroke carrying with it the leading nail disposed within the drive track 18. During the initial driving movement of the leading nail, the carrier wires of the nail package tend to cause the shank of the leading nail to move into the shank portion of the nail feeding track prior to fracture. Such movement, however, is prevented by the surface 102 of the holding pawl 90 which substantially laterally closes the drive track at its position of lateral communication with the nail feeding track.

At the end of the drive stroke, the operator deactuates the device so as to effect the return stroke of the fastener driving element 14. Deactuation serves to exhaust the drive cylinder to atmosphere. The exhausting of the drive cylinder simultaneously serves to exhaust the cylinder 70 thus permitting the spring 82 to commence the feeding stroke of the actuating rod 74. The feeding pawl 60 is thus moved by the actuating rod 74 under the action of the spring 82, in a direction toward the drive track, the feeding surface 66 engaging the second nail within the nail feeding track. The engagement and movement of the second nail by the feeding pawl will effect movement of the leading nail in the nail feeding track by virtue of the carrier wires interconnecting the two nails. However, because of the presence of the fastener driving element 14 within the drive track 18, the head of the leading nail can not move within the drive track until the fastener driving element is withdrawn from the adjacent portion of the drive track. As the fastener driving element is withdrawn, the feeding movement of the feeding pawl member 60 is completed, the compressive strength of the carrier wires between the leading nail and the second nail being such as to insure movement of the leading nail fully into the drive track.

It will be noted that during the feeding movement of the pawl 60, the leading shank surfaces of the leading two nails will be moved into engagement with the cam surfaces 106 of the holding pawl 90, thus pivoting the holding pawl out of its nail holding position against the action of the spring 100. As the second nail reaches a position corresponding with a position of the leading nail fully within the drive track at the end of the feeding movement of the pawl 60, spring 100 is operable to move the holding pawl 90 back into its nail holding position wherein the surface 102 substantially laterally closes the drive track and the holding surface 104 extends across the nail feeding track in a position to engage the trailing shank surface of the leading nail within the nail feeding track.

As indicated above, the compressional strength of the carrier wires of the nail package is such as to effect movement of the leading nail into the drive track by the engagement of the feed pawl surface 66 with the next adjacent nail. It will be noted, however, that the leading surface 64 insures that the leading nail will, during each feed stroke, be positively moved into a position at least partially within the drive track wherein the entire portion of the shank is disposed therein and the trailing portion of the head extending rearwardly from the drive track. With a nail disposed in such position partially within the drive track the trailing portion of the head overlies the cam surfaces 110 and 112 so that during the drive stroke of the fastener driving element 14, these cam surfaces will serve to cam the nail fully within the drive track during the initial portion of its driving movement. This same action insures that the last nail of the nail package will be driven. With respect to the last nail it is contemplated that the nail package will be cut so that the last nails will have a full extent of carrier wires extending rearwardly therefrom. These carrier wires will be engaged by the surface 102 of the holding pawl 90 at the completion of the feed stroke, thus retaining the last nail in the position of movement partially within the drive track and preventing the last nail from falling out of the drive track in the event that the device should be moved off of the workpiece prior to firing the last nail. While it is preferred to utilize the holding pawl 90 to hold the last nail within the drive track, it will be understood that other holding means may be provided.

It thus will be seen that the objects of this invention have been fully and effectively accomplished. It will be realized, however, that the foregoing preferred specific embodiment has been shown and described for the purpose of illustrating the functional and structural principles of this invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.

Claims

I claim:

1. In a fastener driving apparatus including a fastener driving element movable through a cycle of operation including a drive stroke and a return stroke,

an improved mechanism for feeding successive fasteners from a fastener package into a position to be driven by said fastener driving element during the drive stroke thereof, the fastener package being in the form of a strip of circular headed nails interconnected in series with their shanks in spaced parallel relation,

said mechanism comprising a nose piece assembly defining an elongated drive track receiving said fastener driving element therein during the operating cycle thereof and a nail feeding track communicating laterally with said drive track,

an actuating member carried by said nose piece assembly for movement through an operating cycle including an operative stroke in a direction along the extent of said nail feeding track toward said drive track and a return stroke,

nail feeding means operatively connected with said actuating member for movement through operative and return strokes therewith and mounted for movement relative to said actuating member for resiliently biased lateral movement into a nail feeding position extending across said nail feeding track,

said nail feeding means having first surface means operable during successive operative strokes of said actuating member with said nail feeding means in said feeding position to engage successive second nails of a fastener package along the trailing shank surface thereof and to successively move the leading nails of the package into said drive track,

said nail feeding means having second surface means spaced from said first surface means in a direction inwardly of said drive track a distance less than the spacing between the axes of adjacent nail shanks for engaging the trailing shank surface of the last nail of the package during an operative stroke of said actuating member so as to move the last nail of the package into a position within the drive track wherein the shank is disposed substantially entirely within the drive track and the trailing portion of the head is disposed within the nail feeding track,

said nosepiece assembly including downwardly and forwardly inclined cam surface means disposed at the juncture between said nail feeding track and said drive track in a position to be engaged by the trailing portion of the head of a nail moved by said second surface means into said position when such nail is initially moved outwardly of said drive track during the drive stroke of said fastener driving element to thereby cam said nail fully within said drive track for substantially axial aligned subsequent movement outwardly thereof, and

nail holding means mounted on said nose piece assembly for resiliently biased movement toward a nail holding position,

said nail holding means including first surface means operable when said nail holding means is disposed in said nail holding position to be engaged by the shanks of successive nails within said nail feeding track during the feeding movement thereof so as to move said nail holding means out of said nail holding position and permit said nail holding means to be resiliently biased back into said nail holding position at the end of each successive nail feeding movement,

said nail holding means including second surface means operable when said nail holding means is disposed in said nail holding position to engage the trailing shank surfaces of successive nails in said nail feeding track during successive return strokes of said actuating member so as to prevent movement thereof in a direction away from said drive track,

said nail feeding means including second surface means operable when said nail feeding means is disposed in said nail feeding position to be engaged by the shanks of successive nails within said nail feeding track during successive return strokes of said actuating member so as to move said nail feeding means out of said feeding position and permit the same to be resiliently biased back into said nail feeding position at the end of each successive return stroke of said actuating member.

2. A mechanism as defined in claim 1 wherein said nail holding means includes third surface means spaced from said second surface means in a direction toward said drive track a distance less than the spacing between the axes of adjacent nail shanks operable when said nail holding means is disposed in said nail holding position for substantially laterally closing said drive track at the position of communication with said nail feeding track so as to prevent successive nails in said drive track from being canted into said nail feeding track during the driving movements thereof by said fastener driving element, the fastener package including parallel wires interconnecting the headed nails, the last nail of the package including wire portions extending rearwardly thereof, the third surface means of said nail holding means being operable to engage the wire portions extending rearwardly of the last nail when the latter is disposed in said position partially within said drive track and said nail holding means is disposed in said nail holding position.

3. A mechanism as defined in claim 1 wherein said actuating means comprises a piston rod having a piston on one end thereof, a cylinder carried by said nose piece assembly slidably sealingly receiving said piston operable to receive air under pressure therein to effect movement of said piston and piston rod through a stroke corresponding to the return stroke of said actuating member, and spring means operatively connected between said nose piece assembly and said piston rod for effecting movement of said piston rod and piston through a stroke corresponding with the drive stroke of said actuating member.