Cartridge Stapler With Jam Resistant Mechanism

The present invention relates generally to staplers and, more particularly, to cartridge-type staplers.

Prior arrangements for controlling a wraparound sheath for a cartridge stapler have included harness means for urging the cartridge and sheath against one another (U.S. Pat. No. 5,121,868 to Jairam) and rotatable disks in the sheath sides controlled by spring arms (U.S. Pat. No. 4,913,332 to Olesen). In another proposal the wraparound sheath or front jaw is releasably connected to side pins (U.S. Pat. No. 4,200,215).

None of these proposals have been fully satisfactory in all applications.

Broadly, the present invention comprises a manual or powered stapler with a pivotal head having an improved sheath which sheath is pivotal about an upper axle while capable of being held stationary to reduce jamming by controlling a lower sheath axle during stapling which lower sheath axle is releasable after such operation to unclear any jam which may occur.

It is a feature that the lower axle may be held in a fixed normal operating position by the cartridge and head slot wall and upon removal of the cartridge the lower axle is free to move in such slot permitting sheath rotation to unjam the stapler.

FIG. 1 is a side elevational view of a manual cartridge stapler of the present invention;

FIG. 1a is an enlarged partial side elevational view of the stapler showing cartridge engagement;

FIG. 2 is a bottom view of the stapler;

FIG. 3 is a side elevational view of the cartridge;

FIG. 4 is a partial side elevational view showing the sheath, lower cross axle, base spring and cartridge nose;

FIG. 4a is an enlarged partial view of FIG. 4 including a head slot;

FIG. 5 is a view similar to FIG. 4 with the cartridge nose removed to release the sheath; and

FIG. 6 is a view taken long line 6--6 of FIG. 2.

In the FIGS. 1 and 1a, manual stapler 10 (with hand knob removed) includes base frame 11 with feet 12a, b positioned on support surface 14. Pivotally mounted on frame 11 about base-to-head axle 29 is swingable head 17 including staple blank cartridge unit 18 having a blank staple coil housing portion 18a, nose head portion 18n and bottom surface 18b. Sheath 21, pivotal about upper sheath axis rod 21a, includes a front panel 22a and side panels 22b and c. The position of sheath 21 is determined by upper axle rod 21a and lower cross pin axle 24 having ends extending out of sheath 21's configured hole 26 in left sheath panel sides 22b and similarly configured hole in right sheath panel side 22c (not shown). Configured holes are shaped so that when cartridge 18 is installed cross axle 24 is moved downward and held in the lowest areas 26a of panel holes 26 (see also FIG. 5). This arrangement holds sheath 21 in a firm stationary and rigid position during normal stapling operations. Also shown in FIG. 1 is resilient cartridge release lever 28 pivotally mounted on base-to-head axis 29. Lever 28 has ledge 28l which engages cartridge lower ridge piece 18p to hold cartridge 18 in operating position. When handle portion 28h of lever 28 is depressed (arrow A) lever 28 flexes to allow ledge 281 to clear cartridge ridge piece 18p permitting cartridge 18 to be withdrawn.

Turning to FIGS. 2, 4 and 4a, spring 31 includes upright spring ends 32 having holes 32h which fit over head rectangular left protrusion 19a and right protrusion (not shown). Spring 31 is held in a fixed position. Spring 31 has body portion 31b and two (2) curved spring fingers 33a, 33b which bias cross pin axle 24 upwardly and when cartridge 18 is removed, raise cross pin axle 24 as permitted by the limits of configured sheath panel holes 26 (FIG. 5). Sheath upper axle rod 21a is housed firmly in a cross passageway (not shown) in head 17. When cartridge 18 is installed in stapler head 17 the cartridge bottom 18b pushes pin axle 24 down and holds it down in sheath hole areas 26a and against forward walls 20a of each head slot 17g (see FIG. 4a). As shown in FIG. 4a, area 26a has rearward curved arcuate portion 26c which has a curvature from point A to point B equal to the curvature of pin axle 24. Both curvatures are generated about radii of equal length. Axle 24 nests in and against portion 26c when cartridge 18 is installed for operation. Axle 24 simultaneously abuts forward wall 20a to provide full control of axle 24. When cartridge 18 is removed, axle 24 is free to move up and rearward into and against a curved hole area portion 26d (between points C and D). In so moving, axle 24 travels horizontally to distance d. Areas 26a are slightly larger than the cross-sectional area of cross pin axle 24 to reduce frictional engagement of axle 24 and holes 26 when cartridge 18 is removed. Thus, the forces of inserted cartridge 18 hold sheath 21 in fixed position against walls 20a providing sheath 21 control by upper and lower axles 21a, 24, respectively.

Sheath upper axle rod 21a is housed firmly in a cross passageway (not shown) in head 17. The stability of sheath 21 provides a constant space between front face 17f of head 17 and inner surface 22s of sheath front panel 22a where staple driving blade 13 reciprocates (see FIG. 4). The firm control of sheath 21 during the stapling operation reduces jamming of staples.

If a jam does occur, cartridge 18 is removed allowing spring fingers 33a, 33b of spring 31 to urge axle 24 upwardly in holes 26 and in head grooves 17g (FIG. 6). Each groove 17g has a forward wall 20a and a rearward wall 20b which walls 20a, 20b are spaced apart a distance greater than the diameter of axle 24 to reduce frictional engagement. Pin 24 is shown in its raised released position in dotted lines in FIG. 6. Sheath 21 is then capable of swinging a few degrees about fixed axle 21a in direction (arrow B of FIG. 5) to allow jammed staple s to drop down.