Abstract:
A stapler in which the sheath is held in fixed operable position by a pin during operation with the sheath configured to assure such holding. Sheath opening is accomplished by action of a separate release lever which releases with ease the sheath from the pin.

Description:
BACKGROUND OF THE INVENTION 
     While numerous satisfactory arrangements for clearing jams in staplers have been proposed (U.S. Pat. Nos. 5,121,868 and 4,913,332), the present invention provides ready and open access to the jammed area. 
     SUMMARY OF THE INVENTION 
     Broadly, the present invention is a stapler having a head and sheath with the sheath pivotal about the head and held during operation by a releasable latch positioned with respect to the head to form a staple drive channel. Also pivotal on the head in close association with the sheath is a release lever which functions to facilitate operation of the latch to release the sheath for clearing jammed staples. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of the stapler of the present invention with the staple cartridge in dashed lines; 
     FIG. 2 is a side partial elevational view of the stapler head and pivotal sheath in its open position; 
     FIG. 3 is a partial sectional view of the stapler head, sheath and sheath release lever taken along line 3--3 of FIG. 1; 
     FIG. 4 is a partial elevational view of the head, sheath and sheath release lever in operating position; 
     FIG. 5 is a front elevational view of the former and driver; 
     FIG. 6 is a sectional view taken along line 6--6 of FIG. 5; and 
     FIG. 7 is an enlarged partial elevational view of a portion of FIG. 4. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the figures, stapler 10 includes frame 11, feet 12, upper frame 13 carrying anvil 13a, head 16, staple former and driver unit 17 and driver mechanism 18. Also shown are clinching wings 21a, 21b and wing driver 23. Head 16, which moves upwardly (not downwardly as is more common) during the staple driving portion of its cylindrical movement, has upper surface 16s (FIG. 3) upon which staple blank cartridge 15 is positioned during operation. Cartridge 15 engages pin axle 32 during operation to prevent axle 32 movement. 
     Turning to FIGS. 2 and 3, pivotal sheath 26 is shown pivotal about axis 27 in head 16. Sheath 26 includes front portion 28 and side portions 29, 30. Side portions 29, 30 have end walls 29w, 30w. Each side portion 29, 30 has a hook 29h, 30h forming openings 29a, 30a configured to engage and be held in operating position by pin axle 32 urged upwardly by spring 33 in a direction D in FIG. 2. Openings 29a, 30a have front slope surfaces 29s, 30s which engage pin axle 32 to actuate pin axle 32. Movement of pin axle 32 is limited by upper and lower surfaces 16a, 16b of each oval slot 16o. During normal operating conditions, sheath 26 is held spaced from head 16 to form staple transport channel 34 (FIG. 3). 
     When a staple jam occurs, sheath release lever 37 nested outside the sheath 26 is pivoted about axis 27 by grasping handle 37h. Lever 37 includes front plate 40 and two (2) side plates 41, 42. Side plates 41, 42 include internal tabs 41t, 42t which engage end walls 29w, 30w of sheath 26 to assure its rotation with lever 37. Upon initial movement of lever 37, pin 32 is caused to be cammed downwardly by cam projections 41a, 42a overcoming spring 33 so that sheath 26 is released. Sheath 26 is also at that time free to rotate about axis 27 as urged by lever tabs 41t, 42t. 
     The cam projections 41a, 42a of lever 37 have in turn front cam surfaces 41d, 42d and rear cam surfaces 41c, 42c, which are angled to make pin axle 32 depress with ease when lever 37 is pulled right in direction DD to open or reversed to close. The shallow angles of surfaces 41c, 42c and 41d, 42d ease in the depression of pin axle 32 in either direction. In contrast, the cam front slopes 29s, 30s of sheath 26 are steeper than surfaces 41c, 42c as shown in FIG. 7. Pulling on sheath 26 directly requires a larger force to overcome spring 33 and thereby depress pin axle 32. Vertical reference line V is tangent to cam slope 30s of hook 30h (shown in dashed lines) at point P where axle 32 would first engage sheath 26 if it were pulled to effect its release. Lines V and W form angle b. Line R is an extension of cam surface 42c on lever 37. Lines V and R form angle d. Since angle b is smaller than angle d, surface 30s is steeper than surface 42c. Pulling sheath 26 to an open or release position would take a larger force than the force that is applied, in the practice of this invention, to lever 37 to cam down pin axle 32 for release of sheath 26. During normal operation sheath 26 is held in place by pin axle 32 and cartridge 15 despite normal stapling forces applied to it. The steepness of cam front slopes 29s, 30s assists in holding sheath 26 during stapler operation. Once released, sheath 26 is further swung to its completely open position (FIG. 2) for channel inspection and a clearing of staples jammed therein. 
     As sheath 16 is so opened wide for clearing, the former and driver unit 17 which include former 42 and driver 43 remain connected together by rivet 46 attached to former 42. Rivet 46 rides in driver slot 47 (see FIGS. 5 and 6) to prevent separation of the former and driver unit 17. Rivet 46 holds former 42 and driver 43 together as a unit.