Guide Anvil Including Movable Clinching Wings for Stapler

Movable anvils for assisting in the clinching of staples are old (U.S. Pat. Nos. 2,267,185 and 4,546,910); however, their construction and operation have not been satisfactory for many applications.

Broadly, the present invention comprises a stapler for driving staples in a vertical plane including a stationary anvil body positioned at an angle to the vertical plane for guiding each of the staple legs into two parallel slots in which are operated two pivotal anvil wings for pivotal movement to engage, bend, and clinch the legs in such a manner that the legs bend in adjacent vertical planes and may, therefore, bypass one another as clinched.

FIG. 1 is a top plan view of the anvil unit of the present invention positioned on an angle;

FIG. 2 is a sectional view along the line 2--2 of FIG. 1;

FIG. 2a is a side elevational view of a staple prior to driving and clinching;

FIG. 3 is a partial elevational view of the anvil unit after the anvil wings have clinched the staple;

FIG. 4 is a partial elevational view of the anvil unit before clinching;

FIG. 5 is a partial bottom view of a clinched staple showing the staple legs in parallel side-by-side planes; and

FIG. 6 is a partial elevational view of the anvil unit adjusted to commence clinching prior to the staple crown reaching the work surface.

In FIGS. 1-5, anvil unit 9 includes body 10 which has two vertical slots 11 and 11a which lie in parallel side-by-side vertical planes. Slots 11 and 11a communicate with one another along vertical plane P which is angled a few degrees, angle A, to the vertical staple driving plane P.sub.1. Perpendicular to slot 11a is staple leg guide ramp 12b having opposed sloping surfaces 12c, 12d. Thus, as staple leg 13b of staple 14 is driven downwardly by driver blade 23 (FIG. 4), leg 13b, if not perfectly aligned with slot 11a, engages guide ramp 12b guiding leg 13b into vertical slot 11a. Similarly, the other staple leg 13a is guided by ramp 12a, as necessary, into slot 11. Since anvil unit 9 is angled, staple crown 15 is not subjected to twisting or other distortion while its legs 13a, 13b are bent out of plane P.sub.1. Each leg 13a, 13b, upon penetrating workpiece 22 and being guided as described above, engages its pivotal clinching wing 15a, 15b, which wings 15a, 15b (as housed in slots 11, 11a) lie in different but parallel planes, causing legs 13a, 13b to bend as driving continues or as wings 15a, 15b are rotated or both.

Preferably, anvil unit 9 and the size of the staplers being driven are proportioned so that leg 13b comes into contact with wing 15b between wing edge 15c and slot end 17b of slot 11 and bending starts in this area to avoid leg 13b moving into slot 11 and interfering with the bending of leg 13a. If bending starts to the left of slot end 17b, leg 13b may ride off wing 15b (before it starts to bend) and enter slot 11. Similarly, points 15d and 17a define limits of a target engagement area for leg 13a for the same reasons.

Clinching wings 15a, 15b, pivotal about pivot pins 18a, 18b, are caused to move upwardly by plate 19 powered by solenoid 21. Since legs 13a, 13b are oriented by ramps 12a, 12b to be aligned with wings 15a, 15b lying in side-by-side planes, legs 13a, 13b as clinched lie in side-by-side or adjacent planes. Where the workpiece 22 is relatively thin, legs 13a, 13b pass one another (FIG. 5); however, if the workpiece 22 is thick enough legs 13a, 13b though still lying in side-by-side planes, would not pass each other.

Turning to FIG. 6, the movement of wings 15a, 15b has been controlled to start clinching of staple legs 13a, 13b prior to staple crown 16 reaching the surface of workpiece 22.