A stapler for driving staples (12) into a sheaf of papers comprises two guide elements (17, 17', 17"; 18, 18', 18") for internal guidance of the legs (12a) of the staple (12) during the driving of the staple into the object. Each guide element (17, 17', 17"; 18, 18', 18") consists of at least two substantially identical, separate guide parts (17, 17', 17"; 18, 18', 18") successively arranged seen in the driving direction of the staple (12). Each guide part (17, 17', 17"; 18, 18', 18") is movable between a first position, in which it extends into the driving path of the staple (12) to abut against the inside of the respective leg (12a) during the driving of the staple, and a second position, in which it is removed against spring action from the driving path of the staple (12). Each of the guide parts (17, 17', 17"; 18, 18', 18") has a ramp portion (23, 23', 23", 24, 24', 24") for such cooperation with the web portion (12b) of the staple (12) that it is removed by the web portion against spring action as the driving of the staple (12) proceeds.

A stapling device has a stapler and a staple wire cassette detachably attached directly thereto, in which the leading end of the wire emerging from the staple wire cassette terminates directly in the working region of the stapler. The stapler has a base member serving as a staple-forming and holddown element, on which a driver and a sleeve are guided linearly so as to engage in telescoping fashion within one another, and are movable perpendicular to the upper side of a sheet stack. Compression springs of different spring forces, having the same working direction, engage on the base member, the driver, and the sleeve. The stapler is acted upon by a drive system which is movable in the working direction of the compression springs. The compression springs are associated with the base member, the driver, and the sleeve, and arranged in preloaded fashion thereon, in such a way that upon actuation of the stapler, a force-controlled drive occurs in an operationally correct sequence.

A stitching apparatus for manufacturing stitching wire staples, in particular annular eyelet staples, for stitching stacked sheet materials, includes a stitching head basic body having a driver for driving the stitching wire staples into the stacked sheet materials in a downward movement of the driver. A former shapes the stitching wire staples, in particular annular eyelet staples. The former is pivoted away during the downward movement of the driver. A wire clamping lever is mounted pivotably in the former. The wire clamping lever has a control element which runs on a control cam in such a way that the former is supported as a result in the upward movement of the driver, with the result that the former is pivoted-in in the upward movement to a different point than the pivoting-out of the former in the downward movement.

A stapling device has a holddown element, a staple forming member, and a staple driving means, which are guided linearly and are movable perpendicular to the upper side of a sheet stack to be stapled. A first pressure spring with a lower spring force is associated with the holddown element. A second pressure spring whose spring force is greater than that of the first pressure spring, is associated with the staple forming member. A third pressure spring is associated with the staple driving means, its spring force being greater than that of the second pressure spring. The pressure springs are arranged with identical working directions perpendicular to the upper side of the sheet stack. The first pressure spring is arranged in preloaded fashion between the holddown element and the staple forming member. The second pressure spring is arranged in preloaded fashion between the staple forming member and the staple driving means. The third pressure spring is arranged in preloaded fashion between the staple driving means and a drive head on which engages an eccentric drive which moves the stapling device in the direction of the arrow onto sheet stack, and thereby controls a force-controlled drive mechanism of the stapling device in an operationally correct sequence.

The stitching or stapling heads, which act together in a stitching zone (C) with the supports that carry printed products to be wire-stitched, have a circular orbit. The stitching heads are guided so as to maintain their more or less vertical position during their orbit. Within the stitching zone (C), each stitching head is thus approximately aligned with its respective support and is therefore in the preferred position for driving the staples into the printed products. When the stitching heads encounter the supports, they are pushed back radially inward against the resistance of compression springs. This causes a slight flattening in the orbit of the stitching heads in the stitching zone (C) and slightly prolongs the time available for the stitching heads to act together with the supports in the stitching process.