190,773. Reavis, W. E. Sept. 21, 1921. Book-stitching machines-In a machine for stitching book signatures comprising a set of punches and needles mounted on a reciprocating frame by the movement of which the signatures are penetrated alternately by the needles and the punches, a clamp-device is provided comprising gripping-plates engaging a thrust member and moved against frictional resistance therewith to keep up pressure of the thrust member on the signatures during the punching operation, whereas during the stitching operation a passive clamping pressure only is employed. Fingers are operated by the punching means so as to be forced between the signatures to provide additional local support during the punching operation. Series of punches 19, Fig. 32, fixed in a bar 17 and of needles 24 carried by a bar 18 are mounted in a frame 15 reciprocated by a pair of cam-wheels 25 on a main shaft 26 engaging studs 27 projecting from the frame. Locking-threads for the stitches are provided by needles 36, 37, Fig. 7, laterally reciprocated by racks 34, 35 meshing with pinions driven by means comprising a cam 45 on the shaft 26, a lever 41 actuated by the cam, a rack bar 40 and gearing associated therewith. Loop-detaining means for the cross-threads comprise pins 46 on a slide 47, Figs. 7 and 13, which are retained by a latch 50 from being pressed forward by a spring 51 the latch being released by a lug 55 rotating with 'a shaft 5<1> forming part of the actuating 233', 233, 231, 230. The signatures are clamped between a clamp-head 65, Fig. 32, and a clamptable 66 mounted on a plate 68 which is gripped between pressure plates 70, 71 to which pressure is applied by an eccentric and lever 74 and adjustable bolt 72. The plates 70, 71 are moved relatively to the plate 68 during the punching operation by a bell-crank lever 76, a roller 79 on which engages a cam 80 on the main shaft. A continuous pressure is thereby kept up on the signatures while the cam is effective. Local support for the signatures during the punching operation is provided by a series of tines formed in a head 128 and projected through openings in a frame bar 9 by bars 129 pivoted to levers 130 operated by a cam 241 through a lever 240 and link 243. Support is provided for the signatures at a distance from the back edges by an auxiliary table 66<1> hinged to the table 66 and provided with an adjustment to allow for the more rapid increase in thickness of the pile of signatures at the back gearing for the locking-thread needles. The pins are reset by a plunger 57 in the punch bar engaging the bevelled edge of the slide 47. Rollers on the racks 34, 35 carry lubricant for the punches. The threads are tensioned by an arrangement comprising a rod 245 supported by bars 244 actuated by a cam-operated lever 247, in conjunction with a set of tensions 246 which may be put out of operation by a number of fingers 251, Fig. 1, mounted on a rod 253 actuated through a lever and link from a pedal 256. A plate C supporting the clamping devices for the signatures is arranged to be swung outwardly about a fixed shaft 42 for access to the needles and when so moved the tension on the threads is removed by the movement of a rod 237 carried by bars 236 connected to the plate C by linkage edge, this adjustment comprising ribbed wedges 82, 83, Fig. 4, moved relatively to alter the level of a bar 84 engaging the signatures by the progressive endwise movement of a bar 81, by a ramp at the side of the clamp plate, as the pile of signatures increases. A knife 88 secured to the edge, of the table 66<1> co-operates with a knife 89 spring-mounted on the table 66 to cut .and clamp the threads after a book has been sewn. The clamp table is raised to normal position by chains 98, 98<1> attached to a weight 101 and passing over pulleys on the shaft 42. The stitching is staggered and to effect this the signatures are placed by the operator against a stop 126 which is moved between the stitching operations into successive positions by mechanism comprising a ratchet-wheel 104' actuated by a ratchet 105 actuated by link connections from the sliding frame and communicating step-by-step motion to a cylinder 103 having a cam groove 104 therein engaged by a pin projecting from a slide 116 which transmits endwise motion to a bar 120 carrying the stop 126 and controlled by springs 121, 128. The cam has four stages in two of which the signatures are positively moved by the movement of the stop, while, in the other two the stop moves away from the signatures which are pressed against it by the operator. A locking device for the plate C comprises arms 261, Fig. 19, projecting from the clamp head 65 having notches 262 for engagement by the flattened ends of a rod 264 rotatable by a handle 266 and linkage 267, 268 to jam the flattened rodends in the notches. A number of books may be statched in succession without severing the threads by mterpcaing between the books plates 150 of any suitable material having apertures 151 for the punches and needles. Specification 117,798 is referred to.