Patent GB-786840-A (GB)
Title: Power-operated pressing tools for riveting and the like
IPC: B21J15/18
Filed: 1956-01-30
Abstract: 786,840. Riveting. CHICAGO PNEUMATIC TOOL CO. Jan. 30, 1956 [Feb. 1, 1955], No. 2941/56. Class 83 (4). A power-operated riveting tool comprising a reciprocating wedge 23 driven by a piston 25 and having a cam surface, a working plunger 13, a shaft 19 carrying a bell-crank lever 18 for transmitting movement from wedge to plunger, a roller on the lever coacting with said cam surface to move the lever to increase the effective length of its power arm which is acted upon by the wedge, said lever having a shoulder 14 for actuating the plunger, is characterized by means for adjusting the position of the shaft 19 relative to the tool housing thereby adjusting the location of the roller relative to the cam surface for any given position of the wedge. The tool comprises a cylinder 5, an adapter 6 and a pair of yoke frames 7 carrying a detachable yoke 11 provided with a stationary die 12 in line with a rivet set 20 carried by the spring-loaded plunger 13. The spring end of the plunger contacts the shoulder 14 on the short arm of the lever 18 on the eccentrically mounted shaft 19 which is adjustable by rotating a knob 19a to shift the position of the pivot of the lever 18. The long arm of lever 18 is bifurcated to support a roller 21 which is normally slightly spaced from one of a pair of rollers 22 mounted on shafts 8. The wedge 23 enters between the rollers 21 and 22 and rotates the lever 18 to press the rivet set plunger 13 towards the die. The spring-loaded wedge is connected to a piston rod 24 which carries the piston 25 in a chamber 27 and also a piston 26 movable in a chamber 28. Valve means under the control of a hand lever 32 admits fluid pressure selectively to the back of piston 25 and constantly to the front of piston 26 and a relay valve limits the fluid pressure in the chamber 27. The continuously supplied return pressure to piston 26 is balanced during the power stroke by direction of fluid pressure from the back of piston 25 to rear of piston 26 through a passage 33 in the rod 24. A gap adjuster comprises a cam 36 on a shaft 37 rotatable by a knob 39 (Figs. 1 and 8). The cam engages with a top portion of the lever 18 and so limits the movement of the lever. In operation, during outward movement of the wedge on the power stroke the roller 21 travels on the steep cam surface 23a which rapidly advances the rivet set plunger and when the roller engages the cam surface 23b the plunger moves more slowly but with greater pressure. A stroke indicator is provided and comprises an L-shaped slide 42 supported by a button 43 for sliding movement on the underside of a guard plate 10. The downwardly extending portion of the slide engages wings 23c on the wedge. When setting the tool the operator observes where the indicator stops after a rivet is set; if the slide has not moved, the piston has probably stalled with the roller 21 on the steep cam 23a of the wedge and to correct this the operator turns the eccentric shaft 19 to move the bell-crank lever axis rearwardly towards position B (Fig. 13). If the slide has moved all the way forward the piston may have stalled by striking the cylinder head so the operator advances the axis of the bell-crank lever to position C. When adjusted, the final pressure on each set rivet will not vary from stroke to stroke. The plunger may be arranged to move transversely with respect to the piston and a yoke of the alligator type may be used. U.S.A. Specifications 2,310,625 and 2,467,020 are referred to.