Patent GB-712705-A (GB)
Title: Improvements in typewriters
IPC: B41J7/02
Filed: 1951-12-04
Abstract: 712,705. Typewriters. UNDERWOOD CORPORATION. Dec. 4, 1951 [Dec. 5, 1950], No. 28428/51. Class 100 (4) A typewriter comprises a frame, a case shift body supported for movement about a horizontal transverse axis by operation of a shift key from a normal to a case shift position, an array of type carriers 40 each having uppermost and lowermost types 51, 51c and intermediate upper and lower types 51c, 51 and each provided with actuating mechanism for moving it to a printing position and mechanism for guiding it in one or another of two paths 153, 154, the carriers and mechanisms being supported on the body for case-shift movement therewith, and operating means for each actuating mechanism including two type keys 54, so that with the body in normal position operation of one key 54 moves the carrier along one path 153 to move a first type 51 to the printing position and operation of the other key 54 moves the carrier along the second path 154 to move a second type 51 to the printing position, and with the body in the case shift position operation of the keys will move the carrier along one or other of the paths to move a third or fourth type 51c to the printing position. The framework comprises spaced side plates 18 rigidly connected by cross members including a trackway 19 on which is guided a work supporting carriage 20 having end plates 21 connected by a rail 22 which engages the trackway 19. A platen 24 is rotatably carried on end plates 21 and cooperates with feed rolls 25 for feeding work sheets. Typing mechanism.-The typing mechanism supporting body 30 comprises an open frame 31 with attached end plates 33, and each plate 33 has a projecting stud 34 bearing in bushings on plates 18, to provide a case-shift axis for the body. Eleven flat carriers 40 on each side of the central plane are guided in planes convergent on a line 41 by means of slots 44 in comb 43 and slots 46, 47 in comb 45. Two normal case types and two capital types 51c are provided on two type blocks 52 on the end of each carrier 40. Each carrier 40 is guided by means of an arm 56 pivoted at 58 on the body 30, and by an arm 55 pivoted on a stud 60 which is stationary on body 30 when one key 54 is operated but is elevated when the other key is operated. The key levers 61 pivot about a common rod 62 and are urged upwardly by springs 65 to the normal position of Fig. 1. An actuator 66 parallel to and above each lever 61 is pivoted to an upright arm 67, carries a pivoted snatch pawl 68, and is urged upwardly by a spring 74, as in Fig. 1, so that the pawl is free of and above a common toothed power drive member 70 which is continuously rotated electrically. Arms 67 pivoted to a common rod 71 normally abut the member 72. A finger 81 on each lever 61 has a hooked end 82 overlying a lug 83 on the actuator and may yield upwardly and rearwardly on lever 61, being held in the normal position by a spring 84. When lever 61 is depressed the pawl 68 is lowered into engagement with the drive member 70 which imparts an initial limited pivotal movement to the pawl and then gives the pawl and actuator a forward stroke, during which the tail 85 of the actuator comes into contact with member 70, moving the actuator upwardly to free the pawl. Spring 74 returns the actuator. If the key 54 is not released, lug 83, at the end of reciprocation, contacts the hook 82 to displace finger 81 rearwardly, and when the key is released spring 84 snaps hook 82 into engagement with lug 83. Each carrier 40 is operated by a single train of driving means operable by either of two trains of connections leading from the two related actuators. The single train drive includes a pivoted lever 91 with a rolling surface 93 which is overlaid by pivoted levers 94, 95 flanking the plane of the carrier. Each lever 94, 95 has a link 101 pivotally connected thereto at points on an arc conggruent with the system of carriers 40, the lower end of each link being pivoted to a lever unit 102 at a point on a further congruent arc. Arm 103 of the unit extends from a pivot plate 104 to link 101, whi!e arm 105 is pivotally adjustable about a screw 106 on arm 103 by means of an eccentric 107 turnable on arm 103 and straddled by the forked end of arm 105. A link 108 extends between the rear end of arm 105 and a bell-crank 110 pivoted at 114 and having a face 111 for rolling contact with arm 67. To ensure that the rear ends of levers 103 will receive equal operating strokes and have equal motion, although the levers are of graded lengths, the angular motion of the levers is adjusted by variously proportioning the rolling faces 111 of bell cranks 110. The trains from levers 94, 95 are returned by springs 123. The drive also includes a toggle link 130 connected to the carrier at 57, and a toggle member 131 pivoted at 132 to link 130 and at 133 to the body 30, the normal position being shown in Fig. 1, but the toggle straightening to actuate the carrier. The toggles 130, 131 are arranged so as to exert the same pressure whichever of the four types is brought to printing position. Each lever 91 has an arm 134 connected to the member 131 by a link 135 having an integral momentum accumulator 136. Movement of each lever 95 is limited by means of a notch 140 on the lever co-operating with a pin on the body 30, and of lever 94 by a pin and slot connection 143 with a lever 142 itself limited by a pin 144 on the body. When lever 94 or 95 is operated the related actuator 66 is freed from roll 70 slightly before full limit position is reached, the stroke being completed by the momentum of the parts, including 136 which is moved with increased acceleration by lever 91 and which exerts a final straightening force on toggle 130, 131 through link 135. Actuator 66 commences its return movement before lever 94 or 95 because spring 74 is stronger than spring 123. Movement of lever 91 is arrested by contact of arm 145 with an abutment 146. Actuation of a lever 94 elevates stud 60 to actuate the lower type block 52 along path 154, by operating a mechanism comprising lever 142, link 150, and bell crank 151 having stud 60 thereon, the latter coming to rest before the carrier 40 reaches the printing position. To prevent premature return of lever 94 a nose 155 on arm 134 descends on a pin 156 on lever 94. The carrier 40 and parts 91, 130, 132 are returned by a spring 158, a toggle 160 (Fig. 8, not shown) preventing noise. The frame 31 carries in the plane of each carrier 40 a main plate 162 supporting pivots 92, 96, 133, and pivots of levers 95, 142 and providing abutment 146, a plate 163 adjustable on plate 162 providing the pivot for bell-crank 151 and a finger 164 adjustable on plate 162 bearing pivot 58. The plates 162 are adjustably secured to the frame by screws 170. All pivot points 133 lie in a radius about the axis 41 of convergence of the carriers 40 in a transverse plane 173, and preferably plane 173 slants down at the front, and axis 41 slopes rearwardly below the platen. In the normal case position an arm 181 on each side of the body rests on an eccentrically adjustable stop 182 on the side plate 18, and in the capital case position each arm 181 abuts upwardly against a stop 183. Type guide.-A type guide 187 extending upwardly from a cross piece 188 of frame 30 has an opening through which blocks 52 enter for printing contact, and confining and guiding lips 190, the opening narrowing at top and bottom to provide guide faces which engage the obliquely approaching blocks 52. Case shift.-The power mechanism for case shifting includes an eccentric 195 associated with a connecting rod 196 by means of a ring of balls 197 so that the eccentric is freely rotatable in the rod and the latter retained on the eccentric. A rocker 198 pivoted to rod 196 and to the wall 18 at 200 has adjustable abutments 201 straddling a pin 202 extending laterally from plate 33 through a hole in wall 18. The eccentric is rotatably mounted on a constantly rotating shaft 203 carrying a toothed clutch wheel 204. A clutch pawl 206 pivoted on the eccentric is normally held free of wheel 204 by a control dog 207 normally engaging an outreaching nose on the pawl. A spring 208 in the eccentric engages a tail of the pawl 206 tending to engage the latter with wheel 204. A second control dog 210, in the normal position of case shift key 205, is clear of pawl 206. The two dogs pivot at 212 on a bracket 211 and are connected by a link 213. Operation of key 205 carried on lever 209 fast on a shaft 214 causes the arm 215 on the shaft to draw a link 216 forwardly, the latter swinging dog 210 towards pawl 206. Simultaneously link 213 swings dog 207 clear of the pawl and the latter swings to couple the eccentric 195 to the wheel 204, and at the end of a half turn rod 196 will be in a rearward position (Fig. 10) and will have operated the rocker 198 to displace the body 30 to upper case position. This half turn is terminated by engagement of the pawl with the hooked end of dog 210 which swings the pawl clear of the wheel 204. When key 205 is released, dogs 207, 210 are returned by spring 217, and pawl 206 re-engages wheel 204 for a further half turn, when dog 207 engages the pawl. In this half turn rod 196 is driven forwardly and rocker 198 restores the body to normal case position. The stop faces of the dogs are formed by leaf springs 218 which yield slightly when engaged, avoiding shock. Movement of the dogs is controlled by a stop 219. To control a rebounding tendency the eccentric carries a two lobe member 223 which co-operates with a spring- pressed pawl 224. Shaft 203 may be coaxial with roll 70 and driven by the latter through speedup gearing. A spring device 226 stores energy from a previous case shift operation for use in the initial movement of the next operation. The device comprises link members 227, 228 having forked interfitting portions, the upper member 227 being pivoted at 231 to the arm 181