Patent GB-973509-A (GB)
Title: Improvements in or relating to coupling mechanisms
IPC: B41J1/60
Filed: 1962-02-26
Abstract: 973,509. Securing together rotary parts. INTERNATIONAL BUSINESS MACHINES CORPORATION. Feb. 26, 1962 [March 22, 1961], No. 7424/62. Heading F2U. [Also in Division B6] A coupling between a driving pulley 42 and a shaft 36 connected to a rotatable and tiltable single element print head 1 comprises a tooth 104 pivoted on the shaft 36 for movement from a first position in which it engages both flanks of a radial groove 100 in the pulley 42 to a second position in which at least part of the tooth remains in the groove spaced from at least one flank thereof. The print head 1, of truncated spherical form and having rows and columns of type characters 2, is rotatably mounted in a block 6 which is tiltable about horizontal pins 24 in a yoke 23 secured to a support 26. The shaft 36 is connected to the head 1 by a universal joint comprising a slotted member 39 engaging pins 38, 40 respectively secured in the shaft and head. The block 6 is tiltable through bevel gear segments 31, 11, by a tubular shaft 30 carrying a driving pulley 32. The rotate and tilt pulleys 42, 32 are respectively rotated against springs 44, 34 by actuating tapes 43, 33. The support 26 is carried by trunnions 50 on a carrier 51 slidably mounted on a shaft 52 for longitudinally positioning the print head, and is upwardly rocked for the printing operation by the co-operative action of a cam (not shown) on a sleeve 67, keyed, but slidable, on the shaft 52, and of a follower 73 which is mounted on the support 26 by a pin 75 and on the carrier by a pin and slot (not shown). The rocking of the support 26 is limited by an arm end 113 secured thereon engaging an anvil 114 secured to the carrier. The positive rocking force applied to the support 26 is terminated before the print head strikes the platen, the print head continuing its movement by inertia. The arm 113 strikes the anvil 114 just before the print head contacts the platen so as to produce a whipping action for sharp print head engagement. The coupling groove 100 is wedge shaped and is formed in a downwardly extending portion 49 of the pulley 42. The tooth 104 is also wedgeshaped and is formed on a bell-crank lever which is pivoted on a bracket 103 of a collar 102 secured on the shaft 36 and is urged anticlockwise by a spring 106 to urge the tooth 104 to engage both flanks of the coupling groove 100 so as to rigidly connect the pulley 42 to the shaft 36. The bell-crank lever is rotated clockwise by a lever 117 one end of which is acted on by a lobe 122 of a cam 121 on the sleeve 67 and which is returned against a stop 124 by a spring 123. As shown, a ring 108 secured to the support 26 has formed therein wedge-shaped detent grooves 110, one for each peripheral column of type characters on the print head, and the tooth 104 is double-wedge-shaped so that when the bell-crank lever is rotated to partly disengage it from the groove 100 it engages one of the detent grooves 110 to precisely position the shaft 36 and correct for location inaccuracy due to wear or tape stretch. In Fig. 4 (not shown) the ring of detent grooves 110 is dispensed but when the bell-crank lever is rotated clockwise the inner edge of the tooth 104 is still not completely removed from the coupling groove 100 thereby ensuring re-entry of the tooth in the coupling groove as printing takes place. Rotational location of the print head 1 is, as shown, refined, to counteract wear and play in the universal joint 39, or, in Fig. 4 (not shown), solely effected, by an arm 18 pivoted at 17 on the block 6 and urged by a spring 20 into engagement with detent teeth 19 around the lower edge of the head. Tilt location of the print head is effected by an arm 57 of a lever 55 urged by a spring 60 to engage the arm 57 with radially extending detent teeth 15 on a plate 14 secured to the block 6. The arm 57 also extends into an arcuate slot 58 in the arm 18. The lever 55 is rotated clockwise by a face cam 68 on the sleeve 67 acting through levers 64, 62. In operation, the shaft 52 makes one revolution. At the beginning of the revolution the lever 55 is rotated clockwise so that the arm 57 is disengaged from the detent teeth 15 and acts against the lower edge of the slot 58 so as to disengage the arm 18 from the detent teeth 19. During this time the lever 117 is out of contact with the cam 121 so that the tooth 104 is in firm engagement with the coupling groove 100 of the pulley 42. In this position the tapes 33 and 43 are actuated to tilt and rotate the print head, and as they are moved the member 26 is. upwardly rocked and effects engagement of the lever 117 and the cam 121. The tape movement is completed before the arm 113 reaches the anvil and at this time the lobe 122 actuates the lever 117 to move the tooth 104 out of engagement with both flanks of the coupling groove 100 and, as shown, into engagement with one of the detent grooves 110 for rotational location of the shaft 36. As the tooth 104 enters the groove 110 the face cam 68 permits upward movement of the arm 57 to engage the detent teeth 15 for tilt location, and to permit the arm 18 to engage the detent teeth 19 for rotational location of the print head. As soon as the printing operation is completed the cam 121 permits spring return of the tooth 104 into firm reengagement with the groove 100 and at the same time the face cam 68 removes the arms 57, 18 from the teeth 15, 19.