Patent GB-587724-A (GB)
Title: Improvements relating to escapement mechanism
IPC: B41J19/32
Filed: 1945-01-09
Abstract: 587,724. Typewriters. JENNINGS, H. W. K. (Sweeney, J. L.). Jan. 9, 1945, No. 766. [Class 100 (iv)] [Also in Group XXIV] An escapement mechanism, particularly for typewriters, comprises three elements so connected together that when one of them is held against movement, movement of another of them causes movement of the third, separate devices being provided for holding two of the elements against movement, and also means for limiting the movement of the third which is constantly urged towards one of its extreme positions. As described, the device is appliedto a typewriter for effecting the letter-spacing movement of the carriage, and for adjusting the letter spacing as desired. The differential mechanism comprises a gear 62 fixed to a shaft 54, a gear 63 rotatable on the shaft and planet gears 64, 65 meshing with the gears 62, 63 and carried by a ring 68. Rotating with the gear 62 is a gear 53 meshing with a gear 52 on a shaft 47 carrying a pinion 46 engaging a rack 45 on the typewriter carriage which is urged in the printing direction by a coiled spring connected thereto by a tape as usual. The gear 63 is urged in anticlockwise direction by a coiled spring 75 and has fixed thereto an arm 69 movable between a fixed stop 76 and a stop 77 on an adjustable bar 79. Rotation of the ring 68 is normally prevented by a ball-clutch device 112, 116, and the gear 53 can be prevented from rotating by a member 95 with tapered jaws 96 to engage the correspondingly shaped periphery of the gear. With the ring locked and gear 53 free, the carriage rack 45 under the tension of its spring rotates the mechanism in the direction of the full line arrows, Fig. 8, overcoming the action of the spring 75, until the arm 69 engages the fixed stop 76. As described below, during the movement of a typebar towards the printing position, first the block 95 is moved to lock the gear 53 and just after, the ball-clutch 116 is released. The spring 75 is now able to rotate the gear 63 in anticlockwise direction until the arm 69 engages the adjustable stop 77. As the typebar moves away from the platen, the reverse operations take place, the ring 68 being locked and the gear 53 released in that order. The carriage spring can now operate to letter space the carriage and rotate the gearing until the arm 69 engages the stop 77. The bar 79 is adjusted to alter the position of the stop 77 and thus vary the letter spacing by a screw 85 moving it against the action of a spring 89. Operation of the devices is effected by the engagement of a cam surface 27 on the type-bar lever 14 with a universal ball 26 fixed to a slidable plate 28 urged towards the front of the machine by a spring and pivoted at its rear end 33 to a yoke 36 mounted at its lower end on pivots 38. Rearward movement of the plate 28 by the parts 26, 27 occurs when the type bar reaches the position 138, Fig. 6, causing rotary movement of the yoke 36 which through a ball-andsocket connection 105, operates a sliding member 97 on which the block 95 is spring- mounted, so as to cause the latter to lock the gear 53. During subsequent movement of the yoke 36, a projection 126, Fig. 3, engages a ball 129 under the conical end of a screw 131 adjustable in an arm pivoted at 121. The arm has extensions 124 encircling the balls 116 and when thus raised by the projection 126 releases the disc 68. After printing has taken place, the reverse operations occur. Instead of the gear 62, either the gear 63 or the disc 68 may be directly coupled to the carriage. Also, the arm 69 may be fixed to the disc 68 with the ball clutch operating on the gear 63. Back-spacing mechanism.-The back-spacing key is connected with a lever which hooks over a pin on the lever 69 and when operated moves the carriage back a distance equal to its last forward movement. The key is held depressed while the type key is operated,