Patent GB-620686-A (GB)
Title: Improvements in or relating to printing telegraph receivers
IPC: H04L17/24
Filed: 1946-05-02
Abstract: 620,686. Type-printing telegraphy. CREED & CO., Ltd., and SALMON, R. D. May 2, 1946, No. 13360. [Class 40 (iii)] In a printing-telegraph receiver in which a type carriage is moved parallel to a printing platen.for character spacing by means of feeding and retaining pawls pivoted on the carriage and engaging respectively a feeding rack reciprocable by means of a cam for each signal combination received, and a fixed rack, means is provided operative on the receipt of a signal combination the response to which does not involve any movement of said carriage for moving said feeding pawl out of engagement with said feeding rack during a sufficient part of the reciprocation of the latter to prevent a character-spacing movement of the carriage whilst leaving said retaining pawl in engagement with the fixed rack. The arrangement may include two bails parallel to the racks and operated simultaneously to lift the two pawls from their racks to allow the carriage to return to its initial position at the beginning of a line. The bails may be operated separately and in succession, so that the pawls are correspondingly disengaged from the movable and fixed racks to provide back-spacing. The receiver is generally similar to that described in Specification 580,882, the type carriage being advanced by the pawl 12 actuated by the rack 14 oscillated by an arm 39 operated by a linkage 33, 36, 37 and a cam member 32, and being retained by the pawl 13 associated with the fixed rack 15. The control of functions to be performed is effected by function bars such as 52, 53 controlled by a set of selector members, such as 21, 22 separate from the selector members, for example, notched discs, for selecting a character to be printed-as described in Specification 620,682. Suppression of letter spacing. On the receipt of a code combination a vane 58 is temporarily moved to a horizontal position, as described in Specification 620,682, the vane 58 being held in a horizontal position by the selection of a function bar, such as 52, which requires suppression of the spacing action. The vane may be retained in the horizontal position by notches or projections 60. A link 66 connected to an arm 65 operated by a cam 64 rocks a lever 70 and raises the bail 72 engaging a pin 76 to lift the pawl 12 from engagement with the driving rack 14 so that its movement is not transferred to the type carriage. When normal spacing is to take place, the vane is not held in the horizontal position and the link 66 does not operate the lever 70 to raise the bail 72. Carriage return. When the function bar 53 operated by the appropriate signal moves inwardly a pivoted lever 80 rotates in a clockwise direction and through a roller 92 and lever 90 allows a projection 83 on an arm 82 to rock a lever 84 engaging a member 85 carried by the second bail 86 slidably mounted on pins. The vane 58 is retained in the horizontal position so that the pawl 12 is raised. The upward movement of the bail 86 lifts a pin 94 secured to the pawl 13 associated with the fixed retaining rack 15 and the carriage is returned to its initial position by a spring and dash-pot arrangement. Back spacing. The operation of the appropriate control bar 52 allows a pivoted lever 98, similar to the lever 80, to rotate and a lever 100 to be actuated so that the movement of an arm 101 rocks the pivoted lever 103 to engage the member 85 by which the retaining pawl 13 is lifted from the rack 15. The vane 58 is also retained in the horizontal position so that forward spacing is suppressed. The arm 101 is moved by a lever 105, which is actuated by the cam 64 half a revolution later than the actuation of the arm 65 controlling the driving pawl 12. Due to the forward movement of the rack 14, the end of the pawl 12 when lowered engages the next tooth of the rack 14 and when the retaining pawl 13 is subsequently lifted, the type-carriage and pawl 12 move backwardly with the rack 14 when it performs its rearward movement, the carriage-return spring maintaining the rack against its operating cam. Modified spacing action. The spacing arrangement may be modified so that the lines of characters are printed from right to left, the pawls 12a, 13a co-operating with reversed teeth on racks 14a, 15a, and the linkage 33, 36, 37 operated by the cam 32 being replaced by a shaft 35 and links 49, 36a, 37a, arranged so that the arm 39 actuating the rack 14a is moved in an anti-clockwise direction for the forward stroke, i.e. for normal letter spacing. The Provisional Specification describes an arrangement in which the function cam-sleeve carries a cam which actuates a lever carrying two pawl members adapted to engage the bar utilized for withdrawing the feed pawl and a pawl member for engaging the bar used for withdrawing the retaining pawl, and a second cam which actuates a lever carrying a pawl member adapted to engage the withdrawal bar associated with the retaining pawl. These pawl members are selectively held out of engagement with the withdrawal bars by levers controlled by the carriage-return and backspacing function bars. A further retaining pawl, separate from the pawl engaging the retaining rack, is operated so that during carriage-return both withdrawal bars are held in the disengage position until the carriage reaches the beginning of the line, where it operates an arm on this retaining pawl to disengage it from the withdrawal bars so that the feeding and retaining pawls are allowed to re-engage the feed and retaining racks respectively. Specifications 563,221 and 600,297 also are referred to.