Patent GB-1293487-A (GB)
Title: Printers with bi-directional spacing mechanisms
Inventor: FORREST JAMES SHERWOOD
IPC: B41J23/26
Filed: 1971-05-28
Abstract: 1293487 Selective printing INTERNATIONAL BUSINESS MACHINES CORP 28 May 1971 [30 June 1970] 17809/71 Heading B6F A printer includes a carriage 11 movable for letter spacing and back-spacing by means of an elongate reciprocable member 26 and a complementary fixed elongate member 23, the carriage being couplable alternately to the members 26, 23 during a reciprocatory stroke of the member 26 so that the carriage is advanced stepwise, the direction of advance being reversible. The carriage 11 may support a print head 11 or a platen. Variable letter spacing; back-spacing.-The members 26, 23 comprises racks, the rack 26 being reciprocable by a driver 31 reciprocated from a drive shaft 12. The driver 31 includes a notch 30 which engages a lug 32 on a bellcrank 33 to urge the rack 26 longitudinally through a spring 35, a second bell-crank 36, and a pin 37. On the return stroke of the driver 31 under spring 34<SP>1</SP>, the spring 35 draws the bell crank 33 against a second pin 46 closer to the pivot point of the bell cranks 33, 36 and thereby returns the rack 26 to its home position. For back-spacing, the first stroke of the rack 26 is made in the reverse direction by shifting the head of the driver 31 so that a notch 44 engages a lug 45 on the bellcrank 36. The head of the driver is shifted by a lever 41 operated pneumatically by bellows 42. The length of the stroke of the rack 26 may be variably restricted by a stop element 38 bearing stepped surfaces 39 for co-operation with a lug 40 on the rack 26. The element 38 is pivotable about a shaft 57 when the driver 31 is displaced, the degree of pivoting permitted being governed by stop arms 60-64 selectively positioned pneumatically by bellows 76, 80, 85, and held during a cycle by a latch member 59. The element 38 may also bear stepped surfaces 49 for restricting the back-spacing motion of the rack 26 to a variable degree. The carriage 11 is coupled to the rack 26 for the outward stroke of its cycle by pawls 18-20 and to the fixed rack 23 for the return stroke of the rack 26 by pawls 15-17. Each of the pawls 18-20 has a pair of teeth (154-156, Figs. 2, 3, not shown), the teeth of the pawls being initially displaced with respect to one another over half a tooth pitch of the rack 26, so that one of the pairs of teeth will register exactly with the teeth on the rack 26, wherever the rack is positioned, when a link 143 driven by a cam 140 keyed to the shaft 12 urges the pawls 18-20 toward the rack 26. The link 143 engages a bellcrank 159 which is pivotally connected to a lever 160 having an arm (167, Fig. 4, not shown) which urges the registered pawl into engagement with the rack 26 and registers the remaining pawls therewith so that they too are urged into engagement with the rack. The pawls 15-17 are normally engaged with the rack 23 by springs 171 but are disengaged therewith during a drive stroke of the rack 26 by an arm 169 on the bellcrank 159. Carriage-release arrangements; carriage return.-A lever 190 controlled pneumatically by bellows 192 is provided to release the carriage by disengaging pawls 15-17 from the rack through an arm 193, a latch 195 being provided with an arm 194 to hold the lever 190 in retracted position. For carriage return, an actuator (not shown) for a carriage return spring (not shown) is also actuated. Tabulation.-For tabulation, the carriage is released by actuation of lever 190, and a tabulation lever 208 is actuated pneumatically by bellows 207 to disengage a tabulation pawl 199 from the rack 23 and locate a sensor (217, Fig. 5, not shown) in the path of set tabulation stops (215). The carriage is driven in the forward direction by a main spring (not shown) until the sensor (217) strikes a stop (215) whereupon the tabulation lever 208 is displaced longitudinally and disengaged from a latch 212 so that the pawl 199 is re-engaged with the rack 23 to halt the carriage. Combination type-selecting arrangements; pneumatic control.-The keys (not shown) on the printer operate interposers (107, Fig. 6, not shown) and a filter shaft (108), the interposers engaging respective combinations of bails (100- 106) in known fashion. The bails control respective slides (93-99, 109, 110) which control the flow of air from a pump (90) driven from the filter shaft to control type selecticn mechanism or function control mechanisms such as by the bellows 42, 76, 80, 85, 192, 207 associated with carriage movements.