Letter space control mechanism

Claim 2

A typewriter having a frame, character-by-character printing mechanism, paper support mechanism mounted adjacent said printing mechanism and defining a printing point therebetween, means mounting at least one of said mechanisms for lateral movement relative to the other of said mechanisms to enable positioning of said printing point along a writing line, incremental securing means connected between said frame and said one mechanism for retaining said printing point at any of a plurality of fixed equally spaced locations along said writing line; feed increment measuring means operatively associated with said one mechanism for limiting displacement of said printing point along said writing line including a movable plate defining at least a first plurality of stop surfaces, selectively positionable stop means including arresting surfaces alignable with respect to said stop surfaces and normally spaced therefrom by predetermined distances, and impositive cyclic drive means for moving said first plurality of stop surfaces of said plate along at least a first path into engagement with individual arresting surfaces to measure feed increments of said one mechanism, wherein the improvement comprises: means normally positioning one of said arresting surfaces in active arresting alignment with an associated stop surface on said plate, impositive actuator means for positioning different ones of said arresting surfaces into alignment with the first path of said stop surfaces, an overriding member mounted adjacent said actuator means and having a first position for overriding said actuator means and a second position of non-interference with the operation of said actuator means, a mode control member, detent means for establishing at least two stable positions for said mode control member, and first linkage means interconnecting said mode control member and said overriding member for positioning said overriding member in one of said first and second positions when said mode control member is in a first one of said two stable positions and for positioning said overriding member in the other of said first and second positions when said mode control member is in a second one of said two stable positions.

Claim 3

A typewriter as defined in claim 1, wherein: said stop means comprises a plurality of individually positionable two-position stop members, each providing at least one of said arresting surfaces, and said stop surfaces of said movable plate comprise individual surface portionS aligned in the first path of said stop surfaces with said arresting surfaces and wherein the improvement further comprises: said actuator means comprising individual impositive two-position actuators individually connected to said stop members for displacing respective stop members between arresting and non-arresting positions.

Claim 4

A typwriter as defined in claim 2 wherein said impositive actuators comprise expansible chamber pneumatic devices.

Claim 5

A typewriter as defined in claim 1 further comprising: means supporting said movable plate for movement along a second path that is transverse to the first path, a second plurality of aligned stop surfaces formed on said movable plate and displaced from said first plurality of stop surfaces along said second path, whereby said movable plate is positionable in either a first position wherein said arresting surfaces are aligned along the first path with said first plurality of stop surfaces or in a second position wherein said arresting surfaces are aligned along the first path with said second plurality of stop surfaces, the stop surfaces of said second plurality of stop surfaces, each being individually spaced from a respective stop surface of said first plurality of stop surfaces in the direction of the first path by fixed increments that are an even multiple of the space between said locations, said detent means further providing a third stable position for said mode control member, and further linkage means interconnecting said mode control member with said movable plate for displacing said movable plate to said second position of said movable plate when said mode control member is in said third stable position.

Claim 6

A typewriter as defined in claim 4 wherein said fixed increments are all equal to the space between said locations.

Claim 7

A typewriter as defined in claim 4, wherein: said detent means provides a fourth stable position for said mode control member, and the first linkage means positions said overriding member in said first position of said overriding member and said further linkage means positions said movable plate in said second position of said movable plate when said mode control member is positioned in said fourth stable position.

Claim 8

A typewriter as defined in claim 1 wherein said incremental securing means comprises a substantially stationary rack member having teeth thereon at regular intervals along the length of said writing line, a shiftable rack member, superimposed upon said stationary rack member and movable with respect thereto from a fixed home position along a line parallel to said writing line, means urging said movable one of said mechanisms in one direction along said writing line, alternately operative rack engaging means connected with said movable one of said mechanisms and comprising first pawl means for normally engaging said stationary rack member and defining a stable position at each of said equally spaced locations, the distance between said spaced locations being a fixed unit increment that is the minimum differential spacing between all stable positions of said printing points along said writing line, and second pawl means for engaging said shiftable rack member to transmit motion of said shiftable rack member to said movable one of said mechanisms, inter-connecting means operated in timed relation with operation of said impositive cyclic drive means to provide substantially in sequence: shifting of said shiftable rack member, engagement of said second pawl means with said shiftable rack member, release of said first pawl means from said stationary rack member, restoration of said shiftable rack member to said home position, engagement of said first pawl means with said stationary rack member, and release of said second pawl means from said shiftable rack member, said second pawl means having an effective position relative to said stationary rack member that is spaced from the effective position of said first pawl means by a first clearance increment, whereby transfer of engagement of said first pawl means from said stationary rack member and said second pawl means into said shiftable rack member will displace said movable one of said mechanisms relative to said stationary rack member by said clearance increment, said predetermined spacing distances between said stop means and said arresting surfaces being measured to limit displacement of said movable one of said mechanisms to position said first pawl means adjacent one of said stable positions on said stationary rack member and spaced therefrom away from said one direction by a further clearance increment, motion direction control means operatively associated with said impositive cyclic drive means for effectively selecting either forward or reverse movement of said shiftable rack member, said first plurality of stop surfaces comprising surfaces facing the direction of the path of said stop surfaces in opposite senses for engaging said arresting surfaces to measure both forward and reverse feed, where the improvement further comprises: input control means for selecting a non-feed operation, said stop means including a selectively positionable non-feed arresting surface positioned for selective cooperation with a stop surface of said movable plate, the spacing distance between said non-feed arresting surface and said cooperating stop surface in said reverse direction being no greater than said fixed unit increment and at least equal to the sum of said clearance increment and said further clearance increment, and means responsive to selection of a non-feed operation by said input control means for operating said motion direction control means to select reverse feed motion of said shiftable rack member, and for actively positioning said non-feed arresting surface.

Claim 9

A typewriter as defined in claim 7 wherein the sum of said clearance increment and said further clearance increment is substantially equal to the spacing between adjacent ones of said spaced locations.

Claim 10

A typewriter having a frame, character-by-character printing mechanism, paper support mechanism mounted adjacent said printing mechanism and defining a printing point therebetween, means mounting at least one of said mechanisms for lateral movement relative to the other of said mechanisms to enable positioning of said printing point along a writing line, a substantially stationary rack member having teeth thereon at regular intervals along the length of said writing line, a shiftable rack member superimposed upon said stationary rack member and movable with respect thereto from a fixed home position along a line parallel to said writing line, means urging said movable one of said mechanisms in one direction along said writing line, alternately operative rack engaging means connected with said movable one of said mechanisms and comprising first pawl means for normally engaging said stationary rack member and defining a stable position at fixed unit increments along the writing line, said unit increment being the minimum differential spacing between all stable positions of said printing points along said writing line and second pawl means for engaging said shiftable rack member to transmit motion of said shiftable rack member to said movable one of said mechanisms, means for shifting said shiftable rack member by measured distances away from and back to said fixed home position, interconnecting means operated in timed relation with operation of said shifting means to provide substantially in sequence, shifting of said shiftable rack member, engagement of said second pawl means with said shiftable rack member, release of said first pawl means from said stationary rack member, restoration of said shiftable rack member to said home position, engagement of said first pawl means with said stationary rack member, and release of said second pawl means from said shiftable rack member, said second pawl means having an efFective position relative to said stationary rack member that is spaced from the effective position of said first pawl means by a first clearance increment, whereby transfer of engagement of said first pawl means from said stationary rack member and said second pawl means into said shiftable rack member will displace said movable one of said mechanisms relative to said stationary rack member by said clearance increment and said shifting means moves said shiftable rack member to position said movable one of said mechanisms so that said first pawl means is adjacent one of said stable positions on said stationary rack member and is spaced therefrom away from said one direction by a further clearance increment, motion direction control means operatively associated with said shifting means for effectively selecting either forward or reverse movement of said shiftable rack member, and wherein the improvement comprises: input control means for selecting a non-feed operation, said shifting means including a movable plate defining at least one stop surface and operatively associated with said shiftable rack member for limiting displacement of said printing point along said writing line, a selectively activatable non-feed arresting member cooperable with said stop surface, and spaced therefrom by a distance no greater than said fixed unit increment and at least equal to the sum of said clearance increment and said further clearance increment, and means responsive to selection of a non-feed operation by said input control means for operating said motion direction control means to select reverse feed motion of said shiftable rack member, and for selectively activating said non-feed arresting member.

Claim 11

A typewriter having a frame, character-by-character printing mechanism, paper support mechanism mounted adjacent said printing mechanism and defining a printing point therebetween, means mounting at least one of said mechanisms for lateral movement relative to the other of said mechanisms to enable positioning of said printing point along a writing line, a substantially stationary rack member having teeth thereon at regular intervals along the length of said writing line, a shiftable rack member superimposed upon said stationary rack member and movable with respect thereto from a fixed home position along a line parallel to said writing line, means urging said movable one of said mechanisms in one direction along said writing line, alternately operative rack engaging means connected with said movable one of said mechanisms and comprising first pawl means for normally engaging said stationary rack member and defining a stable position at fixed unit increments along the writing line, said unit increment being the minimum differential spacing between all stable positions of said printing points along said writing line and second pawl means for engaging said shiftable rack member to transmit motion of said shiftable rack member to said movable one of said mechanisms, means for shifting said shiftable rack member by measured distances away from and back to said fixed home position, interconnecting means operated in timed relation with operation of said shifting means to provide substantially in sequence, shifting of said shiftable rack member, engagement of said second pawl means with said shiftable rack member, release of said first pawl means from said stationary rack member, restoration of said shiftable rack member to said home position, engagement of said first pawl means with said stationary rack member, and release of said second pawl means from said shiftable rack member, said second pawl means having an efFective position relative to said stationary rack member that is spaced from the effective position of said first pawl means by a first clearance increment, whereby transfer of engagement of said first pawl means from said stationary rack member and said second pawl means into said shiftable rack member will displace said movable one of said mechanisms relative to said stationary rack member by said clearance increment and said shifting means moves said shiftable rack member to position said movable one of said mechanisms so that said first pawl means is adjacent one of said stable positions on said stationary rack member and is spaced therefrom away from said one direction by a further clearance increment, motion direction control means operatively associated with said shifting means for effectively selecting either forward or reverse movement of said shiftable rack member, and wherein the improvement comprises: input control means for selecting a non-feed operation, said shifting means including a movable plate defining at least one stop surface and operatively associated with said shiftable rack member for limiting displacement of said printing point along said writing line, a selectively activatable non-feed arresting member cooperable with said stop surface, and spaced therefrom by a distance no greater than said fixed unit increment and at least equal to the sum of said clearance increment and said further clearance increment, and means responsive to selection of a non-feed operation by said input control means for operating said motion direction control means to select reverse feed motion of said shiftable rack member, and for selectively activating said non-feed arresting member.

Claim 12

A typewriter as defined in claim 9 wherein the sum of said clearance increment and said further clearance increment is substantially equal to said fixed unit increment.