Type action for a power-driven typewriter

A simplified type action for a typewriter comprising a type bar linkage having a toothed driving pawl pivotally mounted on an intermediate lever connected to a type bar through a link, and a key lever linkage including a key lever having a hooked lever pivotally mounted thereon and adapted to be engaged by a blade or tooth on a constantly rotating power or snatch roll to initiate a cycle of printing operation. The trigger lever is yieldably pivotable by the driving pawl upon its return stroke to assure the restoration of the type bar linkage to its normal position. Motion transmitting means best suited for such type action is also disclosed in which the power roll is composed of a center shaft and a toothed member rotatably mounted thereon, and an energy storing motion transmitting spring connects and is adapted to impart the motion of the former to the latter.

BACKGROUND OF THE INVENTION 
This invention relates to a type action for a power-driven typewriter and 
more particularly to a powered type action having a simplified type action 
construction. 
Various attempts have been made to devise a simplified low cost type action 
for a power-driven typewriter. A successful attempt provides a type action 
which comprises a pawl coupled by a pin and slot connection to a type bar 
sublever connected to a type bar by a link and adapted to be pulled into 
the path of a tooth on a continuously rotated snatch roll in response to 
key lever depression and driven over an interval determined by the depth 
of pawl-tooth engagement to drive the sublever for typing operation of the 
type bar. The pin and slot connection uses a single piece key lever to 
pull the pawl into engagement with the snatch roll, provides a key lever 
bypass with economized parts, and also provides initial lost motion 
between the pawl and the sublever to assure the depth of pawl-tooth 
engagement of a preset degree. This type action, however, has been found 
to be imperfect in that the minimum depth of pawl-tooth engagement may 
cause the pawl to be moved by the snatch roll within a limit defined by 
the pin and slot lost motion connection between the pawl and the sublever 
in spite that the pawl is in general inclined to become engaged deeper and 
deeper with a snatch roll tooth once it is engaged therewith. Thus, the 
type action has a disadvantage that slow or incomplete depression of a key 
lever occasionally results in a misfiring or effects no printing of a 
character. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a simplified 
type action for a power-driven typewriter which is capable of producing 
quality of printwork even through slow or incomplete depression of a key 
lever. 
According to the present invention, there is provided a type action which 
comprises a driving pawl pivotally mounted on a type bar sublever 
connected to a type bar by a link and a trigger lever pivotally mounted on 
a key lever and adapted to be engaged with the pawl to bring the same into 
engagement within the path of a tooth of a continuously rotated toothed 
power roll and driven thereby to drive the sublever and the type bar for 
typing operation. The trigger lever is urged by a spring stretched 
therefrom to the key lever so that it is yieldably pivoted by the pawl 
when it is engaged by the latter during a return stroke of the latter to 
its initial position to provide a key lever bypass. According to the 
invention, the power roll includes a continuously rotated drive shaft, a 
coaxial toothed member mounted for rotation on and relative to the drive 
shaft within a limited angle, and an energy storing motion transmitting 
spring connecting the shaft to the toothed member for accelerating the 
latter temporarily to a higher rotational speed than would otherwise be 
obtainable by the drive shaft during actuation thereby of a driving pawl 
and its associated parts. 
Other objects and advantages of the present invention will become apparent 
from the following detailed description and accompanying drawings of 
preferred embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now FIGS. 1 and 2, there is illustrated a key lever 1 fulcrumed 
about a cross bar 2 at its rear end and depressible to effect the 
initiation of a type action. The key lever 1 passes through slots 3 and 4 
in a rectangular boxlike sublever mounting bracket generally identified by 
reference numeral 5, which extends across and is suitably supported on a 
machine frame. A rearwardly extending flat resilient finger formed on a 
spring comb 6 mounted on the machine frame underlies an ear 7 formed on 
each key lever 1 to urge it counterclockwise to a normal rest position in 
which it is abutted by the upper end of the slot 4. An upwardly extending 
hooked lever 8 which may preferably be molded with a suitable plastics 
material is mounted on each key lever 1 at an intermediate portion thereof 
for pivotal motion about a pin 9 and is urged clockwise by a tension coil 
spring 10 stretched between lugs 11 and 12 formed on the key lever 1 and 
the hooked lever 8, respectively. A laterally extending lug 13 (FIG. 2) 
provided adjacent the lug 12 at the lower end of the hooked lever 8 is 
abutted by a lower edge portion of the key lever 1 to retain the hooked 
lever 8 in its initial upright position as illustrated in FIG. 1 against 
the urging of the spring 10. Adjacent the lug 13, the hooked lower 8 has a 
leg 49 extending forwardly through the slot 4 of the sublever mounting 
bracket 5 to be guided therein for pivotal motion about the pin 9. The 
hooked lever 8 is operatively associated with a type bar linkage and has 
at its upper end a forwardly extending hook 14 which normally overlies and 
is adapted to be engaged with a bent lug at the top of an upwardly 
extending finger 15 formed intermediately of a driving pawl 16 in the type 
bar linkage. 
Each driving pawl 16 is preferably molded with a suitable plastics material 
such as a polyacetal plastics, and is connected at its forward portion to 
a sublever or intermediate lever 17 by a pin 18 and passes at its rear end 
through a vertical slot 19 formed in a guide bracket 20 fixed integrally 
to an impression control bracket 34 which extends across and is suitably 
mounted on the machine frame. A spring 21 connects the control bracket 34 
to each driving pawl 16 at the finger 15 thereof to urge the driving pawl 
16 clockwise about the pin 18 to a rest initial position in which a lobe 
22 formed on the upper edge of a rear portion of the pawl 16 is abutted by 
the lower surface of the horizontal portion of the guide bracket 20. Each 
driving pawl 16 further has a downwardly extending tooth 23 formed 
thereon. The tooth 23 of each driving pawl 16 is normally held in a 
position above and out of engagement with a toothed power roll generally 
identified by reference numeral 24. The power roll 24, preferably molded 
with a suitable plastics material, has teeth or blades 25 and is connected 
by a suitable means to the output shaft of a constantly rotating drive 
motor (not shown) so that it is driven thereby to constantly rotate 
clockwise about its axis. Thus, if the driving pawl 16 is pivoted 
counterclockwise about the pin 18 to bring its tooth 23 into the circular 
path defined by the teeth 25 of the power roll 24, the tooth 23 is engaged 
by a tooth 25 of the power roll 24 and the pawl 16 is thereby moved 
forwardly together with the sublever 17. 
Each sublever 17 is pivotally mounted on a cross bar 26 located in the 
sublever mounting bracket 5 and extends through slots 27 and 28 formed 
therein which guide the sublever 17 for pivotal motion about the cross bar 
26. A connecting link 29 connects the sublever 17 at the top thereof 
articulately to a type bar 30 fulcrumed about a segment wire 31. Each type 
bar 30 is normally resting against a type bar rest 32 and is adapted to be 
driven by the sublever 17 which pivots counterclockwise about the segment 
wire 31 to bring a character type 33 thereon into contact with a platen 
(not shown) to print the character on a record medium supported on the 
platen. 
In operation, when a key lever 1 is depressed, the trigger lever 8 thereon 
causes the hook 14 at its upper end to engage with the bent lug of the 
associated driving pawl 16 to pivot it counterclockwise about the pin 18 
from its initial position thereby bringing its tooth 23 into the circular 
path defined by the teeth 25 of the power roll 24 to initiate a cycle of 
power driven operations of the type bar linkage for typing a character. 
The driving pawl 16 is then driven forwardly by the power roll 24 against 
the action of the spring 21 to pivot the sublever 17 clockwise about the 
cross bar 26, whereby the type bar 30 is pivoted through the connecting 
link 29 counterclockwise about the segment wire 31 thereby effecting 
printing of the character. During such pivotal motion of the type bar 30, 
it is first driven by means of the power roll 24 until the tooth 23 of the 
driving pawl 16 is brought out of engagement with a tooth 25 of the power 
roll 24, and then continues its pivotal motion by its own inertia. After 
impact of the character type against the platen, the spring 21 restores 
the type bar linkage including the driving pawl 16, sublever 17 and type 
bar 30 to the initial position. Upon such restoration of the driving pawl 
16, if the key lever 1 is still held depressed, the hooked lever 8 thereon 
is contacted at the front end of its hook 14 with the bent lug of the 
finger 15 of the driving pawl 16 and is pivoted thereby counterclockwise 
against the action of the spring 10, as illustrated in FIG. 2, thereby 
assuring the driving pawl 16 and the associated members to resume their 
initial positions regardless of the depressed key lever 1. 
The impression control bracket 34 is provided for controlling the 
impression of characters to be typed on a record medium carried on the 
platen. The bracket 34 is provided with adjustable control fingers 35 
corresponding to the driving pawls 16. Each control finger 35 underlies a 
rearward extension of the driving pawl 16 and is adapted to be engaged 
with the lower edge thereof to limit pivotal motion of the driving pawl 16 
thereby limiting the depth of engagement of the tooth 23 of the driving 
pawl 16 with teeth 25 of the power roll 24. The impression is thus 
controllable by adjusting the finger 35 of the control bracket 34 since 
the momentum of the type bar 30 depends on the time or the length of 
movement of the driving pawl 16 to be driven by the power roll 24 which in 
turn depends on the depth of engagement. 
In FIGS. 3 and 4, there is illustrated a modified type action according to 
which a character is repetitively typed while a modified key lever 1a is 
held depressed. The repeat key lever 1a has a reduced height in the 
cross-section adjacent the cross bar 26 when compared with the non-repeat 
key levers 1. Since there is more room in the slots 3 and 4, the repeat 
key lever 1a can be depressed rather deeper than those key levers 1 to 
effect repetitive typing of the corresponding character. Pivotally mounted 
on the key lever 1a is a modified hooked lever 8a having a lower extension 
36 which extends downwardly along the key lever 1a and has a sidewardly 
extending bent lug 37 formed at the lower end thereof. Adjacent the bent 
lug 37 of the hooked lever 8a, the key lever 1a is provided with an 
adjustable L-shaped finger 38 extending from the lower edge thereof first 
downwardly and then forwardly, defining a spacing between the lower edge 
of the key lever 1a and the finger 38 thereon. The bent lug 37 of the 
hooked lever 8a is normally located intermediate of the spacing and is 
adapted to be abutted by the finger 38 when the hooked lever 8a is pivoted 
counterclockwise about the pin 9, thus limiting the pivotal motion of the 
hooked lever 8a. The hooked lever 8a has at the top end thereof a modified 
hook 14a which normally overlies and is adapted to be engaged with the 
bent lug at the top of the finger 15 of the driving pawl 16. The hook 14a 
has a forwardly extending offset portion defining an oblique or inclined 
edge 39 and a shouldered edge 40 which also overlie the bent lug of the 
driving pawl 16. 
In operation, depression of the key lever 1a initiates a cycle of typing 
operation in a manner as described above. Upon restoration of the type bar 
linkage, if the key lever 1a is still held depressed to a first non-repeat 
position, the bent lug at the top of the finger 15 of the driving pawl 16 
is engaged with the shouldered edge 40 of the hooked lever 8a to pivot the 
same counterclockwise in a manner as described above thereby preventing 
repetitive typing of the character. If the key lever 1a is held depressed 
rather deeper to a second or repeat position, however, the bent lug of the 
driving pawl 16 is brought into engagement with the oblique edge 39 of the 
hooked lever 8a to first pivot the lever 8a counterclockwise until the 
bent lug 37 of the lever 8a is abutted by the finger 38 of the key lever 
1a as particularly illustrated in FIG. 4 and then be cammed by the oblique 
edge 39 of the hooked lever 8a whereby the driving pawl 16 is pivoted 
counterclockwise about the pin 18 to bring its tooth 23 again into the 
circular path defined by the teeth 25 of the power roll 24 as illustrated 
in FIG. 4 thereby initiating another typing operation of the character. 
Thus, the character is repetitively typed while the key lever 1a is held 
depressed. The finger 38 of the key lever 1a is thus adjusted to limit the 
counterclockwise pivotal motion of the hooked lever 8a such that the tooth 
23 of the driving pawl 16 is brought into engagement with a tooth 25 of 
the power roll 24 at the most appropriate instant during its return stroke 
to obtain the smoothest stabilized motion thereof for such repetitive 
typing operations of the character. 
In FIGS. 5 and 6, there is illustrated another embodiment of a repeat type 
action according to the present invention. The type action comprises 
another modified key lever 1b which also has a reduced height adjacent the 
cross bar 26 as the aforementioned repeat key lever 1a has. The key lever 
1b additionally has an adjustable arm 90 provided at the intermediate 
portion thereof adjacent the pivot 9 for a modified trigger lever 8b. The 
arm 90 of the key lever 1b extends first upwardly and substantially in 
parallel with the trigger lever 8b and then obliquely in an upward and 
forward direction to define a cam surface 91 at its forward edge. A 
modified driving pawl 16b pivotally mounted on a sublever 17 has a 
laterally extending lug or cam follower 92 formed integrally thereon in 
spaced relation to the cam surface 91 of the trigger lever 8b in its 
normal position of rest. The trigger lever 8b has a modified elongated leg 
49b which extends obliquely in a downward and forward direction through 
the slot 4 of the sublever mounting bracket 5 instead of the forwardly 
extending leg 49 for any other non-repeat key lever 1. When the key lever 
1b is depressed to the deeper second position for repetitive typing, the 
leg 49b is abutted to the lower end of the slot 4 in the bracket 5 to 
yieldably pivot the trigger lever 8b counterclockwise about the pin 9 to a 
pivoted position, as illustrated in FIG. 6, whereby the driving pawl 16b 
is kept cleared of the trigger lever 8b during depression of the key lever 
1b to the second position for repetitive typing. 
In operation, depression of the key lever 1b initiates a cycle of typing 
operation in a manner as described above. Upon restoration of the type bar 
linkage, if the key lever 1b is still held depressed to the first 
non-repeat position, the trigger lever 8b is yieldably pivoted by the 
driving pawl 16b to prevent repetitive typing of the character in a 
similar manner as in the non-repeat key levers 1. If the key lever 1b is 
held depressed to the second repeat position, however, the cam follower 
lug 92 on the driving pawl 16b is brought into engagement with the cam 
surface 91 on the arm 90 of the key lever 1b to be cammed thereby to bring 
the tooth 23 of the driving pawl 16b again into the circular path defined 
by a tooth 25 of the power roll 24 as illustrated in FIG. 6 thereby 
initiating another cycle of typing operation of the character. Thus, the 
character is repetitively typed while the key lever 1b is held depressed 
to the second repeat position. The arm 90 of the key lever 1b may be 
adjusted in a similar sense as in the finger 38 of the aforementioned key 
lever 1a. 
In FIGS. 7 to 10, there is illustrated a motion transmitting mechanism for 
imparting power to drive such type bar linkages as described above, which 
will now be described in detail with reference to FIGS. 7 to 10. 
The power roll 24 comprises a center shaft 41 and a toothed member 42 which 
is mounted for rotation on and relative to the shaft 41 and consists of a 
plurality of similarly shaped toothed sections 43 preferably molded with a 
suitable plastics material such as polyacetal plastics. Each section 43 
has six teeth or blades 44 formed thereon and a hexagonal extension 45 
provided at one end thereof. This extension 45 is received in a hexagonal 
bore 46 provided at the other end of the adjacent section for affixedly 
attaching one to another section 43 as seen from FIG. 8. Each section 43 
is further provided with a small bore 47 adjacent to the extension 45 for 
receiving the shaft 41 and also with a larger bore 48 adjacent to the bore 
47. 
The shaft 41 is supported for rotation at either end portion thereof by a 
bearing member 50 attached to a side wall 51 of a machine frame by means 
of a conventional snap ring 52. The shaft 41 extends outwardly beyond the 
side wall 51 at one end thereof and a hub member 53 is fastened to this 
end of the shaft 51 by a set screw for rotation with the shaft 51. Affixed 
to the hub member 53 is a pulley 54 which is connected through a suitable 
belt (not shown) with another pulley affixed to the output shaft of a 
drive motor. The power roll 24 is thus continuously rotated. A case shift 
cam 55 is mounted for rotation on and relative to the hub member 53 and is 
adapted to be coupled thereto by means of a conventional spring clutch 
comprising a wrap clutch spring 56 which is connected to the case shift 
cam 55 at one end and to a timing wheel 57 at the other end. The wheel 57 
is loosely mounted on the hub member 53 and has a lug 58 which is normally 
engaged with a bifurcated clutch trigger (not shown) and is adapted to be 
released therefrom in response to depression or release of a case shift 
key (not shown) provided on the typewriter keyboard to couple the case 
shift cam 55 to the hub member 53 and accordingly to the driving shaft 41 
to permit the cam 55 to be rotated a half revolution thereby effecting a 
case shifting operation. 
Motion transmitting means is provided on the shaft 41 between one bearing 
member 50 and the toothed member 42. It comprises a driving member or 
first hub member generally identified by reference numeral 60, preferably 
molded with a suitable plastics material. The hub member 60 is provided 
with a center bore 61 for receiving the shaft 41 and is affixed thereto by 
means of a diametrically extending pin 62 for rotation therewith. The hub 
member 60 has a first knurled sleeve section 63 for operating a knurled 
cam member (not shown) in response to depression of a space key (not 
shown) also provided on the keyboard to activate the spacing mechanism of 
the typewriter to effect feeding of the paper carriage one letter space 
along the writing line. The hub member 60 has a second sleeve section 64 
and a flange portion 65 between the first and second sleeve sections 63 
and 64. Axially extending major and minor annular ribs 66 and 67 (FIG. 9) 
are provided on the flange portion 65 of the hub member 60, thus defining 
therebetween a slot 68 and an angular or sectoral spacing 69. 
A driven member or second hub member generally identified by reference 
numeral 70 is provided between the first hub member 60 and the toothed 
member 42. The second hub member 70, also preferably molded with a 
suitable plastics material, is provided with first and second center bores 
71 and 72 for receiving the center shaft 41 and the second sleeve section 
64 of the first hub member 60, respectively, for rotation on and relative 
to them. The second hub member 70 has a first sleeve section 73 and a 
hexagonal portion 74 which are received in the larger bore 48 and the 
hexagonal bore 46, respectively, of a toothed section 43 of the toothed 
member 42 for affixedly coupling the second hub member 70 to the toothed 
member 42. The second hub member 70 further has an integral toothed wheel 
section 75 adjacent the hexagonal portion 74 thereof. The wheel section 75 
has teeth formed thereon and is adapted to be engaged by known manually 
operable jam reset means to forcibly rotate the power roll 24 in the 
reverse direction for freeing jams of typewriter parts such as type bar 
linkages when the machine is caused to stop by such jams. The second hub 
member 70 is further provided with a second sleeve section 76 adjacent the 
wheel section 75 and a lug 77 which extends in parallel with the axis of 
the center bore 71 thereof into the angular spacing 69 of the first hub 
member 60. The second sleeve section 76 has a slot 78 formed therein at a 
position diametrically opposite to the lug 77 and is provided with a 
center bore 79 having a similar inner diameter with the ribs 66 and 67 of 
the first hub member 60 as best seen from FIG. 8. 
A motion transmitting wrap spring generally identified by reference numeral 
80 is provided for coupling the first hub member 60 to the second hub 
member 70 thereby coupling the driving shaft 41 to the toothed member 42. 
The wrap spring 80 is located in an annular spacing defined by the annular 
ribs 66 and 67 of the first hub member 60 and the second sleeve section 76 
of the second hub member 70, and has several windings which loosely 
surround the second sleeve section 64 of the first hub member 60, as seen 
from FIG. 8. The wrap spring 80 has tabs 81 and 82 at its ends which 
extend radially to be received within the slots 68 and 78 in the first and 
second hub members 60 and 70, respectively, and is so arranged that it 
urges the second hub member 70 to a normal position relative to the first 
hub member 60 in which position the lug 77 of the second hub member 70 is 
abutted against the major rib 66 of the first hub member 60. Thus, the 
toothed member 42 is normally retained in a predetermined angular position 
relative to the driving shaft 41 by means of the wrap spring 80, but is 
angularly displaceable against the urging of the wrap spring 80 to a 
position relative to the driving shaft 41 in which position the lug 77 of 
the second hub member 70 is abutted against the minor rib 67 of the first 
hub member 60. 
In operation, the toothed member 42 is rotated with normal angular relation 
to the driving shaft 41 while the power roll 24 has no load applied 
thereto by any typewriter parts. But, when a key lever 1, 1a or 1b is 
depressed and the associated driving pawl 16 or 16b is brought into 
engagement with a tooth 25 of the power roll 24 to initiate the movement 
of the type bar linkage for typing its character, the toothed member 42 is 
decelerated thereby so that it is angularly displaced in the reverse 
direction to the rotation relative to the driving shaft 41 to increase the 
torsion of the spring 80 whereby energy is stored in the motion 
transmitting spring 80. As the type bar linkage is gradually accelerated 
to get a certain speed of movement, the spring 80 will release the energy 
stored therein to additionally accelerate the type bar linkage so that the 
linkage finally gets a higher speed than would otherwise be obtained 
without such energy storage during a period of time of engagement of the 
type bar linkage by the power roll 24, and the toothed member 42 is 
restored to its normal position relative to the driving shaft 41 after 
such release of the stored energy.