US3779359A

US3779359A - System for performing carrier return operation

Info

Publication number: US3779359A
Application number: US00191679A
Authority: US
Inventors: D Morrison; R Raesz
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1971-10-22
Filing date: 1971-10-22
Publication date: 1973-12-18
Anticipated expiration: 1990-12-18
Also published as: CH541432A; DE2251288B2; SE380207B; DE2251288A1; BR7201900D0; JPS4850813A; JPS531017B2; GB1368867A; BE789183A; FR2157329A5; AU4759772A; IT967607B; CA969498A

Abstract

A system for performing a carrier return operation in a typewriter, printer, etc., having a leadscrew controlled carrier, and controlling when the carrier is to be returned dependent upon a carrier return signal generated in conjunction with combinations of generated signals indicative of rotation and nonrotation of the leadscrew, and the leadscrew rotational position. The system is structured such that the carrier will be returned and properly positioned at the left margin or starting line upon termination of escapement, and upon signals being generated indicating that the leadscrew is in its home rotational position.

Description

United States Patent 1191 Morrison et a1.

14 1 Dec. 18,1973

SYSTEM FOR PERFORMING CARRIER RETURN OPERATION Inventors: Donald J; Morrison; Reuben Raesz,

both of Austin, Tex.

International Business Machines Corporation, Armonk, NY.

Filed: on. 22, 1971 Appl. No.2 191,679

Assignee:

us. c1 197/66, 197/19, 197/84 R, 197/90, 197/91, 197/176, 340/172.5

11m. c1 B41j 19/70 Field 61 Search 197/16, 19, 20, 65, 197/66, 67, 68, s2, s4, 84 A, 84 B, 89,90,

References Cited UNITED STATES PATENTS 10/1967 Cralle et al. 197/176 X 2/1941 Bernhard 197/84 A 12/1953 Frey et al.,.. 197/84 B 5/1959 Frey 197/84 B 9/1959 Walton et al. 197/66 7/1966 Bell 1 1. 340/203 9/1968 Perkins et a1. 340/1725 3,406,625 Chamness et al 197/90 UX 3.512,]32 5/1970 Jones et al. 197/84 R X 3,588,119 6/1971 3,647,041 3/1972 Davis et a]. 197/84 A X OTHER PUBLICATIONS IBM Technical Disclosure Bulletin, Printer with High-Speed Space Control, H. C. Tanner, Vol. 12, No. 12, May 1970, pp. 2260-2261.

Primary Examiner Ernest T. Wright, Jr. Attorney.lames l-l. Barksdale, Jr. et a1.

57 ABSTRACT A system for performing a carrier return operation in a typewriter, printer, etc., having a leadscrew controlled carrier, and controlling when the carrier is to be returned dependent upon a carrier return signal generated in conjunction with combinations of generated signals indicative of rotation and non-rotation of the leadscrew, and the leadscrew rotational position, The system is structured such that the carrier will be returned and properly positioned at the left margin of starting line upon termination of escapement, and upon signals being generated indicating that the leadscrew is in its home rotational position.

12 Claims, 5 Drawing Figures PMENTEB HEB 18 973 sum 10F 2 EMITTER HOME COMBINATION GEAR TYPEWRITER FIG. 2

SYSTEM FOR PERFORMING CARRIER RETURN OPERATION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to carrier return systems in typewriters having a leadscrew controlled carrier, and more specifically to a system for performing a carrier return operation wherein signal sequences and combinations related to carrier escapement and the leadscrew rotational position in conjunction with a carrier return signal control when the carrier is to be returned.

2. Description of the Prior Art Heretofore, much of the prior art has dealt mainly with movable carriage type typewriters with the primary concern being the return of the carriage in such a manner as to reduce shock, vibration, and resulting breakage. With the increasing popularity of carrier type typewriters having a carrier under the control of a leadscrew, attention has been given to the problem of homing the leadscrew to insure that the carrier is in engagement with the threads of the leadscrew when 'it is positioned at the starting line or left margin.

Representative of the closest known prior art is U. S. Pat. No. 3,346,088. Disclosed is a single element typewriter having a carrier and a leadscrew which must be horned or rotated to a predetermined rotational position to correctly position the carrier at the end of a carrier return operation. The homing operation involves the steps of removing escapement and holding pawls from a pin wheel, allowing the leadscrew to rotate in a direction to advance the carrier, sensing when the leadscrew has reached a home position, and re-engaging the escapement and holding pawls with the pin wheel. Sensing is by means of a sensing pawl engaging oppositely disposed and radially projecting homing lugs on a homing disc.

' In the event the leadscrew is in its home rotational position at the time a carrier return is keyed, the sensing pawl engages one of the radially projecting homing lugs andthe escapement and holding pawls are not withdrawn from the pin wheel. In this event, the leadscrew is not rotated, is already homed, and the carrier is returned.

With the system of this invention, the apparatus for performing other operations is also utilized for performing a carrier return operation. For example, the emitter wheel and associated sensor can also be used for tabular operations, for determining the measure, for determining the position of the carrier, for determining the extent of escapement, etc., while the ratchet gear and associated magnet-armature assembly can also be used for terminating character, tab, and space escapement. In essence, a carrier return operation is accomplished electronically and takes advantage of existing apparatus, thus not increasing the likelihood of mechanical failure through incorporation of additional mechanical apparatus.

BRIEF DESCRIPTION OF DRAWING FIG. I shows a typewriter carrier and means for urging the carrier in the advancing and return directions, and a leadscrew and an associated emitter wheel and ratchet gear for controlling advancement of the carrier.

FIG. 2 is a more detailed view of the emitter wheel and an associated sensing device.

FIG. 3 is a more detailed view of the ratchet gear and an associated magnet-armature assembly.

FIG. 4 is a timing diagram showing the relationship of sensed spokes on the emitter wheel and the teeth on the ratchet gear.

FIG. 5 is a block diagram depicting the apparatus for performing a carrier return operation and controlling when the carrier is to be returned.

SUMMARY OF THE INVENTION Briefly, means are provided for generating and recognizing signal combinations in conjunction with a carrier return signal for the purposes of insuring that the leadscrew controlling the carrier in a carrier type type writer has been horned prior to effecting the return of the carrier. The signal combinations are dependent upon rotation and non-rotation of the leadscrew and the leadscrew rotational position. The system is such that a carrier return signal can be generated from a keyboard or a record reader and that the return of the carrier will not take place until carrier escapement in either direction for previously keyed or read characters and functions has terminated. Upon termination of a previous character or function escapement, a carrier return signal and a home signal indicative of the home rotational position of the leadscrew will cause the carrier to return to the left margin or starting line. Since the leadscrew has been horned, when the carrier is returned to the left margin the threads on the leadscrew will be engaged and the carrier will be maintained at that position until escapement is again initiated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS or in the advancing direction, by cable 29 which follows a path around pulley 18, which is connected to cable tensioning arm 17, and over pulley 19 to windup block 20. Force applied to carrier 16 by cable 29 is supplied by mainspring 27 maintained by mounting plate 26. Since carrier 16 is driven, or impelled, to the right by mainspring 27 and cable 29, and since mounting bracket 7 carrying pivotable shoe 6 is secured to carrier 16 with pivotable shoe 6 engaging the threads of leascrew 1, carrier advancement is controlled by counterclockwise rotation of leadscrew I (as viewed from the end having ratchet gear 32) under the influence of a gear train and power means not shown. For backspace operations, rotation of leadscrew l in the reverse, or clockwise, direction is initiated by means of a backspace magnet and spring clutch assembly not shown in FIG. 1.

The return of carrier 16 to the left for a carrier return operation results in pivotable shoe 6 pivoting and ratcheting over the threads of leadscrew 1. Carrier 16 is driven to the left, or in the return direction, for a carrier return operation by cable 30 which follows a path around pulleys 14, 13 and over pulley 25 to windup block 24. Force is applied by cable 30 through

gears

22 and 23 by means of shaft 21 connected to a motor or other power means not shown, and the transmission of power through shaft 21 will also effect windup of mainspring 27.

As shown in FIG. 1, the leadscrew 1 has an emitter wheel 31 on one'end and a ratchet gear 32 on the other end. Ratchet gear 32 and teeth 2 have associated therewith a magnet-armature assembly comprising armature 3 biased by spring 4 over fulcrum member 28, and electro-magnet 5. When forward rotation of leadscrew 1 is to be stopped, electro-magnet 5 is deactivated, allowing armature 3 to contact and abut the teeth 2 on ratchet gear 32.

Emitter wheel 31 on the left end of leadscrew 1 has emitter spokes 9 and a home emitter spoke 8, and has an associated sensing device 10 containing a home sensor 126 and an emitter sensor 127 for sensing the passage therethrough of emitter spokes 9 and home emitter spoke 8, and providing signals indicative thereof. Lead wires 12 carry pulses indicating the sensing of the home emitter spoke 8 and lead wires 11 carry pulses indicating the sensing of emitter spokes 9. Lead wires 1 1 and 12 are connected to the remainder of the system as will be described with reference to FIG. 5.

Referring to FIGS. 2 and 3, emitter wheel 31 and ratchet gear 32 are shown in more detail illustrating the correspondence of home emitter spoke 8 and home lug 38 of teeth 2. Emitter wheel 31 and ratchet gear 32 are viewed from the end of leadscrew 1 having ratchet gear 32. A timing diagram is shown in FIG. 4 showing the relationship of ratchet gear 32 and signals generated upon the sensing of home emitter and emitter spokes 8 and 9 on emitter wheel 31. When home emitter spoke 8 is sensed, the home and

emitter sensors

126 and 127 both provide signals due to the structure of the home emitter spoke 8, and these two signals are combined. The combination signal will for a carrier return operation control electro-magnet 5, which upon deactivation will allow armature 3 to contact lug 37 of teeth 2 and thereafter abut surface 39 of home lug 38 of teeth 2 stopping rotation of leadscrew 1. Surface 39, lug 37, and home lug 38 have been described separately for purposes of clarity. In actual practice, as far as the actual structure of the ratchet gear 32, per se, is concerned, surface 39 is identical to surfaces 33 and lug 37 and home lug 38 are identical to lugs 34. That is, ratchet gear 32 is symmetrical with respect to its axis of rotation. The combination signal will remain up until electro-magnet 5 is again activated and rotation of leadscrew 1 is initiated. This relationship will become more readily apparent upon reading the remainder of the specification.

With the above serving as background, reference is made to FIG. 5 in conjunction with FIGS. 1-4. In FIG. 5 there is shown a printer or typewriter keyboard 41 and record reader 42, either of which serves as a source of character and function output, providing signals to the remainder of the system. Characters are defined herein to be characters and spaces, while the functions referred to herein are defined to be tab, backspace, and carrier return. Reference is made herein to both up and down signals, and the lack of reference to a signal being either up" or down" is to be taken as up." In more conventional terminology, up" and down are taken as positive and negative logical levels, respectively. Further, reference to a Not signal is to be taken as down." In any event, signal is hereinafter to be taken as an electrical or electronic signal.

Assembly 50 is made up of apparatus described above. That is, leadscrew l is shown in FIG. 1, the home and

emitter sensors

126 and 127 make up sensing device 10 shown in FIG. 1, emitter wheel 31 is shown in FIGS. 1 and 2, the forward escapement magnet is shown as electro-magnet 5 in FIG. 1, the ratchet gear 32 is shown in FIGS. 1 and 3, the armature assembly is shown in FIGS. 1 and 3 and is made up of armature 3, spring 4, and fulcrum 28, and the backspace magnet and spring clutch assembly referred to above for effecting reverse rotation of leadscrew 1 has not been shown in FIG. 1 in order to avoid confusion. The structure of this, or a similar apparatus, is well known to those skilled in the art; being comprised of a magnet, armature, gear train, and spring clutch.

The signal combinations to be considered in conjunction with a carrier return signal (CR) are a home signal (HOME) and a Not rotational signal (ROTATION or E S HOME and a rotation signal (ROTATION or ESC), ROTATION and a Not home signal (HOME), and ROTATION and HOME. The carrier return signal is generated from printer keyboard 41 upon the operator keying a carrier return or from record reader 42 reading codes on a recording media.

Not Rotation and Not Home (ESC and HOME) A carrier return signal generated upon a carrier return being keyed on printer keyboard 41 by an operator, or being read from a recording media by record reader 42, and applied along

lines

43 or 44, respectively, gated through OR gate 45, and applied along

lines

46, 128, and 97 when leadscrew 1 is not rotating and carrier 16 is not escaping (ES? applied along line 98 from inverter 122), and when leadscrew 1 is not in its home rotational position (HOME applied along line 99 from inverter will result in a signal applied along line 101 from AND gate 100. The signal applied along line 101 is to spaced encode 102 which causes space encode 102 to output a space along line 105, through OR gate 107, and along line 108 for storage in escapement register 58. Space encode 102 is structured to output a space having a three-unit escapement value count. This stored count is applied along line 56 to comparator 54 and there compared with the count of emitter pulses applied to comparator 54 along line 53 from escapement counter 52. Emitter pulses sensed upon rotation of leadscrew 1 by the emitter sensor (127 in FIG. 1) of assembly 50 are applied along a single representative line 49 (lines 11 in in FIGS. 1 and 2) to escapement counter 52. E'scapement counter 52 and escapement register 58 are resettable, and are reset along lines 1 13 and 114, respectively, each time a signal is applied along line 55 which occurs when the contents of escapement counter 52 are greater than, or equal to, the contents of escapement register 58. Leadscrew 1 will not be stopped until the count in escapement counter 52 is equal to, or exceeds, the count for a space, or a previous character or function. When leadscrew 1 is stopped, escapement counter 52 and escapement register 58 will have been reset to zero for input and accumulation of the count for the next character or function.

With a three-unit space input to the escapement register 58, comparator 54 will bring up

lines

57 and 59 when the count-in escapement counter 52 is less than the count inescapement register 58. This will set character escapement latch 63 which is reset upon termination of escapement for any previous character or function as will be described in more detail below. Upon the setting of character escapement latch 63, a signal is applied along line 64, through OR gate 66, and thence along line 67 to the forward escapement magnet in assembly 50. A pointed out above, the forward escapement magnet in assembly 50 corresponds to electromagnet 5 in FIG. 1. The signal applied along line 67 is an initiation signal and causes the forward escapement magnet in assembly 50 to be activated, disengaging armature 3 from ratchet gear 32, and initiating or allowing, rotation of leadscrew 1 and escapement of carrier 16.

When the count in escapement counter 52 exceeds, or equals, the count in escapement register 58 (B B A=3 a signal is applied along

lines

55 and 92 providing one of the inputs to NAND gate 94. NAND gate 94 derives its other input from NAND gate 91 along line 93. The sensing thereafter of a home emitter spoke (8 in FIG. 1) by the home sensor (126 in FIG. 1) in assembly 50 will cause a home signal to be applied along a single representation line 48 (line 12 in FIGS. 1 and 2). This signal is inverted by an inverter 120 and a down signal is applied along

lines

129 and 89 to NAND gate 91. With the signal for carrier return applied along

lines

46, 130 and 90 being up and with a Not reverse escapement signal applied along line 88 being up, due to a down signal appearing on line 110 having been inverted by an inverter 121, the output of NAND gate 91 along line 93 will be up. The up signals now applied along

lines

92 and 93 are inverted by NAND gate 94 and a down signal is applied along line 95 resetting character escapement latch 63. Upon character escapement latch 63 being reset, the forward escapement magnet in assembly 50 is deactivated, stopping rotation of leadscrew 1 through a signal applied along line 64, through OR gate 66, and along line 67. Thus, rotation of leadscrew l and forward escapement of carrier 16 will occur until a home signal appears on line 48. Then if the contents of escapement counter 52 are equal to, or greater than, the contents of escapement register 58, character escapement latch 63 will be reset. If however, a home signal had not appeared on line 48 by the time a B 2 A signal appeared on line 55, leadscrew 1 would continue rotating since all input conditions to NAND gate 91 would be up resulting in a down input into NAND gate 94 which would cause a positive logical level to be applied to character escapement latch 63. Character escapement latch 63 would not be reset since a down signal along line 95 is required for resetting.

When character escapement latch 63 is reset, the condition for activating carrier return and index magnets 83 is met clue to a carrier return signal applied along

lines

46, 128, 131, and 132, a ET signal resulting from a down signal along

lines

68 and 133 which is inverted by an inverter 122 and applied along line 134, and a home signal applied along

lines

48 and 135, applied along

lines

87, 86, and 85, respectively, through AND gate 109 and along line 84. With the carrier return and index magnets 83 activated, carrier 16 is caused to return through a force applied to carrier 16 by cable 30 shown in FIG. 1, and the typewriter platen (not shown) is indexed.

With leadscrew 1 being in its home rotational position when carrier 16 is returned to the left margin, pivotable shoe 6, which ratchets over the leadscrew l during a carrier return operation, will engage the threads on leadscrew 1 and maintain carrier 16 at the left margin. lf leadscrew 1 were not in its home rotational position and carrier 16 were returned, upon deactivation of carrier return and index magnets 83, carrier 16 would be displaced in the advancing direction a short distance until pivotable shoe 6 engaged the threads on leadscrew 1, and therefore, would not be positioned at the starting line or left margin. Such an event would result in an uneven left side on output, and this is to be overcome with the system of this invention.

Home and Not Rotation (HOME and 58C) The next to last paragraph above in the description of ESC and HOME is pertinent to the conditions of HOME and ESC. Again, when character escapement Not Home and Rotation (HOME and ESC) The condition, or signal combinations, of leadscrew rotation and Not home can be divided into four categories determined by the cause of rotation of leadscrew 1. If leadscrew 1 is rotating, this is because carrier 16 is escaping for a previously keyed or read character, space, tab, backspace, etc., and rotation of leadscrew 1 and escapement of carrier 16 will continue for this previously read character or function until completed, and then the carrier return signal appearing initially on line 46 will be recognized.

These four categories are as follows:

1. Repeat Carrier Return Referring to the discussion related to m and HOME, after the three-unit space has been input to escapement register 58 and rotation of leadscrew 1 has been initiated, carrier escapement latch 63 is reset as described, with carrier return and index magnets 83 being activated. At this time, the conditions EG and HOME are met and carrier 16 is returned. During the returnof carrier 16, leadscrew l is not rotating, is in its home rotational position, and the reset condition for resetting carrier escapement latch 63 is still met. A repeat carrier return signal on line 46 will effectively only result in the indexing of the printer or typewriter platen (not shown) upon carrier return and index magnets 83 being activated again.

2. Tab Operation When leadscrew 1 is rotating due to a tab function having been keyed or read, this rotation was caused by a signal appearing on

lines

46, 128, 131 and 112 causing space encode 102 to input a 3 unit space into escapement register 58 as described above in relation to ES?) and HOME.

In further describing the forward escapement magnet of assembly 50 (electro-magnet 5 in FIG. ll), it is controlled by either character escapement latch 63 or tab escapement latch 70, with the last input having control thereof through OR gate 66. That is, during tab escapement of carrier 16, a signal applied along line resetting character escapement latch 63 will not deactivate the forward escapement magnet during rotation of leadscrew 1 when escapement or rotation signals are applied along

lines

68 and 73 in conjunction with the tab function signal applied along

lines

46, and 74.

These signals are gated through AND gate 72 and applied along line 71 setting tab escapement latch 70 and causing continued activation of the forward escapement magnet of assembly 50 due to the output of tab escapement latch 70 applied along line 69, through OR gate 66 and along line 67. The signal now applied along line 67 is a continuation signal.

After carrier 16 has escaped 3 units upon rotation of leadscrew 1, a signal appears on

lines

55 and 81. Thereafter, when carrier 16 contacts a tab stop contact 123 and a signal indicative thereof is applied along line 80, and a subsequent, or coincidental, home signal appears on line. 79, a signal is gated through NAND gate 78, and inverted, by inverter 124, providing the down signal applied along line 77 for resetting tab escapement latch 70 and deactivating the forward escapement magnet of assembly 50. The CR, W, and HOME signals then applied along

lines

87, 86, and 85, respectively, are gated through AND gate 109 and along line 84 for activating carrier return and index magnets 83 for causing carrier 16 to return.

3. Characters and Spaces When rotation of leadscrew 1 is due to a character or space having been keyed or read prior to a carrier return signal being keyed or read, the count of the character or space is input along

lines

46, 128, 131, 132, and 103 to previous character and function register 104 which is resettable to zero each time rotation of leadscrew 1 is stopped. This count is applied along line 106, through OR gate 107, and along line 108 and stored in escapement register 58. The remainder of the operation is as described in the description related to F8? and HOME. That is, when character escapement latch 63 has been reset, and when leadscrew 1 is not rotating and is in its home rotational position, signals indicative thereof applied along

lines

86 and 85, respectively, will be gated through AND gate 109 when a carrier return signal appears on

lines

46, 128, 131, 132 and 87. The signal then applied along line 84 will activate carrier return and index magnets 83 for causing carrier 16 to return.

4. Backspace Operation When rotation of leadscrew 1 is the result of a backspace having been keyed or read prior to a carrier return signal being generated, a backspace signal appeared on

lines

46, 128, 131, 132 and 103 with the escapement value count thereof being accumulated in previous character and function register 104. This count was applied along line 106, through OR gate 107, and along line 108, and stored in escapement register 58. Until the count in escapement counter 52 for the number of emitter pulses appearing on line 49 was equal to, or greater than, the backspace count stored in escapement register 58, a signal appeared on

lines

57 and 60. This signal in conjunction with the backspace operation signal on line 61 caused a signal to be gated through AND gate 117 and along lines 62 136, activating the backspace magnet and spring clutch assembly of assembly 50 and causing reverse rotation of leadscrew l and reverse escapement of carrier 16. The signal applied along line 57 also appeared on line 59, setting escapement latch 63.

It is not necessary to set carrier escapement latch 63 and activate the forward escapement magnet of assembly 50 for a backspace operation since (as can be seen in FIG. 3) armature 3 will ratchet over teeth 2 when electro-magnet 5 is deactivated and leadscrew 1 is rotated in a clockwise direction. Noise is reduced, and therefore, character escapement latch 63 is set and forward escapement magnet of assembly 50 is activated.

As mentioned, with a B A signal appearing on line 60 and a backspace operation signal appearing on line 61, a signal is gated through AND gate 117 and along lines 62 and 136 to activate the backspace magnet and spring clutch assembly of assembly 50 to cause reverse, or clockwise, rotation of leadscrew 1. Thereafter, when a B 2 A signal appears on line 55, escapement counter 52 and escapement register 58 are reset to zero along lines 113 and 114, respectively, and an up signal is applied along line 92 to NAND gate 94. The other input to NAND gate 94 along line 93 is also up since the signal appearing along line 88 is down (due to the up signal appearing on line 110 having been inverted by inverter 121) at the time the NOT home signal applied I along line 89 is either up or down and the carrier return signal along line 90 is up. The resulting down signal output from NAND gate 94 is applied along line 95 for resetting carrier escapement latch 63 and deactivating the forward escapement magnet of assembly 50. As pointed out above, deactivation of the forward escapement magnet of assembly 50 does not stop reverse rotation of leadscrew 1 since armature 3 ratchets over teeth 2 on ratchet gear 32. The stopping of leadscrew 1 takes place when the signal applied along line 57 is no longer up for activating the backspace magnet and spring clutch assembly of assembly 50. The resetting of character escapement latch 63 and the deactivation of the forward escapement magnet of assembly 50 prevents forward rotation of leadscrew 1 when the backspace magnet and spring clutch assembly of assembly 50 is deactivated.

With leadscrew 1 now stopped, the signals CR, 1 18C, and W. applied along

lines

97, 98, and 99, respectively, are gated through AND gate and along line 101 to space encode 102 for initiating forward escapement and the subsequent return of the carrier 16 as described above.

A backspace latch could be included in the above system to insure the forward homing of leadscrew 1. That is, a backspace latch could be used to insure that the return of carrier 16 will only follow forward escapement. As now shown, a down signal on line 57 causing leadscrew 1 to stop reverse rotation in conjunction with a home signal would satisfy the conditions for gating a signal through AND gate 109 and along line 84, activating carrier return and index magnets 83 and causing carrier 16 to return.

Home and Rotation (HOME and ESC) lf leadscrew 1 is rotating and in its home rotational position at the time a carrier return signal appears on line 46 and a B 2 A signal appears on

lines

55 and 92, character escapement latch 63 will be reset, stopping rotation of leadscrew 1 and activating carrier return and index magnets 83 as described above. If escapement of carrier 16 and rotation of leadscrew 1 for the previous character or function have not been completed and a home signal appears on line 48, character escapement latch 63, or tab escapement latch 70 will remain set, with leadscrew l continuing to rotate until a signal appears on line 55. A home signal appearing coincident therewith, or thereafter, will cause character escapement latch 63 to be reset and carrier return and index magnets 83 to be activated. Tab escapement latch 70 will not be reset until a tab contact signal appears on line 80, and a home signal appears coincident therewith, or thereafter, on line 79.

In summary, it is the combination of signals indicative of the rotational position of leadscrew 1 and rotation and non-rotation of leadscrew l in conjunction with, or following, a carrier return signal which forms the basis for determining when the leadscrew 1 is to be horned, when the leadscrew 1 is home, and when the carrier 16 is to be returned. In all cases, escapement for a previous character or function must have terminated, rotation of leadscrew 1 must have stopped, and the leadscrew 1 must be in its home rotational position before a carrier return operation can take place.

With the above described system, when the carrier I 16 has been returned to the left margin or starting line and the carrier return and index magnets 83 have been deactivated, the leadscrew 1 will be in its home rotational position and the pivotable shoe 6 will engage the threads on the leadscrew 1 and the carrier 16 will be positioned and maintained at the left margin.

While the invention has been shown and described with reference to a particular embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention.

What is claimed is:

l. A system for performing a carrier return operation in typewriters, printers, and similar apparatuses having a leadscrew controlling a carrier, said system comprising:

a first means for generating an electronic carrier re turn signal; 1

a second means for generating electronic position signals corresponding to the rotational position of said leadscrew;

a third means for generating electronic rotation and Not-rotation signals corresponding to rotation and non-rotation of said leadscrew; and

a fourth means for causing said carrier to return upon the occurrence of an electronic Not-rotation signal and an electronic position signal being an electronic home signal corresponding to the home rotational position of said leadscrew after an electronic carrier return signal is generated.

2. Asystem according to claim 1 wherein said fourth means includes means for stopping rotation of said leadscrew upon the occurrence of an electronic home signal.

3. A system according to claim 2 wherein said fourth means includes means for continuing rotation of said leadscrew upon the occurrence of an electronic position signal not being an electrode home signal until the occurrence of an electronic position signal being an electronic home signal.

4. A system according to claim 2 wherein said fourth means includes means for initiating and continuing rotation of said leadscrew upon the occurrence of an electronic Not-rotation signal and and an electronic position signal not being an electronic home signal until the occurrence of an electronic position signal being an electronic home signal.

5. A system for performing a carrier return operation in typewriters, printers, and similar apparatuses having a leadscrew controlling a carrier, said system comprising:

means for generating an electronic carrier return signal;

means for generating electronic position signals corresponding to the rotational position of said leadscrew;

means for generating electronic rotation and Notrotation signals corresponding to rotation and nonrotation of said leadscrew;

means for generating an electronic stop signal and means for-stopping rotation of said leadscrew;

means for generating an electronic initiation signal and means for initiating rotation of said leadscrew;

means for generating an electronic continuation signal and means for continuing rotation of said leadscrew; and

means for causing said carrier to return upon the occurrence of an electronic carrier return and any of the following combinations of electronic signals:

A. a Not'rotation signal and a home signal corresponding to the home rotational position of said leadscrew;

B. a rotation signal, a home signal, and a stop signal;

C. a rotation signal, a position signal not being a home signal, a continuation signal, a home signal, and a stop signal;

D. a position signal not being a home signal, a Notrotation signal, an initiation signal, a home signal, and a stop signal.

6. A system according to claim 5 wherein said means for initiating rotation of said leadscrew includes means for inputting a space count.

7. A system according to claim 5 wherein said combinations of electronic signals occur upon forward escapement of said carrier.

g. A system according to claim 5 further including means for determining forward escapement of said carrier.

9. A system according to claim 5 further including means for continuing carrier escapement and leadscrew rotation for characters and functions input prior to generation of an electronic carrier return signal.

10. A system according to claim 6 further including means for comparing said space count with the number of said electronic position signals for determining when said carrier is to be returned.

11. A system according to claim 8 further including means for determining reverse rotation of the leadscrew.

12. A system according to claim 5 further including means for causing said leadscrew to rotate to a home rotational position for said combinations of electronic signals (C) and (D).

22 9 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,779,359 Dated December 18, 1973 Inventor) Donald J Morrison, Reuben Raesz It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 9, line 52, the word "electrode" should read -electronic-- .1 Column 10, line 23, the word "signal" should be inserted following "return".

Signed and sealed this 9th day of April 1971 (SEAL) Attest:

EDWARD MJ 'LETCHER R. o. MARSHALL DANN Attesting Officer- Commissioner of Patents

Claims

1. A system for performing a carrier return operation in typewriters, printers, and similar apparatuses having a leadscrew controlling a carrier, said system comprising: a first means for generating an electronic carrier return signal; a second means for generating electronic position signals corresponding to the rotational position of said leadscrew; a third means for generating electronic rotation and Notrotation signals corresponding to rotation and non-rotation of said leadscrew; and a fourth means for causing said carrier to return upon the occurrence of an electronic Not-rotation signal and an electronic position signal being an electronic home signal corresponding to the home rotational position of said leadscrew after an electronic carrier return signal is generated.

2. A system according to claim 1 wherein said fourth means includes means for stopping rotation of said leadscrew upon the occurrence of an electronic home signal.

5. A system for performing a carrier return operation in typewriters, printers, and similar apparatuses having a leadscrew controlling a carrier, said system comprising: means for generating an electronic carrier return signal; means for generating electronic position signals corresponding to the rotational position of said leadscrew; means for generating electronic rotation and Not-rotation signals corresponding to rotation and non-rotation of said leadscrew; means for generating an electronic stop signal and means for stopping rotation of said leadscrew; means for generating an electronic initiation signal and means for initiating rotation of said leadscrew; means for generating an electronic continuation signal and means for continuing rotation of said leadscrew; and means for causing said carrier to return upon the occurrence of an electronic carrier return and any of the following combinations of electronic signals: A. a Not-rotation signal and a home signal corresponding to the home rotational position of said leadscrew; B. a rotation signal, a home signal, and a stop signal; C. a rotation signal, a position signal not being a home signal, a continuation signal, a home signal, and a stop signal; D. a position signal not being a home signal, a Not-rotation signal, an initiation signal, a home signal, and a stop signal.

8. A system according to claim 5 further including means for determining forward escapement of said carrier.