US3432019A - Automatically disabled backspace mechanism - Google Patents

Description

L. E. HARE March 11, 1969 AUTOMATICALLY DISABLED BACKSPACE MECHANISM Sheet Filed Sept. 29, 1966 pi\ Qmmmk; a I

Fly-1 INVENTOR LLOYD E. HARE ATTORNEY March 11, 1969 HARE 3,432,019

AUTOMATICALLY DISABLED BACKSPACE MECHANISM Filed Sept. 29, 1966 B Fig-2 Sheet 2 OfZ LLOYD E. HARE INVENTOR 54 77 76 BY 7 iii/ V ATTORNEY United States Patent 1 Claim ABSTRACT OF THE DISCLOSURE In a conventional carriage typewriter, a power operated backspace mechanism having a backspace pawl, is provided with an interposer responsive to movement of the carriage to a left margin position to block engagement of the backspace pawl with a carriage rack while permitting translatory movement of the pawl should a backspace key lever be depressed with the carriage so positioned.

This invention relates to a power operated backspace mechanism for typewriters or like machines; more particularly it relates to backspace mechanism disabling elements responsive to movement of the typewriter carriage to a left hand margin position to render the backspace mechanism ineffective to move the carriage as long as the carriage is located at said left hand margin position.

In a known typewriter, a backspace pawl is power driven into engagement with and translates a rack on the carriage incident to each backspacing operation. In such a mechanism the initiation of a backspace operation, when the carriage is located at a preset left margin position, jogs the carriage causing the left margin locator and a frame supported post to pound against one another as the carriage is power driven toward and drawn back from the center post incident to each backspace operation. The noise and vibration incident to this jogging is not only irritating to a typist but more importantly, harmful to the mechanism.

In accordance with the present invention there is provided mechanism effective to prevent jogging of the can riage incident to a backspace operation called after the carriage has movedto a preset or final left margin position. More particularly there is provided interposer mechanism responsive to movement of the carriage to a left margin position to block engagement of the backspace pawl with the rack while yet permitting translatory movement of the pawl should a backspace key lever be depressed with the carriage so positioned.

An object of the invention is to provide backspace mechanism disabling elements to prevent carriage movement incident to backspace operations initiated after the carriage has been moved to a left hand margin position.

Another object of the invention is in the provision of backspace mechanism disconnect elements positionable when the typewriter carriage has moved to a left hand margin limit to prevent engagement and movement of the carriage by power operated backspace mechanism.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIGURE 1 is a perspective view, looking from the rear of the typewriter, of backspace mechanism and an associated disconnect element or interposer in accordance with the invention;

FIGURE 2 is a perspective view, looking from the front of the typewriter, showing the operative relationship of the interposer with frame and carriage supported elements;

FIGURE 3 is a partial elevational view showing the inactive position of the interposer;

FIGURE 4 is a view similar to FIGURE 3 showing an intermediate inactive position of the interposer; and

FIGURE 5 is a view similar to FIGURE 3 showing the active position of the interposer.

Referring now to the drawing wherein like reference characters designate like or corresponding elements throughout the several views there is shown in FIGURE 1 a typewriter carriage supported feed rack 10 which is adapted to be moved in a letter feed direction indicated by arrow 11 by a spring motor connected to the carriage by a drawband under control of an escapement generally designated by reference numeral 12. The carriage supported feed rack 10 is adapted to be indexed in a backspace direction indicated by arrow 13 by a pawl generally designated by reference numeral 14 which when actuated moves upwardly into rack engagement and then translates to move the carriage supported feed rack 10 in the direction of arrow 13.

Actuation of the backspace pawl 14 is effected by depression of a backspaced key lever 15 whose rear end is formed with upper and lower longitudinally offset stop lugs 16 and 17. The upper and shorter lug 16 normally lies in the wrap path of the axially bent end 18 of a radially offset coil spring 21 of a conventional wrap spring clutch generally designated by reference numeral 21a to maintain the clutch disengaged. The wrap spring clutch 21a comprises a constantly rotating shaft or sleeve 19 surrounded by the coil spring 21 with the other end of the coil spring 21 secured to the output element 22 of the wrap spring clutch 21a which takes the form of a cam. A clutch cycle is effected by raising the lug 16 from the offset spring end 1'8 allowing the spring 21 to wrap and couple the shaft 19 and cam 22. The clutch will be disengaged at the end of a revolution by the upper or lower stop lug; the latter if the lever 15 is still raised after a revolution. When such is the case, upon return of the lever 15 to normal the spring end 18 will be caught by the upper lug 16 before the spring 21 can wrap. Repeat actions are effected by raising both lugs 16 and 17 from the path of end 18. i i

A cam follower arm 23, pivotally mounted to a machine frame member 24 at one end 25, is provided intermediate its ends with a depending projection 26 which rotatably supports a roller 27 adapted to roll about the cam periphery. The other end of the cam follower arm 23 is articulately connected to a vertical thrust link 28 whose upper extremity is bent over and to which is secured a threaded stud 29. The stud 29 supports a stroke or pitch adjusting nut 31 having a rounded crown and further extends through an opening of larger diameter than the stud 29, provided in a bent off part 33 of a lateral arm 34 of a pawl lift crank 35. The underside of the part 33 of pawl lift crank 35 is shaped complimentary to and resiliently held against the rounded crown of pitch adjusting nut 31 by a spring 36 trapped between a washer 32 resting on the crank arm 34 and a nut 3111. Thus the pawl lift crank 35 is articulately connected to the vertical thrust link 28 by a relatively frictionless pivot. The pawl lift crank 35 is pivotally supported on a frame supported stud 37. Also pivotally mounted on the frame supported stud 37 is a vertically extending swing arm 38 whose upper end is pivotally connected as at 39 to one end of the backspace pawl 14. As shown in FIGURE 1 the backspace pawl 14 has a depending part 41 which lies in the path of the vertically extending arm 42 of the pawl lift crank 35. The backspace pawl 14 extends leftwardly from the pivot 39 and its left end is bifurcated to provide upper and lower arms 43 and 44, respectively, laterally offset from one another to embrace a frame supported guide plate 45. The upper arm 43 is formed with a vertically extending tooth 46 adapted to engage and move the carriage feed rack as will presently appear. Both the upper and lower arms 43 and 44 are provided with pins 47 and 48 respectively, extending rearwardly. The pin 47 on the upper arm 43 extends into a substantially rectangular cutout 49 in the guide plate 45 whose right edge 51 slants upwardly and leftwardly. Normally the pawl 14 and swing arm 38 are held to the right by a return spring 52 connected to the lower pin 48 and an ear 53 on the frame supported guide plate 45 so that the upper pin 47 is located adjacent the lower right hand corner of the guide plate cutout 49.

When the clutch is cycled by depression of the backspace key lever 15, the thrust lever 28 rocks the pawl lift crank 35 counterclockwise about pivot 37 whereby its upper arm 42 engages the depending part 41 of pawl 14 to rock the pawl 14 clockwise about its pivot connection 39 to the swing arm 38 to elevate the pawl tooth 46 along the slanted edge 51 into rack engagement; the return spring 52 preventing translation of the pawl 14 (and rotation of swing arm 38) to the left until the pin 47 reaches the top of the cutout 49 which limits further elevation. The continued application of torque by the pawl lift crank 35 to the pawl 14 after the pawl tooth 46 engages the carriage supported feed rack 10 will overcome the force of spring 52 allowing the swing arm 38 to pivot about pivot 37 and pawl 14 to translate to the left and carry the carriage supported feed rack 10 in the direction of arrow 13. The hereinabove described backspace mechanism is similar in material respects to that disclosed in Patent No. 2,577,467.

As will be understood the movement of the typewriter carriage in a backspace or carriage return direction indicated by arrow 13 in FIGURES 1 and 2 is limited by a frame supported centerpost 54 located in the path of an abutment screw 55 (FIGURES 35) on a conventional margin stop generally designated by reference numeral 56 (FIGURE 2) which is positionable along a margin rack 57 supported by the carriage rearwardly of the carriage supported feed rack 10. Pivotally mounted on the centerpost 54 is a carriage return clutch knock-off paddle 58 which is rocked against the centerpost 54 when the abutment screw 55 is moved toward the centerpost 54. The margin stop 56 includes a depending catch 59 adapted when the carriage is, in the embodiment disclosed, approximately 5 spaces from its left hand margin to engage and pull in the direction of arrow 13 a U-shaped end 60 of a lever 61 whose other end 62 is pivotally mounted on a dashpot actuator slide 63 supported for lateral movement as by pins 64 extending from a machine frame supported cross rail 65 into slots 66 thereof.

A depending arm 67 of the dashpot actuator slide 63 is secured to the plunger 68 of a dashpot (not shown) which as is understood is operative to dissipate the relatively high energy potential of a fast moving carriage over the 5 space interval, thus decelerating the carriage after a relatively long carriage return run before its movement is terminated by the centerpost 54. During backspacing operations through said 5 spaces, however. the dashpot offers negligible impedance.

The movement of the dashpot actuator slide 63 is employed in accordance with the present invention to control the movement of a backspace pawl disabling lever or interposer generally designated by reference numeral 71. It is to be understood however that the dashpot actuator slide 63 is employed to control interposer 71 merely because it exists in a conventional machine and that a separate lever responsive to carrage movement through its final increments or increment of movement could be employed to so control the interposer 71.

As viewed in FIGURE 2 the interposer 71 is pivotally mounted between its ends on a frame supported pin 72. The extremity of the generally rearwardly extending arm 73 of the interposer 71 is bent back slightly forwardly whereby the bend 74 normally rests on the face of the depending part 67 of the dashpot actuator slide 63. The generally forwardly extending arm 75 has an end 76 adapted to move over and block the upward movement of the pin 48 on the lower arm 44 of the pawl 14. As shown in dotted outline in FIGURE 2 the elevated position of the pin 48 lies in the horizontal plane through which the fiat end 76 of the interposer 71 moves. A spring 77 secured to the forwardly extending arm and to the machine frame is operative to move the interposer 71 clockwise from the normal position, as viewed in FIGURES 2 and 3, as the actuator slide 63 is moved to the right by the carriage mounted margin stop 56. FIGURE 4 shows the position of the interposer with the carriage one increment from the left margin position. If a backspace operation is initiated at this position, the carriage mounted margin stop will move the actuator slide 63 further to the right and the interposer 71 will be positioned over the pin 48 when the final carriage position is reached, as shown in FIGURE 5, in which the margin stop abutment screw 55 is shown against the carriage return knock-off paddle 58. During the last backspace increment, as the interposer 71 moves toward a blocking position, the rising pin 48 will cammingly engage the left edge (FIGURE 2-5) of the end 76 thereof, to rock the interposer 71 counterclockwise, and during translation push the interposer 71 into a neutral position to thereby allow the backspace pawl 14 to engage and move the carriage supported feed rack 10' to its final position. Where the increments of movement are less than shown. the interposer 71 will be swung to a neutral position by the pin 48 several times incident to backspacing increments in advance of the final one. Whatever the pitch of the machine as the last backspace increment is completed, the interposer 71 swings over and beyond the axis of the pin 48 precluding any camming action and thereby blocking the pin 48.

Prior to the present invention, if a backspace operation were initiated at the final carriage position, the pawl 14 would engage and move the carriage causing the margin stop abutment screw 55 to drive the paddle 58 toward the centerpost 54 during the power stroke of the backspace mechanism. As this paddle movement is insulficient to permit backspacing movement over a letter feed increment, on the return stroke of the backspace mechanism the carriage would be drawn back to the FIGURE 5 position by the spring motor. Thus a single or repeat backspace in such condition would jog the carriage.

With the present invention, the initiation of a backspace operation with the interposer 71 positioned above pin 48 as shown in FIGURE 5, the pawl 14 is prevented from rising and can only translate; to the left as viewed in FIGURE 1 or to the right as viewed in FIGURES 2-5. Thus the carriage is not engaged and remains motionless.

In conventional machines there is provided a margin release mechanism to permit carriage movement beyond a preset left margain. Such margin release mechanisms are effective to rock the centerpost assembly 54 out of the path of the margin stop abutment screw 55 and to pull the lever 61 counterclockwise, thus releasing the margin stop 56 and the dashpot actuator lever 61 permitting the interposer 71 to move out from a blocking position so that backspacing of the carriage through the margin may be accomplished. The limiting or final carriage position abutmentand a dashpot actuating catch on the carriage frame will be similarly eifective at the limiting carriage position to preclude movement of the carriage by the backspacing mechanism.

The invention claimed is:

1. A backspace mechanism for a typewriter comprisa movable carriage;

a carriage supported feed rack;

a pawl;

a keylever actuated power means for driving said pawl whereby when driven said pawl will normally rock into engagement with said carriage supported feed rack and then move in a backspace direction to move said carriage supported feed rack in a backspace direction;

a carriage supported margin stop;

a frame supported centerpost cooperable with said margain stop for determining a left hand margin position for said carriage;

interposer means normally inoperable, movable to an operable position overlying a pin extending laterally from said pawl to prevent rocking movement of said pawl, so that when said pawl is driven by said keylever actuated power means said pawl will move in a backspace direction without first engaging said carriage supported feed rack;

and means responsive to movement of said carriage, for

moving said interposer means to an operable position when said carriage arrives at a left hand margin position determined by said frame supported centerpost and said margin stop, said responsive means holding said interposer means in an operable position as long as said carriage remains in a left hand margin position, thereby preventing jogging of the carriage incident to a backspace operation called while the carriage is in a left hand margin position.

References Cited UNITED STATES PATENTS 966,035 8/1910 Mercer 19791 1,873,553 8/1932 Crumrine l9791 1,955,614 4/1934 Thompson et a1. 19794 X 2,088,064 7/1937 Koca 197-91 2,577,467 12/1951 Kloski et a]. 197-91 2,728,437 12/1955 Kupper 1979l 3,217,850 11/1965 Frechette ct a1. 197-91 X ERNEST T. WRIGHT, Primary Examiner.

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