Carriage Return Energy Absorber

Abstract

A carriage return drawband load cushioning device having a carriage return drawband guide supported on a pivotally mounted bell crank, the position of which is determined by a spring adapted to yield in response to carriage load at the commencement of carriage return movement and revert to a normal condition only after the termination of carriage return movement.

Description

BACKGROUND OF THE INVENTION

This invention relates to a power operated carriage return mechanism for typewriters and the like, and more particularly to a carriage return drawband load cushioning device in a power operated carriage return mechanism adapted to minimize stress and strain in a carriage return drawband and promote smooth carriage return motion.

Carriage return mechanisms normally comprise, a carriage return drawband which is connected to a typewriter carriage through the intermediary of a line spacing mechanism, a carriage return reel for winding the carriage return drawband, a continuously rotating power driven member, a normally disabled clutch interposed between the carriage return reel and the continuously rotating power driven member, and a key controlled mechanism for actuating the clutch and thereby coupling the continuously power driven member to the carriage return reel.

As can be readily appreciated, due to the inertia of the carriage, the magnitude of the carriage load as seen by the carriage return drawband is much greater at the commencement of carriage return movement that it is after the carriage is moving. Consequently, unless means are provided to alleviate the condition, a carriage return drawband experiences shock and an inordinate amount of stress and strain at the commencement of carriage return movement which not only produces an undesirable jerking motion of the carriage but materially reduces the life expectancy of the carriage return drawband.

While carriage return mechanisms have been provided in the past with torque limiters in the form of slip clutch arrangements to avoid shock, and stress and strain in the carriage return drawband at the commencement of a carriage return movement, slip clutch arrangements customarily provided for this purpose are quite costly and normally require critical adjustments to operate in an efficient manner.

Accordingly, it is usually not practical to employ such a slip clutch arrangement in the carriage return mechanism of a portable typewriter in which it is essential to minimize cost and critical adjustments.

It is known to employ resilient couplings to cushion or absorb the impact of sudden loads, however a disadvantage in the use of such a coupling in a carriage return drawband is the inherent tendency for a resilient coupling to store energy and then return it, and, as a consequence cause an unwanted surge or increase in the return velocity of the carriage.

SUMMARY OF THE INVENTION

Briefly, the present invention provides a carriage return drawband load cushioning device in a carriage return mechanism for reducing shock and stress and strain in a carriage return drawband and promoting smooth carriage return motion. The carriage return drawband is led rearwardly from a carriage return reel around a carriage return drawband guide mounted on one arm of a pair of angularly disposed arms forming a bellcrank pivotally mounted at the vertex of the angularly disposed arms to the typewriter side frame, passes vertically upward to a pulley rotatably mounted on a stud fixed to the typewriter frame, and is then connected to a line feed mechanism mounted on a carriage. A resilient member connected between the end of the other angularly disposed arm of the bellcrank and a stud fixed to the typewriter frame is adapted to bias the bellcrank in a counterclockwise direction against a stop mounted on the typewriter frame and yield under the load of the carriage at the commencement of carriage return movement, thereby effectively decreasing the magnitude of power exerted on the carriage to commence the return movement of the carriage. The resilient member biasing the bellcrank is so positioned that as the bellcrank rotates clockwise, the moment arm through which the force of the resilient member acts and consequently the torque it exerts is adapted to decrease enabling the bellcrank to maintain its clockwise rotated position until the end of carriage return.

Accordingly, an object of the present invention is to provide a cushioning device in a carriage return mechanism for reducing shock and stress and strain in a carriage return drawband and promoting smooth carriage return motion.

Another object of the present invention is to provide a carriage return drawband load cushioning device adapted to absorb energy at the commencement of carriage return movement and retain it until the termination of carriage return movement.

Other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following description of the invention taken in conjunction with the drawing, which forms a part thereof.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a carriage return mechanism embodying the present invention;

FIG. 2 is a side view of the carriage return drawband load cushioning device of the present invention;

FIG. 3 is a sectional view of the carriage return reel and the wrap spring clutch mechanism embodied in the carriage return mechanism of the present invention;

FIG. 4 is a side view of the key control mechanism embodied in the carriage return mechanism of the present invention;

FIG. 5 is a side view of the key control mechanism illustrated in FIG. 4 shown in an operational mode;

FIG. 6 is a side view of a brake mechanism for minimizing carriage return drawband loop-out in the carriage return mechanism of the present invention, and

FIG. 7 is a side view of the brake mechanism illustrated in FIG. 6 shown in an operational mode.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Referring now to the drawing wherein like reference characters designate like or corresponding parts throughout the several views, there is illustrated in FIG. 1 a flanged carriage return reel 10 adapted to wind a carriage return drawband 11, a continuously rotating shaft 12 having, as best viewed in FIG. 3, a normally disabled wrap spring 13 connected thereto, and a key control mechanism generally identified by the reference numeral 14, adapted to enable the wrap spring 13 so as to couple the carriage return reel 10 to the continuously rotating shaft 12. The carriage return drawband 11 is guided rearwardly around a pulley 15 of a carriage return drawband load cushioning device, generally identified by the reference numeral 16, and upwardly over a sheave 17 mounted on the typewriter frame, and from there leftwardly in a bend around the underside of a sheave 18 mounted on a carriage 19 to a line spacing device (not shown).

The carriage return load cushioning device 16, most clearly shown in FIG. 2, comprises a bellcrank 21 having two angularly disposed arms 23 and 24 pivotally mounted at their vertex on a stud 22 extending outwardly from the typewriter frame. The pulley 15 is supported at the end of arm 23 while the arm 24 has an aperture 25 formed therein for receiving a hooked end of a coil spring 26. The coil spring 26 is connected at its other end to a stud 27 extending from the frame of the typewriter and is adapted to bias the bellcrank 21 counterclockwise as viewed in FIGS. 1 and 2 with the arm 23 in abutment with a stop 28 mounted on the typewriter frame between the angularly disposed arms 23 and 24. The stud 27 to which the coil spring 26 is connected is so positioned on the typewriter frame that the moment arm through which the force of the coil spring 26 acts decreases as clockwise movement of the bellcrank 21, as shown in phantom in FIG. 2, increases the tension in the coil spring 26. The stop 28 is so positioned on the typewriter frame that it abuts arm 24 of the bellcrank 21 immediately prior to the position at which the coil spring 26 would pass over the stud 22 and at which point the moment arm through which the force of the coil spring 26 acts would be zero.

As shown in FIG. 3, the carriage return reel 10 is rotatably mounted on the outer surface of a bearing member 29 rigidly supported in a typewriter side frame 31. In addition to supporting the carriage return reel 10, the bearing member 29 is also adapted to support the continuously rotating shaft 12 extending axially through the center bore 32 of the bearing member 29. Rotatably mounted on the continuously rotating shaft 12 extending axially through the center bore 32 of the bearing member 29 is a driven member 33 having lugs 34 extending therefrom into apertures 35 in the side of the carriage return reel 10 and adapted through the action of the wrap spring 13 to provide a positive rotary connection between the carriage return reel 10 and the continuously rotating shaft 12. The wrap spring 13 is adapted to telescope the driven member 33 and is secured at one end 36 by a resilient C-ring 37 to a flange or driving member 38 rigidly connected to the end of the continuously rotating shaft 12 by a threaded screw 39 engaged to the continuously rotating shaft 12. The free end 41 of the wrap spring 13 is bent outwardly into an aperture in a phenolic collar 42 encircling the periphery of the wrap spring 13 and adapted when restrained to cause the wrap spring 13 to wrap and couple the driven member 33 and the driving member 38. The carriage return reel 10 is urged clockwise by a flat coil spring 43 connected internally of the reel 10 in a conventional manner with one end connected to the bearing member 29 and the other end connected to the inner periphery of the hub 44 of the carriage return reel 10, thereby tending to maintain the carriage return drawband 11 in a taut condition.

The key control mechanism 14 for enabling the wrap spring 13 to wrap and thereby drive the carriage return reel 10, as illustrated in FIG. 1, includes a carriage return key lever 45 fulcrumed about a cross shaft 46 and depressible to effect initiation of carriage return action. The forward end of the key lever 45 passes through a slot 47 in a keyboard frame assembly generally identified by reference numeral 48, which extends across and is suitably supported on the typewriter frame. A lever 49 pivotally mounted at its forward end on a cross shaft 49a underlies a downwardly projecting edge 45a of the keylever 45 and is biased in a counterclockwise direction as viewed in FIG. 1 by a coil spring 50 connected to its free end so as to bias the key lever 45 upwardly toward a frame stop 47a.

A clutch arm 51 pivotally mounted on a shaft 52 rigidly mounted on the typewriter side frame 31, is biased in a clockwise direction by a spring 53 connecting the clutch arm 55 to a bent out ear 54 of a frame mounted bracket 55. The frame mounted bracket 55 is rigidly mounted on the typewriter side frame 31 by a pair of screws 56 as shown more clearly in FIGS. 4 and 5. A friction shoe 57 fastened to an upwardly projecting end of the clutch arm 51 is adapted to press against the phenolic collar 42 when the clutch arm 51 is pivoted clockwise, thereby producing sufficient drag on the phenolic collar 42 to cause the wrap spring 13 to engage the driven member 33 and thereby drive the carriage return reel 10 clockwise winding the carriage return drawband 11 thereon.

The clutch arm 51 is controlled by a clutch release arm 59. The clutch release arm 59 extends from a U-shaped bridge structure 61 pivotally mounted on shaft 52 adjacent to the clutch arm 51 and having a laterally bent off tail portion 61a adapted to overlie a laterally bent off tail portion 62 of the clutch arm 51. Threaded to and extending through the laterally bent off tail portion 61a of the clutch release arm 59 is a threadably adjustable member 63 adapted to engage the laterally bent off tail portion 62 of the clutch arm 51. The clutch release arm 59 is biased in a clockwise direction by a coil spring 64 connected to the frame mounted bracket 55.

The frame mounted bracket 55 also provides a steplike stop arrangement consisting of a primary stop 65 and a secondary stop 66 as more clearly viewed in FIGS. 4 and 5, adapted to be engaged by a bent off ear 67 of a clutch release pawl 68 pivotally mounted about a stud 68a on a laterally offset portion 59a of the clutch release arm 59. Thus the primary stop 65 serves to limit clockwise movement of arm 59 which in turn via the threadably adjustable member 63 threaded thereto limits clockwise movement of clutch arm 51 and maintains the wrap spring 13 unwrapped. A spring 69 connecting the laterally offset portion 59a of the clutch release arm 59 and the clutch release pawl 68 biases the clutch release pawl 68 in a clockwise direction as viewed in FIG. 4. A bent off ear 67a is provided on the clutch release pawl 68 to limit clockwise movement of the clutch release pawl 68 by abutting an edge of the laterally offset portion 59a of the clutch release arm 59.

Upon the depression of key lever 45, the ear 67 of the clutch release pawl 68 is adapted to be shifted off the primary stop 65 and, as will hereinafter appear, be caught by the secondary stop 66. More particularly the bent off ear 71a of a key lever bypass and action trip pawl 71 pivotally mounted on a stud 72a fixed to a laterally offset downwardly projecting extension 72 of the key lever 45 is adapted to extend below the primary stop 65 and push against ear 67 when the carriage return key lever 45 is depressed. The key lever pawl 71 also includes a bent off ear 70 which limits clockwise movement of the key lever pawl 71 and is normally biased clockwise into abutment with an edge of the extension 72 by a spring 73 connecting the key lever pawl 71 and the extension 72. The clutch release pawl 68 is adapted to shift from the secondary stop 66 and to catch the primary stop 65 as a result of counterclockwise movement of the clutch release arm 59 as will hereinafter be discussed.

Referring again to FIG. 1, a T-shaped center stop lever 80 movably mounted intermediate the extremity of its vertical leg on a stud 79 secured to the typewriter frame between a pair of center limit stops 82 and 83, is biased in a forward direction into abutment with an enlarged head 79a of the stud 79 by a spring 78 telescoping the stud 79. The T-shaped center stop lever 80 has an enlarged lower portion 84 to which is connected an intermediate link 85 extending to the right as viewed in FIG. 1 into connection with the arm 86 of a bellcrank 87 pivotally mounted on a downwardly extending frame supported stud 88. The bellcrank 87 is biased in a counterclockwise direction into abutment with a stop 89 as viewed in FIG. 1 by a coil spring 90 connecting an upwardly projecting bent off ear 86a on the arm 86 of the bellcrank 87 to the typewriter frame.

A rigid clutch release link 92 extends forward from an aperture in a bent off shelf 91a on the other arm 91 of the bellcrank 87 through a guide 92a into close proximity with the clutch release arm 59.

To minimize carriage return drawband loop-out at the termination of carriage movement, a braking mechanism, generally identified by the reference numeral 93, is provided, comprising a pair of upwardly extending levers 96 and 97 pivotally mounted on a frame supported stud 98. As shown in FIGS. 6 and 7, the lever 97 of the braking mechanism 93 has a forwardly extending bent off ear member 99 with a friction surface 99a adapted to engage the periphery of the carriage return reel 10, but is normally out of contact with it as shown in FIG. 6. The lever 96 has a rearward projection, a rearward projection 101 to which there is connected a coil spring 102 extending upwardly to a rearward projection 108a of the lever 96. The coil spring 102 is adapted to bias the rearward edge of the lever 96 against a laterally extending bent off ear 103 formed on the rear edge of lever 97 into abutting relationship. As seen in FIG. 1, the clutch release link 92 stands normally rearwardly moved by the arm 91 supporting its rear end, such arm being part of a lever 87 which under the influence of a spring 90 is normally in contact with a stop 89. Obviously, in such position of the lever 87, the lever 96 and the related lever 97 are positioned as shown in FIG. 6, wherein the friction surface 99a on the lever 97 stands clear of the peripheral surface of the reel 10. A laterally bent off ear 96a on the uppermost portion of lever 96 has an open ended slot 108 therein overlying the clutch release link 92 and is positioned in the path of an adjustable V-shaped locking clip 109 mounted on the clutch release link 92. When the clutch release link 92 moves in a forward direction the clip 109 is adapted to pivot the lever 96 counterclockwise as viewed in FIG. 7 causing the coil spring 102 to urge the lever 97 counterclockwise and the friction surface 99a of the ear member 99 into braking engagement with the carriage return reel 10.

In operation, when the carriage return key 45 i depressed, the bent off ear 71a of the key lever pawl 71 engages the bent off ear 67 of the clutch release pawl 68 pivoting the clutch release pawl 68 counterclockwise as viewed in FIGS. 4 and 5, thereby moving the bent off ear 67 of the clutch release pawl 68 out of abutment with the primary stop 65 and through the action of the spring 64 into abutment with the secondary stop 66. The movement of the clutch release pawl 68 beyond the primary stop position allows the spring 64 to pivot the clutch release arm 59 clockwise a sufficient distance to enable the spring 53 to pivot the clutch arm 51 clockwise causing the friction shoe 57 to frictionally engage the phenolic collar 42 and thereby cause the driven wrap spring 13 to wrap about the driven member 33 coupling the carriage return reel 10 to the continuously rotating shaft 12.

With the carriage return reel 10 coupled to the continuously rotating shaft 12, the carriage return reel 10 winds the carriage return drawband 11. As the carriage return drawband load cushioning device 16 yields permitting the bellcrank 21 to pivot clockwise as viewed in FIG. 2 and the carriage return drawband 11 to pick up the load of the carriage 19 in a gradual manner. The clockwise movement of the bellcrank 21 is limited by the stop 28 at a point in which the moment arm of the spring 26 is designed to have a minimal value, so that minimal carriage load on the carriage return drawband 11, even after carriage return movement has commenced, is sufficient to prevent the spring 26 from returning the bellcrank 21 in a counterclockwise direction and accelerating the carriage return movement.

At the end of carriage return, a left-hand margin stop 113 carried by the carriage 19 strikes the T-shaped center stop lever 80 or if the margin release key lever (not shown) happens to be depressed so as to rock the upper portion of the T-shaped center stop lever 80 backwards out of the path of the left-hand margin stop 113, a final stop 114 on the carriage 19 strikes the T-shaped center stop lever 80, pivoting the T-shaped center stop lever 80 clockwise as viewed in FIG. 1. Thereby, through the intermediate link 85 pivoting the bellcrank 87 clockwise as viewed in FIG. 1, the rigid clutch releasing link 92 moves forward into engagement with the clutch release arm 59. The engagement of the clutch release arm 59 by the clutch release link 92 pivots the clutch release arm 59 counterclockwise thereby causing the threadably adjustable member 63 to drive the laterally bent off tail portion 62 of the clutch arm 51, pivoting the clutch arm 51 counterclockwise and moving the friction shoe 57 fastened to the clutch arm 51 out of frictional contact with the phenolic collar 42. As the clutch release arm 59 moves counterclockwise the ear 67 of the clutch release pawl 68 moves out of contact with the secondary stop 66 and is biased into abutment with the primary stop 65 by the spring 64. In instances in which the carriage return key lever 45 is maintained in a depressed condition overlong, the ear 67 of the clutch release pawl 68 raises the bent off ear 71a of the keylever bypass and action trip pawl 71 pivoting the key lever pawl 71 counterclockwise about its pivot against the action of the spring 73. As a result, the ear 67 is able to abut the primary stop 65 and when the carriage return key lever 45 is released the spring 73 pivots the key lever pawl 71 clockwise to a normal position.

With the drag of the friction shoe 57 removed from the phenolic collar 42, the wrap spring 13 unwraps disengaging the continuously rotating shaft 12 from driven member 33 and the carriage return reel 10, thereby terminating the power winding of the carriage return drawband 11.

Also, with the removal of the carriage load from the carriage return drawband 11, the energy stored in the spring 26 pivots the bellcrank 21 counterclockwise as viewed in FIGS. 1 and 2 until the arm 23 is in abutment with stop 28.

So as to minimize over feed-out of the carriage return drawband 11 from the carriage return reel 10 as a result of the bellcrank 21 returning to its normal position, as the rigid clutch release link 92 moves forward to engage the clutch release arm 59, the U-shaped adjustable locking clip 109 mounted thereon moves the lever 96 counterclockwise as viewed in FIGS. 1 and 7, allowing the spring 102 to pivot the lever 97 counterclockwise, which urges the friction member 99a into frictional contact with the periphery of the carriage return reel 10 braking the feeding out of the carriage return drawband 11 from the now no longer driven carriage return reel 10 due to drawband tension and the action of spring 26.

A main spring barrel (not shown) then moves the carriage 19 to the left into engagement with an escapement pawl (not shown) allowing the biasing action of spring 90 mounted on the bellcrank 87 to return the T-shaped center stop lever 80 counterclockwise to a normal position as viewed in FIG. 1 and the clutch release link 92 and the V-shaped adjustable locking clip 109 rearwardly. With the rearward movement of the V-shaped adjustable locking clip 109, the coil spring 102 urges the rearward edge of the lever 96 and the laterally extending bent off ear 103 formed on the rear edge of the lever 97 into abutting relationship thereby deactivating the brake mechanism 30 and reassuming the position illustrated in FIG. 6.

With the present invention, there is thus provided a new and improved carriage return mechanism in which not only is shock and stress and strain on the carriage return drawband significantly reduced but the problem of carriage return drawband loop-out is also minimized.

Claims

I claim:

1. In a carriage return mechanism having:

a frame

a carriage return drawband connected at one end to a carriage,

a reel on said frame for winding the other end of the carriage return drawband thereon,

a power source for driving said reel,

a normally disabled clutch interposed between the reel and the power source,

a key controlled mechanism for closing said clutch and thus coupling the reel to the power source to cause said reel to wind up carriage return drawband thereon the effect return movement of the carriage,

and a carriage load cushioning device associated with said drawband at a location intermediate said clutch and the carriage and comprising,

a pulley around a part of the periphery of which the drawband extends on its way from said reel to the carriage,

a swingable arm member carrying said pulley on an arm thereof to be displaced swingably from a normal position when said drawband commences to be power drawn by said reel against the opposition of substantially the full static energy of the carriage,

a stop from which said arm member is swingably displaceable from its normal position,

and spring means associated with a pulley carrying arm member, being strong enough normally to bias said arm member against said stop and furthermore being of such strength that upon closure of said clutch, the drawband will effect a pivotal displacement of the arm member against the influence of said spring means only as substantially the full static energy of the carriage is encountered and so that carriage return effecting force becomes transmitted to the carriage in a cushioned manner to gradually overcome the static energy of the carriage and then to effect the return of the carriage.

2. The device as recited in claim 1, including means to limit the degree of pivotal movement of said arm member from said stop in order that then the band transmits carriage return movement positively.

3. The device as recited in claim 2, said spring means having joint connections with said arm member and the frame, so arranged in respect to the pivot for said arm member that the spring means progressively acts with a decreasing moment arm as the arm member becomes operated to the limit of said limit means and so that the spring means is unable to effect the restoration of the arm member until the carriage return clutch opens.