US3207283A - Type bar action - Google Patents

Description

p 1965 A. R. JOHNSON 3,207,283

TYPE BAR ACTION Filed July 16, 1962 2 Sheets-Sheet 1 INVENTOR ARTHUE. JOljNSON M5 fi \3Q&.Q,L-%

ATTORNEYS Sept. 21, 1965 A. R. JOHNSON TYPE BAR ACTION 2 Sheets-Sheet 2 Filed July 16, 1962 V NT R ARTI- IP IR R. 9OHNSON g, ATTORNEYS United States Patent 3,207,283 TYPE BAR ACTION Arthur R. Johnson, Wethersfield, Conn., assignor to Royal McBee Corporation, New York, N.Y., a corporation of .New York Filed July 16, 1962, Ser. No. 209,851 9 Claims. (Cl. 197-17) This invention relates to a type bar action for controlling the deceleration of a type bar on its return stroke to the headrest.

Conventional power driven writing machines of the basket type are commonly characterized by a headrest against which the type bar strikes at the end of its return stroke after making an imprint. A spring is customarily used to effect such return stroke. In order to attain high speed typing, such a spring must be relatively powerful in order to clear the type bar from a position near the platen so as to make way for the imprint stroke of a succeeding bar to preclude jamming of two bars at or near the printing position. The force of impact of a returning bar on the headrest is a function of the tension or power of the return spring, the greater the tension at the start of the return stroke, the greater the impact on the headrest at the end of the return stroke. Hence if a very strong spring is used, the impact will be correspondingy high resulting in a high rebound reaction of the bar upon hitting the headrest. Various headrest cushioning expedients are resorted to in an eifort to absorb the impact energy of the returning bar to prevent excessive rebounding thereof and to reduce noise. It has been found, however, that there is a limit to the amount of cushioning that can be provided in a headrest and that limit is directly related to the maximum return spring tension that can be used. Thus there is a definite limitation placed on typing speed which limitation may be, and often is, well below the printing capacity of the machine.

In high speed operation of a power driven writing machine, energy is expended by the machines power roll in driving the type bar to printing position. Where a spring is used to return the bar, a good portion of the springs return energy is supplied to the spring by the power roll during the type bar printing stroke. This energy is transferred from the spring to the bar during the bars return and is ultimately absorbed or dissipated by the headrest and is not returned to the power roll. Hence the speed of the power roll is inclined to fluctuate which not infrequently results in non-uniform printing impression.

It is accordingly among the objects of my invention to provide a type bar deceleration mechanism that overcomes the above mentioned disadvantages in a thoroughly practical and efiicient manner.

Another object is to provide a mechanism of the above nature wherein type bar rebound is completely eliminated. A still further object is to provide such a mechanism whereby much higher type bar return speeds may be used thus making possible a substantial increase in typing speed. Another object is to provide a mechanism of the above nature wherein the energy supplied to the type bar to effect its return is returned to the drive source for use in the next typing cycle thus to maintain the drive roll speed constant regardless of the typing speed and to attain more uniform type impression. Other objects will be in part apparent and in part pointed out herein below.

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In the drawing wherein I have shown two embodiments of my invention and whereinsimilar reference characters refer to similar parts throughout the several views:

FIGURES 1-5 are schematic views showing the condition of the mechanism at Figure Normal position 1 Start of acceleration 2 End of acceleration 3 Free flight 4 Start of deceleration- 5 FIGURES 6-10 are schematic views of a modified form of the mechanism showing its condition at Referring now to FIGURE 1 a power roll 20 is rotatably mounted on the machine frame F to be driven in the conventional manner. A type bar actuating arm 21 is pivotally mounted on a cross shaft 22 carried by the machine frame and is under the clockwise bias of a return spring 23 whose opposite ends are connected to the arm and frame respectively. One end of a link 24 is pivotally connected to the upper end of arm 21, the other end of the link being pivotally connected to one end of a type bar 25 rockably mounted on a pivot 26 and normally lying against a headrest 27 which may or may not be cushioned as desired. Thus when arm 21 is rocked counterclockwise, in a manner to be described, type bar 25 is swung clockwise to printing position (see FIGURE 4). After printing, the type bar and arm are returned to normal position (FIGURE 1) by return spring 23.

Arm 21 carries between its ends a pin 28 on which are pivotally mounted a type bar drive accelerating cam 29 and a type bar return decelerating cam 30, these cams being provided with power roll engaging surfaces 29a and 30a. Edge 29b of cam 29 normally rests against a stop 31 on arm 21 against which it is held by the clockwise bias of a cam return spring 32. A trigger lip 33 projects from the face of cam 29 and overlies the nose 34a of a trigger 34 pivotally mounted on a pin 35. Trigger 34 is operatively associated in any suitable manner with the key lever (not shown) which corresponds with type bar 25. It may now be seen that when such key lever is depressed trigger 34 is rocked counterclockwise so that its nose 34a forces lip 33 upward causing cam 29 to pivot counterclockwise to the FIGURE 2 position where point A of its surface 29a engages the surface of power roll 20 whereby acceleration of the cam is started. Point A lies on or closely adjacent to a line passing through the axes of cam 29 and power roll 20. Acceleration of cam 29 ends when point B on its surface 29a quits engagement with the surface of power roll 20 (see FIGURE 3). It should be noted that as the cam is accelerated from zero to full velocity its point of contact moves away from the line passing through the axes of the cam and power roll in a direction opposite to the direction of rotation of the power roll as indicated by the broken line arrow in FIGURE 3. This assures complete control of the cams acceleration.

When the cam 29 reaches its FIGURE 3 position at the end of acceleration, arm 21 and type bar 25 have reached their middle position and start their free flight which continues to the FIGURE 4 position, the printing position of the type bar. An over-centering spring 37 has one end connected to cam 30 and its other to arm 21, the connections being so located that the spring normally biases edge 30b of the cam counterclockwise (FIGURE 1) against a stop 38 on arm 21 thus to limit counterclockwise movement of the cam. However, when the cam reaches the end of its acceleration (FIGURE 3) its edge 30b engages a frame supported reset stop 39 which, upon the continuing free flight of arm 21 causes the spring 37 to overcenter thus to rock the cam clockwise to its FIGURE 4 position wherein it is held by the stud 37a on cam 30, to which the upper end of spring 37 is attached, bearing against the top of cam 29.

The FIG R 4 it an f the mech n s marks the d o f e fli ht n h a t f the r t drive n e the pu l of urn s n 23 wh h wa t s an during the acceleration and ree fl ht ar isans 9f h l Thus when cam 30 reaches the FIGURE position which marks the start of deceleration point C on its surface 30a engages the surface of power roll 20, Point C being spaced from the line passing through the axes of cam 30 and roll in the direction of rotation of the roll. As arm 21 continues its clockwise movement under the pull of spring 23 cam is rocked count'erclockwise at its point of engagement with the power roll moves from point C (FIGURE 5) to point D (FIGURE 1) which is closely adjacent to or on the 'line passing through the axes of the cam and roll; thus the point of contact moves in a direction opposite to the direction of rotation roll 20 to provide complete and unlimited control of deceleration of type bar 25. As cam 30 moves counterclockwise from its FIGURE 5 to its FIGURE 1 position, spring 37 again overcenters so that the cam comes to rest in its normal position against stop 38 on arm 21. Also cam 29 is returned to its normal position where its lip 33 overlies trigger nose 34a, the trigger having been returned to its normal position against a stop 34b by a trigger spring 340.

From the foregoing it may be seen that return spring 23 may be more powerful than a conventional spring of this nature because of the complete deceleration control described. As the deceleration is controlled from maximum to zero velocity, type bar 25 comes to rest against headrest 27 when its velocity is zero or substantially so, the energy of the type bar being returned to power roll 20 through cam 30. Thus no type bar rebound is possible, higher speed typing is made possible and uniform type impression is attained.

In the modified form of the invention shown in FIG- URES 6-10 a type bar actuating arm is pivotally mounted on a cross shaft 51 carried by the machine frame and has attached to the upper end thereof one end of a return spring 52 and one end of a type bar operating link 53. The other end of return spring 52 is attached to the machine frame and accordingly biases arm 50 clockwise toward power roll 20. When arm 50 is driven to the left by roll 20, in a manner to be described, type bar 25 is rocked to printing position as noted above in connection with FIGURES 1-5.

A roll cam, generally indicated at 54 is rotatably mounted on a pin 55 carried by arm 50 between its upper end and axis. Cam 54 is provided with a curved accelerating surface 54a which may extend from a point A to a point B thereon, the cam also having a decelerating surface 54b which may extend from a point C to a point D, surfaces 54a and 54b being joined by a fiat 54c whose radii are less than those of surfaces 54a and 541) at points A and C respectively. A pair of lips 56 and 57 extend from one surface of cam 54, lip 56 being engaged by the nose 58a of a trigger 58 to latch the cam in its rest or normal FIGURE 6 position. Trigger 58 is pivotally mounted on a cross shaft 59 carried by the machine frame and has an arm 58b operatively associated in any suitable manner with a keylever (not shown) whereby upon depression of such lever, trigger 58 is rocked clock wise to unlatch the trigger nose 58a and cam lip 56.

An overcentering spring 60 has one end connected to cam 54 at a point 60a, the other end of the spring being connected to a finger 61 which .is preferably integral with arm 50. When cam 54 is in its normal FIGURE 6 position spring 60 biases cam 54 counterclockwise so that trigger lip 56 bears against trigger nose 58a which accordingly holds the cam with its flat 54c spaced from the driving surface of power roll 20. When trigger 58 is actuated by a key lever its nose 58a is withdrawn from in front of lip 56 permitting spring 61 to rotate cam 54 counterclockwise to its FIGURE 7 position wherein point A on its accelerating surface 54;: engages the power roll to start the acceleration portion of the cycle.

As cam 54- is driven by the power roll from its FIG- URE 7 to its FIGURE 8 position which latter position marks the end of acceleration, arm 50 is rocked counterclockwise and is accelerated to its maximum velocity as is also the type bar. It will be noted that the point of engagement A between the cam and roll lies on or closely adjacent to a line passing through the axes of the cam and roll and that at the end of acceleration at point B the point of engagement has moved in a direction opposite to the direction of rotation of power roll 20 thus providing complete and unlimited control of acceleration of arm 50. The energy xpended by the power roll in driving and accelerating arm 50 is stored in return spring 52.

As noted above when the mechanism is in its FIG- URE 8 position the acceleration portion of the cycle ends and the parts are in free flight to their FIGURE 9 position wherein the type bar is in printing position and makes an impression. As described above, arm 50 is provided with projecting lip 57 which is adapted to strike a cam reset 63 at the start of the-free flight portion of the cycle (FIGURE 8). When this occurs cam 54 is rocked clockwise about its pivot 55 causing spring 60 to overcenter and rock the cam until its lip 56 engages a stop 64. In the meantime return spring 52 has swung arm 50 from its end of free flight position (FIGURE 9) to its start of deceleration position (FIGURE 10) where point C on cam surface 54b engages roll 20 at a point spaced from the line passing through the cam and roll axes in the same direction as that of roll rotation.

Deceleration of arm 50 and accordingly its associated type bar is effected as the point of engagement of cam surface 54b and roll 20 moves from C to D, it being noted that the direction of this movement is opposite to that of roll rotation to afford completely controlled deceleration. As this movement continues the energy that was stored in return spring 52 is returned to roll 20 thus maintaining the roll speed constant and affording uniform type impression. As the velocity of arm 50 is decelerated to zero or practically so at the end of deceleration (FIGURE 6) type bar 25 comes to rest against headrest 27 at substantially zero velocity thus precluding any possibility of rebound. Also movement of cam 54 from the FIGURE 10 to the FIGURE 6 position causes spring 60 to overcenter again so that trigger nose 58a and cam lip 56 relatch with cam flat 54c opposed to and spaced from the driving surface of power roll 20.

It will now appear that I have provided a mechanism for controlling the deceleration of a type bar that attains the several objects set forth above in a thoroughly practical and eflicient manner.

As other embodiments of the invention are possible and as changes can be made in the ones disclosed, all without departing from the scope of the invention, it is to be understood that the foregoing is to be interpreted as illustrative and not in a limiting sense.

I claim:

I. A type bar action for a writing machine in combina tion,

a frame.

a type bar pivotally mounted on said frame,

a hea-drest on said frame for said bar,

means including a pivoted actuating arm for pivoting said bar from said headrest to printing position,

a return spring connected to said arm to return it and said bar to normal position,

a power roll rotatably mounted on said frame,

and oscillatable roll cam means on said arm having accelerating and decelerating portions which serially engage said roll first to accelerate said arm and bar from zero to maximum velocity and then, after printing, to decelerate said arm and bar from maximum return velocity to zero at said headrest.

2. Mechanism in accordance with claim 1 wherein said accelerating and decelerating portions are so arranged that said arm and bar are in free flight from the end of acceleration to the arrival of said bar at the printing position.

3. Mechanism in accordance with claim 1 wherein said roll cam means comprises two identical cams, and means mounting said cams on said arm on a common axis.

4. Mechanism according .to claim 1 wherein said cam means comprises a single element, said cam portions being joined by a flat which is spaced from said power roll when the mechanism is in normal condition.

5. Mechanism according to claim 1 provided with means including an overcentering spring connected to said arm and to said cam means for effecting engagement between said decelerating portion and said power roll after said type bar leaves the printing position.

6. Mechanism according to claim 5 wherein said last mentioned means includes a stop on said frame adapted to be engaged by a lug on said cam which, upon engagement during the return movement of said arm, cause said spring to overcenter.

7. Mechanism according to claim 1 including means operable in response to manipulation of the writing machine for triggering said cam means to effect engagement between said accelerating portion and said power roll.

8. Mechanism according to claim 1 wherein the point of engagement between said decelerating cam portion and said roll is at a point spaced from a line passing through the axes of said cam means and roll in the direction of rotation of the roll and moves toward said line during deceleration.

9. A type bar action for an electric typewriter comprising, in combination,

a frame,

a type bar pivotally mounted on said frame,

means including an actuating arm for pivoting said bar from rest .to printing position,

a return spring connected to said frame and said arm for returning said arm to rest position,

a smooth surfaced power roll rotatably mounted on said frame,

a pair of oscillatable cams mounted on a common pivot on said arm adjacent said power roll,

spring means interconnecting said cams and said arm to normally bias said cams away from said power roll, one of said cams being engageable with said power roll to accelerate said arm and bar from zero to maximum velocity and the other of said cams being engageable with said power roll to decelerate said arm and bar from maximum return velocity to zero at the rest position of said arm and bar, and

means to eflect engagement of said accelerating cam with said power roll.

References Cited by the Examiner UNITED STATES PATENTS 1,732,155 10/29 Egli 197l7 1,963,285 6/34 Woodward 197-17 X 3,021,934 2/62 Enders l9717 ROBERT E. PULFREY, Primary Examiner.

Claims (1)

1. A TYPE BAR ACTION FOR A WRITING MACHINE IN COMBINATION, A FRAME, A TYPE BAR PIVOTALLY MOUNTED ON SAID FRAME, A HEADREST ON SAID FRAME FOR SAID BAR, MEANS INCLUDING A PIVOTED ACTUATING ARM FOR PIVOTING SAID BAR FROM SAID HEADREST TO PRINTING POSITION, A RETURN SPRING CONNECTED TO SAID ARM TO RETURN IT AND SAID BAR TO NORMAL POSITION, A POWER ROLL ROTATABLY MOUNTED ON SAID FRAME, AND OSCILLATABLE ROLL CAM MEANS ON SAID ARM HAVING ACCELERATING AND DECELERATING PORTIONS WHICH SERIALLY ENGAGE SAID ROLL FIRST TO ACCELERATE SAID ARM AND BAR FROM ZERO TO MAXIMUM VELOCITY AND THEN, AFTER PRINTING, TO DECELERATE SAID ARM AND BAR FROM MAXIMUN RETURN VELOCITY TO ZERO AT SAID HEADREST.

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