US3581859A

US3581859A - Position sensitive mechanical feedback control

Info

Publication number: US3581859A
Application number: US762695A
Authority: US
Inventors: Arthur R Johnson
Original assignee: Litton Business Systems Inc
Current assignee: TRIUMPH-ADLER AG A CORP OF GERMANY; Western Atlas Inc
Priority date: 1968-09-26
Filing date: 1968-09-26
Publication date: 1971-06-01
Anticipated expiration: 1988-06-01

Abstract

A power mechanism having a control member and a power delivery member connected to respective ends of a wrap spring wound around a continuously rotating shaft. The control member is adapted to follow a universal bar and, in response to movement of the universal bar in a predetermined direction, to cause the wrap spring to couple the power delivery member to the continuously rotting shaft until the power delivery member is driven through an angle equal to that traveled by the control member.

Description

United States Patent ml 1 [72] Inventor Arthur R. Johnson 2,875,880 3/1959 Palmer 197/17 Wethersfield, Conn. 2,973,078 2/1961 Templeton et a1, 197/17 [21] Appl. No 762,695 3,077,971 2/1963 Palmer 197/71X [22] Filed Sept. 26,1968 3,086,635 4/1963 Palmer 197/16 [45] Patented June 1,1971 3,157,265 11/1964 Palmer 197/16 [73] Assignee Litton Business Systems, Inc. 3,191,740 6/1965 Smusz et a1. 197/16 New York, N.Y. 3,348,648 10/1967 Frechette 197/16 3,349,886 10/1967 Madison et a1. 197/107 [54] POSITION SENSITIVE MECHANICAL FEEDBACK CONTROL 2 Claims, 2 Drawing Figs.

[52] U.S.Cl 197/17, 197/97 [51] Int. Cl B41j 23/08 [50] Field of Search 197/16, 17,

[56] References Cited UNITED STATES PATENTS 1,936,466 11/1933 Crumrine 197/97 2,155,997 4/1939 Sterling 197/97X Primary Examiner-Ernest T. Wright, Jr. Attorney.loseph R. Spalla and Cornelius P. Quinn ABSTRACT: A power mechanism having a control member and a power delivery member connected to respective ends of a wrap spring wound around a continuously rotating shaft. The control member is adapted to follow a universal bar and, in response to movement of the universal bari-ina predetermined direction, to cause the wrap spring to couplethe power delivery member to the continuously rotting shaft until the power delivery member is driven through an angleequal to that traveled by the control member.

PATENTED JUN Il97l 3 5 1,859

INVENTOR ARTHUR R. JOHNSON BY 5% M ATTORNEY POSITION SENSITIVE MECHANICAL FEEDBACK CONTROL BACKGROUND OF TH E INV ENTION This invention relates to mechanisms for transmitting power to auxiliary mechanisms in an electric typewriter at a rate related to the movement of individual type actions, and more particularly it relates to a power transmitting mechanism which delivers power at a velocity directly related to and substantially over the interval of movement of a universal bar driven by individual type actions.

It is well known in electric typewriters having type actions of the type bar type for each of the type actions to include a sublever operative to drive a universal bar. The universal bar when driven by any one of the sublevers often operates auxiliary mechanisms, for lifting ribbon, tripping an escapement and in some instances even feeding a ribbon through the machine.

In order to produce high quality print work in a type bar machine it is necessary to maintain the velocity of a driven type bar and its impact with the platen within relatively close tolerances, otherwise the color density of the print work will not be constant and a mixture of light and dark type impressions will result.

Unfortunately, the power demands made by these auxiliary mechanisms are not constant and often impose variable loads on the type actions which vary the velocity of a driven type bar and its impact with the platen beyond allowable limits, consequently impairing the quality of the print work.

While it has been suggested in the prior art to use a power mechanism triggered by the universal bar to drive the auxiliary mechanisms so as to remove the load of the auxiliary mechanismsfrom the type actions, these prior art devices have not been entirely satisfactory. In the known prior art devices, the power mechanisms are cyclic and once the power mechanism is triggered by the universal bar, the power mechanism operates through a preset cycle independently of the universal bar. Thus, the time interval in which any particular auxiliary mechanism goes through its cycle of operation is constant regardless of whether the universal bar is actuated by an action associated with a center type bar or an action associated with an end type bar. Consequently, the power mechanism cannot be retriggered until it has completed a preset cycle resulting in delays, which in some instances such as calling for anew character, is particularly objectionable. Also, in the case of an auxiliary mechanism such as a ribbon lift, for example, since the time interval between a type bar leaving its headrest and striking a platen increases progressively from the center type bar to an end type bar, in order to insure that the ribbon is in front of the type bar when the type bar strikes the platen, means must be provided to adjust the triggering time of the power mechanism for each individual type action, either by providing an irregular shaped universal bar or by varying the cam surface of each sublever.

SUMMARY OF THE INVENTION The present invention provides an electric typewriter having a plurality of type actions and a universal bar driven by the type actions, with a power mechanism for powering auxiliary mechanisms such as a ribbon lift mechanism as well as escapement trip mechanisms and the like, in response to the movement of the universal bar and at the rate of or a rate related to the movement of the universal bar. The power mechanism has a control member and a power delivery member connected to respective ends of a wrap spring wound about a continuously rotating shaft. The control member is responsive to movement of the universal bar and is followed by the power delivery member which is caused to be coupled to the continuously rotating shaft by the wrap spring during movement of the control member in a predetermined direction and at the rate of movement of the control member.

Accordingly, one of the objects of the present invention is to provide an electric typewriter for producing print work of constant color density.

Another object of the present invention is to eliminate any variations in type bar velocity and impact with the platen as a result of the power demands of auxiliary mechanisms.

Another object of the present invention is to divorce the type actions from the effect of the power demands necessary to operate auxiliary mechanisms.

Another object of the present invention is to provide a power mechanism in which the velocity of power delivered to the auxiliary mechanisms has a direct relation to a control velocity.

Still another object of the present invention is to provide a noncyclic power mechanism for delivering power to the auxiliary mechanisms at a velocity having a direct relation to the velocity ofa universal bar.

Other objects and advantages of the present invention will become obvious to those skilled in the art from a consideration of the following description read in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a perspective view of a portion of an electric typewriter embodying the power mechanism of the present invention.

FIG. 2 is a front elevation view partly in section of the power mechanism of the present invention in a normal inoperative position.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION Referring now to the drawing wherein like reference characters designate like or corresponding parts throughout the several views, the power assist mechanism of the present invention is shown in conjunction with an electric typewriter employing type bars. As illustrated in FIG. 1, a portion of a sublever 10 is pivotally mounted on a shaft 12 secured to the frame and is articulately connected by a link 14 to a type bar 16 pivotally mounted on a segment wire 18. The sublever 10 is adapted to be pivoted counterclockwise as viewed in FIG. I by powered actuating means (not shown) to drive the type bar 16 from a headrest 113 into contact with a platen 20. A return spring 22 connected to the sublever 10 returns the type bar 16 and sublever 10 to their normal positions after typing impact with the platen 20.

A forwardly extending tail 24 of the sublever 10 overlies a universal bar 26 pivotally mounted on the shaft 12 so that when the sublever 10 is pivoted counterclockwise the universal bar 26 is also pivoted counterclockwise, and when the sublever 10 returns to its normal position, the universal bar 26 is returned to a normal clockwise position against a stationary stop 27 by a spring 28 connecting the universal bar 26 to the machine frame.

A power assist mechanism generally designated by the numeral 32 comprises two levers, a control lever 34 and a power delivery lever 36, rotatably mounted between a pair of

bushings

37 and 39 on a continuously counterclockwise rotating shaft 38 extending from the end of a power roll or snatch roll (not shown). The control lever 34 is articulately connected to the universal bar 26 by a link 30 and the power delivery lever 36 is connected to an auxiliary mechanism (not shown) by a link 49.

The control lever 34 and the power delivery lever 36 are connected together by a wrap spring 40 wrapped clockwise from right to left about the rotating shaft 38 as viewed in FIG. 2. A control end 45 of the wrap spring 40 is received in a slot 41 in the control lever 34 and a delivery end 46 of the wrap spring 40 is received in a slot 48 in the power delivery lever 36. The wrap spring 40 is wound that clockwise rotation of the control lever 34 urges the wrap spring 40 to open as does counterclockwise rotation of the power delivery lever 36.

Counterclockwise rotation of the control lever 34 causes the wrap spring 40 to grip and to be driven by the continuously rotating shaft 38 thereby to transmit driving movement to the power delivery lever 36 until the power delivery lever 36 reassumes its normal angular position relative to the control lever 34 following cessation of control lever movement in counterclockwise direction.

The wrap spring 40 is wound in an interference fit with the shaft 38 as shown in H6. 2 when an immediate sensing response is desired, or with a slight clearance if an initial motion response delay is acceptable. The control lever 34 is biased in a normal clockwise position by the spring 28 urging the universal bar 26 clockwise against the stationary stop 27, and the power delivery lever 36 is biased in a normal clockwise position by a spring 42 connected to the power delivery lever 36 urging the power delivery lever 36 clockwise against a stationary stop 44.

In operation, as the sublever l pivots counterclockwise to drive the type bar 16 into contact with the platen 20, the forwardly extending tail 24 of the sublever pivots the universal bar 26 counterclockwise.

counterclockwise movement of the universal bar 26 moves the control lever 34 counterclockwise allowing the wrap spring 40 to grip the counterclockwise rotating shaft 38 which power drives the wrap spring 40 until the power delivery lever 36 reassumcs a normal angular position relative to the control lever 34 following cessation ofcounterclockwise movement of the universal bar 26 and control lever 34. After the type bar 16 has impacted against the platen 20 and begins its return to head rest 13 the universal bar 26 also begins to return in a clockwise direction, under the action of the spring 28, into abutment with the stop 27. During this clockwise return movement the control lever 34 moves clockwise urging the wrap spring 40 to open and allowing the power delivery lever 36 to move clockwise under the action of the spring 42 until the control and power delivery levers 34 and 36 reassume their normal angular clockwise relationship. Any tendency of the wrap spring 40 to wrap from left to right during the return movement of lever 36 by spring 40 will be opposed by the counterclockwise rotating shaft 38. Should another type action be initiated during return movement of the universal bar 26, the sublever 10 of the next called action will arrest and reverse the direction of the universal bar 26 and again cause immediately the actuation of the power assist mechanism 32.

With the power assist mechanism 32, the link 49 connected to the power delivery lever 36 is used to transmit the power from the continuously rotating shaft 38 to operate the auxiliary mechanisms of the type discussed previously.

As a result, instead of requiring the universal bar 26 to transmit power from the sublever 10 which will result in a variable load being imposed on the type action, or requiring it to actuate a power mechanism, with the velocity output of the power mechanism independent of the velocity of the universal bar 26, the universal bar 26 in accordance with the invention now merely moves with the sublever 10, without loading sublever [0, and the motion of the universal bar 26 is sensed and followed by the control lever 34 of the power assist mechanism 32 which then supplies all of the power necessary to drive the auxiliary mechanisms from the rotating shaft 38, at the rate of movement of the universal bar 26. Thus the load is divorced from the universal bar 26 and type action. As a consequence there is eliminated the need for an irregular shaped universal bar 26 or other such means for varying the triggering time of the power mechanism for each type action. Also, since the power assist mechanism 32 is noncyclic it is always prepared to deliver power to an auxiliary mechanism lever 34, and the link 49 on the power delivery lever 36.

The invention I claim is:

1. In an electric typewriter, a power assist mechanism for power operating a function control element in response to and at the rate of movement of a type action driven universal bar from a rest position, comprising,

means biasing said universal bar toward said rest position,

a driven shaft,

a control lever and an output lever rotatably mounted on said driven shaft,

a coiled spring coaxially wound around said driven shaft in a direction opposite the direction of rotation of said driven shaft and connected at one end to said control lever and at its other end to said output lever,

means biasing said output lever to a rest position, said coiled spring, with said universal bar and said output lever at rest position, being effectively disengaged from said driven shaft, and

means connectingsaid universal bar to said control lever whereby during movement of said universal bar from said rest position said coiled spring is caused to be coupled to, and to be driven by, said driven shaft at a rate of movement proportional to that of said universal bar movement and in turn to drive said output lever.

2. In an electric typewriter having, a type action, a universal bar movable in a first direction in response to power driven movement of said type action, and a function control link for operating an auxiliary mechanism in response to movement of said universal bar, the improvement comprising,

power assist means connected between said universal bar and said function control link for sensing, without resisting, movement of said universal bar in said first direction and, in response, power operating said control link during continued movement of said universal bar in said first direction, and at a rate of change of movement proportional to the movement of said universal bar in said first direction, said power assist means including a continuously rotatable shaft,

a control lever rotatably mounted on said continuously rotatable shaft articulately connected to said universal bar,

a power delivery lever rotatably mounted on said rotatable shaft and articulately connected to said function control link,

a wrap spring telescoping said continuously rotatable shaft, said wrap spring having a control end and power delivery end, said control end being connected to said control lever thereby to follow the movement of said universal bar in said first direction and during said movement to cause said wrap spring to frictionally engage said continuously rotatable shaft and be driven until said power delivery end has moved through substantially the same angular distance as said control end following cessation of universal bar movement in said first direction, said power delivery end of said wrap spring being connected to said power delivery lever,

and means biasing said power delivery lever and said universal bar in a second direction to a rest position.

Claims

1. In an electric typewriter, a power assist mechanism for power operating a function control element in response to and at the rate of movement of a type action driven universal bar from a rest position, comprising, means biasing said universal bar toward said rest position, a driven shaft, a control lever and an output lever rotatably mounted on said driven shaft, a coiled spring coaxially wound around said driven shaft in a direction opposite the direction of rotation of said driven shaft and connected at one end to said control lever and at its other end to said output lever, means biasing said output lever to a rest position, said coiled spring, with said universal bar and said output lever at rest position, being effectively disengaged from said driven shaft, and means connecting said universal bar to said control lever whereby during movement of said universal bar from said rest position said coiled spring is caused to be coupled to, and to be driven by, said driven shaft at a rate of movement proportional to that of said universal bar movement and in turn to drive said output lever.

2. In an electric typewriter having, a type action, a universal bar movable in a first direction in response to power driven movement of said type action, and a function control link for operating an auxiliary mechanism in response to movement of said universal bar, the improvement comprising, power assist means connected between said universal bar and said function control link for sensing, without resisting, movement of said universal bar in said first direction and, in response, power operating said control link during continued movement of said universal bar in said first direction, and at a rate of change of movement proportional to the movement of said universal bar in said first direction, said power assist means including a continuously rotatable shaft, a control lever rotatably mounted on said continuously rotatable shaft articulately connected to said universal bar, a power delivery lever rotatably mounted on said rotatable shaft and articulately connected to said function control link, a wrap spring telescoping said continuously rotatable shaft, said wrap spring having a control end and power delivery end, said control end being connected to said control lever thereby to follow the movement of said universal bar in said first direction and during said movement to cause said wrap spring to frictionally engage said continuously rotatable shaft and be driven until said power delivery end has moved through substantially the same angular distance as said control end following cessation of universal bar movement in said first direction, said power delivery end of said wrap spring being connected to Said power delivery lever, and means biasing said power delivery lever and said universal bar in a second direction to a rest position.