US3401783A

US3401783A - Proportional ribbon feed mechanism

Info

Publication number: US3401783A
Application number: US517551A
Authority: US
Inventors: James R Norwood; Joseph S Morgan
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1965-12-30
Filing date: 1965-12-30
Publication date: 1968-09-17
Anticipated expiration: 1985-09-17
Also published as: DE1561238A1; DE1561238B2; FR1506088A; DE1561238C3; GB1139060A; GB1128649A

Description

Sept. 17, 1968 NORWOOD ET AL 3,401,783

PROPORTIONAL RIBBON FEED MECHANISM 2 Sheets-Sheet 1 Filed Dec. so, 1965 FORWARD ESCAPEMENT DIRECTION INVENTORS.

JAMES R. NORWOOD JOSEPH S. MORGAN I BY W9 b. v

ATTORNEY.

United States Patent "ice 3,401,783 PROPORTIONAL RIBBON FEED MECHANISM James R. Norwood and Joseph S. Morgan, Lexington,

Ky., assignors to International Business Machines Corporation, Armonk, N.Y., a corporation of New York Filed Dec. 30, 1965, Ser. No. 517,551 11 Claims. (Cl. 197-151) ABSTRACT OF THE DISCLOSURE A ribbon feed mechanism for a proportional escapement typewriter which incrementally feeds printing ribbon by lengths proportional to the widths of the printed characters is disclosed. The mechanism comprises a drive shaft which is interconnected by a one way clutch to ribbon changing operation required during typing. Also the shaft and is moved in the overrunning direction of the one way clutch to an initial position in response to movement of the typewriter escapement apparatus. Later in the cycle the sensing member is driven back to its home position in the driving direction of the overrunning clutch to advance the ribbon.

The present invention relates generally to ribbon feed mechanism for business machines and more particularly to apparatus employed with a single element proportional escapement typewriter for feeding one use ribbon in accordance with the widths of the characters being printed.

A single element typewriter where the print element moves with respect to a stationary printing platen otters many and significant advantages with respect to more conventional typebar typewriters. The print element is easily removed and replaced so that the type style or font is readily changed. The mass and bulk of the movable carrier mounting the print element and associated ribbon feed mechanism are substantially reduced when compared with the mass and bulk of the conventional movable printing platen. A complete description of such a single element typewriter is found in the IBM Customer Engineering Series 72 Instruction Manual, Form 241- 5032-0, copyright 1961, and available from International Business Machines Corporation, Armonk, N.Y.

It has also been proposed to provide a single element typewriter with proportional escapement apparatus whereby the interchangeable print element is moved through various escapement distances in accordance with the widths of the characters selected by the typist. This escapement apparatus may comprise a pin wheel carrying a plurality of settable pins which, in combination with adjustable pitch changing means, is adapted to limit the rotary movement imparted to a lead screw by a constant torque device. The lead screw has a driving connection with the movable carrier that pivotally mounts a rocker assembly. The rocker assembly in turn carries the single print element. In one constructed embodiment of such a proportional escapement typewriter, a character may have a width of from three to nine escapement units and there are three selectable pitches. Thus, the carrier, rocker :assembly and single print element may move through any one of twenty-one possible escapement distances depending on the pitch setting of the machine and the character selected. A single element proportional escapement typewriter of this type isdescribed and claimed in co-pending application Ser. No. 311,373, entitled, Proportional Escapement Apparatus for a Single Element Typewriter, filed Sept. 25, 1963, and assigned to the assignee of the present invention. This application has now issued as US. Patent No. 3,346,086.

Such a single element proportional escapment typewriter is capable of producing copy which closely simu- 3,401,783 Patented Sept. 17, 1968 lates printed material. A one use ribbon, such as a carbon ribbon, which is fed once through the typewriter and discarded is normally employed to obtain printing of the highest quality. Carbon ribbons are relatively expensive supply items and it is desirable to limit the unused areas of the ribbon to a minimum. Because the ribbon feed mechanism is mounted on the movable carrier for th single print element, there is only limited space available for the ribbon. It is necessary to make maximum use of the ribbon provided in order to limit the number of ribbon changing operations required during typing. Also the ribbon changing operation, which involves the removal of the used ribbon :and the threading of a new ribbon, should be a clean operation capable of being quickly completed with a minimum of inconvenience on the part of the typist.

Accordingly, it is the primary or ultimate object of the present invention to provide a ribbon feed mechanism wherein the ribbon is advanced in proportion to the width of the character being typed. Maximum use is made of the available printing area on the ribbon which increases character yield and reduces both the frequency with which the ribbon must be changed and the overall cost of the typing operation.

Another object of the invention is the provision of a proportional ribbon feed mechanism for a proportional escapement single element typewriter wherein means are provided for inhibiting or preventing feeding of the ribbon during carrier return, tabulation, backspace and no-print operations. In these operations the carrier, rocker assembly and single print element move in the forward escapement or backspace direction but printing is not accomplished.

A further object of the invention is the provision of an improved arrangement for attaching the leader of a new supply spool of ribbon to a take up assembly as well as an improved system for removing and disposing of the used ribbon. A ribbon changing operation can be accomplished with a minimum of inconvenience, time and effort on the part of the typist.

Still a further object of this invention is to provide a proportional ribbon feed mechanism having the characteristics described above which is extremely simple in construction and operation. The ribbon feed mechanism is highly reliable and can be produced at low cost.

Briefly, the present invention provides a proportional escapement ribbon feed mechanism wherein a ribbon feed sensing arm is moved from a home position to an initial position via an engaged positioning clutch in exact accordance with the escapement movement of the carrier, rocker assembly and single print element. The positioning clutch is then disengaged to isolate the proportional ribbon feed mechanism from the escapement assembly. A ribbon feed driving arm is driven through a predetermined distance and engages the ribbon feed sensing arm. The ribbon feed sensing arm moves through a distance regulated by its initial position and this movement is transferred by way of a driving clutch to ribbon advancing apparatus which feeds the ribbon longitudinally in exact accordance with the width of the previously printed character. The driving clutch is disengaged during movement of the ribbon feed sensing arm from its home to its initial position. Means are also provided for disengaging the positioning clutch during certain functions and other operations when the carrier, rocker assembly and single print element move but characters are not printed In this manner the ribbon feed sensing arm is not moved to an initial position, where it is adapted to be engaged and driven by the ribbon feed driving arm.

The take up mechanism for the used ribbon comprises a slotted hub having a pair of cars and a take up plate removably mounted on the hub. When the plate is on the hub, the ears are biased or sprung outwardy from each other and their normal positions. Ribbon is wound about the ears and supported by the plate. To remove the ribbon, the plate is lifted from the slotted hub and the ears collapse to their initial positions. This permits the used ribbon to be removed with the plate and it is only necessary to turn the plate over and the ribbon will fall therefrom into a waste or other receptacle.

The foregoing and other objects and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawing.

In the drawing:

FIGURE 1 is an exploded perspective view of proportional ribbon feed mechanism for a single element typewriter for feeding one use ribbon in accordance with the widths of characters being printed as seen from the rear of the typewriter and constructed in accordance with the teachings of the present invention:

FIGURE 2 is side sectional view taken along the section line II-II of FIGURE 1;

FIGURES 3 and 4 are plan views taken along the section lines III-III and IV-IV, respectively, of FIGURE 2;

FIGURE 5 is a plan elevation view showing particularly the latching system and the mechanism for maintaining the positioning clutch engaged; and

FIGURE 6 is a series of graphs illustrating the timing involved in the operation of various portions of the proportional ribbon feed mechanism.

Referring now to the drawing, there is shown proportional ribbon feed mechanism constructed and operated in accordance with the teachings of this invention. This mechanism is generally mounted on a movable carrier, not shown, that pivotally carries a rocker assembly. A single print element is mounted for rotational and tilting movements on the rocker assembly. The carrier, and all apparatus carried thereby including the proportional ribbon feed mechanism, is mounted for movement in the forward escapement and backspace direction in front of a relatively stationary printing platen. This apparatus, other than the proportionl ribbon feed mechanism, will not be further described in the present specification. However, it is fully shown and described in the above identified instruction manual and Patent 3,346,086 to which reference should be made for a complete description of the basic single element proportional escapement typewriter. For reference purposes the forward escapement direction is represented by arrow 10 in FIGURE 1 of the drawing.

A supply spool 11 of a One use typewriter ribbon 12 is wound about an annular hub 13. The supply spool rests on a supply plate or tray 14 having a projection 15 which extends loosely into the center opening of the annular hub 13. Ribbon is drawn from the supply spool 11 and is guided by a pair of ribbon lift guides, not shown, in a longitudinal path of travel adjacent the printing platen and disposed between the printing platen and the single print element. Ribbon lift apparatus, also not shown, is connected with the spaced ribbon guides and is operative to raise the ribbon into printing position during each nor-mal character printing operation. Ribbon gudes and ribbon lift apparatus of a type which may be employed are fully disclosed in the above identified instruction manual and US. Patents 2,902,136 and 2,919,008, which are also assigned to the assignee of the present invention.

After leaving the ribbon guides, the ribbon passes between a pair of ribbon drive rolls 17 and 18' to a ribbon take up assembly comprising a take up hub 19 and a take up plate 20 where the used ribbon is wound in a spool to be discarded at a later time. The particular construction and cooperation of the take up hub 19 and take up plate 20 which allow a ribbon change operation to be completed with a minimum of time, effort and inconvenience will be considered in detail in the following portions of the specification.

The drive roll 17 is carried by a pivoted carrier 21 and is spring biased against the ribbon and drive roll 18. The flanged drive roll 18 is mounted on shaft 22 and is driven in a counterclockwise direction by

gears

23, 24 and 25. The gear 25 is formed with an integral axially extending annular hub 26 (see FIGURE 2 of the drawing) which is loosely received over the upper end of a vertical drive shaft 27. Received over the hub 26 and attached thereto by press fitting or other convenient attachment means is a pulley 28 having a semicircular groove about the periphery thereof.

Extending about the pulley 28 and a similar pulley 29 located on a shaft mounting the take up hub 19 is a continuous garter spring 30. Whenever a counterclockwise rotational movement is imparted to the gear 25, the ribbon drive roll 18 is rotated to advance a length of ribbon corresponding to the rotational movement of the gear. Also, the take up hub 19 and attached take up plate 20 are rotated in the counterclockwise direction. The pulley 28 is larger than the pulley 29 and therefore transmits proportionally larger angular rotation to the latter pulley. Slippage occurs between the pulleys and the garter spring and the amount of slippage increases as the diameter of the take up spool of used ribbon increases. This slippage insures the used ribbon is tightly wound on the take up spool.

Attached to the vertical drive shaft 27 by a set screw 31 and located below the gear 25 and pully 28 is an elongated annular collar 32. Received over the upper end of the collar 32 and the lower end of the gear hub 26 is a clutch spring 33 which provides a one way driving clutch for the proportional ribbon feed mechanism. The convolutions of the clutch spring 33 are wound in such a manner and direction that when a counterclockwise rotation is imparted to the vertical drive shaft 27, a similar rotational movement is transmitted to the gear hub 26, pulley 28 and gear 25. This causes the ribbon to be advanced and wound on the take up spool. However, when the vertical drive shaft 27 is rotated in the opposite or clockwise rotational direction, the turns of the clutch spring 33 unwind slightly to release gear hub 26. The gear 25 and pulley 28 do not move and no motion is imparted to the one use ribbon when the vertical drive shaft 27 moves clockwise.

Mounted on and carried by the elongated annular collar 32 is a laterally projecting ribbon feed sensing arm 35. As shown in FIGURE 1 of the drawing, this sensing arm is adapted to be engaged and driven in the counterclockwise direction by the upper end of a ribbon feed driving arm 36. The amount of counterclockwise ribbon feeding movement imparted to the ribbon feed sensing arm 35 depends on its initial setting prior to the pivoting movement of the ribbon feed driving arm 36. The sensing arm 35 is initially located at a home position and is moved in a clockwise direction to an initial position in exact accordance with the escapement movement experienced by the single print element, rocker assembly and movable carrier. This clockwise movement of the ribbon feed sensing arm 35 is accomplished by means of an engaged positioning clutch generally designated by the reference numeral 37. The home position is defined as the position of the ribbon feed sensing arm 35 prior to an escapement operation and prior to its being driven clockwise by engaged positioning clutch 37 while the initial position is defined as the position of the ribbon feed sensing arm 35 after it has been driven clockwise via positioning clutch but before it is driven counterclockwise back toward the home position. Rotation is not transmitted to the gear 25 and pully 28 during movement of the ribbon feed sensing arm 35 to its initial position due to the one way driving connection provided by clutch spring 33.

The positioning clutch 37 comprises an annular generally T-shaped upper clutching member 39 which is loosely received on the vertical drive shaft 27. A guide pin 40 projects through a pair of slots 41 in the upper clutching member 39 so that the latter is guided for limited vertical movement with respect to the vertical drive shaft. The enlarged lower end of the upper clutching member is machined or otherwise formed .to provide an accurately contoured cam 42 having a pair of circumferentially spaced and radially extending

camming projections

43 and 44. The function and use of the camming projections to prevent feeding of the ribbon during certain typewriter operations where escapement movements of the carrier take place but no printing is accomplished will be hereinafter more fully explained. The lower edge of the upper clutching member 39 is provided with a ring of downwardly facing clutching teeth 45.

An annular lower clutching member 48 is attached by a set screw 49 to a mounting hub 50 located at the bottom of the vertical drive shaft 27. The mounting hub 50 is closely received or journalled on the drive shaft and the lower portion of the mounting hub is formed to provide an escapement sensing pinion 51. The lower clutching member 48 has a plurality of circumferentially spaced and axially extending slots 53 therein. Received in each of these slots 53 is a generally L-shaped drive tooth 54 having a tapered upper edge which projects upwardly from the lower clutching member. The drive teeth 54 are radially constrained in their slots 53 by means of a retaining ring 54'. An annular spider type spring 55 is mounted on the hub 50 directly below the lower clutching member 48 and has circumferentially extending spring arms 56 which individually and resiliently urge the L-shaped drive teeth 54 to extended operative positions.

A coil spring 57 is disposed between the upper and lower clutching

members

39 and 43 and tends to maintain the upper clutching member 39 in its elevated or raised position so that the positioning clutch 37 is disengaged. However, when the upper clutching member 39 is forced down, the teeth 45 mesh with drive teeth 54 and the positioning clutch is engaged. The drive teeth 54 are angularly disposed relative to the ring of teeth 45 so that any initial rotational movement required to rotationally engage the teeth of the clutch is minimized. This is accomplished by separating the drive teeth 54 from each other by a distance equal to a multiple of the space occupied by one of the teeth 45 plus an increment which is less than the space occupied by one of the teeth on the upper clutching member 39. Therefore, the maximum rotational movement required to drivingly engage the teeth of the positioning clutch 37 is much less than the distance occupied by one of the teeth 45 on the upper clutching member 39. This arrangement is enhanced by the use of the spider type spring 55 which permits individual vertical movement of the drive teeth 54 and positive vertical engagement of the positioning clutch at all times.

The escapement sensing pinion 51 meshes with a rack 58 which is stationarily mounted on the frame of the typewriter. All of the mechanism so far described, with the exception of stationary rack 58, is mounted on and movable with the carrier rocker assembly and single print element. Thus, when the carrier is moved through an escapement distance corresponding to the width of a selected character, a proportional rotation of pinion 51 will occur. This pinion directly senses any movement of the carrier whether in the forward escapement or backspace direction. When the positioning clutch 37 is engaged, the rotational movements of the escapement sensing pinion 51 are transmitted through the lower and upper clutching

members

48 and 39 to drive the vertical shaft 27 and position the ribbon feed sensing arm 35. The positioning clutch 37 is held engaged only during the time interval when the carrier is experiencing an escapement movement to position the ribbon feed sensing arm 35 at its initial position. The positioning clutch is disengaged when the ribbon feed driving arm 36 moves forward and drives the ribbon feed sensing arm 35 to advance the ribbon so that the counterclockwise rotation of the vertical shaft 27 is not reflected to and does not attempt to move the carrier, rocker assembly and single print element in the backspace direction.

A pin 60 carried by a bellcrank 59 engages the top surface of the upper clutching member 39 and controls the engagement and disengagement of the positioning clutch 37. The bellcrank 59 is pivotally mounted on a pin 62 'along with a transfer lever 61. The bellcrank 59 and transfer lever 61 are joined by a spring 63 which is appreciably stronger than the coil spring 57 and these members normally move together as a unit. A slotted latch member 64 is pivoted on a pin 65 and is adapted to engage a latch car 66 of the transfer lever 61. When the latch member 64 engages the latch ear 66 of the transfer lever 61, the bellcrank 59 and pin 60 are so positioned that the coil 57 is compressed and the positioning clutch 37 is engaged. The location of the various parts at this time is shown in FIGURES 1 and 5 of the drawing. The positioning clutch 37 is engaged even though it may appear the upper and lower clutching

members

39 and 48 are separated because of the exploded nature of FIGURE 1. However, when the latch member 64 is pivoted clockwise and moves from latch ear 66, the transfer lever 61 and bellcrank 59 rotate clockwise about pivot pin 62 and the clutch pin 60 is permitted to move upward. The coil spring 57 separates the clutching

members

39 and 48 and the positioning clutch 37 is quickly disengaged.

The state of the positioning clutch 37 is controlled by slotted latch member 64 whose condition is in turn determined by multi-armed clutch release lever 68. The clutch release lever 68 is pivoted for swinging movement about vertical pivot pin 69 and biased counterclockwise by spring 95. A first arm 70 of this release lever is connected by a pinto the latch member 64. A second or middle arm 71 is adapted to be engaged at certain times by the

camming projections

43 and 44 carried by the upper clutching member 39. A third vertically extending arm 72 is positioned behind a pin 73 projecting downwardly from the lower end of the ribbon feed driving arm 36.

The ribbon feed driving arm 36 is pivotally mounted at 74 and has a cam follower portion 75 which is biased into engagement with the surface of ribbon feed cam 76 by spring 96. The ribbon feed cam 76 is keyed or otherwise attached to a print shaft 77 that rotates through one complete revolution during each printing cycle of the typewriter. Other cams on the print shaft 77 regulate ribbon lift, detenting of the single print element and pivotal movement of the rocker assembly and single print element toward the printing platen. The arrangement is such that all operations are performed in a synchronized and accurately timed manner.

Considering the operation of the above described proportional ribbon feed mechanism, reference should be made to FIGURE 6 of the drawing wherein the displacement of various parts relative to the angular position of the print shaft 77 is graphically depicted. The positions of the upper clutching member 39, latch member 64, ribbon feed sensing arm 35 and ribbon feed driving arm 36 are illustrated by the curves 80-83, respectively. At the beginning of a printing operation the mechanism is as shown in FIGURE 1 of the drawing with the positioning clutch 37 engaged and interconnecting the escapement sensing pinion 51 with the vertical drive shaft 27 and the ribbon feed sensing arm 35. The typist selects a character by depressing a keylever at the keyboard of the typewriter. The single print element is rotated and tilted as required to bring the selected character to the printing position in front of the printing platen. Then the rocker assembly is pivoted forward to effect printing of the selected character.

After printing has been completed, it is necessary to move the carrier, rocker assembly and single print element in the forward escapement direction as indicated by arrow 10 in accordance with the width of the printed haracter. The pinion 51 senses this escapement movement and positions the ribbon feed sensing arm 35 accordingly since the positioning clutch 37 is engaged at this time. The possible initial positions of the ribbon feed sensing arm 35 are shown by the alternate broken curves 82 in the graph of FIGURE 6 of the drawings. As previously explained, the gear and pulley 23 are not driven to feed the one use ribbon 12 during positioning movement of the ribbon feed sensing arm due to the one way drive connection defined by clutch spring 33.

After the ribbon feed sensing arm 35 has been rotated clockwise from the home position via positioning clutch 37 and has been located in its initial position in accordance with the width of the previously printed character, the ribbon feed driving arm 36 begins to move forward as the ribbon feed cam 76 and print shaft 77 continue to rotate. The pin 73 carried by the ribbon feed driving arm 36 engages arm 72 of release lever 68 and swings the latter clockwise about its pivot pin 69. The first arm 70 of the release lever 68 moves the slotted latch member 64 whereby this member moves out of engagement with the latch ear 66 of transfer lever 61. The coil spring 57 is then operative to move the upper clutching member 39 vertically and the positioning clutch 37 is disengaged.

With the positioning clutch 37 disengaged, the ribbon feed driving arm 36 advances the ribbon feed sensing arm 35 counterclockwise from its initial position to the home position. The gear 25 and pulley 28 are driven through clutch spring 33 to feed the one use ribbon 12 in accordance wtih the width of the previously printed character. A length of used ribbon corresponding to the width of the previously printed character is moved from the printing point so that a length of unused ribbon is disposed at this point.

During the succeeding printing operation, the single print element and rocker assembly are thrown forward to cause printing of the next selected character and this is represented by the vertical line 86 in FIGURE 6 of the drawing. A resetting lever 87 attached to the rocker assembly engages the transfer lever 61 and pivots the combined transfer lever 61 and bellcrank 59 assembly as printing occurs so that pin 60 moves the upper clutching member 39 downward to engage the positioning clutch 37. Spring 63 provides a lost motion connection between the bellcrank 59 and the transfer lever 61 which permits the transfer lever 61 to continue to move after the pin 60 has engaged the positioning clutch 37 if the resetting lever 87 has been overthrown for any reason. As the clutch release lever 68 returns to its initial position, it

engages and pivots latch member 64 so the tip thereof moves over the latch ear 66 of the transfer lever 61 and the apparatus is ready for the next cycle of operation. It should be understood that the graphs in FIGURE 6 of the drawing depict the operation of the apparatus under maximum speed conditions where escapement movement of the carrier, rocker assembly and single print element takes place while another character is being selected for printing. However, the general series of operations including printing of a selected character, proportional escapement of the carrier and proportional advancement of the one use ribbon are completed in the order set forth regardless of the speed of typing.

The slippage occurring during engagement and disengagernen-t of the clutch spring 33 and the positioning clutch 37 can be of a magnitude sufficient to cause underfeeding of the ribbon. To compensate for this condition, a stop arm 89 of spring steel is mounted from the bottom of ribbon supply plate or tray 14 and is positioned to be deflected slightly by the ribbon feed sensing arm 35 when the latter is driven counterclockwise to the furthest extent by the ribbon feed driving arm 36. As the ribbon feed driving arm 36 returns to its starting position, the energy stored in the flexible stop arm 89 moves the ribbon feed sensing arm 35 back through a small angular distance.

This acts to add a constant increment of ribbon to the amount of ribbon fed during each ribbon feeding operation. This compensates for any loss of rotational movement in the driving and positioning clutches and insures that sufficient ribbon is fed during each advance of the ribbon.

There are a number of typewriter operations where the carrier, rocker assembly and single print element move in the forward escapement or backspace direction but printing is not accomplished. It is desirable that ribbon feed be inhibited during these operations to prevent the waste of large amounts of ribbon. When a backspace or carrier return operation is initiated, the proportional ribbon feed mechanism is in the position shown in FIGURE 1 of the drawing with the positioning clutch 37 engaged. The movement of the carrier in the backspace direction causes the escapement sensing pinion 51 and the vertical shaft 27 to rotate counterclockwise. This tends to advance the one use ribbon since gear 25 and pulley 28 are driven via clutch spring 33. However, the driving movement continues only until the camming projection 43 carried by upper clutching member 39 engages arm 71 and pivots clutch release lever 68. The positioning clutch 37 is immediately disengaged and no ribbon is fed during the remainder of the backspace or carrier return operation. The positioning clutch 37 is engaged and latched during the next printing operation.

A tabulation operation involves moving the carrier, rocker assembly and single print element in the forward escapement direction until the next set tab stop is sensed. The tabulation movement will cause the vertical drive shaft 27 to turn in the clockwise direction until the camming projection 44 carried by the upper clutching member 39 engages arm 71 and pivots clutch release lever 68. The positioning clutch 37 is released and no further movement of the ribbon feed sensing arm 35 occurs during the remainder of the tabulation operation. During the first printing operation after the tabulation operation, the ribbon feed driving arm 36 moves the ribbon feed sensing arm 35 to its home position and the ribbon is advanced by a distance corresponding to the angular position of camming projection 44. This projection is disposed so that a forward escapement movement slightly greater than that required in printing the widest character at the largest pitch setting is needed before the camming projection 44 is operative to engage and move release lever 68. Ribbon feed is also inhibited by this apparatus during other extended forward escapement movements of the carrier which do not involve printing, such as a repetitive series of spacebar operations.

A no print operation for a single element typewriter occurs when the rocker assembly and single print element are thrown toward the printing platen with insuificient force to cause printing. Character selection and escapement operations are performed in the conventional manner. The print shaft 77 rotates during each no print operation to oscillate the ribbon feed driving arm 36. However, the rocker assembly does not pivot sufliciently to allow resetting lever 87 to move transfer lever 61 to a position Where it is engaged and latched by latch member 64. The positioning clutch 37 is not engaged under these conditions and the ribbon feed sensing arm 35 is not displaced from its home position. No ribbon is fed during the first printing operation after a series of no print operations have been completed.

As mentioned above, one important aspect of the present invention is the provision of an improved arrangement for attaching the leader of a new supply spool of ribbon to a take up assembly as well as an improved system for removing and disposing of the used ribbon. The take up assembly comprises the slotted take up hub 19 having a pair of ears 91 and the take up plate 20 provided with a center post 92. Located at the bottom of the center post are apertures 93 which receive the cars 91 of'the take up hub 19. When the take up plate 20 is mounted on the 9 slotted take up hub 19, the center post 92 of the take up plate wedges apart or slightly separates the ears 91 from their initial positions. When loading a ribbon, the leader is positioned and clamped between the post 92 on the take up plate and one of the ears 91 of the take up hub 19. After the loading operation, used ribbon is wound about the cars 91 and post 92 to form a spool which is supported on the take up plate 20. To remove the used ribbon, the typist merely lifts the take up plate 20 from the take up hub 19. During the upward movement of the plate, the ears 91 return inwardly to their initial positions and this tends to reduce the friction and resultant force required to remove the take up plate from the typewriter. Also, the spool of used ribbon is now loosely supported on the take up plate and can be discarded by simply turning the take up plate over and letting the used ribbon fall into a waste basket or similar receptacle. This ribbon changing operation is characterized by its extreme simplicity and cleanliness when compared to those encountered when using prior art ribbon feed mechanisms.

It should now be apparent that the objects initially set forth have been accomplished. Of particular importance is the provision of a simplified ribbon feed mechanism for advancing a ribbon, such as a one use carbon ribbon, in according with the widths of characters being typed. Also, means are provided for inhibiting ribbon feed during certain typewriter operations when the carrier, rocker assembly and print element move in the forward escapement or backspace direction but no printing is accomplished. The mechanism as disclosed includes a clutch spring and a ratchet clutch but other types of clutches having the same general operating characteristics can be substituted therefor. Also, additional means may be provided for disengaging the positioning clutch to prevent initial setting of the ribbon feed sensing arm and feeding of the ribbon; This additional apparatus would be responsive to an operation other than those set forth herein, such as movement of a control lever to a position associated with the cutting of stencils.

What is claimed is:

1. A proportional ribbon feed mechanism for a business machine having a movable print element for feeding ribbon in accordance with the widths of the printed characters comprising:

a ribbon advancing roll for feeding the ribbon;

means to drive said ribbon advancing roll;

said means to drive comprising a drive shaft;

a one way driving clutch interconnecting said drive shaft and said ribbon advancing roll;

means for sensing escapement movements of said movable print element;

a positioning clutch interconnecting said sensing means and said drive shaft;

a ribbon feed sensing arm carried by and movable in one rotational direction with said shaft from a home position to an initial position in response to said sensing means when said positioning clutch is engaged, said one rotational direction being in the overrunning direction of said one way driving clutch;

means to disengage said positioning clutch after said ribbon feed sensing arm is located in said initial position; and

means to drive said ribbon feed sensing arm to said home position in the other rotational direction to turn said drive shaft and drive said ribbon advancing roll through said one way driving clutch to advance the ribbon in proportion to the escapement movement of said print element.

2. A proportional ribbon feed mechanism for a business machine having a movable member for feeding ribbon in accordance with the widths of the printed characters comprising:

ribbon advancing means for feeding the ribbon;

means to drive said ribbon advancing means;

said means to drive comprising a drive member;

a one way driving clutch interconnecting said drive member with said ribbon advancing means;

means for sensing escapement movements of said movable member;

a positioning clutch interconnecting said sensing means with said drive member;

said sensing means causing movement of said drive member in one direction from a home position to an initial position in response to an escapement movement of said movable member when said positioning clutch is engaged, said one direction being in the overrunning direction of said one way driving clutch;

means to disengage said positioning clutch after said ribbon feed means is located in said initial position; and

means to move said drive member to said home position in the other direction to drive said ribbon advancing means through said one way driving clutch to advance the ribbon in proportion to the escapement movement of said movable member.

3. Apparatus according to claim 2 further characterized by:

said one way driving clutch and said positioning clutch being disposed at the opposite ends of said drive member; and

said means to move being located between said one way driving clutch and said positioning clutch.

4. Apparatus according to claim 2 further characterized by:

means to re-engage said positioning clutch after said ribbon advancing means has fed said ribbon in preparation for another cycle of operation of said business machine.

5. Apparatus according to claim 2 further characterized by:

said movable member comprising a carrier, a rocker assembly pivotally mounted on said carrier and a print element on said rocker assembly; and

said proportional ribbon feed mechanism being carried by and movable with said carrier.

6. Apparatus according to claim 5 further characterized by:

means to re-engage said positioning clutch after said ribbon advancing means has fed said ribbon in preparation for another cycle of operation of said business machine; and

said means to re-engage being carried by said rocker assembly.

7. A proportional ribbon feed mechanism for a business machine having a movable member for feeding ribbon in accordance with the widths of the printed characters comprising:

ribbon advancing means for feeding the ribbon;

means to drive said ribbon advancing means;

said means to drive comprising a drive member;

a driving clutch operative in one direction interconnecting said drive member with said ribbon advancing means;

means for sensing escapement movements of said mov able member;

a positioning clutch operative in the other direction interconnecting said sensing means with said drive member;

said sensing means causing movement of said drive member in said other direction from a home position to an initial position in response to escapement movement of said movable member when said positioning clutch is engaged; and

means to move said drive member to said home position in said one direction to drive said ribbon advancing means through said driving clutch to advance the ribbon in proportion to the escapement movement of said movable member.

8. Apparatus according to claim 7 further character ized by:

means to disengage said positioning clutch; and means to actuate said means to disengage in response to predetermined movement of said movable member in at least one direction of travel. 9. Apparatus according to claim 8 further characterized by:

means to disengage said positioning clutch; and means to actuate said means to disengage each printing cycle of said business machine prior to the movement of said drive member to said home position. 10. Apparatus according to claim 9 further characterized by:

additional means to actuate said means to disengage;

and said additional means to actuate causing operation of said means to disengage in response to a predetermined movement of said movable member in at least one direction of travel. 11. Apparatus according to claim 10 further characterized by:

said additional means to actuate comprises a cam mem ber rotatable with said drive member; and

said cam member having at least one actuating camming projection disposed on the periphery thereof.

References Cited UNITED STATES PATENTS Thompson 197-172 Webster 24274 Dodge 197-84 Hausman 197-84 Toggenburger 197-151 Schroder 197-151 Page 197-151 Kizak 197172 Roller et a1 19715l Germany.

ROBERT E. PULFREY, Primary Examiner.

E. T. WRIGHT, Assistant Examiner.