US2752026A - Ribbon vibrating mechanism for typewriters and like machines - Google Patents

Description

June 26, 1956 c. B. LETTERMAN RIBBON VIBRATING MECHANISM FOR TYPEWRITERS AND LIKE MACHINES Filed Dec. 24, 1952 IN VEN TOR HARLES B. LE77'ERMAN Will;

A T TORNEV RIBBQN VIBRATING DIECHANISM FOR TYPE- WRITERS AND LIKE MACHINES Charles B. Letterman, West Hartford, Conn., assignor to Underwood Corporation, New York, N. Y., a corporation of Delaware Application December 24, 1952, Serial No. 327,721

1 Claim. (Cl. 197-157) This invention relates to bichrome ribbon vibrating mechanisms for typewriting machines and the like, selectively conditionable to vibrate the ribbon for use of one or the other color band or for stencil typing.

An object of the invention is to provide an improved ribbon-vibrator operating mechanism operative to raise the ribbon to the typing or printing line quickly and with great accuracy, avoiding any possibility of overthrow, chatter or rebound of the ribbon, a major cause of faulty type impressions.

A further object is to provide a simple and reliably operative bichrome ribbon vibrating mechanism particularly suited for lightweight, economical portable typewriters, and yet dependably operable to vibrate the ribbon to typing position without risk of any bleeding tendency, that is, type impressions partly of the color from the other ribbon band.

Other objects and advantages will be in part obvious and in part pointed out as the following description of one embodiment which the invention may assume in practice proceeds.

In the drawings:

Figure 1 is a side elevational view, partly broken away and in central section, of a typewriter embodying the invention, the ribbon vibrating mechanism being set for typing by the upper or black band and in quiescent condition,

Figure 2 is a fragmentary view similar to Figure 1 but showing the ribbon vibrating mechanism in the operated condition of typing by the upper ribbon color band, and

Figure 3 is a view like Figure 2 but in the operated condition of typing in the lower or red color band.

Referring to Figure 1, the type action system herein shown by way of example, comprises a series of key levers 5 fulcrumed on a common axis not shown, substantially rearward of the typewriter and which at their forward ends carry keys 6 arranged in the usual four banks or key rows, of which two are shown. Each key lever has a pin 7 projecting therefrom for cooperation with a slot 8 of a bell crank sub-lever 9 fulcrumed on a rod 10 extending transversely of the typewriter and supported on the mainframe side members 11, of which one is shown. An arm of the sub-lever 9 is connected by a pull link 12 to a type bar 13 pivotally supported on a type bar segment 14. The segment 14 is carried on a shift frame 15 by which the segment is case shiftable to present one or the other of the upper and lower case type to the typing line, upon actuating the type bar to strike a platen 16. The type bars 13 are guided laterally to the typing point by the usual type guide 17 carried on the segment.

For actuating the ribbon vibrating mechanism, upon operating each type bar, a universal bar 18 is provided, the same having arms 20 at its opposite ends pivoted on but rockable independently of fulcrum rod 10. The arms 20 are each bent inwardly to form lugs to which a sheet metal plate or bar 21, preferably of flat spring stock, is secured. At its forward longitudinal edge, bar 21 is nited States Patent Patented June 26, 1956 flanged over for lengthwise stiffening, and at its rearward marginal portion, substantially overhung from the pivot rod 10, is sheared or slit transversely at intervals conforming to the spacing of the key levers 5 to form a series of independent spring fingers 22, each curved at its end to afiord a rounded contact for the respective key levers. The fingers 22 are of different lengths as measured from the fulcrum axis 10, there being four groups of fingers, each group of different length and each group of fingers being associated with only the key levers of a certain key bank. It is usual in typewriters that all the type keys have a uniform dip on being depressed, and by providing different lengths for the fingers 22 a uniform stroke is imparted to the universal bar 18 by all the type actions notwithstanding the different lengths of the key levers. In addition to having each of the spring fingers 22 independently yieldable, it is desirable to have each finger bendable so that its end may be adjusted slightly with respect to the associated key lever 5 to either contact same or afford a slight clearance according to the requirements of each type action to raise the ribbon, by means hereinafter described, to accurately overlie the typing line. Spring means not shown tends to rock the universal bar 18 counterclockwise as viewed in Figure 1, pressing the fingers 22 toward the key levers 5, contact of one or more fingers with the respective key levers determining the normal or inactive position of the universal bar.

The member 20 at the rightward end of the universal bar, Figure l, is extended laterally and upwardly to provide a C-shaped arm or lever 23 defining an arcuate slot 24 open at 25. A ribbon vibrator 26 having the usual ribbon guides 27 at its upper end is mounted for up-anddown reciprocatory movement on the segment-shift frame unit 14, 15 by means including lugs 28 slidably embracing an upright member of the type guide 17. At its lowermost end the ribbon vibrator 26 is pivotally connected at 30 to an arm 31 secured to a cross shaft 32 extending from the middle of the typewriter laterally through the right-hand mainframe side member 11 in which it is journalled. Arm 31 includes a downwardly projecting lug 33 having a sleeve of resilient or cushioning material thereon and engages a channel cross member 34 of the typewriter mainframe. The stop lug 33 thus determines the retracted or normal downward position of the ribbon vibrator 26, quietly arresting same in its retracting movement. The end of cross shaft 32 which projects through the side member 11 has an arm 36 secured thereto to which a selectively settable link 37 is pivotally connected at 38. The forward end of the settable link 37 has a pin 40 projecting laterally therefrom and cooperating in the arcuate slot 24 of the lever 23.

The link 37 is settable selectively to three positions, specifically to locate its pin 40 in the slot 24 at different distances from the axis 10, the settings, ranging from the bottom up, being respectively for the black ribbon band, secondly the medial position for stenciling, and the uppermost position, shown in dot-and-dash outline, being for vibrating the ribbon to the upper or red color band. In the medial position for stenciling, in which setting the ribbon vibrator is rendered inactive the pin 40 is opposite the slot opening 25 and therefore the link 37 receives no movement from the universal bar 18, the lever 23 merel oscillating idly.

The mechanism for selectively setting the link 37, as above described, comprises a setting lever 41 pivoted at 42 on the side member 11 and settable to three positions as defined by a spring-pressed detent device 43 cooperating with detent notches (not shown) in a flange 44 of the side member. The setting lever 41 is connected by a link 45 to a bell crank 46 pivoted at 47 to the side member, its other arm being connected by a link 48 to the settable link 37. It will be observed that the link 48 hangs from bell crank 46 and suspends the leftward portion of the settable link 37 in its three selected positions. The point of connection of the link 48 with the bell crank 46 is located with respect to the settable link 37 and the connecting point of link 48 thereto so that a minimum of angular movement of link 37 is required during its longitudinal movement in actuating the ribbon vibrator. The length of link 48, also, is ample to keep said angular movement at a practical minimum.

Insofar as the invention concerns ribbon overthrow prevention, only the two settings of the vibrating mechanism for bichrome selection need be considered, the stencil setting being an inactive condition of said mechanism. As to the alternative bichrome-selecting settings of link 37, it will be seen that the link pin 44) is adapted to engage one or another point on the lever 23, as shown respectively in Figures 2 and 3, and that said points are at different distances from the axis of said lever, namely the shaft 10. With the bichrome-selecting mechanism set for the upper color band, usually black, shown in full line in its quiescent condition in Figure 1, the link pin 40 is disposed on the lever 23 in a position relatively near the lever fulcrum and therefore a lesser movement will be imparted to the ribbon vibrator 26 as required to elevate the ribbon so that its upper color band is at the typing line, as 7 demonstrated in Figure 2. With the bichrome selecting mechanism set for the lower color band, usually red, as partly shown in dot-and-dash outline in-Figure -l, the link pin 40 is adapted to cooperate with a point on lever 23 that is a greater distance from the lever axis 10 and therefore a greater stroke is imparted to the link 37 and thence to the ribbon vibrator 26 as required, to elevate the ribbon so that its lower color band is brought to the typing line, as demonstrated in Figure 3.

To accurately arrest the ribbon vibrator 26 in its fully elevated position and thus prevent ribbon overthrow, in either setting of the bichrome-selecting mechanism, two stop devices are provided for arresting link 37. For the lesser throw of the vibrator for the upper or black band, Figure 2,,the stop device comprises a tongue 50 projecting from the link 37 to provide a stop face 51 adapted to engage an adjustable stop 52 rigidly mounted on the mainframe side member 11. For the greater throw of the ribbon for the lower or red band, Figure 3, the stop device comprises a laterally projecting prong 54 at the rightward end of link 37 providing a stop face 55 adapted to engage an adjustable stop element 56 on the side member 11. Each of the stops 52 and 56 may embody various constructions to afford adjustability, that shown being an eccentric, the slight rotation of which varies its position with respect to the stop face on link 37, its adjusted position being secured by tightening a screw shown. Each stop element 52, 56 is preferably of rigid or substantially non-yielding material so that accuracy of the full stroke arrest will be had over an appreciable period of service.

The provision of two stop devices arranged as shown to cooperate individually with the settable link 37 in its two bichrome selecting settings is of particular advantage. Each stop 52, 56 may be individually and accurately adjusted to perform its stopping function exactly as required, since each stop functions independently of the other and may therefore be regulated without concern as to the other. The particular association of the stops 52,

56 with the settable link 37 makes this feasible in that the'stop' device 56, 52 for the shorter throw of the mechanism is. rendered ineffective automatically by the shift of link 37 to its other setting where the bichrome mechanism is conditioned for the longer throw, as will be apparent from a comparison of Figures 2 and 3. A further advantage is in having a major part of the vibrating mechanism conveniently accessible at the side of the typewriter chassis where the more important elements of the mechanism may be adjusted or repaired with ease.

The dependable operation of the ribbon vibrating mechanism, particularly as to quickly arresting the ribbon in typing position without chattering, is aiforded by the limited yieldability of the universal-bar spring fingers 22. As the selected key lever 5 is initially operated its engagement with the corresponding spring finger 22 causes the latter to flex or tension slightly as it picks up the load of the ribbon vibrator and its operating mechanism, which flexing is maintained while the full throw of the vibrator is being completed. At the instant of completing the full throw of the vibrator either stop device 52 or 56 becomes effective as the link 37 abruptly engages the stop. At this point any tendency of the link 37 and associated mechanism to rebound is obviated by the stored-up tension in the flexed spring finger 22. That is, at the instant of arresting the ribbon vibrating mechanism the tension of the effective spring finger, transmitted through the universal bar 18, its associated lever 23 and via pin 40 to link 37, firmly presses said link against the eifective stop 52, 56 to avoid any chattering of the mechanism that may carry through to the ribbon at the instant of impact of the type and thus result in a blurred or bleeding type impression.

Having thus described the invention, what is claimed is: In a typewriter, in combination, a platen, a series of type bars operable against said platen to type at a printing point, key levers to operate said type bars, a ribbon vibrator holding a typewriter ribbon normally retired below a printing point, a universal bar having spring fingers whereby said key levers are adapted to operate it, an arm, a pivot axis for said arm, said arm pivotally rockable by the operations of said universal bar, a link having at one end an operative connection with said vibrator and about such connection being swingable' at its other and toward and away from the said pivot axis to link it to said arm at a greater or a lesser arms length from the said pivotaxis, whereby uniform rocking movements of said arm will cause greater or lesser-extent ribbonvibrating movements of said link and said vibrator, depending on the arms length at which said link is linked to saidarm, an adjustable stop to limit said vibrator to said greater-extent movement whenever said link is linked to said arm at said greater arms length, and an adjustable stop for cooperation with said link near the swingably settable end thereof to limit it to the said lesserextent movement, the said link having an abutment which is in cooperative range of said last stop only if it is linked with said arm at'the said lesser arms length, each spring finger having a position on the universal bar for its related key lever to efiect said limited lesser or greaterextent operation of the said link and after accomplishment of said operation to exert in a terminal portion of a key lever stroke a spring bias on said universal bar keep- "ing said link and the ribbon vibrator operated in the exact limit position.

References Cited in the file of this patent UNITED STATES PATENTS 990,917 Spiro May 2, 1911 1,165,941 Buschmann Dec. 28, 1915 2,178,688 'Helmond Nov. 7, 1939 FOREIGN PATENTS 381,472 Great Britain Oct. 6, 1932

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