US2857033A - Type bar actuating mechanism for typewriters - Google Patents

Description

A. DEMMEL 2,857,033

TYPE BAR ACTUATING MECHANISM FOR TYPEWRITERS Oct. 21, 1958 Filed Jan. 19. 1956 Amo'r. Dernme/ WMJW& fi

United States Patent TYPE BAR ACTUATING MECHANISM FOR TYPEWRITERS Anton Demmel, Wilhelmshaven, Germany, assignor to Olympia Werke AG., Wilhelmshaven, Germany Application January 19, 1956, Serial No. 560,185

Claims priority, application Germany February 26, 1955 2 Claims. (Cl. 197-28) The present invention relates to a type bar actuating mechanism for typewriters and is particularly designed for use with typewriters having a very low construction, i. e. those known as portables wherein the key levers are coupled to their respective type bars by means of connecting levers and draw-bars. In general, the connecting levers are each mounted for pivotal motion on an axis intermediate the ends of the lever thereby establishing two lever arms, one such arm being coupled to the associated key lever, and the other arm being pivotally connected at its outer end to one end of the draw-bar, the other end of the latter in turn being pivotally connected to one arm of the pivotally mounted type bar, the other armof the type bar carrying at its outer end the type which is caused to strike against the paper on the platen.

With type bar actuating assemblies of the kind abovereferred to, efforts have been made to impart to the type bar, during the last portion of its operating or striking stroke, the greatest possible acceleration in order that the type shall strike the paper on the platen with the highest possible velocity and momentum thereby assuring sharp and dark carbon copies even when several sheets of paper, or thick paper, is used. A secondary advantage inherent in high speed type bar actuation is that it enables a corresponding increase in typing speed.

In order to obtain a high striking velocity for the type bar it has been suggested in the past that means be provided for changing the transmission ratio of the connecting lever as a function of the change in lift imparted to the lever by depression of the key lever. However, so far as is known, the previous constructions have been limited to arrangements wherein it has been possible only to progressively shorten the effective length of that arm of the connecting lever at the side of the pivot axis connected to the key lever. The efiective length of the other arm of the connecting lever at the opposite side of the pivot axis and which is connected to the draw-bar remained constant. Due to the relatively slight maximum amplitude of key lever motion permissible in typewriters of the so-called low construction or portable kind, to bring the typebar from itsrest position into the striking position, the prior suggested arrangements for changing the transmission ratio of the lever system do not obtain the optimum strikingvelocity for the type bar to be accelerated. j

The principal object of the present invention is to provide an improved arrangement for increasing the velocity of the type bars with increasing displacement of the respectively associated key levers, and is characterized by the fact that the connecting levers between the key levers and type bars are mounted for rotation on an axis the position of which changes progressively in such manner that the distance between the instantaneous pivot axis of the lever and the point of connection to the keylever is progressively shortened, while the distance between the instantaneous pivotaxis of the connectinglever and the pointof connection to the draw-bar (which is in turn 2,857,033 Patented Oct. 21, 1958 coupled to the type bar) is simultaneously progressively lengthened. The net eficct is a compound or two-fold increase in the velocity of the type bar during its stroke. One such increase is due to the progressive increase in angular velocity of the connecting lever about its pivot axis and the other increase arises from the progressively increased rate of displacement at that outer end of the lever arm which is coupled to the draw-bar, for a given change in angular displacement of the lever about its axis.

A more specific object of the invention is to provide for a progressive shift in the axis of rotation of the connecting levers according to the arrangement described in the preceding paragraph wherein each connecting lever is provided-with a closed arcuate slot intermediate its ends through which a shaft extends and which establishes a pivot axis for the connecting levers, the longitudinal axis of the slot being disposed generally parallel with the longitudinal axis of the relatively straight connecting lever, and the lever being shifted, during its pivotal movement, generally longitudinally of itself on the shaft from one end of the slot to the other, thereby effecting a progressive decrease in the efiective length of the input lever arm to which the key lever is connected and a simultaneous progressive increase in the effective length of the output lever arm to which the draw-bar is connected.

Thus the advantage of the particular novel connecting lever arrangement about to be described permits acceleration of the type bar to the greatest possible velocity which heretofore has been impossible to achieve with prior known constructions under comparative kinematic conditions and equal lift of key. Moreover, application of'a type bar actuating mechanism in accordance with the present invention makes it now possible to achieve likewise advantageous striking and acceleration effects even for a typewriter of the so-called low construction with its inherently restricted number of working parts, although such effects were hitherto obtainable only in larger ofiice machines with their essentially more ample operating mechanisms. 7

The foregoing and other objects and advantages inherent in the invention will become more apparent from the following description of a preferred embodiment of the invention when considered with the accompanying drawings. As to the latter, Fig. 1 is a view in longitudinal vertical section through a typewriter of low.construction andwherein the particular type bar actuating mechanism in accordance with the invention is drawn in bolder lines to distinguish the same from the remaining and otherwise conventional structural components of the machine, and Fig. 2 is a view to larger scale of the connecting lever construction which is the heart of the invention, the lever being shown in one of its extreme positions in solid lines and in the other extreme position in dashed lines.

With reference now to the drawings, the typewriter of low construction is indicated generally by reference numeral 1. It includes a lower frame 2 and a paper carriage 4 movable transversely on the frame on bearings 3, the carriage 4 supporting the usual platen 5 which receives the paper (not shown) on which the typing is to take place. A bearing block 6 extending over the entire width of the typewriter 1 is fastened inknown manner between lateral upright supports 2a on the frame. This block is provided with upper and lower slots 6a and 6b. Along the block 6 are arranged upper and lower horizontal bores which receive respectively upper and lower,

transverse, horizontally extending parallel round shafts 7 3 bra-rah arm a extending obliquely Hawaii/aid and towards the rear of the frame. a The end of each arm 10a terminates in a rounded head 10]).

On the lower shaft 8 there are swingably journalled in the lower slot '6b'of the bearing block 6 aplurality of parallel arranged connecting leversell, there "being one connecting lever associated with each key lever 10 and each of said connecting -levers being provided with an arcuate seat 1113 having the same curvature as, and receiving, 'theround'ed head 'ifibof thea'ssociated key'lever so as to 'enablea sliding action'between the two surfaces as the head 10b rotates in its se'at 1'1b.

The lower, front end of 'theconnec tinglever armportion 11a is provided with *a small aperture 11c which receives and anchors'one'end of a helical tension'spring 12, and the other end ofspring 12 issi'rnilarly anchored to an'intermediate portibnofthekey lever '10 by attachment in a'small aperture'lfic. The spring 12 functions to "effect a return of'th'e type 'bar to its rest position following release of the key lever'as'soc'i'ated therewith and also serves to positivelyconn'ect each key lever 10 with its associated connecting lever 11.

The lower, horizontally extending shaft 8, provided to establish pivot bearings for the c'o'nncting'levers 11 in the bearing block '6 passes through an arcuately curved, closed slot 11d located at substantially the intermediate part of each lever 11, the'longitudinal axis of slot 11d being disposed generally parallel with the longitudinal axis of the relativelystraight connecting lever 11 and extending obliquely downward toward the typewriter front. Connected pivotally to the outer end of the other arm 11a of each lever 11 is one end of adrawfbar 13, the other end of the bar being pivotally connected to the lower, comparatively 'short lever 14a of the associated type bar 14, the type bars 14 being pivotally mounted upona transversely extending, horizontal shaft 15 arranged on a bar'segment '16. The latter is fixed in a rearwardly upward sloping position on a support 212 upstanding upon the typewriter frame-2, by means of screws 17. The upper part of'segment 16 carries a plate 18 which is fastened onto theseginent by means of screws 19, and whose upper part 1821 is bent forwardly and slotted so that it serves to guide the type bars 14 in the platen striking position. i v e v In order to guide the key lever's'lh, there is disposed in front or the bearing block 6a vertically disposed transversely extending guide plate 20 provided with vertical slots receiving the respectively'alignedportions of the key levers 10. The upper end of the "guidefplate 20 terminates in'a rearwardly'extending horizontalflange, the rear edge portion 20a of 'which is fashioned into an inverted U-shaped channel constituting a seat fora pad 21 made from rubber or like material. As is 'clear'from the drawings, the upper edge of each key lever "10 bears against the lower face of pad '21 and hence serves to damp the motion of the key levers when released to return to their rest positions.

On the upper side of bearing block 6 there is arranged a lug '22 which carries a horizontal, transversely extending U-sha-ped rail 23in which is seateda pad 24 of rubber or like materialagainst which the upper ends of the type bars 14 abut when in the rest position. 7

The mode of operation of the improved type actuating barmechanism in accordance with the invention is as follows: H H g When any one of the key-levers 10 is depressed, thus to move the same in a clockwise direction about its end pivotal support shaft 7, a corresponding movement 'is transmitted to the input armportion 11a of connecting lever '11 via the rounded head 10!; working in its seat 11b. The pivotal motion of lever 11, which is against the restoring action of spring 12, is always about anaxis represented by the center of shaft 8. However, due to the fact that lever 11 is mounted slidably upon shaft 8 by means of the closed, arcuate slot 11d the force "applied to input arm 1122 'bythe key lever head 10b in addition to effecting a rotary, clockwise movement of lever 11 about shaft 8 also causes the lever 11 to move generally longitudinally of itself thus moving the sides of the slot 11d along the shaft 8.

The sliding movement of lower 11 occurs simultaneously with its rotary movement about the shaft 8 with the result that the instantaneous arris'of rotation of lever 11 represented by the center of shaft 8 moves progressively along the lever slot 11d from a starting-position shown in full lines in the drawings wherein the top end of slot 11d engages the surface of shaft 8 to a terminal position shown in dashed lines wherein the bottom end of slot 11d; engages shaft 8. Consequently, it will now be evident that as the instantaneous axis'of rotation of lever 11 shifts progressively along the lever slot in response to a progressively increasing downward displacement of the key lever 10, the eifective length of input lever arm 11a, represented by the iristantaneousdistance between the head "10b and shaft '8, is progressively decreased; simultan'e'ou's'ly, the effective length of output lever arm 11e, represented by'the iiistantaneous distance between shaft '8 and the' outerf'en'd of arm 112, to which one end of the draw-bar '13 "is attached, is progressively increased. This simultaneous decrease in the length of the input lever sr'm naane increase in length of the output lever arm 11e thiisbrings about'a compounding of-acceleration to motion of the dr'aw-bar-13 and hence also to the type bar 14 thu's'cau'sin'g apr'ogre'ssive increase in the velocity of the type at the outer'e'nd'of typebar 14 so that the type will then strike the paper onplaten 5 with an extremely highspe'ed, and hen'ce'rnoinentiim, which results in sharp and darkcarbons where m'nlti-copy work is necessary. Itis also reflected by an increase in typing speed. De-

. creasing the'length of the {input arm lla'results in a corresponding progressiv increase 'in the angular velocity of the lever 1-1 about its pivot axis for a given linear change in displacement of key lever 10, and increasing the length of the *outputarm '11e results in 'a corresponding progressive increase'in thedisplacement'of the outer end of arm 11a for agivenangular-displacement of the lever 11. The arc'uate curvature of slot 11d assures a smooth change in the transmission ratio of lever 11 as regards its input and outpntjarm's. I

After the type bar 14 strikes the paper on platen 5, whereuponffin ger pressure ii 'rton the corresponding key lever 10 is released, spring '12 effects a return movement of the connecting lever 11 and hence also the draw-bar 13 and type bar 14 to their respective rest positions, the connecting 1e'ver 11 sliding back until the top end of slot 11d again rests 'upon shaft 8.

'In conclusion it is to be understood that while an exerr'iplary embodiment of the invention has been described and illustrated, obvious modifications may be made in the construction and arrangement of component parts without, however, departing from the spirit and scope of the invention as defined in the appended claims. Thus, for example, the shape of the connecting levers 11 may be changed in such manner-"that further functions are derived from it, for example, the typewriter ribbon switch motion. Also, while the principle of the invention makes the same particularly useful for typewriters having an overall low construction commonly calledfportables, the same principle can 'beincorporated in typewriters of larger construction.

I claim: I

1. in a type bar actuating mechanism for typewriters, particularly those having an overall low construction, the combination comprising pivotally mounted key levers coupled to their respective pivotallymounted type bars by means of connecting levers and draw-bars, said connecting levers each being provided with'a closed elongated slot intermediate the ends thereof and being pivotally mounted intermediate their ends on a stationary shaft working in and along the elongated slots'in said connecting levers to establish two oppositely extending input and output lever arms on each connecting lever, said input arm being pivotally connected to the corresponding key lever and said output arm being pivotally connected to one end of the corresponding draw-bar, the other end of said drawbar being connected to the corresponding type bar, thereby to efiect a progressive change in the instantaneous position of the pivot axis of said connecting lever along said lever in response to continued displacement of its associated key lever in a direction to effect a corresponding progressive decrease in the length of said input arm and a progressive increase in the length of said output arm.

2. A type bar actuating mechanism as defined in claini 1 wherein said slot in each connecting lever is arcuate and extends obliquely downward toward the front of the typewriter.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain Nov. 26, 1952

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