US2002695A - Control mechanism for typewriting machines - Google Patents

Description

May 28, 1935. H. A, FOOTHORA'P 2,002,695 7' CONTROL MECHANISM FOR TYPEWRITING MACHINES Filed July 24, 1950 5 Sheets-Sheet l y 1935. H. A. FOOTHORAP 2,002,695

CONTROL MECHANISM FOR TYPEWRITING MACHINES Filed July 24, 1930 5 Sheets-Sheet 2 May 28, 1935. H. A, FOOTHORAP CONTROL MECHANISM FOR TYPEWRITING MACHINES Filed July 24, 1930 5' Sheets-Sheet 3 W %N \M\ r 3 M. \W

mw aw S ww mmmm .wmv M M May 28, 1935.

H. A. FOOTHORAP 2,002,695

CONTROL MECHANISM FOR TYPEWRITING MACHINES v Filed July 24, 1930 5 Sheets-Sheet 4 4 3' 3 o [I n h 3% w W 0Q Q) 3714902111306- y 8, 1935. H. A. FOQTHORAP 2,002,695

CONTROL MECHANISM FOR TYPEWHITING MACHINES Filed July 24-, 1950 5 Sheets-Sheet 5 Patented May 28, 193

CONTROL MECH MACHINES A A A 2,002,695 UNITED STATES PATENT OFFICE,

ANISM FOR- TYPEWRITING Harry A. Foothorap, Harrisburg Pa., assignor, by

mesne assignments,

to Underwood Elliott Fisher Company, New York, N. Y., a corporation of Delaware Application July 24, -19 30, Serial No.470,519 23 Claims. (01. 197-2) My invention relates to improvements in platen operating and control mechanism for typewriting machines of the class embodying a fiat work clamping platen depressible from the writing plane to release the workyand printing mechathe work to line and letter space the printed record; and to a return posinism movable over tion clear of the work.

In my U. S. Patent No. 1,904,127 dated April 18, 1933, there'is disclosed an exempliiication of this class of typewriting machine, to-wit, an Elliott-Fisher machine equipped with a motor drive-to return the prin mg mechanism-transversely of the'machine to the left handmargin, or longitudinally of the machine to clear the work,

as desired.

The principal object of my invention is to equip a machine of the above class so asto provide for the automatic depression of the platen, in timed of the printing mechanism to different positions, whereby movement ofsaid mechanism, beyond that necessary to clear the work sheets or forms of different lengths, is obviated and operation of the machine relation to return movement expedited.

Another object of my invention is to provide platen depressing mechanism sufiiciently reactive in character to yieldingly retainthe platen in work-clamping position, but susceptible of operation to depress the same by application of a negligible amount of power, so that it may be operated either by a movable part of the machine, for instance, the printing mechanism, without imposing any appreciable extra load on said part, or, by a slight pressure of the hand upon a key lever.

' To theaccomplishment of the above andother objects subordinate thereto, and presently appearing, a preferred embodiment of my invention will now be described in' detail, with refer-' ence to the accompanying drawings/and particularly defined in the claims appended hereto.

Insaid drawings,

Figure l is a top plan view illustrating my novel platen operating and control mechanism applied to an Elliott-Fisher machine of. the type above mentioned,

Figure 2 is a rear elevation drawn on an enlarged scale, with parts of the printing mechanism eliminated for-the sake of clearness,

Figure 3 is afragrnentary view in side elevation, parts showing in section,

Figure 4: is a longitudinal sectional view taken on the line i-4 of Figure l, V

Figure 5 is a fragmentary view, similar to Figure l, but drawn on an enlarged scale,

Figure 6 is a transverse sectional view taken on the line 6-5 of Figure 1,

Figure '7 is a similar view taken on the-line I-1 of Figure l,

7 coupling contacts,

on the line 9-9 of Figure 2,

ill-I31 of Figure 9,

mounting therefor,

of said toggles and its mounting,

the line 15-45 of Figure 14,

detail of one of said toggles,

ative and inoperative positions,

the line I8 -|8 of Figure 1'7,

on the line 2!-2l of Figure 8."

, v Figure 8 is a perspective view of a coupling device mounted on the line space carriage, a mounting and a latching mechanism included therein, and a platen-operating crank with which the Figure 9 is a vertical sectional view further illustrating the parts shown in Figure 8, and taken Figure 10 is a detail view partly" in horizontal section and partly in top plan taken on the line.

Figure ,11 is a similar view taken on the line Figure 12 is a detail view of a part of the latching mechanism, on the line 12-42 of Figure 9, Figure 13 is a view partly in side elevation and partly in section, of one of a purality of platenmoving toggles forming partof my platen operati'ngmechanism, together with a ball bearing 'Figure 14 is a view in side elevation of one Figure 15 is a view in vertical section taken on Figure 16 is a sectional view of a structural :Figure 17 is a view in side elevation of a portion of the control bail of the machine, and a motor control cam thereon adjustable to oper- Figure 18 is a vertical sectional view taken on Figure 19 is a similar view illustrating a motor control cam adjusted into inoperative position, Figure 20 is a fragmentary sectional view of a detail of the platen operating mechanism, and V Figure 21 is a longitudinal sectional view taken Referring to the drawings, and first to the general equipment of the Elliott-Fisher machine, I '(Figs. 1, 4 and 5) designates the usual track frame thereof formed by side members 2 and front, intermediate, and rear members 3, 3 and 3 respectively. The fiat platen 4, located within the frame I, supports the workin a flat spread-out condition and in its normal elevated position, cooperates with overlying edge clamping bars 5, on the members 2, to clamp the work in position. Theframe l is'equipped with idler rolls 6 for facilitating the feeding of endless forms over the platen 4, which need merely be identifiedin passing, since their function and operation is well understood in connection with these machines.

The printing mechanism, proper, which is of the usual type bar and key lever class, is supportedby a printing head or carriage I mounted by rollers 3 upon the rails H and I2 of a line space carriage 9, for movement transversely of theplaten to letter space the printed record. The printing head is propelled and controlled by sition. For further details clutches, not shown,

' otally moimted,

the front and intermediate members 3 and 3.,

the usual typewriter appurtenances, such as the spring motor In, and escapement mechanism, not shown.

The line space carriage 9, sometimes called the line space frame, but herein termed the carriage, and including the front and rear rails H and I2, respectively, and stretcher members I 3 connecting the rails, is movable longitudinally of the platen 6 upon rollers M (Figs. 2 and'3) running on tracks on the frame side members 2.

The line space carriage 9 is driven by a line space shaft it (Figure 2) journaled in said carriage and having fast thereon toothed pinions l'l meshing with racks E8 on the side members 2. Said shaft forms part of a line spacing mechanism, illustrated conveniently at l9, which, sufiice it to say, operates said shaft in the proper direction to move the carriage 9 forwardly line space distances at a time. For details of this feature, reference may be had to my previously mentioned patent.

Referring to the motor drive, a motor 20 mounted upon the carriage 9' drives the line space shaft l 6 through a motor control shaft 2 i, also mounted on the carriage, inter-meshing pinions 22 and 23 fast on the line space and motor control shafts, respectively, and forward and reverse driving in the housing 24. The motor control shaft 2| is endwise movable from a neutral position to engage either clutchso that the carriage is capable of motor operation forwardly, to quickly locate it over the work, or through a return excursion, to clear the work prior to removal of the same, or for other purposes, such as correction or proof reading.

Movement of the motor control shaft 2!, in either direction, is effected by operation of a motor control bail 25 (Figures 1-3, 6 and 7) pivas at 25, on one frame member 2 to rock in opposite directions, respectively, and with which the motor control shaft 2| has a travelling connection in the form of a grooved wheel 2? (Figure 2) fast on said shaft and engaging the upper edge of said bail. The control bail 25 is rocked primarily, in the desired direction, by a pair of knee levers, one of which is-shown at 28 (Figures 3-5) fast on individual shafts 29 (Figures 6 and 7) mounted in the frame I and suitably connected by linkage, indicated at 30, (Figure 4) with the bail 25. Stops 3| (Figures -7) on the shafts 2s limit movement of said shafts and bail.

At each end of the motor control bail 25, a cam 32 (Figures 1-3 and 6) is provided. As the carriage 9 nears the limit of either its forward or its return excursion, a lug 33 on the carriage engages the proper cam and rocks the bail to move the motor control shaft 2| to neutral poof the motor drive, reference may be had to my patent, previously mentioned. i

In accordance with my invention, the platen 4 is anchored in a semi-floating condition within the frame I by a pair of subjacent platen guiding links 34 (Figures 4 and 5) extending longitudinally of the platen with their front ends pivoted at 35 adjacent the front member 3 of the frame and their rear ends pivoted at 36 to brackets 31 suitably secured to the under face of the platen.

Beneath the platen there is provided tensioned platen counter-balancing mechanism, including, preferably, a pair of opposed vertically movable bell crank levers 38 pivotally mounted at 39 on respectively, of the frame along-ithe longitudinal median line of the platen 4, a retractile counterbalance spring 40 connecting the lower arms of said bell-crank levers 38, whereby the upper arms of the levers exert elevating counterbalancing forces in opposition to the weight of the platen 4.

In'actual practice, the elevating forces exerted by the counterbalancing mechanism are, in the elevated position of the platen, less than that opposed thereagainst by the weight of the platen, but equal to said weight in the fully depressed position of said platen, and elevating forces sufficient to overcome the uncounterbalanced weight of the platen and sustain it in work-clamping position are supplied by the reactive platen operating mechanism now to be described.

Vertically disposed operating toggles M (Fig ures 4-6) are located beneath the platen i and roughly speaking, in proximity to the respective corners of the platen near the side edges thereof.

These platen-operating toggles are arranged, therefore, in pairs, one pair towards the front end of the platen and the remaining pair of toggles towards the rear end, thereof, and adapted for simultaneous operation to depress and to raise the platen, while maintaining it substantially level or horizontal.

The respective toggles each comprise a link 44 and twin levers 52, the latter being fulcrumed intermediate their ends on hubs 43 (Figures 13-15) projecting inwardly from the inner faces of the side frame members 2, which hubs are secured in place by suitable fastenings, as the screws 49 passing through the side frame members from the outer faces thereof.

The twin levers 42 are so fulcrumed on their hubs as to provide short upper arms @3a and longer lower arms 63b, the twin members of each lever being slightly spaced apart, in which position they are held by the headed bolts 52, passing through apertures in the outermost twin lever, the threaded ends of the bolts engaging bushings 53 (Figure 16) screwed into the corresponding twin lever.

Ball bearings 41 occupy opposed races t8, 5!, in the hub 43 and twin levers 32 respectively, andrelieve the friction at this point.

The upper end of the link 64 is pivotally connected to the lower face of the platen #3 at 25, the lower end of the link being embraced between and pivoted at 35 to the free ends of the upper shorter arms 43a of the twin levers 43. The pivotal points 43, Q5, and 46 lie in alinement when the toggle is straightened or extended to forma dead centre locking the platen in its raised or elevated position wherein it clamps the work between its upper face and the edge-clamping bars 5.

Springs 54 connected to the respective joints 46 'of their associated toggle levers ii and to studs 55 on the frame I tend to straighten the toggle levers and maintain them in such positions.

The provision of both counterbalancing means typified by the spring pressed fingers 38, and the platen raising and lowering mechanism, typified by the toggle mechanisms 4!, may require additional explanation.

The spring 40 (Figure 4) is of just sufficient strength to sustain the weight of the platen d in its elevated position, without material or substantial pressure against the ledges or paper edge clamping bars 5. In other words, the parts are in equilibrium.

The toggles 4| and their operating mechanism afford a means to positively raise and lower the Cil aooaeos platen, and to press the platen with considerable force against the under surfaces of the paper edge clamping bars 5 to hold the work sheets in place.

Due to differences in temperature, and for other reasons, the platen is liable to warp and a strong pressure against the platen is required to flatten the latter to hold the edges of the platen firmly against the clamping bars throughout their length. V Therefore, to provide the considerable pressure necessary to clamp the work between the platen and the paper clamping bars 5, and to maintain the toggles in their straightened positions, the toggle springs 54 must be very strong.

Given the above conditions, it will be seen that, in depressing the platen, suiiicient energy must be exerted on the universal shaft 55 to overcome the gradually increasing tension of the already tensioned Strong springs 55, as well as the lesser gradually increasing tension of the counterbalancing spring 40.

Release of the Luiiversa shaft 56 enables the strong springs 5 operating upon the toggles 4|, and the counterbalancing spring 49 operating through the fingers 38, separately from the springs 54, to restore the platen to elevated position. i

As soon as theplaten reaches its elevated position, the effect of the counterbalancings'pring 49 becomes practically nil, but the strength of springs 54 is only slightly'reduccd, considerable tension remaining therein to press the platen firmly against the paper clamping bars 5.

It will be understood that the platen is not raised appreciably, past its counterbalancing position by the springs 54, the important function of which is to press the platen against the paper clamping bars with suiiicient force to hold the work in place, reduce the warpage, if any, platen, and produce a uniform clamping action.

The toggles M are connected to a universal cross-shaft 5K5, (Figures 4-7) journaled in ball bearings 51 in'the frame side members 2', for simultaneous operation, as follows. The front and rear toggles 4! on the same side of the'platen 4 have their long arms Mb connected by links 58 pivotally connected at 59 to the free endsof depending arms Bii fast on the shaft 55. Said shaft 56 is operatively connected by means of a depending arm 6! fast thereon and a draw link-52m an operating crank 63 (Figures 1-4) pivoted at the rear of the frame I on a step bearing E4, and movable rearwardly tooperate the shaft 56 and toggles 4! in a platen-depressing direction. The operating crank 63 is provided with a stop arm 85, (Figures 1 and 2) adapted. to contact thecross member 52 of the frame to limit itsrearward movement, and hence the extent of depression of the platen, and at its free end, the operating crank carries a vertical roller 66, the purpose of including vertical end which will presently appear. U

Mounted on the rear of the line space carriage 9 are selective means" for establishing aneperating connection betweenthe carriage and, crank 63 in timed relation to the return of the carriage to diiferent positions. Aframe or mounting 61 brackets 58 (Figures 1-3 and 840) and horizontal upper and lower bars 59 and ill, respectively, is secured, as by bolts 1 i,- to the end members it of the carriage 9.

A coupling device 12 is mountedupon the frame 6?, including preferably, a horizontal push-bar 13 secured at one end to a vertical pintle M journaled at its opposite ends in the-upper and lower bars in the e 69 and 10, respectively, upon which the push bar may be swung: from an inoperative position, parallel with said bars, (see Figures 1 and 2) to an operative position, at a right angle to the bars 69 and 18, to provide an extension member on the carriage 9 with its free end in line with the roller 66.

A bifurcated centering head 15 is provided on the free end of the push bar it and is adjustably retained thereon by a spring pressed dog 15 (Figures 1, 2 and 21) engaging, in the normal position of the parts, a notch T! on the under side of said bar. The centering head '55 is rotatably adjustable on the bar 13 to an. inclined position as in Figure 9, in which the dog 16 engages a second notch 18 when the head is located within the frame 51, as in Figures 1 and 2, to hold the dog in unobstructing position should it be desired to tilt the line space-carriage upwardly on its rollers 14 for purposes such as repair.

The coupling device F2 is yieldingly retained in its operative and inoperative positions, respectively, by an overthrow preventing latching device E9 (Figures 1, 2, 8, 9 and 10) which may conveniently comprise a short crank arm projecting radially from the pintle is at a point intermediate its ends, an angular link 83 being pivoted at one end, at IEO, to the outer end of the crank arm 85, and having a tensi-oned spring 84 connected to its opposite end, the spring being anchored at it! to the bracket 58, as shown in Figure 10. The elements are so arranged that by swinging the coupling device from one to the other of its positions, the pivot point is shifted from one side to the other of a dead center taken through the pintle l4 and the anchorage iii! of the spring 84. I

As disclosed in Figure 10, in full lines, the coupling device is in its folded or idle position, the pivot point we lying far to the opposite side of the center of the pintle M, due to the angular link, the angle of which embraces the pintle. In this position, the free end ofthe angular link at the point of connection of the spring 8 there with, lies in-line with the pivot point ice but on the opposite side of the pintle therefrom; and

in linewith' the spring anchorage HM, and the parts so arranged from a positive latch to hold the coupling device idle.

Byswinging the coupling bar the position shown in dotted lines in Figure 10, the pivot point I05 is swung to the opposite side of its dead-center, the coupling arm as it starts its clockwise travel, first disengaging thelink 83 from the pintle, and as the pivot point "36 passes its dead center, the spring 13 i is free to snap the coupling bar to its rearward, efiective position.

A stop member 32 (Figures 8, 9 and 11) fast on the pintle 14, arrests the coupling bar 53 at either limit of its travel by contact with abutments 3 3 and El, respectively, depending from the upper rod GB of the frame.

Atie rod i512 extending between and connecting the pintle M and push bar '13, braces and affords strenyh and rigidity to the coupling device.

The push bar 13, when swung counter-clockwise (Figure 10) restores the overthrow preventing latch 83 and connected parts to the fullline positions shown, the spring 8Q operating to bring the parts to such positions as soon as the pivot point we passes the dead center.

The spring-urged link 83, by its engagement with the pintle M, operates to arrest the coupling 1 F '13 clockwise to device, and the abutment 8| merely prevents overthrow of the coupling device.

It will also be noted that, because of the overlapping arrangement of the latching device, the pivoted end of the link 83 has a greater travel than does the free end of the link.

The operation of this invention under, the different conditions presented by the use of work sheets of different lengths, is as follows:

Assume that it is desired to write or enter amounts on a full length sheet or form.

The coupling device 12 is adjusted to inoperative position (Figure 1) and the carriage 9 is shifted rearwardly along the tracks I5 to its limit of travel either by hand or motor, leaving the writing area of the platen clear to receive and support the worksheet.

As the carriage approaches its limit of rearward travel, the lower bar 16 of the frame 67 contactsthe roller 66 carried by the operating crank 63 and projecting upwardly into the path of such bar.

Continued rearward travel of the carriage to its limit of movement rocks the operating crank 63 and, through link 62, arm 55 and the universal shaft 56, (Figure 5) operates to simultaneously rock the longer arms 43b of the several toggles t! to break or fiex the latter, and positively draw the platen downwardly, against the tension of the counterbalancing means 38, 49.

The platen is thus withdrawn from the edge clamps 5 to enable the edges of the work sheet to extend therebeneath as the sheet is positioned on the platen.

Obviously, the weight of the carriage is sufficient to maintain the platen in its lowered position, against the tension of the toggle restoring springs 54 and the platen counterbalancing spring 46.

Coincident with the arrival of the printing carriage 9 at its rearward limit of travel, the trip lug 33 on the carriage wipes over the rearmost cam 32 on the motor control bail 25, rocking the bail back to its median position and shifting the motor control shaft 2! to neutral position to interrupt the motor circuit (not shown) to the motor 26 and thus cut off the transmission of power to the drive for the carriage 9. Contact of the trip lug 33 with the shoulder on the rearmost cam 32 (Figure .l) arrests the printing carriage at its rearward limit of travel.

The work sheet having been positioned on the platen, the printing carriage 9 is advanced from its rearward limit of travel manually, or by rocking the motor control bail from its median position, in the opposite direction from which it was rocked when starting the rearward travel of the carriage, to bring the printing point of the carriage to the first writing line on the work sheet or form.

The carriage, on such advance, withdraws from the path of the roller 66, to free the platen elevating and counterbalancing mechanisms to the action of their springs, which restore the platen to printing position, and cause it to press the edges of the work sheet against the edgeclamps 5 to hold the work in place.

Upon completion of the writing on the work sheet, the carriage 9 is returned to its rearward limit of travel, to lower the platen as heretofore explained, and permit the removal of the work sheet or form. I

In recording upon short, for instance, half length sheets or forms, the coupling 12 is swung to operative position and the head 15 picks up the roller 66 and depresses the platen coincidentally with return of the carriage 9 through the shorter return excursion sufiicient to clear such work.

At a suitable point on the motor control bail 25, with relation to the return position of the carriage 9 when operating on short length sheets, a motor control cam 86 (Figures 3, 17, 18 and 19) is provided to disconnect the motor drive at the proper time and in the same manner as described with reference to the earns 32. The cam 36 is preferably hinged to the bail 25, as at 81, for swinging adjustment into or out of the path of movement of the lug 33. A leaf spring 38 projects through a slot 89 in the adjustable cam 86 to bear against flat portions 89' and 96 on the cam and yieldingly retain it in adjusted position.

Mounted on one side of the main frame I is a platen depressing key lever 9! (Figures 1 and 3) connected by a link 92 with a crank arm 93 fast on the universal shaft 56, and by means of which, the platen 4 may be manually depressed without returning the printing carriage to the rear, if desired.

It will be seen that the platen counterbalancing and moving mechanisms, respectively, are adapted for normally exerting forces at a series of points against the platen to provide for elevating the same uniformly that is to say maintaining it in horizontal position. Obviously this provides for uniform clamping pressure along the edges of the work and obviates buckling of the work such as is liable to occur with non-uniform clamping pressures. Furthermore by virtue of the short and long arms 43a and 43b of the toggles ll, connection of the former to the platen 4 and springs 54, and'operation of the toggles 4| through the long arms 331) the platen operating mechanism is eifective to impose forces, or leverage, to depress the platen in excess of the elevating forces exerted by said moving mechanism. This facilitates overcoming the combined platen elevating forces and provides for easy carriage operation of said platen moving mechanism.

Ease of operation of the platen moving mechanism, in platen depressing operations is further facilitated by the relation of the points of connection of the spring 54 to the toggle ll and frame I. As will be clear these connections are such that when the lever members 32 are rocked about their fulcrums 43, in a platen depressing direction, i. e. clockwise, as viewed in Figs. 4 and 5, the leverage of the short arms 43a progressively decreases, thus increasing the efiectiveness of the long arms llib'and in direct ratio to the increasing resistance of the springs 55 and also of the spring 4t! of the counterbalance mechanism. Consequently the platen operating mechanism is operative in said direction to apply platen depressing forces gradually increasing in direct ratio to the increasing resistance exerted in a platen elevating direction.

By virtue of the advantages in leverage, described in the immediately preceding paragraphs, the platen operating mechanism is operative in a platen depressing direction, by the application thereto of a comparatively light substantially uniform force so that extra load on the carriage retracting motor is reduced to a minimum degree.

In platen elevating operations the effective leverage of the short arms 43a progressively increases in direct ratio to the decrease in force exerted by the springs 40 and 54 so that the ment of a preferred elevatingand clamping force applied is .substan-i tially uniform. The result is thatthe platen is engaged with the clampingbars with .a mini mum of shock, and rebound .andnoise are practically eliminated.

" v-The foregoing constitutes a detailed embodiform of my invention, but it is to be understood that right is herein res served to such modifications thereof as fall with.- in the scope of-the protection prayed.

I claim: r V

1. In a machine of the class described, the .combinaticn with .a platen movable toward and from the writingplane to clamp, and to releasethe work, respectively, and a travelling carriage,

movable in line and letter spacing-directions relatively to the platen; .of carriage-operated mechanism for moving the platen in one of its said directions of movement, and meansforselectively controlling operation of said mechanism in timed relation to travel of the .carriage to different positions.

, 2. Ina machine of the class described,the.com-.

bination with a vertically movable platen, and a travelling carriage, of platen-moving mochanismoperative to depress the platen, and re.- acting to exert a lifting force thereagainst, and means for automatically operating .said mecha nism to depress the platen in timed relation to travel of the carriage to different positions, said means autom tically stopping" the carriage in said different positions.

3. In a machineof the combination with a frame, a carriage travelling thereon, and a vertically movable-platen, of platen-operatingmechanism,

including selective devices on the frame and carriage;'respectively, adapted for cooperation at different points in the travel of the carriage to move the platen.

a. In a machine of the .class described, the combination with a frame, a carriagetravelling thereon, acarriage-operating motor, and a movable platen, of platen-operating and-motor-conetrolling mechanism, including selective devices onthe frame and carriage, respectively; adapted for cooperation at different points in the travel of the carriage to move the platen, and to con- V trol themotor.

5.1n a machine of therclass described, the combination with a, vertically; movable, fiat platen, anda travelling carriage, of platen-operating mechanism, including front and rear pairs of .;toggles operative simultaneously in platenelevating and depressing directions, respectively,

and locking against movement in :a platen-ole vating direction, meansfor tensioning the toggles against movement in one direction, and carriage-operated means for operating'the toggles against the actionof said :tensioning means.

6. In a machine of the class described, the combinationwith work-clamping means, including a movable platen, and clamping members with which the platen coacts to-clamp, and to release, the work; and a travelling carriageand printing nism, normallvexerting elevating forces :at a series of pointsagainstthe platen, platen-depressing mechanism operative to impose depressing forces upon said platen in excess of the elevating forces exerted by said counterbalanoing mechanism, to overcome the combined elevating forces, and carriage-operated means for operating the platen-depressing mechanism, including an extens on membe on th a ri m va to effective and ineffective positions, respectively.

.class described, the

of platenecounterbalancing mecha- '7. In a machine of the class described, the combination .with work-clamping means, ing a movable platen, with which the platen coacts to clamp, andto re-' lease, the work; and a traveling carriage and printing mechanism, of platen-counterbalancing mechanism normally exerting elevating forces at a series of points against said platen, platendepressing mechanism operative to impose depressing forces upon said platen in excess of the elevating forces exerted by said counterbalancing mechanism, carriage-operated means for operating the platen depressing mechanism, including an extension member on the carriage movable to eifective and ineffective positions, respectively, and a mechanism for yieldingly retainingsaid member in either of said positions. ,8, Ina machine of the class described, the combination with Wor -clamping means, including a bodily movable platen, and clamping members with which the platen co-acts to clamp, and to release, the work; a travelling carriage and printing mechanism, and platen-shifting mechanism; of carriage-operated mechanism effective upon the platen-shifting means, to shift the platen in one direction, such carriage-operated and a latch mechanism for retaining said member in either of said posi- 9. In a machine of the class described, the combination with a track frame, a travelling carriage and printing mechanism on the frame, and work-clamping means, including a bodily movable platen, of carriage-operated platenmoving mechanism, including an element on the frame directly operated by the carriage in one position of the latter, an extension member on the carriage for operating said element in another position of the carriage, and movable to efiective and ineffect've positions, respectively, and a latch mechanism for retaining said member in either of said positions.

10. m a machine of the class described, the combination with work-clamping means, including a vertically movable platen, of counterbalancing mechanism exerting elevating leverage against the platen, and platen-depressing mechanism, including opposed pairs of tensioned toggle levers normally exerting elevating leverage at a series of points against the platen, and operative to impose platen-depressing leverage in excess of the elevating leverageflexerted by said mechanism, to facilitate overcoming the combined platen elevating leverage, and means to simultaneously operate said levers.

1,1. In a machine of the class described, the combination with a frame, Work-clamping means, including a vertically movable platen, and a travelling .carrlage and printing mechanism, of platen depressing mechanism, including opposed pairs of tensioned toggle levers normally exer-ting elevating leverage at a series of points against the platen, and operative to impose depressing leverage against the platen in excess of said elevating leverage, a crank element on the frame, operating connections between the crank and said levers, and means for operating said crank by travel of the carriage, including an extension member on the carriage movable into and from cooperative relation to said crank.

- a m h of ing a bodily movable platen, and clamping meminclude-J and clamping members the class described, the combination with wo -krc amr n m an includ bers with which theplatenco-ac'ts to clamp, and to release, the'wor a travelling carriage and printing mechanism, and platen-shiifting mech-' anism; of carriage-operated mechanism eiiective upon the platen-shifting means to shift the platen in one direction, such carriage-operated mechanism including an'extension member on the cartions, respectively.

' 13. In a machine of the class described, the combination with a frame, a travelling carriage and printing mechanism on the frame, and workclamping means, including a bodily movable platen, of carriage-operated platen-moving mechanism, including an element on the frame directly engaging the carriage in one position ofthe latter, and an extension member on thecarriage for operating said element in another position of the carriage and movable to effective and ineffective positions, respectively.

14. In a machineof the class described, the combination with a travellingcarriage and printing mechanism, and work-clamping, includ ing 'a movable platen, of platen-moving mechanism, including opposed pairs of toggle levers ted points in the travel of the carriage.

platen, said levers being tensioned against platendepress'mg movement, and operative to exert progressively increasing leverage in opposition to the tension exerted thereagainst, and means for simultaneously operating said levers.

'17. In a'machine of the'class described, the combination with work-clamping'means, including a platen adapted for elevation and depression, of reactive counterbalance mechanism supporting less than the weight of the platen in the elevated position of the latter, and counterbalancing said platen in the depressed positionthereof, and platen-operating mechanism reacting to elevate said platen, and exerting a progressively increasing leverage in a platen-elevating direction.

I 18. In a machine of the class described, the combination with work-clamping means-including a platen adapted for elevation and depression, of reactive counter-balance mechanism supporting less than'the weight of the platen in the elevated position of the latter, and counter-balancing said platen in the depressed position thereof, vate said platen, and exerting progressively increasing leverage in platen-elevating and depressing directions, respectively.

19. In a machine of the class described, the

combination with a platen shiftable to its writing platen in, and return it to, one of its positions; op-' erating means connected with the platen-supproaches another limit or" its travel.

20. In a machine of the class described, the combination with a platen shiftable to'its writing position and to its work-releasing position, respectively; and a carriage adapted to travel relatively to the platen; of means to support the platen in, and return it to, one of its positions; operating means connected with the platen-supporting'means and extending into the path of travel of the carriage; and alternative means interposed between the carriage and the operating means to efifect the actuation of the operating means at different points in the travel of the carriage, to shift the platen to the other of its I positions.

21. In a machine of the class described, the com ination with a platen shiftable to its writing platen in, and return it to, one of its positions; operating. means connected with the platen-supporting means and extending into the path of travel ofv the carriage; and selective means interposed between the carriage and the operating relation to the travel of the carriage to difierent positions; and carriage-operated devices to control theoperation of the motor in said different positions of the carriage.

-' 23. In a machine of the class described, the

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