US3665850A

US3665850A - Selective belt printing apparatus for printing a line at a time

Info

Publication number: US3665850A
Application number: US852697A
Authority: US
Inventors: Ralph Berger; Howard Satterlee
Original assignee: New England Merchants National Bank
Current assignee: New England Merchants National Bank
Priority date: 1969-08-25
Filing date: 1969-08-25
Publication date: 1972-05-30
Anticipated expiration: 1989-05-30

Abstract

Printing apparatus is provided in which an entire line of print is printed at one time and wherein a sheet of paper is advanced past a printing station so that a series of lines of printing can be successively printed thereon. The printing is effected in a plurality of parallel columns, with which are aligned a like number of belts on which are located the print characters. These belts are driven by one or more drums in repetitive cycles. In each cycle each of the belts is brought to a halt with the desired character at the printing line in the printing station and when a line of print has been thusly compiled, a single hammer unit drives the characters against a ribbon to print the line on the paper. The belts are then returned to an initial position of rest in preparation for the next succeeding cycle for the next succeeding line of print. The print hammer may be actuated from the same source of power which drives the drum or drums and there may be related to this source of power a stepping device which steps the paper through the printing station.

Description

O United States Patent 1151 3,665,850

Berger et al. 1 May 30, 1972 s41 SELECTIVE BELT PRINTING 3,139,818 7/1964 Koehn ..1o1 93 c APPARATUS FOR PRINTING A LINE AT 3,139,822 7/1964 Lj g "W C A TIME 3,364,852 1/l968 Ragen ..lOl/93 C [72] Inventors: Ralph Berger, McLean, Va.; Howard Sat- Primary Examiner-William B. Penn terlee, Madeira Beach, Fla. Attorney-Roberts & Cohen [73] Assignee: New England Merchants National Bank, 57] ABSTRACT Boston, Mass. Printing apparatus is provided in which an entire line of print [22] Filed 1969 is printed at one time and wherein a sheet of paper is advanced [21] Appl. No.: 852,697 past a printing station so that a series of lines of printing can be successively printed thereon. The printing is effected in a plurality of parallel columns, with which are aligned a like 2% number of belts on which are located the print characters. '6 l l l These belts are driven by one or more drums in repetitive cy- 1 o cles. In each cycle each of the belts is brought to a halt with the desired character at the rintin line in the rintin station h p g h l p 1 d g l and w en a line of print has been t us y compi e a sing e [56] Reta-mm cued hammer unit drives the characters against a ribbon to print the UNITED STATES PATENTS line on the paper. The belts are then returned to an initial posinon of rest 1n preparanon for the next succeedmg cycle for the MlleS 1 1 next succeeding line of print The print hammer may be actu- 2'168-364 8/ 1939' Schaefer 101/336 X ated from the same source of power which drives the drum or 2'2o4153 6/1940 y et 101/111 X drums and there may be related to this source of power a 2. 1 3/ 1945 Keuper 101/ 1 1 1 X stepping device which steps the paper through the printing sta- 2,90l,540 8/1959 Canepa.... 101/111 X fi 3,010,387 11/1961 Deutsch... l01/1llX 3,135,195 6/1964 13 Claims, 15 Drawing Figures Potter 101/93 C S0! A/0 ID ELECTRON/C 56H P067770 CONTROL 66 Mao/64rd? 85 if)? RALPH BERGER HOWARD sATTERLEE A'I'TORMCYS Patented May 30, 1972 I 6 Sheets-Sheet 2 EJTZL u g l .II.II.IL.LNLFLrLr.

I mun 1 mu llHl [Trim NHL RALPH QERQER HOWARD SAT-TERLEE Patented May 30, 19'?2 6 Sheets-Sheet 5 QR Q mwm mm E S E R L O R H RE N T EMT EM me D M P W A0 RH \mm Patented May 30, 1972 3,665,850

6 Sheets-Sheet L RALPH BERGER HOWARD SATTERLEE I i Y Patentd May 30,1912 3,665,850

6 Sheets-Sheet 5 INVI'JNIOHS RALPH BERGER HOWARD SATTERLEE Patented May 30, 1912 3,665,850

6 Sheets-Sheet 6 SELECTIVE BELT PRINTING APPARATUS FOR PRINTING A LINE AT A TIME DRAWING FIG. 1 is a diagrammatic side view of a printing apparatus provided in accordance with one embodiment of the invention employing a plurality of driving drums;

FIG. 2a is a front view, on enlarged scale, of one of the driving drums;

FIG. 2b is an enlarged view of a portion of the aforesaid driving drum illustrating in cross-section printing belts supported on the said drum;

FIG. 3a is a side view of a printing belt employed in the invention in stretched-out condition;

FIG. 3b is a top view of the belt of FIG. 3a;

FIG. 4a is a diagrammatic illustration of the alignment of a plurality of belts when a printing operation is ready to be effected;

FIG. 4b is a diagrammatic view of the belts of FIG. 4a in their alignment at the start of a printing cycle;

FIG. 5 is a detailed view on enlarged scale illustrating how the ends of the belts are connected together in an endless loop;

FIG. 6 is a diagrammatic view on enlarged scale showing further details of the apparatus of FIG. 1 relative to the supply of paper;

FIG. 7 is a diagrammatic view illustrating the printing ribbon supply for the apparatus of FIG. 1;

FIG. 8 is a diagrammatic view of a clock or position indicator for use in the apparatus of FIG. 1;

FIG. 9 illustrates in diagrammatic form a modification applicable to the apparatus of FIG. 1;

FIG. 10 diagrammatically illustrates a second embodiment of the invention; and

FIGS. 11a and 11b diagrammatically illustrate the printing elements and arrangement for the apparatus of FIG. 10.

FIELD OF INVENTION This invention relates generally to printing apparatus and more particularly to a medium speed printer capable of printing, by way of example, 60 to 100 lines per minute.

It is an object of the invention to provide an improved printing apparatus of the aforenoted type capable of reliably printing by the use of components which are readily and economically assembled and serviced.

SUMMARY OF INVENTION In accordance with the invention there is provided a printing apparatus which comprises a sheet supply means for displacing a sheet of record medium such as paper through a printing station in a determinable direction to enable line-byline printing on said sheet in lines perpendicular to said direction and in a multitude of parallel columns aligned with said direction. .A plurality of belts is employed with the belts being arranged in parallel to the aforesaid columns to which they correspond in number and in alignment. These belts preferably include like assortments of print characters serially distributed along corresponding lengths thereof.

The belts are driven by suitable driving means such that the aforesaid lengths are driven at least partly through the aforesaid printing station. A locating means is operatively associated with each of said belts to terminate movement thereof through the station so that a preselected print character is brought to a printing line at the printing station in each of the said columns.

in accordance with the invention a printing means is employed which displaces the thusly compiled line of print characters towards the sheet simultaneously to print an entire line at one time.

In further accordance with the invention, the means for driving the lengths bearing the characters through the printing station includes means for returning such lengths to a starting position from which the lengths can be driven in entirety through the printing station in a succeeding cycle.

To provide for succeeding cycles there is provided apparatus for stepping the sheet line-by-line through the printing station in equal time increments. Also provided is a device to supply print ribbon between the sheet and print means.

As will be shown in greater detail hereinafter, the drive means and print means cooperatively include at least one drum for releasably driving the belts and a print hammer extending linearly across the aforesaid columns at the printing station. Cyclical means is provided to drive the aforesaid drums cyclically and there are actuating means responsive to this cyclical means to actuate the print hammer.

According to one feature of the invention, the cyclical means includes a pinion driven by a rack and in turn driving a sprocket which drives a chain which in turn drives a second sprocket coupled to the drum or drums driving the aforesaid belts. A crank is employed for driving the aforesaid rack and a cam is connected to and moves with the crank shaft and operates a toggle coupled to the print hammer.

Each of said belts may include two axially arranged sections, one of which includes the print characters and the other of which includes ratchet teeth by means of which the belts may be engaged for being halted with a proper character in position. This halting operation may be effected, for example, by a sole operating stop which selectively engages one of the aforesaid teeth.

The sheet supply device employed in accordance with the invention may preferably include a ratchet and pawl assembly to supply driving power to a sprocket drive, the pawl being connected to the print hammer through intervening mechanisms so that the operation of these two elements is synchronized.

In accordance with one embodiment of the invention, the belts are driven by a plurality of drums with spaced parallel axes.

In accordance with another embodiment of the invention, a single drum is employed which is encircled by the aforesaid belts.

BACKGROUND There are a number of printer constructions which employ displaceable belts cooperating with print hammers to effect a printing operation.

One such apparatus is known from U.S. Pat. No. 3,113,509 (V. R. Simpson) which issued Dec. 14, 1963. As will be seen from the description which follows hereinafter, the Simpson apparatus is distinguishable in that it employs a belt arrangement wherein the belt is aligned with the printed line and because it further employs a print hammer arrangement which is unlike that employed in accordance with the present invention.

U.S. Pat. No. 3,164,084 (W. G. Paige), which issued Jan. 5, I965, likewise employs a plurality of belts to constitute a high speed belt printer, there being moreover employed an internal hammer arrangement. The apparatus disclosed by this patent is unlike that of the present invention in that it employs a plurality of print hammers and does not provide for bringing a multitude of characters to a single line of print to be operated upon simultaneously by a single hammer.

U.S. Pat. No. 3,188,947 (W. G. Paige), which issued June 15, I965, similarly provides a plurality of belts, but is distinguishable in that a plurality of print hammers is employed, each of which is associated with a relatively small number of belts. There is not shown in this patent an arrangement whereby an entire line of print is effected through the use of a single print hammer and consequently the arrangement of this patent is considerably more expensive and complicated than the arrangement of the present invention.

DETAILED DESCRIPTION An exemplary purpose of the present invention is to provide a medium speed printer capable of printing for example, 60 to lines per minute. In a preferred machine each line consists of, for example, I32 columns wherein the characters are spaced one-tenth of an inch apart. The characters, by way of example, occupy an area 0.093 X 0.063 inch in size.

In the particular machine under discussion, there are six lines of print per inch. Each row or line of 132 columns is set up during a single cycle and at the end of the cycle the entire row or line of characters is printed at one time.

At the end of a given portion of a printing cycle and directly after the printing of a single line, the sheet of paper on which printing is being effected advances and provision may be made that the associated printing machine will advance at the same time.

The cycle then includes a reverse portion causing all columns to be reset to zero or starting position. As will be seen hereinafter, the term reverse is a generalized expression since the cycle can be zeroized by circular movement all in the same direction.

A printing operation consists of a plurality of repeated cycles in each of which a line of print is first assembled and then employed in a single hammer operation.

With reference to the details schematically shown in FIG. 1, a printing apparatus in accordance with one embodiment of the invention comprises a plurality of

drums

20, 22, 24, and 26 rotatable on

shafts

28, 30, 32, and 34, the drums and shafts having spaced and parallel axes arranged at the four comers of a rectangle.

A plurality of belts, such as diagrammatically indicated at 38, encircles the aforesaid drums and are driven by these drums in a manner which will be indicated with greater particularity hereinafter.

On each of the above mentioned shafts is mounted a sprocket wheel. More particularly, on shaft 28 is mounted a sprocket wheel 40, there being additionally provided sprocket wheels 42, 44, and 46 mounted on shafts 30, '32, and 34 respectively.

The aforesaid sprocket wheels are engaged and driven by a chain 48 arranged as an endless loop and in turn engaged by and driven by a sprocket wheel 50. Rotation of the sprocket wheel 50 drives the chain 48 thereby driving sprocket wheels 40, 42, 44, and 46, which in turn drive the

drums

20, 22, 24, and 26 and thereby the belts 38.

From FIGS. 2a and 2b can be seen the construction of the above noted drums and the accommodation of the belts 38 thereon. Drum 20 is illustrated by way of example in FIG. 2a. It is a one-piece cylindrical element provided with a plurality of annular grooves 52 separated by annular ribs 54. The drum may be, for example, two inches in diameter and the grooves 52 therein may be, for example, a total of 132 in number, the grooves being spaced by the ribs 54 at a distance, for example, of 0.100 inch. The drums may be made of any metal having suitable strength.

In FIG. 2a it is seen that the grooves 52 accommodate the belts 38 which lie flatly against the drum in said grooves. By way of example, in FIG. 2b are shown in section belts 38a, 38b, and 380. These belts are, by way of example, 0.080 inch wide and 0.005 inch thick. They can be fabricated of metal or plastic and can be coined, etched, or molded. The belts have such relationship with the drum that they are normally driven by the drum when the drum is rotated. However, movement of the belts can be arrested without impeding movement of the drum.

The construction of the aforesaid belts is indicated with greater particularity in FIGS. 3a and 3b. Therein it can be seen that each such belt is formed of serially connected sections such as indicated by

brackets

56 and 58. Section 56 is the print character including section. In this section will be included a plurality of characters 60 which may include, for example, the complete alphabet in capital letters, the complete alphabet in small letters, a series of numbers and whatever other signs and symbols are required to effect a normal printing operation. In the preferred embodiment of the invention, 128 such characters are provided.

The belt section 58 includes a plurality of ratchet teeth 62. As will be shown, the ratchet teeth constitute a part of the arrangement by which the belts are brought to a halt for the appropriate positioning of the aforesaid characters. For this reason the ratchet teeth are identical in number to the number of characters 60. The pitch of the teeth and characters may, for example, be 0.166 inch and with 128 teeth and characters a total belt length of 42.6 inch will be involved.

FIGS. 4a and 4b show diagrammatically the use of belts of the aforesaid construction, it appearing that the belts 38 will be effectively staggered relative to each other to bring selected characters thereon to a print zone or area 64 for a printing operation. FIG. 4b shows that in the beginning of a printing cycle the belts 38, or more particularly, the character 7 sections 56 thereon, are all in an initial starting position of alignment with one another wherefrom the belts are transported such that the sections 56 tend to move in entirety through the printing zone 64. In fact, and as will be shown in greater detail hereinafter, movement of the belts or belt sections is intercepted so that these sections end up in the staggered relationship appearing in FIG. 4a for purposes of a printing operation. The staggered relationship will, of course, be different for different printing cycles and printing operations so that a different line of print will be employed for each printing operation.

The belts are not employed in the stretched-out condition appearing in FIGS. 3 and 4. They are instead employed with their ends connected to form an endless loop. This appears in greater detail in FIG. 5 where can be seen a spring-like serpentine element 66 formed, for example, of beryllium copper or stainless steel, or the like, and connected to the ends 68 and 70 of a belt 38.

Where the belt 38 is fabricated of metal, the element 66 will be welded, braized or soldered to the ends thereof which are to be connected. If the belt 38 is fabricated of plastic, the element 66 can be molded into position.

In any event, and with reference once again to FIG. 1, the belts 38 are supported in juxtaposed and parallel position corresponding to the columns which are to be printed and they are driven to move the characters past the printing zone by means of the aforenoted sprocket 50.

Sprocket wheel 50 is mounted on shaft 72, having mounted thereon a pinion gear 74. Pinion gear 74 is engaged and driven by a rack 76, rack 76 in turn being driven by crank 78.

The crank 78 in the illustrated embodiment of the invention under discussion is driven continuously in one direction so that the rack 76 is driven in opposite directions illustrated by arrow 80. This operates to drive the belts 38 first in one direction and then in the other direction for each complete cycIe. It will be understood that, since crank 78 has a circular movement and rack 76 a linear movement, the speed of the rack and thus the belts will be essentially sinusoidal, the belts coming gradually to a zero velocity at which printing may be effected. The magnitude of movement which the belts 38 undertake is such that due to such movement all of the characters on each belt will be able to move past the printing station.

In fact, and as has been noted hereinabove, this movement is intercepted so that a preselected character on each belt will be arrested in said printing station. The mechanism for accomplishing this is illustrated in the form of a solenoid 82 having associated therewith a stop 84. There is one such solenoid and stop for each belt and it is the function of each stop to engage one of the ratchet teeth on the associated belt as has been described hereinabove. The time at which the stop 84 will move into a position of interference is controlled by an electronic control 86, the details of which are not important to an understanding of this invention. However, it is to be understood that the electronic control 86 operates in conjunction with a belt position indicator 88 which may, for example, be controlled by an element mounted on the shaft 72 so that the electronic control 86 may select. the character to be brought to the printing station for a particular belt 38 depending on the data supplied to the control 86 for purposes of controlling the printing operation.

The printing zone referred to hereinabove is a zone extending transversely of the columns of print and the direction of movement of the belts 38 and is, moreover, a zone which lies adjacent the print bar or hammer 90 and the print back up bar 92 between which elements pass all of the belts 38. There is also provided a print ribbon 94 by means of which ink is deposited upon the record medium or sheet 96 of paper upon which the printing operation is to be effected.

Print hammer 90 is displaced by means of a toggle 98 including links 100 and 102. When these links are in rectilinear alignment, hammer 90 is displaced towards back up bar 92 and a printing operation is effected. When links 100 and 102 are angularly related as in the illustrated position thereof, the hammer 90 is withdrawn from the bar 92.

The relative attitude of links 100 and 102 is controlled by a linkage 104 pivotally connected at 106 to a link 108 supported on a pin 110. This linkage system is controlled by a cam 112 mounted for rotation with crank 78 on a shaft 1 14.

It will be appreciated from what has been stated hereinabove that rotation of crank 78 drives rack 76 and creates the driving force for the belts 38. It will now be ap preciated further that such rotation actuates the link 104 and the toggle 98 and thus the print hammer 90. As a consequence thereof movement of the belts 38 and that of the hammer 90 are related. They are more particularly related so that movement of the hammer 90 follows the least possible time in which a different character can be moved through the printing zone so that a complete selection of characters is possible before the printing operation is effected. Specifically, this means that all of the characters on each of the belts 38 will have the opportunity if not previously intercepted to move to a position adjacent hammer 90 before this hammer will be motivated to effect a printing operation.

The hammer 90 is mounted on lever 114, in turn pivoted on pin 1 16. This is employed in the control of paper supply as will soon be seen. As part of the paper supply apparatus there are provided

sprockets

118 and 120 coupled to a chain 122. Also there are provided

guides

124 and 126. The paper 96 in strip or sheet form passes between the guides and the aforesaid chain and is engaged by the

sprockets

118 and 120 and driven through the printing zone around the back up bar 92 and thence in the direction of discharge as indicated by arrow 128. The drive of the paper 96 is incremental and can best be appreciated from an examination of FIG. 6.

In FIG. 6 is shown the back up bar 92 in association with the print hammer 90 and ribbon 94, the hammer being mounted as aforesaid on the lever 114.

An arm 130 contacts lever 114 and atop the arm 130 is pivotally mounted a pawl 132 supported on pin 134 and connected with arm 136. Pawl 132 engages a ratchet wheel 138 connected with sprocket 118 such that rotation of the ratchet wheel 138 rotates sprocket wheel 118 which is effective through chain 122 to drive sprocket wheel 120. It will also be seen that the pawl 132 is loaded by spring 140.

From what has been stated hereinabove, it will now be appreciated that movement of the hammer 90 in upward direction against back up bar 92 will carry arm 130 therealong and thus will carry along therewith pawl 132.

Upward movement of pawl 132 will be to the extent of one tooth on ratchet wheel 138 so that return movement of hammer 90 will cause pawl 132 to displace ratchet wheel 138 by an amount which is equal to one tooth, this in turn corresponding to the distance equal to that between successive lines of print on the sheet 96. As aforesaid, when there are six lines of print to the inch, this distance will be equal to 0.166 inch.

Also to be noted in FIG. 6 is the solenoid 142 actuated by coil 144 for the displacing of armature 146. Armature 146 cooperates with arm 136 to deactivate pawl 132 when it is desired that movement of the print hammer 90 not be accompanied by corresponding movement of the paper driven by

sprockets

118 and 120.

The drive of the ribbon 94 appears more particularly in FIG. 7, wherein it is seen that the supply of the ribbon 94 includes a supply spool 148 and takeup spool 150. The paper is indicated again at 96 and the printing zone at 64. It is to be understood that the ribbon is purposefully passed at an angle relative to zone 64, since thereby a wider ribbon can be employed which is easier to control than a narrow ribbon. Movement of the ribbon 94 is provided by increment drive of a type corresponding to that employed for driving the paper.

FIG. 8 illustrates a clock or counter or position indicator 152 which can be mounted on the shaft 72 as aforesaid to provide information for the belt position indicator 88 of FIG. 1. The element 152 may be a sprocket wheel, a photoelectric device, a magnetic device or any other such device capable of generating pulses indicating movement of the wheel through the increments 154 corresponding to the various characters to be printed.

One such wheel may be associated with sprocket drive 50 to indicate the overall displacement which the drive tends to give to the belts 38. Pulses or other such signals derived from the element 152 will be counted in well known digital manner in the indicator 88 and this count will be compared in the control 86 also in well known manner with digital representations of the characters which are to be printed. Comparison when determined will be used to actuate the stops 84 to bring the corresponding belts to a halt. This terminating of the motion of the belts is possible due to the fact that the engagement between these belts and the associated drums is frictional and any given belt can be brought to a halt with a selected character thereon in position at the printing zone even though the remaining belts may still be moving through the printing zone.

In a given cycle when the time has elapsed for all characters to have been brought through the printing zone, as determined by the cycle of crank 78, hammer will effect a printing operation and the belts 38 will be brought back to their initial position as determined by a stop (not shown) installed on each of the belts. The apparatus will then be ready for the next successive cycle which will be a repetition of what has been described above.

FIG. 9 illustrates a modification of which the apparatus of FIG. 1 is susceptible. This modification involves simply the adjustable mounting of the

drums

24 and 26 on adjustable bearing supports 156 and 158. The purpose of this adjustment is to provide for taking up slack in the belts 38 and also to align the characters to the print slot. This adjustment may require a take up of slack in the chain 48. Such requirement is met by the provision of a take up spool 160 mounted on a swingable arm 162.

A second embodiment of the invention appears in FIGS. 10 and 11, wherein it is seen that a single drum 164 can be employed instead of the plurality of drums descussed hereinabove. In this embodiment, belts 166 encircle the periphery of the drum and are selectively brought to a halt by means of a pivotal element 168 mounted for pivotal movement on pin 170 and controlled by solenoid 172. Movement of the paper 174 is diagrammatically illustrated as being controlled by

drives

176 and 178, the paper moving around a back up 180 for the printing of successive lines.

FIGS. 11a and 11b diagrammatically illustrate how printing is effected, the back up 180 in this case being displaced by

links

182, 184, and 186 to displace the back up toward and away from the drum and the print belt thereon in a manner generally like that which has been noted hereinabove.

What is claimed is:

1. Printing apparatus comprising sheet supply means for displacing a sheet of record medium through a printing station in a determinable direction to enable a line-by-line printing on said sheet in lines perpendicular to said direction and in a multitude of parallel columns aligned with said direction, a plurality of belts parallel to said columns and corresponding in number thereto, said belts including like assortments of print characters serially distributed along corresponding lengths of said belts and having an initial position from which the belts can be displaced, drive means for driving each of said lengths through said station, said drive means being reversibly displaceable at a sinusoidally variable speed between two limits, locating means selectively operable to engage with each of said belts to terminate movement thereof through said station while said drive means continues its movement in one direction toward one of said limits whereby a preselected print character is brought to a printing line at said station in each of said columns, and print means to displace the thusly compiled line of print characters towards said sheet simultaneously to print an entire line all at one time when said drive means is at one of said limits, said locating means being operatively associated in timed relation to the operation of said drive to be disengaged from said belts to permit said belts to be returned by said drive means to said initial position when said drive means is displaced in the other direction towards the other of said limits.

2. Apparatus as claimed in claim 1, wherein the means for driving said lengths through said station includes means for returning said lengths to a starting position from which the lengths can be driven in entirety through said station in a succeeding cycle.

3. Apparatus as claimed in claim 1 comprising means to supply a print ribbon between said sheet and print means and wherein said sheet supply means includes means for stepping the sheet line-by-line through said station in equal time increments.

4. Apparatus as claimed in claim 1, wherein said drive means and print means cooperatively include at least one drum for releasably driving said belts, a print hammer extending linearly across said columns at said station, cyclical means to drive said drum cyclically, and actuating means responsive to the last said means to actuate said hammer.

5. Apparatus as claimed in claim 4, wherein said cyclical means includes a pinion, a rack displaceable in opposite directions to drive said pinion in alternate directions, a

sprocket coupled to said pinion, a chain driven by said sprocket, a second sprocket coupling said chain to said drum, and a gear for driving said rack alternately in opposite directions; and wherein said actuating means includes a cam coupled to and moving with said gear and a toggle coupled to said hammer and actuated by said cam.

6. Apparatus as claimed in claim 1, wherein each said belt includes two serially arranged sections one of which includes said print characters and the other of which includes ratchet teeth.

7. Apparatus as claimed in claim 6, wherein said locating means includes a solenoid-operated stop for selectively engaging said teeth.

8. Apparatus as claimed in claim 6, wherein each said belt includes a spring element closing the belt in an endless loop.

9. Apparatus as claimed in claim 1, wherein the sheet supply means includes a sprocket drive, a ratchet and paw] assembly for driving the sprocket drive, said pawl being coupled to and driven by said print means, said print means having idle and active positions and driving said pawl upon returning from active to idle position, and means for selectively preventing engagement of the pawl with said ratchet.

10. Apparatus as claimed in claim 1, wherein said drive means includes a plurality of drums, with spaced parallel axes, for frictionally engaging and driving said belts.

11. Apparatus as claimed in claim 10, wherein at least one of said drums is adjustable, said drive means further including a chain for driving the drums simultaneously and means to take up slack in the chain to account for adjustment of said one drum.

12. Apparatus as claimed in claim 1, wherein said drive means includes a single drum, said belts being arranged to encircle said drum.

13. Apparatus as claimed in claim 3, wherein the means to supply a print ribbon includes means to supply the same at an angle across the printing lin

Claims

5. Apparatus as claimed in claim 4, wherein said cyclical means includes a pinion, a rack displaceable in opposite directions to drive said pinion in alternate directions, a sprocket coupled to said pinion, a chain driven by said sprocket, a second sprocket coupling said chain to said drum, and a gear for driving said rack alternately in opposite directions; and wherein said actuating means includes a cam coupled to and moving with said gear and a toggle coupled to said hammer and actuated by said cam.

9. Apparatus as claimed in claim 1, wherein the sheet supply means includes a sprocket drive, a ratchet and pawl assembly for driving the sprocket drive, said pawl being coupled to and driven by said print means, said print means having idle and active positions and driving said pawl upon returning from active to idle position, and means for selectively preventing engagement of the pawl with said ratchet.

13. Apparatus as claimed in claim 3, wherein the means to supply a print ribbon includes means to supply the same at an angle across the printing line.