US3750792A

US3750792A - Automatic media thickness compensator for a printer

Info

Publication number: US3750792A
Application number: US00278174A
Authority: US
Inventors: G Liles
Original assignee: NCR Corp
Current assignee: NCR Voyix Corp
Priority date: 1972-08-04
Filing date: 1972-08-04
Publication date: 1973-08-07
Anticipated expiration: 1990-08-07

Abstract

A carriage having a print head thereon is traversed along a platen to enable the print head to print along a line of printing in a serial-type printer. The print head moves with the carriage and is also mounted thereon for independent movement towards and away from the platen. A leaf spring biases the print head towards the platen, and a sensing finger, secured to the print head, contacts and glides along a thin, self-supportable, flexible tape which overlies media of various thickness mounted on the platen to maintain the print head (like a wire matrix) a predetermined distance from the media enabling the print head to print on various thicknesses of media automatically.

Description

United States Patent 11 1 Liles 1 Aug. 7, 1973 1 AUTOMATIC MEDIA THICKNESS 1,874,0I3 8/1932 Kaddeland 11mm 3,627,096 l2/l97l Finnegan 1. 'l97/l R COMPENSATOR FOR A PRINTER Inventor: George N. Liks, Dayton, Ohio Primary Examiner koben Pun-my [73] Assignee: The National Cash Register s istant E qginerR. T. Raqler 7 Company, Dayton, Ohio Attorney-J. T. Cavender and Albert L. Sessler, Jr.

[22] F1led: Aug. 4, 1972 [57] ABSTRACT PP N-1278i174 A carriage having a print head thereon is traversed along a platen to enable the print head to print along 52 us. c1. 197/1 R, 340/259, 346/139 c a line of Printing in serial-type w The print head 51 1m.c1 B41] 3/50 moves with the carriage and is also mounted thereon 581 Field of Search 197/1, 18,49, 55, for independent movement towards and y from the 197/126, 128, 137, 149; 346/76 R, 74 CH, 74 platen. A leaf spring biases the print head towards the E, 7 M, 74 MC 39 C, 3 235/619; platen, and a sensing finger, secured to the print head,

, 101/35, 4144; 340/259 contacts and glides along a thin, self-supportable, flexible tape which overlies media of various thickness 5 Ref C t mounted on the platen to maintain the'print head (like UNTED STATES PATENTS a wire matrix) a predetermined distance from the 3 705 408 ""972 K t I 346/139 C media enabling the print head to print on various thickrone 6 a r 3,146,058 8/1964 Henshaw 346/139 0 of aummat'cany' 2,141,975 I2/1 938 Finch..,..'. 346/139 A 4 Claims, 8 Drawing Figures 26 -36 "W l 1 l E g I V 3 1, f1"? 1 .1 I i l 20 68 l 9O /28 '1 i 66 r I I I 106' 1 l I J i l I l l =Ei:.!.] .i|. -\;llJ| I09 '1' ',ir" Q I I 1 I I I -1 L LL1Q9," as

z I) D I I 64 86 l 1 1 I v 1 r 24 1 I 48 l l l 1 l 1 1 5 1 1 i A i 1 2 1; 3 ti 1 X i 34 H 40 60 1 p T 1 PAIENIEU Au; 7 m5 SHEEI 1 (If 4 sum Q 0F 4 FIG. 8

FIG. 6

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 is a plan view of a portion of a serial-type wire matrix line printer on which the forms compensator of this invention is mounted. The forms compensator comprises a carriage means having a conventional wire matrix print head means 22 mounted thereon. A traversing means 24 traverses the carriage means 20 along a platen 26 of the printer to enable the print head means to print along a line of printingon the platen. The forms compensator also includes a mounting means 28 for mounting the print head means 22 on the carriage means 20 to enable the print head means to be reciprocated along a line which is perpendicular to the line of printing along the platen. A biasing means 30 (FIG. 2) is used to resiliently urge the print head means 22 towards the platen 26. A sensing means 32,.cooperating with the print head means 22 is used to sense the thicknesses of the media located on the platen and to move the print head means away from said media against the bias of said biasing means 30, as a thicker medium is encountered along the line of printing. The biasing means 30 then moves the print head means 22 towards the platen 26 as a thinner medium is encountered. This action permits the print head means 22 to be spaced a predetermined distance from the media along the line of printing regardless of the thickness of the particular medium mounted on the platen and being printed upon.

Media of various thicknesses are shown on the platen 26 in FIG. 1, as for example, medium 34 may be a single sheet tally or audit roll, and medium 36 may be a multi-sheet pass or bank book. The forms compensator of this invention is capable of automatically adjusting the print head means 22 relative to the platen 26 in response the thickness of the particular medium being printed upon. Having media of different thicknesses mounted on the same platen to be printed upon along a single line of printing is common in accounting machine practices.

The carriage means 20, alluded to earlier, includes a base 38 having brackets 40 upstanding therefrom as shown in FIG. 2. These brackets 40 support a horizontally positioned rail 42 which is positioned parallel to the rotating axis of the platen 26, and a flat horizontally positioned rail 44 is secured to the underside of the rail 42 as shown in FIG. 2. A carriage member 46, of the carriage means 20, abuts against the rail 42 and rests upon the rail 44.

A conventional traversing screw 48, of the traversing means 24, passes through the carriage number 46, and is coupled thereto by the construction shown principally in FIG. 3. This construction includes two nuts and 52 which are inserted into split bushings or protrusions S6 and 58 respectively, which bushings are secured to the carriage member 46. The

nuts

50 and 52 are adjusted on the traversing screw 48 in a conventional manner so as to provide a minimum of backlash of the carriage member 46 on the screw 48 over the entire length thereof, and each nut is then clamped in its associated bushing by a fastener 58 as shown in FIG. 2. The ends of the traversing screw 48 are conventionally supported in bearings (not shown), and the screw 48 is rotated by a conventional constant-speed motor (synchronous or servo controlled) or a stepping motor 60 (FIG. 1) to traverse the carriage means 20 along the platen 26 as the characters are printed by the wirematrix, print head means 22. During printing, the stepping motor 60 runs as a continuous motor, and the dots printed by the seven print head wires which are ar-' ranged in a column (as described earlier in the Background of the Invention) are really printed on the fly" as the print head means 22 is traversed along the line of printing by the motor 60. The main advantage of the stepping motor 60 is that it is low cost and'fairly easy to control by electronics. Because these aspects may be conventional, they are not described in detail.

The mounting means 28, for mounting the wire print head means 22 on the carriage means 20 for reciprocating movement towards and away from the platen 26, is shown in FIGS. 1, 2, and 3. The mounting means 28 includes a base 62 (best seen in FIG. 3) which base has vertically extending sides against which

plates

64 and 66 are secured by fasteners 68. The plate 64 has a horizontally positioned V-shaped groove on theouter face thereof, into which groove, a plurality of ball bearings 72-is positioned. A plate 74, also has a horizontally V- shaped groove therein which groove is complementary in shape to the groove in plate 64, and the plate 74 is fastenedto the carriage member46 by fasteners 76 toretain the ball bearings in the grooves'and support the left end (as viewed in FIG. 3) of the base 62. Apin 78 (FIG. 2) projects from the plate 64 into the associhead'means 22 is mounted on the carriage means 20 for perpendicular movement towards and away from the platen 26 while the carriage means 20 is being traversed along a print'line on the platen 26.

The-wire matrix print head means 22 includes a wire matrix print head unit 86 which is secured to the base 62 on the carriage member 46 by two fasteners 88 shown in FIG. 1. The print head unit 86 has conventional actuators like 90 and print wires or wire plungers 92 which are supported in a wire guide'or'housing 94, which is supportedon a bracket 96 secured to the base 62. The wire plungers92, when actuated, come out of the end 98 (FIG. 1) of the housing 94 and impact against a medium on the platen. The print head unit 86 is of a known variety which utilizes seven wire plungers 92 located in a vertical line as shown in FIG. 8. In order to print a completecharacter, like the letter M,.for example, when using a five by seven matrix format, the stepping motor 60-would run as a continuous motor to move the print head along the line of printing on the platen, and five successive impacts by the print head unit 86 would be required to complete the letter. One prior art print head unit, like the one described, has control electronics which include a run emitter" clock which is operatively associated with the traversing screw 48 and the motor 60 to allow the screw to rotate at a constant speed. A print emitterclock also associated with the traversing screw 48 and the motor 60 in combination with the control electronics creates the necessary fire pulses (to the actuators 90) which pulses are phased with the motion of the traversing screw 48 to enable accurate horizontal spacing of the dots produced by the successive impacts of the print head unit 86. Because the techniques for energizing the print head unit 86 are conventional, they are not described in detail herein. A plate 100 (FIG. 2), secured to the bracket 96, supports two spaced and vertically positioned

posts

102 and 104 which are used as ribbon guides. As shown in FIG. 1, an inked ribbon 106 passes behind post 102, around the front end of an adjustably fixed deflector guide 107 and one side of the end 98 of the housing 94, around the front end 98 of housing 94, around the front end of an adjustably fixed deflector guide 109 located on the opposite side of the housing 94, and behind the second post 104. The bracket 96 has a well 108 (FIG. 2) located therein beneath the housing 94, and a curved wall 110 and a vertically positioned flat wall 1 12 form opposed contact areas in said well.

The biasing means 30 alluded to earlier is shown in FIG. 2. As stated earlier, the biasing means 30 is used to resiliently urge the wire matrix print head means 22 towards the platen 26 along a line which is perpendicular to a line of printing thereon; it should be recalled that the print head means 22 is also mounted for reciprocal movement relative to the platen. The biasing means 30 includes a leaf-type spring 114, having one end fixed to a lever 116 by fasteners 118. The free end of the spring 114 passes through a suitable slot in the carriage member 46 and extends into the well 108 and abuts against the curved wall 110 therein to resiliently urge the print head means 22 towards the platen 26 with a force of one-fourth to onehalf pound. The lever l 16 has a square hole therein between the ends thereof, enabling the lever to be slidably mounted on a bar 120 which is square in cross section as shown-in FIG. 2. The bar 120 extends along the length of the platen and is parallel to the traversing screw 48. Bar 120'has its end conventionally, rotatably mounted in the side frames (not shown) of a printer in which this invention is located. One end 122 of lever 116 passes through a suitable slot in the carriage member 46 and extends into the well 108 located in the bracket 96. The remaining end of the lever 116 has two

notches

124 and 126 therein to receive apawl member 128. The lever 116 also has a hub portion 130 fixed thereto on each side thereof, and each. hub portion has a square opening therein which is aligned with the square opening in the lever 116 to provide a sliding fit on the square bar 120. Each hub portion like 130 is rotatably mounted in an apertured flange 132 which is secured to the carriage member 46 by fasteners 134. By this construction, the lever 1.16 is carried by the carriage member 46 as it is traversed along the platen 26 and is capable of being independently rotated in clockwise and counterclockwise directions by the square bar 120. A lever 136 (FIG. 1) is fixed to the bar 120 by a flange 138 to rotate the bar. One end of the lever 136 has an actuating arm 140 of a solenoid 142 secured thereto.

The print head means 22 is moved away from the platen 26 to permit the insertion of

media

34, 36 by the construction just described. When the solenoid 142 is energized, the operating arm 140 (FIG. 1) rotates the lever 136 and bar 120 in a clockwise direction (as viewed in FIG. 2). When so rotating, the lever 116 which is slidably secured to square bar 120, will also be rotated in a clockwise direction enabling end 122 thereof to contact the vertical wall 112 in well 108 and move the entire print head means 22 away from the platen 26 to the position shown by the dashed outline 144 in FIG. 2. The mounting means 28, already described, enable the lever 136 to move the print head means away from the platen 26, and it is held in the away position by the pawl member 128 entering notch 126 (FIG. 2) after the lever 116 is rotated. When the solenoid 142 is deenergized, a spring (not shown) asso' ciated with the operating plunger thereof, will return the print head means 22 to the position shown in solid lines in FIG. 2 in which pawl member 128 enters notch 124 as shown. This position enables the print head means 22 to move freely towards the platen 26 to engage it without the end 122 of lever 116 contacting the vertical wall 112. The leaf spring 114, secured to lever 116, urges the print head means 22 towards the platen 26.

The sensing means 32, (FIGS. 1 and 2) alluded to earlier, cooperates with the print head means 22 to contact the media on the platen 26 and to move the print head means away from the media as a thicker medium is encountered along the line of printing and to enable the biasing means 30 to move the print head means 22 towards the platen as a thinner medium is encountered, thereby enabling the print head means 22 to be spaced a predetermined distance away from the particular medium being printed upon regardless of its thickness. This adjustment is made automaticaly without any adjustment by an operator using thisinvention.

The sensing means 32 (FIG. 2) includes a flexible tape means 200, mounting means 202 for mounting the tape means 200, and a sensing finger 204.

The mounting means 202 is best shown in FIGS..2 and 6 andincludes a shaft 206 which is secured to the side frames (not shown) of the printer in which this invention is used. A plurality of U-shaped brackets, like 208, are rotatably mounted on the shaft 206, and these brackets are spaced equally along the length of the platen 26. Each bracket 208 has aligned apertures therein to receive a shaft 210 which also extends along the length of the platen 26.

Shafts

206 and 210 are parallel to the rotating axis of platen 26. Two

rollers

212 and 214 are conventionally, rotatably mounted on the shaft 210 and are located between the arms of each bracket 208 as shown in FIG. 6. Each bracket 208 is fixed at various spaced locations along the length of the platen 26 by

nuts

216 and 218 which are fastened to threaded portions of the shaft 210. A tension-type spring 220 (FIG. 2) having one end secured to the arm of the bracket 208 closest to the sideframe (not shown) of the printer, and the other end of thespring secured to the side frame, is used to resiliently rotate all the brackets 208 and shaft 210 in a counterclockwise direction (as viewed in FIG. 2) to enable the rollers like 212 and 214 to press the media into contact with the platen, as is conventionally done. The shaft 210 and brackets 208 also support the flexible tape means 200 in the position shown in FIG. 2.

The flexible tape means 200 has the general shape shown principally in FIGS. 4 and 6, and includes an elongated area or tape 220 which extends along the length of the platen 26 and has long fingers 222 and short fingers 224 depending therefrom. The tape means 200 is typically made of stainless steel, having a thickness of about 0.005 inch, and is flexible and self supporting. The long fingers 222 and short fingers 224 are spaced apart equal distances, and each adjacent pair of long fingers 222 has one of the brackets 208, positioned therebetween as shown in FIG. 6. Each long finger 222' has a curved section 226 on the free end thereof which substantially encircles the shaft 210 when positioned thereon as shown in FIG. 6. The shaft 210 has suitable circumferential grooves therein to receive C-type lock rings 228 which restrain each long finger 222 from axial movement on the shaft. By this construction, the tape means 200 is free to rotate on shaft 210 but is axially restrained thereon. When the tape means 200 is positioned next to the platen 26, there is a tendency for the tape means to rotate in a clockwise direction (as viewed in FIG. 2) under the influence of gravity. This clockwise rotation occurs when the print head means 22 is moved away from the platen 26 to the position shown by the dashed line 144. To keep the tape means 200 from rotating away from the platen, a lip 230 is formed on each bracket 208 as shown in FIGS. 2 and 6, and the associated short finger 224 of the tape means 200 is then positioned between the lip 230 of the associated bracket 208 and the platen 26.

The sensing finger 204 has a spherically shaped end which contacts and glides along the elongated area or tape 220 of the tape means 200. The finger 204 has an axis which is positioned along a radial line from the axis of the platen 26, and the finger is held in that position by a bracket 232 which is secured to the plate 100.

The operation of the sensing means 32 is as follows. Assume that the medium 34 on the platen 26 is a single journal sheet, and that a pass book 36 is positioned over a portion of the sheet 34 as shown in FIGS. 1 and 7. The sensing finger 204, tape means 200, and print head means 22 are urged against the journal sheet 34 by the leaf spring 114 of the biasing means 30 (FIG. 2). As the print head means 22 is traversed across the platen 26 by the traversing means 24, the sensing finger 204 glides along the length of the elongated area or tape 220 of the tape means 200, pressing against the journal sheet 34 to maintain the end 98 of the print head a fixed distance away from the journal sheet 34. Notice that at the junction 232 between the thinner sheet 34 and the thicker pass book 36 (FIG. 7), the tape means 200 provides a gradual transition therebetween due to the tape means being flexible. As the sensing finger 204 rides over the junction 232, it will push the end 98 of the print head away slightly from the platen against the bias of the leaf spring 114 to maintain the end 98 at substantially a fixed distance from the pass book 36. As the'print head means 22 is traversed further to the right side of the platen 26 (as viewed in FIG. 7), the sensing finger 204 rides over a junction point 234 between the pass book 36and the platen 26. At the junction point 234, the tape means 200 provides a gradual transition between the pass book 36 and the platen 26 enabling the biasing means 30 (FIG. 2) to urge the print head means 22 towards V the platen 26; the sensing means 32 would then keep the print head means 22 a predetermined distance away from the platen 26. Naturally, this predetermined distance is dependent upon the type of printer used; however in the embodiment shown, this distance was 0.010 inch to 0.025 inch.

Upon completion of a line of printing, the platen 26 will be indexed by conventional means, and the print head means 22 will be returned to the left margin of the ally rotated to rotate square bar in a clockwise direction (as viewed in FIG. 2), or the solenoid 142 (FIG. 1) may be energized causing lever 116 to rotate in a clockwise direction and thereby push the print head means 22 away from the platen 26 to the position shown by the dashed line 144 in FIG. 2. With the print head means 22 moved away from the platen, media positioned thereon can be easily removed and new media can be easily positioned thereon. The controls for operating the stepping motor 60, solenoid 142, platen 26 and print head means 22 may be conventional, and accordingly, need not be described in any further detail. While this invention is described in conjunction with a wire matrix printer, this invention may be used with other printers in which it is desirable to keep the print heads thereof at fixed distances away from media of various thicknesses located on the associated platens.

FIG. 8 shows the end 98 of the housing 94 as seen from the platen 26. The end 98 has openings 178 therein from which the wire plungers (like 92 in FIG. 2) emerge to impact against the media. The housing 94 is mounted on the print head means 22 by the fasteners 186, I88 and 190 shown in FIG. 1. The wire plungers (like 92 in FIG. 2) are withdrawn within the holes 178 (FIG. 8) when in the inactive state to enable the plungers to be accelerated (when energized) to obtain the required hammer impact energy prior to impacting or printing after emerging from the holes 178.

When the print head means 22 is traversed at a rapid stepping rate along the platen 26 by the traversing means 24, the action of the sensing means 32 in riding up a thicker medium on the platen causes a force pulse urging or bouncing the print head means 22 away from the platen. The faster the stepping or printing rate, the greater is the force pulse which is created in moving the print head means 24, and as a result, damping may be needed to minimize the bouncing or moving away of the print head means from the platen.

A damping means which may be used with this invention, should bouncing of the print head means 22 become a problem, is shown in FIGS. 2 and 3. An elastomeric block 180, made of a material like polyurethane rubber, is bonded to the surface 182 of the base 62 of the print head unit 86 and is also bonded to a plate 184 which is free to slide on surface 186 of the carriage member 46. The block is compressed sufficiently through conventinal trial and error techniques so that the combined drag force created by the partially compressed block and plate 184 is a fraction (like onethird to one-half of the force of leaf spring 114 which urges the print head unit 86 towards the platen 26. Small motions of the print head means 22 away from the platen 26 are damped by the block 180 alone, and larger motions of the print head means are additionally clamped by the sliding of plate 184 on surface 186. If the retract motion of the print head means 22 to the position shown by the dashed outline 144 is not desired, the plate 184 can be eliminated, and the block 180 may be bonded directly to the surface 186.

What is claimed is:

1. In a forms compensator for sensing the thicknesses of various media mounted on a platen of a serial-type line printer having:

a carriage means having-a print head means thereon;

traversing means for traversing said carriage means along said platen to enable said print head means to print along a line of printing on said platen;

mounting means for mounting said print head means on said carriage means for simultaneous movement therewith along said print line and for independent reciprocal movement of said print head means along a second line which is transverse to said line of printing; and biasing means for resiliently urging said print head means along said second line towards said platen; the improvement comprising; sensing means secured to said print head means to contact the media on said platen and to move said print head means away from said media as a thicker medium is encountered along said line of printing and to enable said biasing means to move said print head means towards said platen as a thinner medium is encountered, thereby enabling said print head means to be spaced a predetermined distance from said media along said line of printing regard: less of the thickness of a particular medium being printed upon on said platen; said sensing means comprising:

a support means extending along the length of said platen; a thin, self-supportable, flexible tape means mounted on said support means and extending along the length of said platen to overlie themedia thereon;

and a finger means fixed to said print head means for contacting said tape means as said print head means is traversed along said platen.

2. The compensator as claimed in claim 1 in which said tape means has an elongated area'which is positioned parallel to said platen to overlie the media thereon, and said finger means includes a sensing finger which contacts said elongated area.

3. The compensator as claimed in claim 2 in which said support means include:

a stationary shaft having its longitudinal axis mounted parallel to said platen;

bracket means pivotally mounted on said stationary shaft;

a second shaft mounted parallel to said stationary shaft on said bracket means, and spring means to urge said second shaft towards said platen; and

roller means mounted on said second shaft to press the media against said platen;

said tape means further having spaced long fingers depending from said elongated area, with the free ends of said fingers encircling said second shaft to support said elongated area along said platen.

4. The compensator as claimed in claim 3 in which bracket means having lip means thereon; and said tape means further having spaced short fingers depending from said elongated area, with the free endsof said short fingers being positioned between said lip means and said platen so as to retain said elongated area near said platen.

I ll i i

Claims

1. In a forms compensator for sensing the thicknesses of various media mounted on a platen of a serial-type line printer having: a carriage means having a print head means thereon; traversing means for traversing said carriage means along said platen to enable said print head means to print along a line of printing on said platen; mounting means for mounting said print head means on said carriage means for simultaneous movement therewith along said print line and for independent reciprocal movement of said print head means along a second line which is transverse to said line of printing; and biasing means for resiliently urging said print head means along said second line towards said platen; the improvement comprising; sensing means secured to said print head means to contact the media on said platen and to move said print head means away from said media as a thicker medium is encountered along said line of printing and to enable said biasing means to move said print head means towards said platen as a thinner medium is encountered, thereby enabling said print head means to be spaced a predetermined distance from said media along said line of printing regardless of the thickness of a particular medium being printed upon on said platen; said sensing means comprising: a support means extending along the length of said platen; a thin, self-supportable, flexible tape means mounted on said support means and extending along the length of said platen to overlie the media thereon; and a finger means fixed to said print head means for contacting said tape means as said print head means is traversed along said platen.

2. The compensator as claimed in claim 1 in which said tape means has an elongated area which is positioned parallel to said platen to overlie the media thereon, and said finger means includes a sensing finger which contacts said elongated area.

3. The compensator as claimed in claim 2 in which said support means include: a stationary shaft having its longitudinal axis mounted parallel to said platen; bracket means pivotally mounted on said stationary shaft; a second shaft mounted parallel to said stationary shaft on said bracket means, and spring means to urge said second shaft towards said platen; and roller means mounted on said second shaft to press the media against said platen; said tape means further having spaced long fingers depending from said elongated area, with the free ends of said fingers encircling said second shaft to support said elongated area along said platen.

4. The compensator as claimed in claim 3 in which bracket means having lip means thereon; and said tape means further having spaced short fingers depending from said elongated area, with the free ends of said short fingers being positioned between said lip means and said platen so as to retain said elongated area near said platen.