Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/22—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of impact or pressure on a printing material or impression-transfer material
  • B41J2/23—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of impact or pressure on a printing material or impression-transfer material using print wires
  • B41J2/235—Print head assemblies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J25/00—Actions or mechanisms not otherwise provided for
  • B41J25/001—Mechanisms for bodily moving print heads or carriages parallel to the paper surface
  • B41J25/003—Mechanisms for bodily moving print heads or carriages parallel to the paper surface for changing the angle between a print element array axis and the printing line, e.g. for dot density changes

Definitions

• This invention relates to the field of matrix printers to print letters, numbers and other graphic symbols with higher resolution than has heretofore been possible in aymbols having a total height of less than four millimeters.
• the invention relates to printing heads having adjacent printing elements spaced center-to-center as required by the diameters of the elements but offset relative to each other both horizon ⁇ tally and vertically to permit visibly separate rows of dots to be printed closer together than would be possible based on the center-to-center spacing of the elements.
• Matrix printers are commonly used with calcu- lators and computers and other electrically operated devices to print alpha-numeric information.
• Standard Arabic numbers and standard Roman letters, both capital and lower case, can be legibly printed in a matrix of 7 x 9 dots or even 5 x 7 dots arranged in a checkerboard pattern.
• a 7 x 9 array permits a maximum of four spaced vertical lines and five horizontal lines to be printed, if the dots are a full space apart, but this small number of lines is not sufficient to form a clear or even a legible reproduction of the approximately 2000 Chinese characters most commonly used in Japanese printing.
• a minimum resolv ⁇ ing power of about 13 x 13 dots is required, and preferably an array having at least 17 x 17 dots should be provided.
• a typical printing head does not have the total number of printing elements suggested by the multiplication of the two numbers that define the array.
• a 5 x 7 array does not have five columns of seven printing elements, nor does a 7 x 9 array have seven columns of nine elements. Instead, in a full-space matrix a checkerboard pattern of 35 dots is produced by providing only a single vertical column of seven printing elements and moving the printing head five horizontal incremental steps to print the 35-dot array and a 7 x 9 printer has a printing head with only one vertical column of nine printing elements. The printing head is moved seven horizontal incremental steps to print a 63-dot checkerboard array.
• the number of non-overlapping dots that can be formed in a given space is determined by the size of the printing of the printing elements.
• the dots are basically circular and the diameter of the printing elements is usually the main limitation in minimizing the spacing of the dots.
• a preferred type of impact matrix printing element is a ballistically operated wire, or needle, that is struck at one end by an armature of a solenoid to be projected forward like a spear to print a dot and then rebound with the aid of a spring. It is essential that the impact of the armature cause the needle to move axially and not simply to bend.
• About the smallest diameter needle capable of operating for a commercially acceptable length of time has a diameter of about 0.35 mm, and it ' is common practice to support the front portions of the full complement of such needles, typically seven or nine, side by side in a bearing made of suitable material, such as synthetic ruby or alumina, with a corresponding number of highly polished holes closely spaced in a row.
• the diameter of each hole is about 0.37 mm and their centers are about 0.37 mm apart. Needles smaller than about 0.35 mm in diameter, down to about 0.2 mm diameter, have been used but require a support sleeve, which limits the closeness of spacing.
• the center-to-center spacing of adjacent bearing holes determines the distance between the centers of adjacent horizontal rows of dots so that adjacent ver- tically spaced dots do not overlap substantially and this limits the number of such rows that can be formed in a given vertical space.
• the row of bearing holes is nor ⁇ mally perpendicular to the direction of incremental movement of the printing head and is therefore normally vertical.
• the row of bearing holes is slanted slightly so that the letters slope as hand ⁇ printed letters frequently do, but the center-to-center spacing of bearing holes in such heads is great enough so that the dots formed by adjacent needles do not overlap substantially.
• Such an arrangement is described in British patent specification 1,343,570.
• the kanji should not exceed 3.7 mm in height.
• Kanji normally fit within a square area, and the resolution needs to be about equal in the horizontal and vertical directions.
• the lower limit of legibility for the more complex kanji requires a dot matrix of about 13 x 13 full-spaced dots capable of making at least seven horizontal and seven vertical lines. Higher resolution matrices are desirable to increase legibility.
• This invention arranges the printing elements- of a matrix printing head so that adjacent elements are offset both horizontally and vertically with respect to each other to cause the centers of the horizontal rows of dots to be spaced more closely than would be possible if the same elements were arranged in the most compact vertical column possible.
• the head may have a standard seven or more elements to print either the upper or lower
• separate bearings may be provided for more than one set of needles.
• the separate multi-needle bearings can be mounted in precise, offset relationship to each other to allow the full number of horizontal rows to be printed in one sweep of the printing head and without having to move the paper incrementally less than one line at a time.
• Pig. 1 is a perspective view of a matrix printer in which the present invention is incorporated.
• Fig. 2 is a simplified drawing of a ballistic printing element as used prior to the present invention and as used in this invention.
• Fig. 3 shows a magnified portion of the front end of the printing head in Fig. 4 and a line of dots illustrating the printing of a horizontal line.
• Fig. 4 is an illustration of an ar ⁇ rangement of printing elements according to the prior art.
• ⁇ *JV I ⁇ Fig. 5 is a geometrical construction of an arrangement of printing according to one embodiment of this invention.
• Fig. 6 is a side view of an improved bal- listically operated printing needle constructed according to one embodiment of the invention.
• Figs. 7A and 7B show alternative embodiments of a printing head of the invention with two sets of offset printing elements.
• Fig 1. shows a typical matrix printer 11 for printing graphic symbols including letters, numbers, punctuation marks, and other symbols on a recording medium of which paper is the most common example.
• the paper 12 runs over a cylindrical platen 13 in front of a printing head 14.
• the head moves laterally on a pair of guide rods of which only one rod 16 appears in the drawing.
• the operation of the printing head in printing the symbols and in moving along the guide rods, and the operation of the platen to feed paper through the printer 11 are all electrically controlled, either by operation of a keyboard 17 or by electrical signals from other sources.
• a matrix printer builds up each symbol by printing an array of dots, each of which is produced at a specific location relative to the other dots required for any given symbol.
• the dots that make up a symbol are not all printed simultaneously, except for the simplest symbols, such as a decimal point, but are printed in a specific sequence. Each dot is printed by a printing
• each printing element is at a location identified by reference numeral 18.
• Fig. 2 shows a common printing element arrange ⁇ ment.
• the element is a thin wire, or needle, 19 sup ⁇ ported in a front jewel bearing 21 and rear guide 22.
• the front end 23 of the needle 19 faces the paper 12 wrapped partly around the platen 13.
• the paper may be a type that darkens in response to pressure, alone, which is referred to as "no-carbon" paper, or, as illustrated in Fig. 2 , it may be regular paper that requires an inked ribbon 24, which is guided through the space between the paper 12 and the front end of the needle 19.
• the needle 19 moves to the left in the arrange ⁇ ment as illustrated in Fig. 2 when struck by the armature 26 of a solenoid 27.
• the solenoid includes a U-shaped core 28 of low-carbon steel or other ferromagnetically soft material with an energizing coil 29 around one leg of the core.
• the armature 26 is pivotally supported at the end of the other leg and is biased clockwise by a spring 31.
• the needle 19 is resi ⁇ iently biased to the right by a spring 32 compressed between the plate 22 and a collar 33 affixed to the needle- near its back end 34.
• the slight curvature of the needle 19 is due to the fact that this needle is only orie of a group of such needles, usually seven or nine in number, arranged so that their front ends are in a straight line and are parallel and as close together as possible.
• the respective sole ⁇ noids for each of the needles require much more space, and so the back ends of the needles are fanned out in a circular arc arranged to minimize the curvature of the needles.
• each needle like the needle 19, receives a sharp impact force from the armature 26 when the solenoid 27 associated with that needle is energized.
• the counterclockwise movement of the armature 26 is limited, but the force of the impact is great enough to cause the needle to fly to the left, in spite of the concommitant, increased compression of the spring 32, until the front end 23 strikes the ribbon 24 and forces the ribbon against the paper 12.
• the spring 31 retracts the armature 26 by pivoting it clockwise immediately after the impact against the back end 34. of the needle 19. After the needle has flown ballistically forward in response to this impact and has caused a dot to be printed on the paper 12, the needle rebounds to the right, aided by energy stored in the spring 32.
• dot matrices including non-ballistic impact, ink squirting, electric discharge, and others, but ballistic systems are widely used in practice and will be used in the description of this invention.
• the invention is not limited to a bal ⁇ listic system.
• Fig. 4 is an enlarged drawing of only the jewel bearing 21 and the front ends 23a-23i of nine needles 19a-19i.
• the bearing 21 may be synthetic ruby and, in accordance with common practice, is divided into two mirror image parts 21a and 21b.
• the guiding surfaces for the needles 19a-19i are arcuate recesses 36a-36i in one edge of the bearing part 21a and corresponding arcuate recesses 36a'-36i' in the facing edge of the bearing part 21b.
• the diameters of the openings defined by each pair of recesses is slightly greater than the diameter of the needle guided by that pair.
• each of the recesses 36a-36i and 36a'-36i' is a semi ⁇ circular arc, but this would mean that the bearing ma ⁇ terial would taper down to zero width at the facing edges of the parts 21a and 21b. The material at such points would wear excessively, and so the arcs that define the recesses have been truncated to less than 180°. However, the arcuate surfaces that remain confine the needles 19a-19i sufficiently to prevent adjacent pairs of needles from rubbing against each other.
• each of the dots is determined approximately by the diameter of the needles, but the texture of the surface of the paper on which the dots are printed makes the shape and, to some extent, the size of the dots inexact.
• the contour of a dot as seen under a magnifying glass is likely to be rough, which makes it impossible to measure the diameter precisely.
• the size of each dot is also affected by the type, hardness, and thickness of the paper and the number of copies; the environmental conditions; the type of ribbon used and the ink on the ribbon; and other factors. These latter factors do not affect the dot size equally, and the most important factor is the diameter of the needle.
• each of the rows 37 and 38 appears to be a line about 0.35 mm wide, and the space between the two rows is about 0.39 mm
• the maximum height of a symbol printed by the 9-needle structure in Fig. 4 is, therefore, 0.37(N-l)mm + 0.36 mm, or about 2.94 mm but it contains, at most, five visibly separate rows of dots. If four additional needles were added so that seven rows could be printed, the maximum symbol height would be 5.6 mm, much greater than the size chosen by the Japanese government.
• Fig. 5. illustrates a geometrical analysis of a modified printing structure that makes it possible for at least seven horizontal rows to be printed in a space having a total height of 3.7 mm.
• a structure having N needles 41A, 41B...41(N-l) . 41N is arranged so that the needles are tilted at an angle - ⁇ - with respect to the horizontal.
• Two shaded lines 42 and 43 printed by the needles 41A and 41C, respectively, are indicated. These lines are illustrated as having constant width, but they actually consist of dots, just like the lines 37 and 38 i Fig. 3. All of the needles are of equal diameter D and the width of each line is defined as D, although the line width may actually be slightly different from the needle diameter.
• the width of the space 44 between the closest visibly separate lines 42 and 43 is defined as w.
• Fig. 5 shows a vertical overlap V between two adjacent needles 41(N-1) and 41N, and the same overlap exists between each adjacent pair.
• the total vertical distance between the centers of needles 41A and 41N is (N-1)(D-V) and the total height T of the tallest symbol that can be printed is:
• Equation (1) may be rewritten as either
• the width W is a
• the width W of a space 44 as a percentage of the width D of a line 42 is
• the vertical overlap V between any two adjacent needles, for example the needles 41A and 41B, will be approximately 0.09 mm.
• the space W between- two rows of dots, or horizontal lines, 42 and 43 printed by any pair o most closely adjacent needles in a first group of first needles comprising alternate needles 41A, 41C,... is approximately 0.17 mm, which is about 47% of the width of any line, for example, the line 42.
• the spaces, such as the space 44, between each pair of spaced horizontal rows can be filled in by printing dots with appropriate printing elements of a second group consisting of the elements 41B, 41D,..., each of which is capable of printing a row of dots centered between the two rows on each side and overlapping those rows.
• any two dots are to be printed in a vertical line in spite of the fact that the needles are offset as shown in Fig. 5, a delay time must be maintained between • the printing of such vertically aligned dots. If the vertically aligned dots are to be printed by next-adjacent needles 41A and 41B, the delay must be related to X cos - ⁇ , i.e. to the amount of horizontal offset, or displacement, between these dots. If it is the dots printed by the farthest apart needles 41A and 41N , the delay will be related to (N-l) X cos - ⁇ .
• the diameter of the needles 41A-41N need not be
• the corresponding, limiting minimum value of fr is a little less than 29°.
• the reason for selecting even numbers of needles 41A-41N, e.g. fourteen and eighteen, to produce seven or nine visibly separate lines of dots like the lines 42 and 43 is that many existing matrix printers use printing heads with seven or nine needles, and it is desirable to be able to utilize the mechanism of such existing machines with a minimum of revision. By simply tilting the existing seven needle or nine needle printing heads, or even just the jewel bearing, it is possible to use such heads to print approximately the upper or lower half of a symbol at a time. Alternatively, many symbols could be printed using just the lower set of dots.
• the paper may be fed just enough to cause the uppermost needle printing the top row of the bottom half of the symbols to fall exactly of the positions of the needle printing the bottom row of the top half of the symbols.
• the advantage of feeding the paper just that much less than half the maximum symbol height is that it causes the space W between the closest visibly separate lines of dots to be greater, e.g. W is approx ⁇ imately 0.06 mm for seventeen needles of 0.35 mm. di ⁇ ameter, each, but only about 0.04 for eighteen needles of the same size.
• the space 44 for a seventeen needle arrangement would be about 17% of the line width instead of about 11% for an eighteen-needle arrangement.
• the angle ⁇ - would be about 34°
• a printing arrangement in which the actual or effective number of needles is even is capable of printing only the same number of visibly separate lines as a printing arrangement having one less needle
• the extra needle allows one pair of the lines to be spaced farther apart than the other pairs. Any pair can be selected for such additional spacing, which may be of some benefit in adding to the legibility of the symbol.
• the value of W for needles having diameters of 0.35 mm is approximately equal to 0.20 mm., which is about 56% of the width of a line.
• the angle - ⁇ would be about 49°
• the relative vertical shift between the paper and the printing head should be NX Sln ⁇ . If t h e bottom row of the upper half 2 is to overlap, precisely, the top row of the lower half, the vertical shift shoul d be ( N-l ) X s i n ⁇ ⁇
• needles such as the needle 19 in Fig. 2
• the perpendicular distance through the axis of a needle from one surface to the opposite surface is re- ferred to as the diameter, even if the cylinder does not have a circular cross section. If the diameter is made much less than about 0.35 mm, the needle tends to be too flexible so that it may bend in response to the impact of the armature 26.
• Another advantage of offsetting the needles in accordance with this invention is that it becomes reasonable to reduce the diameter of the forward part of the needle adjacent the end 23 between the bearing 21 and the ribbon 24.
• Fig. 6 shows a needle 46 so modified.
• the forward cylindrical portion 48 has a lesser diameter, which may be 0.2 mm, or even smaller. This forward portion should be long enough to prevent the shoulder 49 from pressing the ribbon 24 (Fig. 2) against the paper 12, for example about 0.2 mm long. The diameter of the end 51 should not be so small that it will pierce the ribbon, and the portion 48 should be entirely forward of the bearing so that the shoulder 49 will never enter the bearing where it might rub on the bearing surface and cause excessive wear of that surface.
• the legibility of the printed symbols may be further enhanced.
• fourteen such needles producing dot diameters of about 0.26 mm will have no overlap V, even though their body diameters are 0.35 mm and their axes are spaced 0.37 mm apart.
• the space W will be approximately equal to the dot diameter and the angle 0 will be about 45°.
• the angle ⁇ has been calculated as if the printing apparatus included a delay line or other delay means capable of being set to any desired delay time. If the apparatus has no delay means as such, the printing of a vertical line of dots may be obtained by selecting the timing of the pulses that actuate the needles so that the pulses actuating any two needles to produce dots in a vertical alignment occur in the proper time relationship to do so. This time relationship must take into account the scanning speed of the printing head and the vertical distance between the two dots. If there is a fixed timing system for actuating the needles, it may be nec ⁇ essary to tilt the row of needles farther, which is the same as reducing the absolute value of the angle 0. Then, the needles must be spaced farther apart so that hori- zontal rows of dots printed by adjacent pairs of needles will not overlap excessively.
• Fig. 7A shows printing head 52 with two jewel bearings 53 and 54 mounted rigidly in a frame 56.
• the bearings may be divided into two parts similar to the parts 21a and 21b in Fig. 4, and they may be held in place by being clamped or otherwise fixedly held in the frame 56.
• the bearing 53 serves as a guide for nine needles 57a-57i
• the bearing 54 serves as a guide for an additional nine needles 58a-58i.
• the needles 57a-57i are actuated by solenoids 59a-59i in a support 61 rigidly attached to the frame 56.
• the needles 58a-58i are actuated by solenoids 62a-62i held in a support 63 that is also rigidly attached to the frame 56.
• the frame 56 is supported on rods such as the rod 16 in Fig. 1 to slide back and forth in the directions indicated by a double ended arrow 64.
• the bearings 53 are placed in the frame so that rows of dots printed by successive actuations of the needles 57a and 58i will either overlap each other exactly or will overlap only to the same extent as the overlap, if any, between each other adjacent pair of needles.
• the bearings 53 and 54 are also spaced apart a precise hori ⁇ zontal distance to permit a single symbol to be printed with all eighteen of the needles 57a-57i and 58a-58i, just as if all of the neeedles were in a single bearing. This makes it unnecessary to print the upper half (approxi ⁇ mately) of each symbol on the first scan of the printing head and the lower half (approximately) of each character during a second sweep.
• the paper similar to the paper 12 in Fig. 1, need not be fed less than a full line increment after each sweep. It need not be fed a small increment after alternate sweeps, and a slightly larger increment after the other alternate sweeps.
• Fig. 7B shows another embodiment similar to tha in Fig. 7A.
• a front bearing support 66 similar to the frame 56 and two jewel bearings 67 and 68 similar to the bearings 53 and 54 are shown.
• the electro magnetic actuating means are not shown, but can be identi ⁇ cal to the means 59a-59i and 62a-62i in Fig. 7A.
• the bearings 67 and 68 have needles 69a-69i and 71a-71i, respectively, supported in parallel vertical rows in them.
• the needles 69a-69i in the bearing 67 in Fig. 7B and the needles 71a-71i in the bearing 68 are spaced apart by a sufficient distance to permit any two next-adjacent needles, for example, the needles 69a and
• the needles 71a-71i are spaced the same distance apart as the needles 69a-69i but are offset vertically so that the level of the center of a row of dots printed by successive actuation of, for example, the needles 71a is midway between the levels of the centers of dots printed by the needles 69a and 69b.
• the dots printed by the other needles are spaced correspondingly.
• the horizontal spacing between the needles 69a-69i and 71a-71i requires delay means to effect printing of dots in vertical alignment from the two sets of needles.
• the bearings 67 and 68 may be spaced to accommodate any time delay, but preferably, the bearings 67 and 68, like the bearings 53 and 54 in Fig. 7A, are located as close together as possible, taking the rela ⁇ tively large cross-sectional areas of the actuating means 59a-59i and 62a-62i illustrated in Fig. 7A into account.

Applications Claiming Priority (2)

Publications (1)

Family

ID=25371218

Family Applications (1)

Country Status (9)

Families Citing this family (15)

Family Cites Families (4)

• 1979
  • 1979-02-14 IL IL56669A patent/IL56669A0/xx unknown
  • 1979-02-15 WO PCT/US1979/000092 patent/WO1979000627A1/en unknown
  • 1979-02-15 DE DE792936561T patent/DE2936561A1/de active Pending
  • 1979-02-15 GB GB7934748A patent/GB2035905B/en not_active Expired
  • 1979-02-15 BR BR7906616A patent/BR7906616A/pt unknown
  • 1979-09-11 EP EP79900244A patent/EP0009033A1/de not_active Withdrawn
  • 1979-10-12 DK DK432979A patent/DK432979A/da not_active Application Discontinuation
  • 1979-10-12 SE SE7908476A patent/SE7908476L/xx unknown
• 1980
  • 1980-11-27 FR FR8025589A patent/FR2477071A1/fr not_active Withdrawn

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events