US 3724631 A
An electronic printer employs a character drum on which the elements are arranged along helical paths, and are divided into a plurality of discrete, axially offset character groups. An impact member is aligned with each of the character groups, and enables printing during concurrent rotation of the drum and axial movement of both the drum and the hammers synchronously past the object to be printed.
Claims available in
Description (OCR text may contain errors)
United States Patent 11 1 Kaczeus 1541 PRINTER WITH HELICALLY ARRANGED TYPE nrvnmn INTO AXIALLY OFFSET GROUP Inventor: Steven L. Kaczeus, Chelmsford,
Assignee: Printer Technology, 1110., Woburn,
Filed: 'Jan. 15, 1971 Appl. No.: 106,850
US. Cl ..197/49, 101/93 c, 197/18 Int. Cl ..B4lj 1/22, B41j 1/32 Field of Search ..l0l/93; 197/55, 49,18
 References Cited UNITED STATES PATENTS 7/1958 Masterson ..l01/93 C [111 3,724,631 [451 Apr. 3, 1973 2,926,602 3/1960 MacDonald et al. ..101/93 C 3,331,316 7/1967 Bretti 197/] R 3,385,213 5/1968 Stephan ..101/110 3,406,625 10/1968 Chamness et 31.... .197/55 X 3,442,364 5/1969 Ragen ..197/49 3,599,772 8/1971 Comstock ..197/49 Primary Examiner-Edgar S. Burr Attorney-Peter L. Costas [5 7 ABSTRACT An electronic printer employs a character drum on which the elements are arranged along helical paths, and are divided into a plurality of discrete, axially offset character groups. An impact member is aligned with each of the character groups, and enables print-. ing during concurrent rotation of the drum and axial movement of both the drum and the hammers synchronously past the object to be printed.
11 Claims, 7 Drawing Figures .1055 2 1/ POSITION/N6 un/vs l l i PATENTEHAPR 3 I975 SHEET 2 UF 2 FlG.6
COMP 2 CPU BUS 1 w u hm K "L Mn Im f 5 7 G F COMP? 1 CTR PRINTER WITH IIELICALLY ARRANGED TYPE DIVIDEDINTO AXIALLY OFFSET GROUP BACKGROUND OF THE INVENTION In many instances, the maximum value is not realized in currently available computer, mini-computer, teleindicated by the indicating means, and the actuating ployed therein. Although high speed printers are available, their cost is often prohibitive or at least difficult to. justify, particularly in situations in which the output capacity that they provide greatly exceeds the overall capacity of the system. Moreover, such printers tend to be inappropriate for use in applications in which human memory and reading capacities are involved. On the other hand, in contemporary mini-computer systems the presently available low speed printers often constitute the most limiting factor, and tend to militate against efficient operation.
Accordingly, it is the primary object of the present invention to provide a medium speed electronic printer that is relatively inexpensive to produce.
A more specific object is to provide such a printer that is capable of printing at least 30 characters per second, preferably about 60 90 and most desirably about 80 120 characters per second.
It is also an object of the invention to provide a printer that is especially suited for'use in mini-computer systems, both in terms of output capacity and also in terms of cost. I
Another object is to provide a full character impact printer having, in addition to the foregoing advantages, the capability of producing a desirable final copy format.
It has now been found that the foregoing and related objects can be readily attained in an electronic character printer comprising a frame having means thereon for positioning an object to be printed along a linear printing path, and a character drum mounted on the frame for concurrent movement along the linear path and rotation about an axis parallel thereto. The drum has a multiplicity of character elements arranged .about the circumference thereof and along helical paths, which elements are divided into a plurality of discrete, axially ofr'set character sets each comprised of a plurality of discrete axially off-set character groups each provided by a multiplicity of character elements. Theprinter also includes a plurality of impact members mounted on the frame for synchronous movement along the linear path with the character drum. Each of the impact members cooperates with one of the character groups and is of a width substantially equal to the axial length encompassed by one of the character groups, and is aligned therewith to permit contact to be effected between any character element thereof and the object, for printing during such concurrent movement and rotation. The printer has means for continuously rotating the character drum and for moving the character drum and impact members along the linear path; means is also provided for dynamically indicating the angular relationship between the character elements of each of the groups and the impact member associated therewith. Means responsive to an electronic input signal representative of matter to be printed is also provided for actuating the impact members when a desired character for printing is aligned therewith, as
means actuates the impact members independently of one another and such that the impact members cooperating with those groups of characters which are axially aligned along the circumference of the drum are actuated prior to actuation of the impact members cooperating with the character ferentially therefrom.
lnaccordance with one embodiment, the charactergroups are substantially identical and each of them constitutes a character set. The angle of the helical paths, the character group off-set distance, and the rates of rotation and linear movement are interrelated in such a manner that the character elements of each of the groups sweep past only lln of the number of columns to be printed on the object, where n represents the number of character groups. In addition, each of the character sets extends incompletely about the drum circumference to provide circumferential spacing between the first and last character elements thereof.
Alternatively, a pair of character groups may provide a single character set, as a result of which the set will have two impact members associated with it. Preferably, the drum has a plurality of character sets thereon with the character groups arranged sequen tially about the circumference thereof. In such a case, the angle of the helical paths, the character group offset distance, and the rates of rotation and linear movement are so interrelatedas to cause the character elements of each of the sets to sweep past only 1/1: of the total-number of columns to be printed on the object, 11 representing the number of character sets on the drum. Most desirably, three character sets andsix of impact members are provided. The drum is advantageously substantially free of axial and circumferential spacing between the last character element of one of the groups and the first character element of another of the groups to which it is adjacent. Generally, a character set will contain 64 alphanumeric characters, and the printer will additionally include means furnishing ink to the object at the locations of contact with character elements.
In accordance with the method! of the invention, an object to be printed is positioned along a linear printing path, and a character drum is concurrently moved along the linear path and continuously rotated about an axis parallel thereto. The drum is provided with a multiplicity of character elements arranged about its circumference and along helical paths, and the elements are divided into a plurality of discrete, axially offset character groups. A plurality of impact members are moved synchronously'with the drum along the linear path and with the object therebetween. Each of the impact members is of a width substantially equal to the axial length encompassed by one of the character groups, and is aligned therewith to permit contact to be effected between any character element thereof and the object. The relationship between the character elements of each of the groups and the impact member associated therewith is dynamically detected, and an electronic signal representative thereof is generated. An electronic input signal representative of the matter to be printed is also generated, and the detecting signal and input signal are compared. The impact members are independently and non-sequentially activated in response to the signal comparison during such concurgroups spacedcircumrent movement and rotation, thereby effecting contact of the object and the character elements to reproduce the matter thereon. Preferably, contact of 60 90 character elements per second is effected with the object, and most desirably the rate of contact is 80 120 character elements per second.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a printer embodying the present invention;
FIG. 2 is a side elevational view of a character drum, printing hammers and inking roll which may be utilized in the type of printer illustrated in FIG. 1, and drawn to a scale that is slightly enlarged therefrom;
FIG. 3 is a front elevational view of the character drum of FIG. 1, drawn to a slightly enlarged scale to more clearly illustrate the character element arrangement thereon;
FIG. 4 is a fragmentary sectional view to an enlarged scale of an engagement mechanism for the printer carriage'assembly;
FIG. 5 is a schematic view of the developed surface of a second drum providing a single character set, and of a pair of cooperating printing hammers employed therewith, drawn to an enlarged scale;
' FIG. 6 is a schematic view of another developed drum surface and of printing hammers used therewith, the drum providing three discrete character sets that are axially offset from one another and have circumferential spacing between the first and the last elements thereof; and
FIG. 7 is a schematic view of an electronic logic design appropriate for use in the printer of FIG. 1.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Turning now in detail to FIG. 1 of the appended drawings, therein illustrated is a printer mechanism embodying the present invention and having a chassis providing side elements 10 between which are journalled a hexagonal shaft 12 and a worm shaft 14, parallel thereto. The hexagonal shaft 12 has a pulley 16 secured near one end and a timing wheel 18 at the opposite end thereof, and a character drum 20,having a hexagonal axial passageway 22 therethrough, is slidably mounted on the shaft 12 between the side elements 10 of the chassis. The drum 20 has a multiplicity of character elements 24 arranged along helical paths in six discrete axially offset groups A B A,, 8,, A and 8,, as is best seen in FIG. 3 and will be more fully described hereinafter.
' A hammer carriage assembly, generally designated by the numeral 25, is mounted upon the worm shaft 14 and includes a housing 26 supporting a multiplicity of hammers 28 therein. As is seen in FIG. 4, which illustrates a mechanism by which the carriage assembly 25 may engage the worm shaft 14, the housing 26 has a transverse bore 27 for the worm shaft 14, and an intersecting perpendicular bore 29 in which is seated a slidable pin 31. The upper surface of the pin 31 has a transverse notch 33 formed therein, and a short stud 35 projects downwardly from the pin 31 through an opening 37 in the housing 26. Pivotably mounted above the pin 31 on an axle 39 is a pawl 41 having a nose portion 43 that is urged by sprint 45 into engagement in the notch 33 of the pin 31, thus maintaining the pin 31 in retracted position against the force of coil spring 47 positioned therebehind. As will be apparent, pivoting the pawl 41 in a counter clockwise direction will disengage the nose portion 43 and permit spring 47 to thrust pin 31 into driving engagement in the groove 30 of the worm shaft 14. Disengagement of the pin 31 from shaft 14 is effected by pivoting the resetting arm 49 on the shaft 51 against the force of spring 53. This causes the arm 49 to bear against the stud 35 and return the pin 31 to a position for reengagement of the nose portion 43 in the notch 33.
A yoke 32 embraces the drum 20, and is secured to the carriage housing 26 by a flexible drive cable 34. The cable 34 is supported upon the chassis by four pulleys 36 which in turn are rotatably mounted upon corner posts 38. A coil spring 40 biases the carriage assembly 25 toward the left end of the chassis as depicted in FIG. 1, and a dashpot or shock absorber 42 is affixed upon the side element 10 adjacent to that end to prevent damaging impact upon return of the carriage assembly 25 under the force of the spring 40. The
printer also includes an electric motor 44 from the shaft 59 of which power is transmitted through a belt 46 to the hexagonal shaft 12 and the worm shaft 14 through the pulleys 16, 48 on the ends thereof, respectively.
Energization of the motor 44 causes the worm shaft 14 and the hexagonal shaft 12 (and consequently the drum 20) to rotate continuously. To commence printing, engagement between the carriage assembly 25 and the rotating worm shaft 14 is effected by release of the pin 31, in the manner described, which follows the groove 30 and thus causes axial movement of .the assembly 25 from left to right in FIG. 1. Through the cable 34 and yoke 32, the drum 20 moves axially with the carriage assembly 25 at precisely the same rate, and continuous rotation of the drum sequentially presents the character elements 24 thereon to the associated hammers 28 for printing, as will subsequently be described in detail. When the farthest extent of the carriage assembly 25 and drum 20 has been attained (near the right end of the printer) the resetting arm 49 is actuated to disengage the pin 31 and permit the spring 40 to return the mechanisms to the home position near the left end.
FIG. 2 shows one inking arrangement and best illustrates the individual raised character elements 24 of the printer. The paper 50 is positioned by conventional web positioning means 2 between the drum 20 and the hammers 28 which are aligned on a common axle 52 for pivotal movement toward the paper 50 and drum 20. The hammers 28 have enlarged heads 54, and foot portions 56 made of magnetic material and angularly offset relative to the axle 52 to best accommodate the magnetic coils 58 by which the hammers 28 are actuated. An inking roll 60 is rotatably mounted upon a shaft 62 that is parallel to shafts 12 and 52, and the roll 60 moves with the drum 20 and contacts the character elements 24 to provide ink thereto for transfer upon impact. It will be appreciated that this arrangement for inking would not be very appropriate with the mechanism shown in FIG. 1 because printing would thereby be produced from right to left on the page. With the particular printer illustrated, it is preferable to supply an inking ribbon 55 from spools 57 and convey it between the hammers 28 and paper 50. The impressions are thereby transferred from the drum through the rear of the paper 50 for reproduction on the front surface thereof.
With further specific reference to FIG. 1, it is seen that each of the enlarged heads or impact members 54 of the hammers 28 is substantially equal in width to the axial portion of the drum 20 that is covered by the character group (e.g. A A A B B or B that is associated with it; i.e., each head 54 is about one-sixth of the total length of the drum 20. As a result, each head 54 is capableof contacting all elements 24 of the character group with which it is aligned, and only those elements.
Appropriately interconnected (in a manner not shown) with the other elements of the printer is a schematically represented electronic logic system 64, used for information input and printout control. Normally, the electronic system 64 will cooperate with a computer or other central printing unit providing data input thereto, and the logic design will be more fully described hereinafter. m
The timing wheel 18 on the end of the hexagonal shaft 12 is provided with reference marks or strobes (not shown) indicative of the position of eachof the character elements 24 on the drum 20. The wheel may also have marks for other purposes, such as to enable tabulation of total revolutions of the drum for carriage return control and the like, or a second timing wheel may be provided'for that purpose. The wheel 18 passes through the field of a magnetic pickup head 66, which is connected to the system 64, to generate a signal for actuation of the hammers 28 when the character required in a particular column of the paper 50 is aligned therewith (as indicated by the signal from head 66). It will be appreciated that other means for detecting the relationship between the character elements 24 and the hammers 28 or heads 54 may be substituted, such as the optical code diskdevices known in the art. It will also be. appreciated that the arrangement of character elements 24 illustrated in FIG. 3 simplifies the timing wheel configuration since like elements of each character set are aligned and may all therefore be indicated by a single reference mark; however, other character arrangements may be employed advantageously. The limit switch 68 is actuated by the carriage assembly in the home position thereof, to permit the transfer of data through the electronic system 64 and the other parts of the printer.
As depicted in FIG. 1, the drum 20 rotates upwardly into the page of drawings while it moves axially from left to right. To compensate for the axial movement, it is necessary that the character elements 24 be arranged along a path that extends helically in the direction opposite to forward progression of the drum 20. This allows all elements of each character group to pass the same points across the page, and it will be appreciated that the proper helical angleis a function of the axial and rotational rates, and of the character group spacing. If movement was intermittent or at varying rates, the elements would have to be arranged along paths of different configurations for proper compensation.
As has been mentioned, the drum 20 employed in FIGS. 1 3 has six separate character groups (namely A A A B B and B each of which is associated with a single hammer 28. Each of the pairs of groups A,
and B A, and B and A and B, constitutes asingle alphanumeric series (normally of 64 or 96 characters) to provide three complete character sets on the drum 20, the groups A, and B being positioned to sweep every third column on the page (e.g., columns 2, 5, 8, l1 the groups A, and B, sweeping subsequent columns (e.'g., 1, 4, '7, 10 and A and B sweeping the remaining columns (e.g., 3, 6, 9, l2. In this manner a full alphanumeric character set is presented to each column of the page as the drum 20 progresses thereacross, and the speed of printing can be greatly increased because each of the sets need pass only one third of the columns. Moreover, due to the division of each set into two axially offset groups, the speed is further increased by elimination of any delay due to hammer responsiveness and cycle times. Thus, by so dividing the character sets the equivalent of l of blank space is provided for the resetting of each of the hammers between impacts, which is more than adequate recycle time, in thepresent state of the art. Although it might appear that even greater printing rates could be attained by dividing the sets into more than two groups, such is not the case in practice. The resultant speeds require very high rates of drum rotation, which in turn would impose intolerable centrifugal forces thereon. Secondly, although the contact time of the paper, character elements, and impact heads is very brief, unduly high speeds cause significant relative movement at the moment of contact, producing smudg'ing and loss of definition in the printed characters. in FIG. 5, a developed (i.e., showing the full 360 circumferential surface) drum 20' having only two character groups C, D is illustrated, the groups C and D constituting a single alphanumeric series. The carriage 25' supports two hammers-28', each of which has an impact head 54' spanning the axial length of the character group with which it is aligned. Although this embodiment does not offer the full scope of benefits previously discussed, the printing speeds attainable are considerably in excess of those that would be possible using a drum having the character set arranged along a single, continuous (not offset) helical path and associated with only one hammer. Thus the recycle time for the hammer must be accounted for in the latter instance, and although the lag is brief it imposes a significant limitation upon printing speeds. It will be appreciated that other character configurations than those illustrated may. be employed in accordance with the instant invention, such as configurations-providing two or four complete character sets about the drum circumference.
FIG. 6 illustrates another embodiment of the invention wherein the developed drum 20" has three axially offset character sets E, F and G thereon, cooperating with a carriage assembly 25" having three hammers 28" and associated impact heads 54'. The provision bf a plurality of character sets in accordance herewith permits increased printingrates because only a fraction of the total number of columns must be covered by each set. However, since only one hammer 28".
cooperates with each set of characters, the cycle time of the hammers must be considered,.thus rendering this arrangement less desirable than that illustrated in FIGS. 1 3 wherein both a plurality of character sets and also offset character groups comprising half a set are employed. Resetting time is accounted for in this embodiment by providing circumferential spaces h between the first character (A) and the last character (Z) in each alphanumeric set E, F and G. The worst possible case with such an arrangement would require the letter Z to be printed in one column, and immediately thereafter the letter A to be printed in the next; the space h provides a relief period for hammer resetting, making such an operation possible at the high speeds that are attainable due to the use of plural character sets.
It should be understood that operation of the printer herein described requires that the hammers be capable of independent and arbitrary or non-sequential actuation, since the character to be printed in a particular column will be presented thereto without regard to the position of the column relative to those in the same vicinity. To permit operation in such a manner, the computer, data terminal, telecommunication system or other central printing unit must be employed with logic design capable of producing such results. FIG. 7 of the drawings schematically illustrates an appropriate design for use with the printer of FIGS. 1 3.
Actuation of the limit switch (68 in FIG. 1) permits initial communication to occur between the printer and data supplier or central processing unit (CPU in FIG. 7). Upon every revolution of the drum 20 the. print mechanism, through the timing wheel 18 and pickup head 66, signals or flags the CPU of its availability for data input. The CPU thereupon serially transmits data, a character code at a time, to the input buffer registers A, B and C. Assuming, for example, the matter to be printed to be the word prints," the p code would go to register A, the r code to register B, and the 1' code to register C (hereafter only the letters themselves, rather than their codes, will be referred to). Upon transmission of the third character, the flag signal is removed to terminate data inflow.
A reference mark on the timing wheel 18 (which, along with the shafts l2 and 14 and the'drum 20 is con? tinuously rotating) actuates the engagement mechanism of the carriage assembly and causes it and the drum 20 to be driven axially thereby. A subsequent mark effects a shift of the data in registers A, B and C I to shift registers 10, 11 and 12 respectively, placing p in 10, r in 11 and iin 12. At this point, the character elements (a m) in the group designated A begin to sweep through the third column location on the page. Rotation of the timing wheel 18 generates pulses which are counted and stored in a six bit counter (CTR.) to indicate the presence of each character element as it becomes available for printing in column 3. During the first half 180) of the drum revolution the content of the CTR is compared with that of shift register 12 in the first comparator (COMP. 1). Since, in fact the character i is present in both register 1 and the counter (representative of an A character group), a signal is generated to activate solenoid A, and its associated hammer 28 to print the character in column 3 of the page. During the second half of the first revolution of the drum the character group B (containing elements n z) sweeps the second column location and BUS 1 switches the comparison in COMP. 1 to the CTR content and that of shift register 11. Since,once again, both the register compared and the counter (now representative of a B character group) contain a common character (i.e., r) solenoid B, is activated to print with the proper hammer 28 in column 2. Thus, after the first complete revolution the page bears the characters ri.
While this was happening, the previously mentioned flag is set and three more characters are stored in the buffer registers; i.e., n is stored in A, t is stored in B and s is stored in C, after which the flow of data is terminated. A reference strobe generated between the first and second revolutions shifts any remaining data in registers 10, 11 and 12 to registers 7, 8 and 9 respectively, and the data in the buffer registers to shift registers 10, 11 and 12 in the manner previously described. As a result, during the second revolution of the drum characters p, n, t and s are inregisters 7, 10, 11 and 12 respectively, registers 8 and 9 being vacant since the characters r and i were printed during the first revolution. During the first half of the second revolution character groups A; and A, sweep columns 6 and 1 respectively, the counter accumulates characters a m and comparators 1 and 2 compare the contents of shift registers 12 and 7 respectively. Since these registers contain only B group characters (i.e. in the latter half of the alphabet) no match is found and no printing occurs. However, during the second half revolution, while character group B sweeps column 5, the counter accumulates the B group characters and comparator l finds the character t in register 11; accordingly, solenoid B activates its associated hammer 28 and prints the character t in column 5.
1 At the beginning of the third revolution the data has been shifted so that p, n and s are in registers 4, 7 and 9, registers 10, 11 and 12 being vacant because the matter to be printed has been fully transmitted. During this revolution comparisons are made as hereinbefore described while groups A B A, and B sweep columns 9, 8, 4 and 3, respectively; no matches are found, and no printing therefore occurs. On the fourth revolution the data is shifted to place p in register 1 and n and s in registers 4 and 6. During the second half revolution, while groups 8;, and B, sweep columns 6 and 1 respectively, matches are found by both comparators 2 and 3. As a result, the characters p and s are printed in columns 1 and 6, and the page contains the characters prits. Thereafter, the character n shifts to register 1 and, while group B, passes column 4 a match causes the final character to be printed to complete the word.
The logic system will vary depending upon the number of character groups, the arrangement thereof and other factors to provide the proper firing order. Normally it will also include circuitry for carriage return, which may continuously monitor register A to detect the code for carriage return, which in turn may be generated by the counter after sensing an appropriate number of drum revolutions. Upon detecting such a code, a signal is generated to activate the release arm 49, to disengage the pin 31 from the shaft 14 and permit the spring 40 to return the carriage 25. In addition, another detector may detect a line feed code at the input, and fire a paper advance solenoid (not shown) to permit printing of a subsequent line. Such circuitry should be appropriately designed to prevent data flow when undesired, such as during carriage return, or to permit over-printing by delaying paper advance.
Although it is believed that the foregoing detailed description will enable those skilled in the art to readily practice the invention, perhaps it should be noted that the optimum overall dimensions for the type of character drum illustrated in FIGS. 1 3 are believed to be about 2.6 inches in diameter and 1.5 inches in width (axial length). These dimensions are thought to result in a weight/mass to volume ratio that is particularly desirable in a rotating drum of such configuration for a number of reasons, including the elimination of the need for an extensive and costly bearing set for absorption of hammer impact shock during printing. The drum impact surfaces are preferably plated with a hard metal such as chromium to enhance durability. However, an outstanding benefit attendant to the unique design features of the present printer, which minimize rotational speeds, g loadings and torques, is the potential for use of non-ferrous materials, which can often conveniently and inexpensively be molded.
Thus, it can be seen that the present invention attains the primary object thereof, namely the provision of a novel medium speed electronic printer that is relatively inexpensive to produce. Furthermore, the printer is capable of printing at least 30 characters per second, and of printing at the preferred and most desirable rates of 60 90 and 80 120 characters per second, respectively, thus overcoming limited throughput capability of prior art output devices and providing a printer that is especially suited for use in mini-computer systems. The invention provides a full character impact printer having, in addition to the foregoing advantages, the capability of producing a desirable final copy format, as well as providing a novel method of electronically printing at a medium rate, as is also an object of the invention.
Having thus described the invention, I claim:
1. In an electronic character printer, the combination comprising:
a. a frame having means thereon for positioning a web to be printed along a linear printing path;
. a character drum mounted on said frame for concurrent movement along said linear path and rotation about an axis parallel thereto, said drum having a multiplicity of character elements arranged about the circumference thereof and along helical paths, said elements being divided into a plurality of discrete, axially ofiset character sets each comprised of a plurality of discrete, axially offset character groups each provided by a multiplicity of character elements, each of said character sets extending about substantially the entire circumference of said drum;
. a multiplicity of impact members mounted on said frame for synchronous movement along said linear path with said character drum and equal in number to the total number of character groups cooperating therewith, each of said impact members being of a width substantially equal to the axial length encompassed by one of said character groups and being aligned therewith to permit contact to be effected between any character element thereof and the web, for printing during said concurrent movement and rotation;
(1. means for continuously rotating said character drum;
e. means for moving said character drum and impact members along said linear path;
f. means for dynamically indicating the angular relationship of the character elements of each of said groups and said impact member associated therewith; and
g. means responsive to an electronic input signal representative of matter to be printed for actuating said impact members when a desired character for printing is aligned therewith, as indicated by said indicating means, said actuating means actuating said impact members independently of one another with the impact members cooperating with groups axially aligned along the length of said drum being actuated prior to actuation of impact members cooperating with groups spaced circum ferentially therefrom.
2. The printer of claim 1 wherein said groups are substantially identical in the number and identity of characters; wherein the rates of rotation and linear movement are predetermined relative to the angle of said helical paths and the character group offset distance to cause the character elements of each of said groups to sweep past only l/n of the number of columns to beprinted on the web, where n represents the number of character sets; and wherein each of said groups extends incompletely about said drum circumference to provide circumferential spacing between the first and last character elements thereof.
3. The printer of claim 1 wherein a pair of said groups provides'a single character set, said set thereby having two of said impact members associated therewith.
4. The printer of claim 3 wherein said character groups are arranged sequentially about the circumference of said drum, with the rates of rotation and linear movement being predetermined relative to the angle of said helical paths and the character group offset distance to cause the character elements of each ofsaid sets to sweep past only 1/11 of the total number of columns to be printed on the object, where n represents the number of character sets.
5. The printer of claim 4 wherein there are three of said character sets and six of said impact members.
6. The printer of claim 5 wherein the last character element of one of said groups and the first character element of another of said groups of its set and to which it is adjacent are axially offset but contiguous to avoid substantial spacing therebetween, and each of said groups occupies of drum circumferential surface.
7. The printer of claim 3 wherein said character set contains 64 alphanumeric characters.
8. The printer of claim 1 additionally including means furnishing ink to the object at the locations of contact with said character elements.
9. In a printing method, the steps comprising:
a. positioning a web to be printed along a linear printing path;
b. providing a character drum having a multiplicity of character elements arranged about the circumference thereof and along helical paths, said elements being divided into a plurality of discrete, axially offset character sets each comprised of a plurality of discrete, axially offset character groups each provided by a multiplicity of character elements, each of said character sets extending about substantially the entire circumference of said drum;
c. concurrently moving said character drum along said linear path while continuously rotating said drum about an axis parallel thereto,
d. moving a multiplicity of impact members synchronously with said drum along said linear path and with said object therebetween, each of said impact members cooperating with one of said groups and being of a width substantially equal to the axial length encompassed by one of said character groups and aligned therewith to permit contact to be effected between any character element thereof and said web;
. dynamically detecting the relationship between the character elements of each of said groups and said impact member associated therewith and generating an electronic signal representative thereof;
f. generating an electronic input signal representative of matter to be printed;
g. comparing said detecting signal and said input signal; and
h. independently actuating said impact members in response. to said signal comparison during said concurrent movement and rotation to effect contact of said web with said character elements to reproduce said matter on said web, said actuation during a single rotation of said drum being of the impact members cooperating with character groups axially aligned along the length of said drum prior to actuation of impact members cooperating with groups spaced circumferentially therefrom.
10. The method of claim 9 wherein said impact members are actuated at a rate to contact 60-90 of said character elements per second with said web.
11. The method of claim 9 wherein said impact members are actuated at a rate to contact -120 of said character elements per second with said web.