Impact Line Printer

Abstract

A plurality of hammers are aligned laterally across a flexible sheet and are mounted on a support that is horizontally stepped a discrete number of step positions. A plurality of electromagnets, each associated with a single hammer, are mounted in a fixed position and are energized to cause the hammer to impact the flexible sheet. As the hammers are stepped back and forth, and as selected electromagnets are energized, the paper is stepped or advanced to result in a character being impact-printed on the sheet. Each character comprises a plurality of dots or marks arranged in a matrix.

Description

The present invention pertains to printers, and more particularly, to printers of the type referred to as line printers utilizing impact as a means for printing.

Prior art printers may be categorized in several ways, such as impact, non-impact, front or back striking impact, line, serial, etc. Serial printers can be relatively inexpensively constructed, but are generally very slow since they are limited to forming a single character at a time. Line printers, on the other hand, simultaneously form a line of characters and are generally high speed devices (500 lines or more per minute as opposed to 10 to 30 characters per second for serial printers). Line printers are usually very expensive and frequently utilize back striking techniques, such as found in drum printers where an electromagnetically driven hammer drives paper and ribbon onto a font formed on the surface of a drum.

Non-impact printers are limited to single copies and usually are further limited to the use of special papers. Such techniques as electrostatics or thermo papers are frequently used.

Printers for use with communication lines must have a speed capability commensurate with communication line information speeds. Present communication line technology provides information speeds (1,200 Baud and up) which exceed the capabilities of the inexpensive printers, thus demanding the higher speed printers which are extremely expensive in view of the inefficient utilization of the high speed printer capabilities.

It is therefore an object of the present invention to provide a printer capable of printing at communication line speeds while remaining much less expensive than prior art high speed printers.

It is a further object of the present invention to provide a printer utilizing impact techniques having communication line speed capabilities through a novel arrangement to simultaneously form a line of print.

It is still another object of the present invention to provide an impact line printer that utilizes both the advantages of front striking and back striking.

It is still another object of the present invention to provide an impact line printer that forms characters through the utilization of a matrix wherein each character is a result of multiple impacts.

These and other objects of the present invention will become apparent to those skilled in the art as the description thereof proceeds.

The present invention may be described by reference to the accompanying drawings, in which:

FIG. 1 is a pictorial view of an impact line printer constructed in accordance with the teachings of the present invention, showing the compactness available through the utilization of the present design.

FIG. 2 is a schematic block diagram illustrating information and control flow through the apparatus of the present invention.

FIG. 3 is a perspective view, partly in section, of a portion of the apparatus constructed in accordance with the teachings of the present invention.

FIG. 4 is an enlarged perspective view of a hammer for use in the apparatus of the present invention.

FIG. 5 is a cross-sectional view of a portion of the apparatus of the present invention, showing the relative positioning of the platen, flexible sheet of paper, ribbon, hammer, and the electromagnet.

FIG. 6 is a diagram of a typical character, greatly enlarged, printed by the system of the present invention.

FIG. 7 is a perspective view, partly in section, of a portion of the apparatus of the present invention useful in illustrating the paper feed mechanism and relationship of the paper or flexible sheet to the hammers and ribbon.

FIG. 8 is a top view of a portion of the apparatus of the present invention useful in the description of the relationship between the hammer and hammer support and the frame of the printer.

Referring now to FIG. 1, the printer mechanism is enclosed within a housing 10 which may take a variety of forms which are relatively compact. The system of the present invention may be a front feed type printer as shown wherein a flexible sheet or paper 11 is fed into the front of the machine, is printed upon, and exits through the center of the top of the housing and passes over the rear of the machine. Control switches 12 are conveniently placed by manual actuation while the paper may manually be advanced through the provision of pegs 14 extending through an opening 15 in the side of the housing 10. The pegs 14 are secured to a paper drive sprocket as will be described more fully hereinafter.

Referring to FIG. 2, information and control flow may take a variety of forms depending on the particular application of the present printer system. Typically, incoming data and coded control information will be supplied to a data storage facility 20 through a control facility 24 for subsequent printing. The data is by bits and may be serial-forming single input line or parallel-forming multiple input lines. The information in the data storage 20 is initially placed in an input buffer and subsequently dumped into a print buffer, thereby freeing the input buffer to receive subsequent input information. The logic and controls utilized in the system may take any of a variety of present state of the art approaches and do not form a part of the present invention. The data stored in data storage 20 is printed by energizing selected hammer solenoids 21, then moving the hammers to the next subsequent step position by energizing a hammer stepper 22. The selected hammer solenoids are again then energized until all of the step positions have been passed. A paper feed motor 23 is then energized and the paper is advanced and the process repeated. The timing and control of the energization of the hammer solenoids 21, paper feed control 23, and hammer stepper 22 are provided by control circuitry 24.

Referring now to FIGS. 3-8, a plurality of hammers 30 are aligned with each other and are mounted in a hammer support 32. In the embodiment chosen for illustration, the hammers are mounted in the support 32 by clamping the respective hammers between opposed faces of clamping bars 34 and 36, the latter being an extension of support 32. The hammers 30 are formed from appropriate steel to provide the facility to be drawn away from the paper surface, to be released, and to snap forward to strike the paper and return to its original position. The hammers may also be stamped from a single sheet of metal with each of the individual hammers forming fingers in comb-like fashion from a base which is clamped between clamping bars 34 and 36. With reference specifically to FIG. 4, each of the hammers is provided at the upper portion thereof with a striking surface 38 that is formed into a rectilinear edge extending, when the hammer is mounted in the printer, perpendicularly. The utilization of an edge as the striking surface 38 facilitates the production of dots or marks in the matrix of a character, as will be described more completely hereinafter.

A platen 40 comprises a horizontally extending edge functioning as a striking surface. The platen is gripped in a clamp 42 and is held in a position opposite to the striking surface 38 of the respective hammers 30. Flexible sheet material such as paper upon which characters are to be formed is fed through the printer as shown in FIG. 7 on a pair of sprockets 46-48 engaging sprocket holes 50 provided in the paper. A conventional ink ribbon 52 is wound about a feed roll 54 and passes over guides 56 and 58 to take-up roll 60. It may be noted that the ribbon 52, as it passes from guide 56 to guide 58, is inclined to horizontal or with respect to the aligned hammers 30. In this manner, the entire width of the ribbon is utilized since each hammer 30 is positioned to strike a portion of the ribbon unused by preceding hammers. Electromagnets are provided for each of the hammers 30. To more clearly illustrate the elements of the present invention, the individual electromagnets have been eliminated from FIGS. 3, 7, and 8; however, an electromagnet 62 is shown in FIG. 5 positioned adjacent its corresponding hammer 30. The electromagnets may be secured to the frame 64 (FIG. 8) of the printer if it is desired that they remain stationary. Horizontal motion of the electromagnets may be provided to more closely follow lateral hammer motion when an increase in said motion is desired.

The hammer support 32 is also secured to the frame 64 but is mounted to permit lateral or horizontal back and forth stepping. The movable mounting is provided by a plurality of two-dimensional semi-flexible straps 66 clamped at one end thereof to an upright 68 extending from the hammer support 32. As shown in FIG. 8, the opposite ends of the straps 66 are attached to the frame 64. Each of the straps 66 is made of spring steel which permits two-dimensional flexure perpendicular to the face of the strap while inhibiting flexure in any other direction. The mounting of the hammer support 32 in this fashion securely fixes the hammers at a predetermined vertical position while nevertheless permitting the hammer support 32 and hammers 30 to be moved laterally of the paper 44. This lateral movement is indicated in FIG. 8 by the arrow 69. Lateral motion is imparted to the hammer support 32 and hammers 30 by a stepping motor 70 connected to the hammer support 32 by a two-dimensionally, semi-flexible strap 72. While other means may be utilized to connect the hammer support to the stepping motor 70, the strap 72 readily translates the rotary motion of the stepping motor shaft 74 into rectilinear motion and permits the stepping action of the motor 70 to simply and positively "step" the hammer support 32 and hammers 30.

The stepping motor 70 is reversible and is stepped to a number of step positions corresponding to the number of horizontal dot or mark positions in the matrix forming a character. A mechanical stop 76 may be provided to engage the clamp extension 78 secured to the motor shaft 74.

The paper 44 is advanced through the utilization of a second stepping motor 80 which is connected through gears 81 and 82 to sprockets 46 and 48. The selected energization of stepping motors 70 and 80 combined with the energization of appropriate electromagnets 62 generate a matrix of step positions for the formation of characters.

The operation of the printer of the present invention may now be described with the aid of FIG. 6. In FIG. 6, a character "7" is shown and is formed by the selective printing of marks or dots in a matrix. In the embodiment chosen for illustration, a seven by eight matrix has been chosen; it will be obvious to those skilled in the art that a greater or lesser number of step positions may be utilized in accordance with the requirements of the specific application.

Referring to FIG. 6, the horizontal or lateral step positions are designated step positions x1, x2, ..., x7, while the vertical step positions have been designated y1, y2, ..., y8. Assuming that the character 7 is to be printed, the paper 44 will be stationary and dot or mark position x1, y8 will be between the striking surface of the platen 40 and the hammer 30. The electromagnet 62 will be energized and subsequently de-energized, causing the hammer to be drawn away from the paper and then released. The momentum of the hammer will cause it to strike the ribbon 52 and force it against the paper 44 and both the paper and ribbon against the platen 40. Since the striking surface 38 of the hammer 30 is oriented at right angles to the edge of the platen 40, a relatively small mark or dot 85 will be formed. The stepper motor 70 will then be energized and the hammer 30 moved to the horizontal step position x2. The electromagnet will again be energized and the hammer and platen will form the mark 86 in position x2, y8. The stepping motor 70 will continue to step, causing the hammer support 32 and hammers 30 to step to successive step positions until the hammer reaches horizontal step position x7. After the mark is printed at that position, the stepping motor 80 will be energized, causing the paper 44 to be slightly advanced. Vertical step position y7 is now aligned between the striking surface of the hammers and platen. The stepping motor 70 will again be energized in the reverse direction, causing the hammers to step to the left as shown in FIG. 6 with the hammers being energized at the appropriate step positions for the formulation of the character 7. The hammers therefore continue to step back and forth laterally or horizontally across the paper 44 with the electromagnet associated with the hammer energized at the appropriate times. At the end of each horizontal sweep from left to right or right to left, the paper is advanced or stepped to bring the next row of mark positions in the matrix into striking position between the hammers and platen. It may be noted that only one electromagnet energizes a given hammer regardless of the hammer position; thus, while the hammer support and hammers are stepped or oscillated back and forth, the electromagnets associated with each hammer remain stationary. While the hammers are then sometimes slightly misaligned with their corresponding electromagnets, they nevertheless remain within the area of influence of that electromagnet to the extent that the hammer is actuated by the energization and de-energization of its corresponding electromagnet. Since the electromagnets remain stationary, the mass that is accelerated and decelerated during the stepping action of the hammers is greatly reduced and the speed with which the hammers may be stepped is increased correspondingly. The use of the semi-flexible straps 66 greatly reduces friction that otherwise would occur if the hammer support were guided by more conventional means, such as rollers, sliding guides, etc. Further, the tolerances are very inexpensively but accurately maintained through the utilization of the straps 66. Similarly, the strap 72 used by transmitting the stepping motion to the hammers eliminates problems that otherwise would occur with more conventional motion transmitting media, such as the imprecision of chain drives or the backlash of rack and pinions. It may therefore be seen that the present invention provides a unique printing system incorporating the advantages of line impact printing while utilizing a matrix approach to the formation of characters.

Claims

We claim:

1. In a printer for printing characters on a flexible sheet having means for intermittently advancing said flexible sheet as characters are printed thereon, each of said characters being formed by printing a plurality of small dots at desired intersections of a discrete number of columns and rows, the improvement comprising: a frame; a plurality of hammers each carrying a striking means for printing a dot and aligned with each other and mounted on a hammer support; means movably securing said hammer support to said frame with said hammers adjacent said flexible sheet; a stationary platen positioned opposite said hammers and on the opposite side of said flexible sheet; stepping means connected to said hammer support to step said support and hammers a discrete number of step positions across said flexible sheet for aligning each hammer with one of said columns, said discrete number of step positions being equal to the number of columns used to form one of said characters; a plurality of electromagnets immovably secured to said frame, each positioned to actuate, when energized, only a respective one of said hammers when said respective hammer is in any of said step positions; and means for selectively energizing said electromagnets.

2. The combination set forth in claim 1, wherein said stepping means is reversible to step said support and hammers a discrete number of step positions back and forth across said flexible sheet.

3. The combination set forth in claim 1, wherein said stepping means comprises a rotatable stepping motor having one end of a semi-flexible strap secured to the motor shaft and another end secured to said hammer support.

4. The combination set forth in claim 1, wherein said hammers are drawn toward said electromagnets and are released to strike said sheet upon energization and de-energization respectively of said electromagnets.

5. The combination set forth in claim 1, including a plurality of two-dimensionally, semi-flexible straps secured to said frame and to said hammer support, each of said plurality of straps positioned to flex and to permit horizontal movement of said hammer support and to prevent vertical movement of said hammer support.

6. A printer for printing characters on a flexible sheet having sheet stepping means for vertically advancing said flexible sheet as characters are formed thereon, each of said characters being formed by printing a plurality of small dots at desired intersections of a discrete number of columns and rows, comprising: a frame; a plurality of hammers each carrying a striking means for printing a dot and aligned with each other and mounted adjacent said sheet on a hammer support; a stationary platen positioned opposite said hammers and on the opposite side of said flexible sheet; each of said hammers, when actuated, forming a dot on said sheet by striking said sheet; means movably securing said hammer support to said frame, said support being horizontally movable with respect to said sheet; hammer stepping means connected to said hammer support for horizontally stepping said support in one direction to a predetermined number of step positions for aligning each hammer with one of said columns, said discrete number of step positions being equal to the number of columns used to form one of said characters; said hammer stepping means being reversible when said sheet stepping means has vertically advanced said sheet to step said hammer support in an opposite direction to said predetermined number of step positions; a plurality of electromagnets immovably secured to said frame, each positioned to actuate, when energized, only a respective one of said hammers when said respective hammer is in any of said step positions; and means for selectively energizing said electromagnets.

7. The combination set forth in claim 6, wherein said stepping means comprises a rotatable stepping motor having one end of a semi-flexible strap secured to the motor shaft and another end secured to said hammer support.

8. The combination set forth in claim 6, wherein said hammers are drawn toward said electromagnets and are released to strike said sheet upon energization and de-energization respectively of said electromagnets.

9. The combination set forth in claim 6, wherein the striking means of each of said hammers comprises an edge extending in a predetermined direction, said hammers positioned on one side of said flexible sheet; said stationary platen having a striking surface comprising an edge extending perpendicular to said predetermined direction; said hammer striking surface and said platen striking surface positioned relative to each other to form a dot on said sheet at an intersection of their respective striking surfaces when they are forced together with said sheet therebetween.

10. The combination set forth in claim 9, wherein the striking surfaces of said hammers are vertically extending rectilinear edges.

11. The combination set forth in claim 10, wherein the striking surface of said platen comprises a horizontally extending rectilinear edge.