GB1582690A

GB1582690A - Printing apparatus

Info

Publication number: GB1582690A
Application number: GB2253078A
Authority: GB
Original assignee: NCR Corp
Current assignee: NCR Voyix Corp
Priority date: 1977-06-13
Filing date: 1978-05-25
Publication date: 1981-01-14
Also published as: JPS546622A; FR2394401B1; FR2394401A1; CA1096234A; DE2825527C2; DE2825527A1

Description

(54) PRINTING APPARATUS (71) We, NCR CORPORATION of Dayton in the State of Ohio, and Baltimore in the State of Maryland, United States of America, a corporation organized under the laws of the State of Maryland, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to a printing apparatus of the kind including support means adapted to support a plurality of elongated printing elements for lengthwise movement therethrough and driving means adapted to drive said elements to effect printing.

Such printing apparatus find application in wire matrix printers wherein characters are printed in the form of a plurality of dots produced by the impact of elongated printing wire elements with a record medium, in conjunction with an ink ribbon.

One problem which has arisen in con nection with use of printers of the wire matrix type is that of wear of the end bearing which is located near the printing end of the matrix printer and through which the print wires extend and from which they protrude when in a printing position. In order to reduce or eliminate such wear, various means have been employed in prior art structures, such as the use of end bearings made of synthetic sapphire or other very hard materials to limit end bearing wear. However, this method is quite costly and results in ex cessive wear of the print wires. In another prior art structure, means are provided for lubricating the wires where they pass through the bearing.However, this introduces an additional element into the structure, increasing the cost and complexity of the assembly, and also results in inconvenience in the necessity for periodic replenishment of the lubricant.

It is an object of the present invention to provide a printing apparatus of the kind specified wherein the above disadvantages are alleviated.

Thus, according to the invention, there is provided a printing apparatus including a plurality of elongated printing elements arranged to be driven lengthwise to effect printing, and a frame in which are mounted an end bearing means having a plurality of printing element receiving apertures disposed therein, and a plurality of support members spaced apart along the lengths of said printing elements and disposed on that side of said bearing means remote from the printing ends of said printing elements, each support member having a plurality of printing element receiving apertures disposed therein in such a manner that said printing elements each extend through corresponding apertures of said support members and said bearing means, wherein the pattern of apertures in said support member is so arranged as to accomplish translation of said printing elements from a generally circular pattern at the support member furthest from said bearing means into an essentially linear pattern at the support member nearest to said bearing means the pattern of apertures in the support member nearest to said bearing means being identical to, and having the same orientation as, the pattern of apertures in said bearing means.

Preferably, the support member nearest to the bearing means is loosely mounted in the frame to provide a degree of freedom of movement in a plane transverse to the direction of movement of the printing elements. This facilitates the alignment of the printing elements.

The frame in which the support members are mounted is preferably elongated and its longitudinal axis is parallel to the paths of movement of the printing elements between the bearing means and the support member nearest thereto. In such an arrangement the centres of the support members may be substantially on the longitudinal axis of the frame.

In order that the invention be better understood an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a sectional view of a printing apparatus in accordance with the present invention Fig. 2 is an elevation view, partly broken away showing the frame and the elongated printing elements of the printing apparatus; Fig. 3 is an enlarged cross-sectional view taken along line 3-3 of Fig. 2; Fig. 4 is an enlarged cross-sectional view taken along line 4-4 of Fig. 2; Fig. 5 is an enlarged cross-sectional view taken along line 5-5 of Fig. 2; Fig. 6 is an enlarged cross-sectional view taken along line 6-6 of Fig. 2; Fig. 7 is a bottom view of the frame of Fig. 2, taken along line 7-7, showing the end bearing; and Figs. 8A to 8E inclusive are enlarged partial sectional views showing the printing end of the printing apparatus and illustrating the manner in which an elongated printing element coacts with the end bearing under various conditions.

Referring now particularly to Fig. 1 of the drawings, a print head 10 of the wire matrix type is shown. A frame 12 is provided to support a plurality of elongated printing elements or print wires 14, only two of which are shown, for purposes of simplification and ready understanding of the drawings. Each wire 14 has a cap 16 which may be made of plastics or other suitable material, attached to its impactreceiving end to enlarge the area of the impact receiving surface. Each wire 14 also has a spring 18 disposed at its upper end, which exerts a force upon the cap 16 to resiliently bias the wire relative to the frame 12. The spring 18 has been omitted from one of the wires of Fig. 1, in order that the cap 16 may be more clearly depicted.

The frame 12 includes three side walls 20, 22, 24, a print end member 25 (also shown in Fig. 7) and an upper end member 26 (also shown in Fig. 3). A first print wire support member 27 (also shown in Fig. 6) is loosely mounted in grooves in the walls 20, 22, 24 close to the print end member 25, to permit the member 27 to shift laterally with respect to the frame in a plane substantially perpendicular to the longitudinal axis of the frame, and which is parallel to the direction of relative movement between the print head 10 and the record medium, which is to be printed upon by said print head. Two intermediate support members 28 (also shown in Fig. 5) and 29 (also shown in Fig. 4) are positioned in grooves in the side walls 20, 22in planes parallel to the plane of the support member 27.The support members 28 and 29 are not intended to move laterally with respect to the frame, and thus fit relatively tightly within their respective grooves.

The members 26, 27, 28, 29 constrain the various print wires 14 in predetermined paths, and accomplish the translation of the wires from a generally circular formation at the left end as seen in Fig. 1 to a linear formation at the printing end, and also cause the print wires to move into an essentially planar relationship perpendicular to the direction of relative movement between the record medium and the print head, becoming substantially coincident with a plane through the center line of the print head at a point slightly to the left of the member 27, as seen in Fig. 1, and to continue in such planar relationship through the member 27 and the bearing 36 positioned in the print end member 25.

The translation is accomplished by passing each wire 14 through a separate hole 30 in the upper end member 26, through similar holes 31, 32, 33 in the members 29, 28, 27 and into a defined position in the bearing 36. The members 27, 28, 29 and the apertures therein are positioned so that the paths of movement of the wires 14 are completely determined thereby, ancl the pattern of apertures in member 27 and bearing 36 is identical. Thus, theoretically, the apertures in the end bearing 36 do not determine the paths of the wires 14 therethrough, and there would be no side loading whatever of the wires thereby.

Actually, there may be some slight deviation from the ideal plotted paths of the wires 14, and thus some slight side loading.

The bearing 36 is of a material which resists wear and has a low coefficient of friction.

A pair of mounting flanges 38 and 40 extend laterally from the upper ends of sidewalls 20 and 22. The frame 12 is circular in cross-sectional shape to the left of flanges 38, 40 as seen in Fig. 1, and tenninates in the upper end support member 26 which is of circular configuration.

An apertured post 42 extends from the member 26 and provides means for assembling the driving means for the wires 14 to the frame 12, as will subsequently be described in greater detail.

As shown in Fig. 1, a plate 44 is provided with a central aperture 46 and is secured to the flanges 38, 40 on the frame 12 by suitable fastening means 48. The cir cular portion of the frame 12 extends through the aperture 46. A plurality of holes 50 are provided in the plate 44 for mounting a corresponding plurality, nine in the illustrated embodiment, of actuating means for the wire printing elements 14.

A coil 52, a center pole 54, and "L" shaped outer pole 56 and an armature 58 form the electromagnetic actuating means used in the print head. An armature shim 59 spaces the armatures 58 away from the poles 54 for the purpose of effecting faster armature release. A bore 60 is provided in the horizontal leg of the "L" shaped outer pole 56 for receiving the lower extremity of the center pole 54.

A unitary connector 62 is mounted by means of a screw 64 and a washer 66 to the post 42 of the frame 12. The connector 62 has a circular central portion 68 with an annular groove 70 provided in its bottom surface. An O-ring 72 is inserted in the groove 70 to act as a shock absorber and to provide a reference surface for the cap 16 of the print wire 14 striking the end of the armature 58. Nine arms 74 are formed integral with the central portion 68 of the connector 62 and extend therefrom.

Each arm 74 has associated with it a first armature receiving structure 76 and a second armature receiving structure 78.

One end of each armature 58 is received and held in place by the structure 76 and the other end of each armature is received and guided by the structure 78. With the connector 62 installed in the position shown, the arms 74 apply forces to the cantilevered distal ends of the armature, causing their print wire impacting ends to rotate about the fulcrum formed by the top edge of the pole 56 and upwardly into engagement with the O-ring 72. The caps 16 associated with the print wires 14 are maintained in contact with the ends of the armatures 58 by means of the forces applied by the springs 18.

The unitary connector 62 serves a number of functions in the assembly and operation of the print head 10, including retaining the armatures 58 in proper relationship to the remainder of the structure, acting as a biasing means for the armatures, providing means for adjusting the air gap between the armatures 58 and the corresponding center poles 52, forming a reference surface for the armatures 58 and print wire caps 16, to assure that all actuated print wires 14 impact the record medium at substantially the same time during a printing cycle, and, by means of O-ring 72, absorbing energy from the armatures 58 and the print wires 14 on return motion after actuation.

Characters such as numbers, letters or symbols are generated by the print head by a sequence of print cycles. Selective actuation of predetermined combinations of print wires 14 through energization of their corresponding coils 52 during each cycle results in the formation of the de sired character on the record medium, with the print head being shifted one position with respect to the record medium after each cycle to be properly located for the next printing cycle.

When a coil 52 is energized, a magnetic flux is created which causes armature 58 to be drawn into contact with center pole 54. The movement of armature 58 transmits energy into print wire 14, causing it to move in an axial direction in the frame 12. The force imparted into the wire 14 causes it to move against the spring 18 and its inertia causes it to continue to move downwardly out of contact with the armature 58 after said armature bottoms out against the center pole 54. The impactdelivering end of the print wire 14 extends beyond bearing 36 and strikes the record medium, causing a dot to be imprinted.

The energy stored in the moving print wire 14 is partially absorbed by the impacted record medium and is partially returned to the print wire 14, aiding the spring 18 in returning the print wire 14 to its rest position.

At approximately the same time that the print wire 14 is impacting the record medium, the coil 52 is deenergized. The moment exerted on the armature 58 by the arm 74 causes it to rotate away from the center pole 54 and to return into contact with the O-ring 72.

Examination of the curved path of movement of a typical print wire above the end bearing in a conventional matrix print head shows that the end bearing, such as a bearing 100 of a print head 102, shown in a new, unused condition in Fig. 8A must supply a side load to the print wire 104 in order properly to locate said wire, and must also supply a moment to said wire to insure that it exits the end bearing 100 in a direction parallel to the center line of the print head 102. As the aperture in the end bearing 100 wears, the print wire 104 continues to exert pressure to the left on the upper portion of said aperture and to the right on the lower portion of said aperture, as seen in Fig. 8B, and thus continues to apply a side load to the bearing.

When the wire 104 extends forward to print, and engages the record medium 106, or a platen supporting it, or a ribbon associated therewith, the motion of the print head 102 relative to the record medium 106 results in a very heavy side load on the bearing, as shown in Figs. 8A and 8B.

It is this heavy side load, caused by the transverse translation of the print head, that causes excessive bearing wear. With a conventional curved wire path, this situation continues throughout print head life because the static side load and the moment hold the print wire against the side of the hole in the end bearing even after considerable wear has occurred, as may readily be seen in Fig. 8B.

The present invention provides a means for routing of print wires that eliminates substantially any static side loading or moments from the end bearing. Referring to Fig. 1, it will be seen that the support members 27 and 29 supply loads such that with an appropriate deflection at an appro priate longitudinal location at the support member 28, the wire deflects in such a manner that it becomes coincident with a plane through the center line of the print head slightly to the left of the support member 27. If the pattern of apertures 33 of support member 27 (Figure 6) is the same as that of the apertures in the end bearing 36 (Fig. 7), the result is that no static side loads or moments are imparted to the wires 14 by the end bearing 36.

When the print head 10 of the present invention is new, a condition of heavy side loading due to the relative motion between the head 10 and the record medium 106, or the platen supporting said record medium, still occurs, and therefore wear of the end bearing 36, as shown in Fig. 8C, takes place in a manner similar to that shown in Fig. 8B for the conventional orientation of the print wire 104 with re spect to the end bearing 100. However, after a period of time, since the perpen dicularly oriented print wire 14 is not loaded at the end bearing, it no longer rests against the side of the hole.Thus, as the amount of enlargement of the aperture due to wear, designated by distance "d" in Fig. 8D, approaches and equals the transverse translation distance of the print wire 14 caused by its movement with respect to the record medium 106, said distance being designated as "b" in Fig. 8E, the side load due to the relative motion of the print head 10 and the record medium 106 ceases, as shown in Figs. 8D and 8E, and further wear ceases, since the translation distance of the print wire 14 will not increase beyond a predetermined maximum.

WHAT WE CLAIM IS: - 1. A printing apparatus including a plurality of elongated printing elements arranged to be driven lengthwise to effect printing, and a frame in which are mounted an end bearing means having a plurality of printing element receiving apertures disposed therein, and a plurality of support members spaced apart along the lengths of said printing elements and disposed on that side of said bearing means remote from the printing ends of said printing elements, each support member having a plurality of printing element receiving apertures disposed therein in such a manner that said printing elements each extend through corresponding apertures of said support members and said bearing means, wherein the pattern of apertures in said support members is so arranged as to accomplish translation of said printing elements from a generally circular pattern at the support member furthest from said bearing means into an essentially linear pattern at the support member nearest to said bearing means, the pattern of aper tures in the support member nearest to said bearing means being identical to, and having the same orientation as, the pattern of apertures in said bearing means.

2. An apparatus according to Claim 1, wherein the support member nearest to said bearing means is loosely mounted in said frame to provide a degree of freedom of movement in a plane transverse to the direction of movement of said printing elements.

3. An apparatus according to either Claim 1 or 2, wherein said frame is elong ated and its longitudinal axis is parallel to the direction of movement of said printing elements between said bearing means and the support member nearest to said bearing means.

4. An apparatus according to Claim 3, wherein the centres of said support members lie substantially on said axis of said frame.

5. An apparatus according to any one of the preceding Claims, wherein said printing elements are print wires.

6. An apparatus according to Claim 5, forming a printing head of a wire matrix printer.

7. A printing apparatus substantially as hereinbefore described with reference to Figs. 1 to 7 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

transverse translation of the print head, that causes excessive bearing wear. With a conventional curved wire path, this situation continues throughout print head life because the static side load and the moment hold the print wire against the side of the hole in the end bearing even after considerable wear has occurred, as may readily be seen in Fig. 8B.

The present invention provides a means for routing of print wires that eliminates substantially any static side loading or moments from the end bearing. Referring to Fig. 1, it will be seen that the support members 27 and 29 supply loads such that with an appropriate deflection at an appro priate longitudinal location at the support member 28, the wire deflects in such a manner that it becomes coincident with a plane through the center line of the print head slightly to the left of the support member 27. If the pattern of apertures 33 of support member 27 (Figure 6) is the same as that of the apertures in the end bearing 36 (Fig. 7), the result is that no static side loads or moments are imparted to the wires 14 by the end bearing 36.

When the print head 10 of the present invention is new, a condition of heavy side loading due to the relative motion between the head 10 and the record medium 106, or the platen supporting said record medium, still occurs, and therefore wear of the end bearing 36, as shown in Fig. 8C, takes place in a manner similar to that shown in Fig. 8B for the conventional orientation of the print wire 104 with re spect to the end bearing 100. However, after a period of time, since the perpen dicularly oriented print wire 14 is not loaded at the end bearing, it no longer rests against the side of the hole.Thus, as the amount of enlargement of the aperture due to wear, designated by distance "d" in Fig. 8D, approaches and equals the transverse translation distance of the print wire 14 caused by its movement with respect to the record medium 106, said distance being designated as "b" in Fig. 8E, the side load due to the relative motion of the print head 10 and the record medium 106 ceases, as shown in Figs. 8D and 8E, and further wear ceases, since the translation distance of the print wire 14 will not increase beyond a predetermined maximum.

WHAT WE CLAIM IS: - 1. A printing apparatus including a plurality of elongated printing elements arranged to be driven lengthwise to effect printing, and a frame in which are mounted an end bearing means having a plurality of printing element receiving apertures disposed therein, and a plurality of support members spaced apart along the lengths of said printing elements and disposed on that side of said bearing means remote from the printing ends of said printing elements, each support member having a plurality of printing element receiving apertures disposed therein in such a manner that said printing elements each extend through corresponding apertures of said support members and said bearing means, wherein the pattern of apertures in said support members is so arranged as to accomplish translation of said printing elements from a generally circular pattern at the support member furthest from said bearing means into an essentially linear pattern at the support member nearest to said bearing means, the pattern of aper tures in the support member nearest to said bearing means being identical to, and having the same orientation as, the pattern of apertures in said bearing means.
2. An apparatus according to Claim 1, wherein the support member nearest to said bearing means is loosely mounted in said frame to provide a degree of freedom of movement in a plane transverse to the direction of movement of said printing elements.
3. An apparatus according to either Claim 1 or 2, wherein said frame is elong ated and its longitudinal axis is parallel to the direction of movement of said printing elements between said bearing means and the support member nearest to said bearing means.
4. An apparatus according to Claim 3, wherein the centres of said support members lie substantially on said axis of said frame.
5. An apparatus according to any one of the preceding Claims, wherein said printing elements are print wires.
6. An apparatus according to Claim 5, forming a printing head of a wire matrix printer.
7. A printing apparatus substantially as hereinbefore described with reference to Figs. 1 to 7 of the accompanying drawings.