JPH0114032B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Background of the Invention (1) Field of the Invention The present invention relates to a dot matrix impact type line printing device, and more specifically, it is used in the above-mentioned printing device. A flexible hammer spring held in a retracted position by the structure is selectively fired for impact printing via a dot printing impact tip mounted on the free end of the hammer spring. This is related to the printing hammer mechanism.

(2) Prior art A dot matrix row printing device is provided with a reciprocating shuttle including a hammer row, and when the shuttle reciprocates against the printing paper supported by the platen, a dot impact is generated on the free end of the shuttle. It is already known that a plurality of elongated resilient, generally parallel hammer elements with tips are selectively ejected from a retracted position to impinge on an ink ribbon resting against a printing paper. There is. Such a device was published in March 1975 and is covered by the Barras et al. U.S. patent no.
No. 3941051. In the Barras et al. patent, the hammer array uses a printed hammer mechanism that forms a generally C-shaped magnetic circuit between opposing fixed and free ends of each hammer element. This magnetic circuit includes a common permanent magnet to which each hammer element is coupled to its fixed end, a common magnetic return path coupled to the permanent magnet opposite each hammer element, and a common magnetic return path coupled to the permanent magnet opposite each hammer element. There are a plurality of pole pieces extending outwardly from the magnetic return path terminating in the pole tip facing the free end of the magnetic return path. Normally, the magnetic flux of the permanent magnet pulls the hammer element out of the neutral position, presses it against the pole piece, and draws it into the retracted position under the force of the spring. Each time the coil surrounding the pole piece is momentarily energized, the attractive force of the permanent magnet is sufficient to strike the hammer element out of its retracted position and propel it toward the ink ribbon and print paper. Only to be beaten for a long time. After striking the dot printing tip against the ribbon and paper, the hammer element springs back into its spring-loaded retracted position in preparation for the next energization of its coil.

The print hammer mechanism shown in the Barras et al. patent uses a single pole piece with an individual hammer spring. The performance of such a mechanism, for example,
It has been found that improvements can be made by adding a second pole piece as shown by Ballas et al., U.S. Pat. Ivy. US Patent No.
In the printing hammer mechanism of No. 4233894, the hammer spring is
At the same time as it contacts the main pole piece, it forms an air gap with the auxiliary pole piece disposed between the main pole piece and the fixed end of the hammer spring. The air gap created by the auxiliary pole piece and the additional flux path provided by the auxiliary pole piece combine to improve both the launch and retraction characteristics of the print hammer mechanism. Another device that achieves a similar effect using different pole pieces, each with a hammer spring, was published on March 31, 1982 and is covered by commonly assigned U.S. Pat.
No. 4258623.

The print hammer mechanism shown in the various patents of Barras et al. has been found to work reliably and effectively for printing applications using speeds of 600 lines per minute or more. In this regard, it has been observed that the wear and tear that occurs on the print hammer mechanism increases significantly as printing speeds increase. Therefore, wear and tear, which may not be an issue at print speeds up to 300 lines per minute, can become a significant factor affecting the actual life of the print hammer mechanism when 600 lines per minute are constantly required. There is sex. Experience has shown that at high printing speeds, a considerable amount of wear occurs on the hammer due to the frequent striking of the main pole piece with the free end of the hammer spring each time it springs back into its retracted position after printing a dot. It has been found that this can occur in both the spring and the main pole piece. Eventually, a crater-like depression begins to form at the free end of the hammer spring, and the depression can be as deep as 0.043 mm in places. In the end, the hammer spring may actually break,
Alternatively, the air gap between the pole piece tip and the hammer spring may be increased by the crater, making it difficult to retract into the retracted position after each impact print. Pole shoe tips are themselves susceptible to wear. Attempts to minimize wear by covering the pole piece tips with plastic materials or other elastomers have had very limited success, as it is clear that such materials wear away rapidly. The resulting tendency to require frequent replacement and thereby increase problems is due to its inherent effect.

In addition to the wear problem that is exacerbated by increasing print speeds in print hammer mechanisms of the type shown in the Barras et al. patent, there are other operating characteristics of such mechanisms that are in constant need of improvement.
For example, the current required to energize a coil attached to a main pole piece to drive a hammer spring is an important factor in the overall current requirements of a printing device. Anything that provides satisfactory operating characteristics of the marking hammer mechanism while at the same time reducing the current required to drive the hammer spring is a welcome improvement. Such a reduction in current requirements is often accompanied by an improvement in the actual launch characteristics of the hammer spring. It has also been observed that in the case of high-speed printing, the parts of the hammer spring other than the part that strikes the pole pieces undergo some kind of metal corrosion due to wear of the mechanism and overall vibration. This has been observed to occur, for example, at the interface between the hammer spring member and the bonding material to which the spring is attached to the fixed end. Such metal corrosion is also a cause of shortening the lifespan of springs.

Accordingly, it would be desirable to provide an improved print hammer mechanism.

Additionally, it would be desirable to provide a print hammer mechanism that operates to reduce or minimize wear and tear from constantly striking the hammer spring with the pole pieces of the magnetic structure.

Additionally, it would be desirable to provide a print hammer mechanism that has the potential for further improvements or advantages with respect to other types of wear and tear and in the actual operating characteristics of the print hammer mechanism.

(2) SUMMARY OF THE INVENTION The above objects and others are achieved in accordance with the present invention by a print hammer mechanism using an intermediate pivot fulcrum. This intermediate pivot fulcrum is
provided by an impingement structure having a surface disposed in opposing relation to the hammer spring at an intermediate portion between the fixed end and the free end of the hammer spring. In this printing hammer mechanism, when the hammer spring is pulled into the retracted position, the middle part of the hammer spring hits,
It is then configured to rest against the collision structure. At the same time, the hammer spring forms an air gap with the main pole piece to provide the benefits possible with contacting pole pieces and individual air gap forming pole pieces.

Preferably, the impingement structure is covered with a member of plastic, such as Kapton, or a similar elastomeric material to provide a non-metallic pivot point for the elastomer. This feature, in combination with the location of the impact zone in the intermediate region of the hammer spring, greatly reduces the interfacial wear between the hammer spring and the impact structure, while at the same time making fatigue failure of the hammer spring very small. Vibration and other energy is easily absorbed and the curvature of the hammer spring is such that metal corrosion of the hammer spring itself is minimized at the fixed end to which it is attached. At the same time, it has been found that hammer springs are easier to launch using less launch current than is required by many of the devices described above.

In a preferred embodiment according to the invention, the impingement structure is attached to the fixed end of the hammer spring and extends in spaced relationship generally parallel to the spring between the fixed end and the intermediate portion of the spring. It is formed by an auxiliary pole piece that is shaped like an auxiliary pole. The auxiliary pole piece terminates in a pole tip forming an impact surface that receives and retains the intermediate portion of the hammer spring. This impact surface is covered with a thin layer of Kapton. A piece of Kapton is attached to the bottom of the auxiliary pole piece so that it extends along the pole piece and then over the pole tip forming its impingement surface. Although the interfacial wear is considerably less than in the printed hammer mechanism described above, such wear may occur if the auxiliary pole piece tip or other impingement structure is placed in the plane of the hammer spring at or near the node of secondary vibration of the hammer spring. It can be further reduced by placing

(3) Detailed Description The foregoing and other objective features and advantages of the present invention will become apparent from the following more detailed description of preferred embodiments of the invention, illustrated in the accompanying drawings.

FIG. 1 shows a shuttle 10 with a hammer array 12 using a printing hammer mechanism 14 according to the present invention. Each of the print hammer mechanisms 14 has a different one of the plurality of hammers 16. Shuttle 10 has a hollow, generally rectangular cover 18 forming a frame thereof. As seen in FIG. 1, a bracket 20 extends out of the shuttle 10 through the cover 10 at one end of the shuttle 10 and receives a support shaft 22. Although omitted from FIG. 1 for simplicity of illustration, the opposite end of the shuttle 10 is also provided with a bracket and support shaft that operate in the same manner as the bracket 20 and support shaft 22.
can slide and reciprocate. At the same time, both brackets allow the shuttle 10 to pivot outwardly away from the length of the paper 26 disposed on the opposite side of the ink ribbon 30 from the hammer row 12.

The manner in which the shuttle 10 is mounted and driven in a reciprocating manner is described in the above-mentioned U.S. patent by Ballas et al.
This is the same device as described in No. 3940051. The Barras et al. patent utilizes a double-lobed cam drive mechanism to reciprocate the shuttle across the length of the paper, allowing multiple hammers mounted parallel and side-by-side within the shuttle to be individually independent. It describes in considerable detail how to perform dot matrix printing by operating the following methods. Each hammer is provided with a dot matrix printed chip approximately at its center of impact, which normally energizes a coil to drive the hammer out of its retracted position where it is held by a permanent magnet. Then, the ink ribbon is struck against the paper supported by the platen. Each time the shuttle sweeps horizontally along the paper to print a line of dots, the paper is shifted vertically one line, and then the shuttle makes a horizontal sweep in the opposite direction to print the next line of dots on the paper. Print the dots on the line.

As seen in FIG. 2 as well as FIG. 1, each of the hammers 16 has a generally horizontal spring at its lower fixed end 36 extending across the front of the hammer row 12 in spaced relationship with another spring 34. mounted along the axis,
It includes a relatively thin, generally flat spring 34 of resilient magnetic material disposed generally vertically and terminating in an upper movable free end. Each spring 34 includes a dot matrix printed impact tip 40 extending perpendicularly from its surface in a direction toward the ribbon 30. The tips 40 of successive hammers 16 are located along the selected horizontal line. When you pull it in,
Each chip 40 is disposed slightly behind a different hole in the front face 42 of the cover 18.

As seen in FIGS. 1 and 2, the printing hammer mechanism in the hammer row 12 includes a magnetic material mounted on the side of the hammer 16 opposite the printing tip 40 in a spaced relationship parallel to the hammer. There is a flat common return member 44 consisting of. Each print hammer mechanism 14 has a magnetic pole tip 48 and an associated hammer 16 extending outwardly from the common return member 44.
There is a generally cylindrical first pole piece 46 that is closely aligned. When each hammer 16 is in the retracted position, it forms an air gap with an adjacent pole piece 46 and is in the same magnetic path as that. An electromagnetic energizing coil 50 is individually wound around each pole piece 46 adjacent to the pole tip 48, and the leads of the coil 50 connect to terminals on the common return member 44 and printed circuit conductors (details not shown). It is convenient to connect to. The external conductors to the associated circuitry are physically coupled together in the form of a harness 52 extending outwardly from the shuttle 10 to the associated drive circuitry. Harness 5
2 reciprocates along its length along with the movement of the shuttle 10.

The print hammer mechanism 14 also includes a common return member 4.
4 and an auxiliary pole piece 56 is a common permanent magnet 54 in the form of an elongated square bar. Auxiliary pole piece 56 serves as a common mount for each hammer spring 34. The auxiliary pole piece 56 is of thin, flat configuration and extends along a portion of the length of each hammer spring 34 with an outwardly projecting first end 5.
8 and an opposite second end terminating in a pole tip 60, generally parallel to and spaced apart from the hammer spring 34. The auxiliary pole piece 56 is arranged such that a wide surface on one side thereof is in contact with the common permanent magnet 54 . A first end 58 extends outwardly from the side of the auxiliary pole piece 56 opposite the broad surface 62 and extends from the lower fixed end 36 of the hammer spring 34.
are adapted to be received and mounted in generally parallel and spaced relationship along said side surface. The opposite end of the pole piece 56 is bent outwardly opposite the broad surface 62 to form a pole tip 60.

FIG. 3 shows one hammer spring 34 of the print hammer mechanism 12 in a neutral or undeflected position. In this position, the air gap is between the first pole piece 4
6 magnetic pole tip 48 and the upper free end 38 of the spring 34
is formed between. The gap is the hammer spring 34
and a thin layer 66 of elastomeric material, such as Kapton, extending upwardly from the first end 58 of the auxiliary pole piece 56 and covering the pole tip 60. Lamina 66 is a single piece of material extending along the length of hammer row 12 and is adapted to cover pole tip 60 at an intermediate portion 64 along the length of hammer row 12 of each hammer spring 34. thin layer 6
The lower end of 6 is secured to the auxiliary pole piece 56 by adhesive or other suitable means. In this example, the thickness of the thin layer of Kapton is approximately 0.13 mm (5 mils).

When no current is flowing through coil 50, the magnetic attraction created by permanent magnet 54 on pole tips 48 and 60 has the effect of drawing hammer spring 34 into the retracted position shown in FIG. Hammer spring 34
in the retracted position, the middle part 6 of the spring 34
4 rests against the portion of the thin layer 66 that covers the pole tip 60. At the same time, the dimensions are about 0.025 ~
A small air gap 68 of 0.05 mm (1-2 mils) is formed between the upper free end of the hammer spring 34 and the pole tip 48 of the tenth pole piece 46.

Hammer spring 3 from the retracted position shown in Figure 4.
4 is achieved by energizing coil 50 long enough to overcome the action of permanent magnet 54. As a result, the hammer spring 3
4 passes through the neutral, upright position shown in FIG. 3 to the position of FIG. ink ribbon 3
Turn to the position where it hits 0. The hammer spring 34 and its attached tip 40 bounce off the ink ribbon 30 and paper 26 to fly through the neutral position shown in FIG. 3 to the retracted position shown in FIG. When the hammer spring 34 reaches its retracted position, the intermediate portion 64 of the spring strikes the portion of the lamina 66 covering the pole tip 60 and then rests against it. At the same time, an air gap 68 remains between the upper free end 38 of the hammer spring 34 and the pole tip of the first pole piece 46. When the coil 50 is momentarily energized again, the process is repeated and the hammer spring 3
4 flies forward through the neutral position of FIG. 3 to the striking position of FIG. 5, and then the hammer spring 34 rebounds back to the retracted position of FIG.

Each time hammer spring 34 returns to the retracted position of FIG. 4, intermediate portion 64 of the spring strikes pole tip 60 through intervening thin layer 66. The auxiliary pole piece 56 and the thin layer 66 therefore form an impingement structure in addition to an auxiliary pole piece. According to the invention, the intermediate portion of the hammer spring 34, the thin layer 66 and the pole tip 60
It has been found that the interfacial abrasion between the two is negligible compared to the abrasion problems encountered with conventional print hammer mechanisms. The reason for this is, at least in part, that the pole tip 60 and the adjacent portion of the lamina 66 are lower on the hammer spring 34 than the pole tip 48 of the first pole piece 46, which is used as a collision surface in some conventional constructions. The idea is to form an intermediate pivot fulcrum that is closer to the fixed end. Another reason why interfacial wear is minimized relates to the nature of the hammer spring 34 itself and the way it flexes and oscillates.
When deflected from the neutral position shown in FIG. 3, the hammer spring 34 experiences vibration in the first mode of its natural frequency in its plane. At the same time, the hammer spring 34 experiences other higher modes of vibration within its plane. The next higher order such mode of vibration, occurring at a frequency significantly greater than the natural frequency of the spring, causes whiplash along the length of the hammer spring 34 as it deflects near its lower fixed end 36. Or it has the effect of causing wave motion. This whipping or wave motion causes the spring 34 to undergo a sliding motion generally perpendicular to the surface against which the spring 34 strikes so as to increase wear at the interface between the hammer spring and the impact surface. The nature of the next higher mode of the hammer spring 34 is such that this vertical sliding movement
It is such that when the point of impact is chosen to be the pole tip 48 of the first pole piece 46, an increasingly greater effect occurs. In this regard, the effect on the interface wear of the next higher mode of vibration at the point of impact is the effect of the next higher mode of vibration at the intermediate fulcrum formed by the pole piece 60 and the adjacent point portion of the thin layer 66. At a node, it is effectively eliminated.

In the printing hammer mechanism 14 shown in FIGS. 3-5, the magnetic pole tip 60 of the auxiliary magnetic pole piece 56 and the thin layer 6
The intermediate pivot fulcrum formed by the adjacent portion of the hammer spring 34 is located near the node of vibration of the next higher mode in the plane of the hammer spring 34. This is accomplished, at least in part, by covering the pole tip 48 of the first pole piece 46 with a thin layer of Kapton or similar elastomeric material to provide a point of impact for the pole tip 48, as is the case with some conventional marking hammer mechanisms. This is why the amount of interfacial wear that occurs between the intermediate portion of the hammer spring 34 and the thin layer 66 is much smaller than when using the hammer spring 48. Previously cited U.S. Pat. No. 4,233,894 and
In the printing hammer mechanism shown in '4258623, the hammer spring impinges on and rests against the pole tip of the first or main pole piece to form an air gap with the auxiliary pole piece. It has been found that the launch and retraction characteristics of the hammer spring are enhanced by using two pole pieces such that an air gap remains in one of the two pole pieces when the hammer spring is in the retracted position. . These advantages are such that when the hammer spring 34 is in the retracted position shown in FIG.
This is also achieved by the print hammer mechanism of the present invention, which is present between the first pole piece 46 and the first pole piece 46 . Other advantages in the hammer spring launch and retraction characteristics are also realized by creating a pivot fulcrum in the middle of the hammer spring 34 provided by the pole tip 60. When the hammer spring 34 is in the retracted position of FIG. 4, the upper free end 38 of the hammer spring 34
The magnetic attraction applied by the first pole piece 46 through the air gap 68 acts to create a point load on the deflected beam formed by the hammer spring 34. This point load is different from the nature of the load placed on the hammer spring 34 when the first pole piece 46 is used as a contact point, and is easily and conveniently applied to the coil 50 when the hammer spring 34 is held from the retracted position of FIG.
It has the effect of applying a smaller current to launch the ball. A small reduction in the amount of firing current required for the various print hammer mechanisms 14 can result in a significant reduction in the total current consumed by the hammer train 12.

In addition to minimizing interfacial wear between the hammer spring 34 and the impact surface, the printing hammer mechanism 14 according to the present invention has been found to greatly reduce fatigue failure of the hammer spring 34 to the point of almost completely eliminating it. Because the pivot point provided by the pole tip 60 is located adjacent to the intermediate portion 64 of the hammer spring 34, the impact itself is much less severe than the configuration in which the upper free end 38 of the hammer spring 36 strikes a surface. reduced. Only this factor is the hammer spring 3
4, which significantly reduces the possibility of fatigue failure. However, other factors that reduce hammer fatigue failure are related to greatly reduced interfacial wear. In the conventional printing hammer mechanism, where a crater-like depression occurs on the joint surface of the hammer spring due to constant interfacial wear, such a crater-like depression is particularly important when it is considered that the impact exerted on the hammer spring is large. This increases the possibility that the hammer spring will suffer a fatigue failure.

Other advantages of the print hammer mechanism according to the present invention occur in the form of reduced wear and corrosion of the hammer spring 34 and interfacing elements within the print hammer mechanism. In many conventional marking hammer mechanisms, metal corrosion occurs at the interface between the lower fixed end 36 of the hammer spring 34 and an adjacent element, such as the outwardly extending first end 58 of the auxiliary pole piece 56. I know that. This corrosion appears to be due to the way the hammer spring flexes and the amount of impact involved. These factors contribute to the abrasive movements that can result in the actual metal corrosion described above. In the printing hammer mechanism 14 according to the present invention, such metal corrosion is reduced to a very small extent due to the smaller impact and the different deflection of the hammer spring.

In this example, element 66 is described as a single layer of resilient abrasion resistant material such as Kapton. In fact, similar results can be achieved using other shapes made of Kapton or similar materials. For example, the single ply 66 could be replaced by plywood with several layers of Kapton or similar material. In one particular embodiment according to the invention, the outwardly extending first end 58 of the auxiliary pole piece 56
from the top of the magnetic pole tip 60 to the magnetic pole tip 48.
a 0.0254 mm (1 mil) thick layer of Kapton extending from the outwardly extending first end 58 of the auxiliary pole piece 56 past the pole tip 60 but not to the pole tip 48; It is replaced by plywood consisting of two 0.051 mm (2 mil) thick plywood sheets of Kapton extending to and terminating. In addition,
One layer of Kapton with a thickness of 0.0254mm is the magnetic pole chip 4
8 and may occur under certain conditions, such as when the distance between the print hammer mechanism 14 and the platen 70 is relatively large. absorb the blow.

[Brief explanation of drawings]

FIG. 1 is a partially cut away perspective view of a portion of a shuttle equipped with a hammer row using a printing hammer mechanism according to the present invention; FIG. 2 is a front elevational view of a portion of the hammer row of FIG. 1; 3 is a cross-sectional view of the hammer row of FIG. 1 taken along line 3--3 of FIG. 2 showing the hammer spring in a neutral, undeflected position; FIG. 5 is a cross-sectional view similar to that of FIG. 3, but showing the hammer spring in the retracted position; FIG. 5 is a cross-sectional view similar to that of FIG. It is a figure which shows a certain hammer spring. 12... Hammer row, 14... Printing hammer mechanism,
16...hammer, 26...printing paper, 30...ink ribbon, 34...hammer spring, 36...fixed end of hammer spring, 38...free end of hammer spring,
40...Printing chip, 44...Common return path member, 4
6...Main pole piece, 48...Magnetic pole tip, 50...
Coil, 54...Common permanent magnet, 56...Auxiliary magnetic pole piece, 60...Magnetic pole chip, 66...Thin layer.

Claims (1)

[Scope of Claims] 1. An elastic hammer element having both ends as a fixed end and a free end, and a printing element is attached adjacent to the free end, and the hammer element is attached at the fixed end of the hammer element. a magnetic structure; a pole piece attached to the magnetic structure and terminating in a pole tip disposed opposite the free end of the hammer element; and the fixed end and the free end of the hammer element. a hammer element collision mechanism disposed facing the hammer element at an intermediate portion of the hammer element between the magnetic pole tip and the hammer element when the hammer element is in a neutral undeflected position; means for selectively creating a magnetic field spaced apart from both the impingement mechanism and coupled to the magnetic structure to attract the hammer element towards the pole tip and the impingement mechanism; The tip and the impact mechanism form an air gap with the pole tip when the hammer element strikes the impact mechanism and is thereby deflected to a retracted position by the magnetic field. The printing hammer mechanism is arranged to do this. 2 from a single elongated relatively flat strip of magnetic material, wherein the resilient hammer element has a relatively small uniform thickness and assumes a relatively straight shape when in a neutral, undeflected position; and the means for creating a magnetic field includes permanent magnet means, and when the hammer element impingement mechanism deflects the hammer element to the retracted position, the other of the wide faces of the elongated strip is Claims comprising a second pole piece received in an area intermediate the fixed end and the free end, said permanent magnet means creating a magnetic field which normally maintains said hammer element in a retracted position. The printing hammer mechanism according to item 1.