JPH0442992B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printing hammer used in an impact printer.

Since the printing hammer prints while sliding relative to the ink ribbon and paper, the printing surface of the printing hammer is hardened in consideration of wear resistance.

FIG. 1 shows an example of a printing mechanism, and FIG. 2 shows an enlarged printing surface 9 of the printing hammer 1. As shown in FIG. A hardened layer 10 is provided on the printing surface 9.

FIG. 3 shows a printing hammer 20 for a dot printer, in which a hardened layer 23 is provided at the tip of a wire 22.

The type printing hammer 1 shown in FIG. 1 is made of steel, and the hardened layer 10 is carbonitrided, gas nitrided, or WC spray coated. Also, the hardened layer 23 of the dot printing hammer 20 shown in FIG.
The wire is made of cemented carbide or sintered alloy, which has relatively high wear resistance, bonded to steel wire, and the tip of the wire is surface-treated by nitriding, coating with TiN, etc.

As the printing speed increases, there is a problem in that the above-mentioned materials and hardened layers are subject to significant wear.

For this reason, a printing hammer having a platinum group alloy bonded to its tip has been proposed. This alloy is manufactured by sintering or melting, but it is prone to defects such as segregation and cavities, and has poor toughness. At high printing speeds, the tip of the printing hammer may chip or break during operation, so the printing hammer cannot be used. have been forced to replace.

In grinding, since the alloy is hard and brittle, chipping occurs during grinding, resulting in poor production yield. Furthermore, the printing surface is ground into a certain shape, but the grinding process requires a large amount of material, leaving less than half of what remains on the printing hammer.This type of metal is expensive, so the cost is high. Printing hammers that can use this alloy are limited to those that have a minute printing surface, such as the dot printing hammer 20, and this printing surface
The processability, grindability, and
It is unsuitable from the point of view of cost.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to provide a printing hammer that can be applied regardless of the size of the printing surface and has a long life at a low cost.

The present invention is characterized by paying attention to the fact that platinum group alloys are expensive, and by forming a coating with these alloys, a long-life printing hammer can be obtained at low cost.

Ion plating, sputtering, chemical vapor deposition, plasma spraying, etc. can be used to coat the printed surface with a specific alloy, and a method of forming a coat using ion plating will be described.

FIG. 4 is a diagram showing an ion plating apparatus. It consists of a substrate 14 in which a printing hammer is attached inside a container 13, a holder 15 that holds a vapor deposit 16 made of the alloy, and an electron beam source 17, and the atmosphere inside the container 13 is controlled by an inert gas of 10 ^-3 to ^{10 -6} Torr or less. A negative voltage of several hundred to several thousand volts is applied to the substrate 14. When the deposit 16 is evaporated in this state, the deposit 16 is ionized in the plasma, and the ionized deposit 16 collides with the printing surface of a printing hammer (not shown) held on the substrate 14 to form a coating. If ion bombardment with an inert gas is applied before vapor deposition, the printing surface will have a spatter cleaning effect and the adhesion of the film will be improved. The thickness of the film formed in this way depends on the processing time, but it is 0.5~
100μm is common.

Since the printed surface is coated with a thin film of the alloy, the shape of the printed surface is particularly important, and it is essential that the outer periphery of the printed surface be curved. This is to prevent the coating from peeling off, and if the outer periphery of the printing surface has an acute angle, peeling will occur from the acute angle during printing. Also, because the printing speed has increased, the printing impact force has increased,
The hardness of the base material for the coating is also required, with a Vickers hardness of 500 or higher, which is also an essential condition. If the Vickers hardness of the base material is less than 500, the base material will be soft and therefore, no matter how highly wear-resistant a coating is formed, the printed surface will collapse or cave in, making it unusable.

Since the coating is formed in the form of a thin film, the entire coating is continuous and always uniform. As described above, since the coating is formed in accordance with the shape of the printed surface, it is not limited by machining and has the advantage that post-processing is not necessary.

The features of the present invention are that it is possible to form a coating of a specific alloy that follows the shape of the printed surface, has good wear resistance, eliminates the hassle of processing accuracy, and can be processed regardless of the size of the printed surface. Therefore, it is possible to improve productivity and reduce costs.

The specific alloy is either an alloy of platinum group metals or an alloy of platinum group metals and transition metals. Platinum group metals include ruthenium, rhodium, palladium,
These include osmium, iridium, and platinum. Two or more of these metals are combined to form an alloy and formed as a coating on the printing surface. In particular, 40% by weight (hereinafter abbreviated as %) osmium (Os) - 30% iridium (Ir) - 30% ruthenium (Ru) is preferable in terms of manufacturing and has good wear resistance.

Coatings made of these alloys have good wear resistance, but since the metal itself is expensive, it is also possible to partially replace the alloy with a transition metal in order to reduce costs. Transition metals that are easy to form a film include titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum,
Tungsten (W), rhenium, cobalt (Co),
Nickel, manganese, iron, etc. One or more of the above transition metals are selected to replace a part of the platinum group alloy. In particular, transition metals are 40% by weight.
The following is preferable; if it exceeds this range, the influence of transition metals will occur, resulting in poorer wear resistance and corrosion resistance than platinum group alloys.

The coating thickness in the present invention can be varied in various ways, but from the relationship with the Vickers hardness of the base material, it is preferably 5 μm or more in consideration of wear resistance and peeling resistance. Further, the coating may be one layer or two layers. Furthermore, in order to improve the adhesion of the coating, plating with Ni-P, Co-P, etc. may be applied, and a coating made of the specific alloy may be formed thereon.

<Example 1> The printing hammer 1 for type was formed of carbonitrided nickel chromium molybdenum steel (JIS standard SNCM420), and the treatment temperature was 800° C. and the treatment time was 1 hour. A printing hammer 1 having a printing surface having a Vickers hardness of 730 was set on the substrate 14 and held so that the printing surface 9 of the printing hammer 1 faced the deposit 16. Deposit 16 contains 40%Os-30%Ir-30%Ru
The alloy was set. After that, the inside of container 13 is
After setting the temperature to 10 ^-5 Torr, argon gas was introduced, a DC voltage of 2 KV was applied, and the printed surface was first cleaned of spatter for 10 minutes.

The temperature of the printing hammer was set to 200° C. below the tempering temperature, and the deposit 16 was irradiated with an electron beam for 2 hours to evaporate it. After processing, the printing hammer was taken out and the coating thickness was measured, and it was found that a 15 μm alloy coating was uniformly formed on the printing surface. The Vickers hardness of the coating is
It was 730.

<Example 2> The same process as in Example 1 was carried out except that the deposit 16 was 50% Os-30% Ir-30% W. The coating is
The Vickers hardness was 850 at 12 μm.

<Example 3> The same process as in Example 1 was carried out except that the deposit 16 was made of 60% Ru-25% W-15% Co. The coating is
The Vickers hardness was 780 at 20 μm.

<Comparative Example 1> The above carbonitrided nickel chromium molybdenum steel was used for the printing hammer 1 for type, and the treatment temperature was
The temperature was 800°C and the treatment time was 1 hour. Tempering temperature is 240
℃. At that time, the Bitkers hardness of the printed surface was 70.
It was hot.

<Comparative Example 2> Using quenched and tempered chromium molybdenum steel (JIS standard SCM435) of the printing hammer 1 for type, the printing surface was coated with a 25 μm WC sprayed layer. Its Bitkers hardness was 1280.

The above-mentioned five types of type printing hammers were continuously struck 2×10 ⁸ times to investigate the wear dimensions of the printed surfaces. The results are shown in FIG. As is clear from the figure, the product of the present invention had good wear resistance, and the wear size was about 1/4 that of the carbonitrided product and about 1/3 that of the WC sprayed layer.
With the coating of the present invention, no chipping or peeling was observed during printing, and clear printing was always ensured.

<Example 4> Carbon tool steel (JIS standard SK5) was used for the dot printing hammer 20, and the Vickers hardness of the printing surface was
There are four types: 300, 430, 550, and 780. This was set on the substrate 14 in the container 13, and the vapor deposited material 16
An alloy of 50% Os-40% Ir-10% Ru was set. Thereafter, the inside of the container 13 was set to 1×10 ^-5 Torr, argon gas was introduced, a DC voltage of 1.5 KV was applied, and the printed surface was first cleaned of spatter for 7 minutes. Set the printing hammer to 120℃ and apply 3 to the deposited material 16.
It was evaporated by irradiation with an electron beam for a period of time. After processing, the printing hammer was taken out and the coating thickness was measured. The coating surface thickness was 30 μm uniformly on the printing surface, and the Vickers hardness was 770.

The above four types of dot printing hammers 23 are used 3 times.
The abrasion dimensions of the printed surface were investigated by hitting the print surface ⁸ times in a row. The results are shown in FIG. If the coating base has a Bitkers hardness of 500 or more, the wear dimension will be
It can be seen that the thickness is less than 20 μm, indicating high abrasion resistance, and that more than 10 μm still remains on the printed surface. In addition, it was observed that the 30 μm alloy coating layer of the substrate with a Vickers hardness of 300 wore out early, and the printed surface was crushed. In addition, those with a Vickers hardness of 430 will wear out by the thickness of the coating, and if the number of hits increases beyond this point, it is expected that the same tendency will occur as with those with a Vickers hardness of 300. From the above, it is preferable that the base has a Vickers hardness of 500 or more.

As described above, the present invention dramatically extends the service life even at higher speeds by forming a highly abrasion-resistant alloy coating on the printing surface, and can be processed regardless of the size of the printing surface, and can be machined. It is possible to provide a printing hammer that is easy to manufacture and can improve production yield and reduce costs because it is not subject to the restrictions of the above.

[Brief explanation of drawings]

Figure 1 is a side view showing a printing mechanism using a type printing hammer, Figure 2 is an enlarged perspective view of the printing surface of the printing hammer shown in Figure 1, and Figure 3 is an example of a dot printing hammer. 4 is a side view showing an example of an ion plating device, FIG. 5 is a comparison diagram showing the results of a wear test between the printing hammer of the present invention and a conventional printing hammer using an actual machine, and FIG. 6 is a side view showing an example of the ion plating apparatus. FIG. 3 is a comparison diagram showing the Vickers hardness of the base of the coating and the wear size. In the figure, 1 and 20 are printing hammers, 2 is a rotating shaft, 3 is an armature, 4 is an actuator, 5 is an electromagnet, 6 is a type carrier, 7 is an ink ribbon, and 8
is the paper, 9 is the printing surface, 10 and 23 are the hardened layers, 21
is a leaf spring, and 22 is a wire.

Claims (1)

[Claims] 1. Consisting of a material with a Bitkers hardness of 500 or more,
A printing hammer characterized in that a printing surface having a curved outer peripheral portion is coated with one of a platinum group metal or an alloy of a platinum group metal and a transition metal. 2. The printing hammer according to claim 1, wherein the coating thickness of the alloy is 5 μm or more.