Printing actuator
This is a continuation of application Ser. No. 479,416 filed June 14, 1974 now abandoned, which is a continuation of Ser. No. 308,876 filed Nov. 22, 1972 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is concerned with a striking device for a printing machine of a completely new type whose printing speed may be substantially increased. 
     SUMMARY OF THE INVENTION 
     According to the invention, the striking device for a printer comprises a number of hammers and a shaft rotating continuously and capable of actuating each of these hammers causing it to perform a strike. It is distinct, on the one hand, by each of the hammers being mounted so as to pivot around an axle and by being integrated with electro-magnetic means including two poles opposite each other, and on the other hand, by said shaft bearing a number of transverse parallel discs of a material that is a good conductor of electricity. The two poles are associated with a hammer and are positioned on either side of said discs. Thus, when said electro-magnetic means associated with a hammer are actuated, a magnetic field is generated between the corresponding poles. This magnetic field entails the appearance of eddy currents in the disc positioned between said poles. The currents cause said hammer to pivot in such a manner that the poles rotate instantly along with the disc. Thus a print is performed by this hammer. 
     The electro-magnetic means comprise preferably a coil, concentric with the pivoting axis of the hammer, and two magnetic arms, opposite said hammer relative to said axis. The arms bear said poles at their ends. This coil may be integral with the hammer and the arms, but it is recommended that the coil be solidly attached so that the inertia of this rotating assembly be reduced, and that it may pivot relative to the coil. 
     The return media of the hammers may consist of media similar to the above described actuating devices or of electro-magnets. It is, at any rate, preferable for reasons of simplification that these return media consist of springs. 
     When this printing device includes a number of aligned hammers it may be useful, so as to give them appropriate dimensions, to divide them into two groups in such a way that two adjoining hammers belong to different groups and to provide two parallel pivoting axes, associated with one of said groups, each disc of the shaft being associated with one hammer of one of the groups, and with a hammer of the other group. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The figures of the attached drawing will clarify the embodiment of the invention, in which; 
     FIG. 1 is a perspective view designed to explain the operation of the printing hammer according to the invention; 
     FIG. 2 is an elevational view, partially in section, of a striking device for a printer according to the invention; 
     FIG. 3 is an enlarged section taken along the line III--III of FIG. 2; and 
     FIG. 4 is an enlarged section taken along the line IV--IV of FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The printing module shown in FIG. 1 comprises a shaft 1, constantly rotating in the direction of the arrow F, on which is mounted a disc 2 of a material which is a good conductor of electricity, such as copper or aluminum. The periphery of the disc 2 is engaged between the poles 3 of an electromagnetic circuit comprising a U-formed frame, consisting of two parallel arms 4 and 5, solidly attached to each other, at their ends opposite poles 3 by a socket 6 which is concentric with a non-magnetic shaft 7 round which the assembly 3, 4, 5, and 6 may rotate. The electro-magnetic coil 8 is positioned between the arms 4 and 5 and concentrically with the socket 6 and is attached from the outside in a manner not shown to the frame 9 of the machine of which the print module is a part, but in such a fashion that it does not share in the rotation of the assembly 3, 4, 5, and 6. A print hammer 10 is solidly attached to the free end of an arm 11 which is an extension of the arm 4 beyond the axis of non-magnetic shaft 7. 
     When the coil 8 is excited by a pulse a magnetic field occurs between the poles 3 and 3&#39; of the arms 4 and 5 and crosses the rotating disc 2. Its result is the formation of eddy currents in this disc which currents effect the driving of the arms 4 and 5 in the direction F of the rotation of the disc 2, and, consequently, the driving of the hammer 10 in the direction f of the strike. 
     The return of the hammer 10 to the rest position as illustrated in FIG. 1, at the end of the excitation pulse of the coil 8, may be accomplished by a device similar to the actuating device which was just described, but driving the hammer 10 in the reverse direction. Such a device offers the advantage of preventing rebounds of the hammer and of reducing the total time for a cycle of the hammer. Yet for purposes of simplification it is preferable to use a return spring (not shown in FIG. 1). 
     It goes without saying that the shaft 1 is capable of carrying a number of discs 2 whereas a number of hammers 10 may pivot round the shaft 7, whose arms 4 and 5 interact with one of the discs 2. In this manner a striking device is obtained which may be applied to a printer of the parallel or parallel-series type. 
     FIGS. 2 to 4 show a striking device for a parallel printer fo the &#34;back striking&#34; type in which the characters are carried by a character-bearing drum 12, which is continuously in rotation. Opposite a surface of the drum 12 a number of aligned striking hammers 13 is arranged. A paper tape 14 and a carbon ribbon 15 pass between said striking hammers 13 and the drum 12. 
     This striking hammer 13 is integral with the end of an arm 16 which is mounted so as to rotate on a fixed shaft 17 by means of a ring 18 of non-magnetic and wear resistant material, for instance of self-lubricating calcinated bronze, Nylon or Delrin. 
     Each arm 16 extends beyond the axis 17 by an arm 19. An arm 20, identical with arm 19, is connected with the latter so as to be capable of rotating with the ring 18, its free end 21 being positioned opposite the free end 22 of the arm 19. These two arms are made of a magnetic material. They are joined on the side of shaft 17 by a magnetic core 23 which surrounds the ring 18. An electro-magnetic coil 24 is mounted on the magnetic core 23 between the arms 19 and 20. Thus, these arms constitute together with coil 24 and the core 23 an electro-magnetic circuit whose poles are the ends 21 and 22. 
     Laterally of these poles the two associated arms 19 and 20 are kept spaced from one another by a non-magnetic brace 25. Such a brace prevents the displacement of the two poles 21 and 22 toward each other by mutual attraction during the excitation of the coil 24. 
     In the air-gap of each pair of poles 21 and 22 the periphery of a copper disc 26 is located. All the discs 26 are parallel to each other and solidly attached to a drum 27 which is continuously driven at high speed. The discs 26 are transverse to the axis of the drum 27. 
     There are half as many discs 26 as hammers 13, while the latter are mounted rotating round two parallel shafts 17 in such a way that two adjoining hammers rotate, one around one of said shafts 17 and the other round the other shaft. Thus a single disc 26 may drive two hammers 13. Such an arrangement has advantages for it permits one to provide satisfactory dimensioning of the strike modules. The result is that the arms 16 of the two hammers 13 adjacent to each other are curved towards one another in such a manner that the distance separating these two adjoining hammers corresponds with a pitch of the characters on the drum 12. 
     The two shafts 17 are supported by the arms 28, integral with beams 29, positioned longitudinally relative to the drum 27. The arms 28 are of a non-magnetic material and function simultaneously as separators between the striking modules. 
     There is also a resistant support needed for the striking modules 17 because of the considerable forces acting on these shafts at the moment of impact and for support of the weight of the modules which may produce a deformation by bending of said shafts. 
     The excitation of a coil 24 generates a magnetic field in the air-gap of the corresponding poles 21 and 22. This magnetic field crosses the disc 26 positioned in this air-gap and generates eddy currents there which causes the arm 16 to pivot for the strike of the hammer which it carries. 
     Each hammer 13 is maintained in its rest position by a spring 30, operating as return device for said hammer after a strike. The springs 30 are mounted between the corresponding arms 16 and a leg of the angle iron 31, mounted on a longitudinal beam 32. The angle iron 31 is equipped with slots 33 placed opposite of the character columns on the drum 12 and function as guides for the ends of the arms 16 during the striking of the hammers 13. 
     The springs 30 may be replaced by electro-magnets each of which would be linked with a striking hammer and would be continuously excited up to the moment at which the corresponding coil would receive a strike pulse. 
     The electro-magnet would then again be excited. Thus, compared to the springs 30, the electro-magnets would offer the advantage that no retention force would be applied to the hammers during the strike, hence the striking speed would be greater. 
     As already mentioned above, the return of the hammers could also be effected by a device operating by the generation of Foucault currents and of a type similar to the one described in the actuating of said hammers.