EP0021335A1 - Electromagnetic device for driving a print element - Google Patents

Abstract

1. A movable actuator mechanism with at least two operating gaps lying between magnet poles and in which armature elements are moved in an axial direction by the reciprocal influence of the magnetic field in the operating gap and the armature element, the entire mechanism consisting of at least one pair of facing, substantially symmetrically designed yoke halves (24, 27) forming the operating gaps between themselves and whose facing pole ends, each constituting one pole pair, form aligned operating gaps spaced from each other viewed in the operating direction of the armature elements (20, 21), wherein a ram (18) is provided which moves between the operating gaps in the direction of the line of alignment of the operating gaps and which is connected to the armature elements, characterized in that the respective yoke halves (24, 27), forming an electromagnet, consist of a magnetizable material and at least one of which is surrounded by an electrically excited coil (23, 26), that the ram (18) has a cross-section corresponding to the operating gap cross-section extending perpendicularly to its operating direction, that each pole pair of two facing yoke halves (24 and 27) is provided with one armature element (20 and 21) of magnetizable material and one spacer element (19) of predominantly non-magnetizable material arranged between said armature elements, so that each operating gap is associated with one armature element which is geometrically shaped such that its volume is of the order of the operating gap volume, and that each armature element (20, 21) in the original position of the ram (18) in the non excited state of the electromagnet, viewed in an axial direction, is positioned external to its associated operating gap, and that upon excitation of the pole pair of said operating gap, the armature element is pulled inside said operating gap.

Description

The invention relates to an arrangement of the type characterized in the preamble of claim 1.

In particular, the invention relates to a plunger drive for impact printers.

Such arrangements should achieve a very high efficiency with a serious weight minimization of the components with a space-saving construction - in particular for line printers with several drive units for the different printing positions lying next to one another.

Previously known, fast electromagnetic pressure hammer drives have a relatively poor efficiency for the following reason, among other things: A substantial part of the magnetic flux path runs through the armature both in the starting position and during the working phase. To conduct the magnetic flux in the armature, a ferromagnetic flux guide connected with a high mass is therefore necessary. The magnetic flux circuit to one side of the armature closes via this flux guide. The flow guide piece to be provided in the anchor, which has a high mass, is one of the causes of the poor efficiency of such pressure hammer drives, since the anchor and thus also the mass of this flow guide piece must be accelerated with each printing operation.

An arrangement in this regard is described in the German publication DAS 12 37 816, to which in connection 8 also describes the description in more detail,

Furthermore, an electromagnet with linear drive of the armature is known from German utility model 74 32 801.

With this arrangement, which in. 7, however, the following disadvantages occur: due to the special flat design of the anchor part (flat in this context means large in two dimensions compared to a third, which characterizes the thickness of the flat anchor), there are high, uncontrollable transverse forces in In addition to high friction losses, the armature also tilts in the direction of the pole shoes, which means that a clear movement in the desired direction of action cannot be achieved. In addition, with this arrangement, a substantial part of the magnetic flux is already caused by the partially guided between the pole pieces of the electromagnet armature, whereby the previously mentioned, low efficiencies (high armature mass) are required.

From the above-described prior art it can be seen that the known print hammer drives can have only low efficiencies due to the armature, which has a high mass, and that, when using the electromagnet with linear drive described above, lateral forces occur which preclude the use of this arrangement for print hammer drives.

To avoid the disadvantages mentioned above, it is an object of the invention to provide a fast electro-magnetically actuatable tappet drive, in particular for impact printers, which has a high degree of efficiency with minimal volume expenditure and low weight and is easy to manufacture.

This tappet drive is said to be particularly suitable for use in hammer banks for mechanical high-speed printers.

This object of the invention is achieved in an advantageous manner by the measures specified in the characterizing part of claim 1.

Further advantageous developments of the invention can be found in the subclaims.

Calculations, tests and model designs have shown that the tappet drive according to the invention fully meets the expectations placed in it.

Embodiments of the invention are shown in the drawings and are described in more detail below.

If, according to the state of the art, for example in the case of utility model 74 32 801, the movable part which is drawn between the pole shoes of the magnet is referred to as an anchor, this designation is inappropriate in connection with the invention. Because the term anchor connects the idea that this part mainly consists of soft magnetic material. Since this condition does not apply to the invention described below, the only anchor-like movement element is called "tongue" in one embodiment of the invention, in another "plunger". This is to emphasize that the "tongue" is not predominantly made of heavy soft magnetic material, but only of relatively narrow soft magnetic so-called anchor bars, which can be connected by non-magnetic light materials. In the case of the "ram", this designation is intended to indicate a cylindrical movement element. However, it should already be pointed out that both the "tongue" and the (cylindrical) "plunger" are generally covered by the designation "plunger" GE 9Rn O14E should be, which in both cases is only characterized by a different geometric shape.

The embodiment of the invention based on the priority of the German patent application P 29 26 278.8 (GE 979 026), in which the movement element is tongue-shaped, has an embodiment of the embodiment of the invention which is based on the priority of the German patent application P 30 18 407.7 (GE 980 014) Invention, in which the movement element is designed as a cylindrical plunger, certain disadvantages. The former embodiment is relatively complex to manufacture and is not yet optimal in terms of its volume and weight, especially if an overall width of 2.5 mm is desired. However, the former embodiment is less expensive than the second embodiment in terms of its magnetic stray fields which adversely affect the efficiency.

• Fign. 1A, 1B schematische Schnittdarstellungen eines schnellen elektromagnetischen Druckstößelantriebes mit einer beweglichen Zunge und beidseits der Zunge liegenden Jochhälften: Fig. 1A Ausgangsstellung; Fig. 1B Arbeitsphase,
• Fig. 2 eine schematische perspektivische Darstellung des Druckstößelantriebes gemäß Fig. 1 zur Verdeutlichung der Form der Zunge und des Verlaufes der die Joche umfassenden Erregerspulen,
• Fig. 3 eine schematische auszugsweise Schnittdarstellung einer Druckstößelbank mit kleinem Druckstößelabstand, bei der die den ein-GE 980 014E zelnen Druckstößeln zugeordneten Joche gegeneinander versetzt sind,
• Fig. 4 eine schematische auszugsweise Schnittdarstellung einer Druckstößelbank mit kleinem Druckstößelabstand, bei der jedem Druckstößel mehrere Joche zugeordnet sind und bei der die den einzelnen Druckstößeln zugeordneten Joche gegeneinander versetzt sind,
• Fig. 5 eine schematische perspektivische Darstellung einer Jochhälfte, welche von einer Folienspule als Erregerspule umfaßt wird,
• Fig. 6 eine schematische perspektivische Darstellung einer Zunge mit integriertem Hammerkopf,
• Fig. 7 eine schematische perspektivische Darstellung eines Elektromagneten mit Linearantrieb gemäß dem Stande der Technik,
• Fig. 8 eine schematische Darstellung eines Druckstößelankers mit zwei elektromagnetischen Treiberkreisen gemäß dem Stande der Technik.
• Fig. 9 eine schematische perspektivische Prinzipdarstellung eines Stößelantriebes, bei dem ein zylinderförmiger Druckstößel in den kreisförmig ähnlichen Arbeitsspalten zweier gegenüberliegender Jochhälften verläuft,
• Fig. 10 eine schematische Darstellung eines Druckstößelantriebes mit mehreren hintereinanderangeordneten Jochhälften,
• Fig. 11 eine Explosionszeichnung zur Erklärung des Zusammenbaues einer Druckstößeleinheit mit Druckstößel, Führungsstücken, Jochhälften, Flachrahmen und Federdraht,
• Fig. 12 eine schematische perspektivische Darstellung einer Druckstößelantriebseinheit,
• Fig. 13A eine schematische Darstellung zum Aufbau einer ersten Ausführungsform eines Stößels,
• Fig. 13B eine schematische Darstellung zur Herstellung einer zweiten Ausführungsform eines Stößels.

Show it:

• Fig. 1A, 1B are schematic sectional representations of a fast electromagnetic pressure tappet drive with a movable tongue and yoke halves lying on both sides of the tongue: FIG. 1A starting position; 1B working phase,
• 2 is a schematic perspective view of the pressure tappet drive according to FIG. 1 to illustrate the shape of the tongue and the course of the excitation coils comprising the yokes,
• Fig. 3 is a schematic excerpt sectional view of a pressure ram bank with a small pressure ram distance, in which the one-GE 980 014E yokes assigned to individual tappets are offset from one another,
• 4 is a schematic, partially sectional view of a pressure tappet bank with a small pressure tappet spacing, in which several pressure yokes are assigned to each pressure tappet and in which the yokes assigned to the individual pressure tappets are offset from one another,
• 5 shows a schematic perspective illustration of a yoke half, which is encompassed by a foil coil as an excitation coil,
• 6 shows a schematic perspective illustration of a tongue with an integrated hammer head,
• 7 shows a schematic perspective illustration of an electromagnet with a linear drive according to the prior art,
• Fig. 8 is a schematic representation of a pressure rod anchor with two electromagnetic driver circuits according to the prior art.
• 9 shows a schematic perspective illustration of a tappet drive in which a cylindrical pressure tappet runs in the circular working gaps of two opposite yoke halves,
• 10 is a schematic illustration of a pressure ram drive with a plurality of yoke halves arranged one behind the other,
• 11 is an exploded view for explaining the assembly of a pressure tappet unit with pressure tappet, guide pieces, yoke halves, flat frame and spring wire,
• 12 is a schematic perspective view of a pressure tappet drive unit,
• 13A is a schematic representation of the structure of a first embodiment of a plunger,
• 13B shows a schematic illustration for producing a second embodiment of a tappet.

FIG. 2 shows a schematic perspective illustration of an electromagnetic pressure tappet drive. A tongue 18 movable in the direction of arrow D is arranged between two fixed yoke halves 25, 22. The yoke halves 25 and 22 each consist of a magnetizable yoke 27 and 24, which is surrounded by coil turns 26 and 23, respectively. The yokes can e.g. be semicircular, semi-elliptical or also U-shaped. The yokes 27, 24 in the two yoke halves 25 and 22 are aligned such that the yoke ends opposite each other in the yoke halves are aligned. When the coils 26 and 23 are excited, the magnetic flux runs from a yoke over a working gap, in which the armature web is arranged, to the yoke of the other half of the yoke and from there via a further working gap back to the former yoke, so that the magnetic circuit comes out of the two yokes and the two working columns located between the ends of the yokes.

For the sake of simplicity, the following will speak of a pair of yokes (instead of a pair of yokes) for the opposing halves of the yoke.

The current flow in the excitation coils 26 and 23 takes place in such a way that the direction of current in the turns inside the two opposite yokes is the same and opposite to that in the turns outside the yokes. 2, the windings are indicated schematically in the front part of the illustration by a few wire loops, while in the rear part a corresponding sectional illustration of the wires has been selected. The tongue 18, which is movably arranged in the direction of arrow D between the yoke halves 25 and 22, is expanded in the direction of the working gap to be much smaller than in its other two dimensions. The body of the tongue 18 consists of a light, magnetically non-conductive material 19 and magnetically conductive, so-called anchor webs 20 and 21. These anchor webs are arranged in the tongue 18 so that they excite the yoke halves from a rest-starting position in the drawn between the yoke ends and thereby accelerated. The tongue can then follow a further movement in the direction of arrow D. The geometric design of the anchor webs 20 and 21 is essentially chosen so that their volume would fill approximately the space circumscribed between the ends of the yokes opposite. The associated advantages - increasing the efficiency - are described elsewhere.

In an advantageous embodiment of these anchor webs, a cuboid shape can be dispensed with in favor of a V-shaped configuration (see FIG. 1) seen in cross section. The advantages that can be achieved with this are also described elsewhere.

• Die Fign. 1A und 1B beziehen sich auf eine horizontale Schnittdarstellung der in Fig. 2 gezeigten Darstellung, mit der Einschränkung, daß die Joche halbkreisförmigen Verlauf aufweisen. In Fig. 1A ist die Ausgangsstellung, in Fig. 1B eine Stellung nach Abschluß der Beschleunigungsphase für die Zunge gezeigt. Die gleichen Teile der Darstellung in Fig. 1A und 1B tragen die gleichen Bezugszeichen. Die beiden Jochhälften sind mit 22 und 25 gekennzeichnet, die halbkreisförmigen Joche mit 24 und 27. Die die Joche umgebenden Wicklungen tragen die Bezugszahlen 23 (rechte Jochhälfte) und 26 (linke Jochhälfte). Der Stromverlauf im inneren Teil der beiden Magnetjoche ist durch das dafür vorgesehene Symbol als aus der Zeichenebene heraustretend gekennzeichnet; der Stromverlauf außerhalb der beiden Joche ist durch das dafür vorgesehene Symbol als in die Zeichenebene hineintretend angegeben. In dem Arbeitsspalt zwischen den beiden _Jochhälften befindet sich die mit 18 gekennzeichnete Zunge, welche aus den leichten magnetisch nichtleitenden Teilen 19 und den magnetisch leitenden Ankerstegen 21 und 20 besteht. Im Ausgangszustand (Fig. 1A) sind die Erregerspulen der Jochhälften zunächst nicht erregt. Für diese Ausgangsstellung sollen sich die Ankerstege 20 und 21 vor dem Raum, der zwischen den entsprechenden Enden der Joche gebildet wird, befinden. Beim Anlegen einer Spannung an die Erregerspulen der Jochhälften, die symmetrisch aufgebaut sind, werden durch magnetische Wirkung die Ankerstege in den Raum zwischen den Magnetjochenden hineingezogen und dabei beschleunigt. Dadurch bewegt sich die Zunge in angegebener Pfeilrichtung D, die die Druckrichtung symbolisieren soll. Nach Abschluß der Beschleunigungsphase nimmt die Anordnung eine in Fig. 1B gezeigte Position ein. Nach Fortfall der Erregung kann sich die Zunge weiter in Richtung des Pfeiles D bewegen. Die durch die Zunge zurückgelegte Wegstrecke von der Ausgangsstellung (siehe Fig.1A) bis zur Stellung nach Abschluß der Beschleunigungsphase (siehe Fig. 1B) wird als Beschleunigungshub bezeichnet; die danachfolgende weitere Auslenkung der Zunge in Richtung des Pfeiles D als Arbeitshub. Diese Größe ist von konstruktiven Randbedingungen abhängig sowie von den zur Lagerung der Zunge bzw. zur Rückführung der Zunge in seine Ausgangsstellung vorgesehenen Mitteln. Als solche Mittel können an sich bekannte Rückstellfedern (nicht dargestellt) verwendet werden: z.B. zwei Blattfedern, wie in der DAS 12 37 816 beschrieben, eine Feder im Zusammenwirken mit einer Gleitlagerung der Zunge oder eine Rückholfeder im Zusammenwirken mit einer schwenkbar um eine Achse bewegbaren Zunge. Auch eine elektromagnetisch bedingte Rückführung ist möglich.

When the excitation windings of both halves of the yoke are activated, the armature web 21 is accelerated into the space between the front ends of the yokes and the armature webs 20 into the space between the rear ends of the armature yokes. Further Information on the mode of action is given in connection with Figs. 1A and 1B made:

• The figures 1A and 1B relate to a horizontal sectional illustration of the illustration shown in FIG. 2, with the restriction that the yokes have a semicircular course. The initial position is shown in FIG. 1A, and a position after the end of the acceleration phase for the tongue is shown in FIG. 1B. 1A and 1B have the same reference numerals. The two halves of the yoke are identified by 22 and 25, the semicircular yokes by 24 and 27. The windings surrounding the yokes have the reference numbers 23 (right half of the yoke) and 26 (left half of the yoke). The current in the inner part of the two magnet yokes is identified by the symbol provided for it to emerge from the plane of the drawing; the current course outside the two yokes is indicated by the symbol provided for this purpose as entering the drawing plane. Ochhälften in the working gap between the two _J is the tongue marked with 18, which consists of the light magnetically non-conductive parts 19 and the magnetically conductive armature webs 21 and 20th In the initial state (FIG. 1A), the excitation coils of the yoke halves are initially not excited. For this starting position, the anchor webs 20 and 21 should be in front of the space which is formed between the corresponding ends of the yokes. When a voltage is applied to the excitation coils of the yoke halves, which are constructed symmetrically, the armature webs are drawn into the space between the magnet yoke ends by magnetic action and thereby accelerated. As a result, the tongue moves in the indicated arrow direction D, which is intended to symbolize the direction of pressure. After completion of the acceleration phase, the arrangement assumes a position shown in FIG. 1B. After the excitation ceases, the tongue can continue to move in the direction of arrow D. The distance covered by the tongue from the starting position (see Fig. 1A) to the position after the acceleration phase has ended (see FIG. 1B) is referred to as the acceleration stroke; the subsequent further deflection of the tongue in the direction of arrow D as a working stroke. This size depends on the structural boundary conditions and on the means provided for storing the tongue or for returning the tongue to its initial position. Known return springs (not shown) can be used as such means: for example two leaf springs, as described in DAS 12 37 816, a spring in cooperation with a slide bearing of the tongue or a return spring in cooperation with a tongue which can be pivoted about an axis . Electromagnetic feedback is also possible.

3 shows three pressure rams lying next to one another and arranged in a pressure ram bank 31. The plungers are marked with 28, 29 and 30, they each consist of a hammer head and the adjoining tongue. Each tongue is assigned a pair of yokes - consisting of two halves of the yoke. The two yoke halves for the pressure plunger 29 consist of the yoke 29-3 in connection with the excitation winding 29-5 and the yoke 29-4 in connection with the excitation winding 29-6. The yokes show a U-shaped course here. The yoke halves of the pressure plunger 28 consist of the yoke 28-3 in connection with the excitation winding 28-5 and the yoke 28-4 in connection with the excitation winding 28-6. For the pressure ram 30, the yoke halves are indicated by the yoke 30-3 in connection with the field winding 30-5 and the yoke 30-4 in connection with the field winding 30-6.

The yoke halves assigned to the tongue of a pressure tappet are aligned with one another. The pairs of yokes of the adjacent plungers are offset from one another, so that a compact design results with a minimized plunger spacing. The tongue of each pressure tappet 28, 29, 30 has corresponding anchor webs 28-1, 28-2; 29-1, 29-2; and 30-1, 30-2 on the excitation of the excitation coils in the yoke halves are accelerated into the space between the ends of the yokes, resulting in a movement in the direction of action D for the imprint of a character.

In Figure 4, three pressure rams 33, 34, 35 of a pressure ram bank are shown schematically. Each pressure tappet in turn consists of a pressure tappet head with an associated tongue. Several pairs of yokes are assigned to each anchor. For example, the pressure tappet 34 is assigned three pairs of yoke halves, namely that of the yoke 34-1-1 with associated excitation winding 34-1-5 and the yoke 34-1-3 with associated excitation winding 34-1-6 and that from the Yoke 34-2-1 with associated excitation winding 34-2-5 and yoke 34-2-3 with associated excitation winding 34-2-6 and ultimately that from yoke 34-3-1 and associated excitation winding 34-3-5 and the yoke 34-3-3 with associated exciter winding 34-3-6 existing yoke pair. To actuate the pressure plunger 34, all of the yoke halves assigned to it are excited simultaneously. The anchor bars 34-1-2 and 34-1-4 are accelerated into the space between the ends of the yokes 34-1-1 and 34-1-3; The same applies to the other bars 34-2-2 and 34-2-4 in connection with the yokes 34-2-1 and 34-2-3 and the anchor bars 34-3-2 and 34-3-4 in connection with yokes 34-3-1 and 34-3-3. The _J ochpaare adjacent tappets are offset from each other so that the distance between two adjacent push rod is determined by the dimensions of a yoke half including their associated field coil. In order to keep the mutual influence of adjacent tappets as small as possible, the current directions in successive pairs of yokes of the same tappet are opposite each other. As a result, the magnetic flux occurring in the intermediate yoke half of the neighboring tappets is very low.

The yoke halves lying between two pressure tappets can be cast in a common plastic block 36, 37. The holder of the tongues and the means for their resetting are conventional and are therefore not shown or described in more detail.

5 shows an embodiment of a yoke half which is particularly suitable for simple manufacture and simple installation. The U-shaped yoke 38 is surrounded by a foil coil 39 with the connections 40 and 41. One half of the coil fills the space formed between the legs of the U-shaped yoke.

FIG. 6 shows a schematic perspective illustration of a special embodiment of a tongue 43 with an integrated print head 49. The tongue 43 has a double-T-like profile with the cross-sectional areas 43-1, 45-1 and 44-1. In the vertically oriented, narrow tongue piece with the cross-sectional area 45-1, the anchor webs made of magnetically conductive material are identified with 45, 46 and 47. The areas in between are filled with a light material made of magnetically non-conductive material. The T-roof-shaped parts 43-1, 44-1 of the tongue serve to guide them laterally and vertically and to increase the lateral stability.

The tongue is provided at the front end with a plunger-shaped pressure hammer head 49, the cross-sectional representation of which from FIGS. 3 and 4 emerges.

7 shows an arrangement known according to the prior art (German utility model 74 32 801). This arrangement represents an electromagnet with a soft magnetic iron circuit separated at its pole ends by an air gap and a plunger armature. In its rest position, the armature projects into the working air gap and increases Excitation of the electromagnet a magnetically symmetrical working position between the aforementioned pole ends. The pole ends 3 and 4 of the iron circle 1 forming the working air gap 5 are formed as two planes lying opposite one another and the armature 6 as a flat component made of ferromagnetic material which can be displaced between these planes. The armature 6, which in its rest position partially bridges the working air gap 5 magnetically, is pulled out swingably against the return force RK when the electromagnet is excited, and is drawn into the working air gap until it assumes a magnetic symmetrical position between the pole ends.

From the description of the utility model application, the subject of which is shown in Fig. 7, it appears that the armature 6 is a flat part, the thickness of which corresponds approximately to the size of the working air gap between the pole pieces 3 and 4. In contrast, the anchor dimensions are much larger in the other two directions. In such a configuration of the armature, uncontrollable transverse forces inevitably result towards the pole pieces of the electromagnet, which prevent undisturbed movement in the desired direction of action. Furthermore, it can be seen from the description of this utility model that when the armature is in the initial position - that is, before the start of the working phase - a substantial part of the armature is already between the pole pieces so that the magnetic flux lines can pass through this part of the armature. However, the fact that such an arrangement requires a relatively low excitation current does not mean that the efficiency would also be high. The latter is relatively low, which is due to the large armature mass and the relatively large acceleration stroke in connection with high. ₁ ohmic losses in the excitation coil.

In Fig. 8 is known from the DAS 12 37 816 pressure ram drive for fast printers. In this electromagnetically actuated pressure tappet drive, a number of pressure tappets lying closely next to one another are provided. The armature 7, which can be moved in the direction D, is actuated by pressure magnets 12, 13 arranged on one side thereof. The pole faces 14 and 15 of the pressure magnet yokes are offset from the pole faces of flux guide pieces 16, 17 in the armature in the rest position in the longitudinal direction. In a special embodiment, the opposing pole faces 15, 14 of the magnetic yokes 12, 13 and the yokes 17, 16 located on the armature are inclined towards the writing point. The pressure tappet is mounted in a manner known per se on leaf springs 8 and 9 without a pivot point.

The arrangement according to FIG. 8 has various disadvantages: When driving the pressure tappet, forces occur transversely to its direction of movement, which forces have to be absorbed by the armature bearing (leaf springs 8 and 9). These forces occurring transversely to the direction of movement of the armature only partially contribute to an armature acceleration in the effective direction.

Furthermore, flux conductors 16 and 17, respectively, which have a large mass, are provided in order to conduct the magnetic flux in the armature. This mass must be accelerated in a printing process, which contributes to a reduction in efficiency. The special design of the flux guide pieces 16 and 17 in connection with the magnet yokes 12 and 13 assigned to them results in a stroke which is limited in the effective direction. The acceleration stroke has a relatively large value due to the inclined pole faces, which prevents high efficiency.

• In der Ausgangsstellung soll der Ankersteg an der Flußleitung nur einen vernachlässigbaren Anteil haben. Der Magnetfluß verläuft im wesentlichen über den zwischen den Enden der Joche liegenden Arbeitsspalt. Natürlich läßt es sich praktisch nicht vermeiden, daß ein vernachlässigbarer kleiner Teil der Magnetflußlinien in Ausgangsstellung der Druckanordnung über die Ankerstege verläuft. Um den Einfluß der Flußleitung über den Ankersteg in Ausgangsstellung gering zu halten, soll dieser im Querschnitt gesehen (Fig. 1) eine V-ähnliche Gestaltung erfahren. Nach Einschalten des Erreger Stromes und Aufbau des magnetischen Feldes werden die Ankerstege in den Raum zwischen die beiden Joche gezogen und auf diesem Wege beschleunigt. Die hierbei zu beschleunigende Masse ist aufgrund der geringen geometrischen Ausdehnung der Ankerstege klein, wodurch die Zunge eine hohe Beschleunigung erfährt. Hinzu kommt, daß zur Erreichung einer bestimmten Endgeschwindigkeit unter Berücksichtigung der vorgegebenen Randbedingungen nur ein kleiner Beschleunigungsweg erforderlich ist. Dadurch ist nur eine relativ geringe Zeit zur Beschleunigung des Läufers erforderlich, wodurch die auftretenden Ohmschen Verluste in den Erregerspulen gering gehalten werden.

The in the Figs. 1 to 6 pressure ram drive is characterized by the following advantages:

• In the starting position, the anchor bridge on the river line should only have a negligible proportion. The magnetic flux runs essentially over the working gap between the ends of the yokes. Of course, it is practically unavoidable that a negligible small part of the magnetic flux lines in the starting position of the pressure arrangement runs over the anchor webs. In order to keep the influence of the flow line over the anchor web low in the starting position, this should be seen in cross-section (FIG. 1) in a V-like design. After switching on the excitation current and building up the magnetic field, the anchor bars are pulled into the space between the two yokes and accelerated in this way. The mass to be accelerated is small due to the small geometric extension of the anchor bars, which means that the tongue experiences a high acceleration. In addition, only a small acceleration path is required to reach a certain top speed, taking into account the specified boundary conditions. As a result, only a relatively short time is required to accelerate the rotor, as a result of which the ohmic losses that occur in the excitation coils are kept low.

The low mass of the armature webs and the low ohmic losses in the excitation coils during the acceleration phase result in a high efficiency of the pressure ram drive.

The comment about the relatively short acceleration path for the tongue should not, however, imply that the acceleration stroke is the same as the working stroke. At this point it should be expressly pointed out that after the pressure plunger has accelerated, it continues to fly in the effective direction and thus ensures a large working (pressure) stroke after the excitation coil is switched off.

Furthermore, other factors are involved in achieving the high efficiency: The symmetrical arrangement of the yoke halves ensures that the so-called magnetic transverse forces in the direction of the yokes are zero in the first approximation, thereby avoiding friction losses and thus reducing the efficiency by these influences is avoided.

Another essential advantage of the pressure ram drive according to the invention lies in the space-saving design. The yokes are never larger than the excitation coil itself; in addition, the yoke halves are arranged on both sides of the pressure ram. In the case of pressure rams lying next to one another, their mutual spacing can be reduced by displacing the yoke halves assigned to the pressure rams so that the distance between two adjacent pressure rams is determined by the geometric dimension of a yoke half. In addition, it is possible to assign a plurality of yoke pairs arranged one behind the other to a pressure tappet in order to increase the final speed without thereby increasing the mutual spacing of the tappets.

This avoids the tappet mechanism of conventional printer drives, which used to be very bulky.

The small cross-section of the yokes minimizes eddy current and magnetic reversal losses, which contributes to a further increase in efficiency. The low cost of materials for the yokes and the anchor bars makes it possible to use relatively expensive material for these parts. The material expenditure for the formation of the anchor bars almost corresponds to the theoretical minimum: It is now possible for the first time to use only as much material (for the anchor bars) as for filling the working air gap volume is required (mass optimization). Any flow line pieces in the armature can be omitted, whereby flow flow pieces of the armature are to be understood as those parts which carry a substantial part of the total magnetic flux in each position of the pressure tappet drive.

The embodiment of the arrangement according to FIG. 2 is aimed at a relatively flat design of the tongue. Flat in this context means that the thickness of the tongue is much smaller than its width and length.

• - insbesondere bei einer Verwendung mehrerer solcher Anordnungen in Druckhammerbänken - besondere Schwierigkeiten. Diese Schwierigkeiten werden dann besonders groß, wenn geringe Baubreiten der einzelnen Druckantriebseinheiten angestrebt wurden. Für eine übliche Schriftzeichendichte müßten Baubreiten von nur 2,5 mm angestrebt werden. Jedoch sind
• - durch die geringe Dicke der Zunge bedingt- Verstärkungsrippen in Bewegungsrichtung der Zunge erforderlich. Diese über und unter der Zunge verlaufenden Verstärkungsrippen dienen zugleich auch der exakten Führung. Sie müssen über bzw. unter den Erregerwicklungen verlaufen, wodurch die Höhe und die Masse der Zunge wesentlich ansteigen. Für eine Anordnung mit einer Zunge und mehreren hintereinander angeordneten Jochhälftenpaaren (geringerer Höhe) steigt der Anteil der unerwünschten "toten" Masse in den Verstärkungsrippen auf über 50 % der Gesamtmasse der Zunge. Andererseits ist jedoch das Hintereinanderreihen mehrerer Teilsysteme wünschenswert, weil dadurch die Bauhöhe der Zunge gering gehalten werden konnte. Um ohne wesentliche Biegebeanspruchung der Zunge drucken zu können, ist eine Zungenhöhe in der Größenordnung der zu druckenden Buchstabenhöhe anzustreben; dies ist jedoch mit einem Antrieb gemäß Fig. 2 nur dann möglich, wenn mindestens drei hintereinander anzuordnende Jochhälftenpaare mit einer gemeinsamen Zunge vorgesehen werden (Fig. 4). Hierbei übersteigt jedoch, wie bereits erwähnt, die für die Verstärkungs- bzw. Führungsrippen erforderliche Zusatzmasse die eigentliche Zungenmasse. Außerdem ist die Herstellung des Arbeitsspaltes zwischen den Jochhälften mit der dafür vorzusehenden erforderlichen Präzision äußerst kostenaufwendig.

This geometric specification inevitably results

• - Especially when using several such arrangements in printing hammer banks - special difficulties. These difficulties become particularly great when small overall widths of the individual pressure drive units have been sought. For a common character density, widths of only 2.5 mm would have to be aimed for. However are
• - Due to the small thickness of the tongue - reinforcement ribs in the direction of movement of the tongue required. These reinforcing ribs running above and below the tongue also serve for precise guidance. They must run above or below the excitation windings, which causes the height and mass of the tongue to increase significantly. For an arrangement with a tongue and several pairs of yoke halves arranged one behind the other (lower height), the proportion of the undesired "dead" mass in the reinforcing ribs increases to over 50% of the total mass of the tongue. On the other hand, however, the sequential arrangement of several subsystems is desirable because the overall height of the tongue could be kept low. In order to be able to print without significant bending stress on the tongue, a tongue height in the order of the letter height to be printed should be aimed for; however, this is only possible with a drive according to FIG. 2 if at least three pairs of yoke halves to be arranged one behind the other are provided with a common tongue hen will be (Fig. 4). However, as already mentioned, the additional mass required for the reinforcement or guide ribs exceeds the actual tongue mass. In addition, the production of the working gap between the yoke halves with the required precision to be provided for this is extremely costly.

To avoid these disadvantages, it is important to show another embodiment for an inexpensive, space-saving design of very light tappet drive units, in particular for pressure hammer drives.

This makes it possible to line up the tappet drive units so closely to one another when used in printing hammer banks that the width of a unit becomes equal to the spacing of adjacent letters to be printed. The reason for this space-saving design is that the coil windings no longer run between the plungers lying next to one another, but rather that they are now fitted above and below the plungers within the drive unit.

9 shows a schematic perspective illustration of an electromagnetic tappet drive. The cylinder-shaped tappet shaft is provided with the reference number 210. The direction of action of the tappet shaft points in the direction of the arrow 1D. The tappet shaft 210 is composed of anchor rings or anchor disks 220, 230, which are separated from one another by a spacer element 240. In contrast to the spacer element 240, the armature rings or armature disks 220 and 230 consist of magnetizable material. A magnet yoke 250 that can be excited via a coil is provided for driving the plunger. This magnetic yoke 250 consists of two U-shaped yoke halves with the legs (pole pieces) 260, 270 or 118, 119 and the base 290 or 280. The base is connected to two pole pieces in each case. The pole pieces of the halves of the yoke lie in contact-free the opposite. Each pole piece is provided with a semicircular recess for receiving the plunger shaft 210. The tappet shaft 210 moves in this recess in the direction of the arrow 1D (or in the opposite direction). Between the pole pieces there is a circular working gap 111 or 112. The outer ends of the pole pieces surrounding the plunger shaft 210 are chamfered on the side facing away from the plunger (113A, 113B, 114A, 114B). The base (coil core) 290 carries a partial winding 110. For reasons of clarity, the illustration of a further partial winding on the coil core 280 has been omitted. When the winding is excited, a magnetic flux is generated in the magnetic yoke 250 which closes via the pole shoes 260, 118, 119, 270 to form a magnetic circuit. Due to the effect of this magnetic flux, the armature rings 220, 230 (armature disks) of the plunger shaft 210 (which are in the non-excited state of the arrangement immediately in front of the working gaps 111, 112) are drawn into the working gap, which results in a corresponding acceleration of the plunger shaft in the direction of the arrow 1D. For such a function, the armature disks must be made of magnetizable material. The more the magnetic flux closes from one pole shoe to the other via the armature disks 220 and 230 and does not run towards the pole watch without passing through the armature ring, the more efficient is the ram acceleration. For the latter reason, the pole shoes are chamfered at the edges (113A, 113B, 114A, 11 4B).

In Fig. 9 it has already been indicated that such a tappet drive can consist of a plurality of magnet yokes arranged one behind the other in the direction of the tappet shaft. With such an arrangement, adjacent coil cores (280/117 and 290/115) would act together on a pair of pole shoes (270 and 119). To the full when the magnetic yoke is excited Maintaining the acceleration force on the plunger shaft (210) in the direction of the arrow 1D must be paid particular attention to the winding direction of the windings seated on the individual coil cores. The winding direction is opposite from coil core to coil core (290/115). This is the only way to ensure that the magnetic flux does not cancel out in the two adjacent pole yokes 270 and 119. The winding direction of the partial coil 110 for the coil core 290 and the partial coil 116 for the coil core 115 is opposite. The same applies to the sense of winding of the partial coils, not shown, for the coil cores 280 and 117.

The representations in FIGS. 10, 11 and 12 relate to a practical embodiment of a pressure ram drive unit 130 which is intended for use in line printers. If previously there was talk of so-called print hammer drives on corresponding printers (electromagnetically operated print hammers which struck a type to be printed), such a designation is no longer justified in the present "plunger drive". The general characteristic of a print hammer drive was an anchor of incomparably greater mass than would have been necessary to print the type. To keep the action during the printing process surcharge mass (effective mass) still as low as possible, it was necessary, a corresponding small _A ufschlagmasse a leverage with the large armature mass to join. This characteristic is no longer present in the present pressure tappet, since anchor mass and effective impact mass are identical. With this tappet, magnetizable sub-areas are drawn into the working gap of an electromagnetic circuit and accelerated in the process. The plunger only performs a linear movement, in contrast to the circular path movement of a pressure hammer. This new kind Drive is therefore called (pressure) tappet drive. A pressure tappet drive unit 130 serving to drive such a pressure tappet 132 is shown in perspective view in FIG. 12. To explain their mode of operation, reference is also made to the representations in FIGS. 10 and 11. In Figs. 10, 11 and 12 the same parts are identified by the same reference numerals.

10 serves in particular to illustrate the magnetic flux in the individual magnet yokes arranged one behind the other, while FIG. 11 shows an exploded view of various individual parts of the pressure tappet drive unit 130 for information on assembling this arrangement. It serves for a better understanding if, when a reference number is mentioned, the corresponding part is not only shown in FIG. 11, but - if available - also in FIGS. 10 and 12 is considered.

The pressure tappet drive unit 130, designed as a narrow, flat part, consists of a frame 131. This frame 131 is provided with a recess 142. This recess serves, among other things, to accommodate the magnetic coil system 159 (electromagnet unit), which is firmly fixed (glued or cast) in the recess 142. The frame 131 is provided with two bores 143 and 144, which serve as guide holes for the cylinder-shaped plunger 132. This plunger consists of a plunger 133 and the plunger shaft 134. The plunger shaft can be driven in the axial direction in the direction of the arrow 1D, the plunger 133 serving as a stop element against a printing type or the paper to achieve a desired impression. The plunger shaft runs within the magnetic coil system 159 in a recess provided in this. At its end remote from the pressure, the frame 131 is continued in two frame arms. 145 and 146. The end of the tappet shaft 134 remote from the pressure projects into this space between the two frame arms 145 and 146. The end of the tappet shaft 134 is provided with an elongated hole 158 for receiving a spring wire 135 provided, which is attached to one of the frame arms 146 on one side. This attachment is provided by a bracket 137 which can be adjusted with a screw in the frame 131 and by means of which the spring force of the spring wire 135 can also be adjusted. The spring wire 135 protrudes through an elongated hole 139 of the frame arm 146 and is connected at point 136 to the tab 137 arranged on the outside of the frame 131. The spring wire 135 can be fastened at point 136 either by welding, gluing or other conventional measures. The tab 137 is provided at its end remote from the point 136 with a cutout 161 which, when the screw 138 is loosened, allows the tab to be displaced parallel to the axial direction of the pressure tappet shaft in order to make a corresponding adjustment of the spring force of the spring wire 135. The tab 137 is connected to the pressure frame 131 by the screw 138. The task of the spring wire 135 is to bring the pressure tappet 132 back after the printing process has been completed and to secure the tappet against rotation. In the frame 131 there are furthermore two connecting pins 140 and 141 electrically insulated from the frame for connecting the coil of the magnetic coil system 159. For reasons of clarity, the connection pins have not been connected to the ends of the sub-windings 150 and 151 which are connected to one another. The magnet coil system 159 is composed of a total of 6 electromagnetic circuits arranged in series according to FIG. 9. As already mentioned, in such a series, two adjacent electromagnetic circuits have a pair of pole pieces in common. To explain further details of the magnetic coil system 159, reference is first made to the illustration in FIG. 11. The yoke parts of the series-arranged electromagnetic circuits consist of a core for an upper coil comb 147 and a core for a lower coil comb 160. The core for the upper coil comb 147 is composed of a comb back 148, on which at appropriate intervals the comb teeth 148/1, 148/2, 148/3, 148/4, 148/5, 148/6 and 148/7 serving as pole shoes are arranged. The same applies analogously to the core of the lower coil comb 160 with the comb back 149 and the comb teeth 149/1 to 149/7 serving as pole shoes. The cores for the upper and lower coil combs 147 and 160 are made of magnetizable material. As shown in FIG. 9, the pole shoes are designed such that, in the assembled state of the magnetic coil system, the pressure tappet shaft 134 is arranged to be movable between them. The pressure ram shaft 134 is guided in the frame bores 143 and 144 and in the guide bores of the non-magnetizable guide pieces 152, 153, 154, 155, 156, 157. These guide pieces are each arranged within a single magnetic yoke circuit so that their bores are aligned with the bores 143 and 144 in the frame 131. The magnetic coil system is cast in plastic and is arranged in a recess 142 in the frame 131. The arrangement of the windings within the magnet coil system is discussed below: The coil consists of two interconnected partial windings 150 and 151. The partial winding 150 is assigned to the lower coil comb 160, the partial winding 151 is assigned to the upper coil comb 147. The partial windings sit on the back of the comb 149 or 148. It should be noted that the sense of winding on the coil core alternates between two pole pieces for each successive section. Accordingly, the winding sections 150/1, 150/3, 150/5 have the opposite winding sense as the winding sections 150/2, 150/4 and 150/6. The same applies to the winding direction of the winding sections on the upper coil comb 147, in which the winding sections 151/1, 151/3 and 151/5 have the opposite winding direction as the winding sections 151/2, 151/4 and 151/6. In order to achieve an action force of the pressure tappet, the excitation current must flow through the lower partial windings (e.g. 150/1) and the upper partial windings (e.g. 151/1) of a yoke circuit in such a way that their magnetic fluxes are not mutually exclusive cancel. It should be noted that the winding can be applied to the cores for the individual coil combs in a simple manner (which was not the case with an arrangement according to FIG. 2). After the individual parts of the magnetic coil system have been cast and fixed in place in the recess 142 in the frame 131 (which can also be done by casting), only the pressure plunger 132 provided for this system is to be inserted into the guide opening which is specifically kept open for this purpose. The pressure tappet, as shown in FIG. 11, consists of a number of armature disks 134/1, 134/2, 134/3, 134/4, 134/5, 134/6, 134 / .7 corresponding to the pole shoe pairs made of magnetizable material. These individual armature disks are separated from one another by spacer elements 134-1 / 2, 134-2 / 3, 134-3 / 4, 134-4 / 5, 134-5 / 6, 134-6 / 7. In addition, further spacers 134-O / 1 and 134-7 / 8 are provided at the near-pressure and far-away end. Spacers and anchor plates are firmly connected. Further details are given below on the various possibilities for producing such a pressure tappet. The individual armature disks are spaced apart from one another in such a way that, when the magnet coil system is not activated, they lie directly in front of the working gaps between the individual pole shoe pairs. When the magnetic coil system is activated, the magnetizable armature disks are drawn into the working gap, the entire plunger being accelerated for a subsequent pressing process.

FIG. 10 shows a schematic sectional illustration of the parts of the upper and lower coil combs 147 and 160 which are decisive for the magnetic flux within the individual yoke circles as shown in FIG. 12. The sectional plane lies parallel to the frame surface and leads through the axis of the pressure plunger 134. The comb back are marked with 148 and 149 respectively. The individual comb teeth (pole shoes) with 148/1 to 148/7 and 149/1 to 149/7. For reasons only the lower partial winding 150 with the winding sections 150/1 to 150/6 is shown in the overview. It can be seen that the winding direction of successive winding sections alternates with one another so that the magnetic fluxes of adjacent yoke circles in the pair of pole shoes common to these yoke circles do not cancel each other out. 10, the pressure ram assumes such a position that the individual armature plates 134/1 to 134/7 are still in front of the working gaps. The pressure plunger would be moved in the direction of the arrow 1D when the excitation was indicated by the magnetic flux directions, the magnetizable armature disks being drawn into the working gap between the pole shoes and thereby accelerated.

In Figs. 13 _A and 13B show different possibilities for producing and assembling the pressure ram.

In a first embodiment according to FIG. 13A, the individual armature disks 134A and the spacer elements 162 to be arranged between them are screwed onto a common tappet shaft liner 163, which is designed as a threaded pin. All parts can be glued together. If the ram is subsequently ground, a very high accuracy of the ram diameter can be achieved. The armature plates 134A and the spacer elements 162 must have very small length tolerances in order to ensure an exact spacing of the individual armature plates 134A. However, an exact armature plate division is a prerequisite for good efficiency.

The difficulties in producing a tappet according to FIG. 13A can be avoided if the armature disks 134B and the tappet shaft core 164 connecting them are turned in one piece according to FIG. 13B. With such a production, an exact armature disk division can be provided. This is used to manufacture a complete plunger Part connected with a punch 133 (see FIG. 12) and an end part with the elongated hole 158 (see FIG. 12) by means of a plastic embedding. Subsequent rounding then results in the desired dimensional accuracy.

At this point it should be mentioned that in the embodiment according to FIG. 13B the tappet shaft core 164 as well as the anchor rings 134B are made of the same magnetizable material. For the effectiveness of the arrangement, it is important that the diameter of the tappet shaft core is relatively small compared to the diameter of the armature disks 134B, since the tappet shaft core has an albeit small share in an undesirable magnetic flux line. From the point of view of optimal effectiveness, the space between the armature disks should consist entirely of non-magnetizable material. Such a requirement can, however, be waived for manufacturing reasons if the disadvantage of a slight reduction in effectiveness is accepted. By means of suitable material pairing for the guide pieces 152 to 157 and the tappet shaft 134, the pressure tappet 134 can be smoothly seated in the guide bores 143 and 144 without the need for lubrication.

The plunger drive described above can be used in many ways, especially when it comes to the generation of forces, paths, impulses or kinetic energies or switching operations that are controlled by contacts to be actuated by the plunger.

Furthermore, the described tappet drive can be used bidirectionally if the armature disks assume defined end positions in front of or behind the working gaps.

As has already been pointed out, the tongue-shaped ram drive has the advantage over the cylindrical ram drive better efficiency because the magnetic stray fields are lower.

It should also be noted that the two described embodiments can be combined accordingly to combine certain advantages.

For example, it is also conceivable to provide common coil combs for the embodiment shown in FIG. 2 in a multiple arrangement according to FIG. 12.

Claims (27)

1. electromagnet with working gap into which a displaceable armature element made of magnetizable material is drawn when the electromagnet is excited,
characterized, that the electromagnet consists of two essentially symmetrically constructed magnetizable yoke halves (24, 27, 260/270/290, 118/119/280), at least one of which is surrounded by a coil (23, 26, 110), that the facing pole ends of the yoke halves form two aligned working gaps, that a plunger (18, 210) which can be displaced in the direction of the alignment of the working column and has a cross section which is adapted to the area of the working column is arranged between these working columns, that the plunger (18, 210) has two anchor elements (20, 21; 220, 230) made of magnetizable material and a spacer element (240) made of predominantly non-magnetizable material arranged between these anchor elements, that an anchor element (20, 21; 220, 230) is assigned to each working gap, that the anchor elements (20, 21; 220, 230) have such a geometric design that their volume is of the order of the working gap volume, that the anchor elements (20, 21; 220, 230) are in the starting position of the plunger (18; 210 ) are in the non-excited state of the electromagnet essentially in front of its working gaps and when the electromagnet is excited. magnets are drawn into this working column. 2. Arrangement according to claim 1,
characterized,
that the anchor elements (20, 21) have a cuboid shape, the extension in the direction of movement (D) of the plunger in the order of the width of the Working gap is, and the extent perpendicular to it is a multiple of this dimension. 3. Arrangement according to claim 1 and claim 2,
characterized,
that the plunger (18) has a flat design, the dimensions between the pole ends of the yoke halves (24, 27) are incomparably smaller than in the other directions. 4. Arrangement according to claims 1 and 2,
characterized,
that the yoke halves (24, 27) are U, semi-circular or semi-elliptical. 5. Arrangement according to claim 4,
characterized,
that the coils surrounding the yoke halves (24, 27) are designed as foil coils (39). 6. Arrangement according to claim 1,
characterized,
that the anchor elements (20, 21) have a V-shaped profile, the V being open in the direction of movement (D) of the plunger (18). 7. Arrangement according to one of claims 1 to 6,
characterized, that for several plungers (33, 34, 35) arranged next to one another, each plunger (34) has one or more pairs of yoke halves (34-1-1, 34-1-3; 34-2-1, 34-2-3; 34-3 -1, 34-3-3) are assigned, which are offset from each other so that the ram distance is determined by the dimensions of a yoke half (34-1-1) with the coil (34-1-5) assigned to it. 8. Arrangement according to claim 7,
characterized,
that the yoke halves (34-1-1, 33-1-3, 34-2-1, 33-2-3, 34-3-1) lying between two plungers (33, 34) with the coils (34 -1-5, 33-1-6, 34-2-5, 33-2-6, 34-3-5) are cast in a plastic block (36). 9. Arrangement according to claim 7,
characterized,
that the plunger (44) is connected to T-shaped guide elements (43, 42). 10. Arrangement according to claim 1,
characterized, that the mutually facing pole ends of the yoke halves (260/290/270; 118/280/119) are recessed essentially semicircularly and form essentially circular working gaps (111, 112), that the plunger (210) is cylindrical and the anchor elements (220, 230) are disc-like. 11. The arrangement according to claim 10,
characterized,
that the plunger (210) consists of a threaded pin (163) designed as a plunger shaft core, onto which disk-shaped anchor elements (134A) and cylindrical spacer elements (162) separating them are screwed. 12. Arrangement according to claim 10,
characterized,
that for the tappet (210) the anchor elements (134B) and a tappet shaft core (164) connecting them are made from a piece of the same material and that the space remaining between the anchor elements (134B) is filled with a plastic (165). 13. Arrangement according to claims 1 and 10,
characterized,
that the yoke halves (260/270/290; 118/280/119) are U-shaped and are surrounded by a coil on their base (290, 280). 14. Arrangement according to claim 10 or 13,
characterized,
that the opposite pole ends of the yoke halves are chamfered (113A, 113B, 114A, 114B) on the side facing away from the tappet (210). 15. Arrangement according to one of claims 10, 13 or 14,
characterized,
that several pairs of yoke halves (148-1, 148-2 / 149-1, 149-2; 148-2, 148-3 / 149-2, 149-3 etc.) are arranged one behind the other in such a way that two adjacent yoke halves form a yoke section (148-2, 148-3) have in common and that a pressure tappet (132) common to all pairs of yoke halves is provided. 16. Arrangement according to claim 15,
characterized,
that all adjacent yoke halves each have a partial winding (150-1, 150-2, 150-3, 150-4, 150-5, 150-6, 151-6, 151-5, 151-4, 151-3, 151- 2, 151-1) of a coil common to all yoke halves (150, 151), and that the partial windings of adjacent yoke halves have an opposite winding direction. 17. Arrangement according to one of claims 1 to 9 or 15 to 16,
characterized,
that adjacent yoke halves have a coil core (147, 160) forming a continuous comb back (148, 149) with individual comb teeth (148-1 to 148-7; 149-1 to 149-7) designed as pole pieces. 18. Arrangement according to one of claims 15 to 17,
characterized,
that opposite coil cores (147, 160) with the coil (150, 151) and with between them (147, 160) arranged guide pieces (152 to 157) for the plunger (132) are cast in plastic to form an electromagnet unit. 19. Arrangement according to claim 18,
characterized,
that the electromagnet unit is arranged within the recess (142) 'of a flat and narrow frame (131) of a pressure tappet drive unit (130). 20. Arrangement according to claim 19,
characterized,
that the electromagnet unit is glued to the frame (131) or cast in plastic with it. 21. Arrangement according to one of claims 19 or 20,
characterized,
that the plunger (132) is guided in two bores (143, 144) of the frame (131). 22. The arrangement according to claim 21,
characterized,
that the plunger (132) has at its distal end a recess (158) for receiving a spring wire (135) fixed on one side to a frame leg (146). 23. Arrangement according to one of claims 1, 2, 3, 6, 7 or 8 or 10 to 22,
characterized,
that the plunger (18, 210, 132) upon excitation of the electromagnet in the direction of the working column escape line is accelerated and can be moved further in the pressure direction (D, 1D) after the excitation is switched off. 24. Arrangement according to one of claims 1 to 23,
characterized,
that the return of the deflected plunger (18, 132) into its starting position via a spring (135) or by excitation of the electromagnets. 25. Application of the arrangement according to one of claims 1 to 24, for the electromagnetic drive of impact printers. 26. Arrangement according to claim 25,
characterized,
that the plunger (18, 132) carries a stamp (133) as a print hammer head at its end near the pressure. 27. Arrangement according to claim 23,
characterized,
that the plunger is rotatably mounted on an axis.

Images