Electromagnetic Drive For Data Indication

Abstract

Electromagnetic drive for data indication includes a shell core-like magnet core, an excitation coil surrounding the magnet core, the magnet core having an inner sleeve-shaped core portion extending through the excitation coil, the inner core portion being formed with an air gap separating the inner core portion into two parts each formed with a magnetic pole, indicating means, and a plunger polarized in longitudinal direction thereof operatively connected to the indicating means, the plunger being freely displaceably disposed within the sleeve-shaped inner core portion and being displaceable from a neutral position thereof to a position wherein the indicating means are effective to provide an indication.

Description

The invention relates to electromagnetic drive for data indication wherein indicating means are transferred by a plunger from neutral position thereof to indicating position thereof.

Heretofore known electromagnetically operated indicating systems such as wire, mosaic or typewheel printers or perforators or the like, operate in a manner wherein, for example, either the printing wire proper or printing hammer of the amature lever of a magnet system, for example, a plunger-magnet system, is struck or the armature lever of the magnet system proper is constructed as the indicating means (note German Published Application DAS 1,179,228 and 1,262,053). A pre-stressed restoring spring serves in most cases for returning the armature lever to the neutral position thereof after an indication has taken place (note German Published Application 1,253,940). Such drive systems have the disadvantage, however, that the force of the spring acting in opposite direction to the direction of displacement of the armature in the indicating direction, reduces the speed thereof, so that the speed of indication is considerably impaired. A constant striking force on the indication carrier is not assured because the springs are subject to wear in the course of time or a change occurs in the spring constant thereof. It is furthermore disadvantageous that the effective mass of the armature, because the armature lever of the magnetic system proper is constructed as the indicating means, is too large so that such drive systems are able to be used only for slowly operating output devices because of the ponderousness resulting from an adverse pole surface-to-mass ratio and above all because of the large space requirement therefor.

It is accordingly an object of the invention to provide electromagnetic drive for data indication which avoids the foregoing disadvantage of the heretofore known electromagnetic drives of this general construction and more specifically, to provide an electromagnetic drive system of the plunger-magnet system type for data indication which is a major improvement over the heretofore known devices of this general type with respect to operational reliability and simplicity of construction, and does not require the use of additional mechanical components that are subject to wear. With the foregoing and other objects in view, there is provided in accordance with the invention, electromagnetic drive for data indication comprising a shell core-like magnet core, an excitation coil surrounding the magnet core, the magnet core having an inner sleeve-shaped core portion extending through the excitation coil, the inner core portion being formed with an air gap separating the inner core portion into two parts each formed with a magnetic pole, indicating means, and a plunger polarized in longitudinal direction thereof operatively connected to the indicating means, the plunger being freely displaceably disposed within the sleeve-shaped inner core portion and being displaceable from a neutral position thereof to a position wherein the indicating means are effective to provide an indication.

In accordance with another feature of the invention, the length of the sleeve-shaped core portion has a length which is a multiple of the length of the plunger, and the air gap is located in the middle of the coil so that the plunger, as viewed in direction of displacement thereof, is surrounded entirely or partly by one of the magnet poles in the neutral position, and is surrounded by both of the magnet poles-indicating position of the plunger.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in electromagnetic device for data indication, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

FIGS. 1 through 3 are diagrammatic longitudinal sectional views of the electromagnetic drive for data indication according to the invention shown in three different phases, namely in neutral or off-position, in indicating position, and after data indication, respectively;

FIGS. 4 and 5 are diagrams of circuits for triggering the electromagnetic drive; and

FIG. 6 is a longitudinal sectional view of an actual embodiment of the electromagnetic drive of the invention.

Referring now to the drawing, and particularly to FIG. 1 thereof, there is shown diagrammatically the electromagnetic drive of the invention, which is in the form of a plunger-type magnet system for data indication, and includes a shell core-like magnetic core 1 cylindrically surrounding an excitation coil 3 mounted on a coil form 2. The core part 7 passing through the interior of the coil is of sleeve-like construction and has an air gap 4 in the center of the coil so that two magnetic poles 5 and 6 are formed, respectively, having effective pole ends shaped conically on the exterior thereof for the purpose of avoiding unnecessary leakage losses. Within the sleeve-like core part 7, a plunger 8 polarized in longitudinal direction is freely displaceably disposed, indicating means 9 in the form of a printing wire being secured thereto. The plunger 8, in the phase illustrated in FIG. 1, is in neutral position, as indicated by the fact that no current is shown traversing the magnet coil 3, and is completely inserted into the sleeve-like magnet pole 6 where it is retained permanent-magnetically. The length of the core part 7 is a multiple of the length of the plunger 8. A stop 10 of non-magnetic material, preferably of plastic material, serves as a position-securing device for the plunger 8 and is provided with a ventilation or air hole 11 to avoid air damping. An indication carrier, represented diagrammatically by the line 12, against which the printing wire 9, connected to the plunger 8, directly strikes.

In the indicating-position phase of the electromagnetic drive of the invention shown in FIG. 2, the polarized plunger 8 is located in the air gap 4 between the magnet poles 5 and 6 where it is equally surrounded by both of the magnet poles 5 and 6 so that a closed magnetic circuit is formed, the magnetic field produced by the excitation coil 3 being represented by the dotted line, as shown. To transfer the plunger 8 from the off-position thereof of FIG. 1 into the indicating position thereof of FIG. 2, voltage is applied to the excitation coil 3 so that the magnetic field that is formed in opposite in direction to that of the outer magnetic field of the plunger 8. By reversing the polarity of the current direction in the excitation coil 3, the direction of the magnetic field is reversed (note FIG. 3), so that the plunger 8, because it is polarized, is driven out of the air gap 4 back into the off-position thereof wherein, as mentioned hereinbefore, it is retained permanent-magnetically after the excitation voltage has been switched off. The polarity reversal of the current direction preferably occurs at the instant the printing wire indicating means 9 strikes the indication carrier 12. The displacement of the plunger 8 back into the original location thereof shown in FIG. 1 is reinforced in this way by the rebound thereof from the indication carrier 12.

The circuits shown in FIGS. 4 and 5 serve to control the foregoing operation of the electromagnetic drive for data indication constructed in accordance with the invention. FIG. 4 shows the aforementioned excitation coil 3 having one terminal thereof connected through a capacitance 13 and a selector switch 15 to a reference voltage source OV, and the other terminal thereof through a series resistance 16 to a positive voltage +U. Furthermore, a discharge resistor 14 is provided which, upon reversing the switch 15, is connected in parallel with the series connection formed by the excitation coil 3 and the capacitance 13. The position of the selector switch 15 shown in FIG. 4 corresponds to the neutral position of the plunger 8 in the phase illustrated in FIG. 1. The capacitance 13 is charged, and no current flows through the excitation coil 3. The charging time depends upon the dimensioning or rating of the series resistance 16 and the excitation coil 3. For an indicating operation, the position of the selector switch 15 is varied so that the capacitance 13 discharges through the discharge resistance 14. The discharge current consequently flowing through the excitation coil 3 produces a magnetic field (note FIG. 2) which transfers the plunger 8 rapidly into the indicating position thereof. Resetting of the selector switch 15 to the original position thereof shown in FIG. 4 results in renewed charging of the capacitance 13 with opposing current direction (note FIG. 3) so that the plunger 8 rapidly returns to the neutral position thereof shown in FIG. 1.

The circuit diagrammatically shown in FIG. 5 corresponds in construction to that shown in FIG. 4, with the difference, however, that the selector switch 15 of FIG. 4 is replaced by two transistors 15a and 15b in FIG. 5. The pulse diagrams shown in FIG. 5 at the bases of the transistors 15a and 15b indicate that in neutral position of the plunger 8 the transistor 15a is conductive and the transistor 15b is blocked. Further discussion regarding the triggering or control of the transistor 15a and 15b will not be made herein since it can be carried out in any conventional manner known to the man of ordinary skill in the art. In the embodiment of the circuit shown in FIG. 5, npn transistors are used, however the circuit can be suitably adapted for pnp transistors.

In FIG. 6, there is shown in longitudinal section, the actual structure of the electromagnetic drive 20 of the invention which has been shown diagrammatically in FIGS. 1 to 3. An excitation coil 21 is mounted on a cylindrical coil form 22 which is carried by two flanges 23 and 24 having, respectively, a sleeve-like extension 26, 25. The sleeve-like extensions 25 and 26 are inserted into the coil form 22 so that two opposing magnet poles 25a and 26a are formed, having pole ends of conical construction at the outside thereof. A plunger 27, as aforedescribed with respect to FIGS. 1 to 3, is polarized in longitudinal direction thereof and is of tubular construction. Guide flanges 28 and 29 are constructed with the end faces of the polarized plunger 27. They are made of non-magnetic material and are formed with recesses 30 and 31 extending in the direction of displacement of the plunger 27, for reducing the mass of the flanges 28 and 29. The plunger 27 is freely displaceably disposed within the sleeve-like extensions 25 and 26 of the respective flanges 23 and 24. As location-securing device for the plunger 27 in the neutral position thereof, a stop 32 formed with an air hole 33 is provided. The stop 32 is threadedly disposed in the sleeve-like extension 25, and is adjustable therein by means of the threaded connection 34 so that a cylindrical extension 35 of the stop 32 abuts the guide flange 29 of the plunger 27. Due to these measures, the force of impact for the indicating means 38, directly actuated by the plunger 27 and constructed as a printing wire, is capable of being adjusted. Similarly, the neutral position of the plunger 27 is also capable of adjustment. For the purpose of securing the electromagnetic drive 20 of the invention in a non-illustrated carrier part, the flange 23 facing in direction toward the location at which the non-illustrated indication carrier would otherwise be, is provided with a connecting piece 36 formed with a thread 37. The outer magnetic return leg of the magnet system is formed by a sleeve 39 that is slid over the excitation coil 21 and is connected, for example, to both flanges 23 and 24 respectively having the extensions 26 and 25, and provides a shell core-like shape to the magnet core constructed of these components. As described hereinbefore, the sleeve 39 forming the outer leg of the magnetic circuit is located between the two flanges 23 and 24. A close magnetic force lock can be produced by rolling and flanging the outer magnetic return leg, so that the sleeve 39 surrounds both flanges 23 and 24.

In the illustrated embodiment of FIG. 6, the indicating means 38 is constructed as a printing wire, so that when a number of these electromagnetic drives 20 are combined into one unit, there results, for example, a complete wire printing mechanism.

The structure of the indicating means 38 can obviously also be needle or hammer-shaped so that the aforedescribed embodiment of the electromagnetic drive 20 is capable of being used as well for conventional needle printers or fast printers.

The advantages attained by the invention are especially that, due to the very small mass being displaced, a high indicating speed is attained, and this indicating speed, because no increasing counter-force, such as for a spring, need be overcome, is very rapidly achieved.

Claims

I claim:

1. Electromagnetic drive for data indication comprising a shell core-like magnetic core, an excitation coil surrounding said magnet core, said magnet core having an inner sleeve-shaped core portion extending through said excitation coil, said inner core portion being formed with an air gap separating said inner core portion into two parts each formed with a magnetic pole, indicating means, and a plunger polarized in longitudinal direction thereof operatively connected to said indicating means, said plunger being freely displaceably disposed within said sleeve-shaped inner core portion and being displaceable from a neutral position thereof to a position wherein said indicating means are effective to provide an indication.

2. Electromagnetic drive according to claim 1 wherein said sleeve-shaped inner core portion has a length that is a multiple of the length of said plunger, and said air gap is located in the center of said coil.

3. Electromagnetic drive according to claim 1 wherein said plunger, in neutral position thereof, is at least partly surrounded by one of said magnetic poles and, in said position thereof wherein said indicating means are effective, is surrounded by both of said magnetic poles.

4. Electromagnetic drive according to claim 3 wherein the magnetic poles of said magnet core are polarizable, in one indicating operation, so that transfer of said plunger into both the positions thereof wherein said indicating means are effective, as well as into said neutral position thereof, is accelerated.

5. Electromagnetic drive according to claim 4 including means for producing an outer magnetic field in given direction in said plunger and means for producing with said excitation coil a magnetic field in direction opposite to said given direction for transferring said plunger from neutral position thereof to the position thereof wherein said indicating means are effective, and for producing a magnetic field in the same direction as said given direction for transferring said plunger from the position thereof wherein said indicating means effective to said neutral position thereof.

6. Electromagnetic drive according to claim 1 including adjustable stop means disposed in one of said sleeve-shaped core positions for adjusting the neutral position of said plunger.

7. Electromagnetic drive according to claim 6 wherein said stop means is formed with an air hole.

8. Electromagnetic drive according to claim 6 wherein said stop means is formed of a sound-proofing, elastic plastic material.

9. Electromagnetic drive according to claim 1 wherein said plunger comprises a member of tubular construction and a pair of guide flanges located respectively at opposite ends of said member, one of said guide flanges facing in direction toward said position of said plunger wherein said indicating means are effective, said one guide flange being connected to said indicating means.

10. Electromagnetic drive according to claim 9 wherein said indicating means has a wire-shaped construction.