US 3488647 A
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Description (OCR text may contain errors)
1970 v P. E. STUCKERT- 3,488,67
MAGNETIC CORE SWITCHING CIRC UIT Filed JI me e, 1958 OUTPUTS I EFFECTIVE AIR GAP H DUE T0 SATURATION FIELD 22'- ms mm INPUT y INVENTOR. PAUL E. STUCKERT United States Patent 3,488,647 MAGNETIC CORE SWITCHING CIRCUIT Paul E. Stuckert, Katonah, N.Y., assignor to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed June 6, 1958, Ser. No. 740,327 Int. Cl. Gllb 5/00; H01f 21/06 US. Cl. 340--174 2 Claims This invention relates to switching and control circuits employing magnetic cores and more particularly, to the control of signal transmission paths by controlling the degree of coupling between said paths.
In pulse circuits where logical and control operations are performed by magnetic cores or other low impedance elements, it is frequently desirable to change pulse paths which transmit pulses between one or more circuit points. Such changes have been made, for example, by employing conventional manually operated electrical switches or plug wires in a plugboard arrangement. However, manual switches, plug wires and the like, which physically interrupt the circuit, introduce contact resistance which interferes with the proper operation of associated low impedance circuitry. Further, such switches and plug wires involve mechanically moving parts which decrease the reliability of the system.
According to the present invention, the transmission of a pulse between two circuit points is controlled by one or more magnetic cores each having input, output and bias means. The bias means normally biases the core in one of two states of saturation. The application of an input signal to the input means overcomes the bias and drives the core towards the opposite state of saturation thereby creating an output signal in the output means. Upon the cessation of the input signal, the core returns to the biased condition. Associated with each core are facilities for selectively applying to or removing from the core, a saturating field of sufiicient magnitude to prohibit the core from being switched by the application of an input MMF. The saturating field may be provided by a permanent magnet which is placed in the vicinity of the core when it is desired that the core be prohibited from switching or alternatively may be removed so that the core may be switched in response to an input signal. Hence, a signal transmission path is established between the input and output means of a core when the saturating field is not applied thereto, and the pulse transmission path may be interrupted by applying the saturating field to the core.
The invention also provides a matrix of cores arranged in columns and rows which control the transmission of signals between a plurality of input and output terminals. Each of the cores is provided with a bias winding which biases the core in a first state of saturation. The input windings of each of the cores of a predetermined row are connected to an input terminal corresponding to the row. The output winding of each of the cores of a predetermined column are connected to a corresponding output terminal. Mounted adjacent each of the cores of the matrix is structure for supporting a permanent magnet which provides, as a function of position, a field that saturates the core. When the transmission of a pulse between a predetermined input winding and a predetermined output winding is to be inhibited, a permanent magnet is inserted in the support so that the magnet is adjacent the magnetic core. The magnet applies a saturating field to the core which prohibits the material from being switched from one state of saturation to the opposite such state. By selectively positioning the permanent magnets adjacent to selected cores, the transmission of input pulses to predetermined output terminals is controlled.
Accordingly, the principal object of the invention is Patented Jan. 6, 1970 ICC to provide a novel switching arrangement wherein the transmission of pulses between predetermined circuit points is controlled by controlling the degree of magnetic coupling between said points.
Another object is to provide a novel magnetic plugboard arrangement wherein the transmission of a pulse between predetermined points may be selectively interrupted without physically interrupting the circuit by providing means for applying a saturating field to a magnetic core which couples said points.
An additional object is to provide a novel switching matrix having a plurality of input terminals which are respectively coupled to one or more output terminals by magnetic cores and including provision of permanent magnets which may be placed adjacent certain cores in order to inhibit the transmission of pulses by means of said certain cores.
It is also an object to provide a novel switching circuit comprising a magnetic core having input and output means and a biasing means for saturating the core in a first direction whereby the application of a signal to the input means drives the core to the opposite state of saturation to create a signal in said output means and including the provision of means for selectively applying a saturating field to the core to thereby inhibit a transmission of a pulse between said input and output means.
Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.
In the drawings:
FIG. 1A illustrates the novel switching device;
FIG. 1B illustrates the effective air gap produced in the core by a localized saturating field;
FIG. 2 is a graph of the hysteresis curve of the switching device; and
FIG. 3 illustrates a novel switching arrangement employing the invention.
Referring to FIG. 1A, the novel switching circuit includes a magnetic core 10 having an input winding 11, an output winding 12 and a bias winding 13. The core may be constructed of any magnetic material. The core material must be capable of being driven into two opposite states of saturation and thus may exhibit a hysteresis curve of the type shown in FIG. 2. From the following description, it will be evident that material exhibiting a hysteresis curve of the type shown in FIG. 2 is satisfactory when utilized in the invention and need not necessarily be of the square looped or rectangularly shaped hysteresis curves normally desirable in memory type core circuits.
A permanent magnet 16 of FIG. 1A is provided adjacent each core and is Supported by a structure 17. The supporting structure 17 is provided with a hole 18 which permits the insertion or withdrawal of the magnet in the hole as indicated by the arrow 19. When the magnet 16 is placed in the hole 18 so as to be adjacent to the core 10 at point 20, a saturating field represented by arrows 21 is created within the core 10. The elfect of the saturating field produced by magnet 16 is illustrated in FIG. 1B by the effective air gap 22 which serves to decrease the coupling between the input and output winding on the core.
While the illustrations of FIGS. 1A and 1B show a localized field 21 which saturates only a portion of core 10, it is to be understood that the same effect is produced when a saturating magnetic field is employed which sat urates a greater portion or all of the core material. It is immaterial whether the saturating field is applied in a direction perpendicular or parallel to the mean path of magnetic cores. Thus, it is immaterial where the source of the saturating field is placed relative to the core as long at the field saturates at least a portion of the core.
The polarity of the individual windings associated with a magnetic core is indicated by the dot adjacent one end of the core. It is assumed that current applied to the end of the winding adjacent the dot and in the direction towards the dot, produces a MMF which drives the material of the core towards the positive remanent state. With respect to the sense or output Winding of the core, it is assumed that when the core is driven from the negative remanent state towards the positive remanent state, a voltage is induced in the sense winding having a polarity which is positive at the end of the winding adjacent the dot.
In order to facilitate the description of the operation of the switching device of FIG. 1A, assume first that the magnet 16 is completely withdrawn from hole 18. Under this condition, the saturating field is not present in the core material. A bias current I is applied to the bias winding 13 of FIG. 1A in the direction indicated by the arrow on the winding. The MMF produced by the bias current drives the core material into saturation as indicated by point 23 of FIG. 2. While the bias current may be continuously applied to the bias winding it is only necessary that the current be applied thereto during any time intervals in which an input pulse may be applied to input winding 11.
The application of an input current pulse in the direction shown by the arrow on winding 11 of FIG. 1A, produces a MMF in a direction opposite to the direction of the bias MMF. The MMF produced by the input pulse current overcomes the bias MMF and drives the core material to the opposite state of saturation as indicated by point 25 of FIG. 2. The switching of the core from point 23 of FIG. 2 to point 25 induces an output voltage signal in the output winding 12 of FIG. 1A. Upon the cessation of the input signal, the core material is driven back to point 23 by the bias MMF of FIG. 2 thereby inducing an output signal of opposite polarity (with respect to the first output signal) in output winding 12. The polarity of the output signal utilized normally depends on the auxiliary circuitry which is connected to the output winding.
Thus it is seen that the core is normally biased in a first state of saturation. When the magnet 16 is not adjacent to the core, the application of an input signal to the core switches the core to the opposite saturation state. After the termination of the input signal, the core is switched back to the first state of saturation by the bias MMF. An output signal is produced when the core is switched from one state to the opposite state of saturation.
Now assume that the permanent magnet 16 of FIG. 1A is inserted in hole 18 and thus is maintained adjacent to the core at point 20. As stated hereinabove, the magnet 16 produces a field 21 which saturates the core. The magnitude of the saturating field 21 is many times greater than the field produced by either an input current or the bias current so that the effect of the saturating field is to substantially eliminate magnetic coupling due to core material between the input and output windings on the core. The saturating field produced by magnet 16 sufirciently saturates the magnetic core so that the MMF produced by the input current is insufficient to switch the core in the manner indicated hereinbefore. Since the input current does not produce a MMF sufficient to switch the core, an output signal will not be induced in the output winding 12.
Thus it is now evident that when the permanent magnet 16 is placed in hole 18, the core cannot be switched by the MMF produced by the input current and thus an output signal is not induced in the output winding. Conversely, when the magnet 16 is removed from the hole 18, the core is switched in response to an input current and each switching of the core produces an output signal.
While the graph of FIG. 2 illustrates a hysteresis curve having considerable area within the loop, it is to be understood that the invention may be constructed from magnetic material having practically no area within the loop, as for example in the case of various commercially available grades of transformer iron.
With respect to the circuit of FIG. 1A, it was stated herinabove that the core is normally biased in one direction (see point 23 of FIG. 2). However, the requirement of the bias MMF can be eliminated by employing pulses which constitute bursts of alternating current, as for example, pulses of radio frequency energy. In this case, the core acts as a transformer only when the saturating field is removed from the vicinity of the core.
Referring to FIG. 3, a switching matrix embodying the principle of the invention is illustrated. The matrix includes a plurality of cores arranged in columns and rows wherein the input windings of each row of cores are commonly connected and the output windings of each column of cores are commonly connected.
In FIG. 3, the input windings 11 of each of the cores 31-34 of the first row are connected in series between ground 70 and input terminal 71. Similarly, the input windings of cores 41-44 of the second row are connected in series between ground and input terminal 72; the input windings of cores 51-54 of the third row are serially connected between input terminal 73 and ground; and, the input windings of cores 61-64 of the fourth row are serially connected between the input terminal 74 and ground.
The output windings 12 of each of the cores 31, 41, 51 and 61 of the left-hand column are connected in series between ground 70 and output terminal 81. In a similar manner, output windings of the cores of each of the remaining columns are serially connected between ground and the output terminals 82, 83 and 84 which correspond to the respective columns. The bias windings 13 of all of the cores of the matrix are connected in series between terminal and ground. The bias current I is applied to terminal 90 in the direction indicated by the arrow adjacent thereto.
Each of the magnetic cores of FIG. 3 is provided with a magnet similar to magnet 16 associated with core 31. As explained hereinbefore, each of these magnets may be placed adjacent a core or may be removed from the vicinity thereof. It was also explained hereinbefore that mechanical structure for positioning the magnets adjacent the cores must be provided. For example, the cores can be mounted adjacent a flat sheetlike board having a hole similar to hole 18 adjacent each of the cores. A hole 18 is provided for each core so as to accommodate the individual magnets. Other methods of mounting the magnets may be employed by one skilled in the art without departing from the scope of the invention.
Briefly, circuitry supplying one or more input signals are connected to the input terminals 71-74. Auxiliary circuitry which perform functions in response to output signals is connected to the output terminals 81-84. By operating the device of FIG. 3 in the manner described hereinbelow, input signals applied to one or more of the input terminals 71-74 may be transmitted to one or more of the output terminals 81-84.
Assume for example, that an input signal represented by current I is applied to input terminal 73 and it is desired that output signals be manifested at output terminals 81 and 83. Accordingly, the permanent magnets, similar to magnet 16, associated with cores 51 and 53 are each removed from the vicinity of these cores. Upon the application of the input current pulse I to terminal 73, cores 51 and 53 are each switched to the opposite state of saturation. Hence, output signals are induced in each of the output windings 12 of cores 51 and 53. These output signals are manifested at terminals 81 and 83. Since the permanent magnets associated with cores 52 and 54 of the third row are shown adjacent these cores, the input current pulse I does not switch the cores 52 and 54. Thus output signals are not manifested at output terminals 82 and 8-4 as a result of the input current pulse I While the operation of the switching matrix of FIG. 3 is described assuming that the magnets associated with cores 51 and 53 have been removed, it is evident that by selectively removing or inserting other magnets associated with predetermined cores, one or more input current pulses can be transmitted through the switching matrix to predetermined output terminals. In this manner, a magnetic plugboard which functions similarly to the well-known wired type of plugboards employing individual plug wires is provided which is compatible with other magnetic core circuits. The switching matrix of FIG. 3 is compatible with other core circuits in that the input and output impedances are similar to those encountered in core and transistor circuits and are not affected by such difiiculties as poor contacts and opencircuited plug wires. Additionally, the switching matrix can be driven directly by logical circuits employing magnetic cores.
While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.
What is claimed is:
1. In combination with a switching matrix of a type comprising, a plurality of magnetic core members arranged in columns and rows each said members made of magnetic material exhibiting opposite stable states of flux remanence and having input output winding means coupled thereto, an input terminal for each said row connected to the input winding means of each said element thereof for switching each element of each row from one stable state to another, and an output terminal for each of said columns connected to the output winding means of each element thereof for manifesting an output signal in response to the switching of any element of said column, and means comprising, a plurality of permanent bar magnets, and a support structure for said bar magnets having apertures therein, said structure located in close proximity to said core members and supporting said bar magnets for selectively positioning one end of given ones of said bar magnets in close proximity to a corresponding one of said members to apply a. transverse field to the core members and inhibit the switching thereof from one magnet state to another.
2. In combination with a switching matrix of a type comprising, a plurality of magnetic core members arranged in columns and rows each said members made of magnetic material exhibiting opposite stable states of flux remanence and having input, output and bias winding means coupled thereto, said bias winding means of each member capable of establishing each said element in a first stable magnetic state, an input terminal for each said row connected to the input winding means of each said member thereof for switching the states of each member of each row, and an output terminal for each of said columns connected to the output winding means of each member thereof for manifesting an output signal in response to the switching of any member of said column, and means comprising, a plurality of permanent bar magnets, a support structure for said bar magnets having apertures therein, said structure located in close proximity to said core members and supporting said bar magnets for selectively positioning one end of given ones of said bar magnets in close proximity to a corresponding one of said members to apply a transverse field to the members and inhibit the switching thereof from one magnetic state to another.
References Cited UNITED STATES PATENTS 2,734,184 2/1956 Rajchman.
2,740,110 3/ 1956 Trimble.
2,741,757 4/1956 Devol et a1. 340174 2,781,503 2/1957 Saunders 340174 2,782,399 2/1957 Rajchman 340-166 2,814,031 11/1957 Davis.
2,818,555 12/1957 Lo 307-88 2,842,755 7/1958 Lamy 307-88 2,846,673 8/ 1958 Gray 340174 2,905,834 9/ 1959 Arsenault et al. 30788 JAMES W. MOFFlTT, Primary Examiner N. C. READ, Assistant Examiner U.S. Cl. X.R. 336--1 30