US3296601A

US3296601A - Transmitting characteristic for multiaperture cores

Info

Publication number: US3296601A
Application number: US185727A
Authority: US
Inventors: William B Fritz
Original assignee: AMP Inc
Current assignee: TE Connectivity Corp
Priority date: 1959-10-30
Filing date: 1962-04-06
Publication date: 1967-01-03
Anticipated expiration: 1984-01-03
Also published as: GB896657A; CH390322A; FR1285922A; US3163854A; DE1287635B; CH481451A; BE630484A; DE1258895B; NL257406A; US3375505A; BE596500A; GB959012A; NL129774C; NL291108A

Description

Jan. 3, 1967 w. B. FRITZ 3,296,601

TRANSMITTING CHARACTERISTIC FOR MULTIAPERTURE CORES Filed April 6. 1962 HIMIIIIMIII! l T T i PRH E.

INVENTOR. Wuuam B. FRrTz M Wfl-W United States Patent 3,296,601 TRANSMITTING CHARACTERISTIC FOR MULTIAPERTURE CORES William B. Fritz, Linglestown, Pa., assignor to AMP Incorporated, Harrisburg, Pa.

Filed Apr. 6, 1962, Ser. No. 185,727 8 Claims. (Cl. 340174) The present invention relates to multi-aperture magnetic core devices including means and method for improving core transmitting characteristics.

With developments of multi-aperture cores for use in memory and logic circuits have come numerous manufacturing problems. One of the more important problems has been the identification of cores which result in unsatisfactory magnetic device performance due to poor transmitting characteristics. Strict control of manufacturing technique with attention to core material has not heretofore eliminated the difiiculties and many core devices such as shift registers have been assembled with apparently satisfactory cores, only to find malfunction at some point of operation far short of the operating parameters demanded by civilian and military specifications. The result of this is that the general cost of core devices must support a substantial rejection rate, or alternatively, additional cores and windings must be employed to accomplish flux clipping with the additional cost of labor and material incident to such practice.

Accordingly, it is one object of the present invention to provide a method by which cores having ideal transmitting characteristics may be obtained.

It is a further object of invention to provide an improved magnetic core geometry.

It is another object of invention to provide an improved magnetic core device capable of superior performance over a substantial range of current and temperature.

It is still another object of invention to provide a mag netic core device which avoids the need of intra-core flux clipping.

Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings in which there is shown and described an illustrative embodiment of the invention; it is to be understood, however, that this embodiment is not intended to be exhaustive nor limiting of the invention but is given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

In the drawings:

FIGURE 1 is an enlarged view of a multi-aperture magnetic core included to further explanation of the invention;

FIGURE 2 is a similar view of a magnetic core modified in accordance with one embodiment of the invention;

FIGURE 2A is an elevation of the core of FIGURE 2;

FIGURE 3 is a similar view of a core modified in accordance with a second embodiment of the invention; and

FIGURE 4 is a schematic diagram of a shift register circuit employing multi-aperture cores modified in accordance with the embodiment of FIGURE 3.

For a general description and definition of the material and energy requirements of magnetic devices reference may be had to the papers MAD-Resistance Type Magnetic Shift Registers and Analysisof MAD-R Shift Registers and Devices by Dr. D. R. Bennion and Dr. David Nitzan respectively, 1960 Proceedings-Special Technical Conference on Nonlinear Magnetic and Magnetic Amplifiers, Philadelphia, October 26-28, 1960, pp. 96 133, published by the A.I.E.E.

In US. Patent No. 2,995,731 to J. P. Sweeney there is shown a shift register comprised of multi-aperture ferrite cores linked by windings and supplied by driving pulses in a manner to controllably shift intelligence in the form of large and small pulses representative of one-zero binary code. The manufacture of devices of this type presently requires that the cores employed be subjected to tests which measure core threshold and flux content and to a limited visual inspection. Notwithstanding such tests and notwithstanding an apparent compliance with other core specifications, problems have been encountered wherein shift registers lose or gain information. Generally, shift registers which cannot transfer intelligence without significant alteration throughout a range in temperature of between 50 C. and C. are not suitable for military and certain commercial applications. A study of rejected shift registers has revealed that in each case at least certain of the cores employed showed an excessive output voltage from the transmitting aperture responsive to clearing or advance current when the core was in a cleared state. Further tests have confirmed that shift registers composed of cores having a low voltage output operate properly through an acceptable range of temperature and current variations.

The result of the foregoing has been the development of the invention which, as will be shown, calls for a core geometry substantially different from that urged by the prior art.

Referring now to FIGURE 1, a core 20 is shown, having a plurality of minor apertures 24 disposed about a central major aperture 22 and including an input winding 21, an output winding 28 and a winding 26 which may be considered as a clearing winding, similar in function to the advance winding employed in Patent No. 2,995,731. Cores of this type are comprised of die formed ferrite magnetic material having bistable properties characterized by a hysteresis curve substantially but not exactly rectangular. In accordance with the accepted convention, the core 20 may be considered as representing a zero when in its clear or negative remanent state of saturation and as representing a one when in its set state with the core inner leg in the positive remanent state of saturation.

Such states are accomplished by the application of relatively small or relatively large input pulses applied to an input winding such as winding 21 which in the case of a zero input produces an insuflicient to alter the remanent state of the core and in the case of a one input produces an greater than the coercive force thereby reversing the sense of flux of the core inner leg. The application of a prime current to a winding (not shown in FIGURE 1) threading the transmitting aperture assures that the core, when set, will assume a flux configuration encircling the output winding. Intelligence transfer or interrogation is accomplished thereafter by the application of a clearing pulse on winding 26 having a magnetomotive force in a sense to drive the core in the direction of negative saturation, producing a substantial flux change if the core is set and, in theory, only an elastic flux change if the core is clear. The output E on winding 28, is therefore proportional to the amount of flux switched each time the core is cleared. With the winding as shown in FIGURE 1, this flux will be the total switchable flux in the outer leg L4 and assuming a constant cross section, will be elastic flux. However, if the cross sectional area at the section C is not the smallest cross section of the core, the flux in leg L4 will include remanent flux in addition to elastic flux. The effect of the additional flux is that the output E, from a cleared core is larger than desirable and such output may either appear to be a one or will cause the phenomenon of zero build-up. Evidence shows that a shift register of the type shown in FIGURE 4, including cores having excess material at the transmitting aperture, will produce an erroneous one within several advance cycles.

The foregoing problems cannot be solved by exact die specifications requiring equal cross sectional area because of the existence of manufacturing tolerances. It will be readily appreciated that even in the simplest multi-a-perture core geometry there will always exist an area which is the smallest cross sectional area of a core. It will be further appreciated that it is practically and economically impossible to detect which particular combination of core dimensions produces the smallest cross sectional area in each of the cores within a given core geometry.

The solution of the foregoing problems as contemplated by the invention involves a controlled constriction of the cross sectional area of multi-aperture cores whereby the transmitting aperture is made to have a reduced cross sectional area. This may be accomplished in existing cores by removing core material from the L4 leg at the aperture selected to be the transmitting aperture. New cores may be manufactured wherein the core die produces a similar reduced cross sectional area at one of the minor apertures selected to be the transmitting aperture of the core. In either event, the reduction may be accomplished in a number of ways, including the removal of core material from any surface about the outer or L4 leg of the selected minor aperture. This practice has the effect of automatically assuring that the cross sectional area of the core is smallest at the transmitting aperture and therefore the remanent flux is substantially zero and the total switchable flux at that point includes only an elastic component thus making the zero output of a cleared core as small as possible for a given core material.

The core geometry shown in FIGURE 1 is typical of a number of core geometries manufactured under specifications calling for major and minor aperture dimensions and core material thickness and width dimensions with each dimension including a plus or minus tolerance which may be considered for the purpose of discussion as :X mils. Taking this core as an example, it is first necessary to establish the general dimensions of the magnetic core material widths W and W/Z as shown in FIGURE 2. The dimension T may be expected to vary from core to core within a given core geometry by :X mils but due to the flatness or parallelism of the upper and lower surfaces may be carried Within a given core with a consistency far greater than other dimensions. For this reason for all practical purposes alteration of the W or W/2 dimensions will assure that a selected cross sectional area may be made less than any other cross sectional area in the core. It is to be understood however, that while this is preferred, reduction of the cross sectional area could also be accomplished by reducing the T dimension.

When dealing with modification to existing cores of a given core geometry the W and W/2 measurements may be made on a relatively small number of cores and a determination of the amount of core material to be removed from the core may be accomplished and thereafter applied without further measurements to all of the cores of that core geometry. Considering the core of FIGURE 2, one aperture, such as aperture 36, may be selected as the transmitting aperture of the core. Considering the design tolerance of the core to be iX mils, the removal of a portion of magnetic material, as indicated at 38, to the extent of twice the permissible tolerance (2X mils J will assure that the cross sectional area through the section DD is not larger than any other cross sectional area through the core body or through other minor apertures of the core. This will in turn assure that the switchable flux about the aperture 38 will not contain a significant remanen-t component and will therefore produce a low output voltage responsive to advance or clearing pulses applied to the core when in its cleared state as heretofore described. In the same manner, a reduction of the leg L4 by three times the tolerance (3X mils) will absolutely assure a minimum cross sectional area at the selected transmitting aperture 36. In core geometries wherein the core material widths W are relatively small, it is preferred to remove only 2X mils from the leg L4 to avoid any possibility of adversely affecting the core threshold. In most applications wherein the core material widths W are relatively large, a reduction by 3X mils is acceptable. It should be kept in mind, however, that the theoretically preferred Width dimension of a transmitting aperture should be equal to all other similar dimensions and that the invention contemplates making the dimension as close to equal as possible but in any event not larger than any other cross sectional Width.

Removal of core material may be accomplished in any desired manner as by filing, sanding or other abrasive techniques. The removal, as indicated by the slot 38 as shown in FIGURE 2 and 2A, may also be accomplished on the top or bottom surfaces of the core or-may be accomplished by enlarging or removing material from the L4 portion of the aperture selected to be the transmitting aperture. Following removal of core material the constricted aperture may be marked for identification as an aid in assembly of magnetic devices using altered cores.

The :foregoing technique of selecting an aperture and removing material from the leg L4 thereof may also be applied to core dies so that cores may be manufactured having a constricted cross sectional area at a selected minor aperture. The preferred way of accomplishing cross sectional area constriction in new cores is by enlarging the diameter of the minor aperture chosen to be the transmitting aperture. In FIGURE 3, the aperture 34 is enlarged by an amount sufficient to assure the cross sectional width along the section E--E is as small as any cross section in the core. For example, assuming that the die specifications normally require that the apertures A1, A2, A3 and 34 to be equal to 30 mils with a tolerance of 1-1 mil, a new die made in accordance with the invention would include apertures A1, A2 and A3 of 30 mils with aperture 34 being 32 milsimil. In this manner, and variation of one mil in any of the apertures A1, A2 or A3 and 34 will leave the aperture 34 at least as large and the cross sectional area thereat least as small as any remaining cross section of the core. Care must be exercised to assure that the reduction of magnetic material does not reduce the core material linked by the output winding to a point wherein an insuflicient flux will be present in the leg L4 to provide proper gain. By basing the amount of constriction on the manufacturing tolerance of core this may be avoided.

In FIGURE 4, there is shown a shift register circuit of a well known type, wherein odd, 0 and even E" cores are arranged to be driven by pulses applied to ad- Vance windings 48 and 52 and by prime current via winding 58. Each of the cores OE include a major aperture 45 and a plurality of minor apertures 46, as in the cores above described. Intelligence is fed into the register by pulses applied to the input Winding 44 and is transmitted from core to core by advance pulses alternately applied to windings 48 and 52. The constant application of prime current via winding 58 assures that if a core is in its set state the core magnetization will be properly altered to assure coupling of the windings 43 prior to the application of advance current. It is of transcending importance that the intelligence shifted into a register not be lost during successive advance cycles and, moreover, that false intelligence due to zero build-up not occur. In accordance with the invention, each of the O and E cores of the register include transmitting apertures, such as 42, which are enlarged relative to the other minor apertures of the core as heretofore described so as to insure that the cross sectional area of core material at such transmitting aperture is equal to or smaller than any other cross sectional area of the core. In this manner, the application of advance current to a core in its cleared state will not produce output voltages on coupling windings 43 of a value sufficient to either set a succeeding core or to cause the additive effect of zero build-up whereby a false one will be produced at the output winding 49. Loss of ones will be avoided by assuring that the diameter of the transmitting aperture 42 is limited to a deviation of no more than several tolerances of the remaining apertures.

The shift register of FIGURE 4 is exemplary of magnetic devices of the type wherein the present invention can be used to substantial advantage. In any magnetic device having one or more multi-aperture cores coupled to an additional core or cores by coupling windings similar to the winding 43, as shown in FIGURE 4, the output voltage responsive to driving a cleared core may be minimized by the application of the invention.

In a core of the configuration of FIGURE 2 comprised of a magnetic ferrite material uanufactured by the General Ceramics Company of Keasbey, New Jersey and identified as No. 5209 material, the following was observed. The core included dimensions of T :39 mils, W=40 mils, and W/2=20 mils, :1 mil. Removal of approximately 3 mils from the leg L4, as indicated by 38 in FIGURE 2, reduced the output voltage E of the core in its cleared state from 230 millivolts to 60 millivolts.

In a shift register of the type shown in FIGURE 4, the use of cores having 5% reduction of the L4 dimension of the transmitting aperture produced a range of satisfactory operation as measured by advance current vs. prime current improved by 25 percent.

Changes in construction will occur to those skilled in the art and various apparently diiferent modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective against the prior art.

I claim:

1. The method of improving the transmitting characteristics of magnetic cores of the type having a major aperture and a plurality of minor apertures defining inner and outer legs of magnetic material including the steps of ascertaining the cross sectional area of the core body as measured from the said major aperture to the outer pen'phery of the core to a given tolerance, selecting one of said minor apertures as a transmitting aperture, reducing the cross sectional area of the said core by removing magnetic material from the outer leg of the selected aperture to an extent of twice the tolerance as ascerained whereby the cross sectional area of the core through the selected aperture is equal to or less than other cross sectional areas of the core.

2. In a method of improving the binary one and zero transmitting characteristics of magnetic cores of the type having a major aperture and a plurality of minor apertures defining inner and outer legs of magnetic material including the steps of ascertaining the manufacturing 6 v tolerance of the cross-sectional area of material of the core body, as measured from the major aperture to the periphery of the core, selecting one minor aperture as a transmitter aperture for said core, dimensioning the core so that the said cross-sectional area of material at points about said major aperture in the absence of a minor aperture and the sum of cross-sectional .areas of the inner and outer legs of the minor apertures other than at the said one minor aperture are approximately equal, dimensioning the inner and outer legs of material at said one minor transmitter aperture so that the sum of cross-sectional areas of material of said legs is equal to the said cross-sectional area at other points about said major aperture less an amount equal to twice the said tolerance as ascertained.

3. The method of claim 2 including the step of marking the said one selected minor aperture selected as a transmitter aperture for said core for identification as an aid in assembly of magnetic devices using said core.

4. In a method of improving the binary one and zero transmitting characteristics of magnetic cores of the type having a major aperture and a plurality of minor apertures defining inner and outer legs of magnetic material including the steps of ascertaining the manufacturing tolerance of the cross-sectional area of material of the core body, as measured from the major aperture to the periphery of the core, selecting one minor aperture as a transmitter aperture for said core, dimensioning the core so that the said cross-sectional area of material at points about said major aperture in the absence of a minor aperture and the sum of cross-sectional areas of the inner and outer legs of the minor apertures other than at the said one minor aperture are approximately equal, dimensioning the inner and outer legs of material at said one minor transmitter aperture so that the sum of crosssectional areas of material of said legs is equal to the said cross-sectional area at other points about said major aperture less an amount equal to three times the said tolerance as ascertained.

5. The method of claim 4 including the step of marking the said one selected minor aperture selected as a transmitter aperture for said :core identification as an aid in assembly of magnetic devices using said core.

6. In a device for transferring binary one and zero information a circuit including a plurality of multiaperture cores formed of magnetic material having square loop characteristics, input means to supply said cores with information signals, output means driven by said cores to output information and coupling means coupling said cores for transferring information therebetween, drive means linking said cores to switch flux therein to effect transfer of information, each said core including a major aperture and a plurality of minor apertures positioned in said body to define inner and outer legs of material at each minor aperture, the sum of cross-sectional areas of material of said inner and outer legs of material at one of said minor apertures being less than the sum of crosssectional areas of material of the inner and outer legs of material at all of the other said minor apertures and the sum of said cross-sectional area of said inner and outer 'legs of material at said other minor apertures being approximately equal to or greater than the cross-sectional area of the square loop material surrounding the said major aperture at points apart from said minor apertures, the said one minor aperture having the least cross-sectional area of magnetic material being the transmitter aperture for the said core whereby to minimize zero level transfer from each of said cores.

7. The device of claim 6 wherein the said coupling loops link the transmitter aperture of a given core to one of the other said minor apertures of an adjacent core whereby to minimize zero level transmitted from a given core and to further minimize zero level input to the adjacent core.

8. The device of claim 6 wherein the said drive means 7 includes a first drive Winding threading said cores to switch flux about said major apertures and a second drive winding threading the core transmitter apertures to switch flux locally thereabout to prime said cores for transfer.

References Cited by the Examiner UNITED STATES PATENTS 2,799,822 7/1957 Dewitz 340-174 2,907,991 10/1959 Van Allen 340174 8 Briggs 340-174 Kelley 340-174 Bullock 340174 Richard 340174 Mathers 340'174 Bennion 340-174 BERNARD KONICK, Primary Examiner. IRVING SRAGOW, Examiner. M. S. GI'ITES, R. J. MCCLOSKEY, Assistant Examiners.

Claims

2. IN A METHOD OF IMPROVING THE BINARY ONE AND ZERO TRANSMITTING CHARACTERISTICS OF MAGNETIC CORES OF THE TYPE HAVING A MAJOR APERTURE AND A PLURALITY OF MINOR APERTURES DEFINING INNER AND OUTER LEGS OF MAGNETIC MATERIAL INCLUDING THE STEPS OF ASCERTAINING THE MANUFACTURING TOLERANCE OF THE CROSS-SECTIONAL AREA OF MATERIAL OF THE CORE BODY, AS MEASURED FROM THE MAJOR APERTURE TO THE PERIPHERY OF THE CORE, SELECTING ONE MINOR APERTURE AS A TRANSMITTER APERTURE FOR SAID CORE, DIMENSIONING THE CORE SO THAT THE SAID CROSS-SECTIONAL AREA OF MATERIAL AT POINTS ABOUT SAID MAJOR APERTURE IN THE ABSENCE OF A MINOR APERTURE AND THE SUM OF CROSS-SECTIONAL AREAS OF THE INNER AND OUTER LEGS OF THE MINOR APERTURES OTHER THAN AT THE SAID ONE MINOR APERTURE ARE APPROXIMATELY EQUAL, DIMENSIONING THE INNER AND OUTER LEGS OF MATERIAL AT SAID ONE MINOR TRANSMITTER APERTURE SO THAT THE SUM OF CROSS-SECTIONAL AREAS OF MATERIAL OF SAID LEGS IS EQUAL TO THE SAID CROSS-SECTIONAL AREA AT OTHER POINTS ABOUT SAID MAJOR APERTURE LESS AN AMOUNT EQUAL TO TWICE THE SAID TOLERANCE AS ASCERTAINED.