US3526796A - Timing pulse generator - Google Patents

Description

Sept. 1, 1970 F. H. BLITCHINGTON, JR. ETAL 9 TIMING PULSE GENERATOR Filed Oct. 7, 1968 2 Sheets-Sheet l I|| I I I I /3 '1 I II l 36 f I f v /Z 597 6 0 l4 I l lll F. H HFlRR/S Sept. 1, 1970 F. H. BLITCHINGTON, JR.. ETAL 3,526,796

TIMING PULSE GENERATdR Filed Oct. 7, 1968 2 Sheets-Sheet 2 United States Patent 3,526,796 TIMING PULSE GENERATOR Frank Henning Blitchington, Jr., Greensboro, and Richard Allen Harris, High Point, N.C., assignors to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Continuation-impart of application Ser. No. 540,258,

Apr. 5, 1966. This application Oct. 7, 1968, Ser.

Int. Cl. H02k 17/42 US. Cl. 310-168 6 Claims ABSTRACT OF THE DISCLOSURE A substantially unipolar fast rise time pulse is produced when a discontinuity in a magnetic coating on a non-magnetic base is moved past a magnetic pickup head. A magnetic field established in the coating along the path of movement of the coating is interrupted by the discontinuity to produce a localized field above the surface of the coating to produce the pulse in the magnetic pickup.

CROSS REFERENCE TO RELATED APPLICATIONS This is a continuation-in-part of our copending application Ser. No. 540,258, filed Apr. 5, 1966, now abandoned.

FIELD OF THE INVENTION This invention relates to an apparatus for generating pulses, and in particular, to an apparatus for producing pulses in synchronism with the mechanical movement of a device. In many arts, including the communications and information transmission arts, there is widespread use of timing pulses generated in synchronism with mechanical rotation of various devices. Examples of such devices are signal samplers, information storage systems, automobile ignition systems, etc.

DESCRIPTION OF THE PRIOR ART In the prior art, the production of pulses in synchronism with the rotation of a device is usually accomplished by mechanical operation of a switch by a cam or by wiping a contact on a segmented surface. In many applications, it is difllcult to obtain the desired accuracy of operation. Also, the switch contacts are subject to wear, corrosion and failure.

Several devices have been designed which utilize a change in the inductance of a magnetic circuit by the movement of a magnetic element of the circuit. The change in inductance produces a pulse in a coil associated with the magnetic circuit. The output pulses produced by such devices generally have slow rise times and do not have the accuracy required in many applications.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is a new and improved apparatus for generating pulses.

Another object of this invention is an apparatus producing substantially unipolar fast rise time voltage pulses.

With these and other objects in view, the present invention contemplates a magnetic material, having a discontinuity, on a non-magnetic base moved past a magnetic pickup and wherein a magnetic field is established in the magnetic material in a direction along its direction of movement to produce a pulse when the discontinuity passes the magnetic pickup. One such device utilizes a magnetic drum wherein slots are formed through a magnetic material coated on the surface of the drum. A circumferential magnetic field is established in the magnetic material by the rotation of the drum adjacent to one pole of a magnet. The field adjacent to the discontinuity pro- 3,526,796 Patented Sept. 1, 1970 duces a substantially unipolar fast rise time pulse when the discontinuity passes the magnetic pickup.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a pulse generating apparatus embodying the principles of the invention.

FIG. 2 is a plan View particularly showing one theory of operation of the apparatus shown in FIG. 1.

FIG. 3 is a representation of the pulse-like voltage output of the magnetic pickup shown in FIGS. 1 and 2.

DETAILED DESCRIPTION Referring first to FIG. 1, there is shown an apparatus for generating pulse-like voltages. The apparatus includes a segmented drum 10, a magnet 11, and a magnetic pickup 12. The drum 10 is rotated in a selected direction, such as that shown by the arrow in FIG. I, by a motor 15 through a shaft 16. The motor 15 may be operated in synchronism with the driving means for cams of a mechanical signal sampler or any other rotating apparatus. The shaft 16 is mounted for rotation at its upper end on an electrically grounded bearing 21.

The segmented drum 10 is comprised of an inner cylinder 19 and segments 20 of a coating or outer cylinder mounted on the inner cylinder 19. The inner cylinder 19 is made of a non-magnetic material such as brass, aluminum, plastic, etc. The outer cylinder segments 20 are made of a ferromagnetic material having a high retentivity. For example, the segments 20 may be formed by machining grooves 22 through a layer of cobalt-nickel alloy, electrolytically plated on a brass cylinder 19. Generally, any magnetic coating which is suitable for use in making magnetic memory drums would be suitable for use in the segments 20 of the pulse generator. The grooves 22 extend parallel to the major axis of the drum 10, and as shown in FIGS. 1 and 2, extend all the way through the magnetic coating to interrupt a circumferential magnetic path through the segments 20. The grooves 22 need not extend all the way through the magnetic coating forming the segments 20 but must be sufliciently through the coating to substantially interrupt the magnetic path which a circumferential magnetic field would occupy in the segments 20. The grooves 22 must be relatively narrow compared to the width of the segments 20.

The magnet 11 may be a permanent bar magnet or an electromagnet with a north pole and a south pole. In the example to be hereinafter described, it is assumed that the north pole of the magnet 11 is positioned adjacent the grooves 22 and the segments 20 of the outer cylinder. The magnet 11 may have many other forms and positions to produce similar results.

The magnetic pickup 12 may be any magnetic pickup head capable of sensing magnetic signals on a magnetic memory drum, magnetic tape, etc. One such pickup device has a horseshoe or an enclosed ferromagnetic core 24 with a gap 24a. A winding 25 on the core 24 is connected to output conductors 26. The gap 24a is positioned adjacent the segments 20 of the outer cylinder. Fluctuations in the magnetic field within the core 24 are produced by changes in the magnetic field applied across the gap 24a to produce output signals on the conductors 26. A diode 13 and an amplifier 14 connect the pickup 12 to a utilization circuit, such as an electronic switch, etc.

The pickup 12 and the magnet 11 are positioned relative to the drum 10 such that a point on the circumference of the rotating drum 10 passes next to both the pickup 12 and the magnet 11. The pickup 12 and the magnet 11 are positioned as close as possible to the drum 10 Without engaging the drum. The circumference of the drum 10 should be accurately formed to maintain uniform spacing between the pickup 12 and the drum l0.

Referring now to FIG. 3, in assuming that the segmented drum is rotated in a clockwise direction (as seen in FIG. 2) and that the north pole of the magnet 11 is positioned adjacent the drum 10, a voltage wave 27 appears on the output conductors 26 of the magnetic pickup 12. The positive portion 28 of the voltage wave 27 has a peak magnitude approximately twenty times greater than the peak magnitude of the negative portion 29. Assuming the time of the initiation of the positive pulse 28 and the terminal of the positive portion 29 to be one cycle, the positive portion 28 occupies approximately of the cycle. Moreover, it has been observed that the area within the positive and negative portions 28 and 29 appear substantially equal in any one cycle.

The quality of the wave form or the sharpness in rise time in the pulse 28 is dependent upon the relative velocity between the pickup 12 and the segmented cylinder 20. At velocities below a predetermined low relative velocity and above a predetermined high relative velocity the magnitude and sharpness of the pulse 28 deteriorates. It is believed that the operating characteristics of the magnetic pickup 12 and the various parameters of the segmented drum 10 control the optimum range of rotational velocities which produce satisfactory pulses 28.

The theory of operation of the present pulse generating apparatus appears to be that the movement of the segments 20 and grooves 22 past the magnet 11 orients and expands the magnetic domains in the segments 20 to establish and maintain a magnetic field in a single rotary direction through the segments. Since the circumferential path for the magnetic flux through the segments 20 is interrupted by the discontinuities or grooves 22, the magnetic flux bulges outward at each of the grooves 22 as shown in FIG. 2. Thus, when a groove 22 moves adjacent to the gap 24a of the pickup 12, the concentration of flux bulging from the narrow groove 22 produces an abrupt increase in magnetic field in the core 24, as shown in FIG. 2, to produce a sharp output pulse 28 on the leads 26. When the groove 22 moves away from the gap 24a, the field in the core 24 collapses and may even reverse to produce the negative portion 29 of the signal 27 on the leads 26. Due to the characteristics of the pickup 12 and its core 24, the collapsing of the magnetic field in the core 24 occurs at a much slower rate than the rate of increase of magnetic field which occurs when the groove 22 is next to the gap 24a. Adjacent the intermediate portions of each segment 20, there will exist a weak magnetic field which has a polarity opposite to the polarity of the field bulging from a groove 22. As shown by the phantom representation of a core 24' and a gap 24a in FIG. 2, this weak field may produce a weak field in the core 24 which has a polarity opposite to the polarity of the field produced in the core 24 by the field bulging from a groove 22. The rate of change of flux in the core 24 due to the weak field adjacent the intermediate portions of the segments 20 is much less than the rate of change in flux in the core 24 due to the field bulging from the grooves 22.

While the apparatus described utilizes a segmented magnetic drum, it is believed that other segmented magnetic mediums would be suitable. For example, a flexible tape having closely spaced magnetic segments coated thereon may be moved sequentially past a magnet and a magnetic pickup to produce substantially unipolar fast rise time pulses.

There may be additional magnetic pickups, similar to pickup 12 located in the same circumferential path as the magnet 11 and pickup 12 to produce pulses having the same or dilferent phases relative to the pulses produced by the pickup 12. Also, there may be additional pairs of magnets and pickup heads adjacent the drum 10 or other drums on the shaft 16.

EXAMPLE 1 In a device built in accordance with the above description, the inner cylinder 19 was made of brass and has a radius of .500 inch. A 0.125 inch layer of cobaltnickel alloy was electrodeposited on the circumference of the inner cylinder 19. Eighteen grooves 22 having a width of approximately .031 inch and evenly spaced around the circumference of the drum 10 were cut completely through the cobalt-nickel layer into the inner cylinder 19 to form the segments 20. The north pole of the magnet 11 and the magnetic pickup 12 were positioned adjacent the drum approximately from each other.

When the drum 10 was rotated at 1200 r.p.m., the wave 27 depicted in FIG. 3 was observed on an oscilloscope connected to conductors 26 with 360 pulses per second produced on leads 26. The magnitude of the positive wave portions 28, in addition to bearing a 20 to l'ratio to the negative wave portion magnitudes 29, were observed to exhibit unusually fast rise times. It was'found that at rotational velocities less than 350 r.p.m. or greater than 4000 r.p.m., the 20 to 1 ratio of the positive wave portion 28 to the negative wave portion 29 deteriorated.

Within the 350 to 4000 r.p.m. range, the areas within the positive and negative wave portions 28 and 29 were observed to be approximately equal. Rotation of the drum 10 in the opposite direction reversed the polarity of the Wave portions 28 and 29, depicted in FIG. 3, as did reversal of the polarity of the magnet 11. The diode 13 easily eliminated the low magnitude, negative wave portion 29 so that only the high magnitude fast rise time positive wave portions 28 were applied to the amplifier 14-.

EXAMPLE 2 In a second drum 10, the radius R of the inner cylinder 19 was 1.000 inch and with the thickness of the layer forming the segments 20 remaining at 0.125 inch..Thirtysix grooves were spaced evenly around the drum 10. It was observed that the 20 to 1 ratio of the magnitude of the positive wave portion 28 to the negative wave portion 29 occurred in a range of rotational velocity which was /2 of the critical velocity range of Example 1. That is, the 20 to 1 positive to negative magnitude ratio occurred between the rotational velocity of r.p.m. and 2000 r.p.m.

It is to be understood that the above describedembodiments are simply illustrative of the principles of the invention. Many other embodiments may be devised by those skilled in the art without departing from the scope and spirit of the invention.

What is claimed is:

1. An apparatus for generating fast rise time pulses comprising:

a non-magnetic base;

a plurality of segments of remanently magnetizable material mounted on the base in a spaced relationship;

a magnetic pickup for producing a pulse in response to a change in a magnetic field applied thereto;

means for moving the base relative to the pickup such that the segments move sequentiallyin a path adjacent to the pickup; and

means disposed in spaced relation to the pickup for establishing and maintaining a remanent magnetic field in the segments in a uniform direction parallel to the direction of movement of the base relative to the pickup to produce fast rise time pulses in the magnetic pickup.

2. An apparatus for generating a fast rise'time pulse comprising:

a non-magnetic base having a surface;

a magnetic coating on the surface of the base capable of assuming a state of remanence and having a discontinuity;

means for moving the base such that the magnetic coating on the surface of the base moves in a path past a point;

a magnetic pickup located at the point for sensing changes in the magnetic field adjacent the magnetic coating; and

means disposed in spaced relation to the pickup for establishing a remanent magnetic field in the magnetic coating in a direction along the path of movement to produce a fast rise time pulse in the pickup when the pickup senses the interruption of the magnetic field by the discontinuity. 3. An apparatus for generating fast rise time pulses comprising:

(a) a rotatable magnetic drum having a non-magnetic cylindrical core, a magnetic coating on the core capable of assuming a state of remanence; and a longitudinal slot formed substantially through the magnetic coating to interrup the continuity of a circumferential magnetic path through the magnetic coating; (b) a magnetic pickup head adjacent to the drum; means for rotating the drum relative to the pickup head; and (d) means disposed in spaced relation to the pickup head for establishing a circumferential magnetic field in the magnetic coating such that a pulse having a fast rise time is produced by the pickup head When the slot passes the pickup head. 4. An apparatus for generating substantially unipolar fast rise time pulses comprising:

(a) a rotatable magnetic drum having a non-magnetic cylindrical core, a magnetic coating on the core capable of assuming a state of remanence, and a plurality of longitudinal slots formed substantially through the magnetic coating to interrupt the continuity of a circumferential magnetic path through the magnetic coating;

(b) a magnetic pickup head adjacent to the drum;

(c) means for rotating the drum relative to the pickup head; and

(d) means disposed in spaced relation to the pickup head for producing a magnetic field which intersects the magnetic coating at a point in a circumferential path passing adjacent to the pickup head to produce substantially unipolar pulses having fast times in the pickup head.

5. An apparatus as recited in claim 1, wherein the spaced distances between adjacent segments of magnetic material are substantially narrower than the Width of individual ones of said segments along the direction of movement of said base.

'6. An apparatus as recited in claim 4, wherein the distance between adjacent ones of said plurality of longitudinal slots is substantially greater than the Width of individual ones of said slots.

References Cited UNITED STATES PATENTS 1,659,729 2/1923 Gannett 3 l0168 2,516,178 7/1950 Bohannon 3l0155 2,669,669 2/1954 Spaulding 3l0l55 3,122,666 2/1964 Guiot 310l56 3,132,337 5/1964 Martin 310-170 MILTON O. HIRSHFIELD, Primary Examiner R. SKUDY, Assistant Examiner US. Cl. X.R. 310-45,

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