US3012191A

US3012191A - Gradiometer

Info

Publication number: US3012191A
Application number: US628912A
Authority: US
Inventors: Charles E Miller; Walter H Barkas; Jr Roy E Uptegraff
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-11-15
Filing date: 1945-11-15
Publication date: 1961-12-05
Anticipated expiration: 1978-12-05

Description

Dec. 5, 1961 c. E. MILLER ETAL GRADIOMETER 2 Sheets-Sheet 1 Filed NOV. 15, 1945 NTORS F, Jr.

W ATTORNEY Y 4 wrt 1 Coil INVE CHARLES E. MILLER WALTER H. BARKAS ROY E. -UPTEGRAF FIG.2

e 9 n lag Dec. 5., 1961 c. E. MILLER ETAL 3,012,191

GRADIOMETER Filed Nov. 15, 1945 2 Sheets-Sheet 2 INVENToRs CHARLES E. MILLER WALTER H. KAS

ROY E. UPT AFE-v ATTORNEY United States Patent Orifice 3,012,191 GRADIOMETER Charles E. Miller, Walter H. Barkas, and Roy E. Uptegrati, ir., Seattle, Wash., assignors to the United States of America as represented by the Secretary of the Navy Fitted Nov. l5, 1945, Ser. No. 628,912 l Claims. (Cl. 324-43) This invention relates generally to iniiuence-type detonating mechanisms for explosive ordnance, and more particularly to influence mechanisms of the gradiometer type, designed to automatically initiate rdetonation of the explosive charge upon proximity of extraneous magnetic material of predetermined characteristics, corresponding to a target, yet so designed that unwanted detonation will not occur due to the influence of the earths magnetic eld, or due to other factors to which it is desired that the detonating means be unresponsive. Such devices are called gradiometers because they respond only to variations or gradients of the magnetic field that exist in the vicinity of magnetic materials, and are not affected by a uniform magnetic iield.

It has of course been known for many years that a coil of wire attached to a substantially rectilinearly moving item of ordnance such as a underwater torpedo will have a voltage induced in it as the torpedo moves through the non-uniform magnetic eld present about a ship. 'This voltage can be used to tire the-explosive charge of the torpedo as it comes into the vicinity of a ship. As the torpedo, as during its run toward the target, is always moving through the magnetic lield of the earth, however, any motion (roll, pitch or yaw) other than translational, will give voltages due to the changing components of the earths field through the coil. This is likely to result in premature tiring of the torpedo, particularly if the behavior of the torpedo is erratic.

Theoretically the indicated difliculty can be overcome by substituting for the single coil a gradiometer consisting of two spaced-apart but identical coils rigidly mounted with their axes parallel and electrically connected in series opposition. It has been found, however, that such a system mounted in an arbitrary manner on a magnetic and electrically conducting body, such as a torpedo, may also give a voltage output on motion in a uniform eld such as that of the earth, and so defeat the purpose of use of the gradiometer principle. This voltage arises from the magnetism and eddy currents induced in the metal components of the torpedo as it undergoes angular motion in the earths lield and which, in turn, give rise to time Varying magnetic gradients and phase gradients in the region of the gradiometer.

One of the principal objects of the present invention, therefore, is to provide an intluence operated exploder of the gradiometer type particularly. suitable for use in torpedoes and so designed as to produce a voltage When moved through a non-uniform magnetic eld, as the lield about a ship, but to produce no response for any type of motion in a uniform eld (the eld of the earth), such as roll, pitch or yaw of the torpedo during its run toward the target.

Another object of the invention resides `in the provision f l of an exploder mechanism of this character having simple and etfective adjustable means for compensating the coil system against any unbalanced conditions which would be produced by the presence of steel and/ or other magnetic parts of the torpedo such as the shell, the air flask and the large magnetic iield gradients exist; i.e. to an area relatively close to the target.

Other objects of the invention will be evident from a consideration of this disclosure in its entirety.

In the drawings:

FIGURE l is a longitudinal sectional view of a gradiometer constructed in accordance with the present invention, certain parts being shown in elevation;

FIGURES 2 and 3 are longitudinal sectional viewsV on a larger scale of opposite end portions of the gradiometer, particularly showing the compensating means;

lFIGURES

4 and 5 are cross sectional views taken substantially on the lines 4 4 and 5-5, respectively, of FIGURE 3.

FIGURE 6 is a cross section taken substantially on the line 6-6 of FIGURE 1;

FIGURE 7 is a cross section taken substantially on the line 7-7 of FIGURE 2;

FIGURE 8 is a sectional perspective view showing the improved gradiometer and related components installed in a torpedo war head; and

FIGURE 9 is a schematic wiring diagram.

The principal component of this invention is a gradienteter, from which the firing signal is derived, consisting of two identical coils, each containing many turns of line copper wire. The two coils are spacedly mounted on a single core rod formed of a suitable magnetic alloy.A The single rod mounting assures maintenanceV of the coils in accurately parallel relation. The whole gradiometer .assembly is so mounted in the torpedo head as to give each coil, as nearly as possible, an identical relationship of symmetry or asymmetry with respect to the torpedo as a whole. This minimizes effects due to magnetic induction in the torpedo. The lack of fore and aft symmetry of the torpedo about the gradiometer assembly is compensated by a longitudinal corrector, while geometrical and magnetic asymmetries in an athwartship direction are compensated for byan athwartship corrector, so oriented that no voltage is induced in the coil system on changing the uniform component of magnetic field in an athwartship direction. Vertical asymmetries (along the axis of the gradiometer) are reduced by adjusting a vertical corrector screw provided in one end of the magnetic rod and by the introduction of phase-shift rings at each end of the gradiometer rod. Y y

Referring now in detail to the drawings, wherein like reference numeralsV indicate like parts throughout the several views, the numerals 1-and 2 designate, respectively, inner and outer concentric sleeves forming a double walled casing. The sleevesare preferably formed of non` in the hull within the sealed area surrounded by the secured ange rims. Through these openings end'caps 13,'

35 are accessible for purposes of adjustment as will pres-v ently more fully appear. Y

The outer casing sleeve 2 is threaded into, and sealed as by solder'with respectv to, the -anges 3=and 4,' while the inner casing sleeve is rotatable;l Medially secured to and projecting forwardly of the casing 2 is a corrector mounting element in the form Yofan internally threaded ange 6 linto which alongitudinal corrector 7 comprising a cylindrical Vmass off magnetic material'is designed to'bescrewed to clamp anon-magnetic corrector ring 7"to secure phase balance, The sleeve 6 is secured to the casing as by silver solder in av longitudinal position Which Patented Dec. 5, 196i..

is determined by the magnetic characteristics of the individual installation in which the gradiometer is incorporated. lts function will presently be discussed in detail.

The coils and 1.1 are substantially equidistantly spaced from the midpoint of the gradiometcr unit. The two coils are identical in construction, each being formed in two sections in the illustrative embodiment shown, although this is of course a matter of choice, and each complete dual coil assembly comprises a total of approximately 100,000 turns of iine (number 40 B. & S. gauge) wire, layer wound on a suitable card-board or libre sleeve. The magnetic alloy core rod 12 extends axially substantially the entire length of the inner casing sleeve l. At one end (FIG. 2) the core rod is keyed, as at 13 with respect to the closure plug 1S. Plug 15 is formed of insulating material such as plastic and screwed into the end of casing sleeve 1. A sealing gasket 16, of rubber, overlies the end of the casing and is held in place by a sealing cap 17. Cap 18 is held in place by screws 19, a sealing gasket 20 being contined beneath the cap for water-proofing.

A cable 21, which extends through a fitting 22 in the side wall of the flange 4, provides electrical connection between the coils 10 and 11 and the ring apparatus, shown generally in FIG. 8 at 23.

The coils 10 and 11 are held in their spaced relation by

central spacers

24 and 25 of Bakelite or other insulating plastic. Mounted on the core rod 12 between said spacers is an

athwartship corrector

2,6 of magnetic material such as cold rolled steel, contoured to dit the rod 12 and held in place on the rod by Screws 27. A condenser 28, for -ltering out spurious impulses at high frequencies, such as might be caused by vibration of the torpedo, is mounted by a strap 29, the ends of which are secured under the heads of said screws 27.

The end of the casing sleeve 1 which terminates in the flange 3 is closed by an insulating plug 30 of Micarta or other suitable material, centrally bored to receive the end of the rod 12 which extends substantially therethrough. The end of the core rod is bored and tapped to receive a steel screw 31 which constitutes a vertical corrector and is designed to be locked in place by a nonmagnetic lock nut 32 or a cement of litharge-glycerin or the like. A cap 32 is screwed into the plug 3) about the end of the corrector to protect the latter. A copper ring 34 (or a series of rings) is carried about the rod 12 in a recess in the plug 30 and is held in place by the cap 33. The ring 34 acts as a phase shifter and provides an adjustment for synchronizing the electromotive forces which are generated in the two coils of the gradiometer when the torpedo rotates in the earths magnetic iield. The dimensions of the ring may be varied to effect the desired adjustment, and if it is desired a similar ring or rings may be employed at the opposite end of the assembly to extend the range of adjustment. Cap 35 which closes the end of the flange 3 is held in place by screws 36.

To the end that the coils 10 and 11 will be properly positioned, magnetically, on the rod 12, shims, or spacers, 37, 37 are provided. The shims 37 nearest the plug 15 may be made of copper to provide a phase shifter cooperating with the ring 34, while the other shim-s are of non-conducting non-magnetic material.

The position of the inner casing sleeve 1 in the outer sleeve 2 is adjusted, to assure proper magnetic balance, by providing a seating ring 38 and a clamping ring 39. As seen in FIGURE 3, a mounting flange ring 49 is carried on the end of the casing sleeve 1 by means of the plug 30, which is threaded into ring 40 as well as into sleeve 1. Ring 40 normally rests against the seating ring 38, and the position of ring 38 will be seen to tix the longitudinal position of the core rod and coil assembly. Ring 38 is screwed into the threaded socket 41 of the end flange 3 the proper distance to locate the coils 10 and 11 for proper magnetic balance. When initial adjustments are being made, the proper setting for the ring 33 is ascertained by trial and the ring is then locked, as by tightening a set-screw 42 for setting the threads, before the gradiometer is set in position.

A pin 43 engages in a slot 44 to key the rod 12 against rotation and to hold the athwartship corrector against displacement from its proper position. By virtue of the key 13, the core rod, and so the corrector 26, may be turned by turning the inner sleeve 1 when ring 313 is freed by releasing set-screw 42.

After the coils and corrector 26 have been properly located, the parts are locked in position by the ring 39 which, like the ring 38, is partially -split radially and litted with a set screw for locking the threads.

After the coils and the athwartship corrector have been properly positioned in the casing 1, the interior of said casing is filled with a suitable potting compound (not shown).

The operation of the invention and the functions of the correcting devices are believed to be obvious from the foregoing, but may briefly be summarized as follows:

Although the coils 10 and 11 are made in two sections, each functions as a single coil and is shown as such in the schematic diagram, FIG. 9. The two coil elements 10 and #11 are connected in series opposition, as there shown, and their output is shunted by the condenser 23.

A magnetically permeable rod of `finite length such as the core rod 12, when subjected to translational and/or rotational motions in a non-uniform magnetic lield, will become so magnetically polarized that the magnetic inductions at any two points equdistant from the center of the rod at any given instant of time will not be equal. The corrector-s incorporated in the improved gradiometer equalize the magnetic lield which surrounds the rod 12 as a result of movement of the torpedo assembly in the earths field. Thus, the system is initially in balance, and after the torpedo has been fired and reaches the non-uniform magnetic iield of the target, electrornotive forces will be set up in each of the coils 10 and 11. However, these forces will not be equal since they have not been compensated by the correctors. An electromotive force accordingly results, and this is made to effect operation of the `tiring mechanism contained in the housing 23 (FIGURE 8). Such mechanism, as previously stated, forms no part of the present invention, and may include suitable amplifying and primerdetonating means.

Each gradiometer is adjusted for the conditions obtaining in the torpedo in which it is installed. Longitudinal balance is effected by providing a steel corrector 7 (with corrector ring 7') of the proper length and diameter which is positioned in the receptacle formed by flange 6 with its inner face the optimum distance from the wall of the casing sleeve 2. Athwartship adjustment is accomplished by rotating the casing `1 which rocks the rod 12 and with it the corrector 26.

Vertical adjustment is, of course, accomplished by setting the corrector (screw) 311 in its optimum position in the end of the rod 12, and adjusting the ring 34.

From the above description it will be understood that the invention provides a `grtnliometer type exploder of unitary, simple, rigid and watertight construction, equipped with provision for balancing out all effects which might give rise to premature firing as the torpedo moves through the magnetic tield of the earth on its 'way to the target. While it will be appreciated that the preferred form of the invention herein disclosed 1s well calculated to fulfil-l the objects and advantages primarily stated, it will also be understood that the invention is subject to variation, modification and change within the spirit and scope of the subjoined claims.

What is claimed is:

1. A gradiometer for installation in a device having asymmetric magneto-electric characteristics, comprising a core, a pair of coils having like characteristicsspacedly mounted on said core and connected in series opposition,

whereby a signal may be derived from the output of said coils upon movement of the gradiometer through a non-uniform field, and means for otsetting such asymmetric characteristics including a phase shifting element inductively coupled to one of said coils.

2. Means as set forth in claim 1 in which said phase shifting element comprises a substantially annular inductor mounted concentrically with respect to said core and the last mentioned coil.

3. Means as set forth in claim 1 in which said core is substantially straight, said phase shifting element comprising a substantially annular inductor mounted concentrically upon said core near one end thereof, and a longitudinally adjustable supplemental core section adjacent said same end of the core.

4. A gradiometer for installation in a device having asymmetric magneto-electric characteristics, comprising a substantially straight core, a pair of coils having like characteristics spacedly mounted on said core and connected in series opposition, whereby a signal may be derived from the output of said coils upon movement of the gradiometer through a non-uniform eld, said core being initially rotatably adjustable about its longitudinal axis, means for olfsetting such asymmetric characteristics, including an asymmetric mass of magnetic material mounted adjacent said core in the area between the coils and movable by rotary adjustment of the core, and means for securing said core in it adjusted position.

5. Means as set forth in claim 4, in which said mass is carried by and initially rotatably adjustable with said core.

6. A gradiometer adapted for installation in a device having asymmetric magneto-electric characteristics, comprising a substantially straight core, a pair of coils having like characteristics spacedly mounted on said core and connected in series opposition, whereby a signal may be derived from the output of said coils upon movement of the gradiometer through a non-uniform ield, said core being initially rotatably adjustable about its longitudinal axis, and means for offsetting such asymmetric characteristics, including an asymmetric mass of magnetic material mounted adjacent said core in the area between the coils and movable by the rotary adjustment of the core, means for securing said core in its adjusted position, and a second asymmetric mass of magnetic material ixedly mounted in spaced relation to the first mentioned mass, said masses lying substantially in a plane perpendicular to the core.

7. A gradiometer assembly adapted to installation in a device having asymmetric magneto-electric characteristics, comprising a substantially straight core, a pair of coils having like characteristics spacedly mounted on said core and connected in series opposition, whereby a signal may be derived from the output of said coils'V when the assembly is moved through a non-uniform magnetic eld, an outer casing of non-magnetic material enclosing said assembly, an inner casing surrounding said coils and core and rotatable within the rst mentioned casing, said core being keyed to rotate with said inner casing, and means for offsetting such asymmetric characteristics, including an asymmetric mass of magnetic material secured to and rotatable with said core in the area between said coils.

8. LMeans as set forth in claim 6 in which said outer casing is fixed, and additional offsetting means comprising a second mass of magnetic material affixed to said outer casing.

9. A gradiometer for installation in a device having asymmetric magneto-electric characteristics, comprising a core, a pair of coils having like characteristics spacedly mounted on said core and connected in series opposition, whereby a signal may be derived from the output of said coils upon movement of the gradiometer through a non-uniform magnetic eld, and means inductively coupled to one of said coils, for oisetting such asymmetric characteristics. l

10. A gradiometer for installation in a device having asymmetric magneto-electric characteristics, comprising a core, a pair of coils having like characteristics spacedly mounted on said'core and connected in series opposition, whereby a signal may be derived from the output of said coils upon movement of the gradiometer through a non-uniform magnetic eld, and an auxiliary core adjustably secured to the first-named core `for correcting for lsaid asymmetric characteristics, said auxiliary core having a non-magnetic electrically conductive ring thereon to act as a phase correcting means.

` References Cited in the le of this patent UNITED STATES PATENTS