US 3398328 A
Description (OCR text may contain errors)
United States Patent 3,398,328 ELECTRICAL RELAY CIRCUITRY FOR MAGNE- TIZING SYSTEMS AND THE LIKE Leonard Piekarski, Pomona, Calif., assignor of one-fourth each to Irving B. Collins, Los Angeles, Veronica Whitesides, Culver City, T. A. Smith, Long Beach, and Carroll E. Isham, Buena Park, Calif.
Filed Apr. 21, 1966, Ser. No. 544,207 Claims. (Cl. 317-123) This invention relates to improved electrical apparatus for opening and closing an electrical circuit, with certain features of the apparatus being in some respects especially useful for momentarily closing a circuit to a unit which is responsive to or actuable by an electrical impulse of short duration. For instance, equipment embodying the invention is very useful for closing and then'opening the circuit to a magnetizing coil, so that a rapid surge of current may pass through the coil for magnetizing elements placed therein. For simplicity of discussion, the invention will be described hereinafter primarily as applied to the energization of such magnetizing coils.
Though the magnetization of an element by subjection to the magnetic field within a coil does not require that the field be maintained for any extended period of time, and may be attained almost instantaneously by an electrical impulse of very short duration, the current flow during that short interval must in most instances be very heavy, in order to assure the development of a sufficiently intense magnetic field to attain the desired magnetizing action. This high amperage current flow has in the past proven very difiicult to control because of the problems encountered in attempting to devise a switch or relay capable of instantaneously closing the coil energizing circuit without causing rapid pitting or burning of the switch or relay contacts by the heavy flow of current, and the resultant sparking between the contacts during closure. These contacts therefore have been capable of functioning for only a very short active life, and have been unreliable and unpredictable in operation at all times.
A major object of the present invention is to provide improved circuit for energizing and de-energizing a magnetizing coil or other electrically operated unit, with the circuit being especially constructed to positively avoid damage to the controlling contacts, even though the current passed through those contacts may be relatively high. Certain particular features of the invention relate to the construction and manner of energization of a relay which is utilized in the overall circuit of the invention for opening and closing the circuit to the coil or other electrically Y operated unit.
In accordance with the teachings of the invention, the coil of the circuit closing relay is energized by alternating current, desirably 60 cycle, 110 volt. A.C. The relay is so constructed, and the energizing potential and frequency are so selected, that the coil when energized is not effective to pull the movable contact or contacts of the relay to closed position as positively as is desired in most relay arrangements. Instead, the movable contact or contacts are purposely left free to vibrate through a very substantial range of movement relative to the stationary contacts while the relay is closed. More particularly, the movable contacts vibrate or oscillate at the frequency of the energizing current, that is, usually 60 cycles per second. This vibratory motion causes the movable contacts to continuously and repeatedly shift relative to and over the surface of the engaged stationary contacts while the relay is closed, to in this way actually mechanicallypolish the engaging surfaces of the contacts, in a manner continuously guarding against the development of any pits or other irregularities in the surfaces ,of the contacts. It is found that these vibratory relay contacts can be closed and opened under heavy load conditions repeatedly and almost indefinitely without adversely affecting their current carrying capacity, and without pitting of or other damage to the contacts.
To attain the above discussed results, the relay may be of a construction essentially similar to that customarily employed for direct current relays, but with this direct current type of relay being energized by alternating current, as discussed above, and preferably of a voltage substantially higher than would be employed if the relay were under direct current operation. Structurally, the relay should have considerably less stationary iron or other stationary magnetic material than is present in most alternating current relays, so that the magnetic circuit provided for the flux is not of a great enough flux carrying capacity to smooth over the irregularities of the alternating current supply, and thus maintain the contacts in tightly closed non-vibratory condition.
The above and other features and objects of the invention will be better understood from the following detailed description of the typical embodiment illustrated in the accompanying drawing, in which:
FIG. 1 illustrates somewhat diagrammatically and in perspective a magnetizing device constructed in accordance with the invention;
FIG. 2 shows the electrical circuit of the Fig. 1 magnetizer;
FIG. 3 illustrates, partially in elevation and partially in section, a relay of the type preferably utilized in the FIG. 2 circuit;
FIG. 4 is a plan view of the FIG. 3 relay, taken on line 44 of FIG. 3; and
FIG. 5 is a fragmentary vertical section taken on line 5-5 of FIG. 4.
Referring first to FIG. 1, I have illustrated at 10 a magnetizing coil which is wound helically about an axis 11, and is hollow to enable the insertion into the interior of the coil of an element 12 which is to be magnetized by electrical energization of the coil. The coil receives high amperage current from a control box 13 through two electrical leads 14 and 15. Power is supplied to control box 13 through a cord 16 from any appropriate source of alternating current diagrammatically represented at 17 in'FIG. 2, with the two conductors in cord 16 being designated 18 and 19 in FIG. 2. Preferably, as previously stated, the power source 17 is volt, 60 cycle per second, alternating current.
The control box 13 contains a full wave rectifying circuit 20, to the input side of which power source 17 is connected, by connection of lead 19 to the rectifier circuit at 21, and connection of lead 18 to the rectifier circuit through a two-Way manually operated control switch 22 and a line 23 leading to input terminal 24. The result ing direct current leaves the rectifier circuit through two leads 25 and 26, across which two capacitors 27 and 28 are connected in parallel, with a resistor 29 preferably being connected into lead 26 between the rectifier and the capacitors.
- Capacitors 27 and 28 may typically have a value of 6,000 microfarad, Volt DC, while the resistor 29 may typically have a rating of 8 ohms, 18 watts.
An indicator light 30 is shunted across the input side of rectifier circuit 20, to indicate when the movable contact 31 of switch 22 is in its upper position for supplying alternating current to the rectifier circuit, and thus charging capacitors 27 and 28. A voltmeter 32 is connected across the capacitors, to indicate the amount of the charge which has been attained on the capacitors, so that an operator can readily tell when the charge is suflicient to call for discharging the capacitors through the magnetizin g coil 10.
This discharging of the capacitors is controlled by downward actuation of the movable contact 31 of switch 22, to close through that switch a circuit leading from alternating current power source 17 to coil 33 of a control relay 34. The movable contact 35 of relay 34 is actuable magnetically to closed position with respect to a pair of contacts 36 and 37 by energization of coil 33, to thus close a discharge circuit from capacitors 27 and 28 to magnetizing coil through leads 14- and 15.
With reference now to FIGS. 3 to 5, which show a preferred construction for relay 34, it is noted that coil.
33 of this relay may consist of a large number of turns of wire wound in many layers about an inner tube 38 formed of non-magnetic material, such as an appropriate brass or the like. The coil may thus form an essentially annular structure, as illustrated in FIG. 3, with a cylindrical hollow housing or outer covering 39 being disposed about the periphery of the coil, and being concentric with coil 33 and tube 38, all being centered about a main vertical axis 40 of the relay. Housing 39 may be rigidly brazed, welded, or otherwise secured to a transverse bottom wall 41 extending across the bottom of the coil and tube 38, and having ears or tabs 42 by which the coil may be mounted to a supporting structure 43. The upper end of housing 39 may be closed, about tube 38, by one or a pair of essentially annular discs 43, whose inner edges may engage tube 38 at 44, and which discs 43' may be secured rigidly to an upper flange 45 of housing 39 and a non-magnetic and non-electrically conductive top member 46 by screws 47. Members 46 may be formed of an appropriate plastic material.
The armature 48 of the relay may be externally cylindrical and centered about axis 40, and be a fairly close fit within the interior of tube 38, so that the armature 48 is magnetically actuable downwardly by coil 33 from the full line position of FIG. 1 to the broken line position of that figure. This armature 48 is of course formed of an appropriate magnetic material, such as iron. The upper end of armature or plunger 48 may have an annular flange 49 engageable downwardly against the upper end of tube 38 to limit downward movement of the armature. Also, the armature may rigidly carry an upwardly projecting reduced diameter portion 50, and a still smaller diameter portion 51, which resiliently and shiftably carry the movable contact or cross head 35 which engages stationary contacts 36 and 37 of the relay. Movable contact 35 is normally held in the full line position of FIG. 3 relative to the plunger, by an upper spring 52 which is confined between movable contacts 35 and an upper enlargement 53 carried by the armature, with this spring 52 coacting with a second and lower spring 54 confined between the upper side of the plunger and movable contact 35. These two springs are insulated from contact 35 by an annular non-conductive grommet structure 55, mounted wtihin an aperture in contact 35. The springs of course act together to yieldingly urge the armature and movable contact upwardly to the normally open full line position of FIG. 3.
Contact 35 is elongated in a left to right direction as viewed in FIG. 3, and has two contact surfaces 56 formed at its opposite ends, and facing downwardly for engagement with inverted contact surfaces 57 of the two stationary contacts 36 and 37. The stationary contacts are connected by straps 58 to terminals 59 by which the stationary contacts are connected into the FIG. 2 circuit.
The resilient movement of contact 35 relative to stationary contacts 36 and 37 is limited by a pair of upstanding block portions or bosses 60 of the nonconduotive member 46. These two bosses project upwardly at opposite sides of contact 35, as brought out in FIGS. 4 and 5, and have inner parallel vertical planar surfaces 61 which are spaced slightly outwardly from the opposite parallel side edges 62 of contact 35, so that the contact 35 is free for some lateral movement, and is free for limited turning movement about vertical axis 40, but
both of these types of movement are definitely limited by engagement of edges 62 with boss surfaces 61.
The various electrical and magnetic parameters of relay 34, and the voltage and frequency of the alternating current which energizes coil 33 of this relay, are all so selected and predetermined as to attain an automatic polishing action between contact 35 and the engaged contacts 36 and 37, whenever coil 33 is energized to pull armature 48 downwardly. More particularly, the energizing voltage and current are sufi'icient to pull armature 48 and its resiliently carried movable contact 35 downwardly from the full line position of FIG. 3 to the broken line position of that figure, whenever coil 33 is energized by the alternating current supplied to input lines 18 and 19. However, the holding action of the coil with respect to armature 48 is purposely reduced to a minimum value which, though holding contact 35 substantially closed, will still allow that contact to vibrate relative to stationary contacts 36 and 37 through a very substantial and easily visible range of movement, preferably at least as much as about one sixty-fourth of an inch '(also desirably through a distance at least about as great as 5% of the maximum dimension of each contact face, i.e. 5% of the maximum dimension of the actual contacting portion of faces 56 and 57), so that faces 56 of the movable contacts repeatedly and continuously wipe across and vibrate relative faces 57 of the stationary contacts to effectively polish all of these contact faces and maintain them in optimum current transmitting condition. The vibratory motion thus attained can be observed to produce different types of movement of the movable contact 37, so that the movable contact faces 56 and 57 move horizontally across the upper surfaces of contact faces 57, and may in many instances follow a somewhat circular path in wiping across surfaces 57, with different portions of contact 35 moving alternately into engagement with the two edges 61 of the motion limiting bosses, and with the springs 52 and 54 facilitating the vibratory motion because of their resilient mounting of movable contact 35 relative to the armature or plunger.
To describe briefly a cycle of operation of the circuit of FIG. 2, assume that switch 22 is initially in its intermediate open position, and that the element 12 of FIG. 1 is inserted into coil 10 to a position at which it is to be magnetized by the coil. An operator then moves contact 31 of the switch 22 upwardly to energize the rectifier clrcuit 20, so that direct current is supplied to capacitors 27 and 28, to charge them. When voltmeter 32 indicates that an appropriate charge has been attained on the capacitors, the movable contact of switch 22 is actuated downwardly to open the circuit to the rectifier arrangement, and close the circuit to coil 33 of the relay. The alternating current within coil 33 thus pulls anmature 48 and the connected movable contact 35 downwardly to close the discharge circuit between stationary contacts 36 and 37, so that the capacitors 27 and 28 suddenly discharge through the contacts of the relay to magnetizing coil 10, to attain the desired magnetizing action. The discussed vibratory motion of contact 35 relative to stationary contacts 36 and 37 polishes all of these contacts in the manner discussed, and prevents development of pits or craters on the contact surfaces, so that the relay may be repeatedly opened and closed through many cycles, and almost indefinitely, without encountering the contact deterioration or damage which is a customary problem in magnetizers and other equipment of the discussed general type.
Obviously, many variations may be made in the structure of the relay and its relationship to the energizing alternating current while still attaining the discussed contact vibrating effect. No attempt will be made to set forth all of these diiferent possible variations of the invention since persons versed in the electrical field will be able to devise apparatus embodying the invention from the above teachings. Some of the parameters which may be altered to achieve and. control vibration of movable contact 35 of the relay are the particular construction of coil 33, the ELmOlJIItJOfEStHlIlOIJEIIY magnetic material associated with the coil and typically constituting the parts 39, 41, '43 and 45,, the size, cross section, and flux capacity of this sta tionary magnetic material as compared with the movable magnetic material of armature 48, the magnetic retentivity of the magnetic material, the strength of springs 52 and 54, and the voltage and frequency of the energizing alter nating current. A characteristic which is especially important is the mentioned feature, relating to the amount of stationary magnetic material associated with the coil. In this connection, it is noted that the coil is preferably free of the relatively large amount of stationary laminated iron or other magnetic material which is normally present in an alternating current coil, and which usually provides in an alternating current coil a substantially complete magnetic circuit entirely about the coil of very great flux carrying capacity. Desirably, no such laminations are present in the relay utilized in my invention, or if any laminations are present they have a flux capacity which is not great enough to prevent vibration of contact 35.
For best results, the stationary magnetic material is essentially non-retentive or soft magnetically (i.e. has a minimum magnetic retentivity), and for this purpose may typically be formed of soft iron or the like. Also, it is preferred that the stationary magnetic material, if any is present in the main magnetic actuating circuit of the relay, be sulfciently limited in cross section to have a maximum flux capacity (along that circuit) which is not greater than the maximum flux capacity of the armature along the circuit, and preferably not greater than about 40% of that armature flux capacity. For purposes of this limitation, the magnetic circuit in FIG. 3 may extend vertically within the armature, then horizontally or radially through plates 43, then vertically through housing 39, horizontally through plate 41 and upwardly through a stationary core 148 if such is present (with all of the elements 43, 39, 41 and 148 typically being of magnetic material but preferably of fairly small flux capacity as indicated). As will be apparent the effective flux capacity of the stationary parts is of course determined by and equal to the capacity of that portion of the stationary material which is most poorly conductive magnetically and which therefore defines the minimum flux capacity point along the stationary flux path. Similarly the minimum flux capacity portion of the armature determines the effective overall capacity of that part.
1. Apparatus comprising capacitor means, means for charging said capacitor means, a unit to be energized by discharge of said capacitor means, a discharge controlling relay having a coil and having contacts connected into a discharge circuit from said capacitor means to said unit, said contacts including a first contact and a second contact movable relative thereto into circuit closing engagement with the first contact by energization of said coil, and means for supplying alternating current of a predetermined voltage to said relay coil to close said contacts and thereby discharge said capacitor means to said unit, said relay being constructed to vibrate said second contact very substantially when energized by said predetermined voltage of alternating current and to an extent repeatedly and continually shifting said second contact relative to the other contact while the contacts are closed to thereby mechanically polish the contacts and prevent pitting thereof.
2. Apparatus as recited in claim 1, in which said unit is a magnetizing coil for magnetizing an element in the vicinity thereof upon discharge of said capacitor means.
3. Apparatus as recited in claim 1, in which said charging means include a rectifier circuit energizable by alternating current and operable to supply direct current to said capacitor means.
4. Apparatus as recited in claim 1, in which said charging means include a rectifier circuit energizable by alternating current and operable to supply direct current to said capacitor means, said means for supplying alternating current to said relay coil including switch means for successively connecting a common source of alternating current first to said rectifier circuit to charge the capacitor means, and then to said relay coil to discharge the capacitor means through said contacts.
5. Apparatus as recited in claim 1, in which said relay is constructed to vibrate said second contact through a distance as great as one sixty-fourth of an inch relative to the other contact while the contacts are closed.
6. Apparatus as recited in claim 1, in which said relay has an armature connected to said movable contact to actuate it and projecting into and movable axially within said coil.
7. Apparatus as recited in claim 1, in which said relay has an armature connected to said movable contact to actuate it and projecting into and movable axially within said coil, and means connecting said movable contact to said armature resiliently.
8. Apparatus as recited in claim 1, in which said relay has a movable armature formed of magnetic material for actuating said movable contact, and in which, if any stationary magnetic material is present in the magnetic circuit of the relay, said stationary material does not have a flux capacity along said circuit over about 40% of the flux capacity of said armature therealong.
9. Apparatus as recited in claim 1, in which said relay has a magnetic material armature connected to said movable contact to actuate it and projecting into and movable axially within said coil, said movable contact being a cross head disposed transversely of the axis of the coil at the outside thereof and engageable at opposite ends with two of said first contacts to close said discharge circuit, spring means connecting said cross head to said armature shiftably and resiliently and enabling some lateral movement of the cross head transversely of said axis, said relay having stationary magnetic material near the coil in sufficient quantity to hold the movable contact essentially closed when the coil is energized but not suflicient to prevent said vibration.
10. Apparatus as recited in claim '9, in which said unit is a magnetizing coil, said charging means including a rectifier circuit energizable by alternating current and operable to supply direct current to said capacitor means, said means for supplying alternating current to said relay coil including switch means for successively connecting a common source of alternating current first to said rectifier circuit to charge the capacitor means, and then to said relay coil to discharge the capacitor means through said contacts.
11. The combination comprising a relay including a coil to be energized by alternating current of a predetermined voltage, a first contact, and a second contact actuable relative to the first contact into circuit closing engagement with the first contact by energization of said coil, and means for supplying alternating current of said predetermined voltage to said coil, said relay being constnucted to vibrate said second contact very substantially when energized by said predetermined voltage of alternating current and to an extent repeatedly and continually shifting said second contact relative to the other contact while the contacts are closed to thereby mechanically polish the contacts and prevent pitting thereof.
12. Apparatus as recited in claim 11, in which said relay is constructed to vibrate said second contact relative to the other contact while the contacts are closed through a distance as great as 5% of the maximum dimension of the contacting faces of said contacts.
13. Apparatus as recited in claim 11, in which said relay has an armature connected to said second contact to actuate it and projecting into and movable axially within said coil.
14. Apparatus as recited in claim 11, in which said relay has a movable armature formed of magnetic material for actuating said second contact, and in which, if any stationary magnetic material is present in the magnetic circuit of the relay, said stationary material does not have a flux capacity along said circuit over about 40% of the flux capacity of said armature therealong.
15. Apparatus as recited in claim 11, in which said relay has a magnetic material armature connected to said second contact to actuate it and projecting into and movable axially Within said coil, said second contact being a cross head disposed transversely of the axis of the coil at the outside thereof and engageable at opposite ends with two of said first contacts, spring means connecting said cross head to said armature shiftably and resiliently and enabling some lateral movement of the cross head traversely of said axis, said relay having stationary magnetic material near the coil in sufficient quantity to hold the second contact essentially closed when the coil is energized but not sufiicient to prevent said vibration. 7
References Cited STATES PATENTS UNITED 1,466,654 8/1923 Clough 307-137 X 2,157,640 5/1939 Swarthout 307138 X 2,817,774 12/1957 Kniel et al. 307- 137 3,248,633 4/1968 Guarrera 317-451 X LEE T. I-HX, Primary Examiner.