US3098917A - Method and apparatus for repairing armatures and the like - Google Patents

Description

July 23, 1963 R. A. WILLIAMS 3,098,917

METHOD AND APPARATUS FOR REPAIRING ARMATURES AND THE LIKE Filed Sept. 26, 1961 44 INVENTOR zagmmwm BY Z W ATTORNEYS United States Patent 3,098,917 METHOD AND APPTUS FOR REPAERHNG ARMATUREEE: THE MIKE Ralph A. Williams, 735 Dickinson St, Memphis, Tenn. Filed ept. 26, 1961, Ser. No. 140,877 6 Claims. (Cl. 219-U) The present invention relates in general to methods and apparatus for repairing the insulated coils or loops of low voltage electrical apparatus such as automotive type armatures wherein insulated wires or bars are applied around or to a body of a grounding type of material.

Armatures cease to operate when the normally insulated Wires forming the coils thereof are grounded at any point to the base of the apparatus, for example by the soaking of the insulated material with oil or water or by physical contact between the wire and the base through removal of the insulating material or the introduction of an electrically conductive foreign substance between the wire and the base. The methods heretofore commonly used for repairing automotive type arm-atures having grounding short circuits between the electrical conductors making up the coils thereof and the electrically grounded body on which the coils are mounted have been very inadequate and have resulted in a great many armatures being scrapped. The most frequently used methods employed in an attempt to repair such armatures was to simply hit them with hammers or push screw drivers down into the coils in an attempt to dislodge the material producing the grounding path. About the only other practical means of repairing armatures having this defect was to completely rewind them which obviously was a very time-consuming and expensive procedure.

An object of the present invention is the provision of a novel method and apparatus (for repairing automotive type armatures having insulated wires which have become grounded, wherein a high amperage and low voltage electrical arcin condition is produced to remove the grounding material.

Another object of the present invention is the provision of a novel method and apparatus for repairing automotive type armatures having insulated wires which have become grounded, wherein a direct current of low voltage and rel a tively high amperage is applied to the armature in such a way as to cause an arcing condition which burns away or otherwise removes the grounding material with a voltage low enough to prevent break down of the dielectric insulating material.

Another object of the present invention is the provision of a novel method and apparatus for testing automotive type armatures to determine whether grounding conditions exist and substantially simultaneously eliminate such groundings if detected.

Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawing, illustrating one preferred embodiment of the invention.

In the drawing:

FIGURE 1 is a side elevation view of a typical electric motor armature illustrating diagrammatically grounding conditions of the type to be cured by the method and apparatus of the present invention and the condition of the defect areas after correction;

FIGURE 2 is a fragmentary vertical transverse section view to enlarged scale taken along the line 2-2 of FIG- URE 1; and

FIGURE 3 is a schematic diagram of apparatus constructed in accordance with the present invention for the repairing of armatures.

The present invention in general involves a method for repairing armatures and similar assemblies having a grounded coil condition by connecting a direct current voltage source to the armature in such a way that the positive terminal of the direct current source is connected to the body, shaft or other electrically grounded part of the armature and the negative terminal of the direct current source is applied to at least one of the commutator bars of the armature to produce a current flow at the grounding site of sufliciently high amperage to cause an arcing condition which will burn the grounding material away, and with the voltage held low enough to prevent break down of the dielectric material forming the insulation about the armature windings. This method permits the elimination of the grounding condition by the use of high amperage, low voltage, DC. current applied to the arrnature through the brush and yoke of the apparatus hereinafter described, an are being created at the point of the grounding condition. If the grounding condition has been caused by moistened insulation, the moisture is removed by the heat evolving from the flow of current through the moist insulating material. When the moist material forming the grounding condition becomes dried, the current stops flowing through the insulating material and the ground is removed. In case the grounding conditions are caused by the physical contact between the wire and the base due to removal of the insulating material or be from foreign substance becoming lodged between the base and the wire, the method of the present invention produces an are at the point of grounding which burns away a portion of the base adjacent the point of grounding, thereby eliminating the physical contact 'and creating an air space between the wire and the base.

To facilitate an understanding of the practice and operation of the method of the present invention, a typical armature has been chosen for purposes of illustration, designated generally by the reference character It in FIG- URES 1 and 2, which is of the wire bar winding type having longitudinally or axially extending wire bar receiving grooves 11 in the laminated body 12 of the armature through which rectangular cross-section wire bars 13 imbedded in dielectric insulating material 14 extend. Grounding conditions may result from the moistening of the insulating material 14 by oil, water or other liquid, thereby providing a grounding path through this material, or the grounding may result from direct physical contact between the wire bar 13 and the base or body .12 of the armature or by conductive foreign matter. The armature lit? also includes the usual commutator 15 and armature shaft 16.

Typical grounding conditions which require repair are illustrated in FIGURES l and 2 such as for example a grounding condition resulting from such canting or tilting of the wire bar 13a in its groove which disposes the bar in physical contact with the armature body 12 at the point 17 in FIGURE 2 or by accidental deformation of the Wire bar 13b in the zone of its emergence from its associated groove 11 adjacent the commutator 1'5 providing physical contact with the body 12 of the armature as indicated by the reference character 18 in FIGURE 1. Another example of a typical grounding condition is illustrated in FIGURE -1 wherein foreign matter, indicated by the reference character 19, has become imbedded in the insulating material 14 surrounding the wire bar 130 providing a short circuiting path from the wire bar 13c to the body 12 of the armature.

The typical armature referred to in the following detailed description of the present invention is of the normal automotive armature type which operates with a maximum of 18 volts. By the method of the present invention, the armature is tested with a voltage of 70 volts, which is approximately four times the maximum voltage it will carry in use.

One convenient electrical circuit for practicing the method of the present invention is illustrated in FIGURE 3. The practice of the present method requires a source of direct current electric power. In most cases, a suitable source of DC. electric power is not obtainable directly from the local utility and a conventional A.C.-D.C. converter, for example an arc welder converter having about a 1200 ampere capacity, designated by the reference character 20 is connected to an AC. supply to provide suitable DC. output power. The converter has DC. output leads 21, 22 the voltage across these output leads being regulated by a suitable rheostat 23 intercoupled in series circuit relation with an indicator lamp 24 and manual switch 25 across field control lead wires 26, 27 of the converter 20 whereby the setting of the rheostat 23 will regulate the currents through the field windings of the converter 29 to control the output voltage and current.

The DC. output lead 21 is connected to a suitable contact member to be disposed in electrically conductive contact with the shaft 16 of the test armature lltl, which in this case is a V-shaped copper contact block 23 forming a part of an armature test stand providing an upwardly opening V-shaped recess for receiving the armature shaft 16. The armature test stand also includes a contact brush or brushes 29 engaging the commutator 15 to dispose the brush 29 in electrical communication with the wire bars 13 of the armature 10. The brush 29 is connected by lead 30 through one terminal of an indicator lamp 31, the other terminal of which is connected through lead 32 to a terminal of ammeter 33 which is also connected to the DC output lead 22. The ammeter 33 in this particular embodiment is preferably a 1200 ampere maximum reading ammeter.

A branch circuit is also provided comprising a lead 34 extending from the lead 30 at a point between the brush 29 and indicator lamp 31 to one terminal of an ammeter 35 for example a 75 ampere maximum reading ammeter. The other terminal of the ammeter 35 is connected through lead 36, resistor 37, normally open solenoid contacts 38a and 38b of solenoid 38 and lead 39 to the D.C. output lead 22. The solenoid 38 includes a coil 38c having one terminal connected through lead 40 to lead 39 and the other terminal connected through lead 41, pilot lamp 42, manual switch 43 and lead 44 to the DC. output lead 21, the solenoid coil 38c controlling a plunger 38d which will be projected into bridging contact with the contact members 38a and 38b to complete the circuit therebetween when the solenoid coil 38c is energized.

An additional circuit includes a movable yoke contact member 45 which may be selectively placed in contact with the commutator 15 with the test armature 10 to ap ply high amperage current thereto, the yoke contact member 45 being connected through lead 46 to the second terminal of the ammeter 33 and an indicator light 47 being connected by leads 48, 49 between the lead 46 and the DC. output lead 21.

In the operation of this circuit to test and repair a malfunctioning armature, the AC. electrical supply to the converter 20 is turned on, the switch 25 is closed, and the rheostat 23 is adjusted for a volt output across the converter output leads 21, 22. The pilot lamp 24 will glow to indicate that the current is on. The armature 19 to be tested and repaired is placed on the armature test stand with the shaft 16 in electrical contact with the contact block 28 and the commutator 15 in electrical contact with the brush 29. The DC. output lead 21, which may be assumed to be the positive output lead, will then be in electrical communication with the armature shaft 16 and the armature body 12, while the other DC. output lead 22 is placed in electrical communication with the wire bars 13 through the brush 29 and commutator 15.

If the indicator lamp 31 does not glow but the indicator lamp 47 does glow, these lamp conditions indicate that no grounding condition exists. This is becuase a complete circuit is established from the lead 21, through the lead 48, indicator lamp 47, leads 49 and 46 and ammeter 33 to the other DC. output lead 22, while the branch circuit, paralleling the circuit of lamp 47, which includes lead 32, indicator lamp 31, lead 34 brush 29, armature wire bars 13, armature body 12 and shaft 16, V-contact block 28 and lead 21 is open circuited since there is no grounding path between any of the wire bars 13 and the commutator body 12.

However, if the indicator lamp 31 glows dimly and the indicator lamp 47 does not glow, this lamp condition indictates that it is probable that oil or water-soaked insulation is present creating a grounding condition providing a relatively lower current flow than would occur if a physical contact grounding condition were present. The low level illumination of the indicator lamp 31 in this situation occurs by reason of the fact that the oil or watersoaked insulation completes the electrical circuit portion including the wire bar 13 in contact with the oil or water soaked insulation, brush 29, lead 3G, indicator lamp 31, lead 32 and D.C. output lead 22 with the circuit portion including the armature body 12 and shaft 16, contact block 2? and DC. output lead 21, but the current flow is relatively low due to the appreciable electric resistance properties of water-soaked insulation. Because of the existence of a completed circuit through the indicator lamp 31, the armature 1t) and the contact block 28 as traced above, the indicator lamp 47 does not glow because its circuit, including lead 48, lamp 47, leads 49 and 46 and ammeter 33, is in parallel with the completed circuit of the indicator lamp 31 and is substantially bypassed by the circuit of the indicator lamp 31 so that insufiicient current flows through the indicator lamp 47 to illuminate it.

If the indicator lamp 31 glows dimly and the lamp 47 does not glow, the switch 43 should then be closed, which energizes the solenoid coil 380 to complete the circuit between solenoid contacts. 38a and 38b and place the brush 29 in communication with the negative DC. output lead 22 through leads 3!) and 34, ammeter 35, resistor 37 and the contacts of solenoid 38. If the ammeter 35 registers not more than approximately 50- amperes, the switch 43 should be kept closed until the reading of ammeter 35 drops to zero, the indicator lamp 31 stops glowing, and the indicator lamp 47 begins to glow which conditions indicate the removal of moisture from the insulation and elimination of this grounding condition.

If when the armature It} is placed on the test stand in contact with the brush 29 and contact block 28, the lamp 31 glows brightly, or if the ammeter 35 registers above 50 amperes or registers below 50 amperes but does not drop promptly after the switch 43 has been closed, a physical contact grounding condition is indicated. To correct the physical contact grounding condition, which may, for example, be of the type indicated at 17 or 18 in FIGURES l and 2, the switch 25 should then be opened and the yoke contact 45 should be placed in electrical contact with the armature commutator 15. The switch 25 is then open and the rheostat 23 adjusted to coincide with relative needle-scale position of ammeter 33. Switch 25 is then closed momentarily.

The high amperage current flow thus produced is suflicient to produce an arcing condition at the grounding point, for example the point 17 in FIGURE 2 or the points 18 and 19 in FIGURE 1 which will burn away the grounding foreign matter or the metal immediately adjoining the arcing point, eliminating the physical contact or grounding matter and creating an air space as indicated at 17a, 18a and 19a to restore the armature coil or loops to an isolated condition relative to the armature body.

By this method, the repairing of the grounding condition is accomplished quickly in a matter of seconds as compared with normal methods of repair usually requiring complete rewinding of the armature of the grounded portions thereof.

It will be appreciated that a scale-reading electrical instrument can be substituted in lieu of, or in conjunction with, the indicator lamps '31 and 47.

While but one preferred example of the present invention has been particularly shown and described, it is apparent that various modifications may be made therein within the spirit and scope of the invention, and it is desired, therefore, that only such limitations be placed on the invention as are imposed by the prior art and set forth in the appended claims.

What is claimed is:

1. A method 'for repairing low voltage electrical automotive type armatures and the like having a plurality of coil conductors supported on and normally insulated from a metallic body portion which are defective because of a coil conductor being electrically grounded to the metallic body portion of the armatures comprising applying a direct current voltage of one polarity to the metallic body portion of the apparatus and a direct current voltage of opposite polarity to at least the portion of the conductor adjacent the grounding site producing cur-rent flow of sufficiently high amperage to cause an arcing condition at the grounding site which burns away conductive material providing the grounding path and produces a space insulating the conductor coil from the metallic body portion, said direct current voltage being maintained at a sufliciently low value to prevent breaking down of the insulation between the conductors and the metallic body portion.

2. A method for repairing automotive type armatures having a plurality of coil conductors supported on and normally insulated from a metallic armature body and shaft assembly which is defective because at least one of the conductors is grounded to the body and shaft assembly comprising applying a high amperage direct current voltage of positive polarity to the armature body and shaft assembly and a direct current voltage of negative polarity to at least the conductor which is grounded to the body and shaft assembly to produce a current flow through the grounding path of sufiiciently high amperage to cause an arcing condition which burns away a portion of the armature body grounded to the conductor and produces a space insulating the conductor from the body and shaft assembly, said voltage being maintained at a sufliciently low value to prevent break down of the insulation between the coil conductors and the armature body and shaft assembly.

3. A method for repairing an electrical automotive type armature having a plurality of coil conductors supported on and normally insulated from a metallic body portion of the armature which is defective because of a coil conductor being electrically grounded to the metallic body portion of the armature comprising applying a direct current voltage of positive polarity to the metallic body portion of the armature and a direct current voltage of negative polarity to at least the portion of the conductor coil adjacent the grounding site, producing a sensible indication of the presence or absence of any current flow between the conductor coil and the metallic body portion, interposing an ammeter in series circuit relation between a source of the direct current voltage of one of said polarities and the armature element to which it is applied, and adjusting the direct current voltage to produce current flow of sufiiciently high amperage to cause an arcing condition at the grounding site which burns away conductive material providing the grounding path and produces a space insulating the conductor coil from the metallic body portion while maintaining the direct current voltage at a sufiiciently low value to prevent break down of the insulation between the coil conductors and the metallic body portion.

4. A method for repairing automotive type armatures having a plurality of coil conductors supported on and normally insulated from a metallic armature body and shaft assembly which is defective because at least one of the conductors is grounded to the body and shaft assembly comprising applying a direct current voltage of positive polarity to the armature body and shaft assembly and a direct voltage of negative polarity to at least the conductor which is grounded to the body and shaft assembly, producing a sensible indication of the presence or absence and general intensity level of any current flow between the conductor coil and the metallic body portion, interposing an ammeter in series circuit relation between a source of the direct current voltage of one of said polarities and the armature element to which it is applied, and adjusting the direct current voltage to produce a current flow through the grounding path of sufiiciently high amperage to cause an arcing condition which burns away a portion of the armature body grounded to the conductor and produces a space insulating the conductor from the body and shaft assembly, said voltage being maintained at a suiliciently low value to prevent break down of the insulation between the coil conductors and the armature body and shaft assembly.

5. Apparatus for repairing automotive type armatures having a plurality of coil conductors supported on and normally insulated from a metallic coil supporting body having a defect in the form of a grounding connection between at least one of the conductors and the supporting body comprising a source of direct current voltage, contactor means to be disposed in electrically conductive engagement with the shaft for applying voltage of positive polarity from said source to the shaft and body of said armature, brush means to be disposed in electrically conductive engagement with said conductors for applying voltage of opposite polarity from said source to at least the conductor grounded to said body, sensible indicator means responsive to cunrent fiow from said source through the grounding fault for indicating the presence or absence and general level of current flow, and means for regulating the voltage output of said source to produce a voltage level below values which would damage the insulation between the conductors and said body and a current flow of sufiiciently high amperage through the grounding path to cause an arcing condition which burns away a portion of the conductive material providing a part of the grounding path and produces an air space insulating the conductor from the body.

6. Apparatus for repairing automotive type armatures having a plurality of coil conductors connected to a commutator supported on and normally insulated from a metallic armature body and electrically connected shaft having a defect in the form of a grounding connection between at least one of the conductors and the supporting body comprising brush means to be disposed in electrically conductive engagement with said commutator, a contactor member to be disposed in electrically conductive relation with said shaft, a source of direct current voltage having positive and negative output leads, means for applying voltage of positive polarity from said positive output lead to said contactor member and thereby to the shaft and body of said armature, means for applying voltage of negative polanity from said negative output lead to the brush means to place said negative lead in electrical ,2, communication with the conductor grounded to said body, indicator lamp means intercoupled between said brush means and said negative output lead responsive to current flow through the grounding fault to produce a sensible indication of the presence or absence and general level of current flow, a branch circuit in parallel circuit relation with said indicator lamp means including an amineter and switch means for establishing a circuit between said brush means and said negative output lead, and @3115 for regulating the voltage output of said source to produce a current fiow of sufficiently high amperage through the grounding path to cause an arcing condition which burns away a portion of the conductive material providing a part of the grounding path and produces an air space insulating the conductor from the body, and not high enough voltage to damage dielectric.

References Cited in the file of this patent UNITED STATES PATENTS 2,494,029 Bertalan et al lan. 10, 1950 2,501,481 Taggart Mar. 21, 1950 2,501,482 Boynton et a1. Mar. 21, 1950 2,777,842 Legg Ian. 8, 1957 2,865,083 Kater et al. Dec. 23, 1958

Claims (1)

1. 5. APPARATUS FOR REPAIRING AUTOMOTIVE TYPE ARMATURES HAVING A PLURALITY OF COIL CONDUCTORS SUPPORTED ON AND NORMALLY INSULATED FROM A METALLIC COIL SUPPORTING BODY HAVING A DEFECT IN THE FORM OF A GROUNDING CONNECTION BETWEEN AT LEAST ONE OF THE CONDUCTORS AND THE SUPPORTING BODY COMPRISING A SOURCE OF DIRECT CURRENT VOLTAGE, CONTACTOR MEANS TO BE DISPOSED IN ELECTRICALLY CONDUCTIVE ENGAGEMENT WITH THE SHAFT FOR APPLYING VOLTAGE OF POSITIVE POLARITY FROM SAID SOURCE TO THE SHAFT AND BODY OF SAID ARMATURE, BRUSH MEANS TO BE DISPOSED IN ELECTRICALLY CONDUCTIVE ENGAGEMENT WITH SAID CONDUCTORS FOR APPLYING VOLTAGE OF OPPOSITE POLARITY FROM SAID SOURCE TO AT LEAST THE CONDUCTOR GROUNDED TO SAID BODY, SENSIBLE INDICATOR MEANS RESPONSIVE TO CURRENT FLOW FROM SAID SOURCE THROUGH THE GROUNDING FAULT FOR INDICATING THE PRESENCE OR ABSENCE AND GENERAL LEVEL OF CURRENT FLOW, AND MEANS FOR REGULATING THE VOLTAGE OUTPUT OF SAID SOURCE TO PRODUCE A VOLTAGE LEVEL BELOW VALUES WHICH WOULD DAMAGE THE INSULATION BETWEEN THE CONDUCTORS AND SAID BODY AND A CURRENT FLOW OF SUFFICIENTLY HIGH AMPERAGE THROUGH THE GROUNDING PATH TO CAUSE AN ARCING CONDITION WHICH BURNS AWAY A PORTION OF THE CONDUCTIVE MATERIAL PROVIDING A PART OF THE GROUNDING PATH AND PRODUCES AN AIR SPACE INSULATING THE CONDUCTOR FROM THE BODY.

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