US2176361A

US2176361A - Radial commutator

Info

Publication number: US2176361A
Application number: US137031A
Authority: US
Inventors: Scruggs Loyd
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-04-15
Filing date: 1937-04-15
Publication date: 1939-10-17
Anticipated expiration: 1956-10-17

Description

Oct. 17, 1939. L. SCRUGGS 2,176,361

RADIAL COMMUTATOR Filed April 15, 1957 FIGZ.

ar I an! y A TTORNE Y /WXM Patented Oct. 17, 1939 UNITED STATES PATENT OFFICE Claims.

This invention relates to commutators or small, fractional horsepower electric motors.

One object of my invention is to provide a commutator of the radial type that can be manufac- 5 tured easily and at a low cost.

Another object is to provide a radial commutator for small electric motors, which is of such design that there is no possibility of electric current acting upon the plastic insulating material 1;) of which the body part of the commutator is constructed, in such a manner as to cause said plastic insulating material to char and thus permit the current to short circuit or are across the segments of the commutator.

And still another object of my invention is to provide a commutator of the type and kind above referred to, which is of such design that it is unnecessary to wrap a binding element around the portions of the armature wire that extend between the armature and the commutator as is now the practice, in order to prevent said wires from being thrown outwardly or radially by centrifugal force in the event said wires are baggy or in a sagging condition.

Figure 1 of the drawing is a top plan view of the metal stamping that is used to form the brush-contacting portions or metal segments. of my improved radial commutator.

Figure 2 is an edge view of said stamping after the terminal portions of the radially disposed arms of same have been deformed. I

Figure 3 is a plan view of the mica membe that is used to prevent the Bakelite or similar plastic material from charring.

Figure 4 is a vertical transverse sectional view of the stamping after the radially disposed parts at the inner and outer edges of the annular portion of same have been bent upwardly so as to permit the mica member to be preliminarily positioned upon said stamping in the operation of combining the mica member with the stamping.

Figure 5 is a vertical transverse sectional view of said stamping after it has been bent so as to interlock the mica member with same and impart the final shape to said stamping.

Figure 6 is a vertical transverse sectional View illustrating the metal stamping combined with the plastic material which constitutes the body part of the commutator.

Figure '7 is a side elevational view of the device shown in Figure 6.

Figure 8 is a vertical transverse sectional view of the device shown in Figure 6 after the annular portion of the stamping has been severed o to divide said annular portion into segments or brush-contacting portions that are separated from each other by gaps or slots.

Figure 9 is a side elevational view of the device shown in Figure 8.

Figure 10 is an enlarged end View of the com- 5 plete or finished commutator showing the brushcontacting portions of same in front elevation; and

Figure 11 is an enlarged sectional view of the commutator showing it mounted on the armature 10 shaft in assembled relationship with the armature.

My improved commutator is of the radial type and is adapted to be mounted on an armature shaft A with the brush-contacting portions or 15 segments B of the commutator projecting radially from the armature shaft and disposed at right angles to same as shown in Figure 11, said commutator being composed of or made up of three parts, to-wit, a metal stamping preferably of 20 copper, a cylindrical body part made of Bakelite or some other suitable plastic insulating material that can be molded, and a piece of mica interposed between the metal stamping and the Bakelite and constructed and arranged so that it ef- 25 fectively protects all portions of the Bakelite and prevents the electric current from short circuiting across the gaps a: between the segments or brush-contacting portions B of the commutator,

at any portion throughout the entire length of 30 said gaps.

The metal stamping previously referred to is formed from a flat sheet of copper or other suitable metal and comprises an annular portion I provided at its outer edge without outwardly pro- 5 jecting radially disposed arms 2, and provided at its inner edge with inwardly projecting radially disposed lugs 3 as shown in Figure 1. After being blanked out or cut from a flat sheet, said stamping is subjected to a deforming operation 40 so as to cause lugs 2a on the terminal portions of the arms 2 to be bent into ofi-set or angular relationship with said arms to form retaining devices which assist in securely anchoring the stamping to the Bakelite body part of the com- 45 mutator. After the terminal portions of the arms 2 have been ofi-set or deformed as above described, the stamping is subjected to another deforming operation wherein the outwardly projecting arms 2 are bent into an upwardly and 50 outwardly inclined position with relation to the annular portion l of the stamping, and the inwardly projecting lugs 3 are bent upwardly into a position at right angles to the annular portion I as shown in Figure 4, thereby producing a substantially annular-shaped device provided at its outer edge with upwardly flared portions 2 and provided at its inner edge with right angularly disposed portions 3.

The next step in the operation of manufacturing the commutator consists in assembling a piece of mica with the deformed stamping shown in Figure 4. The piece of mica that I prefer to use for this purpose consists of a fiat member C of substantially annular form in general outline, provided at its inner edge with notches 4 and provided at its outer edge with notches 5, as shown in Figure 3, said member C being preferably cut from a piece of sheet mica by a die or cutter of the exact shape or outline of the member C. After the mica member C has been superimposed upon the annular portion I of the deformed stamping shown in Figure 4 and arranged so that the upwardly projecting lugs 3 on said stamping are positioned in the notches 4 of the member C and the flared arms 2 of the stamping are disposed oppositely to the notches 5 in the outer edge of the mica member, the stamping is subjected to another deforming operation so as to bend inwardly the flared arms 2 and cause said arms to be positioned in the notches 5 and disposed at right angles to the annular portion of the stamping as shown in Figure 5.

Thereafter, the metal stamping with the mica member C interlocked with same, is placed in a mold or die into which a plastic insulating material is introduced so as to form a cylindrical body part D providing with a hole 6 for the armature shaft and having securely anchored to one end of same a metal part which comprises an annular portion I provided at its peripheral edge with a plurality of integrally right angularly disposed spaced arms 2 embedded in said body part and having their outer edges extending flush with the peripheral edge or surface of said body part. The terminal ends of the arms 2 are anchored to the body part by the deformed lugs 2a which efrectively prevent the terminal ends of said arms 2 from springing outwardly, and the mica member C constitutes an effective protecting element that is interposed between the insulating material of the body part D and the annular metal portion I. By referring to Figure 11, it will be noted that the diameter of the mica member C is the same as the diameter of the annular portion I, and is also the same as the external diameter of the body part D, thus insuring that the entire area of the segments or brush-contacting portions B of the commutator will be backed up and separated from the plastic insulating material D by a material which has great insulating properties, to-wit, the mica member C. Subsequently, saw cuts are formed in the annular portion of the metal stamping so as to divide said annular portions into a plurality of segments or brush-contacting portions B that are separated from each other by gaps or slots at as shown in Figures 8, 9 and 10. In producing the slots or gaps a: just referred to it is essential that the saw cuts extend clear through the annular portion I of the metal stamping without, however, completely severing the mica member C or cutting into said mica member to such an extent that the continuity of said member is destroyed, because it is absolutely essential that a continuous or uninterrupted ring of mica be disposed between the body part D of the commutator and the annular portion of the metal stamping that constitutes the brush-contacting portions B, in order that the gaps or slots at between said brush-contacting portions will be closed at their inner ends and cut off or separated from the plastic insulating material of which the body part D is formed, due to the fact that the function performed by the mica member C is to protect the body part D from the electric current and prevent said body part from charring at, or adjacent to the gaps a: between the segments B and thus permitting the current to arc across said segments. In the sawing operation above referred to, it is immaterial if the saw cuts extend into the mica member C a slight distance for it is almost impossible to saw completely through the annular portion l of the metal stamping without slightly scoring the mica member C. The important things are, 1st, that said mica member be not completely severed in the operation of dividing the annular portion l of the metal stamping into segments, and 2nd, that the mica member protect the entire end face of the body part D and comprise parts which extend over those portions of the end face of said body part which lie between the arms 2 that are embedded in the peripheral edge of the body part D in flush relationship with the circular outer surface of said body part. Therefore, I use a relatively thick mica member C of the same diameter as the end face of the body part D, and form notches 4 and 5 in the inner and outer edges of said mica member, as previously explained.

The integral arms 2 on the brush-contacting portions B of the commutator are used to form extensions on said brush-contacting portions to which the armature wires can be conveniently attached, the terminal portions of said armature wires, designated by the reference character w in Figure 11, being positioned in grooves 1 (see Figures 9, l0 and 11) formed in the outer surface of the arms 2, and secured in position in same by soldering or in any other suitable way. In order to reduce the tendency of the terminal portions w of the armature wires to be thrown out of the grooves l by centrifugal force when the motor is in operation, said grooves are preferably under-cut in such a way that centrifugal force tends to make the terminal portions of the armature wires cling tightly to the overhanging walls of the grooves 1 in the arms 2.

As shown in Figures 6, 8 and 11, the body part D of the commutator is provided at its inner end or side with a recess or depression for receiving the windings y of the armature E, thereby making it practicable to use short sections 20 of wire between the armature and the commutator and also providing a bridge piece 8 on the body part D of the commutator that can be used to support and hold the portionswof the armature wires extending between the armature and the arms 2 on the commutator. The bridge piece 8 is formed by a flange or enlarged portion at the inner end of the body part D of the commutator and openended slots 1a are formed in said flange 8 as shown in Figures 9, 10 and 11 to receive the armature wires to. The slots la, similarly to the grooves 1 in the arms 2, are under-cut slightly (see Figure 10) in such a direction that centrifugal force tends to cause the armature wires w to be held in engagement with an overhanging portion on the body part of the armature that effectively prevents said wires from flexing or swinging outwardly in the event they are baggy or in a sagging condition. In small electric motors of conventional construction, the commutator is spaced a considerable distance away 7 from the armature and after the armature wires have been attached-to the commutator a binding element is wrapped around the'portions of the armature wires extending between the armature and the commutator so as to prevent said wires from being thrown outwardly by centrifugal force when the motor is in operation. With my improved commutator it is unnecessary to wrap a binding element around the sections of the armature wires that lie between the armature and the arms 2 on the commutator, due to the fact that the bridge piece 8 on the body part D in which the armature wires are positioned is constructed so as to effectively hold the armature wires against outward flexing or radial movement, produced by centrifugal force. Another desirable feature of such a structure is that it permits the use of very short sections of wire between the armature and the commutator due, of course, to the fact that the inner end of the body part D of the commutator is recessed so as to receive the armature windings y and thus permit the commutator to be arranged in close relationship to the armature.

A radial commutator of the construction above described can be manufactured easily and at a low cost and it has the added advantages of eliminating the possibility of arcing across the segments; permitting the use of short sections of wire between the armature and commutator; and providing an efficient holding and supporting means for the armature wires adjacent to the point where said wires are attached to the commutator.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A commutator for fractional horsepower electric motors, provided with a cylindrical body part formed of insulating material that can be molded, radially disposed, metal brush-contacting portions on one end face of said body part separated from each other by gaps and arranged at right angles to the armature shaft, angularly disposed extensions on said brush-contacting portions, embedded in and extending flush with the peripheral surface of said body part, and a mica member of the same diameter as said body part, interposed between the same and said brush-contacting portions to form closures for the inner ends of said gaps, that extend throughout the entire length of said gaps.

2. A commutator for fractional horsepower electric motors, provided with a cylindrical body part formed of insulating material that can be molded, radially disposed, metal brush-contacting portions on one end face of said body part separated from each other by gaps and arranged at right angles to the armature shaft, right angularly disposed, integral extensions on said brush-contacting portions embedded in the peripheral edge of said body part, and a mica member interposed between said body part and said brush-contacting portions to form closures for the inner ends of said gaps, said mica member having a diameter at least equal to that of said body part, and being provided in its peripheral edge with notches that receive the extensions on said brush-contacting portions.

3. A commutator for fractional horsepower electric motors, provided with a cylindrical body part formed of insulating material that can be molded, segmental-shaped brush-contacting portions on one end face of said body part separated from each other by gaps and arranged at an angle to the armature shaft, a mica member of substantially annular form in general outline arranged between said segmental-shaped brushcontacting portions and said body part and positioned so as to form closures for said gaps that extend throughout the entire length of said gaps, and integral angularly disposed extensions on said brush-contacting portions, positioned in notches in the peripheral edge of said mica member and imbedded in the peripheral surface of said body part.

4. A commutator for fractional horsepower electric motors, provided with a cylindrical body part formed of insulating material that can be molded, segmental-shaped brush-contacting portions on one end face of said body part separated from each other by gaps and arranged at an angle to the armature shaft, a substantially annular shaped mica member of the same diameter as said body part, arranged between said segmental-shaped brush-contacting portions and said body part and positioned so as to form closures for said gaps that extend throughout the entire length of said gaps, and integral angularly disposed arms at the outer ends of said brush-contacting portions to which the armature Wires are adapted to be attached, said arms being positioned in notches in the outer edge of said mica member and being provided at their terminal ends with retaining devices which are embedded in the peripheral edge of said body part.

5. A commutator for fractional horsepower electric motors, provided with a cylindrical body part formed of insulating material that can be molded, segmental-shaped brush-contacting portions on one end face of said body part separated from each other by gaps and disposed in radial relationship with the armature shaft, laterally projecting integral extensions at the inner and outer ends of said brush-contacting portions imbedded in the material of which said body part is made, and a substantially annular shaped mica member interposed between said brush-contact ing portions and said body part and provided at its inner and outer edges with notches in which said extensions are positioned, said mica member having a diameter at least equal tothe diameter of said body part.

6. In a fractional horsepower electric motor, the combination of an armature, a commutator provided with a body part, segmental-shaped, radially disposed, brush-contacting portions on said body part separated from each other by gaps, and integral extensions on the outer ends of said brush-contacting portions provided with undercut grooves in which the armature wires are positioned.

7. In a fractional horsepower electric motor, the combination of an armature, a commutator provided with a body part, segmental-shaped, radially disposed, brush-contacting portions on said body part separated from each other by gaps, integral extensions on the outer ends of said brush-contacting portions provided with undercut grooves in which the armature wires are positioned, and an integral portion on said body part constructed so as toprevent excessive radial movement of the sections of the armature wires extending between the armature and the commutator.

8. In a' fractional horsepower electric motor the combination of an armature, a commutator having a body part of insulating material provided at one end with a recess or depression for receiving the windings of the armature, radially disposed segmental-shaped brush-contacting portions of metal on said body part separated from each other by gaps and provided at their outer ends with extensions to which the armature wires are attached, and a bridge piece on said body part which receives and holds against excessive radial movement the sections of the armature wires extending between the armature and commutator.

9. In a fractional horsepower electric motor, the combination of an armature, a commutator having a body part of insulating material provided at one end with a recess or depression for receiving the windings of the armature, radially disposed segmental-shaped brush-contacting portions of metal on said body part separated from each other by gaps and provided at their outer ends with extensions to which the armature Wires are attached, and an integral flange at the inner end of said body part provided with under-cut slots for receiving the portions of the armature wires extending between the armature and the extensions on the brush-contacting portions to which said wires are attached.

10. A commutator for fractional horsepower electric motors, provided with a body part of insulating material that can be molded, radially disposed, segmental-shaped, metal brush-contacting portions on said body part separated from each other by gaps and disposed at right angles to the armature shaft, laterally projecting integral arms on the outer ends of said brushcontacting portions to which extensions of the armature wires are attached, a mica member that separates said brush-contacting portions from said body part and forms closures for the inner ends of the gaps between said brush-contacting portions, and a slotted bridge piece at the inner end of said body part that receives the armature wire extensions.

LOYD SCRUGGS.